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Development of optical concentrators for small PV systems

Objective



Objectives

Photovoltaic systems have advantages as sources of small amounts of electrical power in remote areas, but conventional solar panels are expensive. This project aims to reduce the cost of solar electricity by developing small optical systems to concentrate the sunlight onto solar cells to increase their electrical output. A typical unit of 2m2 aperture will give 200-300 watts, enough for household electrification (lights, radio and television) for a farm, school or a few houses, or for small scale water pumping. It should be possible to make concentrator systems at half the cost of current planar solar panels.

Technical Approach

Many concentrators have been developed in the past, but they have usually been as expensive as conventional solar panels, because concentrator solar cells have cost much more than one-sun cells, and the optical and tracking systems have been expensive. Recent developments, such as BP Solar's laser-grooved buried-grid cells, have made it possible to manufacture solar cells, little different in design and cost from one-sun cells, that can be used at concentration ratios up to 40x. Using these cells with minimum-specification optical and tracking systems, there is considerable scope for cost reduction.

The collaborators, Reading University, Universidad Politechnica de Madrid, and ZSW, Stuttgart will examine a wide range of possible concentrators, from fixed non-imaging systems with concentration ratios of 2 or 3x, which are expensive in cells but cheap in structure, through cylindrical lens and mirror systems with concentration ratios of 10 to 20x and single axis tracking, to spherical lens systems with concentration ratios around 40x that require two axis trackers. For each system, performance will be estimated using computer ray-tracing programs, taking due account of material properties, manufacturing imperfections, and the daily and annual motion of the sun. The manufacturing cost of each system will be estimated on a common basis, and the cost per watt calculated. Four systems will be chosen to be manufactured as 2 m2 prototypes. They will be built in Reading, and tested for a full 6 months at ZSW's test site at Widderstall.

Expected Achievements and Exploitation

It is expected that the best concentrators will cost about 2 ECU per Watt-peak, compared with 5 ECU/Wp for planar arrays. Such a cost reduction will make pv systems much more attractive to users. The principal users of these small systems will be villagers and small farmers in remote areas, mostly in developing countries, so there will be considerable opportunities for export. It is probable that solar cell strings, optical elements and tracker components will be made in Europe and exported, and the relatively bulky mechanical structures will be made in the country of use; this will encourage the development of an indigenous solar PV infrastructure which is essential to provide users with technical support and maintenance.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

UNIVERSITY OF READING
Address
Whiteknights
RG6 6AY Reading
United Kingdom

Participants (2)

UNIVERSIDAD POLITECNICA DE MADRID
Spain
Address
Ciudad Universitaria - Etsi Telecomunicacion
28040 Madrid
Zentrum für Sonnenenergie- und Wasserstoff-Forschung,Baden-Württemberg
Germany
Address
21 C0,hessbrühlstrasse
70565 Stuttgart