Computer Evaluation of the Solar Energy Potential in an Urban Environment Paper by Jean-Louis Scartezzini, MarylèneMontavon, and RaphaëlCompagno Solar Energy and Building Physics Laboratory (LESO-PB) and Swiss Federal Institute of Technolgy in Lausanne (EPFL). Presented by Shepard Daniel, International Studies, GEOG 370, February 26, 2008 Renewable Energy Applications in the Face of Climate Change: Solar Energy Potential

The study seeks to address the growing need for renewable energy infrastructure … Problem The increasing quantity of greenhouse gases in the atmosphere and resulting global warming and climate change effects necessitate the large scale application of alternative, renewable energies, such as solar energy. This study conducts a preliminary assessment for the potential of solar technologies in urban areas, by using computer models to examine urban sites in Switzerland. Hypothesis There is potential for a drastic reduction of the energy consumption of this urban site, as targeted within the framework of the "2000 Watts Society" project.

METHODS, DATA, TEST: Site: The model was known as “Klein Basel – Matthäus,” representative of the Swiss urban environment, with an area of 59 hectares Methods Overview: Spatial distributions of solar irradiation and daylight fluxes over the overall building facades and roofs were calculated using ray tracing simulation techniques. First, researchers assessed for most appropriate technologies (passive and active solar, photovoltaics and daylighting) using the following factors: – Climate data of the site of Basel – A site ground relief – solar energy and daylight flux distributions on the building facades and slanted roofs – relative fraction of appropriate building surfaces, appropriate surface locations, etc. Second, researchers assessed the performance indicators for each type of technology based on: – Irradiance and Illuminance statistical distributions – The relative fraction of building surfaces appropriate for the different specific solar technologies – Polar diagrams showing the main orientation of the building facades By assuming minimal required irradiation or illuminance thresholds for each specific technology, the corresponding fractions of building facades and roofs were determined. Resource Potential and Appropriate Technologies

RESULTS: It was shown that about half of the building “envelope area” (facades and roofs) is appropriate for the use of solar technologies despite the urban character of the site (building obstructions, effect of urban canyon). Solar TechnologyPassiveActivePVDaylighting Relative fraction of appropriate: FAÇADE AREA: ROOF AREA: 48.7% % 92.2% 1.3% 49.4% 51.1% - Required Minimal Threshold for FAÇADES: ROOFS: 117 [kWh/msq] [kWh/msq] 600 [kWh/msq] 800 [kWh/msq] 1000 [kWh/msq.] 10 [kLux] - Table 1: Relative fraction of building facade/roof areas appropriate for a given solar technology

Conclusions These preliminary results indicate that the perspective of curbing greenhouse gas emissions through use of renewable energies, such as solar energies, in large cities can reasonably be envisioned for the future.