With increase in pollution and cost of producing electricity going up, many scientist have been working on alternate source pf energy. The major source  which have been utilized in recent years are :

Wind energy - Wind mills have been designed to make use of blowing winds and generate electricity through alternators or use the rotation directly to grind or pump water from well. This is the cheapest form of energy, wind mill has very few parts is noise less  and requires little maintenance. Though the electricity generation is seasonal.

Geo thermal - many places on the earth give out steam, This stem has been harnessed to produce electricity by running turbines. Since these areas have been producing steam for possibly few thousand years and may continue for few more centuries this energy is going waste is non polluting.  

Sea waves are also being used to operate turbine and generate electricity. This energy is also non polluting, free and is available for life long exploitation.

Biomass - Bio waste has been used as fuel to burn and run turbine through production of steam.

Natural gas- Technology has been developed to utilize the compressed natural gas to run internal combustion engine. This is  supposed to be less polluting. Cost involved is in transporting and compressing and filling in automobiles.

Hydrogen Some success has been achieved in Hydrogen as fuel for internal combustion engine. Hydrogen fuel is recyclable non polluting and if the right technology can be developed has great promise for the future.

Sun light -  has been harness either to heat water or convert to electricity using photovoltaic cell. Sun energy is free and non polluting. Due to low efficiency of  photoelectric cell and cost. sun though provide abundant energy, and plants have evolved to use sun light efficiently, the science has lagged behind in finding effective and economical methods to harness the same.

Interestingly electricity has been generate from water flowing in capillary tube. Laser light energy has been used to change the orbit of a satellite, power for Laser engine was provided by photovoltaic cells. This arrangement can provide free power for  many years to control the satellite.