Thursday, February 24, 2011

Solar 4:

Solar Thermal

Solar Thermal is the answer to the sector that may not be adequately catered to by Solar PV. In Solar Thermal, Sunlight is concentrated by reflectors at a point or line, and the circulating medium that can be air, water or salt is heated to relative high temperatures varying between 70deg C to 500degC.Initially only solar water heaters were developed in this sector and remains to be the mainstay of it. However large Power Plants have been built for more than a decade now. Once water or any other liquid is heated at sufficiently high temperatures of 300-500 deg C, the rest is standard steam turbine electricity generation. All one may have to do is to replace the coal or oil or gas fired boiler with a Solar Heating/boiler system. For a variety of reasons, however, integration with combined cycle plants has been found to be more feasible, and implemented under the term ISCC(Integrated Solar Combined Cycle). Cost of a complete system producing electricity is high but competitive generally with Solar PV. There is another advantage to this system .Thermal energy can be stored much more economically and large volumes than electricity produced in PV. Five hours of storage at full load has become a common feature of large scale utility plants of 50-100 MW.

Spain has gone into it with much more commitment and investments. More than a dozen plants of 50 MW are already working there, and more are coming in, although under a highly supportive subsidy system in the form of very high feed-in tariff. This is obvious we cannot afford this kind of feed-in tariff, already there is a lot of social unrest on unaffordable tariff, which otherwise is quite competitive with other countries. GOP has been giving subsidies of Rs 200 billion per year to the electrical sector to sustain the existing tariff level. These subsidies have infact paid for the exceptionally high T&D losses and theft and pilferage. So theoretically, GOP could have afforded some subsidies to encourage Renewables and foster technology development, had these kinds of losses not been there. These subsidies now have to go under IMF pressure and tariff is to be raised. But some subsidy can be maintained on the account of Feed-in Tariff for renewables, if a reasonable scheme is developed for creation and support of this technology.

Technology differentiation within Solar thermal.

There are four technologies within Solar Thermal, largely depending on what kind of concentrating system is employed. That is the reason, it is also called Concentrated Solar Power (CSP), although CSP systems have been used in Solar PV as well. The four technologies are;

1)Parabolic troughs

2)heliostats and Solar Towers

3)Linear reflectors 4)Solar dish

Essentially the difference is whether one focuses sunlight on a point like a furnace or a boiler or one does it in on a line or tube carrying a fluid. Parabolic troughs have been more popular, cheaper and are now an established technology. Parabolic troughs are more prone to indigenization, as it is mostly sheet metal work and structures and framing made out of steel. There is some glass work or plastic for reflectors requiring electroplating. Considerable know-how both in formal and informal sector exists in Pakistan and other developing countries like us in this area. It is labor intensive as well. A number of our sick industries in Public sector could be revived by technology arrangements and orders in this field. Also private sector and informal sector can be strengthened.

Building a Solar Thermal (parabolic trough) Power Plant

According to the figures released by US Energy Information Administration, in January 2010,a solar thermal power plant to come on stream in 2012 would cost 4798 USD per kW. It takes three years to implement a 100 MW solar thermal power plant. If one deducts 1798 USD per KW for conventional power component, the solar component cost would be 3000 USD per KW i.e. more than 60% of the total project cost. It requires 25000 tons of steel, 12000 tons of glass and 20,000 cubic meters of concrete among major inputs. It is not round bar construction steel, although some of it is, but mostly it is steel fabrication supporting my argument that we can do it, and we will have comparative advantage in it. Over the years cost s and steel consumption would come down, but the nature of steel construction may not change. By comparison, a large coal power plant of600-1000 MW would require steel structures of 5000 tons, which in itself is a large number. Recently an ISCC plant built in Egypt under World Bank/GEF assistance generated a demand of some 4000 tons of steel fabrications for 15 MW only and should have kept the local company busy for one whole year round the clock. Such is a potential of comparative advantage and job creation in ordinary technology of steel fabrication required in Solar thermal. There are associated technologies in glass, and control system which can be bought or partially developed locally.

Solar thermal in the Middle East

Morocco, Egypt, Iran, Algiers and recently UAE have gone into this, but in a very cost effective way. They, except UAE, have launched solar –augmented combined cycle plants running on gas. Parabolic Troughs have been installed to cater to10-20% of the total fuel requirements of the combined cycle plants. We can do the same in one or more of our existing plants. All these projects, except Iran and UAE, have been financed under GEF.UAE is pursuing two tracks; one for Solar thermal power and the other Solar air-conditioning. A 100 MW Solar thermal has been contracted for, which is to be commissioned by 2012.

Admittedly, there is more solar insolation in countries around Sahara than in South Asia. DESERTEC project has been launched, presently under negotiation, through which electricity produced through Solar Thermal plants installed in Sahara, would be transmitted to Europe through HVDC (a cost effective DC technology as opposed to conventional AC) network, to meet some 20% of the power needs of Europe. Although Terrorism issues may prevent or delay the implementation of DESERTEC, the faith and confidence in Solar Thermal is adequately demonstrated by this EU project. DESERTEC like projects are being encouraged in other countries which have desert. Regional counterpart organizations and arrangements like DESERTEC-India, Asia have been formed. We have Thar, Thal and Cholistan. If Thar Coal gets going finally, there would not much scope there for any thing else. Thus Cholistan can be readied for such ventures.

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