Read the texts about alternative power sources and complete the table with the missing information.Alternative power sourcesEnvironmental problems such as the greenhouse effect and air pollution have led scientists to find alternative power sources which are renewable and less polluting.SOLAR ENERGYSunlight can be directly converted into electricity by solar cells made of silicon. When light strikes the cells, a part of it is absorbed by the semiconductor material. The energy of the absorbed light knocks electrons loose, allowing them to flow freely and produce electricity. The process of converting light (photons) into electricity (voltage) is known as the photo-voltaic process (PV). Solar cells are usually combined into panels and grouped into arrays. Even if the initial costs can be high, the PV system provides an independent, reliable electrical power source. It can produce energy for more than 15 years and its routine maintenance is simple and cheap.WIND ENERGYWind energy is one of the cheapest renewable technologies available today. The wind turns the blades of giant turbines, producing in this way kinetic energy which is then converted into mechanical power and electricity by a generator. The main disadvantage of wind energy is that there are few suitable wind sites where it is possible to have a constant production of electricity.TIDAL ENERGYThis alternative power source, which is typically used in coastal areas, turns the potential energy of tides into electricity. Tidal power generators use rising and fallingtides in much the same manner as hydroelectric power plants. Large underwater turbines are placed in areas with high tidal movements and are designed to capture the kinetic energy of rising and falling tides. The turbines are driven by the power of the sea both when the tide comes in and when it goes out. The problem with tidal power is that only massive increases in tides can produce energy and there are very few places where this occurs. Moreover, the aquatic ecosystem and the shoreline can be damaged by the changes in the tidal flow.GEOTHERMALENERGYIn the past, people used hot springs for bathing, cooking and heating. Geothermal energy is based on the fact that the Earth is hotter below the surface. The hot water which is stored in the Earth can be brought to the surface and used to drive turbines to produce electricity or it can be piped through houses as heat. This energy is cheap and has a low impact on the environment, but there are few sites where it can be extracted at low cost.BIOMASS ENERGYBiomass is a renewable energy source deriving from plant material and animal waste. When it is burnt, it releases its chemical energy as heat. Biomass fuels include forest residues (such as dead trees, branches and tree stumps), straw, manure and even municipal solid waste. Biomass energy is a natural process, it is carbon neutral and has low initial costs. It used to be the main source of heating at home in the past and it continues to be highly exploited in the developing world. The main disadvantage of biomass is that it has a smaller potential than other energy sources and requires excellent maintenance skills.1) Type of energy: пустоSolar energy How it works: пустоSolar cells made of silicon absorb sunlight, which knocks electrons loose, allowing them to flow freely and produce electricity. Advantages: пустоThe PV system provides an independent, reliable electrical power source and its routine maintenance is simple and cheap. Disadvantages: high initial costs2) Type of energy: Wind energy How it works: пустоThe wind turns the blades of giant turbines, producing kinetic energy which is then converted into mechanical power and electricity by a generator. Advantages: пустоIt is one of the cheapest renewable technologies available today. Disadvantages: пустоThere are few suitable wind sites. 3) Type of energy: пустоTidal energy How it works: пустоUnderwater turbines capture the kinetic energy of rising and falling tides and turn it into electricity. Advantages: It is a natural process because it exploits the potential energy of tides. Disadvantages: пустоOnly massive increases in tides can produce energy and there are very few places where this occurs. Moreover the changes in the tidal flow can damage the aquatic ecosystem and the shoreline. 4) Type of energy: пустоGeothermal energy How it works: The hot water stored in the Earth is brought to the surface and used to drive turbines to produce electricity or it can be piped through houses as heat. Advantages: пустоIt is cheap and has a low impact on the environment. Disadvantages: пустоThere are few sites where it can be extracted at low cost. 5) Type of energy: пустоBiomass energy How it works: пустоPlant material and animal waste are burnt in order to release chemical energy as heat. Advantages: пустоIt is a natural process, is carbon neutral and has low initial costs. Disadvantages: пустоIt has a smaller potential than other energy sources and requires excellent maintenance skills.