of electricity. Tidal Energy: Tidal energy is a form of water energy, hydro-energy, which falls in the category of ocean energy.  As the name implies it is a form of energy that converts the energy of tides into useful electric energy. Despite of the fact that tidal energy is more predictable than wind the production of electricity from tidal power has higher cost than other renewable green energy sources due to the cost of technology used and due to the limited locations with high tidal power. With extensive R&D in this sector, there have been significant improvements in the both the turbines technology and the design of the whole setup and this gives promises that the costs will be reduced and that tidal energy will be in the future a cost effective renewable green energy source. Hydroelectric Energy: This is the most common and the most widely used form of renewable green energy sources. Hydroelectric energy has a lower cost than any other form of renewable sources and in some cases over conventional forms of energy and this gives a clear benefit to the consumer since it is free of C0 2 emissions. Hydroelectric energy projects have a longer lifespan and this along with low maintenance and operational costs makes hydroelectric energy production an option of choice where the conditions and environment permit. Hydroelectric energy accounts for about 5% of the total world energy produced and about 60% of the whole the renewable green energy production. Depending on the location,