Energy security and reduction of greenhouse gases for cleaner environment – Most challenging issues of present day:
It has become essential to every nation to access to cheap energy for their smooth functioning and upliftment of their economies. However, the uneven distribution of energy supplies among all the nations and the critical need for energy has led to significant vulnerabilities. Global energy security has become synonym to political stability and good administration.
Political instability of several energy producing countries, the manipulation of energy supplies, the competition over energy sources, attacks on supply infrastructure and accidents and natural disasters are the threat to energy security of any nation. It is also the limited supplies of the most common forms of primary energy, i.e. Oil and Gas that changes perceptions on this topic.
Although plenty of coal, up to about more than 200 years worth, is readily available, almost all over the world, coal is not the fossil fuel of choice for many more advanced countries because of its highly polluting nature. The potential need to change our perception on primary energy sources in the foreseeable future and implementation of new technology, are the solution of the energy security question. Improper planning and ineffective strategies at macro level may lead to higher energy prices, more limited access to sources of energy, competitions and political troubles, which in turn make the threat even larger, as energy plays an important role in the national security of any given country.
One of the leading threats to energy security is the significant increase in energy prices all over the world. Long term measures to increase energy security lies on reducing dependence on any one source of imported energy, increasing the number of sources of energy and suppliers. Greater investment in native renewable energy technologies and energy conservation are envisaged in many of the developed nations. Certainly, every nation’s ultimate goal is to power their entire country with renewable green energy such as solar, wind, and other renewable sources. However, our current technology is not to the point where this would be affordable. Solar and wind do not currently have the energy density to supply us with all the power we need.
Therefore, under the above scenario, on broader sense, two technologies may be very useful and relevant, they are:
(i) Nuclear power, and
(ii) Green-coal power (Clean coal technology).
Nations of developed and emerging economies should think of energy mix of above two technologies in a big way to achieve fair amount of energy security. The raw materials for the above energy mix are present, almost, world over. The cost of power generated by above two technologies and energy mix is also reasonable and within reach of the general population and industries. After all, nuclear power is our one of the best option for clean energy today. In the above energy mix, Hydro-power may also be included, wherever available.
With the huge advances in technology in recent years, any shortcomings we face for the above two mix of energy, can be sorted out easily. Further, dependence on agricultural based biofuel can also be reduced, enhancing chances of availability of more food, thereby reducing poverty.
Green coal for power - To take care of post-Kyoto issues from energy security point-of-view:
a. Coal is the world’s most abundant and important source of primary energy. Turning a potential pollutant into a clean, green fuel for economical power production has become a matter for concern on a global scale. Coal continues to dominate the energy industries as the single most important and widely-used fuel. Delivering around 27 per cent of the world’s consumption of primary energy, almost half of which is used for electricity generation; reserves of coal are spread worldwide throughout some 100 developed and developing countries, sufficient to meet global needs for the next 250 years.
b. Although a combination of economic and environmental pressures has forced the closure of older, inefficient, fossil fuelled thermal stations, the massive growth in power demand on a world scale will continue to be met predominantly by coal-fired plant for the foreseeable future. In many of the rapidly developing and industrializing regions of the world the rate of consumption of coal as a primary fuel for electricity generation is actually increasing. In energy-hungry India alone, coal-burn for power generation is forecast to more than double in the next few years to 350 million tonnes per year. Annual coal production in China, the world’s largest producer, has rocketed to over 1,500 million tonnes. Nevertheless, post-Kyoto issues have heightened environmental awareness, forcing the pace of technological change in the use of this abundant but potentially polluting fuel for power generation. The environmental threat posed by the release of even more millions of tonnes of toxic pollutants, acidic and greenhouse gases from both new and existing coal-burning power stations is widely accepted. Currently, signatories to the Kyoto Protocol are focusing on solutions to the problem of global warming, including the reduction of CO2 and other ‘greenhouse’ gases. In many other non- signatory countries, major programmes have been implemented by utilities and power producers to reduce SOx, NOx and CO2 emissions. Additional environmental concerns have also emerged, including the potential health impacts of trace emissions of mercury and the effects of particulate matter on people with respiratory problems.
c. In contrast with both natural gas and LPG, hard coal can contain a wide range of compounds including sulfur in addition to useful hydrocarbons. The percentage of sulfur can vary widely, with relatively low concentrations in the highest quality anthracite and very high amounts in lignite, generating large volumes of SOx. As well as the need to treat the fuel prior to firing and control closely the combustion process itself to limit the production of nitrogen oxides, coal-fired stations based on conventional pulverized coal technology can only reduce SOx emissions through the use of post-combustion treatments. Further problems still remain through the safe disposal of fly ash which can contain high levels of toxic compounds including heavy metals.
d. Enormous environmental problems faced by operators of older, coal-fired generating plants all over the world, plants were forced to take drastic action after various public protests about the deadly effects of SOx emissions and other emissions. Emissions from coal and lignite-fired units at various power generating stations caused widespread damage, killing livestock and crops downwind of the plant and causing respiratory illness in the population in many countries. The plants were forced to cut output. This tends to place an unacceptably high strain on the commercial viability of an existing power station in many of the developing nations and represents a completely uneconomic option for the majority of obsolescent installations. Power producers in industrialized developed countries are therefore adopting a variety of leading-edge clean-coal technologies for electricity generation.
e. New clean coal technologies are providing an attractive and economically viable option to post-combustion systems. Applying the latest combustion, steam and process technologies in new power plant or upgrading existing coal-fired generating facilities provides significant improvements in thermal efficiency, reducing environmental impact and energy costs to the consumer. At the same time, higher thermal efficiencies result directly in reduced fuel costs, improving profitability and market position for the independent power producer.
(i) For new and smaller coal-fuelled generating plant, boilers using well-proven circulating fluidized-bed CFB technology provide a cost-effective and efficient system capable of meeting current and future environmental standards. They are now being widely used and successfully operated in coal-fired generating units, burning a very wide range of coal and other fuels with widely differing heat values and mineral content. These can typically include anthracite, semi-anthracite, bituminous and sub-bituminous coal, lignite and even ‘gob’ – a form of high-ash bituminous coal waste.
(ii) As an alternative to direct combustion based systems, coal gasification is becoming increasingly attractive, with Integrated Gasification Combined Cycle (IGCC) technology offering one of the best ‘clean’ options for effective power production. Gasification systems use steam and controlled amounts of air or oxygen under high temperatures and pressures to react with coal to form clean synthetic gas or ‘syngas’. Current systems provide efficient clean-up of the gas-stream to produce a mixture of carbon monoxide and hydrogen which can be used subsequently as a ‘clean’ fuel or a basic feedstock for liquefaction.
f. Used as a fuel for power generation in a typical IGCC generating plant, a syngas-fired gas turbine drives a generator, with exhaust heat from the gas turbine recovered to produce steam to power a steam turbine in conventional ‘combined cycle’. IGCC power generating systems are presently being developed and operated in Europe and the US, with commercial systems capable of operating at thermal efficiencies approaching 50 per cent. NOx and Sox emissions levels are minimized with the potential for carbon-capture and sequestration of the CO in the sysngas stream being actively researched as design strategies for near-term and future coal-based IGCC plants. Elemental sulfur is removed from the syngas before combustion and is a highly saleable commercial byproduct. If the gasifier is fed with oxygen rather than air, the flue gas contains highly concentrated CO2 which can readily be captured, at about half the cost of that from conventional plants.
g. As an alternative to the direct use of syngas as a fuel for electricity generation, it can also be processed using modern gas-to-liquids (GTL) technologies to produce a wide range of liquid hydrocarbon fuels such as gasoline and diesel oil. Coal-to-oil is a long-established technology in coal-rich South Africa.
h. Nevertheless, clean coal technology is moving very rapidly in the direction of coal gasification, with a second stage designed to produce a concentrated and pressurized carbon dioxide stream followed by separation and geological storage. This has the potential to provide extremely low emissions of conventional coal pollutants, and as low-as-engineered carbon dioxide emissions – a vital step in the fight to prevent irreversible climate change.
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