|Title||Electricity production and cooling energy savings from installation of a building-integrated photovoltaic roof on an office building|
|Publication Type||Journal Article|
|Year of Publication||2013|
|Authors||Ban-Weiss, George, Craig P. Wray, William W. Delp, Peter Ly, Hashem Akbari, and Ronnen M. Levinson|
|Journal||Energy and Buildings|
|Pagination||210 - 220|
|Keywords||Advanced Technology Demonstration, building design, Building heat transfer, cool roof, energy efficiency, Energy Performance of Buildings, energy savings, Energy Usage, energy use, Heat Island|
Reflective roofs can reduce demand for air conditioning and warming of the atmosphere. Roofs can also host photovoltaic (PV) modules that convert sunlight to electricity. In this study we assess the effects of installing a building integrated photovoltaic (BIPV) roof on an office building in Yuma, AZ. The system consists of thin film PV laminated to a white membrane, which lies above a layer of insulation. The solar absorptance of the roof decreased to 0.38 from 0.75 after installation of the BIPV, lowering summertime daily mean roof upper surface temperatures by about 5 °C. Summertime daily heat influx through the roof deck fell to ±0.1 kWh/m2 from 0.3–1.0 kWh/m2. However, summertime daily heat flux from the ventilated attic into the conditioned space was minimally affected by the BIPV, suggesting that the roof was decoupled from the conditioned space. Daily PV energy production was about 25% of building electrical energy use in the summer. For this building the primary benefit of the BIPV appeared to be its capacity to generate electricity and not its ability to reduce heat flows into the building. Building energy simulations were used to estimate the cooling energy savings and heating energy penalties for more typical buildings.