The potential for PV installation in residential buildings in dense urban areas

כנס המדענית הראשית משרד האנרגיה

2018ביוני 6

פוטנציאל סולארי על מבנים בסביבה עירונית

וולטאיות לייצור חשמל בבנייני מגורים באזור עירוני צפוף-הפוטנציאל להקמת מערכות פוטו

קלוגאיתי ' אביתר אראל ופרופ' פרופ וולקןעדי ' גב, ר מיכאל דורמן"ד

גוריון בנגב-אוניברסיטת בן

021-11-215' חוזה מס

Ben-Gurion University of the Negev (2018) 2

The cost of PV is going down…

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but building heights are going up

")רכבת("בניינים טוריים

"H"בנייני

בנייה רוויה

מגדלי מגורים

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Objectives

a) to estimate the potential for electricity generation by building-integrated PV in dense urban locations, accounting for shading by adjacent structures

b) To compare the solar potential of different residential building types in Israel

c) to analyze the equivalent electricity output of combinations of BIPV and solar water heating in buildings, and to evaluate strategies for incentivizing the most promising ones

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Barriers to building-integrated solar energy

SWHs required by building code since 1970 in all residential buildings of less than 24 meters in height, and since 2012 – in the upper 7 stories of high-rise buildings as well.

Shading by adjacent buildings

Sub-optimal orientation

Insufficient roof area

Barriers: Flat plate solar collector for DHW

Photo: Oded Potchter

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Can rooftop PV cover our electricity needs? Gagnon et al, 2016

Potential in Israel: 32%

Vardimon, 2011.

Sunlight not the only factor – current electricity consumption and building form important, too.

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Gross carrying capacity (PV electricity)

Annual insolation at optimal tilt

- Tel Aviv: ~2200 kWh/m2

- Freiburg: ~1400 kWh/m2

- Pittsburgh: ~1500 kWh/m2

Per capita residential electricity use

- Israel: 2000 kWh/year

- Germany: 1730 kWh/year

- USA: 4517 kWh/year

PV conversion efficiency (system):

15% Current ‘gross’ population density Tel Aviv: approx. 8,000 persons/km2

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Modelling insolation on buildings in the city

Free, open-source tool to assess how building configurations affect insolation and PV installation potential on building envelopes (roofs and facades) in complex, irregular urban environments.

Dorman et al, 2018

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Case study area (Rishon Leziyon): building types

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Measures of density

Dwelling density:

No. of units per 1,000 m2 site area

Ground space index:

Built fraction of site

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Insolation on one building

Building height (m)

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Annual insolation on walls

Facades do not receive much sunlight…

Faiman et al, 2000; Dorman et al, 2018

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Façade suitability for BIPV installation

Façade area with annual solar potential of at least 40% of direct solar radiation on an exposed horizontal rooftop.

…now accounting for shading

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Annual direct radiation on facades in comparison to (arbitrary) threshold of 40% of flat roof

Façade vs. roof

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The solar potential of different urban typologies a. solar PV per dwelling

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The solar potential of different urban typologies b. solar PV per building site

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DSWH closed loop DSWH open loop PV 16% PV 17%

Installation cost 4,770 4,080 40,000 40,000

Maintenance 20 years 4,770 8,160 3,000 3,000

Installation fee - - 2,000 2,000

Annual fee - - 1,000 1,000

NPV @2% 10,343 7,429 5,753 9,795

PV vs solar hot water

All costs in NIS, 2017 data

Price of electricity: 53.94 agorot/kWh

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Discussion

Substantial differences among the urban typologies, which affect solar potential:

Area of rooftop and facades

Orientation of the facades

Location of the building relative to adjacent structures

Low-rise but dense typologies (e.g. row houses) have the highest solar potential, per apartment and per site

Façade PV has much lower output per unit, but can contribute substantially to some buildings (e.g. towers)

Roof PV soon to be more economical than solar water heaters (but has a lower energy utilization factor overall)

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Further work

• Complete analysis with diffuse radiation estimation (Sky View Factor assessment)

• Representation of shading elements such as urban vegetation

• Complex building structures such as windows and balconies (requires DSM data)

• Accounting for the effect of panel temperature on the panel output

• Complete techno-economic analysis of façade-integrated PV

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Dorman M., Vulkan A., Erell E. and Kloog I. shadow: R Package for Geometric Shadow Calculations in an Urban Environment. Submitted, The R-Journal.

Vulkan A., Kloog I., Dorman M. and Erell E. (2018). Modelling the potential for PV installation in residential buildings in dense urban areas. Energy and Buildings, 169: 97–109. https://doi.org/10.1016/j.enbuild.2018.03.052

Publications

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Faiman D., Feuermann D., Ibbetson P., Medwed B., Zemel A., Ianetz A., Liubansky V., Seter I. and Souraqui S. (2000). PV systems for Israel’s cities: How large should they be? A Design Guide. Research Report # RD-24-99, Israel Ministry of National Infrastructure.

Gagnon P., Margolis R., Melius J., Phillips C. and Elmore R. (2016). Rooftop Solar Photovoltaic Technical Potential in the United States: A Detailed Assessment. National Renewable Energy Laboratory Technical Report NREL/TP-6A20-65298. www.nrel.gov/publications

Vardimon, R. (2011). Assessment of the potential for distributed photovoltaic electricity production in Israel. Renewable Energy 36:591-594.

References

Prof. Evyatar Erell

The Jacob Blaustein Institutes for Desert Research Ben-Gurion University of the Negev

Israel

erell@bgu.ac.il

http://www.bgu.ac.il/~erell

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Direct solar radiation: shading

Free, open-source tool to assess how building configurations affect insolation and PV installation potential on building envelopes (roofs and facades) in complex, irregular urban environments.

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Diffuse radiation: sky view factor calculation