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Converting the solar energy received on the surface of the Earth has not been practical with heat engines because of the low density of this energy. On a clear bright day in the summer, the sun generally delivers less than 80 W per square foot. Also, heat engines are prohibited from exceeding the Carnot-cycle efficiency limit. On the other hand, plants perform their energy conversion electrochemically, and, hence, are not limited by the Carnot-cycle. They use solar energy to produce useful fuels that range from corn-cobs and maple syrup to pitch and firewood. However, they have an extremely complicated process control that uses blue and red parts of the visible solar spectrum to extract hydrogen from water and carbon from carbon dioxide to make hydrocarbons. They do not need precious-metal catalysts; however they run complex data processing programs in which stored instructions control electrochemical reactions and also cause growth and production of needed products to occur when needed. 相似文献
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The Earth's rotation is decelerating at a rate of 8.8×10 exp-20 rad/s. Thus, a leap second is added to the year every two to four years. This deceleration is small, but the Earth weighs 6×10 exp 24 kg. A prony brake that achieves this deceleration would release 5.14×10 exp 11 kW, the equivalent of 514,000 1-GW nuclear power plants. Tides, volcanos, Coriolis-generated ocean currents and winds cannot absorb this much power. This leaves the induction generation which produces the Earth's magnetic field as the most likely absorber of the deceleration power. The efficiency of this inaccessible induction generator cannot be calculated. However, it is thought that correlation of the Earth's deceleration with its 0.09% weakening magnetic field could provide insight into the power generation process 相似文献
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Electric vehicles that can't reach trolley wires need batteries. In the early 1900's electric cars disappeared when owners found that replacing the car's worn-out lead-acid battery costs more than a new gasoline-powered car. Most of today's electric cars are still propelled by lead-acid batteries. General Motors in their prototype Impact, for example, used starting-lighting-ignition batteries, which deliver lots of power for demonstrations, but have a life of less than 100 deep discharges. Now promising alternative technology has challenged the world-wide lead miners, refiners, and battery makers into forming a consortium that sponsors research into making better lead-acid batteries. Horizon's new bipolar battery delivered 50 watt-hours per kg (Wh/kg), compared with 20 for ordinary transport-vehicle batteries. The alternatives are delivering from 80 Wh/kg (nickel-metal hydride) up to 200 Wh/kg (zinc-bromine). A Fiat Panda traveled 260 km on a single charge of its zinc-bromine battery. A German 3.5-ton postal truck traveled 300 km with a single charge in its 650-kg (146 Wh/kg) zinc-air battery. Its top speed was 110 km per hour 相似文献
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Electric utilities need quickly-available sources of power for supplying expected and unexpected peak loads. Among useful sources have been the energy stored in water by pumping it to elevated storage reservoirs, in air compressed into underground chambers, and in batteries. A new power source, tBase-load nuclear and coal-fired steam plants generate off-peak energy for recharging the depleted storage facility. The aero-derived gas turbine, challenges the economics of these traditional energy-storage means. These turbines have been designed for aircraft where quick startup, rapid change in output power, and high reliability are essential. With a 1426°C (2600°F) turbine inlet temperature the available efficiencies are 42% in simple-cycle operation and 60% in a combined-cycle power plant. A recent 84-MW natural-gas-burning peak-power plant cost $204 per kW. Pacific Gas and Electric's Helmes River pumped-hydro plant had cost $656 per kW. The combined-cycle gas turbine plants, with their low manpower requirements, are producing power that costs less than power from nuclear power plants. We examine the performance and economics available from these new power sources 相似文献
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Transportation efficiencies in terms of passenger miles per gallon are examined for a wind range of transportation methods: muscle-powered (running, swimming, flying), human-powered machines (bicycles), and fuel-consuming machines (trains, ships, sailplanes). The practicality of vehicles that can deliver 1000 passenger miles per gallon is evaluated 相似文献
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The possible benefits of using ground power to accelerate the airplane on a launch ramp are quantified. A passenger-carrying hypersonic airplane leaving its loading ramp carries fuel for acceleration, cruise and landing. For example, a 230-passenger plane starting a Mach 5 trans-Pacific flight will be loaded with 80 metric tons of liquid hydrogen, up to 40% of which is burned in generating kinetic energy. Catapulting this airplane to cruise speed with ground power would reduce weight and liquid-hydrogen volume. However, there are limits. A ramp for launching a 150-metric-ton vehicle to Mach 5 with 4 g acceleration would be 38 km long and require up to 10 GW of power. In the final second, 2.8 MWh of energy is consumed along 1720 m of ramp. Possible scenarios and acceleration mechanisms are evaluated 相似文献
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The capability of lead-acid batteries for supplying very high power for a short time is explored. The application of such a battery for accelerating a hypersonic plane is used to illustrate the requirements. A technique for analyzing batteries and controlling voltage for pulse loads is described. Evaluation of lead-acid batteries in production and voltage regulation by switching batteries in and out are covered. Alternatives to batteries, including superconducting magnetic energy storage, are discussed 相似文献
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The calculation of field intensity is briefly reviewed. The effects of DC fields and fields from 60-Hz and three-phase power lines are discussed. Measurement of the field under a 12-kV distribution line is described. The insignificant nature of most exposure is emphasized 相似文献
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This paper gives a review of the papers presented at the IEEE 17th Annual Battery Conference on Applications and Advances, Long Beach, CA, USA, 2002. The topics covered are: Li batteries for satellites, capacity fade of Li-ion cells cycled at different temperatures, Ni-H/sub 2/ battery lifetime, batteries for Mars-exploring vehicles, Li-ion cell performance enhancement at low temperatures, navy service batteries, and US Army man portable applications and mobile power challenges. 相似文献