University of Florida Thesis Or Dissertation Formatting

ECONOMIC FEASIBILITY OF USING DC POWER IN MANUFACTURED HOMES

VENKATESH KUMANAN

A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN CONSTRUCTION MANAGEMENT

UNIVERSITY OF FLORIDA

2020

To my family and friends

ACKNOWLEDGMENTS

I want to thank my committee members, starting with Dr. Abdol R Chini, for reinstating my passion for estimation, cost analysis, and sustainable solutions for green building. To Dr. Ravi Srinivasan, inspiring me with his research works and driving me to work hard to reach great heights. Finally, Dr. Russell Walters for his constant support in the field of electricity. Without him, I guess this piece of work would not have been possible.

I want to express my gratitude to the University of Florida and M.E Rinker School of Construction Management for providing me with all the technical tools and support to carry out the research work. I am always grateful to my family and friends who have always been of immense support to me. Without them, I would not have reached this level.

TABLE OF CONTENTS

ACKNOWLEDGMENTS ...... 4

LIST OF TABLES ...... 7

LIST OF FIGURES ...... 8

LIST OF ABBREVIATIONS ...... 9

ABSTRACT ...... 11

CHAPTER

1 INTRODUCTION ...... 13

1.1 Statement of Purpose ...... 14 1.2 Objectives ...... 15 1.3 Scope of Research ...... 15 1.4 Limitations of this Study ...... 16

2 LITERATURE REVIEW ...... 17

2.1 Energy Efficient Buildings ...... 17 2.1.1 History of Energy Efficiency in Buildings ...... 17 2.1.2 Residential Energy Efficiency ...... 18 2.2 Heat Dryer ...... 19 2.3 Renewable Generation ...... 20 2.4 Energy Use of Affordable Home ...... 20 2.5 Life Cycle Affordability Costs ...... 20 2.6 Manufactured Housing ...... 21 2.7 DC vs. AC ...... 23 2.8 Three-Phase Brushless DC Permanent Magnet Motors (BDCPM) ...... 24

3 METHODOLOGY ...... 25

3.1 Home Location Selection ...... 25 3.2 Home Properties ...... 26 3.3 Appliances Selection ...... 28 3.3.1 Refrigerator ...... 29 3.3.2 Clothes Washer ...... 29 3.3.3 Clothes Dryer ...... 30 3.3.4 Dishwasher ...... 30 3.3.5 Cooktop ...... 31 3.3.6 Microwave ...... 31 3.3.7 Air Conditioner ...... 32 3.3.8 Lightning ...... 33

3.3.9 Ceiling Fan ...... 33 3.3.10 Other Miscellaneous Loads ...... 34 3.4 Photo-Voltaic System Selection ...... 35 3.5 Photo-Voltaic Life Cycle Cost Analysis ...... 36

4 RESULTS AND DISCUSSION ...... 38

4.1 Annual Energy Consumption of DC and AC Appliances ...... 38 4.2 Photo Voltaic System ...... 42 4.3 LCC Calculations ...... 44 4.4 Sensitivity Analysis ...... 52

5 CONCLUSIONS AND RECOMMENDATIONS ...... 54

LIST OF REFERENCES ...... 56

BIOGRAPHICAL SKETCH ...... 61

LIST OF TABLES

Table page

3-1 Building characteristics used for the model home ...... 25

3-2 Thermophysical and equipment properties of the model home...... 27

3-3 Location, number, and type of lights in the home ...... 33

3-4 Miscellaneous plug loads ...... 34

4-1 DC. Home – Summary of appliances present in the home...... 40

4-2 AC Home – Summary of appliances present in the home...... 41

4-3 PV system Technical data ...... 42

4-4 Electricity retail rate, PV system, and battery cost per unit...... 42

4-5 PV system cost calculation ...... 42

4-6 PV system cost for the DC home...... 44

4-7 PV system cost for the AC home ...... 44

4-8 PV system's terminology ...... 45

4-9 AC system's variable key ...... 45

4-10 DC system's variable key ...... 46

4-11 NPV of the PV system at the end of the 25th year based on original values...... 52

4-12 NPV of the PV system at the end of the 25th year based on 25% values of batteries and appliances...... 52

4-13 NPV of the PV system at the end of the 25th year based on 50% values of batteries and appliances...... 53

4-14 NPV of the PV system at the end of the 25th year based on 75% of batteries and appliances...... 53

LIST OF FIGURES

Figure page

1-1 Energy consumption of typical household use in Florida ...... 13

2-1 Average retail prices of electricity in the US per sector, 1960-2011 (Cents per Kilowatt-hour, including taxes) ...... 17

2-2 Total energy consumption by sector 1949-2017 in the United States ...... 18

2-3 Heat pump clothes dryer component schematics ...... 19

3-1 Climate zones across the country ...... 26

3-2 Floor plan of the Manufactured home...... 26

4-1 PV Watts Result ...... 43

4-2 LCCA of AC system ...... 48

4-3 LCCA of DC system ...... 49

4-4 LCCA of AC system by reducing the cost of batteries and appliances by half ... 50

4-5 LCCA of DC system by reducing the cost of batteries and appliances by half ... 51

LIST OF ABBREVIATIONS

AC Alternating Current

ACH Air Changes per Hour

American Society of Heating, Refrigerating and Air-Conditioning ASHRAE Engineers

CFC Chlorofluorocarbon

CFM Cubic Feet per Minute

DC Direct Current

DOE U. S. Department of Energy

EEM Energy Efficient Measures

EER Energy Efficiency Ratio

EF Energy Factor

EIA Energy Information Agency

EISA Energy Independence and Security Act

EPA Environmental Protection Agency

EPBD Energy Performance of Building Directive

GBC Green Building Council

GHG Green House Gas

HERS Home Energy Rating System

HPCD Heat Pump Clothes Dryer

HPML Higher-Priced Mortgage Loans

HUD U. S. Department of Housing and Urban Development

HVAC Heating, Ventilation and Air Conditioning

IECC International Energy Conservation Code

IPCC International Panel on Climate Change

IRR Internal Rate of Return

LCAM Life- Cycle Affordability Model

LCCA Life-Cycle Cost Analysis

LED Light Emitting Diode

MHCSS Manufactured Home Construction and Safety Standard

MHI Manufactured Housing Institute

MPPT Maximum Power Point Tracking

NPV Net Present Value

NREL National Renewable Energy Laboratory

NZE Net Zone Energy

PPMOF Prefabrication, Preassembly, Modularization, and Offsite Fabrication

PV Photo Voltaic

RECS Residential Energy Consumption Survey

RESNET Residential Energy Services Network

SEER Seasonal Energy Efficiency Rating

SIP Structured Insulated Panel

TDV Time-Dependent Valuation

UF University of Florida

VRF Variable Refrigerant Flow

VSD BDCPM Variable Speed Drive Brushless Direct Current Permanent Magnet

Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science in Construction Management

ECONOMIC FEASIBILITY OF USING DC POWER IN MANUFACTURED HOMES

Venkatesh Kumanan

December 2020

Chair: Abdol R. Chini Co-chair: Ravi Srinivasan Major: Construction Management

The ideology of Go Green, energy conservation, is taking center stage nowadays. Awareness among people to reduce energy use and move to non- conventional power generation sources increases in recent times. The national standard power generation and distribution systems are centralized. Most of the generated power is fossil fuels (about 80%), and 16% are consumed for residential purposes.

As the electric power produced by the photovoltaic (PV) system is initially Direct

Current (DC), using appliances that use the same type of energy, a significant amount of savings in terms of money, energy, and CO2 emissions can be saved. Also, using DC

Brushless Permanent Magnet Motors (BDCPM) in place of standard Alternating Current

(AC) motors, savings up to 30% in power consumption can be achieved.

This project focuses on a fully DC-powered manufactured home, i.e., entirely off- grid. For this research project, the electrical appliances used are DC-powered. A PV system supplies the power source for this manufactured home. It is expected that by replacing the AC with DC power, the annual energy use drops significantly. The home would also have a solar power battery storage system and would not be connected to the AC grid power system.

This study's DC-powered home can also be used for emergency shelters or installation in any off the grid location. Currently, the cost of DC appliances is high due to low supply and demand. However, the costs would reduce as the demand grows, and these appliances are mass-produced. In the long term, DC appliances not only provide significant energy savings but would be economical as well.

Also, life cycle cost analysis s carried out, which indicates the comparative cost savings between the two systems in the long run.

CHAPTER 1 INTRODUCTION

Recently, there has been much research on changing the power system from the conventional AC to DC power system. Literature shows that by using high-efficiency DC appliances instead of AC, savings can be generated as high as 33% in the residential sector. (Garbesi et al. 2011) Thus, the operational energy of a DC home is less than that of an AC home. Even though the overall energy consumption is low, the cost of DC appliances is generally higher than the AC appliances, which result in a higher initial cost for the home. The PV system required for a DC home would be smaller than an AC home due to lower power consumption. This study would conduct a feasibility analysis to determine the savings obtained by having an off-grid DC home to a grid-connected

AC home.

Figure 1-1. Energy consumption of typical household use in Florida. Source: NREL my Florida home energy, 2019

Figure 1-1 shows the typical consumption of household energy use in Florida.

The image depicts most of the electrical energy consumed in an apartment by appliances, electronics, and lighting. By selecting more efficient appliances and an efficient power system, more energy can be saved.

1.1 Statement of Purpose

Once a natural disaster hits a location, the magnitude of after-effects can be disastrous. During such unforeseen conditions, the follow-up work would be to repair and rehabilitate the disaster-hit zone. To carry out the rehabilitation works at the disaster-hit location, there is a need for manufactured houses built quickly. This concept of utilizing a home in the middle of nowhere is the motivation behind this work. Since the home is a manufactured home, it can be assembled and transported easily. The power source is the next big concern for the home as it might be in a deserted area or places where there are no prior power connections. Therefore, solar energy might be considered as a source for generating the power to run the home.

This study would determine if the novel technologies justify using only DC appliances instead of AC appliances. The use of an alternate source of power is proliferating, and in this project, solar power is selected as it is easy to install on the rooftops.

This work focuses mainly on using DC power for off-grid housing, but DC- powered homes can also be used to replace the traditional conventional houses as well.

It would encourage the public to transition towards DC appliances and significantly reduce electricity usage and would, in turn, reduce the emission of CO2, which contributes to climate change.

1.2. Objectives

This research's main objective is to examine the economic feasibility of using DC power in manufactured homes.

The specific research steps are as follows:

1. Identify a typical manufactured home.

2. Identify the standard appliances and their power and use characteristics that are used in a manufactured home.

3. Identify DC appliances that can replace AC-powered appliances in a manufactured home.

4. Estimate annual energy use of the DC-powered manufactured home.

5. Design and size an appropriate PV system and energy storage system.

6. Estimate the cost of PV and energy storage systems.

7. Estimate the payback period for investment in changing AC to DC appliances, PV systems, and energy storage systems.

8. Perform a life cycle cost analysis of a DC-powered manufactured home vs. an AC-powered one.

9. Discuss the cost impact and benefits of DC versus AC-powered manufactured homes.

1.3. Scope of Research

Comparing DC and AC appliances in homes would be performed by identifying the most efficient appliances currently available in the market. Feasibility is determined by comparing the initial cost and conducting a life cycle cost analysis for 25 years. This analysis includes operational, initial, and maintenance costs as well.

Some of the delimitations to the scope of the study are:

• Complexity in wiring and additional safety for electrical components needed for running a DC home.

• The voltage at which the apartment must be operated.

• Additional loads that might come due to electric vehicles.

• The life expectancy of batteries, the PV system, and DC appliances.

1.4. Limitations of this Study

Some of the limitations of this study are as follows:

1. There are many assumptions made in this study, and there is not enough real-time data to back up those assumptions.

2. It is assumed that all months consume the same amount of electricity.

3. It is assumed that the behavior of the occupants is consistent across the years.

CHAPTER 2 LITERATURE REVIEW

2.1 Energy Efficient Buildings

2.1.1 History of Energy Efficiency in Buildings

Historically, energy efficiency concerns were mostly a reaction to the rise in the cost of energy prices. The price of energy was low until a few decades ago, and therefore the idea of efficiency was not of prime importance. Until the 1970s, the cost of oil was less than $1/gal, and eventually, the price of energy was relatively low compared to most people's income. (EIA, 2018) With time, the price of energy started to shoot up, and the general people's focus started shifting towards energy efficiency. From the

1980s onwards, climate-based design or passive design movement also started to gain importance. Figure 2-1 shows the average price of electricity since the 1960s.

Figure 2-1. Average retail prices of electricity in the US per sector, 1960-2011 (Cents per Kilowatt-hour, including taxes). Source: US Energy Information Administration, 2018

In the 1980s, building codes started to incorporate energy efficiency measures in construction. In the initial parts of the 1990s, the US Department of Energy and the US

Environmental Policy Agency (EPA) began the ENERGY STAR program. This program

began with certifying computers and later expanded to include all home and office appliances, including lighting, fans, HVAC, home appliances, and building and industrial plants. (Energy Star, 2018) In the construction sector, improving the built environment's energy performance is crucial to reducing overall energy demand and greenhouse gas emission.

2.1.2 Residential Energy Efficiency

The below figure 2-2 indicates the energy consumption by different sectors in the

United States in the past 50 years. From that, it can be inferred that the residential sector accounted for about more than 20,000 trillion Btu and while the commercial sector consumed about 28,000 trillion Btu in 2017. It is inferred from the below figure that the residential sector consumes a good percentage of energy compared to the commercial sector, and there is a high demand for an alternative source of energy.

(EIA, 2018)

Figure 2-2. Total energy consumption by sector 1949-2017 in the United States. Source: US Energy Information Administration, 2018.

However, the residential sectors' impacts are high; simultaneously, the potential for mitigation is also highly economically feasible. Thus, the federal government

promoted energy efficiency systems in the residential sectors for decades through several strategies like home rating systems and strengthening the energy codes across all the states.

2.2 Heat Dryer

The heat pump dryer works as a closed-loop system by extracting energy from the surrounding air. This air enters the drum and undergoes the refrigeration cycle, which comprises the compressor, condenser, and an expansion device. The first step in this process is to send the warm, humid air into the drum. The air is passed through an initial filter that traps any reliable components or impurities present in the air. The evaporator in the heating mode increases the refrigerant's temperature and pressure. It then passes through a compressor that increases the refrigerant pressure and moves it through the system. When the refrigerant encounters the condenser, it enters with a high temperature and pressure. The air that passes through that point is heated up. It then moves up to the blower and into the dryer next. By the time the air reaches the next coil and condenser tray from the condenser to the expansion valve, it is depressurized, and the temperature is brought down.

Figure 2-3. Heat pump clothes dryer component schematics. Source: P Bansal, 2016.

The advantages of using a heat pump dryer are it is easy to install as they do not require installation. Also, it can reduce energy use by at least 28% compared to standard dryers. They also dry laundry at low temperatures, so they are gentles on clothes. (Energy Star, n.d.)

2.3 Renewable Generation

Residential buildings can usually achieve net positive/zero electricity demand with proper design and photovoltaic systems. The number of photovoltaic systems for residential homes is on the increase substantially for the past few years. (energy.gov,

2019) There are many reasons for it, like a drop in the PV system price, tax credits, increasing utility prices, and growing incentives for renewable energy. (D.W.H Cai, et al., 2013) Another advantage of using a PV system is that homeowners can sell the extra electricity they produce during the sunshine time and minimize their utility bills.

2.4 Energy Use of Affordable Home

Parker obtained data from ten similar single-family conventional homes from the state of Florida. (D.S Parker, et al., 1996) the author collected data at a 15-minute interval. The average electricity consumption per day was 43kWh/day. It used to vary from 21 to 59kWh/day. The cooling system consumed a significant portion of electricity.

It accounted for about 40% of annual electricity consumption. The magnitude is 13.6 kWh/day. At the same time, space heating accounts for about 4%.

2.5 Life Cycle Affordability Costs

In the past few years, several studies have been carried out on assessing the economic impacts of using energy-efficient measures by examining the benefits and costs of implementing these measures. These studies focus on the cost evaluation

associated with it like Net Present Value (NPV), Internal Rate of Return (IRR), Energy inflation, and discounted payback period (Liu. Y, 2018).

Life cycle cost analysis (LCCA) is a useful tool in evaluating the financial advantages of different alternatives over time. Through LCCA, the initial investment, yearly savings, yearly expenses, cumulative savings, and cumulative expenses are calculated. (U Congress, 2009) As a result, the future costs are discounted to "net present value" by adopting the corresponding discount percentage. The different rates are a significant factor when comparing different alternatives.

Using alternate energy-efficient techniques depends on the total money invested in money saved from the project due to energy savings. As other techniques are adopted, the cost of construction would increase. Savings compensate for this increase in energy obtained by adopting the novel techniques.

2.6 Manufactured Housing

Manufactured housing is a process of constructing a building component or an entire building in a factory condition. These are built off-site and then transported to the respective site location. In the residential sector, these homes are known as modular and manufactured homes. The construction of modular homes is governed by the same residential codes governing traditional on-site home construction. On the other hand, manufactured homes are built on permanent chassis and are built according to the federal building code. They are also administered by the US Department of Housing and Urban Development (HUD) and known as the HUD Code.

These manufactured homes came into effect post-war era and the automobile industry's rise in the late 1920s. House trailers became an essential source of temporary housing for war plant workers and the federal construction projects that came

into effect post-war. By the 1970s, the mobile industry produced a significant portion of the single-family homes in the US and served a broad market, not only construction workers. (US Census, 2017) However, the manufactured construction's growth was also accompanied by their concern regarding these homes' durability. That is when the HUD

Code became the only federal regulation for construction in the United States.

The portion of manufactured homes roughly reached 6% of the United States housing market (EIA, 2018) in 2017. Gavin's research (Wherry G, 2014) indicated that the manufacturing home industry is declining due to its life cycle. Also, the US residential construction sector changes and increasing demand for on-site construction are another reason for the drop in numbers for this type of home. Manufacturers need to look for strategic advancements to be competitive in the residential market to improve this trend.

In 2017, Texas had the highest number of purchased homes, followed by

Alabama and Florida. (MHI, 2017) Those 3 states constituted about a third of the total manufactured home in the country. Overall, 8 states constituted more than 50% of the overall demand. One of the reasons for the dominance of 8 states is that all other states are in hot or mild climates and most prone to hurricane and sea-level rise except

Michigan.

On comparing the cost part of it, a manufactured home is an excellent option as it is one of the foremost providers of affordable housings (MHI, 2017). Many reasons are attributed to this. One of them being less strict building codes compared to conventional design building codes. Another reason is that the components are being fabricated in a controlled factory environment that uses an assembly line technique. Factory

manufacturing removes the needs for on-site construction and plays a significant role in increasing productivity. Besides, since the components are produced in bulk, the manufacturers purchase the raw materials and appliances in bulk, generating considerable construction savings. Therefore, these types of homes are excellent options for low-income people.

2.7 DC vs. AC

Recent interest in DC directly supplying energy to appliances has been because of the speedy rise of PV technologies, which are being used in the residential and commercial sectors. Also, energy-efficient products tend to use more DC power internally. DC motors are about 30% more effective than their AC counterpart (Nixon,

2019). These savings have been depicted by commercial data centers that run on DC internal. (Garbesi et al., 2011)

In the past, DC appliances served tiny markets for decades and have proven to the world that they have enough energy to cater to the globe's needs. These markets include off-grid apartments, data centers, emergency shelters, and remote research hubs. (Garbesi et al., 2011)

Some of the past literature suggests that using DC-based design, the efficiency of all significant power utilizing processes like HVAC, clothes washing and dryers, water heating, and others increase significantly. In general, electronic appliances function with

DC internal instead of AC appliances, as DC motors are more efficient than AC motors.

(Garbesi et al., 2011)

Generally, the DC power, which is generated from the PV system, is converted to

AC using an inverter. This AC power is supplied to the apartment at 240V and 120V for high and low power loads. With the new technologies in place, there is no need to

convert this power. DC power generated from the PV system can directly be used to run the DC appliances.

2.8 Three-Phase Brushless DC Permanent Magnet Motors (BDCPM)

In general, the increase in home appliances is related to the growth of energy efficiency measures incorporated in those appliances. Reducing the appliances' power consumption would aid the manufacture in applying for specific certifications like Energy star. The Energy Star rating would provide the buyers confidence that they would consume less power than other comparable specifications. (Irakoze,2018)

The reduction in power consumption is because the BDCPM motors are much more energy-efficient than a single-phase AC induction motor. (Nixon, 2019) To reduce the house's overall power consumption, the appliances were modified with three-phase

BDCPM motors from the traditional AC motors, which have been used traditionally.

(Irakoze,2018) With the advancement of technology and mass production, it is possible to produce these three-phase DC BDCPM motors at a low cost. These motors can support the same robustness and torque level as that of a single-phase AC induction motor. BDCPM motors are mechanically and physically complex to manufacture, but they are more efficient and produce less noise than a single-phase AC induction motor.

(Irakoze,2018)

CHAPTER 3 METHODOLOGY

The methodology in carrying out this research project is divided into four steps:

1. Selection of building for monitoring loads,

2. Selection of standard appliances for DC-powered and AC powered,

3. Calculation of loads due to the appliances and design of PV systems with battery storage,

4. Determining the simple payback period and life cycle cost of both AC and DC- powered houses.

3.1 Home Location Selection

The first step in this process was to determine the home, which was to be analyzed for this project. The home was chosen such that it would be affordable and has the essential features that were required for single-family living. The home's zone should also be determined as the climatic conditions play a significant role in determining the home's energy consumption and production. Based on the climatic map published by NREL, zone 2 was considered for the analysis. For simplicity purposes, the home was assumed to be in Gainesville, Florida. Figure 3-1 indicates the different climatic zones in the country. It varies from Zone 1 to 7. The selected property falls on zone 2.

Table 3-1. Building characteristics used for the model home. Building Characteristic Double Section Location Gainesville, Florida Number of bedrooms/baths 3/2 Average square feet 1,204 Ceiling height 8' Roof type Gable (4:12), unfinished attic

The model home selected for this study is a manufactured home used by US

DOE in Alabama. Figure 3-2 shows the floor plan of the home, and Tables 3-1 shows its

characteristics. Thermophysical and equipment characteristics of the home are shown in Tables 3-2 (Fenner, 2019).

Figure 3-1. Climate zones across the country. Source: NREL E. Bonnema, 2016.

3.2 Home Properties

Figure 3-2. Floor plan of the Manufactured home. Source US Department of Energy (E Levy, 2016)

Table 3-2. Thermophysical and equipment properties of the model home. Description Properties Building orientation South-North axis Walls Material Wood stud, 2X4, 16 OC R-Value R-11 fiberglass batt Exterior finish Vinyl, light Unfinished attic, R-22 blown fiberglass, vented Ceiling ceiling Roofing Roofing with asphalt shingles, dark Floors R-14 Fiberglass blanket Foundation Pier and beam, 3 feet height Thermal mass Drywall: ½-inch for walls, 5/8-inch ceiling Windows Window area 12% F25, B25, L25, R25 Window proprieties Single pane, metal frame, U-0.47, SHGC 0.73 Window interior shading 0.75 Door proprieties Wood, 20 ft2, U-0.40 Eaves 1 foot Air Flow Infiltration 4.7 ACH50 Mechanical ventilation 21.56 cfm/unit Space conditioning Central air conditioning 2 tons; SEER 13; EER 11 Rated supply fan 0.34 W/cfm Installed supply fan 0.68 W/cfm Electric furnace 35 kBtu/hr Duct leakage 4.54 CFM25/100ft2, average R-8 Space conditioning schedules Cooling 78 °F, Heating 68 °F Water heater Electric, 50gal, EF 0.90 Miscellaneous 100% incandescent Appliances and fixtures Top freezer Benchmark (434 kWh/yr) Electric cooking range Benchmark (499 kWh/yr) Dishwasher Benchmark (318 kWh/yr) Clothes washer Standard (MEF 1.41) Clothes dryer Electric (EF = 3.1) Hot water fixtures Standard Use

3.3 Appliances Selection

The next step was to select the necessary appliances. While selecting the appliances, great care was taken to make them affordable while satisfying the living needs. Based on that, a list of appliances that are used in day-to-day living was created.

These are comprised of a refrigerator, washing machine, dryer, Television, HVAC, cooking range, Microwave. For comparing AC powered and DC powered, appliances are selected and grouped into three categories. Great care was taken while selecting the appliances to compare the ones with similar specifications. The first one being appliances that have an equivalent DC appliance in the market. The second one is appliances that do not have a compatible DC one but can work as a DC appliance by changing the motor. The third category is the list of appliances that can run on both AC and DC supply.

An Excel spreadsheet is created to compare the cost of the products and annual power consumption, which contains the appliance name, brand, model number, cost of the appliance, and annual power consumption. The spreadsheet would give a fair comparison between both groups. The overall power consumption and each appliance's cost for the respective power source can be inferred from the spreadsheet.

The list of appliances, equipment, and fixtures that are included in the comparison are as follows:

• Refrigerator

• Clothes washer

• Clothes dryer

• Dishwasher

• Induction cooktop

• Microwave

• Air conditioner unit

• Lighting fixtures

• Ceiling Fans

• Other electric devices (Miscellaneous electrical loads)

3.3.1 Refrigerator

Unique appliance manufactures 10 cu. ft. DC refrigerator with freezer using one of the most recent energy-efficient technologies. The UGP-275LW "Solar Powered

Fridge with Freezer" costs about $1,417. It operates under 12V/24V. The annual energy consumption is about 213kWh/yr. Danfoss/ Secop manufactures the BD35F compressor, which is used for this refrigerator. Some of this compressor's salient features are that it consumes low energy, low sound emission, and is environmentally friendly due to its CFC free refrigerant uses. The motor in the compressor is brush-less and has a variable speed high-efficient motor. (Home Depot,2020)

While comparing the AC counterpart, a similar capacity refrigerator must be selected to have a valid comparison. Based on that, a Haier 9.8 cu. ft. refrigerator is selected.

The annual power consumption is estimated to be 327kWh/yr, at about $629. (Home

Depot, 2020)

3.3.2 Clothes Washer

Initially, Unique appliances used to manufacture an off-grid DC clothes dryer

(Unique). The model number was UGP-72 LD1. Later the product was discontinued due to electronic issues. Since then, there has not been any commercial DC clothes dryer.

Therefore, it is assumed that a comparable Variable Speed Drive (VSD) Brushless DC

Permanent Magnet (BDCPM) motor replaces the AC motor in the counterpart. It is

estimated that BDCPM motor is about 30% more efficient than AC induction motors.

(Nixon, 2019). The Energy Star rated WTW5000DW model clothes washer by Whirlpool has an annual energy use of 300kWh/year and has a 4.3 cu. ft capacity. As per Lowe's website, the current market price is $749.00 (Lowe's, 2020).

3.3.3 Clothes Dryer

Bloomberg Appliances DHP24400W is a 24" Heat Pump Ventless white trim base model with a 4.1 cu. ft capacity. It works on the concept of Heat Pump Clothes

Dryer (HPCD). Some of the salient features are the new energy star emerging technology, stainless steel drain, and Opti-sense drying. It is estimated that this dryer consumes 50% less energy than condenser dryers. Based on the appliance land website, this dryer would cost around $1,495. (appliance land, 2020)

On the other hand, the AC counterpart also has a hybrid heat pump. The

WHD862CH by Whirlpool has a capacity of 7.4 cu. ft. It is energy star certified and runs on electricity. The rated power consumption of this is 460kWh/yr, and its cost is $ 1,899.

(Whirlpool, 2020)

3.3.4 Dishwasher

There are currently no DC dishwashers that are commercially available in the market. Therefore, it is assumed that a comparable Variable Speed Drive (VSD)

Brushless DC Permanent Magnet (BDCPM) motor replaces the AC motor in the counterpart. It is estimated that BDCPM motor is about 30% more efficient than AC induction motors. (Nixon, 2019). In addition to the change of motor, the heat pump would also reduce power consumption. But the ratio of power-sharing between the motor and heat pump is complicated. Therefore, it is assumed that both AC and DC electric heaters have the same efficiency. The Energy Star rated SHPM78Z55N model

dishwasher by Bosch has an annual energy use of 269kWh/year and has the current market price per Lowe's website is $1,149.00 (Home Depot, 2020).

3.3.5 Cooktop

There are currently no DC commercial electric stoves. The lack of cooktops is because some of the components like switches, transistors, and thermostats work on

AC only. A research was conducted by the Massachusetts Institute of Technology in

2014. A one-of-a-kind battery powered induction stove was designed to run off low voltage inputs and runs at a high efficiency powered by a 24V DC (Weber, 2014). The results from the study indicate that the efficiency is close to 90% and more sometimes.

There is no official price associated with it as it is the research stage but would technically be cheaper than a conventional induction stove. It is estimated that it consumes about 500W and 25A of current. It can be directly connected to the battery and, eventually, useless electrical components.

The AC counterpart is also a single element cooktop to have a fair comparison with a single element DC cooktop discussed above. Avantco ICBTM – 20 Countertop

Induction Range, which costs about $135 (Amazon, 2020). This appliance consumes about 1800W.

3.3.6 Microwave

There are very few DC microwave options available in the market. One such of them is the 12-volt PNP-410 Microwave by Power Hunt. The market price of it is currently unknown as there is no available stock of the product. (Amazon, 2020). It consumes about 660W of power. On the other hand, the AC counterpart Panasonic NN-

SN6865 consumes about 1200W and costs about $170. (Amazon, 2020).

3.3.7 Air Conditioner

A split system was selected for the HVAC system in both AC and DC scenarios.

Four ductless split systems are required since there are three bedrooms and one living room. DC 48 by Hotspot Energy is selected as it has one of the most significant capacities when searched across the online database. The 12,000 BTU 48V DC HVAC system consumes 500W for cooling, and 722W for heating, and a single unit costs about $1,995. (HotSpot Energy, 2020)

One more advantage of using this DC HVAC system is that DC compressors and fan motors provide a soft start to the appliance. This technology's advantage is that when a typical AC air conditioner starts, it requires 500% more amps on startup. Thus, there is no need for oversizing the PV system to handle this initial phase. (HotSpot

Energy, 2020)

The presence of a VRF (Variable Refrigerant Flow) controller, frequency driver, sensors, and a control circuit help adjust the system capacity as conditions change in real-time. The VRV controller also controls the fan and compressor speed, refrigerant flow, and consumes about 30% to 40% less energy. The control circuit kicks into the lower energy level when the system approaches the desired system units. It would help in lower power consumption of energy and maintain a consistent temperature. (HotSpot

Energy, 2020)

On the other hand, the AC counterpart is manufactured by Pioneer

WYS012AMFI19RL-16 (Home Depot, 2020). It is energy star rated and is a similar comparison with DC 48. It consumes about 600 kWh/yr and costs about $ 720.

(Amazon, 2020)

3.3.8 Lightning

For lightning, it does not matter if the power source is AC or DC Irrespective of the power sources, LEDs (Light Emitting Diode) bulbs would work as they have an in- built diode which would convert the AC power source to DC. In this study, based on the usage, the light source's wattage varies from 9W to 43W. In general, there is a conversion loss of 4% when the power is converted from AC to DC. If the input power is

DC, then that loss would not be applicable. Table 3-3 indicates the different lighting fixtures available in the home.

Table 3-3. Location, number, and type of lights in the home. Location Number of lights Type of light Kitchen 1 ceiling mount FL Bathroom 1 fan/light Inc 1 over sink Inc 1 ceiling mount Inc Bedroom (3) 3 ceiling mount Inc Living Room / Dining 2 ceiling mount Fl Room 1 Floor Lamp Fl laundry no light closet no light Exterior 2 wall mount

3.3.9 Ceiling Fan

One of the DC fans available in the market is the Emerson 60" Carrera Grande

ECO (DC EcoMotor) w/Remote in Graphite. The advantage of EcoMotor is that it is 3 times more effective than a typical ceiling fan. The EcoMotor uses a permanent magnet instead of energized copper windings and optimally reduces the current consumption by

3 to 5 times less than equivalent AC ones. The cost of each fan is typical $508. (Hansen

Wholesale, 2020).

On the other hand, the AC counterpart is listed on the "Energy Star's Most

Efficient 2020" database. The Westinghouse 72228 has a blade span of 52" which is of

comparable size to the DC one. This fan consumes about 33W when running at high speed and 3.5W when at low speed and costs about $130 each. (Energy Star,2020)

3.3.10 Other Miscellaneous Loads

There are many plug loads like Television, laptop, coffee maker, and others used on a day to day basis. All these appliances have an internal AC – DC converter to convert the power to the DC power source. But if DC power supply is used instead of

AC, there is no need to have an internal power consumption. Hence there are power savings there. The following is a list of miscellaneous plug loads that are considered for analysis. The capacity is taken the same for both the different types of power sources. A miscellaneous load is considered to incorporate any missing loads in this analysis. (J.

Bruggett, 2016) The only drawback is that each device works at various voltage. A universal voltage converter must supply at a constant voltage, or multiple wiring must be carried out at various voltages. One of the drawbacks of wiring is the complexity involved in it and the costs associated with it.

Table 3-4. Miscellaneous plug loads. Source: J. Bruggett, 2016. S. No Appliances Power Consumption (kWh/yr) 1 Rechargeable Electronics 69 2 Television 51 3 Desktop Computer 150 4 Set - top box cable 60 5 Computer Monitor 54 6 Clothes Iron 49 7 Vacuum Cleaner 41 8 Printer 39 9 Hair Dryer 36 10 Toaster and Toaster Owen 35 11 DVD Player 27 12 Cable / DSL Modem 21 13 Coffee Maker 37 14 Miscellaneous 331 Total 1000 Table 3-4 indicates the different appliances along with the annual power consumption.

3.4 Photo-Voltaic System Selection

Once the appliances used in this apartment have been finalized, the energy consumption due to these appliances is determined. From the annual energy consumption, daily energy use of DC appliances is calculated. The PV system's capacity, which is going to be added to the home, is designed based on the energy consumption, backup hours (which is needed to design the battery capacity and the number of batteries), wattage, type, and arrangement of solar panel that is going to be used in this home is determined. Based on the system outputs (Voltage and Ampere), the appropriate charge controller is selected for the PV system. In this project, January

21 and July 21 are used as design dates for winter design and summer design. These dates are selected based on ASHRAE design data. The requirement for selecting a battery is that the battery's size must be more significant than 11.37 kWh per day (per day energy consumption). 60-hour power back is considered, and LG Chem 9.8 kWh battery is taken into consideration. Based on this calculation, a minimum of 3 batteries is required for the home.

Solar connectors are used for connecting the various components in the PV system. A 400 W monocrystalline solar panel by Axitec is selected for this project.

Based on the calculations, a 4 kW PV system is required to provide electricity for the house. The house's yearly consumption is 4,150 kWh/year, and from PV Watts, the electricity generated is 5,976 kWh/year. Therefore 10 panels of 400 W are connected in parallel. (a1solar store, n.d.)

60A MPPT Solar Charge Controller is selected to aid in the process of power transfer. The electricity generated from the PV cells is transmitted to the charge controller, which sends out the power at a regulated voltage to the batteries and the

appliances. The primary use of the charge controller is to regulate the voltage supply.

(Amazon, 2020) Solar connectors were used for connecting the components. A simple payback period and the life cycle cost of the AC and DC-powered houses would be calculated based on the above costs. From the payback analysis, the number of batteries for power backup might be altered again. Considering a 25-year life, the initial cost, maintenance cost, replacement cost, energy cost at the end of every year would be determined. The life cycle cost analysis would consider that as the demand increases, the cost of DC appliances, PV systems, and solar power battery storage system decreases. In the end, the advantages of using these kinds of apartments being dealt with in detail, and a spreadsheet can be generated to calculate the payback period for using new technologies.

3.5 Photo-Voltaic Life Cycle Cost Analysis

The basic understanding of LCC analysis was explained in Chapter 1 and 2 in detail. In this chapter, the methodology to carry out the analysis is explained in detail.

The general data that is required to carry out the LCCA is described in the table below.

(Table 3 – 5). The system costs are obtained from the historical data and the current market price (Gainesville, FL). These costs include material, labor, and installation costs. The Investment Tax Credit (ITC) allows users to deduct 26% of the cost of installing a PV system from federal taxes. The typical cost of electricity in Gainesville is about $0.13 up to 850 kWh per month. (GRU, 2020) Since the monthly consumption is below 850 kWh, this value holds good.

The following are the steps to carry out life cycle cost analysis.

Step1: The first step is to determine the economic and technical data associated with the components. The data includes the cost of the component, labor charges

associated with it, maintenance cost, the lifetime of the component, residual cost at the end of the component's lifetime, and other costs associated with it like contract costs, permit costs, and other administrative costs.

Step2: In an excel spreadsheet, define the metrics that are needed to carry out the calculations. The metrics include Year, Loan, Payment, Down Payment,

Replacement Cost, Maintenance Cost, Electricity Costs, and others. Two sheets are created—one for AC source and one for DC source.

Step 3: With the energy consumption information, and the data provided in

Step1, prepare a master table and analyze the outcomes from it.

Step 4: From the spreadsheet, two analyses were performed. One was to compare the life cycle cost for 25 years, and the second was to perform the same analysis but to consider the reduced cost of batteries and appliances.

Step 5: Sensitivity analysis was performed to understand the impact of crucial variables while calculating the project's economic feasibility.

CHAPTER 4 RESULTS AND DISCUSSION

4.1 Annual Energy Consumption of DC and AC Appliances

In 2018, the annual energy consumption in the United States was estimated to be 10,972 kWh. The monthly consumption comes down to 914kWh (EIA, 2019). The home selected monthly consumption is 610 kWh for the AC home and 346 kWh for the

DC home. The miscellaneous plug loads are the same for both power sources as they have internal AC – DC converters and work in DC supply only.

Of the monthly consumption, 200 kWh (117 kWh for DC) is consumed by HVAC,

266 kWh (98.25 kWh for DC) by appliances, and 61 kWh (47.5 kWh for DC) by lightning and fans (Tables 4-1 and 4-2). The energy consumed by DC appliances is less than AC appliances because of new technologies like VSD BDCPM motors in the fans and compressors of the appliances along with heat pumps, eliminating AC- DC converters. Tables 4-1 and 4-2 indicate the appliances, makers, model number, and yearly power consumption. The power consumption of the appliances is of three types.

One type has an energy star label, which indicates the annual energy consumption. The second type is not energy star rated, but they have the annual power consumption. The last category has hourly consumption. By multiplying the average hourly consumption, the annual power consumption is identified. The respective conversion loss is not taken into consideration.

푘푊ℎ (4-1) 퐴푛푛푢푎푙 푃표푤푒푟 퐶표푛푠푢푚푝푡𝑖표푛 ( ) 푦푟

= 푃표푤푒푟 (푊) ∗ 퐷푎𝑖푙푦 퐻표푢푟 푈푠푎𝑔푒 ∗ (365/1000)

On the other hand, the DC appliances cost is higher than that of their AC counterpart, even though they have relatively close or same performance, capacity, and size. There are many reasons for this. One reason for this is using the latest DC appliances technologies, such as incorporating BDCPM motors on DC appliances, using heat pumps, and other efficient methodologies. Another reason could be the availability of these appliances. Since these are produced in significantly less quantity, their relative cost is higher expensive. If produced in bulk, the cost of the DC appliances would come down significantly. The appliances' overall cost was $ 7,844 for AC appliances and $14,008 for DC appliances. For the DC appliances with no cost available, the cost of AC appliances is considered. The exact cost cannot be determined due to a lack of data availability. The appliances which fall into this category are clothes washer, dishwasher, and Microwave.

Table 4-1. DC. Home – Summary of appliances present in the home. Energy Model Power Star S. No Equipment Brand Cost ($) Comments Number Power Watts kWh/yr Unique 1 Refrigerator UGP-275LW $ 1,417 213 Appliances Clothes 2 $ 749 210 Washer Clothes Bloomberg Assuming 15 min 3 DHP24400W $ 1,495 900 82 Dryer Appliances daily consumption 4 Dishwasher $ 1,149 188 Inverter type Power Assuming 30 min 5 PNP - 410 $ 170 660 120 microwave Hunt daily consumption Assuming 2 hr daily 6 Induction coil $ 540 500 365 consumption Air Hotspot Assuming 12 hr 7 DC 48 $ 7,980 80 1402 Conditioner Energy daily consumption Interior 8 370 Lighting 9 Exterior 115 11 Fan Emerson $ 508 85 Other Plug 12 1000 Loads Total $ 14,008 4,150

Table 4-2. AC Home – Summary of appliances present in the home. Energy S. Power Star Equipment Brand Model Number Cost ($) Comment No Power Watts kWh/yr 1 Refrigerator Haier HA10TG21SS $ 327 629 Clothes 2 Whirlpool WTW5000DW $ 749 300 Washer 3 Clothes Dryer Whirlpool WHD862CH $ 1,899 460 4 Dishwasher Bosch SHPM78Z55N $ 1,149 269 Assuming 5 Microwave Panasonic NN-SN6865 $ 170 1200 219 30 min daily consumption Assuming 2 6 Induction coil Avantco ICTBM-20 $ 540 1800 1314 hr daily consumption Assuming 7 Air Conditioner Pioneer WYS012AMFI19RL-16 $ 2,880 2400 12 hr daily consumption 8 Interior Lighting 370 9 Exterior 115 11 Fan Westinghouse 72228 $ 130 225 Other Plug 12 1000 Loads Total $ 7,844 7,301

4.2 Photo Voltaic System

A 4 kW PV system is selected to supply electricity for the apartment. From table

4-1, the annual consumption of electricity is 4,150 kWh. The annual production of a 4- kWh solar panel system is about 5,976 kWh for Gainesville from PV Watts. The solar panel system cost includes labor charges for installation, wire, conduit, fittings, breaker, and other miscellaneous components to complete the system that comes to $1.00 per kW. (Go Green Solar, 2020) Essentially the cost per watt comes to $ 5.75.

Table 4-3. PV system Technical data. Technical Data System Size 4 kW Roof Size 1200 sq. ft. PV Efficiency 20% PV degradation 1% Maintenance 1% Derating Factor 86% Tilt angle 20° Azimuth 180° Mounting type Fixed (roof mount) System Loss 14.08% Table 4-4. Electricity retail rate, PV system, and battery cost per unit. Electricity rates Installed cost 5.75 $/Watt Battery Cost 535.72 $/kWh Buying / Selling cost of electricity 0.13 $/Watt Table 4-5. PV system cost calculation. S. No. Component Cost per Quantity Unit Quantity Total cost 1 Solar Panel $ 225.00 No 10 $ 2,250.00 2 Batteries $ 5,525.00 No 3 $ 16,575.00 3 Solar Charge Controller $ 178.00 No 1 $ 178.00 4 Labor Charges $ 1.00 kW 4000 $ 4,000.00 Total Cost $ 23,003.00 The technical data that comprises the PV system properties and the PV system's components cost are summarized in tables 4-3 and 4-5. Table 4-4 indicates the cost involved in utilizing the power if consumed from the grid and if self-produced.

Figure 4-1. PV Watts Result.

4.3 LCC Calculations

Table 4-6. PV system cost for the DC home. DC home- System Costs Total System Costs $ 36,516.00 Down Payment $ 3,652.00 Loan Costs $ 47,493.47 Table 4-7. PV system cost for the AC home. AC home- System Costs Total System Costs $ 7,349.00 Down Payment $ 740.00 Loan Costs $ 9,588.26 Tables 4-6 and 4-7 indicates the necessary cost data for the PV system of the

DC home for performing a life cycle cost analysis. It was assumed that a down payment of 10% and the loan to be repaid in 15 years totals about $ 47,493.47. The battery and the appliance's life expectancy is assumed to be 12.5 years, and that of the PV system is 25. Post the warranty period, the components may still be used, but they are replaced with brand new systems for simplicity purposes. The salvage value is assumed to be zero. The monthly maintenance cost is about $230, which is 1% of the initial costs.

(Solar,2018) The maintenance cost increases annually by 1.7% due to the inflation rate.

Assuming that the building is built in 2020, the homeowner is eligible to deduct 26% of the cost of installing a solar energy system from their federal tax. The terminology which needs to be used in the LCC Analysis is provided in table 4-8.

Loan Payment: Amount to be paid monthly as per the rate of interest, loan term, and total system costs. The formula is:

퐿표푎푛 푃푎푦푚푒푛푡 = 푆 ∗ (1 + (𝑖))^푛 (4-2)

Down Payment: Amount that is to be paid at the start of the project. It is generally between 10% to 20% of the total system costs. For this project, it is assumed to be

10%.

퐷표푤푛 푃푎푦푚푒푛푡 = 푆 ∗ 퐷푃

Maintenance Cost: The following is the formula applied to obtain the annual maintenance cost associated with maintaining the good running condition.

푀 𝑔 푦 (4-3) 푀푎𝑖푛푡푒푛푎푛푐푒 퐶표푠푡 = 푆 ∗ ( ) ∗ (1 + ( )) 100 100

Annual Net Balance:

퐴푛푛푢푎푙 푛푒푡 푏푎푙푎푛푐푒 (4-4)

= − 퐿표푎푛 푝푎푦푚푒푛푡 − 푑표푤푛 푝푎푦푚푒푛푡 − 푚푎𝑖푛푡푒푛푎푛푐푒 푐표푠푡

+ 푑푒푝푟푒푐𝑖푎푡𝑖표푛

PV system's Net Present Value (NPV):

푑 −푦 (4-5) 푃푉 푁푃푉 = 퐴푛푛푢푎푙 푛푒푡 푏푎푙푎푛푐푒 ∗ (1 + ( )) 100

Accrued/total NPV: 퐴푐푐푟푢푒푑 표푟 푡표푡푎푙 푁푃푉 (4-6)

= ( 퐴푐푐푟푢푒푑 표푟 푡표푡푎푙 푁푃푉)퐿푎푠푡 푌푒푎푟 + (푃푉 푁푃푉)푃푟푒푠푒푛푡 푦푒푎푟

Table 4-8. AC system's variable key. Variable's Key Name Unit Symbol Term of loan Yr n 15 Year Yr y Electricity costs $ E 0.13 Appliances Cost $ 7,349 Down Payment $ DP $ 735 Rate of interest % i 5% Discount % d 2.5 Energy inflation rate % e 5 General inflation rate % g 1.7 Annual energy consumption kWh/month EC. 7,301

Table 4-9. PV system's terminology. Variable's Key Name Unit Symbol PV system size kW P Average daily sun hours hr K Term of loan yr n Year yr y Electricity costs $ E System Cost $ S Tax Credit $ T Down Payment $ DP. Rate of interest % i Energy inflation rate % e General inflation rate % g Discount rate % d Annual maintenance % M Annual energy consumption kWh/month EC. Annual energy generation kWh/month EG. Table 4-10. DC system's variable key. Variable's Key Name Unit Symbol PV system size kW P 4 Average daily sun hours Hr K 5.53 Term of loan Yr n 15 Year Yr y Electricity costs $ E 0.13 PV System Cost $ $ 23,003 Appliances Cost $ $ 13,513 Overall Cost $ S $ 36,516 Appliances and Battery Cost $ $ 30,088 Discount % d 2.5 Down Payment $ DP $ 3,652 Rate of interest % i 5% Energy inflation rate % e 5 General inflation rate % g 1.7 Annual maintenance % M 1 Annual energy consumption kWh/month EC. 4,150

Annual energy generation kWh/month EG. 5,976

With the help of the above formula, the LCC analysis was carried out for two cases. LCC analysis is carried for 25 years. In the first case, at the end of 25 years, the

AC system is still more cost economical than the DC system. But in the second case, the DC system is much more economical than the AC system. This is because the batteries' cost has been assumed to be 50% of the original cost. Also, the cost of appliances is reduced by 50% of the difference between the AC and DC appliances.

With the advancement of technology and increased production, there would be an overall drop in the components' price. Table 4-9, onwards, would explain the difference better.

Figure 4-2. LCCA of AC system

Figure 4-3. LCCA of DC system

Figure 4-4. LCCA of AC system by reducing the cost of batteries and appliances by half.

Figure 4-5. LCCA of DC system by reducing the cost of batteries and appliances by half.

4.4 Sensitivity Analysis

The PV system's cost, the energy inflation rate, and the discount rate were selected to carry out the sensitivity analysis. Two parameters were kept constant, and the other parameter was varied to better understand the impact of these parameters in determining the study's significance. The cost of the PV system includes the cost of the entire PV system (including installation), batteries, and appliances. The cost of the appliances is the difference between the AC appliances and DC appliances cost. For example, assume the cost of AC appliances (total) is $200, and DC appliances are

$300. For a 25% case, the value is (300-200) *0.25, which is $25. That is how the cost of appliances is obtained for sensitivity analysis. The discount rate for this analysis is assumed to be 2.5%. For sensitivity analysis, a value greater than the assumed value and one less than the assumed value is taken for better understanding.

Table 4-11. NPV of the PV system at the end of the 25th year is based on original values. Original Value 1.50% 2.50% 3.50% EIR / Discount AC DC AC DC AC DC 3% $ 42,435 $ 74,096 $ 42,435 $ 67,105 $ 42,435 $ 60,972 4% $ 46,206 $ 74,096 $ 46,206 $ 67,105 $ 46,206 $ 60,972 5% $ 50,628 $ 74,096 $ 50,628 $ 67,105 $ 50,628 $ 60,972 6% $ 55,822 $ 74,096 $ 55,822 $ 67,105 $ 55,822 $ 60,972 7% $ 61,933 $ 74,096 $ 61,933 $ 67,105 $ 61,933 $ 60,972 Table 4-12. NPV of the PV system at the end of the 25th year based on 25% values of batteries and appliances. 25% Value 1.50% 2.50% 3.50% EIR / Discount AC DC AC DC AC DC 3% $42,435 $45,904 $42,435 $41,661 $42,435 $37,937 4% $46,206 $45,904 $46,206 $41,661 $46,206 $37,937 5% $50,628 $45,904 $50,628 $41,661 $50,628 $37,937 6% $55,822 $45,904 $55,822 $41,661 $55,822 $37,937 7% $61,933 $45,904 $61,933 $41,661 $61,933 $37,937

Table 4-13. NPV of the PV system at the end of the 25th year based on 50% values of batteries and appliances. 50% Value 1.50% 2.50% 3.50% EIR / Discount AC DC AC DC AC DC 3% $42,435 $49,661 $42,435 $45,038 $42,435 $40,982 4% $46,206 $49,661 $46,206 $45,038 $46,206 $40,982 5% $50,628 $49,661 $50,628 $45,038 $50,628 $40,982 6% $55,822 $49,661 $55,822 $45,038 $55,822 $40,982 7% $61,933 $49,661 $61,933 $45,038 $61,933 $40,982 Table 4-14. NPV of the PV system at the end of the 25th year is based on 75% of batteries and appliances. 75% Value 1.50% 2.50% 3.50% EIR / Discount AC DC AC DC AC DC 3% $42,435 $54,688 $42,435 $49,534 $42,435 $45,012 4% $46,206 $54,688 $46,206 $49,534 $46,206 $45,012 5% $50,628 $54,688 $50,628 $49,534 $50,628 $45,012 6% $55,822 $54,688 $55,822 $49,534 $55,822 $45,012 7% $61,933 $54,688 $61,933 $49,534 $61,933 $45,012 Similarly, EIR rates are assumed to be 5%. Similarly, with discount rates, 2 values above and below the assumed value are taken for a better cost breakdown.

Based on the analysis, the following tables, 4-11,12,13,14, were generated. The values indicate the PV system's net present worth at the end of the 25th year for four different system costs.

From the above table, it is understood that as the cost of batteries and the DC appliances drop, the DC system becomes more and more economically feasible.

Similarly, as energy inflation rates increase, the AC system becomes more expensive, and thus the DC system is feasible. The last case is that as the discount rate increases, the net present worth of the AC home increases, and the DC home becomes more affordable.

CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS

This chapter deals with summarizing the interpretations from the entire research work that has been carried out and includes recommendations for future study. The

United States consumes about 33% of worldwide energy use. In which the residential sector accounts for 16% of national consumption. With the slow adoption of power generation through solar energy, CO2 emissions can be reduced. Also, the longevity of fossil fuels and other non-renewable sources of electricity production can be extended.

Since this home is prefabricated and can be assembled on-site, it can be transportable to any place and can be easily set up in a short time. Additionally, the PV system of power source ensures no delay in waiting for a power source.

From the results, it is inferred that DC appliances are currently 46% more expensive than the AC counterpart. But on the other hand, it consumes 76% less electricity than using AC powered electric appliances. The cost of the PV system and

DC appliances over time with an increase in demand eventually helps get the prices down helps the price to descend. By the LCCA, the overall yearly savings by adopting the PV system is explained in the tables. By assuming that the batteries and appliances' price drops over time, around $4,000 is saved at the end of the 25th year using the DC system over AC. Figure 4-1 to 4-4 gives us a better understanding of this. That depends on a few factors like the rate of interest, the term of the loan, discount, general inflation rate, and others. By performing more analysis and by taking real-time data, better results can be predicted.

Figures 4-1 to 4-4 indicate the LCCA for 25 years of the time of the building. 25 years is considered as it is the lifetime of the PV system. From the first two figures, it is

inferred that the DC system is expensive in the long run compared to the AC system, but by reducing the prices of batteries and the appliances by half, at the end of the 25th year, the DC system is economical compared to AC system.

From the sensitivity analysis, it is inferred that as the PV systems and batteries drop down, the DC system becomes more economical. The same is the case with EIR and discount rates. As the discount rates and EIR increases, the DC system favored over AC system in both cases. The savings are as high as 65%. As more products are produced and consumed, the DC system would become a preferred power source over the AC system.

Recommendation for future research. Future opportunities include conducting real-time data analysis research in which live data can be monitored over time, and better results can be obtained. The lack of long-term data is complicated in predicting the exact outcome using this power source. Some of the appliances do not have an equivalent DC device. Though they are available, and their cost is unclear. With better data availability, more accurate predictions can be carried out, and the assumptions made can also be verified.

One more critical component that has not been dealt with in his research is the wiring and the apartment's voltage. Each appliance works at different voltages.

Therefore, the need for a universal voltage regulator and a circuit breaker might arise to enhance the system's safety standards. Further research needs to be carried out to predict better results.

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BIOGRAPHICAL SKETCH

Venkatesh Kumanan was born in Chennai, India. He completed his bachelor's in civil engineering. He was selected for pursuing a master's in structural engineering through GATE (Graduate Aptitude Test in Engineering) Scholarship after his under graduation. It was a federally funded scholarship. During his master’s program, he did a piece of work on "Evaluation of Response Reduction Factor for moment-resisting frames." Post his master's in structural engineering, and he began his new construction management journey in his master's degree. During his earlier days at M.E. Rinker, Sr.

School of Construction Management, he developed an interest in cost-effective, sustainable buildings and infrastructure construction. He dreams of making it big in the infrastructure industry.

Apart from studies, Venkatesh was a part of a non-profit organization called

ASHA. In which he used to volunteer for various sports events and other charity works.