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| SCIENCE & TECHNOLOGY |
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Turning desert sun into electricity
THIS UNIVERSE |
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Turning desert sun into electricity i) It is virtually free and unlimited after the recovery of initial cost. ii) Depending on its utilisation, paybacks can be very short when compared to the cost of common energy sources used. iii) Solar and other renewable energy systems can be stand-alone i.e. not requiring connection to a power or natural gas grid. iv) No greenhouse gas emissions and v) it is still an untapped market. The concerns about reducing the CO2 emissions to arrest the global warming and future energy supplies have led to a great surge of interest in this technology. The CSP focuses on three types of solar power technologies such as trough systems, dish/engine systems, and power towers. All the three technologies are based on the principle of concentrating the sun’s heat energy and raising the liquid to a high-temperature but they use different kinds of mirror configurations. It works on the similar principle when we use a magnifying lens to focus the sun’s heat rays on a paper to get it catch fire. In trough systems, the sun’s energy is concentrated by the mirrors, which are parabolically curved and trough-shaped. The concentrated energy is allowed to fall on a receiver pipe running along the axis of focus of the curved surface. This energy heats oil flowing through the pipe and the heat energy is then used to generate electricity as done in a conventional steam generator. The collector field comprises the area where many troughs are installed in parallel rows aligned on a north-south axis. The configuration of single-axis troughs tracks the sun from east to west during the day and ensures that the sun is continuously focused on the receiver pipes. An individual trough system can generate about 80 megawatts of electricity. Currently, all such plants are of hybrids nature i.e. they use fossil fuel to supplement the solar output during periods of low solar radiation. In a solar dish engine, the dish is used as a concentrator, which collects the solar energy to concentrate it on a relatively smaller area and an electric generator uses this heat to produce electricity. The dish mirrors made of glass are relatively inexpensive, easily cleanable and can reflect ~92% of the sunlight hitting on them. It makes them an excellent choice for the reflective surface of a solar concentrator. In a power tower system, a power tower converts sunshine into clean electricity for the electricity grids. It utilizes large number of sun-tracking mirrors to focus sunlight on a receiver at the top of a tower, where a fluid is heated to generate steam, which, in turn, is used in a conventional turbine-generator to produce electricity. Acciona Energy, a Spanish company, has opened a solar thermal plant called Nevada Solar One spreading across 400 acres of desert outside Boulder City, Nev., 25 miles southwest of Las Vegas. Ausra, a Las Vegas based company, has supplied mirrors and heat-collecting tubes for the solar plants are made available by a German company, Schott, in Albuquerque. It has 47 miles of trough-shaped mirrors, lined up in rows. The mirrors focus light onto a black pipe with a fluid inside and raise the fluid’s temperature to 750- degree F. The fluid is used to boil water into steam, which turns a generator. Such an individual commercial plant can produce anywhere between 50 and 200 MW of electricity. In earlier power plants, steam was used as the heat transfer fluid in power towers; but the current designs make use of molten salt because of its superior heat transfer and energy storage capabilities. Solar Reserve has invented this new technology to save and store captured solar energy in molten salt. The use of molten salt i.e. a mixture of sodium and potassium nitrate, instead of water or oil, not only enables the power generation in day time but also allows the heat to be stored for use when sun is not present. The National Solar Thermal Test Facility has found that molten salt is the most efficient fluid for transporting sun’s heat as it remains liquid at atmosphere pressure. This property makes it an efficient, low-cost medium to store thermal energy and its operating temperatures are compatible with today’s high-pressure and high-temperature steam turbines. |
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Hole in earth’s magnetic field RECENT satellite observations have revealed the largest breach yet seen in the magnetic field that protects earth from most of the sun’s violent blasts, researchers reported Tuesday. The discovery was made last summer by Themis, a fleet of five small NASA satellites. Scientists have long known that the Earth’s magnetic field, which guards against severe space weather, is similar to a drafty old house that sometimes lets in violent eruptions of charged particles from the sun. Such a breach can cause brilliant auroras or disrupt satellite and ground communications. Observations from Themis show the earth’s magnetic field occasionally develops two cracks, allowing solar wind - a stream of charged particles spewing from the sun at 1 million mph - to penetrate the Earth’s upper atmosphere.
— AP
Galactic diet enforcer Mysterious dark energy, which likely causes the universe to keep expanding, seems to have another effect: It prevents the biggest clusters of galaxies from getting too fat. Astronomers used X-rays to study the formation of galactic clusters billions of years ago. Their research supports the hard-to-fathom concept of dark energy as a potent force that governs the growth of the universe. It also means Albert Einstein’s century-old theory of general relativity passes another crucial, but not conclusive, real-world test. Scientist Alexey Vikhlinin used NASA’s Earth-orbiting Chandra X-ray Observatory to find that dark energy acts as a force that keeps clusters of galaxies - around 1,000 bright galaxies or more - from essentially overeating and getting too big.
— AP
Your mind can be read They hope their study, published in the U.S. journal Neuron, will lead to helping people with speech problems or doctors studying mental disorders, although there are privacy issues if it gets to the stage where someone can read a sleeping person’s dreams. “When we want to convey a message, we need to move our body, for example by speaking or by tapping a keyboard,” said Yukiyasu Kamitani, the project’s head researcher from the Advanced Telecommunications Research Institute International, a private institute based in Kyoto, Japan. “But if we can get information directly from the brain, it will be possible to communicate directly by imagining what we want to say, without having to move,” Kamitani said in a telephone interview with Reuters.
— Reuters
Ice volcanoes on Titan Observations from the international Cassini spacecraft suggest Saturn’s largest moon may have active or recently active ice volcanoes. Radar images point to flows on the surface of Titan that could result from volcanoes spewing chilled liquid from the interior, mission scientists reported Monday. Previous Titan flybys suggested ice volcanoes existed, and scientists believe they would erupt with ammonia, methane and water instead of lava.
— AP |
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THIS
UNIVERSE My mother told me
that excessive use of salt might affect my intelligence. Is that
so? Why? I am sure you mother is a very wise and knowledgeable person. I dare not contradict her especially because I know very little about these things. I can say that excess of anything is not good for you. It is known that salt, because of its sodium ion not allowed to people with high blood pressure. I am sure your mother has also told you that too much sugar is bad for you. This I know because of the tooth trouble one of my grand children is beginning to have. I would advise you to be moderate and listen to your mother. If you do that your intelligence will not be in danger, irrespective of whether her statement is scientifically valid or not. Just like the sound or pictures, is it possible to transmit smell through electromagnetic waves? Electromagnetic waves can carry information, not molecules. Information can code for sound and pictures, which can be generated in the receiving instrument as per instruction, embedded therein. Actual molecules traveling to the receptors in the nose produce smells. These molecules obviously cannot be transported, at the speed of light, from the source to every one who sits down to watch a TV program. On the other hand it is not inconceivable that on the receiving side our sets might be equipped with fragrance capsules that emit whiffs of appropriate smells suited to the scene we are watching. Here again we would be transporting only information, leaving the chore of generating fragrance of the right kind according to instructions to the equipment at the receiver end. It might be even possible to give the choice of the fragrance, its strength and texture, to receivers as we do for the shade and tone of the color on the TV screen! It is a bit complicated but not impossible. We have to remember, of course, that people are more finicky about their smells, than they are about their pictures and sounds. Can you tell us the size of our earth as compared to our milky way? Diameter of the earth is 12,756 kilometres. Diameter of the galaxy is usually given in light years. A light year is the distance light travels in one year. You perhaps know that speed of light is nearly 300,000 km a second. Number of seconds in a year is about 31.5 million. The diameter of the galaxy is 100,000 light years. Now if you do the arithmetic you will find the value of the diameter of the Milky Way galaxy in kilometres. I leave this exercise to you. The earth is very tiny compared to the galaxy. I do not know why sometimes our heads are so bloated! |
THE pressure of growing population and rising per-capita energy consumption has forced humanity to face acute energy crisis. To tide over this crisis, it is required to shift from the polluting and depleting energy supplies, now in use, to renewable energy sources such as conventional solar and wind power. The solar energy seems to be an alternative source as it has the following advantages over conventional energy:
The U.S. Department of Energy (DOE) has developed a clean, large-scale solar thermal technology known as concentrating solar power (CSP). 
Japanese researchers have reproduced images of things people were looking at by analysing brain scans, opening the way for people to communicate directly from their mind.