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By Ken Zweibel, James Mason and Vasilis Fthenakis
Even the U.S. can become independent of oil: scientists outline the first time in a detailed concept of how it can be powered by solar power by 2050 - the construction of mega solar power plants is by no means unrealistic.
gasoline and heating oil are more expensive, the Middle East, the U.S. also involved in wars for oil, and the demand for fossil fuels will continue to grow - such as China and India. Then threaten future disputes over access to energy resources. Meanwhile emitting coal, oil and gas power plants and motor vehicles annually in the world millions of tons of greenhouse gases - and thereby jeopardize the global climate.
have long been scientists, engineers, economists and politicians made suggestions on how to reduce the consumption of fossil fuels could be gradual. It is not enough. In particular, the U.S. needs a comprehensive plan to escape their dependence on fossil fuels. Our analysis shows that a broad shift to solar energy is the logical answer to this challenge.
reached by sunlight within 40 minutes so much energy on our planet, how we consume the world in one year. The U.S. has the good fortune to have her alone in the southwest at least 650,000 square kilometers of suitable land for the installation of solar power plants. This area receives annually about 5000 EJ solar energy (1 EJ = 1018 joules), the corresponds to approximately 1.3 million terawatt hours. This is a tremendous amount of energy - all nuclear power plants in the world would have with their more than 400 gigawatts of power almost 500 years, generating power to supply that amount. If it were possible, only 2.5 percent of them converted into electrical energy, would be the total energy demand in the U.S. (as of 2006) cover with ease.
would But large areas of land with solar panels and thermal parabolic trough plants are covered and a main route for transport will be established by direct current. The necessary technology is there, and she is ready for use.
Here we present our "Solar Grand Plan". A concept with which be produced in 2050 about 70 percent of electricity needs and 35 percent of the total energy needs, including transport and traffic systems of the United States from solar energy could. This energy could be offered to non-subsidized rates, which correspond roughly to those that we are now paying for energy from conventional sources - about 5 U.S. cents per kilowatt hour (kWh). We also use wind, biomass and geothermal energy sources could cover renewable energies in 2100 even 100 percent of U.S. electricity needs and 90 percent of the total energy demand.
second Part: pay the high costs from
order to realize the concept in 2050, the government should invest in the next 40 years, 420 billion U.S. dollars (280 billion euros). These high costs will pay off: solar power plants need little or no fuel, so year after year billions are saved. The new infrastructure would replace 300 large coal and 300 even more gas power plants. The spent fuel from these plants would be saved, reduced demand for oil imports to zero. At the same time, the U.S. trade deficit could be reduced dramatically, and the political tensions in the Middle East and elsewhere would be mitigated.
Since the production of solar energy almost does not require emissions, greenhouse gas emissions would the power plants at an annual 1.7 billion tons reduced. Another 1.9 billion tons, as blowing vehicles currently in the atmosphere could, by use of plug-in hybrid vehicles save (plug-in hybrids can be charged not only by the internal combustion engine, but also at the outlet). Thus, the CO2 emissions of the United States would in 2050 by more than 60 percent below the year are 2006th
REVOLUTIONARY U.S. SOLAR PLAN
dropped in recent years, production costs for solar cells and modules significantly. The best solar cell types are thin-film cells from cadmium telluride (CdTe). To power in 2020 to provide for 5 cents per kWh may need CdTe solar modules with an efficiency of 14 percent convert. The costs of such facilities should be $ 1.20 per watt. Current modules convert the sun's energy by 10 percent and cost about $ 4 per watt. Further progress is therefore necessary. But last year increased the average efficiency of commercial modules from 9 to 10 percent. Also, photovoltaic panels on roofs, which cover the day a part of domestic electricity consumption, in the course of this development will be more competitive.
In 2050, according to our concept of photovoltaic modules a total of 3,000 gigawatts . Generate This would require the modules with a total area of 80,000 square kilometers will be installed. This project seems to gigantic. Existing systems, however, indicate that in the American Southwest for the generation of a gigawatt hours required land area is smaller than that needed an average of coal plants, if one is also used for the coal mining land into account. Studies of the National Renewable Energy Laboratory (NREL) in Golden (Colorado) show that in the southwestern United States more than enough land is available, without having to ecologically sensitive areas, densely populated areas or difficult to access Terrain would have to fall back.
The most important task is therefore to increase the efficiency of solar panels on 14 percent. Although the effectiveness of commercially available cells will never reach of laboratory products. But the cells of the NREL CdTe already reached 16.5 percent and should be even better.
produce overcast sky solar power plants but little at night and absolutely no electricity. must therefore be stored in sunny hours of energy for evening and night reserve. Most energy storage systems are expensive or inefficient. As a very good alternative, the storage of energy in the form of compressed air has proved. It will air with the aid of solar power in underground caverns, abandoned mines, aquifers (porous rock, the ground lead) or compressed natural gas storage exhausted.
If necessary, the air is discharged and passed through a turbine generating electricity. Before it is heated by burning small amounts of gas still. Since 1978, a compressed air storage plant is operating successfully in the Lower Saxony Huntorf, in McIntosh (Alabama) in 1991 a second plant went online.
third Part: A network of compressed air storage
studies of the Electric Power Research Institute (EPRI) in Palo Alto (California) showed that the cost of compressed air storage are about half as high as the costs for lead acid batteries. Since the suggestion would increase the cost of photovoltaic power by storing 3 to 4 cents per kWh, the total cost in 2020 would thus reach 8 to 9 cents per kWh. About DC high voltage power lines would run from solar farms in the Southwest-based electricity to compressed air energy storage in the country. There could be installed turbines produce electricity all year round without interruption. The decisive factors are the locations. Field studies of the U.S. gas industry and EPRI showed that in three quarters of the country suitable geological formations are present, often close to urban areas.
similar Externally, the compressed air storage systems, the distribution stations for gas, as is common in the USA. The development of such systems is a challenge, but there are many available reservoirs and sufficient reasons for the gas industry to invest in the construction of a compressed air storage network.
Our concept is based on another technology: parabolic trough power plants. They could supply a fifth of the required solar energy. In such systems, long metal reflectors of sunlight is focused onto a tube filled with liquid. Here it is heated and flows through a heat exchanger in which steam is created to drive turbines. To save energy, the liquid may also be passed through large insulated tanks, where molten salt absorbs the heat and saves a few hours. At night, drained the energy and then used to generate steam.
Already since many years, nine parabolic trough power plants generate reliable with a total capacity of 354 MW of electricity. In March 2007, was in Nevada, a new 64-MW power plant on line - but without heat storage. The first commercial power plant with salt storage - it can supply the plant for seven hours with operating heat - is being built in Spain, and further develop in the world. For our project, however, 16 hours required storage capacity, it can be produced around the clock stream.
4th Part: Mass production lowers prices
The cost of parabolic trough power plants must be reduced - by the larger production quantities. A team of solar energy specialists from the Western Governors' Association, which have been governors of 19 western U.S. states together came to the conclusion that parabolic trough power plants by 2015, electricity for 10 cents per kWh (or less) produce could, if power plants with a total capacity of would be 4 GW (gigawatts billion watts) was established.
Neither parabolic trough solar technology is still being developed fully. According to our plan, they should get time to mature by 2020, only to be used on a large scale can. Up then, however, could be other solar technologies are available that meet the economic conditions.
The geographical structure of a solar energy system will differ significantly from the existing system. While coal, oil, gas and nuclear power plants are built anywhere in the U.S. relatively close to consumption centers, most solar systems would be in the southwest. The existing AC power supply system, however, is not powerful enough to transport the electricity from there to the whole country. On long routes, it would lead to large losses. High-voltage direct current lines (HVDC, High Voltage Direct Current) have but over long distances less energy losses than AC lines. An HVDC grid would extend radially from the southwest to the borders of the country and terminate at converter stations, which convert the direct current into alternating current. Through traditional regional lines, he would then be transported to the consumer.
Because today's AC system is overloaded, it has already come to power outages. DC lines are cheaper and require less surface area than AC lines. In the U.S., about 800 km HVDC lines in operation and proved to be reliable and efficient. Major technological advances are no longer necessary, only the current operation would for improvement.
The possibilities for the realization of the Solar Grand Plan, we have carefully checked. Seems appropriate, a two-phase approach: In the first phase, from now until 2020, to solar panels to cheap mass products are. But he has to grant the U.S. government 30-year loan, declare its readiness to conduct solar energy subsidies and pay. From 2011 to 2020, would support the annual increase steadily. Could then solar technology on their own to compete with conventional energy sources. In sum, the government would provide 420 billion U.S. dollars.
In this first phase would photovoltaic and parabolic trough power plants with a total capacity of around 84 GW are installed and the DC power to be expanded - along America's "Interstate" highways where there are already transit rights. The need for land purchases and for obtaining regulatory approvals could be minimized by this. The main route is to purchase large areas such as Phoenix, Las Vegas, Los Angeles and San Diego in the west and San Antonio, Dallas, Houston, New Orleans, Birmingham (Alabama), Tampa (Florida) and Atlanta provide to the east.
come every year in the first five years added 1.5 GW of installed capacity of photovoltaic systems, the same performance contributed new parabolic trough power plants at. For many manufacturers, this would be an incentive to expand their capacity. In the five years following the increase to 5 GW per year per type of power plant is started. The growth helps companies optimize their production so the price of solar power drops significantly.
The timetable is realistic. Alone from 1972 to 1987 were installed in the U.S. each year an average of over 5 GW of power from nuclear power plants. Solar systems, however, can be produced much faster and built - because of its simple structure and reduced environmental and safety problems.
Our scenario for the years 2020-2050 we made conservative assumptions. Technological and cost-effective improvements that could come into play after 2020, we had not taken into account. We also concluded that the power demand increases nationwide by one percent per year. In this scenario, solar power plants supply in 2050 about 70 percent of the electricity produced in the United States, covering 35 percent of total energy demand. These figures also include the power for the operation of 344 million hybrid vehicles. Gasoline-powered vehicles would be displaced, which would contribute significantly to reducing dependence on oil and reduce greenhouse gases. Finally incur approximately three million new jobs, especially in the manufacture of components for Solar power plants - much of the jobs that were lost in the then dwindling oil, gas and coal industries.
would eliminate the fall in oil imports to improve the U.S. trade balance at an annual 300 billion USD (at a crude oil price of 60 dollars per barrel, the average price for 2007 was already at about 74 dollars). Although solar power plants must also be maintained and repaired, but solar energy is free, so the savings will not be repeated during the oil year after year. Also increase the solar installations, the safety of the national electricity supply, reduce costs for the military and reduce its pollution and climate-friendly way of working and social Costs. The Solar Grand Plan will reduce the energy consumption even: Even if the demand would grow by one percent per year, consumption would fall from 105 EJ in 2006 to 98 EJ in 2050! The reason: Today we spend a significant amount of energy to fossil fuels and to prepare to win, more energy is lost in combustion and emission control.
5th Part: How does the world in a hundred years? To achieve
the requirements for 2050, some 120,000 square kilometers in area for the installation of solar photovoltaic and parabolic trough power plants are needed. This number seems huge, but corresponds to only about 20 percent of the land area in the southwest, which is inhospitable and can not use. Thus there is no shadowing, we see in our area calculations from space, we multiply the module surface by a factor of 2.5, to determine the required land area. With parabolic trough power plants, this factor is 3
Accurate forecasts of 50 or more years is impossible. Tentatively, we introduced yet by imputation, to represent the full potential of solar energy in 2100. We went from a total energy consumption of about 150 EJ and the power generation capacity will exceed that year our current seven-fold.
first estimated we the necessary amount of solar power plants. To calculate conservative, we went from a historic low of sunlight to the southwest, as it was recorded in winter 1982 to 1983 and between 1992 and 1993. We also assumed that after 2020 there is no other technological or economic improvements to come, although it is expected in the next 80 years with it. Under these assumptions could be the country's electricity needs are met with the following power plant capacity: 2.9 terawatt of solar photovoltaic power plants would be fed directly into the networks, led another 7.5 TW in compressed air storage. Would add 2.3 TW of parabolic trough power plants and 1.3 TW of distributed photovoltaic installations. Complements would be supplied by 1 TW of wind farms and 0.2 TW of geothermal power plants. The production of biofuels, we sat down to 0.25 TW. The solar plant will be about 430,000 square kilometers of land cover - still less than the Southwest offers.
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Repower America with wind and solar
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may 2100 renewable energy sources meet 100 percent of U.S. electricity needs and 90 percent of the total energy demand. In spring and summer, the solar infrastructure would produce enough hydrogen to 90 percent of fuel demand to provide the entire transportation and communications. Hydrogen could then replace the natural gas that are used in the operation of the CAES turbines must. Additional 180 billion gallons of biofuel would cover the remaining demand for transportation energy. CO2 emissions resulting from energy production and consumption would drop to 92 percent below the 2005 level. And all this despite the anticipated growth of our annual energy consumption by one percent.
6th Part: "Solar Grand Plan" is cheaper than farm subsidies
The most important question is about the financing of the plan. One of the most popular ideas this is the introduction of a carbon tax. The International Energy Agency (IEA) estimates that it would be 40 to 90 dollars per ton of coal so that electricity producers an incentive to reduce by processes for CO2 capture and storage, the emission of carbon dioxide. This tax corresponds to an electricity price increase of 1 or 2 cents per kWh. Our plan is cheaper. The 420 billion dollars, which must throw in the state can be occupied by a tax of 0.5 cents on each kWh of electricity that comes from fossil fuels. At today's costs 60-10 cents per kWh, this seems acceptable.
A national plan for renewable energy sources would ensure the energy supply of the United States and would be a central element of the future well-being the nation. The aid would-successively in the period 2011 to 2020 paid. With a term of usually 30 years, ending the promotion between 2041 and 2050. For the construction of the HVDC network by private companies would have to channel for subsidies, as they power lines and converter stations would be financed in the same way as today's AC power: by the revenue they generate for the supply of electricity.
420 billion U.S. dollars are a lot of money. The annual costs would still be less than the subsidies that flow currently in the U.S. agriculture. They were also less than the tax-financed subsidy in the past 35 years have been invested in upgrading the infrastructure for high-speed telecommunications.
The biggest obstacle to the shift of U.S. energy supply to renewable energy is the lack of public awareness. People with vision should therefore seek to inspire the citizens of the United States as well as leading figures from politics and economy for the almost incredible potential of solar energy. If the Americans realize that potential first, then her desire for sustainable energy supply and reduced CO2 emissions they finally convince them that we must bring the US-wide introduction of solar energy on the road. This
Text is a slightly condensed version of the original text of "Scientific American".
Source: SPIEGEL ONLINE 2008
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