CLIMATE CHANGE ------WHY? REMEDY!

Climate change is now widely recognized as the major environmental threat of the globe. Climate change is defined as any long-term change in the patterns of average weather of a specific region or the Earth as a whole. Climate change reflects abnormal variations to the Earth's climate and subsequent effects on other parts of the Earth over durations ranging from decades to millions of years.Impacts are being felt in the form of melting icecaps in the polar areas and increased variability of temperature, rainfall and storms in virtually all regions.

Global warming is the increase in the average temperature of the Earth's near-surface air and oceans since the mid-20th century and its projected continuation. The Intergovernmental Panel on Climate Change (IPCC) concludes that increasing greenhouse gas concentrations resulting from human activity such as fossil fuel burning and deforestation are responsible for most of the observed temperature increase since the middle of the 20th century. The IPCC also concludes that natural phenomena such as solar variation and volcanoes produced most of the warming from pre-industrial times to 1950 and had a small cooling effect afterward.


The Earth’s Greenhouse Effect

What Are Greenhouse Gases?

Many chemical compounds found in the Earth’s atmosphere act as “greenhouse gases.” These gases allow sunlight to enter the atmosphere freely. When sunlight strikes the Earth’s surface, some of it is re-radiated back towards space as infrared radiation (heat). Greenhouse gases absorb this infrared radiation and trap the heat in the atmosphere. Many gases exhibit these “greenhouse” properties. Some of them occur in nature (water vapor, carbon dioxide, methane, and nitrous oxide), while others are exclusively human made (certain industrial gases). Over time, if atmospheric concentrations of greenhouse gases remain relatively stable, the amount of energy sent from the sun to the Earth’s surface should be about the same as the amount of energy radiated back into space, leaving the temperature of the Earth’s surface roughly constant.

How much of green house gas emissions are made of CO2 ?

Roughly 72% of Green House Gases are made up of Carbon Dioxide.

Annual Greenhouse Gas Emissions by Sector

The Energy Connection . . .


Fossil fuels are made up of hydrogen and carbon. When fossil fuels are burned, the carbon combines with oxygen to yield carbon dioxide. The amount of carbon dioxide produced depends on the carbon content of the fuel; for example, for each unit of energy produced, natural gas emits about half and petroleum fuels about three-quarters of the carbon dioxide produced by coal.

Fossil fuels supply 85 percent of the primary energy consumed in the United States and are responsible for 98 percent of emissions of carbon dioxide. Eighty percent of U.S. carbon dioxide emissions come from the use of coal and petroleum fuels. Although the industrial sector is the largest energy consumer (including direct fuel use and purchased electricity), the transportation sector emits more carbon dioxide because of its near complete dependence on petroleum fuels. The residential and commercial sectors have lower emission levels than the transportation and industrial sectors, with the majority of their emissions coming from the combustion of fossil energy to produce purchased electricity.

Electricity generation consumes 40 percent of U.S. primary energy and is responsible for 40 percent of carbon dioxide emissions. In the electric power sector, coal accounts for 83 percent of the emissions.



What is the Prospect for Future Emissions?

World carbon dioxide emissions are expected to increase by 1.8 percent annually between 2004 and 2030. Much of the increase in these emissions is expected to occur in the developing world where emerging economies, such as China and India, fuel economic development with fossil energy. Emissions from the countries outside the Organization for Economic Cooperation and Development (OECD) are expected to grow above the world average at 2.6 percent annually between 2004 and 2030.

Coal fired power plants form part of the generation portfolio in most countries, but has the disadvantage of relatively high levels of carbon dioxide emissions. They are perceived as a major factor in CO2 emissions leading to global warming. But a number of solutions – short and long term – can put coal on a level with other technologies.

Against the advantages, coal suffers from the disadvantage of having the highest level of carbon dioxide (CO2) emissions, close to 1 MT of CO2 per MWh generated for the majority of plant installed around the world. This is twice the level associated with modern gas fired generation.



Remedy

There are many solutions to the reduction of CO2 emissions from coal fired power plants. In the short term, major improvements in CO2 emissions from pulverised coal fired plant are possible by:

1. Improvements in generation efficiency (giving a reduction in CO2 emissions per megawatt of electricity generated), either via new supercritical/ultra-supercritical plant or upgrade of existing plant to make it energy efficient through renovation and modernization of older power plants.
2. By substituting a fraction of the coal with biomass (biomass co-firing), biomass being CO2 neutral. Modern coal fired boiler designs are capable of accommodating up to 20 per cent biomass co-firing, with a corresponding reduction in CO2 emissions.
3. Use of advanced concepts in plant integration.
4. 4) CO2 reduction by IGCC (Integrated Gasification Combined Cycle) plant.

Simultaneous adoption of all four improvements outlined above would reduce CO2 emissions from coal based thermal power plants by 50-60 per cent to a level comparable to a modern gas fired plant.

Carbon capture and storage (CCS)

A longer-term solution is CO2 capture and geological storage (CCS). This involves a chain of technologies for CO2 capture, transportation and storage.

Post-combustion capture, in which the CO2 is separated from flue gases.

Pre-combustion capture, in which the CO2 is captured prior to combustion generally by a shift reaction to convert fuel gases to CO2 and hydrogen.

Carbon capture and storage (CCS) is an approach to mitigate global warming by capturing carbon dioxide (CO2) from large point sources such as fossil fuel power plants and storing it instead of releasing it into the atmosphere. Although CO2 has been injected into geological formations for various purposes, the long term storage of CO2 is a relatively untried concept and as of 2008, no large scale power plant operates with a full carbon capture and storage system.

CCS applied to a modern conventional power plant could reduce CO2 emissions to the atmosphere by approximately 80-90% compared to a plant without CCS.

IGCC technology and its benefits

IGCC is one of the cost effective solution if electricity is to be generated from coal in the most environment friendly manner by capturing the sequestering CO2. In IGCC, CO2 is captured from high pressure synthetic gas in the pre-combustion stage. In conventional steam power stations, CO2 is to be captured from a large volume of flue gas, which makes it complex and costly.

Other benefits which accrue from IGCC plants in comparison to conventional coal fired plants are:

• Low rank and low cost fuels like pet coke, heavy refinery residue, biomass, lignite can be used.
• Less SO2, NOX and particulate matter emission.
• Less CO2 emission. Less water demand.
• Less land in comparison to conventional pulverized coal fired power plant.

Super-critical and ultra super-critical power plants

• Average efficiency of sub-critical coal plant - 36 to 38%
• Efficiency of newer super-critical coal plant - 43 to 45%
• Efficiency of most advance super-critical coal plant - up to 50%
• 1 % increase in plant efficiency reduces 2 % CO2 emission

Super-critical technology reduces green house gas emission to 750 gms of CO2 per KWh compared to India’s national average of 1259 gms CO2 per KWh with sub-critical technology. World’s average is 919 gms CO2 per KWh. Average for OECD countries are 888 gms CO2 per KWh.

4000 MW ultra mega power project will avoid burning 1.7 MT of coal per year. This will in turn avert 3.6 MT of carbon emission per year.

This approach is resulting in the reduction of CO2 emissions by 7% in ultra-supercritical pressure power generation, compared with current sub-critical pressure power generation. Accordingly, adoption of supercritical technology is the only environment friendly option for all future coal fired thermal power plants to be implemented in 12th/13th plan.



Nuclear energy: The clean air energy
- A remedy for the greenhouse effect?

In the framework of the international negotiations on global climate policy the nuclear industry is trying to get nuclear energy accepted as a tool in the struggle against the greenhouse effect. They claim nuclear energy will contribute to the solving of the climate crisis. Over the last years, nuclear energy has been portrayed as an useful tool in the battle against the greenhouse effect.

In addition to the economic benefits achieved through the use of nuclear energy, there are environmental benefits as well. There are, however, various drawbacks caused by the production of electricity through nuclear power. Although there are various risks involved when using nuclear energy as a source of power, we argue that the benefits greatly outweigh any potential problems that may arise.


Nuclear Safety

National and international anxiety about nuclear power stems directly from a fear of release of radioactive material and its consequences on people and the environment. The problem, however, is that there is a huge information gap between specialists on the exposures from nuclear power and the public. When one looks at the 1991 report by the United Nations Scientific Committee on the Effects of Atomic Radiation, (UNSCEAR) one would see that the routine generation of nuclear electricity releases only negligible amounts of radioactive materials to the environment. "The average dose any individual in the world receives each year from all of the activities in the peaceful nuclear fuel cycle is less than 0.1 percent of the inevitable exposures he or she receives from natural radiation sources, such as cosmic rays and radon emitting building materials".

One has to accept that electricity production can't be totally free of risk. The accident at Chernobyl, in the former USSR, was undoubtedly the most severe radioactive accident the world has experienced since the arrival of nuclear energy as an alternative source of electric power.


Nuclear Waste


Another drawback that is often associated with the use of nuclear energy is that of nuclear waste. There is a huge misunderstanding that the waste created by nuclear energy is more "dangerous" than that of other means of producing electricity. The truth of the matter is that radioactive waste from nuclear energy may be dangerous for thousands of years, while wastes resulting from the burning of coal, remains dangerous forever. The reason for this is because the toxicity of these stable elements does not decrease over time as does the toxicity of radioactive materials.

Other interesting facts concerning nuclear waste include the reduction in emissions of SO2 and NOX in countries using nuclear power is revealing. "In France, for example, during the period from 1980 to 1986, SO2 and NOX emissions in the electric power sector were reduced by 71 percent and 60 percent, respectively, making a major contribution to reductions of 56 percent and 9 percent, respectively, in total SO2 and NOX emissions in France". These tremendous reductions were made possible by a fourfold increase in nuclear electricity generation.

One positive result from the tragic Chernobyl accident is that there is now increased awareness and commitment of the nuclear community to international cooperation in the field of safety. "Through the efforts of utilities and governments, of the IAEA and others, an international nuclear safety regime is emerging, which includes a wide range of arrangements for improving operational safety and emergency preparedness and response to accidents".


The fact of the matter is that nuclear power plants are safer today than ever before, and they will be unquestionably safer tomorrow than today.


Overall, nuclear energy has proven to be most beneficial to our society. As a result of this technology, the United States has decreased its dependency on foreign-imported oil. In fact, the United States saves about 12 billion dollars each year through the lack of oil it imports from other nations. Nuclear energy has also proven to be a protector of the environment because of the lack of CO2, greenhouse gasses, and other gases it emits into the atmosphere. There are, however, some major drawbacks to using nuclear energy. These drawbacks include the actual safety of using nuclear energy, the waste it produces, and the atomic weapons that nuclear energy promotes. Overall, however, it is a fact that the use of nuclear energy greatly outweighs any other source of energy over the decades.

Non-conventional Energy

Renewable Energy is the green energy which is derived from the natural resources which are renewable in nature. Some of the major examples of the renewable energy resources are the tidal energy, solar energy and the wind energy. Renewable resources of energy are those resources which never run out; they are always available in abundance. Wind power is considered to be major renewable energy source and is growing in use.

This is an inexhaustible supply and technologies are evolving to make use of these processes for conversion to usable energy.

Clean Energy is the energy which had been generated from the non-polluting, harmless and clean methods. Most of the renewable resources of energy can be considered as the sources of clean energy, but there are some exceptions. Clean energy is very much beneficial for our environment. They can be useful in preventing the global warming as they emit very less amount of carbon dioxide.

In 2006, about 18% of global final energy consumption came from renewables, with 13% coming from traditional biomass, such as wood-burning. Hydroelectricity was the next largest renewable source, providing 3% of global energy consumption.

Wind energy is the fastest growing energy resource in the world and can economically produce scalable renewable power to meet growing energy demands.Wind power is growing at the rate of 30 percent annually, with a worldwide installed capacity of 121,000 megawatts (MW) in 2008, and is widely used in European countries and the United States.

D Dey, Prepared on 25.06.2009

References used:-
1) http://en.wikipedia.org/wiki/Global_warming
2) http://en.wikipedia.org/wiki/Greenhouse_effect
3) http://rashidfaridi.wordpress.com
4) http://www.gov.mb.ca
5) http://science.howstuffworks.com/nuclear-power5.htm