<Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> Sustainable energy is energy that is consumed at insignificant rates compared to its supply and with manageable collateral effects, especially environmental effects . Another common definition of sustainable energy is an energy system that serves the needs of the present without compromising the ability of future generations to meet their needs . The organizing principle for sustainability is sustainable development, which includes the four interconnected domains: ecology, economics, politics and culture . Sustainability science is the study of sustainable development and environmental science . </P> <P> Technologies promote sustainable energy including renewable energy sources, such as hydroelectricity, solar energy, wind energy, wave power, geothermal energy, bioenergy, tidal power and also technologies designed to improve energy efficiency . Costs have decreased immensely through out the years, and continue to fall . Increasingly, effective government policies support investor confidence and these markets are expanding . Considerable progress is being made in the energy transition from fossil fuels to ecologically sustainable systems, to the point where many studies support 100% renewable energy . </P> <P> Energy efficiency and renewable energy are said to be the twin pillars of sustainable energy . In the broader context of sustainable development, there are three pillars, ecology, economy and society . Some ways in which sustainable energy has been defined are: </P>

Name the main source of energy in any self sustaining system
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