In the backdrop of dwindling fossil fuels and burgeoning environmental pollution, it is imperative for communities to ensure prudent consumption of conventional energy resources.
While this can be achieved by adopting energy-frugal lifestyles at individual level, reduction in inefficiencies during power generation can contribute significant fuel savings and ensure lesser carbon emissions. A number of technologies are being employed in power generation industry to recover waste heat, thereby improving energy conversion efficiency.
Combined Heat and Power (CHP) or Cogeneration
Commonly known as cogeneration, combined heat and power technology is the simultaneous generation of electricity and heat in power plants. While traditional power units release almost 70 percent of fuel energy to the environment in the form of waste heat, a significant portion of this waste heat can be reclaimed and used for district heating; thus, cutting down fuel consumption per unit of power generated with a proportionate drop in carbon dioxide emissions.
CHP is a useful technology fulfilling the objectives of fuel savings and environment conservation; however, in recent years, smaller gas-fired power units, called micro CHP, are replacing large coal-fired cogeneration power plants. Further to the use of CHP and micro-CHP units, a preferred choice in electrical power industry is combined cycle gas turbines.
Combined Cycle Gas Turbines (CCGT)
In a combined cycle gas turbine, jet engines are used to drive an electric generator, while the hot exhaust gases are used to produce steam for running a two-stage steam turbine. Attributed to availability of gas at cheaper rates compared to coal and the ease in installation of gas turbines, medium-sized combined cycle gas turbines have been a popular choice.
Although CCGT technology is not as energy-efficient as CHP, burning of natural gas produces much lower volumes of carbon dioxide per kilowatt-hour compared to coal burning power plants. Nonetheless, coal based power units cannot be fully replaced with gas units, as coal reserves are more extensive at the global scale.
Clean Coal Burning Technologies
There are two primary technologies for cleaning up emissions from coal-fired power plants: fluidized bed coal combustion and integrated gasification combined cycle (IGCC). While fluidized bed combustion of coal is comparatively energy- efficient and lowers environmental penalties like acid rain, IGCC- conversion of coal to a gas prior to burning in CCGT- facilitates easier carbon sequestration.
Improving Energy Efficiency in Power Generation
Energy efficiency technologies like cogeneration and combined cycle gas turbines aim at reclaiming waste heat from power units. On the other hand, clean coal burning technologies such as coal gasification and fluidized bed combustion ensure lesser carbon dioxide emissions, in addition to enhancing efficiency in energy conversion. However, these technologies are still in development phase and may not prove cost-effective.
Source
2003, Elliot, David, Sustainable Energy: Choices, Problems and Opportunities, The Royal Society of Chemistry
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Zeeshan Amin - I am a professional mechanical engineer with a diverse experience of over 5 years with Honda Cars, Shell Oil and Nestle.
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