RD potential

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The largest single factor precluding more rapid penetration of renewable energy technologies into these markets is the cost of renewables. Table 5.1 shows that the cost of most renewable energy technologies has been declining and is expected to continue to do so. The cost decreases have occurred from industrial learning through the production process as well as through research and development (R&D). While all renewable technologies are expected to have future cost decreases, the potential for cost reductions is not the same for all of them. For example, hydroelectricity is a relatively mature technology where the majority of the research is directed at mitigating environmental impacts, not reducing costs. On the other hand, photovoltaics' current high processing costs of relatively inexpensive materials provide ample opportunity for future cost reductions. Below, we examine the R&D-related cost reduction potential for three renewable energy technologies with significant R&D opportunities.

Table 5.2 Renewable electric technologies

Technology

Variations

Photovoltaics

Wind Biopower

Hydroelectricity Landfill gas

Geothermal

Ocean energy

Solar concentrating power

Configuration - flat plate, concentrating Material type - crystalline silicon, thin films Cell type - single junction, multifunction Location - land, water Orientation - horizontal axis, vertical axis

Resource - agricultural and mill wastes, forest wastes, municipal wastes, dedicated energy crops

Output - cogeneration, power only

Configuration - cofiring of coal plants, direct combustion, gasification

Cycle - steam, combustion turbine, combined cycle gasifier

Resource - reservoir, run-of-river

Output - cogeneration, power only Configuration - combustion turbine

Application - heat pumps for space conditioning, industrial process heat, power only

Resource - hot water, steam, hot dry rock

Power conversion - flashed steam, binary

Resource - tidal, wave power, ocean thermal energy conversion

Concentrator - troughs, dishes, central receiver

Configuration - hybrid, solar-only

Storage

5.2.2.1 Photovoltaics

The two distinguishing features of R&D on photovoltaic systems are the multiple paths available for improvements and the fact that processing costs make up the bulk of today's module costs. By pursuing multiple R&D paths, the probability of finding one or more routes to cost competitive photovoltaic modules is increased. While silicon crystal constitutes more than 85% of production today (Cassedy, 2000), a multitude of thin films are being investigated. These include polycrystalline sheets, amorphous silicon, and a host of semiconducting compounds, such as cadmium telluride, gallium arsenide, and copper indium selenide, all of which absorb wavelengths that predominate in the solar spectrum, increasing their potential efficiency compared to silicon materials. Because these materials can be deposited from the gaseous state, they offer the possibility of multijunction cells with efficiencies potentially greater than 30% resulting from absorption of a wide spectrum of wavelengths. Such high-efficiency cells also lend themselves to the use of reflectors and/or lenses, along with mechanisms, to track the sun to increase the sunlight incident on the photovoltaic cell. Many innovative tracking mechanisms and concentrator assemblies are being investigated for such concentrating systems. Cost reductions are also possible in the manufacturing process itself, through both direct research on manufacturing processes and through learning during the production process. Learning is also reducing the balance-of-system costs for components other than the photovoltaic modules, like the inverter, controls, grid interconnections, tracking mechanisms, and frames.

At issue is whether or not this research and learning will bring the ultimate cost of photovoltaic-supplied electricity from its current levelized cost of $0.25-$0.50/kWh to the $0.03-$0.06/kWh required to be competitive today in grid-connected distributed electric markets. Although this may be extremely difficult, research continues because potential improvements are promising and the market value of a clean modular energy source like photovoltaics is expected to increase.

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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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