The use of appropriate performance parameters facilitates the comparison of grid-connected photovoltaic (PV) systems that may differ with respect to design, technology, or geographic location. Four performance parameters that define the overall system performance with respect to the energy production, solar resource, and overall effect of system losses are the following: final PV system yield, reference yield, performance ratio, and PVUSA rating. These performance parameters are discussed for their suitability in providing desired information for PV system design and performance evaluation and are demonstrated for a variety of technologies, designs, and geographic locations. Also discussed are methodologies for determining system a.c. power ratings in the design phase using multipliers developed from measured performance parameters.

Assessing snow-related energy losses is necessary for accurate predictions of photovoltaic (PV) performance. A PV test platform with seven portrait-oriented modules placed at four tilt angles (0, 15, 30, and 45 degrees) was installed in Calumet, Michigan to measure the energy loss in this snowy climate. As a best-case snow-shedding configuration, three modules were elevated high enough to prevent surface interference. The opposite effect of maximum surface interference was introduced by mounting the other four modules at ground level. The platform was monitored for one year beginning in October 2013. The snowfall that winter was 5.3 m (209 inches). Snow-related annual energy losses ranged from 5% to 12% for the elevated, unobstructed modules, with the steepest tilt angle experiencing the least amount of energy loss. For the obstructed modules, there was proportionately less angular dependence on lost energy and annual energy losses ranged from 29% to 34%. This relative 3-to 6-fold increase in lost energy when ground interference is present points out the importance of prompt snow clearing for portraitoriented PV. Depending on the breadth of an inverter's operating voltage limits, these results suggest that landscape-oriented array layouts and perhaps snow-clearing mechanisms may be advantageous in snowy climates.

No abstract

No abstract

No abstract