A Basic Comparison of Two Solar Energy Conversion Methods

@ruperto (1552)
Philippines
June 10, 2010 10:00am CST
There are two commonly used solar energy technologies available. One is solar photovoltaic while the other is solar thermal. Solar photovoltaic make use of transducers that convert sunlight directly into electricity in the form of direct current. Solar thermal makes use of sunlight collector to convert the heat of the sun into mechanical energy that drives a turbine. Solar panels used in photovoltaic are actually more expensive for generating large amounts of power. However, solar panels are a “cheaper” choice for low power outputs up to a few hundred watts. The green machine driven by a solar collector is used in solar thermal plants and is a very good choice for power outputs of about 5,000 watts or more. For ease of reference from this point onward, let us refer to the photovoltaic system simply as “solar panel” and the solar thermal system as “solar collector”. It is worth noting that both types of systems above do not emit greenhouse gases and do not rely on any non-renewable energy sources. Solar photovoltaic and solar thermal are totally clean and renewable. A point of comparison between the solar panel and the solar collector is that the solar panel has no moving parts as it generates electricity using a special semiconductor that has the characteristic of producing an electric potential when light is shone on it. The solar collector machine, on the other hand, besides involving the laws of thermodynamics, also has moving parts. For instance, the solar collector fluid is circulated by a heat pump while the final output is a mechanical rotation with enough torque to drive a water pump and/or a power generator. Unlike the solar panel, the solar collector is more flexible because the heat source may not be sunlight. It could be waste heat which is usually “thrown away” e.g. in man-made processes such as thermal plants, boilers etc. Finally, for practical applications, solar panels are normally used to energize up to the size of a small household, while solar thermals are normally used to energize up to hundreds to thousands of households.
1 person likes this
3 responses
• Philippines
11 Jun 10
hello ruperto, if only the thermal solar can be used for good in this country. i am sick with the use of coal, and i mean plants are still using coal and hydro where we can use thermo with the four volcano's that are in the country. i hope there is a legislative resolution to this, because we also have summer, therefore we can actually get electricity from the SUN for at least two months.
1 person likes this
@ruperto (1552)
• Philippines
11 Jun 10
hello LetranKnight25 Thanks for the comments. I think hydroelectric and geothermal, as already used in the Philippines, will even be more valuable for the many years to come. BTW the company in the US called Electratherm.com has responded to an inquiry for delearship of green machines that can generate multiples of 50KW. The energy source would be a locally made solar collector such as a solar pond of brine (about 8 feet deep). I think every square meter of the pond can contribute up to 500W. So a 50KW system would use a 1,000 square meter pond. It is amazing how Ormat in Israel has been using this technology for more than 50 years. Would you have contacts who may be interested to be dealers of these solar thermal to mechanical energy systems? I'm all ears ;)
• United States
10 Jun 10
Thanks for posting that. I really hope to see what kind of stuff they put on cars and whether or not this is a plausible solution for future energy needs. I've heard that our solar dependency right now is minimal only because the actual amount of electricity we need we can't collect in the amount of time the sun is up. I hope that they can make better more concentrated solar panels in the future. Do you whether or not solar panels are recyclable? I've never wondered that till just now. And whether or not they would last a long time or do they eventually break after being in the sun for so long? thnks!
@ruperto (1552)
• Philippines
10 Jun 10
Thanks for the comment. I think most solar panels are recyclable and meant to last for about 25 years. The material solar panels are made of are manufactured at temperatures way above the "field temperature" these will be exposed to. For solar collectors, there is the alternative of energy storage e.g. using a large amount of salt solution. The heat may be store in solar pond after sunset and before sunrise. meanwhile, a circulating pump is transferring this heat into a green machine that extracts the energy given of when the fluid is "forced" to "temperature drop" anywhere from a delta of 10 to 40 degrees. It's amazing that this energy is sufficient to cause another fluid (with low boiling point) to vaporize and drive a turbine. If you consider this technology as a business or career, let us discuss more... or please check out electratherm.com Cheers and more Power :)
@veganbliss (3903)
• Adelaide, Australia
6 Apr 11
Good topic! You've given a fairly broad view in comparing both systems. I would tend to favour the Solar Thermal System. It provides a much greater return on investment as well as more efficiency. Solar hot water systems might be a good household example. Although more accurate detail could be put into describing the workings of the two, it would be more interesting to take a look at the advantages as well as disadvantages of the systems. My discussion topics have been quite critical of subscribing to those solar installation schemes for householders as the return on investment is particularly poor. Here, it is estimated to take about twenty five years just to break even on the set-up costs, making it ridiculously nonviable. The money wasted on subsidies would be better spent elsewhere. There are other much, much better & infinitely less expensive alternatives. It is also important to note that the manufacture of solar cells must be done very carefully in controlled laboratories & the materials used are not necessarily totally clean & renewable & the manufacturing & installation processes, amongst others necessary to bring a completed, working system to the consumer, do generate considerable amounts of greenhouse gases. The solar hot water systems, whilst largely mechanical, need not have any moving mechanical parts (water cannot be considered as a moving part, for example).