Архив рефератов (Копия alferov)Посмотреть архив целиком
Humankind has only one alternative under the circumstances.
“Solar Energy Conversion is Our Only Future in Power Sector”. That’s the title of a report by Academician Zhores ALFEROV, it concluded a series of public lectures delivered by 20 Nobel Prize winners in St. Petersburg.
Man hasn’t yet learned how to handle the gifts of Nature with care, even after achieving unprecedented results in science and technology. Basic estimates show that our descendants may face the most serious energy crisis a few generations from now, should the energy consumption rate continue to rise. It is confident that such crisis will be a catastrophe to the human race. According to International Energy Agency, energy consumption, to put it simple, will double while its year-on-year increase will be mere 1.5 percent. Investment in the energy sector is estimated at $4.6 trillion to cover the cost of the escalating needs.
However, our insatiable appetite is restricted by natural resources. They are sweepingly running dry. Experts say that the world oil reserves will run thin in 40 or 50 years, natural gas reserves will be spent in 60 or 70 years and coal will follow suit in 300 or 400 years. Reserves of cheap uranium that is used to produce energy on thermal neutrons will last for another 120 years. Nuclear energy produced on fast neutrons enjoys the most optimistic outlook. In this field we have one and a half thousand years to make up our minds.
In my opinion, nuclear and thermonuclear power engineering are the leftovers of the programs for the development of nuclear and thermonuclear arms, to a certain extent. The above programs begot the nuclear power engineering in the USSR, USA, Great Britain and France. If not for those programs, nowadays we would talk about the nuclear power engineering as energy belonging to the distant future. When scientists worked hard to build an atomic bomb, then a hydrogen bomb, the Devil may have looked after the results, but God didn’t mind for the Soviets did so with good intentions – to counterbalance a monopoly on nuclear arms. Thank God, the cold war never turned into real hostilities. But I really doubt that God likes the idea of another man-made sun on earth, I mean the launching of a thermonuclear reactor. Scientists have been working for fifty years to make it happen and still we have a long way to go. A test run of the first thermonuclear reactor is scheduled to commence in 2006 or 2007, but only six years after it will be switched into a steady combustion mode. Experts reckon that another fifty years should pass before a thermonuclear reactor can be used industrially.
Humankind has only one alternative under the circumstances. The conversion of solar energy doesn’t disrupt the ecological balance and thermal balance of our planet. It’s possible to convert the solar energy using the semi-conducting photocells. The third Soviet satellite and an American satellite “Vanguard” launched in 1958 were powered by solar silicic batteries. The first solar batteries on the basis of common p-n junctions were manufactured between 1955 and 1956, and in 1970 the solar batteries were installed on the Soviet moon rover “Lunokhod”. Their efficiency rate was 11 percent at 130 degrees Celsius.
However, there’re many skeptics who don’t believe in the bright outlook for two reasons. First, they say, solar energy is diffused, therefore vast areas of the precious land will have to be allocated for solar batteries to ensure a sufficient capacity. But that’s not true. With 20 percent of the efficiency rate, solar batteries will have to cover a little more than one percent of the continental part of the U.S. to ensure all domestic energy consumption in 2020. Secondly, it’s a matter of cost. It’s true that so far the solar energy conversion costs more than that of the nuclear power engineering. The problem can be easily solved by enhancing the photocells efficiency. We hope that the development of semiconductor heterostructures and the use of various physical phenomena will change the situation. These phenomena were introduced in the 1950s. The first semiconductor heterostructures of gallium-aluminum-arsenic were successfully tested aboard the “Mir” space station. Seventy square meters of the solar batteries of that type endured 15 years of uninterrupted operations.
We’ve made considerable progress on our road to enhance photocells efficiency rate. We built cascade heterostructures featuring three, five, ten p-n junctions. In our experiments involving the use of photocells made of gallium arsenide and gallium antimonide we reached an efficiency rate ranging from 32 to 33 percent. Solar photocell has an efficiency rate limit of 93 percent. Imminent internal loss cuts down the number to 85 percent. We could reach for these figures by using the cascade photocells. Hopefully, technological setbacks will be overcome during the next 5 or 10 years. Humankind will be able to enjoy a new era where solar power engineering will play the lead. The world production of photocells is already on a steady increase. Total capacity of photocells produced in 2002 was 520 megawatts. USA, EU countries and Japan hold the leading positions. Top international oil companies manufacture the photocells these days. It’s understood. They think about the future. Fortunately, nobody can privatize the Sun, but we can use his energy. It’s about time we used it. There’s no other alternative to the power sector.