Investigating the Impact of Solar Highways on Driver's Safety And

Investigating the Impact of Solar Highways on Driver’s Safety and Road Maintenance

Navaneeth K. Ramesh

Thesis

Submitted to the

Department of Engineering

Colorado State University – Pueblo

In partial fulfillment of the requirements

for the degree of

Master of Science

Completed on 1st April, 2014

Abstract

Navaneeth K. Ramesh for the degree of Master of Science in Industrial and Systems Engineering presented on 1st April, 2014. Investigating the Impact of Solar Highways on Driver’s Safety and Road Maintenance

Abstract approved: ______

Ananda Paudel, Ph.D.

Effective utilization of vacant areas across highways could produce a significant amount of electricity from photovoltaic systems. The space available in the highway right-of-way (ROW) provides an opportunity for the solar PV system deployment. However, this is only feasible if it can be done in a manner that does not interfere with the operation and maintenance of the highway and does not create an unacceptable risk to the user. Potential impacts those are associated with solar highway that should not compromise risk of safety of the travelling people, road management crew and road management. There is a need on impact studies for Departments of Transportation (DOT) for considering ROW use for solar energy generation using ground mounted solar array systems.

The objective of this thesis is to perform an impact analysis through case studies and identify the hazards. An evaluation matrix is developed based on several findings from literature, experimentation, site visits and personnel communication.

The outcome in this study will facilitate PV deployment related decision process along with relevant mitigation strategies. In a broad scale, this will help to protect the general public and environment while generating power from systems as well as maintaining efficient ROW operations.

Certificate of Acceptance

This thesis, being presented in partial fulfillment of the requirements for the degree of

Master of Science has been accepted by the Program of Industrial and Systems Engineering, Colorado State University – Pueblo.

APPROVED

Dr. Ananda Paudel Assistant Professor and Committee Chair

Dr. Leonardo Bedoya-Valencia Assistant Professor and Committee Member

Dr. Jerry Purswell Adjunct Faculty and Committee Member

Master‘s Candidate: Navaneeth K. Ramesh Date of Thesis Presentation: 1st April, 2014

iii

Acknowledgements

This thesis would not have been possible without the guidance and the help of several individuals who, in one way or another, contributed and extended their valuable assistance in the preparation and completion of this study.

First and foremost, I offer my utmost gratitude to my academic advisor and committee chair, Dr. Ananda Paudel, who introduced me to this topic and encouraged me to write this thesis. I appreciate his support throughout its development with his knowledge and patience. Without him, I would have been unable to put pen to paper and see this through to its conclusion. One simply could not wish for a better or friendlier advisor.

I am very grateful to Dr. Leonardo Bedoya-Valencia and Dr. Jerry Purswell for their help, support, and expertise throughout this study. Their participation on the committee is greatly appreciated.

I am indebted to Mr. Art Hirsch of Terra Logic Sustainable Solutions for allowing the opportunity to work on this topic and providing the means to perform the research necessary for its successful completion.

I wish to thank all the members of Sandia Laboratories for providing me access to the SGHAT software even before its commercial release. I also wish to thank Dr. Tabler, for providing me access to his research papers on his snow drifting study.

I would also like to acknowledge and thank all the members of CDOT involved in this project for giving me their valuable time, feedback and support of this thesis.

I would also like to thank my dearest friends and my flat mates. Their unwavering support and encouraging words were a constant inspiration and a welcomed perspective at the most trying of times.

Finally, I would like to thank my dearest parents and my brother for supporting me throughout all my studies. Without their motivational support, the completion of this degree would not have been possible. I dedicate this work to them.

Abbreviations AASHTO American Association of State Highway and Transportation Officials Caltrans California Department of Transportation CBM Condition-based maintenance CDOT Colorado Department of Transportation CDPHE Colorado Department of Public Health and Environment CEQA California Environmental Quality Act CFR Code of Federal Regulations CPV Concentrated Photo Voltaic DNI Direct Normal Irradiance DOE The Department of Energy DOT Department of Transportation EPC Engineering-Procurement & Construction FHWA Federal Highway Administration FMEA Failure Mode and Effects Analysis kW Kilo Watts kWh Kilo Watt hours MassDOT Massachusetts Department of Transportation MUTCD Manual on Uniform Traffic Control Devices MW Mega Watts NREL National Renewable Energy Laboratory NW Parkway Northwest Parkway O&M Operations & Maintenance Ohio DOT Ohio Department of Transportation OSHA Occupational Safety and Health Administration PM Preventative maintenance PV Systems Photo Voltaic Systems R&D Research & Development REI Renewable Energy Installations ROW Right of Way RSDG Roadside Design Guide SAI Solar America Initiative SH-ROW State Highway Right of Way SMUD Sacramento Municipal Utility Districts University Colorado State University-Pueblo VGCS Veteran‘s Glass City Skyway WQCD Water Quality Control Division

Table of Contents

Abstract ...... ii

Acknowledgements ...... iv

Abbreviations ...... v

List of Figures: ...... vii

List of Tables ...... vii

Thesis Outline ...... ix

Chapter 1 – Introduction ...... 1

Chapter 2 - Literature Review ...... 5

Chapter 3 – Objective ...... 40

Chapter 4 –Methodology ...... 41

Chapter 5 – Results ...... 63

Chapter 6 – Conclusions & Recommendations ...... 68

Future Research: ...... 70

REFERENCES: ...... 71

APPENDICES ...... 76

List of Figures:

Figure 1. Solar PV system along highway E-470, Denver, CO ...... 2 Figure 2. Stake holder's relationship chart for Solar Highways ...... 4 Figure 3. Components of a solar PV system ...... 6 Figure 4. Solar Highway at Oregon by ODOT ...... 10 Figure 5. Aerial view of the solar highway project by Ohio DOT ...... 11 Figure 6. Snow fences implemented in the State of Wyoming ...... 18 Figure 7. Snow fence recommendation by Tabler ...... 19 Figure 8. Ocular Hazard Plot ...... 26 Figure 9. Illustration of road signage on solar glare displayed at Massachusetts ...... 29 Figure 10. Aerial view of the solar PV system at Colorado State University – Pueblo ...... 30 Figure 11. Key observation points considered for evaluation ...... 31 Figure 12. SGHAT analysis sample for Colorado State University – Pueblo ...... 33 Figure 13. Proposed risk analysis model for research evaluation ...... 37 Figure 14. Project development outline for research assessment ...... 41 Figure 15. Solar PV system installed at North West Parkway, Colorado...... 43 Figure 16. Solar PV system installed at the Denver Federal Center, Colorado ...... 43 Figure 17. Solar PV system installed at the DIA, Colorado ...... 43 Figure 18. List of major highways in Colorado with available ROW space and isolation level . 46 Figure 19. Identified locations along the highways of Colorado ...... 47 Figure 20. Aerial view of the proposed site at MP-358, Elbert, CO...... 53 Figure 21. Proposed site at MP-358, Elbert, CO ...... 53 Figure 22. Highway I-70 alignment at proposed site near MP-358, Elbert, CO ...... 53 Figure 23. Sketch layout of the proposed solar highway at Elbert, CO ...... 54 Figure 24. Key observation points taken for evaluation at Elbert, CO ...... 55 Figure 25. SGHAT analysis sample for proposed site at Elbert, CO ...... 57 Figure 26. Time history of the glare analysis at proposed site near MP-358, Elbert, CO ...... 59 Figure 27. Four square method risk quadrant ...... 62 Figure 28. Process control chart with life cycle stages for setting up Solar PV systems in ROW‘s along Highways ...... 64

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List of Tables

Table 1: Summary of Solar Highways implemented worldwide ...... 13 Table 2: Summary of O&M activities with typical frequencies ...... 14 Table 3: Albedo Chart for Material Reflectivity of common reflective surfaces ...... 22 Table 4: Technical details of the solar PV system at the Colorado State University – Pueblo .... 31 Table 5: Latitude & Longitude coordinates at Colorado State University – Pueblo ...... 32 Table 6: SGHAT Results for Glare analysis at the Colorado State University – Pueblo ...... 34 Table 7: Field visit summary ...... 42 Table 8: Latitude & Longitude coordinates for the potential sites identified along Colorado Highways ...... 47 Table 9: Summary of the qualitative method approach with factors considered for evaluation .. 49 Table 10: Monthly break up of average solar radiation at proposed site ...... 51 Table 11: Technical assumptions at the proposed site at Elbert, CO ...... 52 Table 12: Observation points with distance and direction of orientation at Elbert, CO ...... 56 Table 13: Latitude & Longitude coordinates of the PV Array1 at Elbert, CO ...... 56 Table 14: Latitude & Longitude coordinates of the PV Array2 at Elbert, CO ...... 57 Table 15: SGHAT Results for Glare analysis at Elbert, CO for PV Array 1 ...... 58 Table 16: SGHAT Results for Glare analysis at Elbert, CO for PV Array 2 ...... 58 Table 17: Impact matrix with risk factors and the probability of occurrence ...... 65 Table 18: References used in recommending the mitigation and siting criteria ...... 66 Table 19: Impact matrix with mitigation measures and siting criteria ...... 67

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Thesis Outline

Chapter 1 Introduction This chapter covers the basic introduction to Solar Highways including major concerns and potential impacts associated with the placement of solar array systems within the Colorado Department of Transportation‘s Right of Way. The author describes in brief about the Solar Highway benefits, the stake holder‘s relationship for this project and the solar resource potential available in the Colorado highways along the ROW. Chapter 2 Literature Review Literature Assessment of several topics is covered in this section. The author gives an insight of all the current and existing research performed on topics such as glare and its potentials impacts, Solar PV Operation and Maintenance challenges, Highway Operation & Maintenance challenges, snow drifting and case studies performed in assessment of other proposed solar highway projects by other Departments of Transportation. Chapter 3 Objectives The author sets froth the key objectives that will be established through this thesis. The objective directive is defined by the experimentation performed to analyze the results. Chapter 4 Methodology This chapter covers the methodology and experimentation for the project. The contents will include the key findings and results from the Literature assessment, perform glare analysis using the SGHAT software for various locations identified, set up a score matrix for site selection using a qualitative approach, identify the site radiation, perform the glare analysis for the selected site and finally assess the impact of the glare analysis through a risk evaluation model. Chapter 5 Results The summary outlines the key results/findings and also establishes an impact matrix to identify the impact parameters, the potential impacts, the risk factor, the mitigation and the design criteria recommended to counter the problem. Chapter 6 Conclusion & Recommendation This chapter makes the recommendations and conclusions that would help address the concerns and potential impacts associated with the placement of solar array systems within the right of way by summarizing the research findings in collaboration with the interviews with CDOT officials and the site surveys performed. Suggestions for future research to address the potential impacts associated with the placement of solar array systems are also discussed.

Chapter 1 – Introduction

Introduction: For many years state Department of Transportation‘s (DOT‘s) have used solar PV technology on a small scale range on highway applications such as portable message signs and traffic signals. More recently, state DOTs have turned their attention towards medium scale deployment of solar PV. While many of these installations have been on the rooftops of agency facilities, a number of DOTs have now considered and installed Solar Photo Voltaic (PV) systems in the highway Right of Way (ROW). The concept of this thesis stems from the need to provide clarity to all state DOTs to evaluate the potential impacts associated with developing Solar PV systems along Highways by identifying critical impacts and recommending potential mitigation considerations.

The evaluation and the analysis performed in this thesis uses the study of highways in the state of Colorado and the general operating principles on highway and utility maintenance set forth by the Colorado Department of Transportation (CDOT).

This research study will address the DOT‘s major concerns and potential impacts associated with the placement of solar array systems within the right of way with concentration on safety and operation & maintenance activities. These potential impacts that are associated with solar highway safety are safety of the travelling public, right of way management, snow drifting and highway maintenance.

Glare for drivers and snow drifting are some of the potential impacts identified in this research work. Considering the fact that the ROW is recognized as a potential area for alternative energy, the goals and objective of this research study would be to provide different case studies with potential hazards as identifiers for which validation, subsequent assessment, and citations will be performed through an evaluation matrix. The assessment of the evaluation matrix is based on several key findings from the literature studies, design of experiments for glare effects, site visits, interviews and meeting with key official personnel in the field of solar operations & maintenance.

The research outcome in this study will facilitate PV deployment related decision process along with relevant mitigation strategies. This will help to protect the general public and environment while generating power from PV systems as wells as maintaining efficient ROW operations.

Background Information Solar Highways refers to highways with solar PV systems deployed along the ROW. As adequate land is available, it can be considered a resourceful potential to generate electricity and effectively utilize the vacant areas along highways. This effective utilization has been adopted by various agencies and several solar highways have been developed throughout the world. Development of solar highways also provides an offset to carbon footprint emissions and generates financial resources through long term lease agreements.

The potential safety, environmental and highway operation and maintenance impacts of solar panel array installation along the ROW were researched and evaluated. To study the potential impacts for user safety and maintenance operations, the current ROW physical characteristics and operational conditions to various PV design criteria variables and criteria have been identified and evaluated. A typical view of a solar PV system placed along the highway is shown in Figure 1.

Figure 1. Solar PV system along highway E-470, Denver, CO

Solar Highway benefits

Promising ROI‘s through solar highways can be considered as a smart , safe investment and an effective renewable energy project investment, where they can be mapped to the different elements of the electricity system value chain.

As solar highways fall within the generation category, the solar power will be sent directly to the local electric grid and the utility that purchases the power would receive the Renewable Energy Credits (REC). The generated electrical energy can be used for various applications, such as road lighting, traffic systems. In time, electric cars might possibly be able to make use of the energy. The energy will then actually be generated at the place where it is needed which will provide a big step towards an energy-neutral mobility system.

Typical spaces available for solar energy generation are rest areas, land outside clear zones, space adjacent to interchange and building roof tops. Based on the space available and their characteristics photovoltaic (PV) arrays with varying ranges of design and orientation and capacity could be installed in DOT‘s property.

From the concept to deployment stage, the PV development involves several agencies holding key responsibilities and each of them play a vital role towards solar highway development. As many as eight different agencies hold several roles and responsibilities in setting up and running the project. The DOT/moderator owning the ROW land will be responsible to coordinate with the service utility company and the solar service provider. The Solar service provider is responsible for coordinating the finance, design and construction of the PV system at the host‘s site. Other agencies in the stake holder‘s relationship include equipment manufacturer, solar PV system installer, investor, incentive provider and the consultancy service company. The tentative stake holder‘s relations chart for the solar highway project is provided in the Figure 2.

Stake Holder’s Relationship of Solar Highway Project

Customer Equipment Manufacturer Supplying solar Panels and the inverters Receive revenue from the sale of

Utility Company system components Provide equipment warranties. Providing electricity Installer Integrate PV to the grid Equipment Equipment Installation Warranties Sales & Maintain Operated by the Solar Service Provides net metering credit Service Provider Install solar Panels Excess PV Regular kWh kWh output Service Solar Service Provider Provide Maintenance Servicing A “Turnkey” Solar energy Engineering/Procure/Construct Moderator - DOT PPA Tenure O&M “EPC” Consortium Revenue • Receive power from site Coordinates financing, design Investor Purchase RECs and construction of PV systems Receive low risk ROI from sales of Provide installation at Moderator’s site electricity and state and federal space and service access Revenue from Electricity Sales incentives. for PV system Financing Receive tax returns from the tax

return program Provide capital investment. Return on Investment Apply for the tax Contributes financing towards Incentive Provider – credit & Grant construction and operation. Department of Energy & Federal Government Providing Consulting Service Receive the Grant

Receive the Tax Credit Consulting Structure the financing for the Figure 2. Stake holder's relationship chart for Solar Highways federal and state tax credit for the investor. 4

Chapter 2 - Literature Review

As impact studies are the major focus of this research, detailed literature review to assess existing studies that have been undertaken to impacts associated with solar highways and PV deployment. In addition, national and international projects experiences that correlate with motorists‘ safety and ROW operations and maintenance are researched. The potential topics identified in the literature assessment are as follows:

The working principle and background of solar array system Administrative controls over ROW management Exploring existing solar highways implemented within the US and the rest of the world Glare from solar panels Current practices and soft wares used to analyze sun glare vision impairment hazards Operations and Maintenance activities associated with PV deployment Operations and Maintenance activities associated with high way management Safety during solar array maintenance Snow drifting and deposition

In addition to the literature review, several interviews with key personnel from the industry as well as site visits to existing solar array systems along highways were. The impact-related data and mitigation approaches are the key inputs to model the framework development.

Solar Array System

The solar PV system uses solar cells that are made up of layers of semiconducting materials that absorb sunlight enabling electrons to flow through the material to produce electricity. Individual solar cells are combined together to form solar modules which are in turn assembled into PV array systems. For mass scale applications several array systems are interconnected to form a single large system. The equipment required for PV facilities can be tolerant to slope change based on site topographical conditions and can be engineered to accommodate slope change across a site. There are usually security link fences that surround the solar array system in the clear zone area to provide security against vandalism and theft. The typical solar PV array system with its components is given in Figure 3.

Figure 3. Components of a solar PV system (Adapted from: mapawatt.com, 2009)

With reference to Figure 3, all PV systems irrespective to being the flat plate or the concentrating power technology would require the panels to be maintained and cleaned well in order to achieve the best efficiency from the system and will require standard equipment‘s such as the inverters and transformers (mapawatt, 2009). The inverters are used to change the direct current load to alternating current that is used in the transmission grid and the transformers are used to either step up or step down the voltages to a relative voltage collection system suitable for transmission. When the tilted module rows are too crowded and placed close to each other, winter production will suffer as the rows in the front will shade the rows behind for a greater duration of the day. The required distance to avoid this is called the minimum inter row spacing. As a result, ground-mounted systems should be optimally-aligned with respect to both their southern orientation and their tilt angle.

ROW Management baseline conditions

The State Highway Utility Accommodation Code serves the public good through the safe, efficient and effective joint utilization of State Highway Right-of-Way (SH ROW) for both transportation and utility purposes. The code guides the DOTs, utility owners and local agencies in the planning and administration of utility accommodations within the SH ROW (CDOT, 2009). The means of reasonable regulations will ensure that such accommodations do not adversely affect the highway or traffic safety, or otherwise impair the operation, aesthetic quality or maintenance of the transportation facility, or conflict with applicable law.

Several DOT‘s, FHWA and research institutions have been investigating and implementing PV array systems to be built in sustainable environmental values in their infrastructure based on utility economics. This section highlights key existing baseline conditions and standards that need to be followed to accommodate energy utilization within the highway ROW.

Federal Regulations and Standards The deployment of the PV system along the highway ROW is a recent development and needs to abide by the standards for accommodating utilities on the ROW. The following includes the Federal regulations and standards that should be followed while accommodating utilities in the State Right of Way (as defined in 23 CFR 645.207.):

a) ―Rights of Way,‖ [Title 23 - Highways] 23 CFR 1.23, April 1, 2008 b) ―Utility Relocations, Adjustments, and Reimbursement,‖ 23 CFR Part 645A, April 1, 2008 c) ―Accommodation of Utilities,‖ 23 CFR Part 645 B, April 1, 2008 d) Air Space Lease 23 CFR 710 e) ―Transportation of Natural and Other Gas by Pipeline; Minimum Safety Standards,‖ Hazardous Materials Regulation Board, [Title 49 - Transportation] 49 CFR Part 192, October 1, 2007 f) ―Transportation of Liquids by Pipeline; Minimum Safety Standards,‖ Hazardous Materials Regulation Board, 49 CFR Part 195, October 1, 2007

Design Approach The main function of the highway is to provide safe and efficient flow of traffic along highways resulting in proper safety to drivers and all its maintenance crews involved to perform various activities. The design approach for PV systems should avoid any risk of accident while setting up Renewable Energy Installations (REI) near the roadway. With a forecast of solar generation capacity that is expected to grow by 46 gigawatts by the year 2040, it is important that this design approach be set up in a way that will fulfill and ensure the best practices in maintaining safety and performance (Jaffe, 2013).

The AASHTO Road Design Guide (RSDG) is a resource document from which individual highway agencies can develop standards and policies. This guide also includes a synthesis of current information and operating practices related to roadside safety (AASHTO, 2011). While the existing AASHTO RSDG does not have a direct provision for REI, certain assumptions can be made to follow certain principals based on the guidance provided for locating units that are associated with REIs. The Manual on Uniform Traffic Control Devices (MUTCD), AASHTO RSDG (2011) and FHWA safety guidelines are a few reference documents that can used to develop the design approach while setting up REI‘s. Key extracts from the RSDG towards roadside safety and integrity of the REI are as follows:

• Clear zones are the roadside area, starting from the edge of the pavement edge of the highway that has space available for the driver to stop or regain control of a vehicle. A distance of at least 30ft from the shoulder of the highway is recommended. However, the desired width is varied and dependent upon traffic volumes, speeds and roadside geometry.

• Crash cushions are systems used to lower the effects of vehicles by striking obstacles to incur a stop when hit head-on.

• Guardrails are structures along the highway alignment to guide the off track vehicle back to the road. Guardrails could be a suitable solution towards structural support when placed in front of PV array systems to provide breakaway support as it could decrease the severity of collisions thereby preventing direct vehicle collision with the PV array system.

• Fixed/Permanent structures are support systems that are immune to the effects of ambient conditions (e.g. ice and wind loads, temperature) and meet AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals.

• Breakaways are design features which allow a device such as a signage or traffic signal support to break or separate upon impact in order to reduce the severity of an accident. AASHTO standard criteria ensure that breakaway support failures should be permissible when struck head-on by an 1800 lb. vehicle or its equivalent, at speeds of 20mph and 60mph.

• Utility lines such as electrical cables, conduits, water pipes and drainage pipes should be buried underground to the most possible extent. This establishes a consistent prevention and minimizes conflicts between highway and utility facilities ensuring that such accommodations do not adversely affect user safety, otherwise impair the operation of the transportation facility, or conflict with applicable law.

Existing Solar Highways

After understanding that solar highways have several benefits and the potential to provide safe, reliable and affordable renewable energy, several DOT‘s within the United States and from all over the world have a interest in utilizing their ROW effectively by establishing Solar PV plants. The interest among DOTs in pursuing solar PV will likely continue as demand for clean energy grows and the price for solar technologies declines. The Department of Energy (DOE) Solar America Initiative (SAI) has set a goal of PV grid parity with 70 - 100 GW installations by 2030 (DOE, 2008). The government has set ambitious goals for PV deployment and installations over the next 20 years that will be heavily dependent on technological development and cost reductions. Meeting this goal will require improvements in performance efficiency of PV technologies and an increase in manufacturing economies of scale. A few of the solar highway projects that have already been implemented by DOT‘s are described below.

Highway Project -1: Oregon Department of Transportation (ODOT) One of the first initiatives on solar highway installations in the United States was adopted by the Oregon Department of Transportation (ODOT) during the year 2008 to build the first Solar Highway project in Oregon and the nation (Hamilton, 2008). With the intention to reduce energy costs, the ODOT understood the availability of its resources with more than 19,000 lane miles of ROW and developed the solar highway project. The aerial view of the solar highway project at Oregon developed by ODOT is shown in the Figure 4.

Figure 4. Solar Highway at Oregon by ODOT (Source: Hamilton, 2008)

As shown in Figure 4, the project is located at the interchange of Interstate 5 and Interstate 205 near Portland, Oregon. The 104 kW dc ground mounted solar array system consisted of 594 panels producing about 130,000 kWhs annually. In an initiative to develop a new solar highway at the West Linn highway, the ODOT performed a site feasibility analysis and a NEPA methodology to assess associated impacts. None of the resource factors were found to provide negative effects by the PV array system but rather acted as a protective barrier to prevent wildfire from spreading in that area.

Highway Project -2: Massachusetts Department of Transportation (MassDOT) The MassDOT had installed a pilot 122 kW PV system along U.S. Route 44 in the State of Massachusetts (Kreminski, Hirsch, & Boand, 2011). The PV system is located 65 ft. from the state highway on the south facing cut slope beyond the ditch line and behind the guard rail. The design approach towards setting up this PV system indicates that it was placed away from the clear zones and all existing utility lines. Setting up the PV system behind the guard rails also indicates the presence of safety factors being considered to decrease the severity of collisions from passing by vehicles.

Highway Project-3: Ohio Department of Transportation (Ohio DOT) Ohio DOT in conjunction with the University of Toledo deployed a 117.477 kW solar array system in its highway ROW in the Veteran‘s Glass City Skyway (VGCS) bridge, Toledo, Ohio. The aerial view of the solar highway project at the Veteran‘s Glass City Skyway bridge by Ohio DOT is shown in the Figure 5.

Figure 5. Aerial view of the solar highway project by Ohio DOT (Source: Stuart & Phillips, 2012)

As shown in Figure 5, these large arrays of solar panels were installed in the north of the VGCS bridge next to Interstate I-280 in Toledo, OH (Stuart & Phillips, 2012). Feasibility studies were performed to evaluate the solar PV system‘s major concerns such as the proximity to the freeway and observations of glare and glint. The study suggest that no known problems for glare or glint were observed with no complaints from motorists and the glare normally lasts for a portion of the day and for a few months out of the year (e.g. ½ hour a day during summer months).

Highway Project-3: California Department of Transportation (Caltrans) The Caltrans and the Sacramento Municipal Utility District (SMUD) in 2008 partnered to develop solar energy projects at an expected capacity of 1.4MW. Caltrans drafted the airspace lease agreement so that SMUD would be able to govern the use of ROW. The key findings in this project are that mitigation measures for potential impacts associated with glare, aesthetics, air quality, biological resources, cultural resources, geology and soils, hazards and hazardous materials, hydrology and water quality, noise, and transportation/traffic would have to be implemented as part of SMUD‘s proposed project (Burleson Consulting, July 2011). However, it was also determined that the proposed project would not contribute incrementally to a considerable environmental change. The reasons listed indicated that the potential effects of the proposed project were determined to be less than significant and all identified potentially significant impacts would be mitigated to a less than-significant level (wickedlocal.com, 2012). However, when the project went out for construction bid, only one firm responded with a price which SMUD determined too high (Turner, 2011). Thus, the project was never built.

International Projects - European Solar Roadways with Noise barriers

As many European countries tend to utilize all available space, existing noise barriers offered possibilities for the production of electricity through PV (European-Commission, 2000). Switzerland was one among the first European countries to start deploying the PV system along the ROW using noise barriers in 1989 (NOVEM, 2011). Later, several European countries such as Germany, Spain, and Italy had adopted the same application and were called as ―solar- roadways‖ (Federal-Office-of-Energy, 2001). Noise barriers are principally installed to protect an area from noise pollution but can be given a double purpose of also generating renewable energy when facing west through south to east by adding PV panels. The comprehensive list of solar roadways installed in Europe is tabulated in Table 1.

Table 1: Summary of Solar Highways implemented worldwide (Source: Lenardic, Revolucije, & Slovenia, 2011) Rated Year of Country, Location Description Capacity Completion World's first PV noise barrier installed at A13 10 MW Switzerland, Chur 1989 Highway PV noise barrier project on the Autobahn A6 100 kW Sausenheim, Germany 2000 Highway 205 kW Western Netherlands PV noise barrier project along A9 Highway 2000 55 kW De Bilt, Netherlands PV noise barrier along Highway A-27 1995 65 kW North-East of France PV noise barrier along A-21 motorway 2000 220 kW Amsterdam PV noise barrier project along the A9 highway 1998 2.65 MW Germany, Aschaffenburg Solar park Aschaffenburg, noise barrier A3 2009 1 MW Germany, Töging am Inn Noise barrier A94 2007

833 kW Noise barrier along S.S. 434 "Transpolesana" 2010 Italy, Oppeano

730 kW Noise barrier along A22 Brenner Motorway 2009 Italy, Marano d'Isera

600 kW Noise barrier along A92 motorway 2009 Germany, Freising

365 kW Noise barrier along B31 2006 Germany, Freising 283 kW Germany, Bürstadt Noise barrier along B57 2010 180 kW Germany, Vaterstetten 400 m long noise barrier along railway tracks 2004 123 kW Switzerland, Melide Noise barrier along Gothard motorway 2007 101 kW Austria, Gleisdorf Noise barrier along A2 motorway near Graz 2001 100 kW Switzerland, Giebenaach Noise barrier along the A2 motorway 1995 90 kW Germany, Biessenhofen Nestle facility, noise barrier 2010 80 kW Switzerland, Safenwil Noise barrier along the A1 motorway 2001

53 kW Noise barrier along the A31 motorway 2003 Germany, Emden 40 kW Austria, Seewalchen Noise barrier along A1 motorway near Salzburg 1992 Noise barrier along A96 München-Lindau 30 kW Germany, Ammersee 1997 motorway PV system "Stoiadler III" mounted on noise 28 kW Germany, Großbettlingen 2006 barrier in Großbettlingen 24 kW Australia, Melbourne adjacent to Essendon Airport, Melbourne 2007 Bifacial PV noise barrier along the railway 12 kW Switzerland, Münsingen 2008 tracks. First bifacial photovoltaic noise barrier along 10 kW Switzerland, Zürich - 1997 the A1 motorway. First photovoltaic noise barrier along the 9.6 kW Switzerland, Zürich - 1998 railway tracks.

Addressing Solar PV Operations & Maintenance Challenges

Operations and Maintenance (O&M) are critical components of managing solar PV facilities. Grid-connected solar photovoltaic (PV) systems are expected to proliferate over the coming decade and higher penetration levels will put a premium on achieving optimal performance and reliability (EPRI, 2010). Contrary to popular belief, PV power plants are not maintenance free. They require a regimen of continual monitoring, periodic inspection, scheduled preventive maintenance, and service calls. These actions address unplanned outages, repair and restart, and various O&M activities needed to enhance long term uptime, performance, and economic viability. The Table 2 summarizes the associated tasks and the typical frequency with which that O&M activity are typically administered.

Table 2: Summary of O&M activities with typical frequencies (Source: EPRI, 2010) Sr. No Task Frequency (Typical) Preventative Maintenance (PM) 1 Panel Cleaning 1-2 Times/Year 2 Vegetation Management 1-3 Times/Year 3 Wildlife Prevention Variable 4 Water Drainage Variable 5 Retro-Commissioning 1 Time/Year Upkeep of Data Acquisition and Monitoring 6 Undetermined Systems (e.g., Electronics, Sensors) Upkeep of Power Generation System (e.g., 7 Inverter Servicing, Bill of Systems 1-2Times/Year Inspection, Tracker Maintenance Corrective/Reactive Maintenance 1 On-Site Monitoring/ Mitigation Variable As Needed (High 2 Critical Reactive Repair Priority) 3 Non-Critical Reactive Repair As Needed 4 Warranty Enforcement As Needed Condition-Based Maintenance (CBM) Active Monitoring -Remote and On-Site 1 Continuous Options 2 Warranty Enforcement As Needed 3 Equipment Replacement As Needed

The best practices in a PV O&M program that provide a good insight while operating a successful PV O&M program are given below (Nahmias, 2009):

1. Panel cleaning are site-dependent. For example, the cost effectiveness of panel washing can be tied to the amount of dust, dirt, pollen and/or pollution in the site environment; the frequency of rain or snow; and the presence of flat plate versus tilted panel orientation (Gehrlicher-Solar-AG, 2011). 2. Maintenance work performed either early in the morning or later in the evening can avoid heat stress and minimize electrical hazards. 3. Performing site visit in addition to remote monitoring can assist in avoiding potential problems such as broken panels and increase the risks of fire or shorts. 4. Usage of the infrared gun can provide thermo graphic imaging on all electrical systems to determine hot spots where electricity leaks out. 5. Usage of loose concrete gravel or recycled concrete has been the best approach to counter and control weed growth inside the solar facility. 6. Precautions have to be taken while handling weeding machines and lawnmowers as the blades can cause the small gravels and stones to shatter panels. 7. Rain can effectively improve module efficiencies by 3-5% and obviate the need for labor and cost of manual cleanings. 8. Consider appropriate drainage systems within and around the solar plant premises in order to control rainfall water and avoiding probable erosion of top soil. 9. Establish secured fences around the plant system for security issues to protect the PV system from theft.

In summary, maintenance of PV systems is similar maintaining a building infrastructure that operated at a particular high voltage ensuring to minimize production downtime and keeping the facility operating efficiently.

After the assessment of PV O&M challenges, it is also crucial to identify the challenges associated with highway maintenance as PV array maintenance might have an impact on road maintenance. The next section addresses the O&M challenges in the highway.

Addressing Highway Operations & Maintenance Challenges

CDOT has statewide, decentralized, operational multi-functional abilities and provides the citizens of Colorado with quick responses to transportation-related emergencies where expertise in highway and tunnel maintenance and in transportation engineering may be needed. These resources are fully equipped with highway maintenance and construction related equipment.

The road maintenance division of CDOT performs various actives to maintain the road which includes but is not limited to mowing during summer, snow plowing during winter, maintenance of drainage, repairing of pavement, fixing and building of fences, road structures, etc. The right of way serves as a buffer between the traveled way and adjacent private property (CDOT, 1979). The approach to maintenance of the roadside depends on the location of the highway (rural or urban) and the land use sharing border with the ROW.

PV array might have an impact on road maintenance as the array system fencing might alter the mowing operation outside the fencing area. Mechanized equipment is used to perform mowing operation along the right of way in which separate standards are used for urban and rural highways. The grasses on the ROW are usually maintained at a height between 3 inches and 6 inches in the urban areas, while mowing along rural highways are maintained at a height between 4 inches and 10 inches that is extended to all areas in the ROW starting from the pavement edge (CDOT, 1979). The mowing operation is usually carried out at least once in a year or otherwise when necessary. The presence of the PV system will limit the movement of the mechanized equipment thereby limiting the mowing operation. In order to meet the mowing program standard of CDOT, the CDOT noxious weed plan or the use of gravel/stones to cover areas should be used to eliminate or control the existing vegetation and prevent the introduction and spread of existing weeds as a result of project implementation.

Traffic flow, road maintenance, user safety and environment are the major functional departments for operation and maintenance of the highway infrastructure in Colorado. Following are the critical ROW requirements for road operation and maintenance:

. Snow removal during winter, mowing during summer, regular repairing of pavements and structures as per ASHTO guidelines need to be followed and practiced as applicable.

. The maximum speed limit is 75 mile per hour (mph) on the interstate freeway. Rigid objects in the recovery zone are undesirable to avoid potential accidents resulting in severity.

. Lane shift and reduced speed are possible in the work zone. Access road or alternative way to work zone is desirable for smooth road maintenance and traffic flow.

. Vehicle speed less than 55 mph is not allowed in freeway. Slow maintenance vehicle for PV project construction and maintenance might compromise the traffic flow on the highway.

. Steel railings would also have a significant impact when installed to keep people or vehicles from straying into dangerous or off-limits areas. A few experiments were performed to evaluate the crash tests of the steel bridge railings set along the highway in Europe (Ray & Mastova, 2008). The results concluded that the new MDS barrier systems provided protection against the collision of vehicles. The test results provided a positive outcome when vehicles driving had an impact velocity of up to 61 mph (Transportation & Administration, 2012).

. MgCl2, NaCl and salt-sand mixtures are the commonly used deicing agents to melt snow in

the highways. Studies indicate that the current use of MgCl2 pose detrimental effects to portland cement concrete infrastructure and asphalt pavement, cause corrosion damage to the transportation infrastructure, or have significant impacts on the environment (B.A. & W.R., 2008) (Durham, 2010).

As the effects of blowing snow can causes significant impacts on road maintenance, it important to remove snow on regular basis. Removal of snow can also reduce snow the impacts associated to snow drifting. The next section addresses the snow drifting challenges in the highway.

Snow Drifting

Snowdrifts can add significantly to the cost of winter maintenance, and also create serious safety hazards by slippery road conditions causing loss of vehicle control. The other associated impacts related to snow drifting on the highways also causes reduced sight distance on curves and at intersections, obscuring signs, promoting ice formation, reducing effective road width thereby rendering safety barriers ineffective. Drifts contribute directly to pavement damage by blocking ditches, drains and culverts, and serving as a source of water infiltrating under pavement. The blowing of snow brings on ice on the road and reduces visibility. The primary cause of icy roads in wind-exposed areas—melting extracts diurnal solar radiant heat stored in the pavement and substratum, and the quantity of snow blowing across a road can be hundreds of times greater than direct snowfall (R. D. Tabler, 2003).

It is important to properly adhere to engineered mitigation measures and describe in detail the processes involved in snow transport and deposition, provide specific guidelines for designing structural and living snow fences, and present recommendations for designing drift free roads. Installation of snow fences were found to be the best mitigating action to counter snow drifting. Several studies were conducted by Tabler in Wyoming to find the effects of snow fences on crashes and road closures. The effectiveness of snow fencing when placed along the highway is shown in Figure 6 (Tabler & Meena, 2006)

Figure 6. Snow fences implemented in the State of Wyoming (Source: Tabler & Meena, 2006)

As shown in Figure 6, snow fences installed adjacent to highway I-80 in Wyoming, counter snow drifting when the snow gets accumulated on the fence. Similar snow deposition in Colorado will also be a major concern to the CDOT maintenance department. The installation of PV array system along the highway ROW might affect the existing snow drifting and depositional pattern conditions, thus causing the snow to build up on the roadway.

Quantifying the blowing snow problem is site specific and it involves observations, collection of data and a series of calculations like snow accumulation season, potential snow transport, prevailing transport direction, fetch distance and mean annual transport. Snow drifting depends upon the snow mass flux, concentration, height and wind velocity. Wind velocities are determinant factors for the potential snow transport direction. With different climatic and topographical conditions exhibited by different states within the United States, it is important to perform an site specific evaluation to mitigate snow drifting (R. D. Tabler, 1994).

Site specific parameters such as the orientation, height, porosity of the fence and the setback distance from the highway are needed to be considered while setting up snow fences. During the snow accumulation season, most of the snow is accumulated on the leeward side of the snow fence. Figure 7 shows the initial stage of drift development nearby the snow fence.

Figure 7. Snow fence recommendation by Tabler (Adapted from: Tabler, 1991)

As shown in Figure 7, snow is accumulated to a distance of 35H (where H is the height of the fence) from the snow fence at the initial stage of drift development. Based on the study in Wyoming, it is recommended that the distance between fence and road should be at least 35 times the height of snow fence (R. D. Tabler, 1991). Thus, only beyond this distance should the array system be located in known high snow drifting areas. The research recommended that snow fences be placed at the appropriate distance from the roadway to reduce snow deposition on the highway.

The simple mitigation to counter snow drifting is to avoid placement of PV array system in areas susceptible to high snow drifting. Low lying ROW land compared to the elevation of the highway of this site might help to avoid snow deposition and snow drifting along the highway. However, the siting of the PV system should be coordinated with the DOT maintenance personnel as the snow behavior is site specific and an individual analysis is needed for a given site considering the various topographical site and climate conditions.

Since wind velocity can be considered as one of the main factor that influence the snow drift direction, PV array systems should be sited on the downwind side of roadway. (R. D. Tabler, 2003). In addition, the majority of the snow drifts and accumulation will trail off after few feet from the fence and the amount of snow that reaches to the road will be much smaller (if any). Living fences (a series of natural plants, trees, bushes etc. in rows) and mechanical fences (manmade structures of wood, steel or synthetic fiber) are commonly used snow fences used to mitigate the above issue.

Having identified the effects of blowing snow as significant impacts on road maintenance, another parallel impact on solar highways is the glare from the solar panels that possesses a threat to the driving motorists‘ along the highway. The next section addresses the glare affects in the highway.

Glare

It is very important to understand the principle of reflectivity before analyzing its potential impacts (Arce, 2010). Reflectivity refers to light that is reflected off of surfaces. The impacts of reflectivity are glint and glare which can cause a brief loss of vision (also known as flash blindness) (IFALPA, 2012). The reflectivity varies greatly among technologies with concentrated solar power technologies being highly reflective and PV being primarily absorptive. The analysis will depend on site-specific factors and the following section summarizes the issue of reflectivity followed by the methodologies to assess its potential impact.

Reflectivity Basics Flat-plate photovoltaic solar panels are designed to absorb sunlight in order to convert it into electricity. Mono-crystalline silicon wafers, the basic building block of most photovoltaic solar modules, absorb up to seventy percent of the sun‘s solar radiation in the visible light spectrum (Company, 2011). Solar cells are typically encased in a transparent material referred as an encapsulate and covered with a transparent cover film, commonly glass. The addition of these protective layers further reduces the amount of visible light reflected from photovoltaic modules. Photovoltaic panels use the absorbed energy in two ways: 1) the panels generate electricity and 2) the mass of the panels‘ heat up.

In order to maximize the efficiency of electricity production, the panels are designed to minimize the reflection of sunlight. The application of anti-reflective coatings and surface texturing of solar cells are commonly used to minimize this impact. A combination of these techniques can reduce reflection to a few percent. Most solar panels are now designed with at least one antireflective layer and some panels have multiple layers.

One measure of the reflectivity is albedo calculated by the ratio of solar radiation across the visible and invisible light spectrum reflected by a surface. Albedo varies between 0, a surface that reflects no light, and 1, a mirror like surface that reflects all incoming light. Table 3 presents the albedo of common reflective surfaces at different angles (Burleson Consulting, 2011).

Table 3: Albedo Chart for Material Reflectivity of common reflective surfaces (Source: Burleson Consulting Inc., 2011)

Albedo Chart - Material Reflectivity of Common Reflective Surfaces Incident Angle in Degrees Common Relflective Surfaces 0 15 30 45 60 75 90 Steel 37% 39% 46% 57% 70% 83% 94% Fresh Snow 35% 37% 44% 54% 67% 79% 90% Ocean Ice 27% 29% 34% 42% 52% 62% 70% New Concrete 21% 23% 27% 33% 41% 48% 55% Desert Sand 16% 17% 20% 24% 30% 35% 40% Green Grass 10% 10% 12% 15% 19% 22% 25% Standard Glass 8% 9% 11% 13% 16% 19% 22% Plexiglass 8% 9% 10% 12% 15% 18% 21% Plastic 7% 7% 9% 11% 13% 16% 18% Decidious Trees 7% 7% 9% 11% 13% 16% 18% Bare Soil 7% 7% 8% 10% 13% 15% 17% Conifer Forest 6% 6% 7% 9% 11% 13% 15% Worn Asphalt 5% 5% 6% 7% 9% 11% 12% Solar Glass 4% 4% 5% 6% 8% 9% 10%

Sloar Glass with Anti reflective coating 2% 3% 3% 4% 5% 6% 6% Material Reflectivity ( % of brightness) sun's Fresh Asphalt 2% 2% 2% 2% 3% 4% 4%

From Table 3, it can be observed that the solar panels have a lower reflectivity than the area‘s prevailing ground cover, agricultural crops etc. The reflectivity of a surface, or albedo, varies with the type of material that covers it. The solar panels have a reflectivity of around 30% – similar to the reflectivity of current site surface materials such as dry sand at 45%, needle-leaf coniferous trees at 20%, grass-type vegetation at 25% and broadleaf deciduous trees at 10%.

The amount of light reflected off of a solar panel surface depends on the amount of sunlight hitting the surface as well as the surface reflectivity. The amount of sunlight interacting with the solar panel will vary based on geographic location, time of year, cloud cover, and solar panel orientation. Often 1000W/m2 is used in calculations as an estimate of the solar energy interacting with a panel when no other information is available.

The reflectivity from solar projects will vary based on the type of solar power system, its materials and design. Solar PV employs glass panels that are designed to maximize absorption and minimize reflection to increase electricity production efficiency. To limit reflection, solar PV panels are constructed of dark, light-absorbing materials and covered with an anti-reflective

22 coating. Today‘s panels reflect as little as 2% of the incoming sunlight depending on the angle of the sun and assuming use of anti-reflective coatings (Evergreen-Solar, 2010).

While the amount of light reflected off a surface is important, the nature of the reflected light is even more important when assessing the potential for flash blindness. One important characteristic of light to consider is whether the reflected light is ―specular‖ or ―diffuse‖. Specular reflection reflects a more concentrated type of light and occurs when the surface in question is smooth and polished. Glint, also known as specular reflection, is a momentary flash of light that is produced from direct reflection of the sun. Glint is a significant source of visual issues and can cause viewer distraction. Examples of surfaces that produce specular reflection include mirrors and still water. Field trial tests on glint were performed by the U.S Army soldier system command as early as 1996 to improve the integrity of the existing US glint threshold algorithm for creating better eye armor design tools (Chevalier & Kimball, 1998). Diffuse reflection produces a less concentrated light and occurs from rough surfaces such as pavement, vegetation, and choppy water. Glare is defined as a continuous source of excessive brightness caused by diffused or scattered reflections. It is not the result of direct reflection of the sun but rather a reflection of the bright sky around the sun. Glare is significantly less intense than glint (Company, 2011). All surfaces in reality produce a mixture of both types of reflections. Outside of very unusual circumstances, flash blindness occurs from specular reflections. The exact percentage of light that is reflected from PV panels is currently thirty percent. However, because the panels are a flat, polished surface, it is a reasonable assumption that most of the light is reflected in a specular way and thus is fundamentally different from that reflected off a rougher surface (Federal-Aviation-Administration, 2010).

An experiment conducted by the Good Company for a proposed Solar Highway project at West Linn, Oregon reports that mono-crystalline silicon solar cells absorb two thirds of the sun light reaching the panel‘s surface. That means that only one-third of the sunlight reaching the surface of a solar panel has a chance to be reflected. As a result, the reflected energy percentage of solar glass is far below that of a standard glass and more on the level of smooth water (Shields, 2010).

Completing an individual glare analysis A technical guidance for evaluating selected solar technologies from the Federal Aviation Administration on Airports details that evaluating glare for a specific project should be an iterative process that needs to performed in one or more methodologies (Plante, 2010). The solar service provider should coordinate closely with the environmental specialist to collect the data necessary for the particular project review. These data should include a review of existing site conditions and a comparison with existing sources of glare as well as related information obtained from other projects with experience operating solar projects. Depending on site specifics (e.g., existing land uses, location and size of the project) an acceptable evaluation could involve qualitative analysis of potential impact, a demonstration field test with solar panels at the proposed site in coordination with State DOTs. Geometric analysis to determine days and times when an impact is predicted might be needed. Further, an assessment of the ―visual resources‖ at the site and surrounding environment is highly recommended to analyze and mitigate the potential hazards from glint & glare (Clifford K. Ho, 2010).

Software tools for analyzing glare hazard

There are several photovoltaic (PV) simulation tools available in the market for producing estimates of PV system power production (kW), energy (kWh), yield (kWh/kWp) and also analyze the associated glare hazards. These simulation tools quickly adapt the model to accurately reflect new module and mounting products and allow to make use of measured performance data from different systems for model-level and system-level validation. Basic data such as the specific location and design information from a user interface, enables the simulation tool to calculate and compute the necessary data.

TRIVIUM TRIVIUM (Piña, Mayora, & Huarte, 2010) was developed at the Technical University of Madrid to identify and quantify driver vision impairment problems originated by sun glare and to facilitate the design of counter measures to prevent potential safety hazards. The computer program written in MATLAB is based in a methodology to determine the days and times of the year when sun glare may impair drivers‘ vision on a particular road section depending on its geographical location, geometric design of the road, and the physical characteristics of its environment. The software tool has already been used in Spain and identified in several studies

24 of sun glare hazard in locations such as tunnels, freeway entrance ramps, intersection, approaches on the National Motorway A-5 (Spain).

Solar Glare Hazard Analysis Tool (SGHAT) The Sandia Laboratories have developed a web-based interactive tool called Solar Glare Hazard Analysis Tool (SGHAT) that provides a quantified assessment of when and where glare will occur throughout the year for a prescribed solar installation and potential effects on the human eye at locations where glare occurs. The SGHAT employs interactive Google maps where the user can quickly locate a site, draw an outline of the proposed PV array and specify observer locations or paths.(Laboratories, 2012) The latitude, longitude, and elevation are automatically recorded through the Google interface, providing necessary information for sun position and vector calculations. Additional information regarding the orientation and tilt of the PV panels, reflectance, environment, and ocular factors are entered by the user.

If glare is found, it calculates the retinal irradiance and subtended angle (size/distance) of the glare source and predicts potential ocular hazards ranging from temporary after-image to retinal burn. (Clifford K. Ho, 2010). The results are presented in plot that specifies when glare will occur throughout the year, with color codes. It can also predict relative energy production while evaluating alternative designs, layouts, and locations to identify configurations that maximize energy production while mitigating the impacts of glare. The input variables of the software are the height above the ground level, orientation of the array, tilt of the panels, height of the solar panels, rated power of the module and reflectivity of the solar panel (Ho & Sims, 2013).

Hazards from reflection of solar radiation from PV panels include potential for permanent eye injury (e.g., retinal burn from concentrated sunlight) and temporary disability or distractions (e.g., after-image). The impacts of glint and glare on eyesight include discomfort, disability, veiling effects, after-image and retinal burn. Prolonged exposure to ―discomfort glare‖ may lead to headaches and other physiological impacts, whereas ―disability glare‖ immediately reduces visual performance. Disability glare can include after-image effects, flash blindness and veiling, such as that caused by solar glare on a windshield that might mask pedestrians or vehicles. Sandia Laboratories have studied and summarized the potential impacts to eyesight as a function of retinal irradiance (the solar flux entering the eye and reaching the retina) and subtended source

25 angle (size of glare source divided by distance) (Ho, February 16, 2011). The reflected light can be characterized as a combination of specular (mirror-like) and diffuse (scattered) reflections.

Retinal irradiance (W/cm2) is the solar flux entering the eye and reaching the retina which is a function of irradiance at the cornea (front of eye). The subtended angles are the size of glare source divided by distance from the observer. The subtended angle of sun is constant 9.3 mrad and the subtended angle of PV systems varies with the distance of the observer and PV system glare size. Solar receivers produce more diffuse reflections with lower solar intensities but greater subtended angles. Therefore, the potential impact of different retinal irradiances is defined as a function of subtended impact of retinal irradiance and subtended angle to the vision impairment. The ocular hazard plot using the subtended angle and the retinal irradiance is shown in Figure 8.

Figure 8. Ocular Hazard Plot (Source: Ho & Sims, 2012)

Figure 8 shows ―Ocular Hazard Plot‖ with three regions: (1) potential for permanent eye damage (retinal burn), (2) potential for temporary after-image, and (3) low potential for temporary after-image. The green region depicts a low potential for after-image and ocular impacts due to the low retinal irradiances (i.e solar flux entering the eye and reaching the retina) and/or subtended angles of the glare source (i.e size of the glare source divided by the distance).

The exposure time for this study was determined as 0.15 seconds. As the subtended source angle increases, the safe retinal irradiance threshold decreases because of the increased size of the retinal image area, and, hence, increased energy applied to the retina. When a driver is approaching the glare source (PV array system), the subtended angle will increase leading to higher potential for after image (yellow region) or practically as the driver approaches the source he/she will exposed to more glare hazard because of the shorter distance to the source. In the yellow region, a sufficiently high retinal irradiance may cause a temporary after-image (direct viewing of sun is 10 W/cm2).

For a given retinal irradiance, smaller source angles yield smaller after-images, and the potential impact is less. With the higher irradiance, the potential of glare as is sufficiently large causing permanent eye damage from retinal burn (red region). If glare is found, the tool calculates the retinal irradiance (flux of radiant energy on the retina) and subtended angle of the glare source (size of glare source divided by distance to the eye) to predict potential ocular hazards ranging from temporary after-image to retinal burn. Most people have experienced flash blindness after viewing a flash bulb from a camera or a bright light in a darkened room. The visual recovery times would be between 4 – 12 seconds for the light values ranging from ~650 – 1,100 lumens/m2, which corresponds to approximately 7 – 11 W/m2 of solar irradiance at the eye as a result occurring mostly in yellow region in our study.

When the retinal irradiance or subtended angle is sufficiently large, permanent eye damage from retinal burn may occur (e.g., from concentrating mirrors). Below the retinal burn threshold, a region exists where a sufficiently high retinal irradiance may cause a temporary after-image, which is caused by bleaching (oversaturation) of the retinal visual pigments. The size and impact of the after-image in the field of view depends on the size of the subtended source angle. For a given retinal irradiance, smaller source angles yield smaller after-images, and the potential impact is less. Sufficiently low retinal irradiances and/or subtended angles of the glare source have a low potential for after-image and ocular impacts.

The article from Ho indicates that there are a number of factors can affect both the intensity and perceived impact of glare. The direct normal irradiance (DNI), reflectance, distance, size and orientation of the reflecting surfaces, and human factors should be taken into consideration. The DNI is the amount of solar irradiance striking a surface perpendicular to the

27 sun‘s rays. For example, a 3-kilowatt residential rooftop PV array will appear small relative to a 5-megawatt PV array at a given distance. The glare on the larger array can therefore grow to much larger sizes at longer distances than on the smaller array, yielding a greater potential for ocular hazards. Orientation of the array will also impact the effective viewable area, as well as the reflectance. Human factors such as ocular properties (pupil size, eye focal length, ocular transmittance) and light sensitivity will affect the retinal irradiance, subtended angle and perceived impact of the glare.

The SGHAT software will further be used in the ―Experimentation & Methodology‖ section of this thesis to analyze the glare impacts at the solar PV system inside the Colorado State University-Pueblo campus and the other potential locations identified along the Colorado interstate highway.

Reducing Solar Glare: The use of textured glass can reduce the normal specular reflectance of PV modules to ~1 to 2 percent (Ho & Sims, 2013). Application of this coating will help in reducing the reflectance, and the increased scatter of the reflected beam will lower the retinal irradiance and potential for ocular hazards.

New manufacturing concepts of solar modules include the use of ―high-transmission, low iron glass‖ which absorbs more light, producing smaller amounts of glare and reflectance than normal glass (Technical-Support, 2009). The glass composition used has a reduced percentage of FeO permitting the glass to exhibit a combination of high visible transmission and high total solar transmission (Scott V. Thomsen, 2009).

The usage of stippled solar glass in the modules is highly recommended for its superior refractive/reflective properties (Technical-Support, 2009). The application of stippling in the modules allows more light energy to be channeled/ transmitted through the glass while diffusing the reflected light energy. The modules will look hazy and less-defined than the reflection from standard glass.

While most solar panel manufacturers‘ provide certificates for safe levels of glare reflectivity that are decisively lower than other standard residential and commercial

reflective surfaces, it may not be applicable when the same panels are installed with varying site conditions. As a result, it is suggested that customers and installers need to discuss and take appropriate actions on any possible concerns related to glare hazards with neighbors/cohabitants near the planned PV system installation.

While mitigating the solar glare issues by using anti-reflective coatings, glass texturing, using blinds and screens have been widely recommended, perhaps the most effective method is through proper design and siting of the solar energy system, with consideration of its size, orientation, optical properties and location relative to key observation points.

Glare from direct sunlight has been mostly predictable and have been conclusive that most problems occur during the mornings and evenings when the sun is close to the horizon. Awareness to the driving public by providing them prior form on intimation on possible glare at specific sites by displaying road signage along the highway can help in reducing the impact.

Figure 9. Illustration of road signage on solar glare displayed at Massachusetts (Adapted from: Ho, 2012)

The Figure 9 shows an illustration of road signage displayed on the Massachusetts State route providing the drivers with a cautionary warning of dangerous solar glare in the mornings.

Software validation for glare analysis at Colorado State University – Pueblo

With access to the SGHAT software from Sandia Laboratories, it was important to perform a software validation for glare analysis on an existing solar PV system. This trial and error on the software experimentation will achieve in providing evaluation parameters considered by the software to provide corresponding results at actual site conditions. For software validation, a glare analysis on the existing solar PV system inside the Colorado State University- Pueblo‘s campus was performed. The outcome of this validation ensures the respective settings and standards are being met by the software, for the detailed experimentation to be conducted in the thesis research.

In 2009, a 1.2-megawatt solar power system was installed inside the campus of Colorado State University-Pueblo as an initiative to develop clean energy projects and also promote renewable and sustainable energy. The installation of the solar PV system inside the university‘s premises makes it one of the largest at an educational institution in the US and will help the university to control utility costs as prices and usage increase over time. The solar array covers 4.3 acres with more than 6,800 photovoltaic panels, and is capable of generating approximately 1,800 megawatt hours of electricity per year (AASHE, 2009). An Aerial view of the PV system at the university campus is shown in Figure 10.

Figure 10. Aerial view of the solar PV system at Colorado State University – Pueblo (Source: AASHE, 2009)

The technical details of the solar PV system installation have been captured in the Table 4.

Table 4: Technical details of the solar PV system at the Colorado State University – Pueblo (Adapted from: AASHE, 2009) DESCRIPTION DATA Total Capacity 1200 Kilowatts Annual Production 1,800,000 KWh Installation Base Ground / Pole mount Installation Type Fixed Axis – Fabricated aluminum frames PV Panel Type BP Solar BP 3170 170 watt PV panels Panel Numbers 6800 Inverter Type Xantrex GT100 and GT250 Grid Tie solar inverters Total Area 4.3 Acres Ground Level 2 coordinates at fixed ground level 2 coordinates at a slight elevated slope of 10-15 degrees. Latitude/ Longitude Coordinates 38.313453,-104.574885; 38.313458,-104.574106 (iTouchmap.com, 2014) 38.311724,-104.574063; 38.311291,-104.574575 Panel Facing Direction South (Barcelona-Field-Studies-Centre, 2013)

While primary analysis of this experiment is just to validate the SGHAT software, this experiment will also be able to prepare a high-level analysis of the potential for the reflection of sunlight at the 1.2 MW solar site at Colorado State University-Pueblo. This analysis will focus on the direct reflection impacts from the university‘s solar farm project on nearby traffic corridors, roads and buildings in and around the university campus area.

Figure 11. Key observation points considered for evaluation (Adapted from: SGHAT software, 2012)

As shown in Figure 11, eight observation points have been identified that have a line of sight to the solar PV system. These observation points have been strategically placed in different directions to take the distance from the plant into considerations (Barcelona-Field-Studies- Centre, 2013). The distances for this experiment vary from 55 ft. to 980 ft. for calculation purposes.

Specific observation points have been considered to ensure the software provides appropriate results that could be verified manually. For example, observation points 1 and 4 had been chosen, knowing that those points do not possess a glare threat owing to their direction which does not have a direct line of sight with the solar PV system.

The site specific details like the calculated azimuth angle, the tilt of the solar panels, and the rated power along with the latitudes and longitudes of the system location are to be entered in order to retrieve the correct analysis results (RREDC, 2013) (iTouchmap.com, 2014) (Department-UCSB, 2010). For this experimentation model, the tilt angle of the solar panels was taken as 16.5 degrees with a southern orientation having an azimuth angle of 180°. Other factors such as the subtended angle from the sun, the pupil diameter of the human eye, the focal length and the time interval are calculated automatically or will be set as default values. These default values can however be changed based on independent experiment analysis. The total ground elevation is auto-calculated based on the latitude and longitude coordinates. The height above ground was considered to be 7 ft. as an approximation of the height of the solar panels.

Table 5: Latitude & Longitude coordinates at Colorado State University – Pueblo (Source: SGHAT software, 2012) id Latitude (deg) Longitude (deg) Ground Height above Total Elevation ground (ft.) elevation (ft.) (ft.) 1 38.3134523739 -104.574893117 4951.21 7.0 4958.21 2 38.3134523739 -104.574088454 4937.08 7.0 4944.08 3 38.3112046862 -104.574088454 4925.66 7.0 4932.66 4 38.3112046862 -104.574893117 4943.34 7.0 4950.34

Analyzing the potential for solar glare resulted in 6 out of the 8 observation points having influence either as potential for temporary after image or a low potential for temporary after

32 image. The analysis indicate that several of the observation points would have direct glare impacts from the university‘s solar site on nearby traffic corridors, roads and buildings in and around university campus area. The times for occurrence would be in the evening hours from around 18:00 to 18:30 from the month of April to September. A sample of the glare analysis from observation point-2 is provided in Figure 12 to indicate the time for the glare occurrence during 2014.

Figure 12. SGHAT analysis sample for Colorado State University – Pueblo (Source: SGHAT software, 2012)

Results & Conclusion:

The below summary indicates the results obtained from the SGHAT software while analyzing the glare impact for the 1.2 MW Solar PV system at Colorado State University- Pueblo‘s campus. The individual analyses have been performed for all 8 observation points and the results have been published in the Appendix part of this document. The results indicate a possibility of low potential for temporary after damage and a potential for temporary after damage at the present site. The potential level for glare damage will have several other factors to be considered such as whether the impact occurs from either a stationary phase or while traveling in a vehicle with a corresponding speed of the vehicle movement as well as the height of the vehicle. The Table 7 summarizes the distance from the solar PV system, its direction of orientation and the glare results.

Table 6: SGHAT Results for Glare analysis at the Colorado State University – Pueblo (Adapted from: SGHAT software, 2012) OBSERVATION DISTANCE DIRECTION STATUS POTENTIAL GLARE DAMAGE Observation Point -1 307 Ft. South West No Glare - Observation Point -2 700 Ft. West Glare Potential for temporary after damage Observation Point -3 111 Ft. West Glare Low Potential temporary after damage Observation Point -4 144 Ft. North No Glare - Observation Point -5 55.39 Ft. East Glare Low Potential temporary after damage Observation Point -6 80.12 Ft. West Glare Low Potential temporary after damage Observation Point -7 605 Ft. West Glare Potential for temporary after damage Observation Point -8 983 Ft. North West Glare Potential for temporary after damage

This experiment suggests that the SGHAT software produces reliable results with respect to the observation points. From the Table 6, observation points 1 and 4 do not indicate any source of glare threat, as anticipated. As these observation points will not have a direct line of sight to the solar PV system, since they are at a higher elevation and with a different direction orientation, they will not possess a glare threat and the same can be verified manually. It was expected that software also reproduces similar results which was done so ensuring the validity of the software and deemed fit for further analysis and experimentation in this research.

Evaluating the various risk impact methodologies

Risk evaluation is the process of determining the risks are acceptable or unacceptable and need treatment which can be achieved through necessary assessment. Risk assessment is a systematic and holistic approach. Risk decisions should be guided by established risk criteria and tolerance of the department, risk owners and other stakeholders that may be impacted by the risk (Secretarait, 2013).

Popular risk analysis techniques that are practiced are Failure Mode and Effects Analysis (FMEA), and system based techniques like analytic hierarchy process, multi-objective analysis, decision tree analysis and system based risk analysis. It has also been identified that the lack of consistency, vagueness of information, and unfamiliarity with design to cost concept are some of the weaknesses of these risk analysis techniques.

FMEA is a systematic process for identifying the most critical potential design and process failure modes before they occur, in order to eliminate their effects at early stages and refers to errors found in a product or process. This involves a step by step procedure for identifying all failure modes followed by analyzing the consequences and prioritizing in a sequential manner. Elements of the FMEA technique involve severity (seriousness or effects of the failure), Occurrence (frequency of failure), detection (ability to detect the failure) and the Risk Priority Number (RPN) which can be obtained by multiplying all the elements mentioned above (Reliasoft, 2003). Systems Engineering is an interdisciplinary field of engineering that focuses on how complex engineering projects should be controlled and managed over the complete life cycle, which comprises planning, integration and execution. This decision making process involves evaluating qualitative and quantitative factors in a systematic manner. This is accomplished by integrating three major activities consisting of development phase, system engineering process, and life cycle integration and serves the following purpose (Dadpouri & Nunna, 2011):

a. Gives an understanding of the system‘s nature, functional behavior, and interaction with what exists in its environment. b. Optimizes, improves and streamlines the decision making process in different phases of planning, design, development, operation and management.

c. Identifies, quantifies and evaluate risks, uncertainties and variability‘s of decision making process

Strengths and weaknesses Each of the above models has their own strengths and weaknesses. While the FMEA model is very flexible and can be most useful from the earliest stage of design and development of the decision making process its weaknesses include inconsistency in the ranking of severity, occurrence, detection of risks and also difficulties in translating the qualitative data into quantitative data which is necessary for weighing the risks and ranking them. Similarly, while the system-based technique has the advantage of the built-in nature of handling conflicting factors, it provides less priority to certain elements such as environmental effects which are not tangible in the short term.

Selecting the appropriate risk impact methodology

From the literature assessment on evaluating the appropriate risk impact methodologies, it is evident that both the FMEA and the Systems based risk analysis are sensitivity based analysis techniques that will require qualitative or quantitative data, with specific project requirements having all the necessary elements identified with appropriate risk criteria.

. The Risk Priority Number (RPN) is a technique for analyzing the risk associated with potential problems identified in a FMEA model. RPNs calculated at the level of the potential causes of failure (Severity x Occurrence x Detection). These potential causes of failures are determined by 1. Severity, which rates the severity of the potential effect of the failure. 2. Occurrence, which rates the likelihood that the failure will occur and 3. Detection, which rates the likelihood that the problem will be detected before it reaches the end-user/customer (Reliasoft, 2003). . The Four square method of the systems based risk analysis is an alternate evaluation technique that can be used in this study to assess the evaluation of risk and likelihood as either high or low. The values can be placed in the quadrant depending upon the likelihood and severity assessment to categorize the same in impacts associated to either being low or high respectively.

After assessing the various risk impact techniques and the multiple options available for the analysis, it was concluded that the use of the system based risk analysis technique would be the most appropriate and systematic method towards this research for evaluating an impact matrix. However, the glare analysis in this research will be able to provide data that can be collected towards calculating the severity, occurrence and detection. With this, the risk priority number using the FMEA can be calculated for the glare analysis.

Figure 13. Proposed risk analysis model for research evaluation (Adapted from: Reliasoft, 2003 & RIT University, 2011)

The proposed risk analysis assessment will be performed in two different sections. The frame work of this evaluation is given in the Figure 13. The first evaluation involves performing the risk priority number through the FMEA model based on the data collected from the glare analysis experiment.

The overall risk analysis of this research through the impact matrix model will be evaluated through the systems engineering analysis through the four square method, by placing the variables in applicable quadrants based on the likelihood and severity assessment to categorize the respective assessment.

Summary of the Literature Assessments The following were observed as primary conclusions to be taken into consideration for further exploration.

Solar Highways Solar Highways have evinced tremendous opportunities to put renewable energy onto the power grid and add value to the public‘s transportation system right of way. Several projects have been executed in the United States and around the world to demonstrate the success of developing PV projects in the highway right of way.

Operation & Maintenance: 1. The Operation & Maintenance of a solar PV system were considered to have a high impact on safety as the solar highways would require maintenance of both the highway & solar PV system as parallel activities. 2. PV systems are not maintenance free. 3. O&M activities for the solar plant are standalone activities and have no correlation with highway maintenance. 4. The Magnesium Chloride used as deicers to melt the snow can cause corrosion damage to the transportation infrastructure, or have significant impacts on the environment.

Safety: 1. Steel railings/Guard rails along the highway would be providing a vital safety factor as a part of the ROW characteristics when site locations have lesser ―clear zones‖ 2. Implementation of fixed structures, break away structures and crash cushions can reduce fatal accidents. 3. Utility lines should be buried underground whenever possible. 4. PV array systems should be sited on the downwind side of the roadway. 5. Mowing operation are usually carried out at least once in a year or otherwise, when necessary.

Snow Drifting: 1. Blowing snow can cause visibility problems. 2. Installation of snow fences are the mitigating action to counter snow drifting.

3. Snow fences close to the highway can increase the amount of snow deposition on the road. 4. Quantifying the blowing snow problem is site specific.

Glare & Glint The Glare and Glint effects on a solar PV system were considered as a high risk factor. The following are the key points: 1. As per the albedo chart for material reflectivity of common reflective surfaces, solar panels have a lower reflectivity than the area‘s prevailing ground cover, agricultural crops etc. 2. Deaths of two people have been reported when a car collided with a van travelling in the opposite direction at the A303 Highway at IIminister, South West Somerset, New England on August 30th 2012. It is debated that the highway with the solar panels in a dangerous stretch of road posing distractions to traveling motorists and increasing fears of the solar farm ‗glare‘ risk. It was noted that light reflection prevails on the road very early in the morning and late in the evening (Banks, 2012). 3. It is highly recommended to perform a detailed glare /glint performance review on the site before setting up the solar plant and use anti-reflective coatings on the panels. 4. The SGHAT software, as an analysis tool can provide glint and glare ocular hazard analyses for proposed/existing solar installations near airports, roads, workplaces, and communities. 5. Road signs / warning signs on possible glare are common precautionary measures implemented by several DOTs.

Risk impact methodologies: 1. Risk impact decisions should be guided by established risk criteria. 2. Continuous monitoring, documentation and periodic reviews of the identified risk criteria should be practiced to assess conditions and perform mitigations. 3. Commonly practiced risk analysis techniques include FMEA and systems-based risk analysis. 4. Appropriate techniques should be followed based on available qualitative or quantitative data, project requirements and the elements necessary to be evaluated.

Chapter 3 – Objective

The trend of setting up PV systems along the highway has been growing significantly in the U.S. In the state of Colorado alone, the seventh state in terms in solar generation, several investors have installed PV systems on the ROW or adjacent to the highway. These projects enhance the sustainability portfolio of these businesses and provide several economic benefits in the long run. In the last couple of years the PV system projects grown from none to a handful adjacent to the highway. Whether it is within a ROW or not, these projects could affect the operation of the highways.

The primary objective of this study is to identify critical safety and operation and maintenance impacts, and recommend potential mitigation considerations associated with the planning, design, construction and operation and maintenance of PV systems. These identified factors will provide a roadmap to determine the impact analysis by developing a comprehensive matrix to account for the potential factors of solar highways.

Studies of the potential safety and road maintenance impacts of PV array installation along the ROW have been used to identify and evaluate the current ROW physical characteristics and operational conditions to various PV design criteria variables and provide the following deliverables through this research:

• Develop a process flowchart with the life cycle stages for setting up solar PV systems in ROW‘s along the highways. • Study and analyze the impact of highway PV arrays on drivers‘ safety and road maintenance through the impact matrix. • Determine the degree of potential impact to user safety and road maintenance along with risk factors and the probability of occurrence. • Identify and list the critical risk factors in PV array deployment and develop risk reduction strategies through mitigations along with applicable design/siting criteria.

Chapter 4 –Methodology

The study framework for this research involves key inputs from the literature assessment, field visits performed at existing solar plant facilities and potential sites, expert opinion through interviews and discussions from key personnel having domain knowledge and also making use of several tools and software for the analysis and evaluation of the experiment conducted. The project development outlines with appropriate flow having the various stages identified in the methodology outline have been depicted in the chart given in Figure 14. The following method was developed and implemented to achieve the research objectives:

Select suitable ROW locations along the Colorado Highways with adequate solar resource potential. Conduct onsite evaluations of the potential ROW locations. Coordinate with CDOT representatives and other key personnel having domain knowledge. Perform glare analysis studies on the ROW locations. Develop and apply the applicable assessment criteria through process control flow charts and impact matrix.

Qualitative Analysis

Figure 14. Project development outline for research assessment

Field visits of solar PV systems within or near highway ROW areas:

This study involved meetings and field visits of organizations that have implemented solar PV systems within or near the highway ROW areas. The study was conducted to observe site conditions, physical characteristics and evaluate the present modeling variables to validate information collected during literature assessment and expert interviews. The field visits provided an insight on actual and realistic impacts that may occur with solar PV systems in the ROW. A summary of the field visit is provided in Table 7.

Table 7: Field visit summary

DENVER NORTH WEST DENVER FEDERAL DESCRIPTION INTERNATIONAL PARKWAY CENTER AIRPORT Project Location BroomField, Boulder, Co DFC, Lakewood, Co DIA, NE Denver, Co Plant Capacity 10Kw per site 1.17 MW 2 MW Total Plant 10 Kw x 7 No‘s = 63 Kw 7 MW ( 8 sites) 8 MW (3 sites) Capacity tracking tilts every 6 Tilting Angle 18° - 24° 20° minutes No. of Panels 22 Panels 6192 Panels 9254 Panels Area at 7 different location 7 acres 7.5 acres 216 Watts (Sharp Per Panel Rating 220 Watts 190 Watts modules) 11000 MW hours / Plant Production 7865 KW Hour / Year 3.4 Million KW / hour year Direction of South facing South facing South facing Panels Module Height 5Ft Front; 10 Ft Back 2 Ft Front; 13 Ft Back 3Ft Front; 10 Ft Back from ground level Clear Zone 30 Ft More than 100 Ft 90 Ft. Cut Slope for YES – Slide Slope 3:1 NIL – Flat Land NIL – Flat Land Panels Maintenance $15- $25 / kW/year (low) approx. $8000 (low) no data Cost Truck with water Water -> Brush-> O & M System Water -> Brush-> Water spray Water O & M Twice during the last None 2 times a year performed 4.5 years Glare Effect NIL NIL NIL Snow Drifting Not observed Not observed Not observed Weed Cutting Once a year Once a year Once a year

Photographs of the PV systems from field visits at various locations are presented in Figure 15 - 17, namely at the North West Parkway, The Denver Federal Center and the Denver International airport with their respective solar PV systems that were studied and analyzed to identify the site conditions and other physical characteristics.

Figure 15. Solar PV system installed at North West Figure 16. Solar PV system installed at the Denver Parkway, Colorado Federal Center, Colorado

Figure 17. Solar PV system installed at the DIA, Colorado

The observations from the field visits are as follows:

• All PV systems were facing to south direction. As the flat panels are stationary and have unobstructed solar access between the hours of 9AM and 3PM, it is ideal to set the panels towards the south inclined direction.

• Corrosion was observed at the solar PV support structural at DIA. As the first row of solar energy systems is directly exposed to the highway at a close proximity, backsplash of deicing agents had led to corrosion of the steel frame work. A counter measure to mitigate this issue is placing the solar PV system further away from the highway.

• Recycled concrete was used as the base of the array system to control noxious weed. This design criterion should be practiced while setting up solar PV systems at any locations along the ROW.

• No snow drifting and depositional impacts were observed on the roadway surface. While all three sites had adequate clear zones from the shoulder edge to the closest panel.

• All three sites were controlled and monitored using the computer based operation and maintenance programs. These systems helped in monitoring the energy production, efficiency of the system and the overall health of the system. While site based O&M activities are limited to panel washing, O&M programs are used effectively to maintain the system illustrating the importance of keeping an O&M plan.

• Most of the sites were fenced for security issues to protect the PV system from theft, indicating the importance of a fenced perimeter around the PV plant to provide security and avoid vandalism or unwanted movement inside the plant premises.

• Observations from vantage points initially suggested that the glare was produced from the support structural frame work of the PV systems.

• Due to panel breakages were observed at several sites indicating a few causes such as manufacturer‘s defect, panel mishandling during construction, maintenance or lawn mowing.

The above observations will be used in the study frame work while developing the impact matrix as wells as the process flow chart to derive the desired results.

Colorado highways and solar resource potential with available ROW: Colorado‘s road transportation network is comprised of State Highways, U.S Routes and Interstate Highways. CDOT maintains 9,144 linear miles of roadway ROW (Safety, December 2013), which includes roadway surfaces, medians, shoulders, clear zones and interchange areas. The prime concentration on setting up Solar highways along the DOT‘s Right of Way have been identified as Interstate Highway I -70 East bound up to the Kansas State line and Interstate Highway I-76 up to the Nebraska State Line.

The map in Figure 18 presents the major highways in Colorado as well as the solar resource potential along with the availability of the ROW‘s with at least a minimum distance of 200 ft. from the highway.

Because of Colorado‘s unique characteristics – more than 300 days of sunshine per year; productive wind areas; locations of geothermal activity; vegetated areas with grasses, timber and crops; and mountainous areas with fast-moving streams - CDOT ROW may be well-suited to produce alternative energy like solar power (Kreminski, et al., 2011). Figure 18 also indicates the insolation levels for the entire state. It is observed that the northern areas of the CDOT Regions 3, 4, and 6 receive lesser amounts of solar insolation than region 2 and 5, but at considerably higher rates than the nationwide average.

The primary focus on studying and establishment of solar PV systems within the ROW in this research is limited towards CDOT region 4 and region 2. Inter State Highway I -70 East , I- 76 and I-25 North are presently considered as ideal locations to set up PV systems along highway ROWs. Several sites along these three highways have been studied, visited and are considered as a good potential site location for setting up Solar PV systems as these areas have more than 200 ft. of width space available in the ROW. Figure 18 shows a map with the list of potentials locations identified for this research having ROW of greater than 200 ft. across the major highways of Colorado with adequate solar resource potential.

POTENTIAL AREAS FOR SOLAR HIGHWAYS WITH ROW ≥ 200 FEET

Figure 18. List of major highways in Colorado with available ROW space and isolation level (Adapted from: Kreminski et al., 2011)

Potentials locations identified along Colorado Highways: The areas highlighted in red in the map of Figure 19 indicate the potential areas for solar highways along the ROW. These areas have been recommended based on the availability of more than 200 ft. of ROW on either side of the roadway to counter the impacts that have been identified in this document (iTouchmap.com, 2014). The site locations with their respective coordinates have been provided in Table 8.

Table 8: Latitude & Longitude coordinates for the potential sites identified along Colorado Highways

Site Site Reference/Location Latitude & Longitude Coordinates 1 Colorado Springs, I-25 North Bound - Exit 134 38.757779,-104.764627 2 Elbert, Colorado, I-70 East Bound Near MP-354 39.274909,-103.739994 3 Elbert, Colorado, I-70 East Bound Near MP-358 39.273925,-103.735134 4 Morgan, Colorado I-76 Near MP-76 40.267146,-103.719167

SITE - 4

SITE - 3 c SITE - 2 v c SITE - 1 v 1 c v

Figure 19. Identified locations along the highways of Colorado (Adapted from: CDOT maps, 2013)

Selection of Site location

For selecting the right site location a qualitative method has been chosen as an appropriate approach. With qualitative study, the research relies on a combination of participant observation, interviews, and historical research for small sample of data that considers a broad range of interconnected processes or causes. The objective of this section is to select the right site location for setting up a solar PV system from the previously identified four locations along the ROW. A sequential step is used to build the table and compare the results. The mathematical model for this qualitative method approach is given below: 풏

푺 = (푲풊 푿 풔풊) (Equation- 1)

풊

Where: i = Number of factors considered for analysis S = Calculated score K = Individual weight of allocated factor s = Score allocated after assessment

Following are the steps:

STEP-1: List all the important factors that have an impact.

STEP-2: Assign appropriate weights (between 0 and 1) to each factor based on the relative

importance.

STEP-3: Assign a score (between 0 and 100) for each location with respect to each factor

identified in Step 1.

STEP-4: Compute the weighted score for each factor by multiplying its weight with the

corresponding score (which were assigned at steps 2 and 3, respectively).

STEP-5: Compute the sum of the weighted scores for each location and select the location with

the highest score

Approach: Four site locations have been selected based on the site survey‘s considering the land availability within the ROW. The first three sites were identified along interstate I-70 East bound, and the fourth site was identified along interstate I-76 West bound. The factors applicable to ROW features, the solar irradiance, snow fences and appropriate soil conditions are considered for this evaluation. The scoring matrix is composed of individual categories with 100 being the maximum score assigned that would make appropriate site conditions a feasible location to set up solar PV systems. The weights allocated for this evaluation are based on the site surveys conducted at these individual locations and from the inputs gathered from industry experts and CDOT maintenance, safety and operations officials. The total summary of this qualitative method approach with the appropriate factors considered for this evaluation have been detailed in the Table 9.

Table 9: Summary of the qualitative method approach with factors considered for evaluation

Locations Site-1 Site-2 Site-3 Site-4 Factors Weight I-25 Near Exit 134 I-70 Near MP -354 I-70 Near MP-358 I-76 Near MP-76

s S s S s S s S

ROW features a. Available space 0.10 100 10 100 10 100 10 100 10 b. South orientation on the panel 0.20 90 18 90 18 95 19 65 13 c. Terrain Slope 0.07 75 5.25 80 5.6 100 7 85 5.95 d. Areas for access roads 0.08 80 6.4 75 6 80 6.4 75 6 e. Low lying land compared to 0.05 85 4.25 85 4.25 87 4.35 80 4 the elevation on the highway f. Flat land availability 0.15 80 12 85 12.75 87 13.05 78 11.7 g. Presence of a near by water 0.05 75 3.75 80 4 95 4.75 90 4.5 body/ structure/utility Solar irradiance 0.12 93 11.16 100 12 100 12 90 10.8 Living Snow Fence 0.08 65 5.2 65 5.2 95 7.6 65 5.2 Appropriate soil condition 0.1 75 7.5 75 7.5 70 7 70 7 TOTAL 1.00 818 83.51 835 85.3 909 91.15 798 78.15 The highest weightages have been allocated to the factors related to the total available space and south orientation direction on the panels. They constitute to thirty percent of the evaluation assessment, as these two factors are the most critically perceived for a proper site selection, Other factors have been assigned appropriate weightages based on judgmental instincts as well as information collected from the research assessment.

Technique: Based on the findings of the individual site conditions and from other references used for evaluating the site, the appropriate scores have been allocated. The weight factor for the site locations have been multiplied by their corresponding scores and the total score for the individual site have been calculated. The evaluation assessments for this qualitative method are as follows:

Close proximity to the highway with at least thirty feet of clear zone distance from the shoulder of the highway has been identified at all the four locations. While all the sites maintain a high average solar irradiance, higher scores have been allocated based on the region of the identified sites, indicating that sites 1 and 4 fall under a different region with solar irradiance rage of 4.5 to 5 kWh/m2/day when compared to site 2 and 3 with a solar irradiance range of 5 to 5.5 kWh/m2/day. Minimum area requirements of ROW land of more than 200 ft. width are observed. However, greater scores have been allocated to sites with a greater width of 200 ft. Flat terrains at the site locations have been observed, indicating lesser shadow effects from other panels when placed in strings. Higher weightage score have been assigned to sites south facing orientation, a possible zigzag curved terrain that can reduce shading effects from row of solar panels to the other, and the terrain of the site with either being purely flat or sloped.

Results: From this analysis, it has been observed that out of the four possible potential sites, site 3 near Mile Post 358 at Elbert, Colorado along Interstate -70 East bound had the maximum total score making it the first priority to set up a solar PV system. The conditions were found to be feasible and appropriate for setting up mid-size solar PV systems. The solar irradiance found in that area ranges between 5 to 5.5 Kwh/m2/Day that is considered to be of high range.

With a natural south facing orientation, the azimuth angle for the tilt of the solar panels remains unaltered giving maximum yield potential for power generation. ROW land with a flat terrain, it is feasible to set up the solar plant without any shadow effects from adjacent panels, thus making it the best site location among the 4 choices identified.

Solar irradiation at the proposed site near Mile Post 358, Elbert, CO

It is important that solar radiation levels are to be calculated, in order to assess appropriate site conditions that exhibit adequate level of radiation before setting up the solar PV system. This irradiance varies throughout the year depending on the seasons. Several software tools such as the NASA Surface meteorology and Solar Energy and the NREL-PVWatts were used to determine the insolation and radiation levels for the particular site at Mile Post 358 at Elbert, Colorado (Stackhouse, 2014). Table 10 summarizes the average the solar radiation for the selected site (NREL, 2012).

Table 10: Monthly break up of average solar radiation at proposed site (Source: NREL, 2012) Lat 39.275 Solar radiation Lon -103.737 (kWh/m2/day) January 4.66 February 4.80 March 5.52 April 6.03 May 6.09 June 6.23 July 6.38 August 6.33 September 6.31 October 5.87 November 4.45 December 4.27 Average 5.57

As shown in Table 10, the average solar radiation levels are more than 6 kWh/m2/day during the months of April to September. The summer season in this region receives higher daylight hours than the other months thereby producing high insolation and radiation levels. The US Environmental Protection Agency in regard to PV solar energy generation potential states that any location in Colorado with solar radiation of greater than 5 to 6 kWh/m2/day has been deemed good and recommended for PV solar energy generation (NSCEP, 2009). With an average solar radiation of 5.57 kWh/m2/day for the site at Mile Post 358 at Elbert, Colorado, it can be considered as a suitable site for setting up a solar PV system.

Technical details and assumptions for solar PV site installation

To perform glare analysis at the site located near Mile Post 358 at Elbert, Colorado preliminary judgments and certain assumptions on the probable solar PV system will be required to be taken into consideration to perform the glare analysis. Assumptions include the annual production capacity, panel type with capacity and the ground levels. From the site survey‘s, area measurements of the site have been recorded. The distance from the shoulder to the end of ROW was calculated to be approximately 328 ft. and the length available was approximately 1072 ft. These data can be used for manual calculation to determine the capacity of the plant and the total number of panels required for installation.

As per NREL‘s land use requirements for installing solar power plants in the United States, with an 8.07 acre land availability, a solar PV system with a capacity up to 20 MW could be installed (Ong, Campbell, Denholm, Margolis, & Heath, 2013). From the available area at the site, it is suggested that a 5 MW solar plant with fixed axis can be installed. The technical details of the solar PV system installation along with the assumptions considered have been captured in the Table 11 and the sample site layout for this proposed site is provided in Figure 23.

Table 11: Technical assumptions at the proposed site at Elbert, CO

DESCRIPTION DATA Available Length 1072 ft. Available Width 328 ft. Total available area in acre‘s 8.07 acres Approximate capacity of the plant installed Between 1- 20 MW Capacity of the plant assumed 5000 KW Annual Production 7500000 KWh Installation Base Ground / Pole mount Installation Type Fixed Axis – Fabricated aluminum frames PV Panel Type Sharp NU-U240F2 PV panels (SHARP & ELECTRONICS CORPORATION, 2010) Panel Numbers Approx. 12,500 panels Inverter Type Xantrex GT100 and GT250 Grid Tie solar inverters Ground Level All coordinates at fixed ground level Latitude/ Longitude Coordinates 39.27485, -103.73724; 39.27442, -103.73309 (iTouchmap.com, 2014) 39.27363, -103.73311; 39.27419, -103.73738 Panel Facing Direction South (Barcelona-Field-Studies-Centre, 2013)

Photographs of the site visit pictures:

CDOT ROW BOUNDARY FENCE

328 Ft

Figure 20. Aerial view of the proposed site at MP-358, Elbert, CO (Source: Bing Maps, 2013)

Figure 21. Proposed site at MP-358, Elbert, CO

Figure 22. Highway I-70 alignment at proposed site near MP-358, Elbert, CO

A sample site layout for the solar highway along I-70 west ROW at the proposed site is detailed below:

Figure 23. Sketch layout of the proposed solar highway at Elbert, CO

Glare Analysis for the proposed solar site near Mile Post 358, Elbert, CO

The glare analysis for this experiment has been performed using the Solar Glare Hazard Analysis Tool (SGHAT) at the proposed site near Mile Post 358 at Elbert, Colorado. This analysis will focus on the direct reflection impacts from the solar PV site on the highway for the passing motorists and will provide a quantified assessment on the following; When and where glare will occur throughout the year for a prescribed solar installation Potential effects on the human eye at locations where glare occurs.

Key observation points have been identified for the analysis of this experiment and are shown in Figure 24.

Figure 24. Key observation points taken for evaluation at Elbert, CO (Adapted from: SGHAT software, 2012)

As shown in Figure 24, eight observation points have been identified that will have a line of sight to the solar PV system. These observation points have been strategically placed in different directions and take into consideration the distance from the plant. Four observation points were analyzed from the I-70 West direction and the remaining four observations were analyzed from the I-70 East direction at the opposite lane separated by the median (Barcelona-Field-Studies- Centre, 2013). The observation points were pinned at an approximate distance of 100 to 300 ft. from one another. The Table 12 summarizes the observations numbers along with the direction of observation towards the solar panels.

Table 12: Observation points with distance and direction of orientation at Elbert, CO (Adapted from: SGHAT software, 2012) OBSERVATION POINTS TOWARDS OBSERVATION POINTS I-70 West TOWARDS I-70 East Observation Direction Observation Direction Number of Observation Number of Observation OB -1 West bound; North Facing OB -5 East bound; North East Facing OB -2 West bound; North Facing OB -6 East bound; North East Facing OB -3 West bound; North Facing OB -7 East bound; North East Facing OB -4 West bound; North Facing OB -8 East bound; North East Facing

In order to calculate the solar glare analysis using the SGHAT software, key input information such as the orientation based on the azimuth angle, the tilt of the solar panels, and the rated power along with the latitudes and longitudes of the system location are to be entered in order to retrieve the correct analysis results (iTouchmap.com, 2014) (RREDC, 2013) (Department-UCSB, 2010). Two set of PV Array systems have been set up for this experiment to separate the strip of plant vegetation located in the middle of the ROW area. Each PV array system is installed with a capacity of 2.5 MW having a southern facing orientation with an azimuth angle of 180°. The total ground elevation is auto-calculated based on the latitude and longitude coordinates. The height above ground was considered to be three ft. as an approximation of the height of the solar panels. Coordinates for the PV Array1 & PV Array 2 are provided in the Table 13 and Table 14.

Table 13: Latitude & Longitude coordinates of the PV Array1 at Elbert, CO (Adapted from: SGHAT software, 2012) View Latitude Longitude Ground Height above Total Point (deg) (deg) Elevation (ft.) ground (ft.) elevation (ft.)

1 39.27414 -103.73751 5405.54 3 5408.54 2 39.27403 -103.73706 5404.26 3 5407.26 3 39.27395 -103.73671 5405.52 3 5408.52 4 39.27391 -103.73649 5406.48 3 5409.48 5 39.27376 -103.73539 5404.53 3 5407.53 6 39.27361 -103.73423 5405.48 3 5408.48 7 39.27356 -103.73309 5404.54 3 5407.54 8 39.27394 -103.73304 5403.4 3 5406.4 9 39.27415 -103.73531 5402.12 3 5405.12 10 39.2745 -103.73731 5401.94 3 5404.94

Table 14: Latitude & Longitude coordinates of the PV Array2 at Elbert, CO (Adapted from: SGHAT software, 2012) View Latitude Longitude Ground Height above Total Point (deg) (deg) Elevation (ft.) ground (ft.) elevation (ft.)

1 39.27489 -103.73723 5404.03 3 5407.03 2 39.27481 -103.73628 5402.76 3 5405.76 3 39.2747 -103.7351 5405.33 3 5408.33 4 39.27459 -103.73412 5406.99 3 5409.99 5 39.27447 -103.73302 5406.99 3 5409.99 6 39.27409 -103.73305 5402.96 3 5405.96 7 39.27417 -103.73418 5402.01 3 5405.01 8 39.27426 -103.73518 5401.55 3 5404.55 9 39.27444 -103.73631 5402.93 3 5405.93 10 39.27462 -103.73729 5403.24 3 5406.24

It was observed that all eight observation points would influence a potential for temporary after damage and several of the observation points would have direct glare impacts from the solar PV system on the nearby I-70 Highway traffic corridors. The time for occurrence is in the evening hours from around 18:00 to 18:15 from the months of May to August and occasionally during the morning hours around 06:00 at certain observation points. A sample of the glare analysis from observation point 2 when analyzing the PV Array System 2 is provided in Figure 25 to indicate the time for the glare occurrence during 2014.

Figure 25. SGHAT analysis sample for proposed site at Elbert, CO (Adapted from: SGHAT software, 2012)

In summary a possibility of low glare potential has been identified at the present site. The level potential for glare damage will require several other factors to be considered such as the impact either at a stationary phase or while traveling at a vehicle during the impact with a corresponding speed of the vehicle movement as well as the height of the vehicle. Tables 15 and 16 summarize the results obtained from the software for the glare analysis.

Table 15: SGHAT Results for Glare analysis at Elbert, CO for PV Array 1 (Adapted from: SGHAT software, 2012) RESULTS SUMMARY FOR PV ARRAY -1 Observation Status Potential Glare Damage Observation Point -1 Glare Potential for temporary after damage Observation Point -2 Glare Potential for temporary after damage Observation Point -3 Glare Potential for temporary after damage Observation Point -4 Glare Potential for temporary after damage Observation Point -5 Glare Potential for temporary after damage Observation Point -6 Glare Potential for temporary after damage Observation Point -7 Glare Potential for temporary after damage Observation Point -8 Glare Potential for temporary after damage

Table 16: SGHAT Results for Glare analysis at Elbert, CO for PV Array 2 (Adapted from: SGHAT software, 2012) RESULTS SUMMARY FOR PV ARRAY -2 Observation Status Potential Glare Damage Observation Point -1 Glare Potential for temporary after damage Observation Point -2 Glare Potential for temporary after damage Observation Point -3 Glare Potential for temporary after damage Observation Point -4 Glare Potential for temporary after damage Observation Point -5 Glare Potential for temporary after damage Observation Point -6 Glare Potential for temporary after damage Observation Point -7 Glare Potential for temporary after damage Observation Point -8 No Glare -

Even small shadows, such as the shadow of a single branch of a leafless tree, can significantly reduce the output power of a solar module. It is also recommended that the PV site is always kept free of vegetation. Proper spacing (packing factor, which is the ratio of available space to used space, of 1.5 to 2.5 is recommended) between the array string rows helps in lowering shading effects and enhancing power generation. A packing factor of 1.66 was calculated for this site indicating a good recommendation of adequate spacing provided in the PV system.

Impact of glare to a driver Results from the glare analysis experiment indicated a low glare potential on most of the observation points. Although the effect of the glare seems to be low, there is still an uncertainty towards the impact of the glare i.e. its severity. As the site is located at a close approximate to the highway, most of the people who get affected by the glare would be the driving motorist travelling at a speed. In order to determine the impact of the glare severity, a time history of exposure is considered.

Standard exposure time for glare study was 0.15 seconds and a time history with this exposure time was set as one of the axis. Categorical scores had been allocated to the other axis with a score of 5 for any observation with a low potential, a score of 10 for potential glare and a maximum of 15 for a high potential glare. Since none of the observation points exhibited a high potential glare, the score of 15 was not displayed in the time history graph. The sequence of all the observation points with the relevant scores at their appropriate times had been plotted in the graph to derive the time history as shown in Figure 26.

Figure 26. Time history of the glare analysis at proposed site near MP-358, Elbert, CO In Figure 26, assuming that the traveling speed of the motorist is 75 miles per hour on the Interstate highway and with an exposure time of 0.15 seconds for every observation, the time history graph shows the highest peak observations are formed between the third and fourth time frame with a total exposure time of 0.45 seconds. As a result, the maximum distance that can be covered at that with the respective constant speed was calculated as 15.08 meters, indicating that the driving motorists traveling in the highway across all the observation points would experience a maximum glare for duration of 0.45 seconds for an approximate distance of 15.08 meters.

Calculating the Risk Priority Number by the FMEA for glare Based on the data collected from the experimentation section on glare, the Risk Priority Number (RPN) can be calculated. This analysis is based on the judgment to rate each potential problem according to three rating scales namely severity, occurrence and detection.

Severity, which rates the severity of the potential effect of the failure. Occurrence, which rates the likelihood that the failure will occur. Detection, which rates the likelihood that the problem will be detected before it reaches the end-user/customer.

For the glare analysis assessment on the RPN, the rating scales used for this analysis considers a range from 1 to 10, with the higher number representing the higher seriousness or risk. For example, on a ten point Occurrence scale, 10 indicate that the failure is very likely to occur and is worse than 1, which indicates that the failure is very unlikely to occur. Based on the ratings been assigned, the RPN for each issue is calculated by multiplying Severity, Occurrence and Detection

(Equation- 2)

The allocated score for the rating has been assigned as follows:

Severity Occurrence Detection 6 5 8

The total RPN for this analysis was calculated as 240. Considering the rating of 1 being low, 5 being medium and 10 being high, a rating of 6 was allocated to severity based on the data analysis in the experimentation for glare. The site exhibited glare impacts ranging from only a low to a potential temporary after damage with exposure time of 0.15 seconds. Since none of the observation points has displayed a high impact of temporary after damage, the severity can be considered above average medium and as a result was allocated a score of 6 out of 10.

A rating of 5 was allocated to occurrence which indicated a medium or average as it was found that the glare occurrence is a seasonal time based that occurs only during four months averaging between 25- 35 minutes indicating the probability to be medium when calculated on a yearly basis. A high rating of 8 was allocated to detection as the chances of the solar glare to get detected before being observed by the driving motorists‘ is presently not possible. Without the proper mitigation measures, the chances of the glare not to be detected us high. With the development of the glare analysis as a new approach the rating is presently being considered as a high risk factor.

Mitigation/ Corrective actions to reduce the RPN number: As per the FMEA model, it is highly recommended that the RPN number be reduced to lesser than or equal to 100 to decrease the amount of associated risk involved with glare. This can be achieved by performing corrective actions to reduce the glare impact. Few of the corrective actions that can reduce the RPN are given below:

The use of anti-reflective coatings in solar panels will reduce the reflectivity from 4% to 2% there by reducing the severity directly by 50%. As a result the severity rating can be reduced from a previous rating of 6 to 3, thereby revising the previous RPN to a new RPN of 120. As the recommended RPN must be lesser or equal to 100, it is important to perform further corrective actions and reduce the allocated score on occurrence and detection. Performing a glare impact assessment on a particular site before the project development as well as placing the solar PV system on a south facing orientation, on the south side of the East-West approach highway, away from the line of sight from the highway will ensure driving motorists‘ will not get affected by any glare from the solar panels. Performing the mitigation can reduce the occurrence from a previous rating of 5 to 1 as no glare will be observed. This change revises the existing RPN further reducing it to 24.With the revised RPN being less than 100, it suggested to stop further actions. After performing adequate glare analysis for the particular site, creating a public awareness to the driving motorists‘ by displaying proper road signage will help in reducing the detection factor there by making the motorists‘ more alert and responsive whenever they encounter glare from the PV system.

Risk Impact Methodology for Impact matrix

As systems engineering deals with work-processes and tools to handle projects, and it overlaps with both technical and human-centered disciplines such as industrial engineering, control engineering, project management and organizational studies, this process can create a structure for approaching design problems and identifying stream of requirements by design effort (Dadpouri & Nunna, 2011). The prime structure towards the decision making process in the risk impact analysis has been categorized into four different quadrants with affiliation towards impact and the probability of occurrence. The four square method is the technique used in this study to assess the evaluation of risk and likelihood as either high or low. The values are placed in the quadrant depending upon the likelihood and severity assessment (RIT-University, 2011). Probable mitigation strategies have been identified based on the evaluation of the risk and the particular quadrant identified. The structure of the four square method technique with the mitigation concept adopted in this research technique is given in Figure 27.

HIGH Impact is high Probability is high and but probability is low Impact is high

IMPA CT Create plans to deal with the Reduce potential impact

Probability is low and impact is low Probability is high but impact is low

LOW Do nothing Exercise tolerance

LOW HIGH PROBABILITY OF OCCURRENCE

Figure 27. Four square method risk quadrant (Adapted from: RIT University, 2011)

Chapter 5 – Results

The development of solar highways should undergo a systematic process covering all phases of the lifecycle of the project starting with the planning stage until the final operations stage. This systematic process has been described through a process flow chart capturing all the necessary details and might be helpful to guide the selection process and enable the user to use a mitigation measure. A PV system impact analysis and selection process is shown through the flow chart in Figure 28 and is accompanied by the major impact factors. A pathway is derived which considers various steps, accounting for the level and impact of these factors. Mitigation is suggested to address the unfavorable conditions.

The process planning chart has been developed in such a manner that all the factors have been addressed by the responsible concerned authorities at the necessary stage before progressing towards the next stage of the project life cycle. Factors such as the land availability, ROW characteristics, panel inclination, glare analysis, snow drifting and Operation & Maintenance have been identified in this process planning chart.

Decision models in the flow chart such as process flow, alternate process, predefined process and decision process have been identified and implemented to ensure smooth transition from one stage of the life cycle to the other.

The mitigation measures involve the action to be taken for each of the identified factors and the particular life cycle stage, thereby providing a guideline towards the selection process while setting up PV systems along the ROW of a highway. The identified mitigation measures have been sourced from several literature assessments, site and field visits and interviews with the key experts in the relative field to provide the best and most accurate decision making actions to be taken while setting up solar PV systems.

With several stake holders responsible for the proper functionality of the PV systems array, it is also important to identify which stake holder is responsible for the mitigation measure at the right life cycle stage. The depicted control flow chart also identifies the key stake holders responsible for performing their activities and ensuring the correct measures be taken for a smooth process. Service levels have been identified at the various stages of the project life cycle and would be the most appropriate to be followed.

The Figure 28 depicts the process flowchart with the life cycle stages for setting up solar PV systems in ROW‘s along the highways.

FACTORS PLANNING DEVELOP DESIGN IMPLEMENT OPERATE ACTION TO BE TAKEN RESPONSIBILITY START

Land land use Availability restriction SOLAR SERVICE PROVIDER IN CDOT Coordinate with CDOT ; check for CO-ORDINATION solar radiance at site WITH THE MODERATOR Environ Environmental Avoid Wet land/ Meet NEPA impact Compliance requirement NO Assesment Archealogical (EIA) is required sites/Animal habitat YES East-west highway is Select alernate Panel Panels better with ROW on land with inclined to Inclination preference to south side South? NO south inclination SOLAR SERVICE YES PROVIDER Site PV ROW >200 ft is ROW sytem better with sufficient Clear Zone > 30 ft NO behind guardrail or clear zone and breakaway s maintanance space YES Panels facing away

Glare & Potential use from any visible anti-reflective Glint Glare YES point of any road is Occurance coating on PV modules better INSTALLER & NO Install at a Road in the winter EQUIPMENT distance MANUFACTURER Snow High Snow 15times the wind direction will Drifting Drifting Area fence height have least snow YES away from drifting problem NO the roadway

O&M, SCADA Turnkey package Panel washing, Continiously monitoring after weed removal monitor the including O&M will CONSULTING O&M implementation and System performance check reduce the risk of O&M AGENCY Maintenance STOP Figure 28. Process control chart with life cycle stages for setting up Solar PV systems in ROW‘s along Highways

In addition to the process control chart, an impact matrix has been developed that captures the impact parameters along with the potential impacts.

Table 17: Impact matrix with risk factors and the probability of occurrence

CDOT Probability Risk CDOT Sr.NO Impact CDOT Potential Impacts of Factor Concern Parameters Occurrence

Sunlight reflecting off of the solar panels may affect 1 Glare and Glint driving safety along roadways by short periods of High Low Yes intense light impacting driver sight. Solar array systems can increase driver fatalities by 2 Collision safety High Low Yes introducing new structures within the Clear Zone Area Array systems could affect baseline condition snow Snow drifting 3 drifting and depositional patterns thus increasing ice High Medium Yes and deposition and snow build up on the roadway. Magnesium chloride application onto the roadway may drift onto solar array panels that could create structure Chemical 4 rusting and electrical connection problems. This would High Medium Yes Deicing Agents lead to increased solar array maintenance activities on the CDOT ROW Solar Array Solar array panels will need security fencing to reduce 5 Security High Medium No the potential for being vandalized Fencing Construction and Operation & Maintenance 6 Site Safety representatives are at risk working within the right of Medium High Yes way area or represent potential risk to drivers/ visitors Solar Panels Access to solar array systems from roadway shoulder 7 access for Medium High Yes could impact driver and maintenance personnel safety maintenance Ground disruption and equipment can cause the 8 Noxious Weeds introduction of noxious weeds that can cause ecological Medium Medium Yes and aesthetic impacts Solar array panels and overall structure could be Solar Array damaged by high winds and could potentially entering 9 Structure Medium Low No the roadway area or may require frequent maintenance Integrity on the ROW Construction vehicles that access the solar areas from Solar Array the roadway shoulder area may cause a safety concern 10 Medium Low Yes Access to oncoming traffic due to the parked cars along the shoulder and right of way Solar array systems may catch the sudden attention of Driver 11 drivers along interstates and state highways. This Low High Yes Awareness change in driver awareness may be a safety issue. Array system fencing will require an alteration in mowing operations outside the array fencing area. Right of Way Restricted access must be provided for mowing in clear 12 Low High Yes Mowing zone in some areas, maintenance concerns near security fencing and to outside parties who perform mowing activities within the right of way

The impact matrix in the form of a template lists the key risk parameters in the first column, followed by the description of the potential impact in the second column. The risk factors and the probability of occurrence for the individual impact parameters have been identified and classified as low, medium or high. These risk factors were identified through literature assessments, conversations with professionals understanding the solar array system as well as CDOT representatives. Some of the risk factors are time sensitive (day, seasonal etc.), while others are continuous throughout the day. For non-time sensitive factors, which are either critical by nature or imposed by some governmental laws, the probability of occurrence will be assigned based upon the best judgment and information gained from the literature assessment and other studies. From Table 17 of the Impact matrix, it can be observed that main impact parameters have been identified along with their risk factors and the probability of occurrence. While the identified parameters are not exhaustive, it can be assumed that the same would be the major concerns for all DOTs while developing such PV systems in the ROW‘s along the highways. Having identified the parameters, the possible mitigation measures and the design and siting criteria to be proposed to counter these factors are detailed in Table 19. The references used to recommend the mitigation and the design/siting criteria are shown in Table 18.

Table 18: References used in recommending the mitigation and siting criteria

Impact Parameters References used in recommending mitigation & siting criteria Site Surveys, Caltrans project, Glare analysis experimentation Glare and Glint & literature review on glare and glint Driver Awareness Literature review on Massachusetts State Route - MassDOT Interviews with CDOT officials on addressing highway Site Safety operations & maintenance challenges Literature review on AASHTO design requirements, Steel Rail Collision safety guard rails and interviews with CDOT officials. Snow drifting and deposition Literature review on snow drifting. Solar Array Structure Literature review on addressing solar PV systems operations & Integrity maintenance, site surveys at DFC and DIA Chemical Deicing Agents Interviews with CDOT maintenance crew and literature reviews Solar Array Access Interviews with CDOT safety and maintenance crew Right of Way Mowing Interviews with CDOT maintenance crew and literature reviews Solar Array Security Fencing Literature reviews on existing solar highways Solar Panels access for Experimentation on site locations and interviews with CDOT maintenance personnel. Noxious Weeds Site surveys NWP, DFC, DIA and CDOT manuals

Table 19: Impact matrix with mitigation measures and siting criteria

CDOT Sr.NO Impact Mitigation Design /siting Criteria Parameters

Maintain the tilt angle of panels at 18°-36°. Use Glare and Perform glint/glare studies through a site 1 anti-reflective panels and dull polishing on Glint specific study structures. Guardrail placed according to AASHTO Solar array systems could be protected by the requirements and MDS design experiments. placement of guardrails along the road Collision Incorporate berms to deflect on coming vehicles. 2 shoulder. The solar array distance from the safety Place solar PV systems behind guard rails, crash roadway could be increased beyond the 30 foot cushions and away from breakaway structures clear zone. and utility lines. For a particular height of a snow fence the Array systems must be located at least 35-50 accumulated snow gets collected over a distance Snow drifting feet from the roadway surface within the clear 3 of 35 times the snow fence height. Only beyond and deposition zone area. Avoid placement in known high this length should the system be located from the drifting area. solar fence.

Chemical Select structural materials resistant to corrosion Apply coatings such as paint, electro-coating etc. 4 Deicing such as stainless steel and ensure electrical to all exposed structures to prevent corrosion. Agents connections are protected. Perform regular maintenance on the structures. Chain link fencing should be at least 8 feet high with barbed or razor wire on top. Chain linked Solar Array Construct chain link fencing around solar array fencing or reinforced fencing should be installed 5 Security system to prevent vandalism at the top of the cut slopes as well as anti-theft Fencing bolts, and perimeter security lighting and video monitoring. Prepare Site Safety and Health Plan and 6 Site Safety - conduct tailgate safety meetings Look for alternative routes for array Solar Panels maintenance via frontage or adjacent roads; Look for alternative access locations via frontage 7 access for evaluate potential of developing temporary roads for solar array siting maintenance maintenance road Monitor vegetation growth during solar array Follow DOT specifications where noxious free- Noxious and right of way maintenance and develop 8 certified materials are used for erosion control. Weeds Noxious Weed Plan. Use recycled concrete to Plant native grass species in disrupted areas. control noxious weed growth. Include barbed wire or reinforced fencing at the Solar Array Solar array system structure and associated top of the cut slopes as well as anti-theft bolts, 9 Structure security fencing will be designed to withstand and perimeter security lighting and video Integrity high winds monitoring. The construction project will need to coordinate Solar Array with DOT Maintenance Representatives for 10 - Access traffic control procedures to include signage and cones.

Place signage along the road warning the Driver 11 traveling public about upcoming solar array - Awareness systems. Coordinate mowing expectation with DOT Right of Way ROW and maintenance representatives; Ensure vegetation growth does not impact solar 12 Mowing mowing in clear zone is avoided 20 feet from panel performance due to vegetative height shoulder edge in short grass prairie ecosystems

Chapter 6 – Conclusions & Recommendations

The undertaken research indicates that glare, snow drifting, tumble weeds, access road and site safety are few of the major impacts factors that have been identified in the PV array systems deployment along the ROWs.

The glare from PV system (PV panels or support structure) is a concern and has a potential of causing temporary blindness to the motorists. A thorough glare analysis is needed to assess the amount of glare thereby taking all necessary mitigation measures. Site assessments with all physical characteristics such as slope, elevation and distance from the ROW must be considered in order to avoid possible glare from the PV systems to the passing motorists. The solar panels when placed on the south side of a East-West approach highway is the best option to mitigate from the passing motorists‘ as they are placed away from the line of sight.

As PV systems placed in the ROW will have close proximity to the highway, constructing security fences around the site perimeter can a safety net to the PV system. These security fences will act as a barrier to protect the site from theft, vandalism and can protect the integrity of the panels without any damage. From the motorists‘ point of view, the security fences can act as a blockade reducing any direct impact or collision with the PV system. The security fences will also act as a snow fence, break down the wind speed, depositing the snow within a few feet thereby preventing the snow from reaching to the highway.

Locating PV systems either behind the existing guard rail or in an isolated area away from the highway are mitigations that can lower the impacts on safety and can provide a better utilization of the ROW by offering safer travel to the public. Such locations need to be considered before looking for other areas. Construction of new guiderails alongside the roadway for implementing PV systems is not advisable without compromising driver‘s safety. Setting up guard rails in front of PV systems will act as a layer of protection for the PV system and simultaneously help the driving motorists‘ to keep their vehicles from straying into dangerous or off-limits areas.

Snow removal along the highways can be countered by using snow plowing machines and by the use of magnesium chloride that will act as deicing agents. Maintenance of snow removal

68 and mowing concerns should also be addressed with all mitigations when developments of new utilities are being set up in the ROW that could hinder road repair and maintenance activities.

Tumble weed accumulation could reach to the road by piling up on the PV systems and cause nuisance to the motorists and add extra work to the DOT maintenance. Free movement of tumble weeds on the highway also causes heavy nuisance to the driving motorists as a driving distraction and tendencies to scratch the moving vehicles.

Engineering controls necessary to address driver safety concerns must be addressed with proper solar array height, orientation, tilt angles and location with the clear zone area are critical to highway safety.

Slow speed PV maintenance vehicles could be a challenge for traffic flow and should not get access to the ROW from the freeway. Alternatives towards accessing the system like setting up service roads from the exit, closest to the project location or using secondary roads from the back side of the PV plant can be possible mitigations.

Solar PV plants do not require maintenance at frequent intervals and can be limited to only once or twice a year. With such low hindrances, DOT‘s can escort the maintenance crew. Proper coordination with the DOT, can ensure performance of O&M operations in controlled setting without hampering the highway traffic flow.

Impact studies for setting up solar PV systems along the highway ROW is very crucial and need to be enforced. The factors and their impacts vary on specific technology, geographic locations, road condition and orientations, and local environment. Geographic locations for the PV systems include the solar isolation evaluation, land topography, terrain, prevailing wind velocity, snow accumulation and potential snow transport. Road conditions and orientations include the physical characteristics such as slope, elevation, road curves, presence nearby of water bodies and the degree of road inclination. Local environment include storm water management, community awareness, vegetation, noxious weeds and sensitive environments. The developed impact matrix lists all the major factors and proposes the possible mitigation measures with probable design and siting criteria to ensure best practices. The use of the

impact matrix and the process flow chart will help to navigate the site selection process and minimizing the impacts.

The findings of this research could be used as a guidance document to all DOT management and their regional personnel to deploy potential solar array installations within their ROW areas. This document has detailed the potential impacts and mitigation strategies that must be addressed by all DOT‘s or alternative energy investors who will use the ROW for electrical generation.

These guidelines will help to develop a new foundation for a decision making process to aid in ROW management. This project will ultimately result in the better utilization of the ROW with safer protection of the traveling public and environment while maintaining efficient ROW operation and maintenance actions.

Future Research:

The risk analysis technique adopted in this research had only used the FMEA analysis partially limiting to the glare analysis assessment and not the entire research, due to the lack of probability data. It is plausible to perform future studies to obtain accurate data for all the identified impacts through further experimentation and research.

The process flow chart and the impact matrix created in the results section are based on the occurrence of probability and impact factors that have been analyzed through certain factors that have had similar incidents recorded in the past through case studies, literature reviews and personal interviews with key personnel having the domain knowledge. These factors are estimates which could be improved.

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APPENDICES

APPENDIX –A

SGHAT analysis results for Colorado State University - Pueblo

Figure A 2 - Results from OB-3 Figure A 1 - Results from OB-2

Figure A 3 - Results from OB-5 Figure A 4- Results from OB-6

Figure A 5- Results from OB-7 Figure A 6 - Results from OB-8

APPENDIX –B

SGHAT analysis for the proposed solar site near Mile Post 358, Elbert, CO

Figure B 1 - Results from OB-1 Figure B 2 - Results from OB-2

Figure B 3 - Results from OB-3 Figure B 4 - Results from OB-4

Figure B 5 - Results from OB-5 Figure B 6 - Results from OB-6

Figure B 7 - Results from OB-7 Figure B 8 - Results from OB-8

APPENDIX –C

Field Study Reports

Site Survey on 12th December 2012 by Art Hirsch & Navaneeth K.Ramesh

LOCATION 1: The North West Parkway, 3701 Broomfield, Colorado - 80023

Name of the site coordinator: Mr. Mark Shotkoski, Director of Engineering & Maintenance

Site over View:

NW parkway maintains the highway and has a lease agreement for 99 years. The commercial Operation Date of the Highway was started on 2003 and has been on operation for the last 9 years. They are setting up Wind and Solar energy projects along their ROW with focus on environmental and renewable clean energy.

Private Energy supplier Xcel energy is the presently the power supplier for the North West Parkway. Xcel Energy has offered rebate to NW parkway energy consumption when it develops and supplies clean energy from its ROW with a primarily condition that not more than 10% of clean energy must be produced of what every individual meter was drawing.

As a result NW Parkway had decided to set up small solar plants along its ROW for the generation of clean power that is metered and can be used for supplying power to the roadway lighting, deck lights and traffic lights along each section. Solar Plants on the NWP ROW have been in place since June 2011 and have operating for the last 2.5 years.

Figure C 1 - Solar PV system at North West Parkway

7 Sites have been identified for the installation of Solar PV systems. Each system generates 10 Kw; totaling to a total of 63 Kw of clean energy generated from all the 7 sites. NWP‘s ROW is 350 ft. wide along both sides. The clear zone considered for suitable set up of the PV plant is 30 ft. from the shoulder of the highway. The shoulder edge to the panel distance was set up at approximately 35 ft. distance. Building permit for suitable construction out of the clear zone is to be obtained from the local county. Slopes were set up on the identified sides of the PV system for easy installation. The slope side ratio is approximately 3:1 maximum from the road way. Setting up PV systems on slopes provides assistance in cleaning the panels during O&M. Operation & Maintenance on the solar panels is almost zero. No O&M activity has been performed till date. Advisable O&M practice: Water-Brush-Water. Water the panels to remove the dirt/dust in the panels followed by a light brush for thorough clean and pour water again. It was observed that the efficiency of the panels do not improve after the panel wash. Web based systems/software‘s are available to check and recorded the daily energy production. That was one instance where local rodents like (mice) had chewed the conduit –which had to be repaired or replaced. Advisable not to directly burry the cables directly underground but rather use a conduit. Chemical Deicers i.e. magnesium chloride (MgCl) are being used to dissolve the snow. The salt cause‘s pulverization and the sand give traction to remove the ice and make the highway safe for operation. No films/ sheets are caused on the highway sides due to any chemical effect. Chances of splash back effects of the chemical are possible. Geotech studies were performed onsite before plant development. The tilting angle was approximately set up at 18 – 24 degrees bases on the location. No Glare shadow effect has been observed from the solar panels. Glare effects from Aluminum sign boards were greater than the glare from solar panels.

Advisable to set up PV systems along the ROW which do not have bends on the highway. Setting up PV systems parallel to the roads/ highway is most feasible The front side of the panels has an approximate height of 5 ft. from the ground and the back portion of the panel has a height of approximately 10ft from the ground. These distances vary from every site based on the tilting angle. Few snow fences have been placed along the ROW to prevent from snow drifting. Setting up of the snow fence has substantially prevented the snow from drifting. Typical wind direction is on the North-West direction. No evidence on any micro-climate formation. No presence of noxious weed. The ROW landscaping maintenance is done once a year. There has been no animal concentration around the panels as the PV system is fence protected.

LOCATION 2: Solar Power Plant adjacent to the Water Treatment Plant, Highway US-40, Golden, Colorado

A Private owned plant operated and used to carter to the power requirements for the adjacent Water Treatment Plant.

OBSERVATIONS: The PV system at the water treatment plant is based on a tracking principle. Fenced PV plant. The area of the plant facing the highway had an artificial slope to give height to the plant and had two barbed fences for protection. All the inverters, step up transformers for the solar plant were placed a protected closed cabinet. Approach road available to enter the plant premises with parking facility. Transmission towers of approx. 11 Kv size present to transmitting power across the Highway from the power plant.

Figure C 2 - Solar PV system at US-40, Golden, Co

LOCATION 3: Solar Power Plant at the Denver Federal Center, Denver, Colorado

Name of the site coordinator: Mr. Douglas B. Porter, Regional Chief Engineer, G.S.A

The site visited was a fixed PV plant of capacity 1.17 MW in a 7 acre spear area that gave 14-15% efficiency. Contract signed with Xcel Energy in Jan 2008 for credit benefit. Sun Edission offered the contract at to execute the project for Denver Federal Center. The Solar Plant is located along the East West direction Alignment and the panels were facing the south direction. Geotechnical analysis was performed at each and every proposed site for the solar PV system and necessary corrosive effects were also taken into consideration. The 1.17 MW plants consist of approx. 6000 No. of solar PV panels connected via 16 strings through 54 lines into 2 No. inverters. The site had nasty weeds that had to be removed. A temporary irrigation system was used to remove the weeds. The DFC solar panel operates better in the morning than in the afternoon due to clearer skies with panels inclined at a 20° slope. No additional O&M is required for the snow shedding in the solar panels. Scheduled Maintenance take place twice a year. Approximate charges for cleaning the panels are $8000 for cleaning.

As Colorado receives rainfall at least twice a year, the rain is sufficient to clean the panels. No rodents have been observed in the solar PV plant. Presence of Bird excreta found in few solar panels. It was observed that the panels are not very reflective and does give any glare effect also the panels along the Highway does not have any impact with the highway.

LOCATION 4: I-70 West near Mile post 352, Elbert Colorado.

Site Survey on 31th September 2013 by Dr.Ananda Paudel, Navaneeth K.Ramesh & Faruq Salawu

. The distance from the shoulder to the end of ROW fence had been measured and calculated to be approximately 143 feet. When a solar plant is set up in this location, it is likely that the panels will be facing the south direction. With panels facing the south direction, there is a high probability that the sun‘s reflection from the panels will make direct eye sight contact to the passing motorists in the highway. . The ROW area in this location is a low lying land compared to the elevation on the highway. The difference in the ground level from the shoulder to the ROW would be suitable to avoid snow deposition and snow drifting along the highway. . The soil observed in the ROW area was not dry and had no stones or pebbles indicating the presence of a water body close by or high water table content in that area. . The presence of an existing storm water drainage system indicates that the excess rain water is prevented from entering into the highways. . There has been no evidence of existing underground structures such as pipes underneath the ground. No presence of obnoxious weeds was noted in the ROW area. . The ROW area evinced grass covering the entire area till the ROW boundary fence. . The barbed wire fence was placed at an approximate height of 3-3.5ft above ground level.

LOCATION 5 : I-70 West near Mile post 354, Elbert Colorado.

. The distance from the shoulder to the end of ROW fence had been measured and calculated to be approximately 252 ft. The area had similar site conditions to that of the previous site. A parking space of 8ft adjacent to the shoulder indicated the probability of the CDOT operations and maintenance to take place at the site regularly. Large numbers of tumble weeds were observed in this site.

LOCATION 6: I-70 West near Mile post 358, Elbert Colorado.

. Among all the three different site locations, this site was the best suited to set up solar plants along the DOT‘s ROW. The distance from the shoulder to the end of ROW was calculated to be approximately 328 ft. At the half way distance in the ROW area, a layer to small plants of approximately 10-15 feet were planted along the ROW line. Considering the fact that this site had the maximum ROW area, if a solar plant is set up in this location, there would be a necessity to transplant the layer to trees and plants from one location to another. . The site had evinced evidence of animals in and around the ROW area. Animal bones and snake skins were found to indicate the presence to animals within the vicinity. . Different varieties of crops such as barley were seen to be growing in the ROW area. . The ROW also had large presence of littering and improper disposal of trash that could possibly come from the driving motorists. . A large presence of insects such as locusts and bugs were observed at the site.

CDOT ROW BOUNDARY FENCE

328 Ft

Figure C 3 - : Site location at I-70 West near Mile post 358, Elbert Colorado

The site layout for the location No. 3 has been considered for experimentation analysis. The two sections of the 164 ft. each have to merged together to form one big layout. This is possible only when the plants separating the two sections in the site are removed and replanted in a different location. Considering the fact that 328 ft. of ROW length is available, the appropriate design lay out for the solar PV systems needs to be planned with the right number of strings and appropriate spacing between them for regular )operation & Maintenance and vehicle movement. Based on the past snow accumulation data a snow fence of a suitable height will be placed in front of the ROW fence to counter snow drifting to the solar plants blowing towards the South direction. With adequate clearance from the shoulder to the solar plant, a parallel snow fence is to be placed on the opposite direction to counter snow drifting and snow accumulation from winds blowing towards the north direction. A suitable way to prevent theft and stopping animals from entering the solar plant is by constructing a safety fence. This will help the plant is terms of safety and reliability of the plant.

APPENDIX –D

Minutes of the Meeting and interviews of key personnel

Meeting -1 Meeting Date: January 7, 2013 Location: CDOT Region 1 Summit Room

Participants David Campbell – CDOT (ROW Permitting) Jered Maupin – CDOT (Maintenance) (for Michael DeLong) Richard Solomon – CDOT (Maintenance) David Ruble (Maintenance/ROW Management) James Eussen – CDOT (Environmental) Art Hirsch- (TerraLogic) Navaneetha Ramesh- (CSUP Graduate Student)

Meeting Summary

Environmental There may be wildlife attraction by the glare There may be an impact to the Migratory Bird Treaty by bird nesting in the solar frames or ground nesting birds (like borrowing owls) Grass treatment for bird migration could be impacted; no mowing of grass within 22 feet of the edge of pavement unless previously approved by CDOT. Project specific/site specific solar arrays will require a NEPA analysis. It is expected that a Categorical Exclusion (Cat Ex) would be used. CDOT Storm water Management Plan will be required by CDOT Change in vegetation allowing noxious weeds will occur; a Noxious Weed Plan will be required

Shading factor for vegetation under panels is a consideration If using a corridor based approach, it may throw the project into an Environmental Assessment due to environmental uncertainties along the corridor Would need to consider the landowners (like the US Forest Service) who may own the right of way in certain locations within the state Watershed organizations may need to be made aware of the array systems in storm water area.

Safety Glare is an issue for north-south roads; not just the panels but the frames; perhaps fixed versus tracked panels may cause more glare. No need for breakaway structures if arrays are outside the clear zone (greater than 30 feet from travel way line) If arrays are within the clear zone, guard rails and breakaway structures need to be considered Construction of arrays require a lane closure where time/seasonal restrictions imposed by CDOT. Solar array signage could be considered to avoid driver distraction Check animal-car collisions database for high wildlife areas; avoid these areas for placement. Be aware of electrical wiring and connection corrosion due to magnesium chloride road application and dispersion; corrosion of framework may also occur.

Right of Way Maintenance Snow blowing could throw snow as far as 150-200 ft. from the road; array systems could be hit by snow blowing; not a usual occurrence in the plains area (like I-70 East) Concerns about mowing near the solar array chain link security fencing by CDOT tractors; owners of array systems should ―hand mow‖ grass near fencing. Wind generally blows from north to south in Colorado.

Access to arrays for maintenance should be from a frontage road instead of directly off the interstate

Meeting – 2 CDOT Safety Engineering Group Meeting Date: January 28, 2013/2:00-3:30 Participants Arthur Hirsch (TerraLogic) Ananda Paudel (CSUP) Narvaneetha Ramesh (CSUP) Bryan Roeder (CDOT-R&D) K.C. Matthews (CDOT-Safety) Ronnie Roybal (CDOT Safety) Ken Nakao (CDOT Safety) Alisa Babler (CDOT Safety)

Meeting Summary The clear zone distance is not fixed but rather is dependent upon variables such as speed limit, slope, road curves and best professional judgment There is a recovery zone that may be within or outside of the clear zone area Placing solar arrays within a 70-75 mph interstate may represent a high risk concern; fixed objects within the right of way may cause fatalities Guardrail is a fixed object that represents a risk; the placement of guardrail to protect solar array and vehicle impacts is not necessary the best approach It is preferred that solar arrays use already existing guardrail instead of installing new guardrail CDOT management will need to justify the additional risk

The crash worthiness of the solar array system is a concern; the array system should minimize impact of the out of control-moving vehicles There will need to be safety right of way training for solar array maintenance and construction employees. It is not known if adding solar arrays statistically increase the risk of accidents or fatalities; acceptable risk levels are not well identified by CDOT. Glare off the panel is an initial concern but not a major concern; angle modification could be performed after installation if deemed a concern and glare screens implemented E-470 is already using solar PV systems in their right of way. Design considerations need to address high wind and snow loads. In regards to snow drifting, Colorado State Forest Service should be contacted about snow drifting/deposition along right of ways based upon living snow fencing applications No concerns noted about rest areas or noise wall applications.

Meeting – 3 Maintenance Meetings summary Date: 12/23/2013 Location: CDOT, Limon Maintenance Office, 450 B Ave. Limon Co. 80828 Participants: Ananda Paudel Navaneeth K. Ramesh Faruq Salawu Wayne Brown

Maintenance activities: Third party does the major construction/ CDOT does the all maintenance Maintain highway from CDOR ROW fence to fence. Fix, build fence, move, ditch repairing, and tumble weed cleaning: mowing 2-5 times a year.

Snow mowing depends upon the snow fall and duration of snowy season(0-20 times/ year) Winter road maintenance snow removal Strategy is to mow away snow and let road catch more snow. Typical Snow direction in Limon area is NNW to SSE Snow Blowing and spray system in Denver area might be of an issue. Commonly used deicers are used for snow removal. Snow is removed using plow off only (no blowing) Potential Solar Installation issues: Anything standing 3-4 ft. from ground cause snow drifting and a place for tumble weed accumulation, which could back up to road No access possible from the freeway Off ramp double back (take a ramp and use service road) might be a best possible option Cost of replacement might be an issue Traffic volume is going up and unforeseen situation might happen in future. Panels installed farther away from the highway most advisabl

APPENDIX –E

Photographs Photograph of the solar PV fixed plant along I-25 in Colorado Springs near Exit 134. The plant is fenced throughout the plant perimeter with wooden fences in the back as a measure to mitigate snow and to avoid glare reflection to the nearby neighborhood.

Figure E 1 - Solar PV system along I-25, Colorado Springs, CO

Photograph of a solar PV installed adjacent to the highway E-470, Denver, Colorado

Figure E 2 - Solar PV system along highway E-470, Denver, CO

Photograph of the 1.2 MW solar PV system installed covered with snow at the Colorado State University- Pueblo campus.

Figure E 3 - Solar PV System at Colorado State University - Pueblo, CO

Photograph of a small scale PV system at Boulder (university area), Colorado with glare effects on the panel during sun set.

Figure E 4 - Solar PV System at Boulder, CO