2000

93.7 (1,009)

38,953

Table 14-3 Test Results for Available Radiation vs. Actual Production. Source: CADDET Renewable IEA/OECD Technical Brochure No. 142

Table 14-3 Test Results for Available Radiation vs. Actual Production. Source: CADDET Renewable IEA/OECD Technical Brochure No. 142

conditions and with an inverter efficiency of 100%, so that the solar cell conversion efficiency is the only factor affecting output. Note that in some cases, the inverter efficiency may already be included in the manufacturer's performance test data and would not be factored into the PR computation. In this case, dividing the annual kWh production by the product of the annual insolation on the roof per unit area and the area of the modules yields an average field-application efficiency of about 10%. Dividing this by a PR of 76% would indicate that the design rated performance for the modules (before consideration of inverter and other application-related losses) is about 13%.

The 24% overall system losses were due to inverter losses and local conditions. The principal element was inverter losses of 14%. An additional 3% loss was attributed to shadowing from adjacent rows of modules and from trees and buildings. The remaining 7% was attributed to accumulation of dirt and snow, light reflection from module surface at small incident solar angles, derating of conversion efficiencies at actual solar-cell temperatures in excess of 77°F (25°C), lower conversion efficiency at lower solar irradiance levels, mismatch in output between modules in subsystems, and Ohmic losses in cables.

As opposed to solar thermal technology applications, only direct sunlight (or daylight), not diffuse or reflected light, will cause the PV effect. Hence, ideal locations are those with little cloud cover. PVs can operate in daylight without sunshine, though at a reduced rate.

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