An Assessment of the Building Integrated Photovoltaic Facade and It's Operational Mismatch Losses at Southampton University

摘要

Mismatch losses in photovoltaic (PV) arrays arise from electrical output differences in cells and/or modules. Theoretical studies characterising PV generation assume that all cells and modules in an array behave identically and operate under the same environmental conditions. In large arrays, especially building integrated photovoltaics (BIPV) this is not always the case. Variations in the manufacturing process and conditions of operation results in a reduction of the maximum power output of the generator, which is termed the mismatch loss. Mismatch is defined as "the power available from a combination of cells or modules being less than the sum of power of the individual cells or modules." A mismatch study is being conducted on the south facing, multi-configurable mono-crystalline 7.2 kW PV array installed on Building 2 of the Highfield Campus, Southampton University. The system consists of twenty-four strings that feed into two 3.7 kW inverters. The installation has a comprehensive monitoring regime allowing measurement of the string current-voltage characteristic as a function of environmental conditions. This characteristic is critical in identifying interactions that may have an effect on performance and hence mismatch losses. Array performance is discussed in this paper and the results indicate that mismatch losses are 5% of the predicted output.