A barrier to the widespread application of building integrated photovoltaics (BIPV) is the lack of validated predictive performance tools. Architects and building owners need these tools in order to determine if the potential energy savings associated with building integrated photovoltaics justifies the additional capital expenditure. The National Institute of Standards and Technology (NIST) seeks to provide high quality experimental data that can be used to develop and validate these predictive performance tools.The temperature of a photovoltaic module affects its electrical output characteristics and efficiency. Traditionally, the temperature of solar cells has been predicted using the nominal operating cell temperature (NOCT), which can be used in conjunction with a calculation procedure to predict the module's temperature for various environmental conditions. The NOCT procedure provides a representative prediction of the cell temperature, specifically for the ubiquitous rack-mounted installation. The procedure estimates the cell temperature based on the ambient temperature and the solar irradiance. It makes the approximation that the overall heat loss coefficient is constant. In other words, the heat flux on the panels (solar irradiance) is linearly related to the temperature difference between the panel and the environment.The heat transfer characteristics of a rack-mounted PV module and a BIPV module can be quite different. The manner in which the module is installed within the building envelope influences the cell's operating temperature. Unlike rack-mounted modules, the two sides of the modules may be subjected to significantly different environmental conditions.This paper presents a technique to compute the operating temperature of cells within building integrated photovoltaic modules using a one-dimensional steady state heat transfer model. The resulting predictions are compared to measured BIPV cell temperatures for two single crystalline BIPV panels. One panel is installed with thermal insulation attached to its rear surface. The second panel is installed without thermal insulation. Finally, the results are compared to predictions using the nominal operating cell temperature (NOCT) technique.
Proceedings Title: International Solar Energy Conference | | Solar Engineering Conference 2001 | ASME
Issue: No. 3
Conference Dates: April 21-25, 2001
Conference Title: American Society of Mechanical Engineers
Pub Type: Conferences
BIPV, Building Integrated Photovoltaics, NIST, NOCT, performance prediction, temperature, temperature model