Status of geothermal energy amongst the worldʹs energy source

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, 5–13US¢/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. # 2003CNR. Published by Elsevier Ltd. All rights reserved.