Geothermal energy for the benefit of the people

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Abstract

Geothermal energy for electricity generation has been produced commercially since 1913, and for four decades on the scale of hundreds of MW both for electricity generation and direct use. The utilization has increased rapidly during the last three decades. In 2000, geothermal resources have been identified in over 80 countries and there are quantified records of geothermal utilization in 58 countries in the world. The worldwide use of geothermal energy amounts to 49 TWh/a of electricity and 53 TWh/a for direct use. Electricity is produced with geothermal steam in 21 countries spread over all continents. Five countries obtain 10–22% of their electricity from geothermal energy. Only a small fraction of the geothermal potential has been developed so far, and there is ample space for an accelerated use of geothermal energy both for electricity generation and direct applications. A comparison of the renewable energy sources (data from the UN World Energy Assessment Report) shows the current electrical energy cost to be 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. 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%. Comparing four “new” renewable energy sources (geothermal, wind, solar and tidal), shows 70% of the electricity generated by the four to come from geothermal with only 42% of the total installed capacity. Wind energy contributes 27% of the electricity, but has 52% of the installed capacity. Solar energy produces 2% of the electricity and tidal energy 1%. 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. The current cost of direct heat from biomass is 1–5 US¢/kWh, geothermal 0.5–5 US¢/kWh, and solar heating 3–20 US¢/kWh. Geothermal energy, with its proven technology and abundant resources, can make a significant contribution towards reducing the emission of greenhouse gases.

Introduction

At the turn of the millennium, two billion people, a third of the world's population, have no access to modern energy services. World population is expected to double by the end of the 21st century. A key issue to improve the standard of living of the poor is to make clean energy available to them at prices they can afford. Energy affects all aspects of modern life [1]. There is a strong positive correlation between energy use per capita in a country and issues that we value highly such as productivity per capita in the country and life expectancy.

The World Energy Council has presented several scenarios for meeting the future energy requirements with varying emphasis on economic growth, technological progress, environmental protection and international equity. During 1990–2050, the primary energy consumption is expected to increase by 50% according to the most environmentally conscious scenario and by 275% according to the highest growth rate scenario. In the environmental scenario, carbon emissions are expected to decrease slightly from 1990 levels, whereas the high growth-rate scenario leads to a doubling of carbon emissions [2]. The scarcity of energy resources forecasted in the 1970s has not occurred so far. Economic development in the new century will not be constrained by geological resources. Environmental concerns, financing, and technological constrains appear more likely sources of future limits [3].

In all scenarios, the peak of the fossil fuel era has already passed. Oil and gas are expected to continue to be important sources of energy [2]. The share of renewable energy sources is expected to increase very significantly (to 30–80% in 2100). Hydropower and traditional biomass are already important factors in the world's energy mix, contributing about 18% of the total world energy requirements, whereas the “new” renewables contribute only about 2% of the present world primary energy use. The potentially largest single contributor of the “new” renewables, namely solar energy for electricity production, is still not commercially competitive with conventional energy sources. “Modern” biomass, wind and geothermal energy are commercially competitive and are making relatively fast progress.

It is clear that no single energy source is going to take over from the polluting fossil fuels in the new century. The integration of local energy sources in individual countries and regions into national/regional systems that make use of the best local and imported energy is important if we are to find solutions to regional and global energy problems. Proponents for the renewable energy sources need to work together in the world energy market which is very conservative.

The present paper describes the status of geothermal energy development in the world. It furthermore compares the status of the renewable energy resources, namely hydropower, biomass, geothermal, wind, solar and tidal energy. The comparison is mainly based on data presented in the recently published World Energy Assessment report [4], prepared by UNDP, UN–DESA and the World Energy Council.

Section snippets

Hot springs used through the centuries

People have used hot springs for bathing and washing of clothes since the dawn of civilization in many parts of the world. Vestiges of Japanese culture have been unearthed near the Yuda hot spring (Iwate Prefecture) dating from the pre-pottery period before 11,000 B.C. [5], and at the Kawazu hot spring (Nagasaki Prefecture), dating from the Jomon period (11,000–300 B.C.). There are written records of geothermal usage in China which are over two thousand years old. Public baths became common at

Present use and potential of geothermal

It was in the 20th century that geothermal energy was first harnessed on a large scale for space heating, industry, and electricity generation. Prince Piero Ginori Conti initiated electric power generation with geothermal steam at Larderello, Tuscany, in 1904. The first large scale municipal district heating service started in Iceland in 1930. Geothermal energy has been produced commercially for over 80 years, and for four decades on the scale of hundreds of MW both for electricity generation

Electricity production

Electricity is produced with geothermal steam in 21 countries spread over all continents (Table 1). The top ten countries in 1999 were (MWe in brackets): USA (2228), Philippines (1909), Italy (785), Mexico (755), Indonesia (590), Japan (547), New Zealand (437), Iceland (170), El Salvador (161), and Costa Rica (143). The most progressive country at present, the Philippines, plans to add 526 MWe to the installed capacity during 2002–2008. About 22% of the electricity in the Philippines is

Direct use of geothermal energy

Direct application of geothermal energy can involve a wide variety of end uses, such as space heating and cooling, industry, greenhouses, fish farming, and health spas. It uses mostly existing technology and straight forward engineering. The technology, reliability, economics, and environmental acceptability of direct use of geothermal energy has been demonstrated throughout the world. The main types of direct use [10] are bathing/swimming/balneology (42%), space heating (35%, thereof 12% with

Heat pump applications

Geothermal energy has until recently had a considerable economic potential only in areas where thermal water or steam is found concentrated at depths less than 3 km in restricted volumes, analogous to oil in commercial oil reservoirs. This has recently changed with developments in the application of ground source heat pumps using the earth as a heat source for heating or as a heat sink for cooling, depending on the season. This has made it possible for all countries to use the heat of the earth

Geothermal energy for the benefit of the people

People in at least 64 countries around the world are enjoying the use of geothermal resources in variable forms. The scale of use is, however, very variable. The country with the most extensive use of geothermal energy is Iceland which obtains 50% of its total primary energy use from geothermal energy, the remainder coming from hydropower 18%, oil 30% and coal 2%. About 68% of the primary energy of Iceland is thus produced by renewable energy sources. The average figure for the countries of the

Environmental issues

Geothermal fluids contain a variable quantity of gas, largely nitrogen and carbon dioxide with some hydrogen sulfide and smaller proportions of ammonia, mercury, radon and boron. The amounts depend on the geological conditions of different fields. Most of the chemicals are concentrated in the disposal water which is routinely reinjected into drillholes and thus not released into the environment. The concentrations of the gases are usually not harmful, and the removal of e.g. hydrogen sulfide

Comparison of geothermal energy with other renewables

The World Energy Assessment report, prepared by UNDP, UN–DESA and the World Energy Council, has recently been published. It gives a very valuable and comprehensive description of the status of the world's energy sources at the turn of the millennium. The report is published as an input to the session on “energy and sustainable development” of the United Nations Commission on Sustainable Development that will take place in April 2001. Chapter 7 of this voluminous report deals with the renewable

Discussion

Geothermal energy has been produced commercially for 80 years, and on the scale of hundreds of MW for four decades, both for electricity generation and direct use. The utilization has increased rapidly during the last three decades. In 2000, there are records of geothermal utilization in 58 countries in the world. The electricity generated is about 49 TWh/a, and the direct use amounts to about 53 TWh/a.

Based on the country reports at the World Geothermal Congress 2000, Huttrer [9] expects the

Acknowledgements

The author would like to thank Valgardur Stefansson of Orkustofnun, the National Energy Authority of Iceland, for reviewing the manuscript and many helpful comments.

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