Photovoltaic potential in urban areas

When fighting the climate change in urban areas, using solar power can be one of the most effective approaches. During the last decades, the energy coming from the sun is used increasingly and more efficiently. There are various ways for harvesting energy from the sun, including photovoltaics (PV), thin film solar cells, quantum dot cells, concentrating PV and thermal solar power stations (Rhodes, 2010).

There are two basic categories of technologies that convert sunlight into power: solar photovoltaic (PV) modules convert sunlight directly into electricity, and solar thermal power systems use focused solar radiation to produce steam, which is then used to turn a turbine producing electricity (Herzog, et al. 2001). 

Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics has declined steadily since the first solar cells were manufactured (Swanson, 2009). Therefore, solar power in the cities is mostly used by integrating photovoltaics to the building’s roofs or facades.

According to Barker, et al. (2001), geometrical factors that influence photovoltaic potential in an urban planning, are the ratio of a building’s roof surface area and the distance to the neighboring buildings. When roof surface area is large and buildings are spaced tightly, the roof mounted photovoltaics have bigger potential than façade photovoltaics. In case of small roof surface and wide spacing between the neighboring buildings, it is recommended to use façade photovoltaics.

Research made by Cheng et al. (2006), investigates how photovoltaic potential is influenced by the disposition and variation of height of buildings. Research compares four built forms that correspond to different horizontal and vertical layouts, either uniform or random (see Fig. 1).

 Source: Cheng et al. (2006)

According to Cheng´s (Cheng, et al. 2006) results, PV potential is more influenced by a vertical randomness, depending on the site coverage. PV potential is higher in low site coverage setting as it allows better solar access on facade. On the other hand, high site coverage and vertical randomness creates overshadowing of roof area. Horizontal randomness does not have significant influence on PV potential.

As the researches show, PV potential is limited by several factors in urban areas. Therefore, usage of PV systems can not represent a comprehensive solution when changing the source of power in cities. Yet, using PV systems as efficiently and extensively as possible is a crucial approach to reduce greenhouse gas emissions and fight the climate change.

 

Anni Oviir
REAP, HCU Hamburg

Rhodes, CJ. (2010.) Solar energy: principles and possibilities. Sci Prog. 2010;93 pp 37-112.

Herzog, A., Lipman, T., Kammen, D. (2001). Renewable Energy Sources. Encyclopedia of Life Support Systems (EOLSS). Part 4C. University of California

Swanson, R. M. (2009). Photovoltaics Power Up. Science 324 (5929): 891-892.

Barker, M., Blewett-Silcock,T., Eising, K., Gutschner, M., Kjellsson, E., Lutter, E., Nowak, S., Steemers, K., Tondi,G. (2001). Solar Electricity Guide. New Solutions in Energy Supply. Institut Credá. Spain

Cheng, V., Steemers, K., Montavon, M., Compagnon, R. (2006). Urban Form, Density and Solar Potential. PLEA2006 - The 23rd Conference on Passive and Low Energy Architecture, Geneva, Switzerland, 6-8 September 2006