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While solar energy is often spoken of as if it is just one technology, in reality, solar energy comprises two distinct technologies – solar PV and solar thermal.

Solar PV uses the sunlight to excite electrons to produce electricity, while solar thermal uses the heat in the sunlight to produce either heat or electricity.

Both solar PV and solar thermal have been used worldwide, though the magnitudes and the applications vary.

Solar PV is primarily used to produce electricity – both off grid and grid connected. Solar thermal on the other hand is used primarily for heating and drying applications.

Worldwide, solar PV currently has an installed electricity capacity of about 14000 MW while solar thermal has only about 500 MW of electricity installed capacity. But this data might not represent the true contribution of solar thermal to energy consumption. The reason is as follows: Solar thermal is used in a significant way worldwide for producing heat and drying. If this contribution were to be considered, it is estimated that the equivalent installed capacity of solar thermal would be about 80 GW. Compare this with 14 GW for PV, and one understands why solar thermal’s contribution is actually more than that of solar PV. This comparison also shows why the world needs to give solar thermal as much importance and focus as it does for solar PV.

Though the heating and drying applications of solar thermal is likely to dominate over its use for electricity production, solar thermal based power has its advantages as well. Solar thermal costs significantly less in terms of levelized costs of electricity generation, when compared to PV – 25 cents per kWh (PV) vs 15 cents for CSP. (2009 data)

In India, there is no power generation currently (2009) using solar thermal. Solar thermal has been used exclusively for heating and drying.

So far, solar PV use has been minimal as well in India, with just about 100 MW of solar PV having been installed as of mid 2009. Of the 100 MW installed capacity for solar PV, only 2 MW installed capacity is available in grid connected form. The rest are available in a distributed way – on rooftops and at industries and factories for captive electricity generation. But the insignificant contribution to electricity from solar PV could change as a result of the new thrust by the central government to incentivise energy production from solar sources. The National Solar Mission launched recently, has a specific emphasis on solar PV for augmenting power production via solar sources from 2 MW now to 20,000 MW by 2022.

Solar thermal’s contribution to energy consumption in the form of heating and drying India has been growing steadily. The country installs over 25,000 solar heaters every year and this number is likely to accelerate even further.

The objective of this article is to analyse the potential that India has for solar thermal based electricity generation.

Solar thermal based electricity generation is more commonly called CSP, for Concentrated Solar Power, owing to the technology used for generating power which concentrates the sunlight to produce maximum heat. As mentioned earlier, globally, there is only about 500 MW of CSP installed capacity. Most of this installed capacity is in the United States.

According to some estimates, India can have a CSP installed base of 4-5 GW by 2020 (Source: TERI). The potential states in India for CSP are Rajasthan, Gujarat, Maharashtra, Karnataka, MP, Haryana , Tamilnadu, AP potential states. I suspect that the total potential for solar thermal to electricity generation could be far higher than just 4-5 GW.

However, I see little activity taking place in this space. All roadshows, conferences and exhibitions I visit predominantly focus on solar PV with thermal being represented only by solar water heaters. Even the investments I hear of in the solar industry have been largely confined to the solar PV segment.

According to some estimates, if we utilize a portion of the Thar desert for solar CSP, we can generate electricity for the entire country. This being the case, I would have thought solar CSP will get an equal amount of attention. But it is not.

What could be the reasons?

1. Worldwide, solar CSP is not as popular as solar PV. This means Indian companies do not have too many technology suppliers even if they wish to invest.
2. Solar PV costs are falling rapidly, and some even suggest that grid parity will be reached within the next 5-7 years. This makes investments into solar PV a more attractive proposition. Costs for solar CSP are not falling equally rapidly.
3. When businesses consider the thermal energy of the sunlight, it is far easier for them to use it for heat (mature technology, much better payback period…) than consider it for electricity.

My take on this is that, the cost of solar CSP could come down dramatically as much as that for solar PV if the worldwide R&D into this sector is similar to that for solar PV. It requires serious efforts from investors, R&D and government support to lift solar CSP to the same level as that of solar PV in terms of awareness and investments.

Governments worldwide can help in the following ways to make solar thermal based electricity generation more sustainable:

1. By creating more solar CSP test facilities
2. By providing incentives for industries to develop sub-components (e.g.mirrors, coatings, structures)
3. By pursuing intensively R&D efforts.

What is true for other countries is true for India as well, and it is my submission that the Indian government will do well to invest on the above three points for solar CSP renaissance in India.

In this context, it is good to note that TERI had been active to some extent. Some of its activities have been:
-> Feasibility studies for solar power plants
-> Some projects under finalisation
-> Developing expertise in simulations, solar radiation analysis
-> Investing in and developing R & D capabilities
-> Working on solar park concept based on solar CSP

I also read some positive signals from the market. For instance, in Sep 2009 Abengoa announced they were transfer CSP technology to Maharishi Solar, which would deploy it in India. As part of this association, Abengoa Solar ( http://www.abengoasolar.com )will support Maharishi Solar Technology ( http://www.maharishisolar.com )through technology transfers, training of their staff for design installation and operation of various industrial ventures.

These are good news. Let’s hope there’s more good news on the CSP front in 2010.

You might also be interested in the following post –

Solar CSP in India – Latest Trends

1st CSP Today Concentrated Solar Thermal Power Summit India

Concentrated Solar Power (CSP) and India’s Future Power Needs