Potential analysis for rooftop farming and rooftop PV in New Cairo

Transcription

1 Potential analysis for rooftop farming and rooftop PV in New Cairo - A GIS based suitability model - Manual Area model Prepared by: Lisa Kaltenbach and Jingsui Huang Supervision from: Hany Abo El Wafa Prof. Dr. Stephan Pauleit Created within the Master s Thesis of Lisa Kaltenbach (2017) and Jingsui Huang (2017), M.Sc. Environmental Planning and Engineering Ecology, TUM

2 Table of contents 1 Glossary General information Introduction Model aim and usage Model concept and scope Input data Building footprint data Rooftop structures Rooftop holes Results Transformability Technical information Employed Software Model parameters Model Structure Part I: Building Type selection Part II: Attribute Information Integration Part III: Shadow Simulation Part IV: Available Area Calculation RPVF toolbox Running the Model Running Duration Model output Credits Use Limitations Appendix Area model Area_Sub model Bldg_Type and Choose_Multiple_Values_Field sub-model Open Area model

3 1 Glossary RPVF Area F PV FC GIS TIN.gdb Name of the ArcGIS Rooftop Photovoltaics and Farming toolbox Area model of the RPVF toolbox to obtain available shadowed and nonshadowed rooftop area Farming model in the RPVF toolbox to analyze bed layout and estimate crop yield PV (Photovoltaic) model in the RPVF toolbox to estimate solar energy output Feature Class, a collection of geographic features with the same geometry type, the same attributes, and the same spatial reference Geographic Information System, a system designed to capture, store, manipulate, analyze, manage, and present spatial or geographical data Triangulated Irregular Network, a digital data structure used in a GIS for the representation of a surface Ending for geodatabase 2 General information 2.1 Introduction This manual is prepared to give general and technical information about the Area model. A GIS-based model was developed to assess the potential for rooftop farming and rooftop photovoltaics in New Cairo, Egypt. The model calculates and visualizes usable rooftop area according to building footprint data. The model distinguishes between usable shadowed and non-shadowed area and lets the user select input files and building types. The model is the base for a farming (F) and a photovoltaic (PV) sub model. The F and PV models calculate according to certain criteria bed and PV cell layouts and achievable yields regarding crop produce and electricity generation. 2.2 Model aim and usage The model aims to analyze rooftop space available for farming and/or solar power. City planners can use the model in the city planning and development process. It shall ease the the urban planning process of more sustainable solutions for electricity and food generation within urban areas. 2

4 2.3 Model concept and scope The created model is a GIS-based model. The software used to create this model is ArcGIS The model is built on the model builder environment of the software. To edit the model, the user has to use the ArcGIS model builder. The model comprises a main part to determine non-usable area and usable non-shadowed area and a sub part for the calculation of the shadowed area. Shadows are generated by rooftop structures and shadowed area is unusable for PV. Figure 1 shows a graphical representation of the conceptual model. The Area model selects shadowed and non-shadowed rooftop space available for rooftop farming and/or PV. The model allows the user to select building type(s) upon which it creates Feature Classes (FCs) showing the available shadowed and non-shadowed area on each roof. It lets the user define a buffer distance along the edges of the rooftop and the holes to ensure safety and accessibility. A sub-model (Area_sub) iterates through different phases or sections of the building blocks to simulate the shadows on the rooftops created by rooftop structures. The model creates a Scratch geodatabase to store intermediate data and an Output geodatabase to store output data. The outputs of the Area model serve as input files for the PV and F model. The output files are saved to the Output.gdb. 3

5 Figure 1: Conceptual model of the ArcGIS Area-model (own illustration) a) TIN=Triangulated Irregular Network b) i= 1,2,3,4,5,7,8,9,10 (Phases where buildings stand) c) Date and Time: Dec 21 st 2016, 10 am 2 pm, set for Egyptian standard time 4

6 Spatial scope For the purpose of this research the model calculates the potential for the district of Al Rehab in New Cairo, Egypt (Figure 2). The model is transferable to other cities and lets the user select input parameters. The model is not limited to a specific area. Figure 2: Study area of this research (own illustration created with ArcGIS 10.4) 5

7 2.4 Input data The output of the model and its accuracy is highly dependent on the input data. For this research limited data was available and data was created using ArcGIS 10.4 and google earth imagery. Following data was created: Building footprint data Figure 3 visualizes the building footprint. All buildings were processed based on data provided by the GIS portal of Digital Egypt and Google Earth imagery from April The created building footprint lacks the footprint of phase 6 given that buildings in this phase are still not constructed. Figure 3: Visualization of the building footprint for Al Rehab City (created with Google earth imagery and ArcGIS 10.4) Rooftop structures Figure 4 visualizes the rooftop structures such as chimneys, any roof installations (not including satellite dishes) or praying towers. The file was created and processed with ArcGIS 10.4 based on Google Earth imagery. 1 Digital Egypt (2014): Geodata Innovations, URL: Rehab/GIS/RehabEnglish.html, Retrieved September 28,

8 Figure 4: Visualization of above ground roof structures (created with ArcGIS 10.4) Rooftop holes Figure 5 visualizes the rooftop holes. The file was created and processed with ArcGIS 10.4 based on Google Earth imagery. Figure 6 shows a zoomed in footprint representing building footprint, holes and structures. Figure 5: Visualization of the rooftop holes (created with ArcGIS 10.4) 7

9 Figure 6: Zoomed in visualization of building footprint, roof structures and holes Building footprint Roof holes Roof structures 2.5 Results Figure 7 shows visual examples of the results for the study area of Al Rehab. The model generates one output for shadowed and one for non-shadowed area 8

10 Figure 7: Visualization of the Area model results. Building footprint Roof holes Roof structures Available non-shadowed area Available shadowed area Figure 8 shows an excerpt of the table of attributes for the non-shadowed area. It includes the building ID, the height and floor no. of the building, the phase in which it is located and the length and size of the available shadowed/ non-shadowed area in m 2. Figure 8: Excerpt of the non_shadowed table of attributes resulting from running the Area-model. The Shape_Area column lists the available area in m 2 9

11 2.6 Transformability This GIS model can be used to assess the potential for rooftop farming and /or PV in other cities. The input files have to be changed by the user and the input parameters have to be set according to existing criteria. The time and date for the shadow volume calculation has to be changed in the model builder. If needed also the tools of the model can be edited and replaced to best suit the local conditions and requests. 3 Technical information This technical section is prepared to provide the technical information and instructions of how to run and edit the Area model in the RPVF toolbox. 3.1 Employed Software The software that was used in this model is ArcGIS The model is built in the model builder environment of the software. The model can be run by opening it in the ArcMap catalog and can be edited in the ArcMap model builder. The 3D Analyst extension should be enabled to run the tool. In case of working with an older version of ArcGIS the model has to be saved in this version to be able to use it. 3.2 Model parameters The model parameters of the Area model are listed in Table 1. Table 1: Model parameters Area model S/N Model parameter Explanation Data Type 1 GeoDB The file geodatabase where the input feature classes are located 2 fp Feature Class showing the building footprint; created using google earth imagery and the polygon tool provided by ArcGIS Workspace Feature Class 10

12 3 struc Feature Class showing the rooftop structures; outlined using the ArcGIS polygon tool 4 hole Feature Class showing the rooftop holes; outlined using the ArcGIS polygon tool 5 Building_Type The Building Type e.g. Residential (Villa, Apartment ), Commercial A list of unique values read from the Type field of <<fp>> ; the user can select one or multiple building type(s) when running. 6 Edge_buffer The buffer distance (in meters) along the roof edges and hole edges for safety and accessibility Feature Class Feature Class Multiple Value Double If the user has input data in other formats, the data has to be converted and imported to a File Geodatabase. Topology should be validated prior to running the model. The required attribute information in the input FCs is listed in Table 2. The field names when using own input data has to match the ones listed in the table. Table 2: Required Attribute Information of the Input Feature Classes FC Field Type Description fp ID_bldg short Unique number of each building. Phase short Temporal phase or spatial section. Type text The type of the building, e.g. Private vs. Public, Residential vs. Industrial, etc. Use any single value (e.g. Building) for this attribute in case of a single building type. Floors short The number of floors above the ground. Height float Ground-to-roof height. (m) hole N/A n/a Only geometry and location are required. struc Sh float The height of the structure above the roof. (m) 11

13 3.3 Model Structure The model consists of a main model Area and two sub-models Area_sub and Bldg_Type. An overview of the model (Area, Area_sub, Bldg_Type) is shown in the appendix. The Area model uses three input FCs saved to a GeoDB to generate the necessary output files for the PV and F model. The Area model consists of four main processes: 1. Building Type selection (Part I) 2. Attribute information integration (Part II) 3. Shadow simulation (Area_sub) (Part III) 4. Available area calculation (Part IV) Part I: Building Type selection In the first model operations the model imports the FCs and selects the desired building type(s) (Figure 9). The model reads the folder path where the input File Geodatabase (GeoDB) is located and creates two more File Geodatabases: Scratch.gdb for storing the intermediate files and Output.gdb for storing the essential and final results of the Area model. For the selection of building types, a Bldg_Type sub-model was created. Figure 9: Area model Part I (ArcGIS model builder) Bldg_Type sub-model: The Bldg_Type sub-model reads the values of the Type field in <<fp>> and generates a list of unique values for the user to choose. It then produces the <<fp_type>> Feature Class and saves it to the Output.gdb. The <<Choose_Multiple_Field_Value_Sub>> is a sub-model of the Bldg_Type model based on a Choose Multiple Field Values Script tool provided by ArcGIS 12

14 Online 2. It includes a script tool and its own sub-model to iterate through the field values. Figure 10 shows a graphical representation of the Bldg_Type and Figure 11 the Choose_Multiple_Field_Values model type selection Figure 10: Bldg_Type sub-model (ArcGIS model builder) Figure 11: Choose_Multiple_Field_Value_Sub model (ArcGIS model builder) Following script is used to create the Choose_Multiple_Field_Value_Sub model: # Import system modules import arcpy # Set the parameters InputFeatureClass = arcpy.getparameterastext(0) InputField = arcpy.getparameterastext(1) InputValue = arcpy.getparameterastext(2) arcpy.setparameter(3, InputValue) 2 Retrieved December 10,

15 3.3.2 Part II: Attribute Information Integration In a further operation the model spatially joins <<fp_type>> and <<struc>> to allocate the roof structures to the buildings. The information from the column <ID_bldg> in <<fp_type>> is joined to the features in <<struc>>. After the Spatial Join, the model adds a new field with the name <Th> of the data type Float to the attribute table of <<struc_fp_join>>. <Th> indicates the total height of the buildings including the roof structures. The model uses following field calculator function: Th=Heigth+Sh. The Area_Sub model (see Shadow Simulation) needs a TIN surface as input data. Thus the model calculates the <Max_Th> using the Summary Statistics option and joins the output to <<fp_type>>. <Max_Th> indicates the height of the highest point of each building. The model merges <<struc_fp_join>> and <<fp_type>> resulting in <<fp_struc_merge>>, containing the information and geometry of all the structures and footprints. The structures and footprints in the merged feature class can be distinguished by the fields <Sh> and <Max_Th> (Table 3). The model only feds the structures and footprints of buildings with structures into the Area_Sub as input. The elements are selected using the expression: Sh IS NOT NULL OR Max_Th IS NOT NULL. Figure 12 and Figure 13 show graphical representations of Part II of the Area model. Figure 12: Area model: Part II a) (ArcGIS model builder) 14

16 Figure 13: Area model: Part II b) (ArcGIS model builder) Table 3: Attribute Difference of elements in <<fp_struc_merge>> Elements Sh Max_Th Structures IS NOT NULL IS NULL Footprints of the buildings with structures IS NULL IS NOT NULL Footprints of the buildings without structures IS NULL IS NULL Part III: Shadow Simulation The Area_Sub model was created to simulate the shadows generated by rooftop structures. The sub-model runs on the Sun Shadow Volume tool and simulates shadows at a given date and time for multipatch features. The Extrude Between tool extrudes the structures between the roof height and the total height using corresponding TIN surfaces. To create these two TIN surfaces, the Select tool selects the footprint element using the expression Sh IS NULL and the structure element using the expression Max_Th IS NULL. The Create TIN process produces the roof_tin surface based on the footprint element and the Height field (Figure 16), as well as struc_tin surface based on the structure element and the <Th> field (Figure 17). The extruded MultiPatch features (<<struc_mp>>) (Figure 18) lost the projection information. It is added using the Define Projection tool. The output is then used as input for the Sun Shadow Volume tool. Figure 14 and Figure 15 show graphical representations of the Area_Sub model. 15

17 Figure 14: Area_Sub Model first part (ArcGIS model builder) Figure 15: Area_Sub Model second part (ArcGIS model builder) Figure 16: Sample Building: Roof_TIN Showing the Roof Surface 16

18 Figure 17: Sample Building: Struc_TIN Showing the Structure Surface Figure 18: Sample Building: Extrusion of the Structures Between the TIN Surfaces to Form MultiPatch Features The Area_Sub model simulates the shadow variations during the day on December 21 st hourly from 10 am to 2 pm (in this application set for Egyptian standard time), generating a total of 5 shadow profiles. Date and time can be changed by the user in the model builder environment. Figure 19 shows a representation of the settings window when opening the Sun Shadow Volume tool. 17

19 Figure 19: Sun Shadow Volume tool settings The Area_Sub model generates MultiPatch features representing the shadows as solids. The shadows intersect with the buildings below and some nearby structure features (Figure 20). To extract the shadowed surface on the roofs, the Intersect 3D tool is used. The tool extracts the shared part of the 3D MultiPatch features or the shared surfaces between the features. There are no shared surfaces between the generated shadow volume features and the roofs, as the roofs slice the shadow volume. Therefore, an extrusion of the <<fp_type>> features from the roof level, <<fp_mp>>, is required, which requires two TIN surfaces: one representing the roof surface at the roof height and the other representing the roof surface at the maximal building height. The roof_tin in Figure 16 serves as the roof surface. The second required TIN surface is created based on the maximal value among the <Th> values on each rooftop, top_tin (Figure 21). The Intersect 3D tool then extracts the shared volume of the MultiPatch features and the shadow volumes (Figure 22). The bottom surface of the extracted volume is the shadow cast on the rooftop, extracted using the MultiPatch Footprint tool (Figure 23). The resulting shadow files (output Area_Sub) are fed back into the Area model for further processing. 18

20 Figure 20: Sample Building: Sun Shadow Volume (Grey) Figure 21: Sample Building: Top_TIN (Purple) and <<fp_mp>> (Red) 19

21 Figure 22: Sample Building: <<fp_sh_intersect>> (Light Grey) Figure 23: Sample Building: Shadowed Area (Purple) The Intersect 3D tool requires much computing capacity and has a relatively high running duration. The tool may crash or get stuck in case of an input with a large number of features. To prevent possible failures, the whole shadow simulation process is built with an iteration, iterating through the Phase field values from the input <<fp>>. The computer simulates the shadows for a section of the whole area at a time. 20

22 3.3.4 Part IV: Available Area Calculation First operation to calculate the available area is a Spatial Join to associate the attribute tables of <<hole>> and <<fp>> letting the <<hole>> features obtain the ID_bldg information. A buffer distance (in meters) around the holes and inside the roof edges is defined by the user resulting in the generation of unusable buffer zones (<<hole_buffer>>, <<fp_buffer>>). A Merge of the buffer zones, <<hole>> and <<struc>> combines the non-usable roof area (<<non_usable>>). Figure shows a graphical representation of Part IV a) of the Area model. Figure 24: Area model: Part IV a) (ArcGIS model builder) The shadow files from the different sections or phases are merged to show the shadowed area for the whole study area. After fixing the projection system, the model erases the non-usable area from the shadowed area to obtain the usable shadowed area (<<shadow_nd>>). The model then repairs the geometry (Repair Geometry) and dissolves the shadowed area (Dissolve) to avoid overlapping shadows from different time periods. The non-usable area and the usable shadowed area are then merged to form <<non_use_shadow>>, indicating the area not suitable for PV. The model then erases the <<non_use_shadow>> from <<fp_type>> to get the usable non-shadowed area. Another Repair Geometry and Dissolve gives the the final output for available non-shadowed area: <<non_shadow>>. Figure 25 shows a graphical representation of Part IV b) of the Area model. 21

23 Figure 25: Area model: Part IV b) (ArcGIS model builder) 3.4 RPVF toolbox It is recommended to copy the whole RPVF toolbox (RPVF.tbx) on your drive. Table 4 represents a list of all models, sub-models and tools included in the toolbox. Table 4: RPVF Toolbox S/N Part Model/Tool 1 Area Area Area_Sub 2 F F F_Sub Parallel script tool 3 PV PV PV_Sub Bldg_Type Choose_Multiple_Field_Values Choose_Multiple_Field_Values script tool All input data for Al Rehab city is available in the Geo_DB folder. Figure shows the RPVF toolbox in ArcCatalog. 22

24 Figure 26: RPVF toolbox (ArcCatalog) Details on the F part and the PV part are given in different manuals prepared by Lisa Kaltenbach (2016, Farming) and Jingsui Huang (2016, PV). 3.5 Running the Model The user can run the model in ArcCatalog or in ArcMap. In ArcCatalog navigate to the RPVF toolbox and double click on the Area model. In ArcMap add the RPVF toolbox to the ArcToolbox column and double click on the Area model. After selecting the corresponding File Geodatabase and FCs, select the desired building type(s), and define the buffer distance (Figure 27). 23

25 Figure 27: Model parameters input window Area model (ArcMap) A detailed description on the fields is given in the appendix. To run the model, click OK after setting the parameters. 3.6 Running Duration The duration depends on the number of buildings to be processed and can take several minutes up to more than an hour. The running duration for Al Rehab City takes approximately 1 hour and 15 minutes depending on the processing speed of the computer used. 3.7 Model output The Area model creates two File Geodatabases (Scratch.gdb and Output.gdb) in the folder where the input GeoDB Geodatabase is located. The final output of the model are four FCs saved to the Output.gdb: <<fp_type>> (building footprint with buildings of desired type(s)) <<non_use_shadowed>> (non-usable area and shadowed area) <<shadowed>> (shadowed area) <<non_shadowed>> (non-shadowed area) 24

26 4 Credits Authors: Lisa Kaltenbach and Jingsui Huang, December 2016, Technische Universität München. The input data was compiled by the Al Rehab City GIS (Digital Egypt) online portal and own digitalization using google earth imagery. The roof structures and holes were digitized based on Google Earth imagery. 5 Use Limitations There are no access and use limitations for this model. The model was created within the the Master s Thesis Assessing the potential of rooftop photovoltaics and rooftop farming in Greater Cairo, Egypt using a GIS-based suitability model: A case study of Al Rehab (Technische Universität München, M.Sc. Environmental Engineering, Jingsui Huang, 2017) and the Master s Thesis The potential of rooftop farming and solar power in New Cairo, Egypt A local perspective and GIS-based suitability model: the case study of Al Rehab City (Technische Universität München, M.Sc. Environmental planning and engineering ecology, Lisa Kaltenbach, 2017). 25

27 6 Appendix 6.1 Area model Figure 28: Area model (ArcGIS model builder) 26

28 6.2 Area_Sub model Figure 29: Area_Sub model (ArcGIS model builder) 6.3 Bldg_Type and Choose_Multiple_Values_Field sub-model Figure 30: Bldg_Type sub-model (ArcGIS model builder) 27

29 Figure 31: Choose_Multiple_Field_Value_Sub model (ArcGIS model builder) 6.4 Open Area model 1. Field 1 GeoDB: Input geodatabase containing all files needed as input data (here: Rehab.gdb); change folder by clicking on the folder connection symbol, then browse to correspondent folder and select it 2. Field 2 fp: Input building footprint 3. Field 3 struc: Input Feature Class representing the rooftop structures 4. Field 4 hole: Input Feature Class representing the rooftop holes 5. Field 5 Building_Type: Select from the list created 6. Field 6 Edge_buffer: Enter the buffer distance in meters 28