Technology Assumptions and Issues

Residential PV systems are not yet cost competitive with grid-connected electricity; and most of the systems installe d to date were subsidized. Many were installed in Japan and in Europe, where there is significant public support of clean energy sources. The bulk of PV modules sold today, and of residential PV systems installed to date, use one-su n modules with crystalline-silicon solar cells. Also, most PV systems are used today in applications where there is n o low-cost source of grid electricity.

The technology progress described in this report assumes an orderly expansion and development of the market fo r residential PV systems, and continued improvement in both cost and performance of the PV modules and balance-of -system components. As the market for these systems increases, installation costs and standardization, along wit h improved manufacturing processes and increased conversion efficiency, are expected to reduce various cos t components significantly. Achievement of the market expansion and technology improvements, however, are no t certain and will require significant further public and private investment. Identification of early cost-effective markets and marketing of "green" power will be critical for market expansion in the early years when PV system costs are still much higher than grid-tied electricity. This stage can be assisted through publicly and privately financed programs , including the Million Roofs Solar Initiative, to help identify and develop the interim high-value markets described i n Section 2.

Further technology improvements to reduce the cost and improve the performance of PV modules and balance-of -system (BOS) components are required. Substantial reductions in costs and improvements in efficiency have bee n achieved over the past 20 years. This progress has been greatly assisted by publicly funded R&D. Continuation o f this R&D will be instrumental for further progress since the profit margins in the PV industry have been insufficien t to support an adequate private R&D program. The recent progress in crystalline-silicon PV technology has been greatly assisted by publicly funded R&D programs like the DOE PV Manufacturing Technology (PVMaT) program an d publicly -funded, DOE laboratory and university R&D. Some of the technology improvements and product desig n changes that have helped reduce cost include the following: casting of larger ingots to improve the productivity o f crystal-growth; replacement of inner-diameter saws with wire saws to improve the productivity of slicing ingots ; improvement of the yield and throughput of cell fabrication processes, e.g., diffusion and antireflection coating; us e of larger area cells to reduce the cost of operations that scale per piece, e.g., screen print and cell tab; and use of larger area modules to reduce the costs of components that scale per module, e.g., interconnection box and module testing. Compared to the present crystalline-silicon PV modules, thin-film PV technology promises further cost reduction s because of its inherently lower material and energy content, and to a product design that could be more manufacturable, planar processing of large-area substrates. DOE and private (e.g., EPRI) R&D programs were instrumental in the development of this completely new technology, and the first large-scale, >5 MW/year, thin-film PV plants starte d operations in 1997. Finally, BOS components are a significant cost factor in PV systems. PV modules with integrated inverters or with building-integrated features may have a significant impact on grid-tied PV system costs.

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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