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Efficiency and fabricability improvements in silicon concentrating cells

Objective



Concentration photovoltaic is a clear way of reducing quite sensibly the cost of the PV electricity (EUCLIDES prospects -a concentrator prototype developed in JOULE II- are 3.08 ECU/Wp installed, with present technology). Opposite as in flat module systems, in concentration the cells are only a small a component of the system cost.
In consequence the cost-efficiency trade-off is well different, and different for different levels of concentration, tending in all cases to favour higher efficiencies.
This proposal jointly with additional R&D to be done in the concentrator sector, aims to achieving 2 ECUs/Wp (to be reached within the decade). The Commission goal of 1 ECU/Wp module cost represented installed costs higher but approaching the 2 ECUs/Wp.
In consequence our proposal is in agreement with the cost Commission strategy The specific goals of this proposal are: (a) Optimizing the linear concentration cells. This means improving efficiency to 21%, with low or no cost increase in 30 suns linear concentration industrial cells (BP Solar) of 40 cm2. Alternatively, 20% in 48 cm2 cells. Higher concentrations will also be explored. The overall cheapest option, and any other one requested by market considerations (that might appear as an input to the project), will be adopted. (b) Industrializing point focus concentration cells in the range 80-100 suns with efficiencies above 22% (area around to 1 cm2, to be determined more precisely in the project), also using light confining cavities. For cost considerations these results must be obtained with non clean room technology.
In order to achieve higher efficiency four issues will be investigated. (a) The careful study (experimental although with theoretical grounds) of the aspects associated to the series resistance. This involves the emitter profiling and the determination of the actual resistances in the different layers and interfaces. (b) The utilization of gettering techniques so that self-purification of the wafers during the processing steps is produced and therefore the need of clean room process (for high efficiency) is avoided. (c) The use of silicon wafers grown by the float zone (FZ) technique. So far industrial wafers are grown by the Czochralsky (Cz) technique. The FZ technique can give more pure wafers, suitable for higher efficiency. Such wafers do not exist in the market with characteristics (size) appropriate for the PV industry. A suitable grower for PV industry use (fast growth, ingot size up to 150 mm diameter) will be developed. (d) The increase of the light absorption and light confinement. In the point focus case light confining cavities developed in the PV-EYE JOULE I project will be pre-industrialized here. In the linear case light additional work on light deflectors will continue outside this project. Both devices will affect the grid design in (a) PV is in general environmentally friendly. However the fabrication of solar cells, uses energy rather extensively. Due to the strong reduction of solar cells, with the concentration approach contemplated in this project (in the climate of Madrid), the payback time is reduced to about one year for the whole PV plant, to compare to the about two years for flat module.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

UNIVERSIDAD POLITECNICA DE MADRID
Address
Ciudad Universitaria - Etsi Telecomunicacion
28040 Madrid
Spain

Participants (4)

Angewandte Solarenergie - ASE GmbH
Germany
Address
2,Theresienstrasse 2
74072 Heilbronn
BP SOLAR LTD
United Kingdom
Address
Chertsey Road
TW167XA Sunbury-on-thames
Forschungsverbund Berlin e.V. - Gemeinsame Verwaltung
Germany
Address
6,Rüdower Chaussee 6
12489 Berlin
Université d'Aix-Marseille III (Université de Droit d'Économie et des Sciences)
France
Address
Avenue De L'escadrille Normandie-niémen
13397 Marseille