tham khảo:
Sun water and wind are alternative sources of energy．Wind rotating the windmill and moving the sail ．It’s a clean source and a lot of energy ．Unfortunately， if the wind does not blow ．there is no wind energy．As water moves from one place to another ， it makes energy．However， people have to build dams to use this energy source．The dams cost a lot of money ， so water is expensive too.The sun releases large amounts of energy each day．This energy can be converted into electricity . Solar energy is not only abundant and infinite but also clean and safe.Desfite some drawbacks ， the potention of onternative energy sources is enormous ．However ， how to make full use of the energy resources is a question for researchers all over the world.