Renewable energy technology are essential contribute to sustainable energy as they contribute to world energy security by reducing dependence on fossil fuel resources and providing opportunities for mitigating green house gases . the three generation of renewable technologies, reaching back more than 100 years are
- first generation technologies includes hydro power , biomass combustion and geothermal power and heat
- Second generation technology includes solar heating and cooling , wind power, modern forms of bio energy and solar photovoltaic
- Third generation technology includes advanced biomass gasification , enhanced geothermal system and marine energy
first and second generation technology have entered the markets, third generation technology are not yet commercialized . they may have potential comparable to other renewable energy technologies.