Viewing, reading and discussing, too, scan attacks to find out which paragraphs described the pictures above. Toward clean, sustainable energy, future science has reached a consensus that we need to eliminate our usage of fossil fuels such as coal, gas and petroleum, and turn to clean and sustainable power sources. Here are some examples. Hydro power. Hydrox power is the use of the movement of water to generate electricity. In the past, this was mostly done through the damming of rivers and using the water to turn huge electric turbines. Overall, hydro electric dams are among the most used and most successful forms of alternative energy. The main constraint with hydro electric dams are that you need a river with plenty of water, and the damming of a river can create a huge reservoir that destroys natural habitats and displaces people. Another form of hydrox power is generated from motion waves and tides. This form of alternative energy shows great promise as most of the earth's surface is covered with oceans. However, building a tidal power generator can be quite expensive and requires overcoming considerable practical issues. In addition, some of the most effective designs for generating electricity also killed small fish, thereby causing ecological problems. Nuclear power in theory, nuclear power should be both safe, unsustainable. Many countries have nuclear power plants that used the heat from splitting the nucleus of atoms in a process called nuclear efficient to run steam turbines. However, one objection to nuclear efficient is that IT produces toxic nuclear waste with a half life of thousands of year. Further, after a series of disasters involving nuclear efficient plants, there are serious questions about their inherent safety. An alternative is nuclear fusion. This uses the heat generated from combining the nuclear of atoms to run steam turbines. There is enormous potential for this form of energy, as IT uses the same process that the earth sun uses to generate heat. What's more, IT is quite safe from possible disasters and produces nuclear waste with a very short half life. However, up until now, nuclear fusion power plants have been more theoretical than practical. So far, IT has not proven feasible to build a fusion reactor that can generate more electricity than IT uses. Until this issue has been overcome, there is little hope for nuclear fusion solar power. There are two main kinds of solar power. One kind solar thermal energy, uses heat from the sun as an energy source. In its simplest form, IT can amount a little more than a low temperatures solar panel installed on the roof of a house, which uses the sun's heat to heat water and warmer house. There are also high temperatures solar thermal energy plants that used mirrors to focus the heat from the sun on steam or gas turbines in order to produce electricity. Such power plants are usually not very practical, as they must be built in desert areas covering an extensive amount of territory. Another kind of solar power is photo vote power. This uses solar cells, which convert light from the sun into electricity. This has tremendous potential. However, the initial cost of these solar cells can be quite high and thus too expensive for many people or governments to afford, regardless of the kind of solar power. The main issue is that the sun only shines for part of the day, and on cloudy or rainy days, a solar power plant may not work very well or at all. Thus, there needs to be a way to store the solar energy, so IT can be used when the solar power is done. While there are ways to store this energy, such as batteries, storing energy can add so much to the expensive solar power plants that some scientists have suggested putting a solar power plant in space that would always face the sun and transmitted energy to the earth. Wind power, wind power uses giant blades turning in the wind to generate electricity. Unlike solar power, wind power can Operate day and night. However, wind power has significant issues, for example, when turbines are idle, when the wind is not blowing. In addition, the mechanisms can be quite noisy. Y and many people assert that wind farms are ugly and spoil the natural scenery. Finally, when turbines are responsible for killing many birds, these liabilities deterred many people from using wind power despite its vast potential. These are the main forms of alternative energy that are being used today. All have their good and bad points, but used together, they make clean, sustainable energy for the future possible.