The development and testing of small concentrating PV systems.

Abstract -Spreadsheets have been used to compare some 90 possible small PV concentrator designs that might be suitable for use at remote sites. They have apertures of about 2m 2 , use BP Solar LBG cells, and employ small aperture modules to reduce heat sinking and construction costs. Designs include fixed V-troughs and CPC's, single axis tracked cylindrical lens and mirror systems, and 2-axis tracked spherical-symmetry systems. Performance and volume production costs were estimated. Four promising systems were constructed as prototypes: A -Point-focus Fresnel lenses, 2-axis tracking; Cg = 32x; and 69x with secondaries. B -Line-focus mirror parabolic troughs, 1-axis tracking, Cg = 20x. C -SMTS ('Single-mirror two-stage'), 1-axis tracking, Cg = 30x. F -Multiple line-focus mirror parabolic troughs, E-W 1/day manual tracking, Cg = 6x. The prototypes were tested at Reading, and three for up to a year's field trial at ZSW's test site, Widderstall, in Germany. The best system efficiencies, normalised to 25°C and excluding the end losses of linear systems, were 12.5%, 13.2%, 13.6% and 14.3% for collectors A, B, C, and F, respectively. The collectors were practical and robust, and the performances of collectors B, C and F are only 10% below the estimates in the spreadsheet calculations. The best collectors have estimated production costs between 1.5 and 1.8 US $/Wp, yielding energy costs at a good site (excluding BOS and overheads) of between 5 and 7 cents/kWh (18 and 25 cents/MJ). On the same cost basis a conventional PV array costs 4.3$/Wp, and 18 cents/kWh (65 cents/MJ)