19-07-2012, 12:52 PM
thermoelectric waste heat energy
thermoelectric waste heat energy recovery system .doc (Size: 4.44 MB / Downloads: 45)
INTRODUCTION
Even a highly efficient combustion engine converts only about one-third of the energy in the fuel into mechanical power serving to actually drive the car. The rest is lost through heat discharged into the surroundings or, quite simply, leaves the vehicle as “waste heat”.
Until just a few years ago, however, such thermoelectric generators (TEGs) were unsuitable for use in the automobile due to their low level of efficiency. But since significant progress has been made in materials research in recent times, the performance and output of such modules has increased significantly. To generate electric power in the vehicle a thermoelectric generator is integrated in the exhaust gas manifold.
While the electric power such a system is able to generate is still relatively small at a maximum of 200 W, rapid progress in materials research already makes the ambitious objective of generating up to 1,000 W a realistic and by all means feasible proposition. This energy regeneration system also offers additional effects, such as providing the engine or the heating system with extra heat when starting the engine cold. In future thermoelectric generators will be able to reduce fuel consumption under realistic, customer-oriented driving conditions by up to 5 per cent.
AUTOMOBILE APPLICATIONS
The utilization of waste heat energy from exhaust gas gases in reciprocating internal combustion engines (e.g. automobiles) is another novel application of electricity generation using thermoelectric power generators. Although reciprocating piston engine converts the chemical energy available in fossil fuels efficiently into mechanical work substantial amount of thermal energy is dissipated to the environment through exhaust gas, radiation, cooling water and lubricating oils. For example, in a gasoline powered engine, approximately 30% of the primary gasoline fuel energy is dissipated as waste heat energy in the exhaust gases; waste heat energy discharged in the exhaust gas gases from a typical passenger car travelling at a regular speed is 20-30 Kw. A comprehensive theoretical study concluded that a thermoelectric generator powered by exhaust gas heat could meet the electrical requirements of a medium sized automobile.
INDUSTRIAL WASTE HEAT APPLICATIONS:
Most of the recent research activities on applications of thermoelectric power generation have been directed towardsutilisation of industrial waste heat. Vast amounts of heat are rejected from industry, manufacturing plants and power utilities as gases or liquids at temperature which are too low to be used in conventional generating units (<450 K).
CURRENT & FUTURE DEVELOPMENTS:
Recently, an increasing concern of environmental issues of emissions, in particular global warming and the constraints on energy sources has resulted in extensive research into innovative technologies of generating electrical power and thermoelectric power generation has emerged as a promising alternative green technology. In addition, vast quantities of waste heat are discharged into the earth’s environment much of it at temperatures which is too low to recover using conventional electrical power generators.