Potentials for tracking photovoltaic systems and V-troughs in moderate climates

The irradiance received and the energy costs for tracking photovoltaic systems and V-trough concentrators are derived relative to the costs of a fixed system. Radiation data from 28 sites, especially in moderate climates, are investigated with regard to the surplus of radiation achieved with one- and two-axes tracking surfaces. By use of the Perez model the fraction of the supplementary irradiance is computed. A comprehensive computer code describing the optical performance of a low concentrating V-trough was developed. It is used to calculate the annual average concentration for diffuse and direct irradiance under different climatic conditions. Applying a life-cycle cost analysis relative to the costs for a fixed array, the results are freed of political-economic assumptions (inflation or discount rate). The resulting relative energy costs are dependent mainly on module costs. A sensitivity analysis shows that the results are stable against variations in meteorological data, balance-of-system or module efficiencies, and power related balance-of-system costs. The most economical system turns out to be the one-axis tracking PV system for moderate climates. It promises cost advantages for module costs even down to 250 $/m2 if the tracker costs do not exceed the area-related balance-of-system costs of fixed systems by more than 100%.