Mastertheis Ana Gonzalez Quintairos SENDEDVERSION
Technische Universität Berlin
Master Thesis
Analysis of potential distribution and size of photovoltaic systems on rural rooftops
A contribution to an optimized local energy storage system with a remote sensing and GIS-based approach in Swabia, Germany
A thesis submitted in fulfilment of the requirements for the degree of Master of Science Environmental Planning
by
Ana González Quintairos Matriculation number: 349833
First Supervisor: Prof. Dr. Kleinschmit
Second Supervisor: Dr. Jochen Bühler
Faculty VI Planning-Building-Environment Geoinformation in Enviromental Planning
January 2015
In cooperation with Reiner Lemoine Institut gGmbH
Abstract
Abstract
This work studies the distribution of photovoltaic systems in rural areas. The aim of the study is to create a method which predicts the size and location of future photovoltaic systems on rooftops. Only very few authors have also attempted to use high-resolution images to quantify the suitable rooftop surface per building and the appropriated loca- tion of the panels and none of them have addressed the particular building distribution and typology of rural communities. Addressing rural areas has a tremendous importance in Germany where highest PV potential in Germany is expected. The methodology uses as inputs high-resolution aerial imagery, GIS building footprint from the Land-register map and the Bavarian database of photovoltaic systems. The method has been applied to the village of Freihalden (Bavaria) using two different type of images: official orthophotos from the Bavarian Land-survey Office and Google Earth™ orthophotos and the results on rooftop suitable area and on rooftop potential for PV have been compared with each other. The study area is located in Freihalden, Bavaria.
First, the current status quo was analysed, cross-referencing the files from the Bavarian register of photovoltaic systems and the cadastre data. These buildings were excluded from dataset in order to avoid assigning them as potential building for PV in the future. To calculate the spatial distributed potential of the installed photovoltaic power on roof- tops in the future, a pixel-based image analysis is performed on each image to identify suitable rooftop areas, roof obstructions and shadows. The output of the image classifica- tion analysis is converted to vector data and the potential suit-able area is assigned to each building. Rooftop orientation and average slope are spatially joined to each rooftop. The results together with the location in coordinates of each building are giving as input to the PV Calculator, developed by the RLI, to obtain the potential annual energy pro- duction of each building. Finally, the prognosis step predicts the likely PV-expansion pathway based on each rooftop PV potential and the scenarios of the German Energy Agency. The output of the method is stored in a database including the central coordi- nates of each building.
Freihalden was found to have 43 buildings with already PV systems in its rooftops which represented an already installed nominal power of 571 kWp. The classification of the Ba- varian land-register orthophoto concluded that 82% of the buildings in the community have adequate areas with more than 10 m2 suitable for PV, where as in the classification of the Google Earth™ orthophoto 78% of the buildings are considered to have adequate
i Abstract
areas for PV. In average 39% of total rooftop area is considered suitable for PV. This number can be used a rule-of-thumb for future studies in the area. The total PV tech- nical potential of Freihalden reaches the 3170 kWp. Individual building potential ranges from 1 potential kWp to 42 kWp and the specific yield varies from 980,1 to 763,1 kWp/kWh. From the 412 buildings composing the village, 98 will be required to installed new PV systems if the municipality has to fulfil its share on the Bavarian renewable en- ergy goals for 2030. The comparison shows that both airborne high-resolution orthophoto and high-resolution Google Earth™ are capable of delivering trustworthy results with 11% and 16% error respectably using open-source software.
The method developed in this study has been further used to estimate the PV potential and prognosis expansion pathway of two more municipalities in Bavaria supporting the research of the project Smart-Power-Flow at the Reiner Lemoine Institute.
ii Table of contents
Table of contents
Abstract ...... i Table of contents ...... iii List of figures ...... iv List of tables ...... vi List of maps ...... vi Abbreviations ...... vii Chapter 1 Introduction ...... 1
1.1 Background ...... 1 1.2 Context and objectives ...... 2 1.3 Structure of the thesis ...... 3
Chapter 2 State of the art ...... 4 2.1 Suitable rooftop area ...... 4 2.1.1 Constant-value methods ...... 5 2.1.2 Remote sensing methods ...... 6 2.1.3 3D/LiDAR methods ...... 7 2.2 Global solar radiation ...... 8 2.3 PV energy production ...... 10 2.4 Data availability ...... 13 2.5 Research approach and research questions ...... 16
Chapter 3 Methods ...... 17
3.1 Description of the study area ...... 17 3.2 Input data ...... 19 3.2.1 General cartography ...... 19 3.2.2 Land register map ...... 20 3.2.3 Official orthophotos from BVW ...... 21 3.2.4 Google Earth orthophotos ...... 22 3.2.5 Bavarian photovoltaic database ...... 23 3.2.6 Statistics per municipality ...... 23 3.3 Research design ...... 23 3.3.1 Data preparation ...... 25 3.3.2 Isolating building rooftops ...... 28
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3.3.3 Analysis of status quo ...... 28 3.3.4 Pixel-based classification ...... 29 3.3.5 Computation of total suitable area ...... 34 3.3.6 PV energy production ...... 35 3.3.7 Validation ...... 36 3.3.8 Prognosis of the most probable locations for PV systems ...... 37
Chapter 4 Results ...... 40 4.1 Status quo ...... 40 4.2 Suitable area computation ...... 42 4.2.1 Bavarian land-register orthophoto ...... 43 4.2.2 Google Earth images ...... 44 4.3 PV technical potential ...... 46 4.3.1 Bavarian land-register orthophoto ...... 46 4.3.2 Google Earth images ...... 47 4.4 PV prognosis expansion pathway ...... 48
Chapter 5 Discussion and conclusion ...... 50
5.1 Comparison of results ...... 50 5.2 Review of methodology ...... 52 5.3 Future research and outlook ...... 53 5.4 Conclusion ...... 54
Glossary ...... 55 References ...... 56 Appendix A: Findings in literature review ...... 60 Appendix B: Smarth Power Flow municipalities ...... 64 Appendix C : Accuracy assessments ...... 65 Appendix D : PV potential and expansion pathways ...... 68 Appendix E : Maps ...... 91
iv List of figures
List of figures
Figure 2.1. Components of solar radiation on a slope [31]...... 9 Figure 2.2. Definition of tilt ( ) and azimuth ( ) angles for PV applications...... 10 Figure 2.3. Effect of the azimuth and tilt on the energy yield of a PV panel [45] .... 11 Figure 3.1. Example of settlement category: rural (left), village (centre), suburban (right) [Source: Google Earth™ orthophotos] ...... 17 Figure 3.2 Village of Freihalden in Jettingen-Scheppach municipality ...... 18 Figure 3.3. Residential houses with different roof angles in Jettingen-Scheppach ..... 19 Figure 3.4 Extent of the four orthophotos from BVW...... 22 Figure 3.5 Flowchart for calculating PV potential for this study ...... 24 Figure 3.6. PDF land-register map provided by the regional network operator LVN (above) and land-register map after digitalization (below)...... 27 Figure 3.7 Orthophoto and building footprints before and after correction ...... 29 Figure 3.8 Detail of the obstruction, shadows, suitable and non-suitable areas of one household in Freihalden...... 30 Figure 3.9 Signature plots ...... 31 Figure 3.10 new signature plots after building categorization: red roofs (left), grey roofs (center) and black roofs (right) ...... 31 Figure 3.11 Histograms for band 1, band 2 and band 3 of grey roof image...... 32 Figure 3.12 Original orthophoto clipped by the building footprint (left) and classified output after supervised image classification (right) ...... 33 Figure 3.13 Building before (left) and after applying post-processing (right)...... 34 Figure 3.14 Determination of the rooftop area with roof inclinatio angle = 35º .... 34 Figure 3.15 German Energy Agency classes [5] ...... 38 Figure 4.1 Houses with installed rooftop PV systems (purple) in Freihalden ...... 41 Figure 4.2 Supervised image classification based on the BVW orthophoto ...... 43 Figure 4.3 Photovoltaic suitability map based on BVW orthophoto ...... 44 Figure 4.4 Supervised image classification based on Google Earth™ orthophoto ..... 45 Figure 4.5 Photovoltaic suitability map based on Google Earth™ orthophoto ...... 46 Figure 4.6 PV technical potential map based on BVW orthophoto ...... 47 Figure 4.7 PV technical potential map based on Google Earth™ orthophoto ...... 48 Figure 4.8 Prognosis expansion pathway based on BVW orthophoto ...... 49 Figure 4.9 Prognosis expansion pathway based on Google Earth™ orthophoto ...... 49 Figure 5.1 Comparison of image classification statistics ...... 50 Figure 5.2 Comparision of orthorectification on a small subset of Freihalden ...... 52
v List of tables
List of tables
Table 2.1 Classification of references according to its methodology ...... 5 Table 2.2 Available data sources and used data (green) for the master’s thesis ...... 14 Table 3.1 Correspondence of DXF features with Land register map´s elements ...... 26 Table 3.2 Class types ...... 32 Table 3.3 Input data in EVA PV Calculator ...... 36 Table 3.4 Jettingen-Scheppach in Dena network classes ...... 37 Table 4.1 Installed PV systems in Freihalden ...... 41 Table 4.2 Classification statisitics ...... 43 Table 4.3 Classification statistics ...... 45 Table C.1 Accuracy assessment red roofs in Bavarian land-register orthophoto ...... 65 Table C.2 Accuracy assessment grey roofs in Bavarian land-register orthophoto .... 65 Table C.3 Accuracy assessment black roofs in Bavarian land-register orthophoto ... 66 Table C.4 Accuracy assessment red roofs in Google Earth™ orthophoto ...... 66 Table C.5 Accuracy assessment grey roofs in Google Earth™ orthophoto ...... 66 Table C.6 Accuracy assessment black roofs in Google Earth™ orthophoto ...... 67 Table E.1 Prognosis and expansion pathway based on BVW orthophoto ...... 68 Table E.2 Prognosis and expansion pathway based on Google Earth™ image ...... 80
List of maps
Map 1 Freihalden status quo: installed PV systems ...... 91 Map 2 Building rooftop classification based on BVW orthophoto ...... 92 Map 3 Building rooftop classification based on Google Earth™ orthophoto ...... 93 Map 4 Suitable areas for PV based on BVW orhtophoto ...... 94 Map 5 Suitable areas for PV based on Google Earth™ orthophoto ...... 95 Map 6 Building PV technical potential based on BVW orthophoto ...... 96 Map 7 Building PV technical potential based on Google Earth™ orthophoto ...... 97 Map 8 PV expansion pathway based on BVW orthophoto ...... 98 Map 9 PV expansion pathway based on Google Earth™ orthophoto ...... 99
vi Abbreviations
Abbreviations
AC Alternating Current ALKIS Amtliches Liegenschaftskatasterinformationssystem (Official Real Estate Cadastre Information System) ATKIS Amtliches Topographisch-Kartografisches Informationssystem (Official Topographic-Cartographic Information System) BVW Bayerische Vermessungsverwaltung (Bavarian Land-survey Office) CAD Computer-aided Design DC Direct Current DEM Digital Elevation Model
DSM Digital Surface Model ESRA European Solar Radiation Atlas GIS Geographic Information System GW Gig watt HVAC Heating, Ventilation and Air Conditioning IEA International Energy Agency JRC Joint Research Centre of the European Commission kW Kilowatt
kWh Kilowatt hour kWp Kilowatt peak LVN LEW Verteilnetz GmbH (regional network operator)
LiDAR Light Detection and Ranging NASA National Aeronautics and Space Administration NREL National Renewable Energy Laboratory PV Photovoltaic
PVGIS Photovoltaic Geographical Information System RBT Representative Building Typology
STC Standard Test Conditions for PV modules
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Chapter 1
Introduction
The first chapter of this thesis introduces the relevant background information about renewable energy policies in Germany. Secondly, it frames the contexts of the thesis and specifies as well the master thesis objectives. The final research approach and the research questions are not presented here but in the next chapter after the literature research. Finally, the structure of the thesis concludes the chapter.
1.1 Background
The climate policy objectives of the European Union state that by 2020 a share of 20% of primary energy consumption in the European Union should be covered from renewable sources [1]. Germany has even more ambitious goals: the share of renewables in electricity supply must grow as high as 35% by 2020 and 80 % by 2050 [2]. Germany is trying to leave the fossil-nuclear age behind and therefore decentralised solar energy sources are expected to play a major role on the German sustainable power production market, in the near future.
Solar power in Germany has been increasing exponentially for the last 20 years, indeed. Ac- cording to the German Federal Network Agency, the total nominal power of photovoltaic (PV) installed in Germany rose from 17.4 GW in 2010 to 35.7 GW by the end of 2013 [3, 4] and it is expected to reach 42.4 GW of installed capacity by 2020 [5]. Last year, PV- generated energy totalled 29.7 TWh (Figure 1.1) and covered approximately 5.7 percent of Germany’s net electricity consumption [6] . Taken as a whole, renewable energy accounted for 29 percent of net electricity consumption, while the proportion of PV and total RE in Ger- many’s gross electricity consumption stood at 5 percent and 24 percent respectively [3].
Unlike other energy sources, when it comes to photovoltaic generation, small private photo- voltaic systems represent, in numerical terms and in terms of performance, the largest share [7]. The Frauhofer Institute (2014) [3] accounts for more than 1.4 million distributed solar PV generation plants just in Germany. With this figure, the installed PV capacity exceeds of all other types of power plants in Germany. These systems are mostly rooftop installations and usually feed into the low-voltage distribution networks, to which this work focus. As a conse- quence, loads and a reversal power flow direction occurs at certain hours in the year in many low-voltage distribution networks which threatens the network’s stability [7].
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Chapter 1. Introduction 2