<P> Wave power, which captures the energy of ocean surface waves, and tidal power, converting the energy of tides, are two forms of hydropower with future potential; however, they are not yet widely employed commercially . A demonstration project operated by the Ocean Renewable Power Company on the coast of Maine, and connected to the grid, harnesses tidal power from the Bay of Fundy, location of world's highest tidal flow . Ocean thermal energy conversion, which uses the temperature difference between cooler deep and warmer surface waters, has currently no economic feasibility . </P> <P> Solar energy, radiant light and heat from the sun, is harnessed using a range of ever - evolving technologies such as solar heating, photovoltaics, concentrated solar power (CSP), concentrator photovoltaics (CPV), solar architecture and artificial photosynthesis . Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy . Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air . Active solar technologies encompass solar thermal energy, using solar collectors for heating, and solar power, converting sunlight into electricity either directly using photovoltaics (PV), or indirectly using concentrated solar power (CSP). </P> <P> A photovoltaic system converts light into electrical direct current (DC) by taking advantage of the photoelectric effect . Solar PV has turned into a multi-billion, fast - growing industry, continues to improve its cost - effectiveness, and has the most potential of any renewable technologies together with CSP . Concentrated solar power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam . Commercial concentrated solar power plants were first developed in the 1980s . CSP - Stirling has by far the highest efficiency among all solar energy technologies . </P> <P> In 2011, the International Energy Agency said that "the development of affordable, inexhaustible and clean solar energy technologies will have huge longer - term benefits . It will increase countries' energy security through reliance on an indigenous, inexhaustible and mostly import - independent resource, enhance sustainability, reduce pollution, lower the costs of mitigating climate change, and keep fossil fuel prices lower than otherwise . These advantages are global . Hence the additional costs of the incentives for early deployment should be considered learning investments; they must be wisely spent and need to be widely shared". Italy has the largest proportion of solar electricity in the world, in 2015 solar supplied 7.8% of electricity demand in Italy . In 2016, after another year of rapid growth, solar generated 1.3% of global power . </P>

Where does most renewable energy we use come from