The Australian Renewable Energy Agency defines renewable energy as that which is produced using natural resources that are constantly replaced and never run out. Just as there are many natural sources of energy, so too are there many renewable energy technologies that produce heat or electricity. These include solar, wind, hydropower, geothermal, bioenergy and ocean energy. Renewable energy production is complemented by storage technologies that enable production by day and night, such as batteries and smart technologies that predict when and where electricity will be required.