The Degree of Load-Matching in Photovoltaic Systems

Abstract

The degree of load-matching in a photovoltaic (PV) system corresponds to the efficient utilization of the solar cells in the PV system. A high degree of load-matching is obtained when the load-line follows closely the maximum power-line of the solar cell (SC) generator. Some loads inherently exhibit a relatively good matching, and for others the matching is poor. This study introduces a quantitative measure for the degree of load-matching by defining a utilization efficiency-factor for the solar cells of the PV system. This factor is defined as the ratio of the load input power P to the maximum power P_max the SC generator for the corresponding insolation levels; also a daily average utilization efficiency-factor is defined. As examples for the calculation of the degree of load-matching, two loads that are directly coupled to the SC generator are examined: (a) an ohmic load, and (b) a storage battery. The daily average utilization efficiency obtained for the ohmic load is 73%, and for the storage battery is 83%. These two examples show that the load of the storage battery is more compatible with the solar cells than the ohmic load is.