Renewable energy mix include solar thermal photovoltaic bioenergy hydro tidal wind wave and geothermal energy 16 17. Renewable energy sources for fuels and electricity thomas b johansson henry kelly laurie burnham robert williams amulya k n reddy island press 1993 technology engineering 1160 pages. There are four types of geothermal occurrences hydrothermal sources hot dry rock magma and geopressurized sources the total accessible resource base of geothermal energy to a depth of 5 km is. The united nations conference on new and renewable sources of energy uncnrse assessed the technology and economic validity of 10 sources of new and renewable energy biomass solar fuel wood hydropower wind power tar sands and oil shale ocean thermal geothermal peat and draught animals the purpose was to identify constraints on their use as well as measures to enhance their use and thereby facilitate the energy transition from excessive dependence on fossil fuels to a diversified