Augmentation of thermal power stations with solar energy

A new concept of integration of a solar concentrator field with a modern thermal power station is proposed. Such a configuration would utilise the existing equipment and infrastructure as a base load facility and solar energy to reduce the fuel consumption during periods of insolation. The methodology suggested involves feed water heating using a solar concentrator field and consequent reduction of steam extraction presently used for the purpose. Study of retrofit to a 210-MW coal-fired plant indicates that saving of fuel upto 24·5% during periods of insolation can be achieved for feed water heating upto the present level, which is to a temperature of 241°C. The annual saving in coal would be around 47,000 tons at an estimated cost of about Rs. 3 crores. A doubling of the savings, by heating to a higher temperature level of 330°C, is feasible with presently available solar technology. Areas needing detailed study for achieving such an integration are indicated. The control system required to allow for fluctuations in the solar output is outlined. It is felt that the proposed system, where solar energy contributes a small but significant fraction of the total output of the plant, would be easier to control than one where the total energy is provided by solar radiation. A preliminary estimate indicates that the proposed system may cost about half of a stand-alone solar plant with back-up fuel and with the same solar input. However site-specific studies need to be carried out to confirm these figures.