Solar Process Heat Generation
The present Solar Water Heating System uses flat plate collectors wherein the water temp. can be raised up to 80 0 C. They provide heat of 1800 Kcal per m2 of collector area and cost of the system including storage, piping is Rs.5000 / m2 for a collector area of 30-72 m2. This system is now commercially viable.
So far, in India, the use of solar thermal energy is mainly limited to domestic hot water and low temp. heat. Such systems used for heating the boiler feed water contributes 30 to 50 Kcal / Kg. of steam produced which is an insignificant part of the total thermal energy requirements, thus making a small contribution to the
Various types of industries consume large quantities of steam, mostly up to 2000 C and 10 Kg / m2 pressure. It was felt by MEDA that prospects of utilization of solar thermal energy for industrial applications in medium temp range (1250 C 2000 C) is large.
The medium temp. applications use steam in most industries and it can be generated using solar concentrating technology. In India no significant work is done in this technology and the efforts made are dispersed.
Over the last two decades, concentrating solar collectors have been used but their use is limited due to high cost technology. Advancement in the field led to reduction in costs from Rs.40, 000 / m2 to Rs.12500 / m2. The analysis of costs shows major cost component of the system is the structural frame and there are chances to reduce costs to Rs.5000 / m2 for the 50 -100 m2 model due to use of alternative material for the structural frame, low engineering costs and spare fabrication facilities available at competitive prices.
Heat in the form of steam cost about Rs.2.50 / 1000 Kcal for oil fired boiler, Rs.1.00 / 1000 Kcal for coke. In case of flat plate solar thermal system, the cost is around Rs.1.60 / 1000 Kcal and for solar concentrating collector, it would be around Rs.0.85 / 1000 Kcal and is quite compatible with the cost of coke.