<P> Other renewable energy technologies are still under development, and include cellulosic ethanol, hot - dry - rock geothermal power, and marine energy . These technologies are not yet widely demonstrated or have limited commercialization . Many are on the horizon and may have potential comparable to other renewable energy technologies, but still depend on attracting sufficient attention and research, development and demonstration (RD&D) funding . </P> <P> There are numerous organizations within the academic, federal, and commercial sectors conducting large scale advanced research in the field of renewable energy . This research spans several areas of focus across the renewable energy spectrum . Most of the research is targeted at improving efficiency and increasing overall energy yields . Multiple federally supported research organizations have focused on renewable energy in recent years . Two of the most prominent of these labs are Sandia National Laboratories and the National Renewable Energy Laboratory (NREL), both of which are funded by the United States Department of Energy and supported by various corporate partners . Sandia has a total budget of $2.4 billion while NREL has a budget of $375 million . </P> <Ul> <Li> Enhanced geothermal system </Li> </Ul> <Li> Enhanced geothermal system </Li>

Find any two conventional sources of energy (fuels) which of their combination gives energy