Abstract
The world primary energy consumption is about 400 EJ/year, mostly provided by fossil fuels (80\%). The renewables collectively provide 14\% of the primary energy, in the form of traditional biomass (10\%), large (>10 MW) hydropower stations (2\%), and the "new renewables" (2\%). Nuclear energy provides 6\%.
The World Energy Council expects the world primary energy consumption to have grown by 50-275\% in 2050, depending on different scenarios. The renewable energy sources are expected to provide 20-40\% of the primary energy in 2050 and 30-80\% in 2100. The technical potential of the renewables is estimated at 7600 EJ/year, and thus certainly sufficiently large to meet future world energy requirements.
Of the total electricity production from renewables of 2826 TWh in 1998, 92\% came from hydropower, 5.5\% from biomass, 1.6\% from geothermal and 0.6\% from wind. Solar electricity contributed 0.05\% and tidal 0.02\%.
The electricity cost is 2-10 US¢/kWh for geothermal and hydro, 5-13 US¢/kWh for wind, 5-15 US¢/kWh for biomass, 25-125 US¢/kWh for solar photovoltaic and 12-18 US¢/kWh for solar thermal electricity.
Biomass constitutes 93\% of the total direct heat production from renewables, geothermal 5\%, and solar heating 2\%.
Heat production from renewables is commercially competitive with conventional energy sources. Direct heat from biomass costs 1-5 US¢/kWh, geothermal 0.5-5 US¢/kWh, and solar heating 3-20 US¢/kWh.
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