The general objective of the ARCHIMEDES project is the development of a photovoltaic system with passive tracker for highly efficient and long term reliable water pumping with remarkable cost advantages compared to conventional fixed flat plate systems. The system is based upon irradiation enhancement in the module plane by flat plate mirrors in V-trough configuration and elimination of losses from off axis incidence using a maintenance free solar tracking unit, the gravitational/thermohydraulic tracking system (GTS). The new ARCHIMEDES system can demonstrate up to more than 40% cost advantage over systems using fixed standard flat plate PV modules.

This paper describes the work done after one year and a half within the framework of the PLISE project. This project aim at setting up a rating procedure for PV lighting systems, using mainly performance specifications in addition to component specifications. A rating method of the lighting system performance would provide a standardised information to potential customers and allow an objective comparative assessment of different designs. Initial studies showed that until now, no overall specifications nor procedures exist which address the performances of a complete system independently of the performances of the constitutive components. Three tests have to be performed to evaluate the performance of ten European solar home systems: components tests, definition and validation of indoor procedure using both a solar simulator or a programmable DC power supplied and definition and validation of outdoor procedure. Sincc the beginning, the procedure evolves and we present in this paper the procedure that will be proposed within the 1EC TC 82 NWIP 82/218. First results are presented and allow to validate the different procedures established. Future work will give more results and allow a comparison between all the results obtained in indoor/outdoor conditions with data collected in the field.

The considerable growth of the PV market that started 30 years ago, will lead to a fast growing number end of life modules. If good solutions for recycling are developed, a huge accumulation of this end of life and rejected PV modules can be avoided. The aim of this work was to develop and to evaluate different recycling processes. Finally two methods have given acceptable results namely the pyrolysis in a conveyer belt furnace and the pyrolysis in a fluidised bed reactor. Especially for the fluidised bed reactor process, the development has reached an industrial level with the set-up of a big pilot reactor. The cost effectiveness of the process is demonstrated by the high mechanical yield of the process and the high quality of the reclaimed wafers, as proven by a high cell efficiency after reprocessing. The ecological impact of recycling is very high and the energy pay back time decreases drastically due to the avoided high energy consumption of the reclaimed silicon wafer.

This article reports on a newly developed method for electrochemical deposition of buried Cu contacts in Si-based photovoltaic (PV) cells. Contact grooves, 20 mm wide by 40 mm deep, were laser-cut into Si PV cells, hereafter applied with a thin electroless NiP base and subsequently filled with Cu by electrochemical deposition at a rate of up to 10 mm per min. With the newly developed process, void-free, superconformal Cu-filling of the laser-cut grooves was observed by scanning electron microscopy and focused ion beam techniques. The Cu microstructure in grooves showed both bottom and sidewall texture, with a grain-size decreasing from the center to the edges of the buried Cu contacts and a pronounced lateral growth outside the laser-cut grooves. The measured specific contact resistances of the buried contacts was better than the production standard. Overall performance of the new PV cells was equal to the production standard with measured efficiencies up to 16.9%. (C) 2002 The Electrochemical Society.

The LGBG technology for high efficiency cells has grown in ten years from pilot line to 60 MWp per annum manufacturing capacity. Many improvements to the manufacturing process have been achieved in labour productivity through automation, increased laser grooving speeds and the introduction of in-line processes. Progress has been made in increasing the solar cell efficiency on monocrystalline silicon solar cells from a base line of 16.2% in present production to 17% in the new facility. Pilot line cells have demonstrated 18.3% efficiency and modelling has shown 20% cells are achievable in production. A small area cell with LGBG contacts has been made with an efficiency of 20%.

Presents an outline of the work done in the EC co-funded project ACE Designs. The objective of this project was to develop rear contact solar cell designs and to demonstrate their applicability as an alternative crystalline silicon technology for industrial module production. An overview of the results is given with links to the most relevant, publications for further details. The most important result of this project was that rear contact solar cells are a feasible, attractive and cost effective alternative to the well-known front contacted solar cell.

The current metallisation process for the manufacture of laser grooved, buried grid solar cells is based on electroless chemical plating. An electrolytic copper plating process is described that has the advantages of increased bath lifetime; shorter processing time; improved material usage; reduced over-plating; superior quality of the copper deposited and reduced effluent treatment costs. This paper describes work using a prototype electro-plating bath. This paper also describes an investigation of the use of cyanide-free solutions for coating the plated copper deposit on the solar cell. A number of electroless silver and tin coatings offer environment-friendly alternatives to the current silver cyanide process.

Back contact cells promise a cost reduction for the interconnection of cells to modules. The emitter wrap through concept allows in addition to combine low cost material, surface texture, a selective emitter (alkaline etch for Cz-Si respectively mechanical texturing for mc-Si) together with screen printed contacts as done in this work. The connecting holes are drilled by a laser. Emitter and base region at the cell rear are separated by a screen printable diffusion barrier. Computer simulations assisted the optimisation of the grid design especially in estimating the influence of the busbar regions to the series resistance. An efficiency of 15.8% was reached on Cz-silicon, which is the highest efficiency reported so far for a low-cost (i.e., no photolithographical steps) back contact cell. The authors obtained J/sub sc/ of 37.9 mA/cm/sup 2/ and V/sub oc/ of 600 mV. The internal quantum efficiency was found to be distinctly increased due to the selective emitter on the front.

A photovoltaic concentration array prototype of 60·4 m2 of aperture is described. It uses reflecting linear optics kept in focus by means of horizontal single-axis tracking. All its cells are connected in series so as to avoid laborious field interconnection work. This prototype is being followed by a demonstration plant of 3479 m2 of aperture. The prototype performances are presented and fitted to a model that allows their prediction under conditions different from those of measurement. On the basis of this model the demonstration plant performances are anticipated. A cost analysis is presented based on our best estimates after the erection of the present prototype. It shows that the cost of the electricity, in medium or large size installation, should be strongly reduced with respect to that produced by flat modules. © 1997 John Wiley & Sons, Ltd.

Plausible costs of photovoltaic power plants of concentration are presented. Costs are based as much as possible on the recent experience of solar thermal plants. Efficiencies, on the existing world experience of PV power plants. The result is that the costs of concentrating photovoltaic plants should be of 0.08 ECUs/ kWh, about 1/3 of that of flat module plants, and of the same order of magnitude, even lower, than those attributed to solar thermal plants of present technology. For the future, high concentration systems based on Si or tandem cells seem to be the most promising, also in the range of costs of the advanced solar thermal plants.

BP Solar has recently expanded its manufacturing base for the buried contact solar cell. This paper describes automation and manufacturing methods introduced during this expansion. This paper also describes two technologies, which can bring environmental benefit for large scale processing. The first, an electrolytic copper plating process for cell metallisation, has advantages over electroless plating with increased bath lifetime, shorter processing time and improved material usage. The second, an investigation into environment-friendly coatings over the plated copper deposit on the solar cell. A number of silver and tin coatings offer alternatives to the current silver cyanide process.

LGBC silicon solar cells have demonstrated efficiencies up to 20% when used in linear focus concentrating systems up to 20/spl times/ concentration. Small area cells of 1.2 cm/sup 2/ have been cut from these cells and tested up to 100/spl times/ concentration for point focus applications. A potential to achieve 20% efficiency at 100/spl times/ has been recognised and independent results to date have shown an efficiency approaching 18% at 100/spl times/. Based on simple variations of a mass production process, analysis indicates that the manufacturing cost for such cells can be below $0.15/Wp.

An effective way to achieve cost reduction in PV is to increase solar cell efficiency, which increases the module power density and reduces the balance of systems costs through lower area requirements, lower structure costs, reduced module interconnection and less installation time. This paper reports on efforts taken to develop cost-effective monocrystalline silicon substrate materials that do not suffer light induced degradation, and to use these wafers to apply laboratory concepts to industrial production to fabricate high efficiency monocrystalline solar cells. Both Ga-doped Cz ingots and PV-FZ ones have been successfully produced in a wide range of resistivities, and their high quality and lack of light induced degradation confirmed. For a laboratory process, 20.6% efficiency has been achieved on the FZ material, and 19.7% on the Ga-doped Cz. The potential of these materials to produce industrial high efficiency solar cells is shown by pilot line production of Laser Grooved Buried Contact cells of 19.2% on FZ samples and of 18.4% on Ga-doped Cz ones.

Back contact cells promise a cost reduction for the interconnection of cells to modules. The Emitter Wrap Through concept allows in addition to combine low cost material, surface texture, a selective emitter (alkaline etch for Cz-Si respectively mechanical texturing for mc- Si) together with screen printed contacts as done in this work. The connecting holes are drilled by a laser. Emitter and base region at the cell rear are separated by a screen printable diffusion barrier. Computer simulations assisted the optimisation of the grid design especially in estimating the influence of the busbar regions to the series resistance. An efficiency of 15.8 % was reached on Cz-silicon, which is the highest efficiency reported so far for a low-cost (i. e. no photolitographical steps) back contact cell. We obtained Jsc of 37.9 mA/cm 2 and Voc of 600 mV. The internal quantum efficiency was found to be distinctly increased due to the selective emitter on the front.

It is well known that thin film (~10's of µm) silicon cells have the potential to produce similar efficiency to their conventional counterparts with suitable light-trapping schemes. The use of thin films reduces the amount of high grade semiconductor material required and provides the potential for lower cost at similar or higher efficiency. This paper describes collaborative work between BP Solar UK, and Imperial College London to develop a high quality thin film silicon cell as a benchmark for the best possible performance of thin film silicon. The growth conditions for high quality silicon on heavily doped substrates have been optimised. Test structures consisted of ~10µm of boron doped silicon grown on heavily p-++ substrates, with the n+ emitter structures diffused during processing. Growth by ultra- low-pressure chemical vapour deposition (ULP-CVD) and gas source molecular beam epitaxy (GS-MBE) have been compared. Both modes are available within a single machine. Wafers grown by both methods were processed into cells and their performance compared. It was found that GS-MBE provided the best performance devices. Further optimisation of the growth conditions of the GS-MBE showed that the best cells were grown at 700°C. This was the maximum growth temperature considered so as to remain compatible with the transfer of the technology to growth on glass. Growth of in-situ n+ emitters with arsenic doping has been investigated. These cells were also processed into working devices, the results however were disappointing with performance significantly worse than for diffused emitters. A peak efficiency of 15% was achieved with a 15µm layer with top