Asian Development Bank has approved a loan of $135 million to facilitate the construction of an Integrated Gasification Combined Cycle power plant. Although the power plant will be using coal as the primary fuel it air pollution and greenhouse gas emissions from the plant will be lower than the conventional coal-fired power plants.
An Integrated Gasification Combined Cycle power plant converts coal into gas through the process of gasification. Once the coal has been converted in synthetic natural gas or syngas, the resulting mixture of gases, mainly comprising of hydrogen and carbon monoxide, is filtered to remove particulate matter. The filtered gas is then ignited using highly compressed air. The flue gases resulting from the combustion of the gas mixture is fed into a gas turbine which is connected to a generator which produced electricity.
The IGCC power plants are efficient because they use the exhaust gases from the gas turbine to convert water into steam through an Heat Recovery Steam Generator which principally works as a heat exchanger that utilizes the heat content of the exhaust gases coming from the gas turbine. The steam thus produced is then fed into a steam turbine which also produces electricity through another generator.
The efficiency of such power plants is higher than the conventional gas-fired or coal-fired power plants as they utilize the energy content of the exhaust gases from the gas turbine. Conventional coal-fired power plants burn the coal directly to generate steam and release the exhaust gases into the atmosphere without extracting any work. These power plants have high thermal efficiency and produce lesser amounts of sulfur dioxide and carbon dioxide emissions, in addition the exhaust gases are also free from particulate matter which are captured during filtration.
The average efficiency of coal-fired power plants in China is around 33.2% (IEA: Focus on Clean Coal Report, 2006) but the thermal efficiency of combined cycle power plants is usually 40% and can be increased if the temperature of the flue gases fed into the gas turbine is increased.
Such power plants could prove to be bridges between the carbon-intensive conventional coal-fired power plants and the renewable energy based power plants. Developing countries like China and India which are highly dependent on coal for power generation can use these power plants to boost their economic growth an providing low cost power to the poor while limiting the amounts of greenhouse gas emissions.
The problem, though, with such plants is the high capital cost. The per unit cost of generation as compared to coal-fired power plants is higher in case of IGCC power plants. But still, as the ADB notes, they are the cheapest way of reducing carbon emissions as compared to other even more expensive and untested technologies. The cost of generation is expected to match that of conventional power plants as governments around the world launch cap and trade schemes.
Even more efficient, cheaper and cleaner power plants are the ones using Combined Cycle Gas Turbine. In such power plants, natural gas is directly used as the fuel thus eliminating energy requirement for gasification and filtration. China has substantial gas reserves with new and larger finds being reported frequently – CNOOC found three underwater gas fields in the South China Sea, one of which has been verified to have reserves of 100-150 billion cubic meters.
Using combined cycle based power plants developing countries can not only avoid immediate transition to expensive and less efficient renewable energy based technologies but can also reduce their carbon outputs. Both India and China have announced targets for reducing carbon intensities (carbon output per unit GDP).
As the developing countries look to set up more of such power plants the trend could potentially result in increase in production of equipment required and reduction in capital costs. Additionally, these power plants would gradually become more popular as carbon offsetting and trading schemes kick in.
Developed countries, especially those which are against setting up of coal-fired power plants in the developed countries, must support such power plants through financing and technical assistance.
Image Credit: wallyg (Under Creative Commons License)
The views presented in the above article are author’s personal views and do not represent those of TERI/TERI University where the author is currently pursuing a Master’s degree.
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