There are some criterions to select an energy source. A perfect energy power should be cheap to produce, plentiful, easy, clean and safe to use and infinite. In reality, there are no energy sources which can satisfy all these demands. Oil is easy to use but it pollutes the air and its source is scare. On the contrary, nuclear power is very dangerous for people if there is something wrong with the station. Thousands of people have been affected by radio-activity since the Chenobyl station explored. It is worse that these harmful effects will continue to transmit to younger generation. In addition, the building of a nuclear station requires a big investment and the operation of nuclear power involve hi-tech and strict regulations. Therefore, the nuclear power is only produced in industrialized countries.

Researches are looking to other energy resources to reduce the pressure on energy problems. Solar energy is a very cheap resource since it takes power from sunlight to heal the water or run other small electrical appliances. However, this kind of power can be used only in the coastal regions since the sun is available throughout the year and it is costly to build equipment. Hydro power is another option for countries which have many streams. But the supply of power is unstable and depend on the water level in lakes.

Briefly, each energy resource has both its advantages and disadvantages. Depending on the ranking of criterions, people can choose the most appropriate energy source for their needs.