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 USc/kWh for geothermal and hydro, 5-13 UScent/kWh for wind, 5-15 UScent/kWh for biomass, 25-125 UScent/kWh for solar photovoltaic and 12-18 UScent/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 UScent/kWh, geothermal 0.5-5 USc/kWh, and solar heating 3-20 USc/kWh. (C) 2003 CNR. Published by Elsevier Ltd. All rights reserved.
