To replace conventional energy sources, a renewable energy would have to have to provide:
• Dispatchable power: power needs to be available when the primary customers (the utilities, and their consumers and industrial customers) need it. An energy source should therefore have a high capacity factor. Utility base load plants are designed to achieve power generation over 65% of the hours in a typical year.
• Cost effective power: To be as cost effective as a fossil source, a renewable source must produce power at about $0.10 per KWh. Peak load power can afford somewhat higher costs of around $0.12 - $0.15 per KWh.
• Reliable power: Any source vying to replace coal-based electric power should be as reliable as that technology.
Solar PV is not likely to scale up massively in the near future because of its high cost and variability. Wind power is also unlikely to scale beyond about 10% of our grid electricity needs partly because of its high variability.
Geothermal can provide another 10% and because of built in heat storage it can meet many utility requirements if it can be produced cost effectively. Enhanced geothermal energy is the solution to scalable geothermal power. Enhanced geothermal is simply an extrapolation of naturally occurring hydrothermal systems, using artificial geothermal wells. It operates as follows:
1. Drill a production-injection well into hot rock (the rock in question should have limited permeability).
2. Inject water into the well at a pressure high enough to cause fracturing, until fractures extend a significant distance from the initial well.
3. Drill multiple injection wells around the initial production well, with the intent of overlapping the fracture system
4. Circulate water to capture the heat from the rock, which can then be used to generate power.
Solar thermal concentrates the sun's rays to heat a fluid to generate steam that can then run a regular steam turbine. Its great advantage is that the heat can be stored cheaply either as steam, hot water, molten salt or hot oil and used when the sun's heat is not available. Storing this energy using batteries would be prohibitively expensive and battery technology costs are not declining very rapidly.
Advantages of solar thermal energy compared with other sources of renewable energy
• Low price-variability and supply-availability. CSP bears no transportation, supply or commodity price risk.
• Low land requirements and high siting potential. The total space required to power Europe would be equivalent to about 3% of the land of Morocco. The sun intensity constraint could be reduced by building a high voltage DC power grid for long distance electricity transmission.
• Decreasing cost. Capital and operating costs are both likely to be lower than nuclear. Solar thermal is about 75% cheaper than solar PV.
• Ability to reach capacity factors of 65% and hence supply base power needs.
Source: V. Khosla
dimanche 31 août 2008
Downside of coal
One of the common criticisms regarding renewables vs. coal is that the latter is cheap – a misguided perception, based, among other things, on not pricing in externalities like pollution.
A typical 500 MW coal plant generates 3.7 billion tons of carbon dioxide, as much as cutting
down 100 million trees. In 2004, coal accounted for around half of the electricity produced in the U.S. but produced roughly 83% of the resulting carbon dioxide emissions from electric power generation. Coal-fired power plants emit twice as much CO2 per KWH as any other form of power generation. According to the Union of Concerned Scientists, one 500 MW coal plant produces as much emissions as 600,000 cars.
Additional pollutants emitted by coal power plants include sulphur dioxide, nitrogen dioxide, as well as carbon monoxide, arsenic, lead mercury and cadmium. A coal plant can even generate uranium and thorium.
Should the cost of CO2 emissions be included using a conservative $20 per ton of CO2 emission, the price of coal would increase by 2-4X. Two technologies could help reduce the carbon footprint of coal – Integrated Gasification Combined Cycle (IGCC) and Carbon Capture and Storage (CCS).
IGCC technology involves two major processes:
• The gasification of coal, a process in which coal is reacted with steam and oxygen to form syngas, a combination of carbon monoxide and hydrogen. The syngas is then cleaned to remove pollutants.
• A combined cycle process to generate electricity. The produced syngas is then used as the main fuel for a gas turbine (which produces electricity), while the waste heat generated by the gas turbine is used to power an second, steam turbine (additional electricity production), thus increasing the energy efficiency of the plant as a whole.
In theory, IGCC produces less solid waste, lower emission levels (as a result of better efficiencies) as compared to pulverized coal. Aside from consistency and reliability issues, the key question is whether the capital costs of IGCC will be able to fall as projected with learning and increased economies of scale in manufacturing, engineering and so forth.
CCS brings its own host of problems and cost issues. In 2005, carbon dioxide emissions were at least 27.9 billion metric tons. Sequestering just 10% of the world’s fossil-fuel combustion CO2 would require an industry whose throughput would have to be 1.3 times that of the oil industry. Moreover, both the sheer scale and cost of the project remain unknown, as are the safety and operating reliability conditions.
Another approach could be to convert coal to an environmentally friendlier fuel, such as natural gas. Advantages of such a process include the ability to use the transportation infrastructure in place.
Source: V. Khosla
A typical 500 MW coal plant generates 3.7 billion tons of carbon dioxide, as much as cutting
down 100 million trees. In 2004, coal accounted for around half of the electricity produced in the U.S. but produced roughly 83% of the resulting carbon dioxide emissions from electric power generation. Coal-fired power plants emit twice as much CO2 per KWH as any other form of power generation. According to the Union of Concerned Scientists, one 500 MW coal plant produces as much emissions as 600,000 cars.
Additional pollutants emitted by coal power plants include sulphur dioxide, nitrogen dioxide, as well as carbon monoxide, arsenic, lead mercury and cadmium. A coal plant can even generate uranium and thorium.
Should the cost of CO2 emissions be included using a conservative $20 per ton of CO2 emission, the price of coal would increase by 2-4X. Two technologies could help reduce the carbon footprint of coal – Integrated Gasification Combined Cycle (IGCC) and Carbon Capture and Storage (CCS).
IGCC technology involves two major processes:
• The gasification of coal, a process in which coal is reacted with steam and oxygen to form syngas, a combination of carbon monoxide and hydrogen. The syngas is then cleaned to remove pollutants.
• A combined cycle process to generate electricity. The produced syngas is then used as the main fuel for a gas turbine (which produces electricity), while the waste heat generated by the gas turbine is used to power an second, steam turbine (additional electricity production), thus increasing the energy efficiency of the plant as a whole.
In theory, IGCC produces less solid waste, lower emission levels (as a result of better efficiencies) as compared to pulverized coal. Aside from consistency and reliability issues, the key question is whether the capital costs of IGCC will be able to fall as projected with learning and increased economies of scale in manufacturing, engineering and so forth.
CCS brings its own host of problems and cost issues. In 2005, carbon dioxide emissions were at least 27.9 billion metric tons. Sequestering just 10% of the world’s fossil-fuel combustion CO2 would require an industry whose throughput would have to be 1.3 times that of the oil industry. Moreover, both the sheer scale and cost of the project remain unknown, as are the safety and operating reliability conditions.
Another approach could be to convert coal to an environmentally friendlier fuel, such as natural gas. Advantages of such a process include the ability to use the transportation infrastructure in place.
Source: V. Khosla
Nuclear power pros and cons
Pros and cons of nuclear energy
Nuclear power plants emit neither carbon dioxide, nor sulphur or mercury. Currently, the 104 nuclear power plants in the U.S. generate about a fifth of the nation’s energy. Wind accounts for about 1% and solar even less. Nuclear can meet power demand 24 hours a day, in contrast with solar and wind.
Nuclear power can help, even if it won’t solve the whole problem. In the short to medium term, it is probably too late for nuclear power to make a material difference in carbon emission, given nuclear power's slow political, legal and technological development cycle.
Critics argue that nuclear energy has significant capital and decommissioning costs. Those capital costs have risen significantly lately, and there is a debate as to whether nuclear energy is still economic.
The high cost of nuclear power may be ascribed to two factors: a lack of experience in building plants as well as shortage of parts and skills, both due to the fact that no new plant has been started in the U.S. since 1977. But if new plants are started, construction timing will become more predictable, bringing financing costs down as lenders become more comfortable. At the same time, the number of companies supplying parts and providing engineering will increase to meet the demand, lowering the price.
Most important, nuclear power appears economically uncompetitive primarily because the price of fossil fuels doesn’t reflect the high cost that carbon emissions pose for the environment. Should the price of environmental degradation be taken into account either through a direct tax based on the carbon content of a fuel or a so-called cap-and-trade system, fossil-fuel would look much less competitive compared with low-carbon sources, such as nuclear, wind and hydropower. It is estimated that a carbon price of between $25 and $50 a ton makes nuclear power economically competitive with coal.
By far the greatest risk it the possibility that an expansion of nuclear power will contribute to the proliferation of nuclear weapons. Plants that enrich uranium for power plants can also be used to enrich it for bombs. The dangers of nuclear proliferation would be heightened if a nuclear revival turned to reprocessing of spent fuel to reduce the amount of high-level waste that builds up and to maintain adequate fuel supplies. Reprocessing is a problem because it can produce separated plutonium – which is easier to steal or divert for weapons production, than plutonium contained in highly radioactive fuel.
Source: WSJ, 30/06/08
Nuclear power plants emit neither carbon dioxide, nor sulphur or mercury. Currently, the 104 nuclear power plants in the U.S. generate about a fifth of the nation’s energy. Wind accounts for about 1% and solar even less. Nuclear can meet power demand 24 hours a day, in contrast with solar and wind.
Nuclear power can help, even if it won’t solve the whole problem. In the short to medium term, it is probably too late for nuclear power to make a material difference in carbon emission, given nuclear power's slow political, legal and technological development cycle.
Critics argue that nuclear energy has significant capital and decommissioning costs. Those capital costs have risen significantly lately, and there is a debate as to whether nuclear energy is still economic.
The high cost of nuclear power may be ascribed to two factors: a lack of experience in building plants as well as shortage of parts and skills, both due to the fact that no new plant has been started in the U.S. since 1977. But if new plants are started, construction timing will become more predictable, bringing financing costs down as lenders become more comfortable. At the same time, the number of companies supplying parts and providing engineering will increase to meet the demand, lowering the price.
Most important, nuclear power appears economically uncompetitive primarily because the price of fossil fuels doesn’t reflect the high cost that carbon emissions pose for the environment. Should the price of environmental degradation be taken into account either through a direct tax based on the carbon content of a fuel or a so-called cap-and-trade system, fossil-fuel would look much less competitive compared with low-carbon sources, such as nuclear, wind and hydropower. It is estimated that a carbon price of between $25 and $50 a ton makes nuclear power economically competitive with coal.
By far the greatest risk it the possibility that an expansion of nuclear power will contribute to the proliferation of nuclear weapons. Plants that enrich uranium for power plants can also be used to enrich it for bombs. The dangers of nuclear proliferation would be heightened if a nuclear revival turned to reprocessing of spent fuel to reduce the amount of high-level waste that builds up and to maintain adequate fuel supplies. Reprocessing is a problem because it can produce separated plutonium – which is easier to steal or divert for weapons production, than plutonium contained in highly radioactive fuel.
Source: WSJ, 30/06/08
CSP technologies
Algeria’s government is building an experimental solar-thermal power station at Hassi R’mel, about 400 km south of Algiers, which if all goes well will open next year. In April, work started on a similar project at Aïn Béni Mathar, in Morroco.
There are four competing solar thermal power designs:
• Parabolic-trough mirrors,
• Parabolic-dish mirrors
• “power towers” which use an array of mirrors to focus to sun’s rays on to an elevated platform,
• Fresnel systems, which mimic a parabolic trough using (cheaper) flat mirrors.
All four of these designs are now either operating commercially or undergoing pre-commercial trials. Although the total capacity at the moment, according to Cambridge Energy Research Associates, is a mere 400 megawatts, this will grow tenfold over the next four years if all projects now scheduled come to fruition.
Source: The Economist, 19/06/08
There are four competing solar thermal power designs:
• Parabolic-trough mirrors,
• Parabolic-dish mirrors
• “power towers” which use an array of mirrors to focus to sun’s rays on to an elevated platform,
• Fresnel systems, which mimic a parabolic trough using (cheaper) flat mirrors.
All four of these designs are now either operating commercially or undergoing pre-commercial trials. Although the total capacity at the moment, according to Cambridge Energy Research Associates, is a mere 400 megawatts, this will grow tenfold over the next four years if all projects now scheduled come to fruition.
Source: The Economist, 19/06/08
Carbon capture technology
Fossil fuels make up two-thirds of the global energy mix and would still make up almost half by midcentury - even under scenarios where annual emissions are kept at the same level as today. That is why many experts say developing carbon capture technologies is critical in the fight against climate change.
Statoil of Norway is already pumping under the seabed significant quantities of unwanted carbon dioxide from a natural gas field. Sonatrach, the Algerian natural gas and oil company, has a similar project to store unwanted carbon dioxide at its In Salah field. In Canada, EnCana, an energy company, injects unwanted carbon dioxide piped from a coal gasification plant in the United States into its Weyburn, Saskatchewan, field to make it easier to recover hard-to- reach oil.
These and other experiments show that carbon dioxide can be trapped underground with little or no leakage. But commercial-scale facilities to capture and bury the carbon emitted by utilities and installations like refineries still do not exist. Two high-profile projects - one in Scotland led by the British oil company BP, and another in Illinois led by a consortium called FutureGen that includes the coal giant Xstrata - were dealt setbacks over the past year because of ballooning costs and shortfalls in public funding.
Source: IHT, 23/07/08
Statoil of Norway is already pumping under the seabed significant quantities of unwanted carbon dioxide from a natural gas field. Sonatrach, the Algerian natural gas and oil company, has a similar project to store unwanted carbon dioxide at its In Salah field. In Canada, EnCana, an energy company, injects unwanted carbon dioxide piped from a coal gasification plant in the United States into its Weyburn, Saskatchewan, field to make it easier to recover hard-to- reach oil.
These and other experiments show that carbon dioxide can be trapped underground with little or no leakage. But commercial-scale facilities to capture and bury the carbon emitted by utilities and installations like refineries still do not exist. Two high-profile projects - one in Scotland led by the British oil company BP, and another in Illinois led by a consortium called FutureGen that includes the coal giant Xstrata - were dealt setbacks over the past year because of ballooning costs and shortfalls in public funding.
Source: IHT, 23/07/08
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