Solar Technologies – Thermal (Concentrated Solar Power) & PV

When I tell my friends and family I am working on solar Technology, the first question(s) they ask me  usually goes like this…

  • Are you supplying the generated power to the grid?
  • How much can solar help me save on my electricity bill? 
  • How many watts/Kilo watts are you generating?

It is very difficult to make them understand that I am on to Solar Thermal technology which also leverages Solar as energy source. So I have been wanting to write a Blog (my first one) on Solar thermal Energy to help few people out there who have been attuned to the fact solar=PV. I have tried to compare both these technologies at a very basic level and provide my view points.

Solar thermal Vs PV (electricity)

Let us start from the basics. PV panel converts solar radiation into electricity. Solar thermal system concentrates the solar radiation and transfers the energy, mostly to water. Photons from Sun Rays displaces electrons in the Crystalline semiconductors to produce electricity whereas Solar radiation is used to heat underlying medium ,mostly water or oil and this underlying heat energy is transformed into other forms of energy to cater to our needs(Remember Law of conversation of energy from high school days )!!!

Solar Radiation is concentrated by mirrors or lenses to obtain higher temperatures – a technique called  concentrated Solar Power (CSP) is used for this and this is as ancient as Sun Dials and some might argue it is even older than that. Nevertheless the first patent on Solar collector was registered in 1866 (AD of course).

Enough of the Basics. Let me get to the interesting part, I want to provide my view point on a match up between  Thermal vs PV Solar Energy.

For sake of this discussion leave out CSP, the huge scale solar concentrators for power generation(Yes Solar Thermal can also be used for electricity generation, that is for another time). We will focus on other varying needs – the specific need determines which technology(PV vs Thermal) to choose.

Now a days it is becoming a trend in India to have a small captive power generation with PV panels in households for lighting and to power the fans because of unreliable grid supply.

Since the last decade solar thermal came into part of households to generate hot water even though they had compact good looking electric heaters. Solar thermal had a great success in replacing electric heaters. More than 7 million sq meter installations are harnessing solar thermal power for heating water in India.
Cost and efficiency, the efficiency of solar roof top water heaters are above 65% with affordable storage. Meanwhile the PV has average of 16% at 25ºC atmospheric and the overall efficiency is just 10% for Indian conditions.

Storage of electric energy is costly. Grid supply might be slightly lesser than PV’s generation cost still you are polluting somewhere, consuming and depleting energy resource.

Solar thermal in process heat.

We are at a situation where we need to start thinking about harnessing the solar power not only at a large scale, generating electricity in Mega Watts scale  but also for small scale utilities in our Industries.

The former (Electricity generation to Grid) requires lot of stars to line up and there is very little or nothing that small scale industrialists or common man do about it. But on the other hand the using solar energy in the form of Thermal energy is something that is realizable for everyone enabling them to make a difference for future generations.

The most common need in industry, be it textile, paper, food processing etc., is heat. The industry needs huge amount of heat at medium temperature range from 80ºC to 120ºC. Using Solar thermal energy greatly helps these industries reduce their operating costs.

The main sources of the heat in process industry in India are fire wood, fossil fuel & electricity. Fire wood stays first in process heat application. Most of the companies use steam boilers to cater different type process heat needs and they operate the boiler at elevated temperature at 175ºC. The overall system efficiency becomes very less. Small units cannot install boilers and they use electric heaters or fossil fuels.

 It is being proven again and again that is very much possible to direct the solar radiation to cater process heat needs at more than 50% of system efficiency with well proven Thermal technology.



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So What do you think????