Практическое задание по дисциплине «Английский язык» для ЕКурсы

Перевод текстов. TEXT 1 POWER SYSTEM SERVICES PROVIDED BY HYDROPOWER Hydroelectric generation differs from thermal generation in that the quantity of ‘fuel’ (i.e., water) that is available at any given time is determined by river flows leading to the hydroelectric plant. Storage hydropower can largely decouple the timing of hydropower generation and variable river flows. For large storage reservoirs, the storage may be sufficient to buffer seasonal or multi-seasonal changes in river flows, whereas for smaller reservoirs the storage may buffer river flows on a daily or weekly basis. With a very large reservoir relative to the size of the hydropower plant (or very consistent river flows), HPPs can generate power at a near constant level throughout the year (i.e., operate as a base-load plant). Alternatively, in the case that the hydropower capacity far exceeds the amount of reservoir storage, the hydropower plant is sometimes referred to as energy-limited. An energy-limited hydropower plant would exhaust its ‘fuel supply’ by consistently operating at its rated capacity throughout the year. In this case, the use of reservoir storage allows hydropower generation to occur at times that are most valuable from the perspective of the power system rather than at times dictated solely by river flows. Since electrical demand varies during the day and night, during the week and seasonally, storage hydropower generation can be timed to coincide with times where the power system needs are the greatest. In part, these times will occur during periods of peak electrical demand. Operating hydropower plants in a way that generates power during times of high demand is referred to as peaking operation (in contrast to base-load). Even with storage, however, hydropower generation will still be limited by the size of the storage, the rated electrical capacity of the hydropower plant, and downstream flow constraints for irrigation, recreation or environmental uses of the river flows. Hydropower peaking may, if the outlet is directed to a river, lead to rapid fluctuations in river flow, water-covered area, depth and velocity. In turn this may, depending on local conditions, lead to negative impacts in the river unless properly managed. Hydropower generation that consistently occurs during periods with high system demand can offset the need for thermal generation to meet that same demand. The ratio of the amount of demand that can be reliably met by adding hydropower to the nameplate capacity of the hydropower plant is called the capacity credit. In addition to providing energy and capacity to meet electrical demand, hydropower generation often has several characteristics that enable it to provide other services to reliably operate power systems. Because hydropower plants utilize gravity instead of combustion to generate electricity, hydropower plants are often less susceptible to the sudden loss of generation than is thermal generation. Hydropower plants also offer operating flexibility in that they can start generating electricity with very short notice and low start-up costs, provide rapid changes in generation, and have a wide range of generation levels over which power can be generated efficiently (i.e., high part-load efficiency). The ability to rapidly change output in response to system needs without suffering large decreases in efficiency makes hydropower plants well suited to providing the balancing services called regulation and load-following. Overall, with its important load-following and balancing capabilities, peaking capacity and power quality attributes, hydropower can play a significant role in ensuring reliable electricity. TEXT 2 THE MAGNETOSPHERE The magnetosphere is the region dominated by Earth’s magnetic field. It sits in the solar wind which is the atmosphere of the Sun, a fully ionized, hot, collisionless, magnetized plasma. About 95 % of the plasma consists of protons and electrons in nearly equal numbers, and the remainder is mostly ionized helium with smaller numbers of heavier ions. The solar wind is supersonic above a few solar radii and is capable of carrying a large amount of kinetic and electrical energy. At Earth’s orbit, the typical proton and electron densities are around 7 cm-3, velocity about 440 km s-1, producing a dynamic pressure of about 2 nPa. The interplanetary magnetic field (IMF) embedded in the plasma is around 7 nT. In Fig. 2, a charged particle approaching Earth from the sunward side will be deflected around Earth, but this simplistic view is missing key aspects of the dynamical process that shape the magnetosphere, including mechanisms for particles to populate the Van Allen radiation belts and associated magnetospheric ring current. An accessible review of large-scale magnetospheric structure and dynamics begins with the Chapman-Ferraro (CF) problem, ignoring the inter-planetary magnetic field (IMF), treating the solar wind as electrically neutral (but ionized) and the magnetosphere as a vacuum. The dominant effect is then compression of field lines by the solar wind from the pressure of streams of particles which are repelled by the geomagnetic field at the magnetopause, generating the CF currents, and producing the magnetospheric cavity. The balance of internal magnetic pressure against that of the solar wind determines the size and shape of the CF magnetosphere boundary. The compression of the magnetic field on the sunward side is communicated across the vacuum to Earth via gradients in the magnetic field. This CF base model does not include any effects of magnetic tension, and it must be modified to accommodate the fact that the high electrical conductivity and supersonic speeds in the solar wind cause the magnetic flux associated with the IMF to be carried along with the charged particles. A typical wind turbine consists of a number of components: rotor, controls, drivetrain (gearbox, generator, and power converter), tower, and balance of system. In general, the balance of system (BOS) is the system between the technologies that convert the renewable flux (wind or solar) into electricity and the electricity grid (for power production) or load (for direct use). The BOS might include the power-conditioning equipment that adjusts and converts the DC electricity to the proper form and magnitude required by an alternating current (AC) load. For solar PV, the BOS consists of the structure for mounting the PV arrays and storage batteries. For wind turbines, it typically includes all the related electronics required to provide the connection to the grid. TEXT 3 SOLAR AND WIND ENERGY Solar Panel Energy Most renewable energy comes either directly or indirectly from the sun. Solar energy can be used for generating electricity, and for hot water heating and solar cooling. Solar energy is produced when the sun is shining during the day and is complementary to wind energy, which tends to reach its highest production at night. Concentrated solar power uses mirrors to reflect and concentrate sunlight onto receivers that collect the solar energy and convert it to heat. This thermal energy can then be used to produce electricity via a steam turbine or heat engine driving a generator. Photovoltaic solar technology uses photovoltaic cells (PV) to convert sunlight directly into electricity. PV cells are made of semiconductors and can provide large amounts of power for the electric grid. Using solar energy produces no air or water pollution and no greenhouse gases. Solar energy is predictable and is most efficient when utility rates are the highest. We are an energized society. Everywhere you look people are talking on cell phones, driving cars, using computers, cooking food, turning on lights, and so much more. Can you imagine trying to go an entire day without electricity? Even if you could put your phone away and read a book instead of watching TV, you’d have to shut down all of the traffic lights, use candles in your house, and either walk or bike to work. And that’s just YOU! Think of all the hospitals, power plants, and other facilities that require a constant supply of energy in order to keep people safe and healthy. Energy sources that can be regenerated are great to take advantage of for our massive energy needs. In fact, we already utilize some of these resources, like wind, water, and the sun. Let’s look more closely at each of these to see how we can benefit from them and in turn power our lives. Windmills are becoming a common sight across the United States because they are incredible power-producing machines. The wind turbines you see in fields, along coasts, and even in people’s backyards convert wind energy into electrical energy. The blades of the turbine spin as the wind blows, which then turns a mechanism inside the structure. This mechanism is attached to a generator, which is what produces usable electricity. The wind is going to blow whether we use it for generating electricity or not. But there are ways to make windmills more efficient. For example, most modern windmills are about 130-325 feet tall. This is because higher up, wind speeds are faster and there’s less turbulence. Sometimes a household will have a single windmill on their property for their own power generation. But more often, you’ll see a bunch of windmills hanging out together in a wind farm. Just like a large agricultural farm produces a lot of food, a wind farm produces a lot of energy from wind, so the more turbines, the better.Wind power is one of the most efficient ways to generate electricity. This means that we get much more from it than what we put in: twenty to twenty-five times as much, in fact! This is more than nuclear energy and natural gas combined. Wind power isn’t perfect, though. First, you can only generate electricity from wind if you have wind in the first place. Some places are windier than others, so if you live in a fairly stagnant area, you may not have much luck. Those big rotating turbine blades also pose a hazard to flying animals, like bats and birds. However, they are not nearly as dangerous as moving vehicles, power lines, and window-covered buildings.