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