$1$, For a long time, people have been using water to power machines.

`2`. Solar panels will take the place of the roof a house and sun's energy will be used to heat water.

`3`. We use energy from the sun, the wind and the water.

`4`. Many countries have already been using solar energy

`5`, The earth's fossil fuels are running out

6. We / looking / cheap, clean, effective source / energy / not cause pollution or waste natural resource

We are looking for a cheap, clean, effective source of energy that does not cause pollution or waste natural resource

7. Recently / wind / use / generate electricity

Recently wind has used to generate electricity

8. The sun / supply / all energy / used / grow plants / evaporate water / rain / and / maintain / temperature / planet

The sun supplies all energy used to grow plants and to evaporate water for rain and to maintain tenperature of the planet

9. At present / most / our electricity / come / use / coal, gas, oil or nuclear power

At present, most of our electricity comes from the use of coal, gas, oil or nuclear power

10. Today / water power / mostly / use / generate electricity

Today, water power is mostly used to generate electricity

11. This power / could / provide / sun

This power could be provided by the sun

12. If we / able / collect solar energy / we / be sure / have enough power

If we are able to collect solar energy, we will be sure to have enough power

7. Recently, wind has been used to generate electricity

8. The sun supplies all energy which is used to grow plants, evaporate water for raining and maintain the temperature of the planet

9. At present, most of our electricity comes from the use of coal, gas, oil or nuclear power

10. Today, water power is mostly used to generate electricity

11. This power could be provided by the sun

12. If we are able to collect solar energy, we will be sure to have enough power