Application of Solar Thermal Energy for Medium Temperature Heating in Automobile Industry

Abstract

There is a huge potential to deploy solar thermal energy in process heat applications in industrial sectors. Around 50 % of industrial heat demand is less than 250 °C which can be addressed through solar energy. The heat energy requirement of industries like automobile, auto ancillary, metal processing, food and beverages, textile, chemical, pharmaceuticals, paper and pulp, hospitality, and educational institutes etc. can be partially met with solar hybridization based solutions. The automobile industry is one of the large consumers of fossil fuel energy in the world. The automobile industry is major economic growth driver of India and has its 60 % fuel dependence on electricity and remaining on oil based products. With abundant area available on roof top, and need for medium temperature operation makes this sector most suitable for substitution of fossil fuel with renewable solar energy. Auto sector has requirement of heat in the temperature range of 80-140 oC or steam up to 2 bar pressure for various processes like component washing, degreasing, drying, boiler feed water preheating, LPG vaporization and cooling. This paper discusses use of solar energy through seamless integration with existing heat source for a few processes involved in automobile industries. Integration of the concentrated solar thermal technology (CST) with the existing heating system is discussed with a case study for commonly used processes in auto industry such as component washing, degreasing and phosphating. The present study is undertaken in a leading automobile plant in India. Component cleaning, degreasing and phosphating are important processes which are carried out in multiple water tanks of varying temperatures. Temperatures of tanks are maintained by electrical heaters which consumes substantial amount of electricity. Non-imaging solar collectors, also known as compound parabolic concentrators (CPC) are used for generation of hot water at required process temperature. The CPC are non-tracking collectors which concentrate diffuse and beam radiation to generate hot water at required temperature. The solar heat generation plant consists of CPC collectors, circulation pump and water storage tank with controls. The heat gained by solar collectors is transferred through the storage tank to the process. An electric heater is switched on automatically when the desired temperature cannot be reached during lower radiation level or during non-sunny hours/days. This solar heating system is designed with CPC collectors that generate process heating water as high as 90OC. It also seamlessly integrates with the existing system without compromising on its reliability, while reducing electricity consumption drastically. The system is commissioned in April, 2013 and since then it has saved ~ 1,75,000 units of electricity/year and in turn 164 MT of emission of CO2 annually.