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Power from the earth’s heat
Blue whale colony Prof Yash
Pal THIS UNIVERSE |
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Power from the earth’s heat The earth’s heat or geothermal energy has tremendous potential for electricity generation. All around the world, about 8,000 megawatts (MWs) of geothermal electricity are currently produced. Today’s technology produces electricity from hot water or steam resources of earth. In the future, it would be possible to use the heat of the deep, hot, dry rock formations of earth’s crust and possibly even deeper, almost the limitless energy contained in earth’s magma.
The geothermal energy circulates within the earth rocks and gets transferred to the underground water reservoirs below the earth’s crust. The source of this energy is the hot magma. This hot magma maintains the continuous supply of heat between subsurface rocks and water reservoirs unabated. This energy is not new to the mankind. Since the dawn of civilisation; it has been in use for cooking, bathing and heating of the houses. With the advent of technology and burgeoning needs of electricity, the geothermal energy is used for electricity generation. The geothermal resources are usually located along the major plate boundaries where earthquakes and volcanoes are frequent. In these areas, the heat flow is near enough to the earth’s surface to bring steam or hot water to the surface. These reservoirs can generally be classified into two types such as low temperature (<150 `B0C) and high temperature (>150 `B0C). Only the high temperature reservoirs are suitable and most sought after for electricity generation. Today, there are three types of the geothermal electricity generation technologies. Dry Steam: Dry steam reservoirs are rare but highly efficient. The geysers in California is the largest known dry steam plant. Here, the steam is obtained by drilling wells to a depth of 10,000 feet. The natural steam is directly fed to power a turbine engine for producing electricity. The unused steam or condensed water is either utilised for cooling system of the plant or injected back into the reservoir to maintain the water and pressure levels in the reservoirs. Flash Steam: The flash steam plants are commonly used geothermal reservoirs for power generation. The plants utilise the water at temperatures greater than 180 `B0C. This hot water is pumped from wells under high pressure to the generating equipment. Here, the pressure of hot water is suddenly reduced to flash it into steam. The steam, then, drives the turbine generator to produce electricity. The hot water, which has not flashed into steam, and the water condensed from steam, is injected back into the reservoir. The dry steam and flash steam based plants contain some traces of hydrogen sulphide (a gas that smells like rotten eggs), some gases and chemicals that can be harmful when in the high concentrations. But by the use of scrubber systems, these gases can be converted into marketable products like liquid fertilisers. However, the use of binary cycle geothermal power plants eliminates the release of harmful gases. Binary Cycle: In a binary cycle plant, the water or steam from the geothermal source never comes in direct contact with the turbine and generating unit (Fig). Here, water from the geothermal well is circulated through a heat exchanger, where the hot water transfers its heat to a working fluid. The working fluid gets vaporised and propels the turbine generator. As the hot water or steam from geothermal wells is kept confined in the pipes, therefore, there is no question of air emissions to cause any pollution. These plants have the advantage of operating with lower temperature waters (105-180 degree C) that even by making use of a working fluid (isobutane or isopentane) having a melting point lower than that of water. The Mammoth Pacific binary geothermal plant at the Casa Diablo geothermal fields is an example of a binary cycle plant.
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Blue whale colony Scientists
say they have discovered one of the world’s most important blue whale colonies off the coast of Chile, where the endangered animals appear to be staying for the summer instead of migrating south to the Antarctic to feed according to their traditional migratory patterns. “What we are seeing is one of the biggest feeding and breeding sources, at least in the southern hemisphere,” Ernesto Escobar, a spokesman for the Ballena Azul (Blue Whale) project, said. The project has been studying the animals in Chile for the past four years. The research team has just returned from three months studying the whales in the Gulf of Corcovado, off the remote island of Chiloe in Chile’s south, in association with the BBC, which will be showing the trip on its Planet Earth programme. On the trip, 65 blue whales and 51 humpback whales were sighted “which confirms the existence of one of the most important whale habitats in Chile and the planet”, Ballena Azul said in a statement. “The population of blue whales in Corcovado shows us that a large number do not migrate to Antarctica,” Mr Escobar said. Blue whales are the biggest animals ever to have lived but were hunted to the brink of extinction during the first half of the 20th century till a ban in 1965. Whaling was especially savage in the southern hemisphere, where the International Whaling Commission estimates only 400 to 1,400
remain.
— By arrangement with The Independent, London
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THIS UNIVERSE A friend told me that if the rope pulling up a lift breaks the lift will not experience a free fall. If this is correct please tell me why. Your friend is correct. This is not because the laws of physics do not work for lifts. It is because all lifts are protected against such an eventuality. It is easy to provide a failproof mechanism that would sense the speed of descent of the lift. If the speed exceeds the prescribed limit the sensor operates the brakes that safely bring the descending lift to a stop. These brakes work, of course, against the guide rails of the lift. One can also ensure that once the lift is stopped this way the brakes keep clutching the
rails. Photon is a bundle of energy. Energy is equivalent to mass. Does the photon have a mass in reality? Photon has a zero rest mass. But it can have energy and momentum. For a photon its energy is proportional to its frequency. It is usually written as hv. Here h is the Planck constant and v the frequency of light. Its momentum is hv/c, where c is the velocity of light. Understanding this was one of the major breakthroughs during the first decade of the
last century. Photons have no rest mass. They are affected by gravity like particles that have mass. They are not slowed down or accelerated in velocity when they interact with other particles; instead their energy change results in the change of
their frequency. The moon goes around the earth once in 27.3 days, while a lunar month is 29.5
days. Why the difference? It is true that the moon makes one rotation around the earth in 27.3 days. A lunar month is the number of days between two new moon days. After one new moon day the moon does arrive at the same position with respect to the fixed stars after 27.3 days. But it is not aligned with the earth and the sun because during this period the earth has moved some distance around the sun, indeed by about 27°. So the moon has to move some more to come to a position between the sun and the earth. A simple calculation shows that this additional traverse would take about 2.2 days. Therefore the next new moon comes after 29.5 days and not 27.3 — the lunar month is longer than the period of rotation of the moon by about two days! Does Europa, a moon of Jupiter, contain any life? And what about the hidden side of the moon? The only answer I can give is: There is no positive evidence in either case. Incidentally, the hidden side of the moon is hidden from us only because its orbital period around the earth is the same as its rotation period. Surely that cannot give the hidden part any special advantage for developing life.
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