There are several. Everything cannot be used at Home. But knowledge of them is a must.  You can use them in other walks of life including the work place. Why! you can start a business on generating power out of Renewable Sources of energy.

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We have two perennial and wonderful sources of energy. The first, of course the one we see every day; the Sun. While the first one is above us in the sky, the second one is beneath us, hidden in the hot rocks of the earth. The second one is called Geothermal Energy.  Most tribals still use this to cook their food and take a hot water bath free of cost.

 

4. Fuel Cells
What are fuel cells? Fuel cells are electrochemical devices that convert the chemical energy of a fuel directly and very efficiently into electricity (DC) and heat, thus doing away with combustion. The most suitable fuel for such cells is hydrogen or a mixture of compounds containing hydrogen. A fuel cell consists of an electrolyte sandwiched between two electrodes. Oxygen passes over one electrode and hydrogen over the other, and they react electrochemically to generate electricity, water, and heat.

Though fuel cells have been used in space flights and combined supplies of heat and power, electric vehicles are the best option available to dramatically reduce urban air pollution. Compared to vehicles powered by the internal combustion engine, fuel-cell powered vehicles have very high energy conversion efficiency, (almost double that of currently used engines) and near-zero pollution, CO2 and water vapour being the only emissions. Fuel-cell-powered EV's (electric vehicles) score over battery operated EV's in terms of increased efficiency and easier and faster re-fuelling.

5. Hydel energy
Energy from water sources
The energy in the flowing water can be used to produce electricity. Waves result from the interaction of the wind with the surface of the sea and represent a transfer of energy from the wind to the sea. Energy can be extracted from tides by creating a reservoir or basin behind a barrage and then passing tidal waters through turbines in the barrage to generate electricity.

Mini or Micro Hydro power
Hydro power is one of the best, cheapest, and cleanest sources of energy. Although with big dams, there are many environmental and social problems as has been seen in the case of the Tehri and the Narmada Projects. Small dams are, however, free from these problems. This is in fact one of the earliest known renewable energy sources, in the country (since the beginning of the 20th century).

New environmental laws affected by the danger of global warming have made energy from small hydropower plants more relevant. These small hydropower plants can serve the energy needs of remote rural areas independently. The real challenge in a remote area lies in successful marketing of the energy and recovering the dues. Local industries should be encouraged to use this electricity for sustainable development.

It is a technology with enormous potential, which could exploit the water resources to supply energy to remote rural areas with little access to conventional energy sources. It also eliminates most of the negative environmental effects associated with large hydro projects.

Energy from the sea - Ocean thermal, tidal and wave energy
A large amount of solar energy is stored in the oceans and seas. On an average, the 60 million square kilometers of the tropical seas absorb solar radiation equivalent to the heat content of 245 billion barrels of oil. Scientists feel that if this energy can be tapped a large source of energy will be available to the tropical countries and to other countries as well. The process of harnessing this energy is called OTEC (Ocean Thermal Energy Conversion). It uses the temperature differences between the surface of the ocean and the depths of about 1000m to operate a heat engine, which produces electric power.

Energy is also obtained from waves and tides. The first wave energy project with a capacity of 150MW, has been set up at Vizhinjam near Trivandrum. A major tidal wave power project costing of Rs.5000 crores, is proposed to be set up in the Hanthal Creek in the Gulf of Kutch in Gujarat. In some countries such as Japan small scale power generators run by energy from waves or the ocean, have been used as power sources for channel marking buoys.

 

6. Co-generation
Co-generation is the concept of producing two forms of energy from one fuel. One of the forms of energy must always be heat and the other may be electricity or mechanical energy. In a conventional power plant, fuel is burnt in a boiler to generate high-pressure steam. This steam is used to drive a turbine, which in turn drives an alternator through a steam turbine to produce electric power. The exhaust steam is generally condensed to water which goes back to the boiler.

As the low-pressure steam has a large quantum of heat which is lost in the process of condensing, the efficiency of conventional power plants is only around 35%. In a co-generation plant, very high efficiency levels, in the range of 75%–90% can be reached. This is so, because the low-pressure exhaust steam coming out of the turbine is not condensed, but used for heating purposes in factories or houses. Since co-generation can meet both power and heat needs, it has other advantages as well in the form of significant cost savings for the plant and reduction in emissions of pollutants due to reduced fuel consumption.

Even at conservative estimates, the potential of power generation from co-generation in India is more than 20,000 MW. Since India is the largest producer of sugar in the world, bagasse-based co-generation is being promoted. The potential for co-generation thus lies in facilities with joint requirement of heat and electricity, primarily sugar and rice mills, distilleries, petrochemical sector and industries such as fertilizers, steel, chemical, cement, pulp and paper, and aluminum

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7. Wind energy
Wind energy is the kinetic energy associated with the movement of atmospheric air. It has been used for hundreds of years for sailing, grinding grain, and for irrigation. Wind energy systems convert this kinetic energy to more useful forms of power. Wind energy systems for irrigation and milling have been in use since ancient times and since the beginning of the 20th century it is being used to generate electric power. Windmills for water pumping have been installed in many countries particularly in the rural areas.

Wind turbines transform the energy in the wind into mechanical power, which can then be used directly for grinding or further converting to electric power to generate electricity. Wind turbines can be used singly or in clusters called ‘wind farms’. Small wind turbines called aero-generators can be used to charge large batteries.