An Australian company, Solar Systems (ref: http://www.solarsystems.com.au), produces dishes that concentrate solar energy onto an array of silicon-based photovoltaic cells. It works much the same way as conventional solar panels with the difference that sunlight is focused onto a small area, similar to a magnifying glass. This concentration can be as high as 500x. Concentrating the sunlight increases the efficiency of the photovoltaic cells.
The economic advantage of this type of system over conventional flat plate solar panels is that much less photovoltaic material is needed. As is well known, one of the prohibiting factors in manufacturing photovoltaics is the high cost and relatively low production rate compared to other renewables, such as wind turbines.
By reducing the amount of photovoltaic material required one can realize a substantial reduction in material cost.
However, a major design issue is that the focused light produces a large amount of heat which must be dissipated to avoid “frying” the solar cells. So an intricate cooling system must be used. Its makers claim that, cooling system included, the cost is still much less than conventional photovoltaic installations.
Details on their website are a bit scarce, but they say that the efficiency of one of their latest dish systems is 24%, and each dish system produces 24 kW. That’s pretty good. It’s close to the efficiency of Solar Stirling dishes, which is about 30% (ref: http://www.stirlingenergy.com). You notice a large similarity between the two systems. They both use parabolic dishes and tracking mechanisms to focus the sun’s energy. The Stirling dishes have the advantage of using the heat generated at the focal point, which represents a larger percentage of the sun’s energy than can be captured by photovoltaics. This results in somewhat greater efficiency than in the concentrator photovoltaic (PV) unit.
Solar Systems has plans in the works for a large 154 MW plant in north-west Victoria, Australia. The plant will be built using Heliostat Concentrator Photovoltaic Technology (HCPV). Using a field of heliostats, the sun’s energy is concentrated onto receivers, using the same level of concentration as for the dishes (500x). For details see http://www.solarsystems.com.au/HCPV_Technology.html.
In my opinion, concentrator PV systems would need the ability to scale up at least as fast (production volume) as Stirling dishes and with similar cost, to make it viable, not the least of which is increasing the efficiency to match. But who knows, it might get pretty competitive between the two.
Like other solar thermal technology, concentrator PV is limited for use in areas that have little cloud cover. The sun has to be shining for them to work, since only then can the light be focused. When the sky is cloudy, only a conventional solar panel will produce electricity using the sun’s energy.
Like other types of solar thermal power, concentrator PVs will work well in places such as the southwestern United States, South America, Australia, Africa, Spain, and Middle East.
The waste heat that is generated at the focal point of concentrator PVs (and ultimately dissipated) is a source of efficiency loss. The heat dissipation is necessary because it prevents the sensitive components from melting, but in my opinion it represents a preventable loss in efficiency. It makes me wonder if it’s possible to take this waste heat and use it for powering a heat engine such as a Stirling engine. Now, I don’t know how much waste heat is generated, but I figure if it’s more than 300 degrees Celsius you can get enough extra energy out of it to make the system worthwhile, or at least comparable to Stirling dishes.
Maybe it’s possible to utilize more of the sun’s energy than is possible with just a concentrator PV or a Stirling dish. Maybe some hybrid-type of combination is possible using photovoltaic cells and a heat engine, which allows a greater percentage of energy to be captured from the sun’s spectrum, than either can achieve by themselves.
Nevertheless, concentrator PV technology is well established. Some other producers of the technology claim similar efficiencies of 25% or greater, such as SolFocus. See the links below.