Alternative energy. On the picture below you can see the types of alternative energy

ALTERNATIVE ENERGY

On the picture below you can see the types of alternative energy. Tell how they can be used and whether they are efficient comparing to traditional forms of energy.

2. You are going to watch the video about different types of alternative energy (http://www.youtube.com/watch?v=-1EIhowgtgA). Take notes. Be ready to write a short summary. Point out the main ideas of the presenter.

Read the text and fill the gaps with appropriate passages.

Alternative energy

Energy comes in many forms — heat, light, sound, electrical and mechanical. There is no shortage of energy in the world. If you stand on the beach on a windy day you can see the strength of the wind and the waves, and the powerful burning light from the sun.

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Wind power has been used for hundreds of years in the form of the old-fashioned windmill, which converted one form of mechanical energy (wind) into another (the milling process).

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Wind .power is clean and plentiful, and an aerogenerator does no damage to the environment. But aerogenerators are noisy, and the electricity cannot be stored easily for calm days. Wind power cannot, of course, be used in places where there is not much wind! Aerogenerators are best, sited in coastal or mountainous areas. The Aran Islands are three tiny islands off the coast of Ireland that supply all their own energy needs from aerogenerators.

Figure .1 Aerogenerators

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However, there are very few suitable sites for tidal power stations. The only working barrage today is on the Rance Estuary in France, but several countries are planning to construct similar systems.

Hydroelectric energy uses the mechanical energy from flowing rivers to generate electricity. It needs fast-flowing water, so hydroelectric power stations are usually sited in mountainous regions and where the current of the river is fast. The current is much lower in the dry season, so most hydroelectric projects include reservoirs and dams to store water. Electricity can then be generated all year round.

4.___________________________________________________________________________________Hydroelectric power is a clean and renewable source of energy, and can be environmentally friendly. For example, there are about 80,000 small-scale hydroelectric turbines in China, which provide electricity to one-third of Chinese towns. However, large-scale hydroelectric projects are usually not environmentally friendly. Dams and reservoirs can destroy the ecological balance of the rivers and surrounding wetlands. Local people, who are a part of this ecosystem, can lose their homes and their livelihood. For example, the Aswan Dam in Egypt was built across Lake Nasser as part of a huge hydroelectric project. The dam caused many unforeseen environmental problems. Most of the lake's natural animal and plant life died. Water-borne diseases such as malaria and schistosomiasis increased. The Nile, which had been a wide, beautiful blue river, became no more than a trickle of water in some places. The land in the Nile Valley has become dry and unproductive. People whose families farmed this land for thousands of years must now leave in search of a more fertile place to live. They are "development refugees."

Solar power is energy generated from the sun. Many electronic devices, such as watches and calculators, can use the sun's energy directly to provide the power they need. Light energy from the sun changes the electrical conducting properties of the silicon crystals, and a tiny electric current starts to flow. 5.__________________________________________________________________________________Most of the solar power that we use today is based on a much simpler principle than the silicon solar cell. Solar panels on the roofs of houses heat water directly for bathing and central heating systems. The industrial version of the solar panel is the solar furnace, in which huge, curved solar panels, together with a system of mirrors, concentrate a large amount of solar energy onto a small area. The heat energy makes steam for generating electricity. Solar power is clean, renewable, non-polluting and does not damage the environment. It is potentially one of the most important sources of energy in the world. A major disadvantage of solar energy is that the amount of energy generated depends on the season, the part of the world and the weather on a particular day. Another disadvantage is that the raw materials for solar panels, such as glass and aluminum, are quite expensive.

Geothermal energy is energy from the hot center of the earth. The earth has a core of molten rock beneath its solid outer crust. This crust is usually between one and 50 kilometers thick.

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The natural world contains many sources of energy. It is possible to convert the energy of the wind, the sea, the rivers, the sun and the hot center of the earth into useful electrical energy. But because alternative energy is a young science, the generators that do this are relatively primitive and inefficient. We need more research into alternative energy. Environmentally-conscious governments must give more funds to research scientists so that they can develop more efficient ways of harnessing natural energy sources.

A. Wave power stations can potentially upset the local ecosystem. They must be carefully planned and sited where they will do little damage to marine and shore life. Tidal energy is harnessed by building a barrage across a river estuary with a large tidal range—that is, a large difference between high tide and low tide. Power is generated either intermittently (when water flowing back out to sea on the ebb tide is used to drive turbines), or continuously (when the energy of the rising tide is also used).

B.The modem version of the windmill is the aerogenerator (Fig. 1), which converts wind energy into electrical energy. The aerogenerator is relatively cheap and quick to build. It would lake about two years to build a wind-powered electricity generating station, compared with 10 years for a power station based on fossil fuels.

C. The problem is how to convert this energy into the type of energy we need most today — electricity. A device that converts one form of energy to another is called a generator. The traditional generator converts heat energy from coal or gas into electrical energy. The-generators of the future will harness renewable forms of energy in a similar way.

D. This system is called a solar cell. Although solar cells used on earth do not provide much power, satellites in space run on the same principle. They get many times more energy because they are closer to the sun. In the future, workers in space may build huge power stations from solar cells many kilometers wide. The electricity generated could be beamed down to earth as microwaves and then converted back into electricity.

E. Some hydroelectric stations pump water back to a high reservoir during the night (when demand for electricity is low). Like wave and tidal power, hydroelectric power has a high capital cost but low running costs. In Norway, which has many suitable mountain rivers, 90 percent of the country's energy comes from hydroelectricity.

F. But in some places (such as Iceland and New Zealand) it is very thin; the hot molten rock is only a few meters beneath the surface. Energy from this molten rock is already widely used to heat homes and swimming pools in New Zealand, and in a few places it is used to generate electricity. If we developed the technology to bore deeper beneath the earth's surface, many other countries could use geothermal energy. Because there is so much molten rock within the earth, the potential supply of geothermal energy is almost limitless.