Geothermal electric power in Iceland: Development in perspective

Geothermal energy is extensively used in thermal (direct) applications in Iceland. More than 70% of the total population enjoy geothermal district heating. Hydro-power provides most of the electricity generated in Iceland, with less than 10% of the potential harnessed. Iceland is well endowed with both geothermal (high- and low-temperature) and hydro-power resources. At the end of 1980, the installed geothermal power in Iceland was 818 MW₁ in direct applications and 41 MW_e in electric power generation. This exploitation represents a few percent of the estimated geothermal resources of Iceland. Plans to develop geothermal electric power in Iceland date back to the early 1960s. The first geothermal electric power plant (3 MW_e) was installed in 1969. In recent years, several small-scale (two 1 MW_e and one 6 MW_e) geothermal power units have been installed in a cogeneration plant for district heating purposes. There is one major (30 MW_e) geothermal electric power plant in Iceland, which became operational in 1978. Hydro-power, geothermal energy and oil provide consumers in Iceland with about 18, 38, and 44% of their energy needs, respectively.     

Utilisation of geothermal energy in Iceland

The present and future uses of geothermal energy in Iceland are reviewed. The classification of geothermal areas is mentioned and their potential estimated. High temperature areas may be able to sustain the production of 20 MW/km² of electricity for at least 50 years. The potential of the 17 high temperature areas is almost 6000 MW, which is substantially greater than that of the 250 low temperature areas. However, practically all the hot water used for district heating and greenhouse farming is supplied by low temperature areas. About half the population of Iceland enjoys geothermal district heating at the cost of 35% that of comparable fuel oil heating. Utilisation of high temperature areas is relatively recent. Saturated steam from these areas is used for industrial purpose and a 60 MW geothermal power plant is being constructed.     

The elements of direct uses

Direct uses of geothermal energy are important in many countries of the world. Well-known examples are district heating (hitaveita) in Iceland, industrial processing in New Zealand, greenhouse heating in Hungary, and traditional bathing uses in Japan. Although direct uses are also called non-electrical applications, they span the whole range of geothermal temperatures, as evident from the Lindal Diagram shown in Fig. 1. A recent paper on direct uses is that of Gudmundsson and Lund (1985). Because of the many possible applications of geothermal energy, there is a need to identify the main elements that make up direct use projects. The purpose of this paper is to consider these elements, in an attempt to better organize the field of geothermal engineering. The paper concerns the technologies needed to bring geothermal fluids from resource to user. However, corrosion and water quality matters are not discussed, neither are environmental issues. Geothermal drilling, production and reservoir engineering are also outside the scope of this paper.     

Geothermal energy in Turkey: the sustainable future

Turkey is an energy importing nation with more than half of our energy requirements met by imported fuels. Air pollution is becoming a significant environmental concern in the country. In this regard, geothermal energy and other renewable energy sources are becoming attractive solution for clean and sustainable energy future for Turkey. Turkey is the seventh richest country in the world in geothermal energy potential. The main uses of geothermal energy are space heating and domestic hot water supply, greenhouse heating, industrial processes, heat pumps and electricity generation. The district heating system applications started with large-scale, city-based geothermal district heating systems in Turkey, whereas the geothermal district heating centre and distribution networks have been designed according to the geothermal district heating system (GDHS) parameters. This constitutes an important advantage of GDHS investments in the country in terms of the technical and economical aspects. In Turkey, approximately 61,000 residences are currently heated by geothermal fluids. A total of 665 MW_t is utilized for space heating of residential, public and private property, and 565,000 m² of greenhouses. The proven geothermal heat capacity, according to data from existing geothermal wells and natural discharges, is 3132 MWt. Present applications have shown that geothermal energy is clean and much cheaper compared to the other fossil and renewable energy sources for Turkey.     

Low enthalpy geothermal energy utilisation schemes for greenhouse and district heating at Traianoupolis Evros, Greece

A socio-economic study has been made of the possible use of low enthalpy geothermal resources for district and greenhouse heating in the Traianoupolis Evros region. The thermal energy potential of the Aristino-Traianoupolis geothermal field has been estimated at 10.8 MW_th (discharge temperature of 25 °C). Geothermal wellhead water temperatures range from 53 to 92 °C, from 300 m deep wells yielding over 250 m³/h. Our conclusions show, amongst the different scenarios examined and on the basis of a market study, that utilisation of this geothermal energy capacity for district heating of nearby villages, and/or greenhouse heating directed at serving local vegetable markets, would be an attractive investment.     

Geothermal applications in Turkey

Geothermal energy is mostly utilised in direct applications in Turkey. The equivalent of 61,000 residences are currently heated by geothermal fluids. A total of 665 MW_t is utilised for space heating of residential, public and private property, and 565,000 m² of greenhouses. Geothermal fluids are also used in 195 spas (327 MW_t), bringing the total direct use capacity to 992 MW_t. ORME Geothermal Inc. has completed the engineering design of a geothermal district heating system that serves the equivalent of nearly 300,000 residences. A total of 170 geothermal fields have been explored so far in Turkey. At Kizildere a single-flash power plant with 20.4 MW_e installed capacity is integrated with a factory producing liquid CO₂ and dry-ice. A binary cycle power plant with an installed capacity of 25 MW_e will be constructed shortly at Aydin/Germencik. The proven geothermal heat capacity, according to data from existing geothermal wells and natural discharges, is 3132 MW_t (I. Akkus, MTA General Directorate, oral communication, January 2003).     

Direct uses of earth heat

Potential resources and applications of earth heat in the form of geothermal energy are large. World-wide direct uses amount to 7072 MW thermal above a reference temperature of 35°C. District heating is the major direct use of geothermal energy. Equipment employed in direct use projects is of standard manufacture and includes downhole and circulation pumps, transmission and distribution pipelines, heat exchangers and convectors, heat pumps and chillers. Direct uses of earth heat discussed are district heating and cooling, greenhouse heating and fish farming, process and industrial applications, combined and cascading uses. The economic feasibility of direct use projects is governed by site specific factors such as location of user and resource, resource quality, system load factor and load density, as well as financing. Examples are presented of district heating in Reykjavík, Klamath Falls, Melun l'Amont and Svartsengi. Further developments of direct uses of geothermal energy will depend on matching user needs to the resource, and improving load factors and load density.     

The geothermal industry in Iceland

Direct (non-electrical) uses of geothermal energy in Iceland in 1984 amounted to 5517 GWh and the installed power was 889 MW_t, assuming 35°C discharge temperature. The bulk of this thermal power was for district heating, called hitaveita in Icelandic. In recent years this utilization has increased moderately. The installed geothermal electric power is currently 41 MW_e and is unlikely to change in the near future. Icelandic personnel have participated in many geothermal projects of the United Nations during the last 35 years. Contract work has been carried out by Icelandic consulting firms in several developing countries.     

Low-temperature geothermal utilization in Iceland – Decades of experience

Geothermal energy plays a key role in the economy of Iceland and it supplies about 89% of the space heating requirements. A large fraction of the country's district heating services (hitaveitas) use energy from low-temperature geothermal systems, which are mostly located outside the volcanic zone. Many of the geothermal district heating services have been in operation for several decades and much can be learned from their operation, in particular regarding long-term management of low-temperature geothermal resources. In most cases down-hole pumps are used, but there are examples of large-scale artesian flow still being maintained. The Reykjavík geothermal district heating service is the world's largest such service. It started operation on a small scale in 1930, and today it serves Reykjavík and surrounding communities, about 58% of the total population of Iceland. The Reykjavík district heating service utilizes three low-temperature systems. The production and response (pressure, chemistry, and temperature) histories of these systems and six other low-temperature geothermal systems are discussed. Four of the systems are very productive and reach equilibrium at constant production. Two are much less productive and do not attain equilibrium, while three are of intermediate productivity. Groundwater inflow has caused temperature decline and chemical changes in two of the systems. Several problems have faced the Icelandic low-temperature operations, such as excessive pressure drawdown caused by overexploitation, colder water inflow, and sea water incursion. None of the district heating systems has ceased operation and solutions have been found to these problems. The solutions include improving the energy efficiency of the associated heating systems, deeper and more focussed drilling (e.g., directional drilling), finding new drilling targets (even new drilling areas), and injection, as well as technical solutions on the surface. The long utilization case histories provide important information pertaining to sustainable management of geothermal resources.     

Direct heat utilization of geothermal resources

Direct utilization of geothermal energy consists of various forms for heating and cooling instead of converting the energy for electric power generation. The major areas of direct utilization are (1) swimming, bathing and balneology, (2) space heating and cooling including district heating, (3) agriculture applications, (4) aquaculture applications, (5) industrial processes, and (6) heat pumps. Major direct utilization projects exploiting geothermal energy exist in about 38 countries, and the estimated installed thermal power is almost 9,000 MWt utilizing 37,000 kg/s of fluid. The world-wide thermal energy used is estimated to be at least 108,100 TJ/yr (30,000 GWh/yr) - saving 3.65 million TOE/yr. The majority of this energy use is for space heating (33%), and swimming and bathing (19%). In the USA the installed thermal power is 1874 MWt, and the annual energy use is 13,890 TJ (3,860 GWh). The majority of the use (59 %) is for heat pumps (both ground coupled and water source), with space heating, bathing and swimming, and fish and animal farming each supplying about 10%.     

U.S.A. experience in direct heat use

Direct heat use of geothermal energy in the U.S.A. occurs mainly in the western states. A total of 216 projects is operational, with six under construction and 21 planned. The operational projects account for about 2100 TJ/yr (233 MWt-peak) with an average load factor of 29%. The under-construction and planned projects would approximately double the energy use. Not included are an estimated 10,000 TJ (400 MWt-peak) used in enhanced oil recovery. Space and district heating account for almost half (45.8%) of the annual use, whereas greenhouses account for 20.2%, fish farming for 20.7%, industrial processing for 6.7%, and pools and spas for 6.6%. Future growth is expected to be greatest in district heating, where eight proposed projects will produce 1360 TJ annually (149 MWt-peak). Future growth of all direct heat uses in the U.S. is estimated at 8% annually.     

The USA geothermal country update

Geothermal energy is used for electric power generation and direct utilization in the United States. The present installed capacity (gross) for electric power generation is about 2020 MWe, with 1902 MWe net delivering power to the grid, producing approximately 16,000 GWh per year for a 96% capacity factor. Geothermal electric power plants are located in California, Nevada, Utah and Hawaii. The two largest concentrations of plants are at The Geysers in northern California and the Imperial Valley in southern California. The latest development at The Geysers, due to recent declines in steam output, is the injection of recycled wastewater from two communities into the reservoir, which has at present permitted the recovery of 70 MWe of power generation. The direct utilization of geothermal energy includes the heating of pools and spas, greenhouses and aquaculture facilities, space heating and district heating, snow melting, agricultural drying, industrial applications and ground-source heat pumps. The installed capacity is about 4350 MWt and the annual energy use is 22,250 TJ, or 6181 GWh. The largest application is that of ground-source (geothermal) heat pumps (60% of the energy use), and the largest direct-use is that of aquaculture pond and raceway water heating. Direct utilization is increasing at about 6% per year, whereas electric power plant development is almost static. The energy savings from electric power generation, direct uses and ground-source heat pumps amount to 6.6 million tonnes of equivalent fuel oil per year and represents a reduction in air pollution of 5.8 million tonnes of carbon annually (compared to fuel oil).     

Utilization of geothermal energy in Russia

At present geothermal energy is utilized in Russia mostly for space and district heating, and for industrial and agricultural purposes. Six towns whith a total population of about 100,000 use geothermal district heating systems. The total area of geothermally heated greenhouses is about 700,000 m². Electric energy generated at geothermal power stations remains negligible: the installed capacity of the only operating Pauzhetskaya station (Kamchatka) is 11 MW_e. Another station at the Mutnovsky geothermal field is currently under construction and is expected to have 70 MW_e, installed by 1995 and 210 MW_e, by 2000. The proven geothermal resources in Russia provide hope for a significant increase in the utilization of the earth's deep heat and a significant contribution to the power budget in the near future.     

Development of geothermal energy utilization in Turkey: a review

Renewable energy is accepted as a key source for the future, not only for Turkey but also for the world. Turkey has a considerably high level of renewable energy sources that can be a part of the total energy network in the country. Turkey is located in the Mediterranean sector of Alpine–Himalayan Tectonic Belt and has a place among the first seven countries in the world in the abundance of geothermal resources. The share of its potential used is, however, only about 2–3%.The main objective of the present study is to review the development of geothermal energy (GE) utilization in Turkey, giving its historical development and opportunities. GE is used for electric power generation and direct utilization in Turkey, which is among the first five countries in the world in geothermal direct use applications. Direct use of geothermal resources has expanded rapidly last 36 years from space heating of single buildings to district heating, greenhouse heating, industrial usage, modern balneology and physical treatment facilities.Turkey presently has one operating geothermal power plant, located near Denizli City in Western Anatolia with an installed capacity of 20.4 MW_e and an electrical energy production of 89,597 MW h in 2001. Recently, the total installed capacity has reached 820 MW_t for direct use. The total area of geothermal heated greenhouses exceeded over 35 ha with a total heating capacity of 81 MW_t. Ground-source (or geothermal) heat pumps (GSHPs) have also been put on the Turkish market since 1998. Though there are no Turkish GSHP manufactures as yet, 207 units have been installed in the country to date, representing a total capacity of 3 MW.GE is a relatively benign energy source, displaying fossil fuels and thus reducing greenhouse gas emissions. So, it is expected that GE development will significantly speed up in the country if the geothermal law becomes effective.     

Geothermal development in Hungary—country update report 2000–2002

This paper describes the status of geothermal energy utilization—direct use—in Hungary, with emphasis on developments between 2000 and 2002. The level of utilization of geothermal energy in the world increased in this period and geothermal energy was the leading producer, with 70% of the total electricity production, of all the renewable energy sources (wind, solar, geothermal and tidal), followed by wind energy at 28%. The current cost of direct heat use from biomass is 1–5 US¢/kWh, geothermal 0.5–5 US¢/kWh and solar heating 3–20 US¢/kWh. The data relative to direct use in Hungary decreased in this period and the contribution of geothermal energy to the energy balance of Hungary, despite significant proven reserves (with reinjection) of 380 million m³/year, with a heat content of 63.5 PJ/a at ΔT=40 °C, remained very low (0.25%). Despite the fact that geothermal fluids with temperatures at the surface higher than 100 °C are available, no electricity has been generated. As of 31 December 2002, the geothermal capacity utilised in direct applications in Hungary is estimated to be 324.5 MW_t and to produce 2804 TJ/year. Geothermal heat pumps represent about 4.0 MW_t of this installed capacity. The quantity of thermal water produced for direct uses in 2002 was approximately 22 million m³, with an average utilization temperature of 31 °C. The main consumer of geothermal energy is agriculture (68% of the total geothermal heat dedicated to direct uses). The geothermal water is used only in five spas for space heating and sanitary hot water (SHW), although there are 260 spas in the country, and the thermal water produced has an average surface temperature of 68 °C. The total heat capacity installed in the spas is approximately 1250 MW_t; this is not provided by geothermal but could be, i.e., geothermal could provide more than three times the geothermal capacity utilized in direct uses by 31 December 2002 (324.5 MW_t).     

Low-temperature geothermal energy use in Iceland

The results are given of a recent survey of the utilization of geothermal energy produced in low-temperature areas in Iceland. About 70% of Icelanders enjoyed geothermal district heating in 1979 and in the next 3–5 years this percentage should increase to about 80%. Most of the district heating systems receive hot water from low-temperature (reservoir temperature less than 150°C) geothermal areas. In late 1980 the thermal power above 15°C used for district heating amounted to 850 MW while the total low-temperature use was about 950 MW-thermal.     

Environmental aspects of geothermal energy utilization

Geothermal energy is a clean and sustainable energy source, but its development still has some impact on the environment. The positive and negative aspects of this environmental impact have to be considered prior to any decision to develop a geothermal field, as well as possible mitigation measures. The main environmental effects of geothermal development are related to surface disturbances, the physical effects of fluid withdrawal, heat effects and discharge of chemicals. All these factors will affect the biological environment as well. As with all industrial activities, there are also some social and economic effects. In Iceland an enforcement program was launched in the early 1990s to study the environmental impact of developing geothermal resources. Work began on tackling the environmental issues relative to the high-temperature geothermal fields under development in Iceland. Research was conducted on microearthquake activity in geothermal areas and a methodology developed for mapping steam caps. The foundations were laid of networks for monitoring land elevation and gravity changes. Baseline values were defined for the concentrations of mercury and sulfur gases. Groundwater monitoring studies were enforced. Atmospheric dispersion and reaction of geothermally-emitted sulfur gases and mercury were studied. Aerial thermographic survey methods were refined and tested and their capacity to detect and map changes in surface manifestations with time was demonstrated. To further the use of geothermal energy worldwide the International Energy Association set up a Geothermal Implement Agreement (GIA) in 1997; its environmental Annex has been actively implemented, with several projects still under way.     

Barriers and enablers to geothermal district heating system development in the United States

According to the US Energy Information Administration, space and hot water heating represented about 20% of total US energy demand in 2006. Given that most of this demand is met by burning natural gas, propane, and fuel oil, an enormous opportunity exists for directly utilizing indigenous geothermal energy as a cleaner, nearly emissions-free renewable alternative. Although the US is rich in geothermal energy resources, they have been frequently undervalued in America's portfolio of options as a means of offsetting fossil fuel emissions while providing a local, reliable energy source for communities. Currently, there are only 21 operating GDHS in the US with a capacity of about 100 MW thermal. Interviews with current US district heating operators were used to collect data on and analyze the development of these systems. This article presents the current structure of the US regulatory and market environment for GDHS along with a comparative study of district heating in Iceland where geothermal energy is extensively utilized. It goes on to review the barriers and enablers to utilizing geothermal district heating systems (GDHS) in the US for space and hot water heating and provides policy recommendations on how to advance this energy sector in the US.     

Geothermal space heating

The use of geothermal resources for space heating dominates the direct use industry, with approximately 37% of all direct use development. Of this, 75% is provided by district heating systems. In fact, the earliest known commercial use of geothermal energy was in Chaudes-Aigues Cantal, France, where a district heating system was built in the 14th century. Today, geothermal district space heating projects can be found in 12 countries and provide some 44,772 TJ of energy yearly. Although temperatures in excess of 50 °C are generally required, resources as low as 40 °C can be used in certain circumstances, and, if geothermal heat pumps are included, space heating can be a viable alternative to other forms of heating at temperatures well below 10 °C.     

World geothermal power generation in the period 2001–2005

A review has been made of all the country update papers submitted to the World Geothermal Congress 2005 (WGC2005) from countries in which geothermal electricity is currently being generated. The most significant data to emerge from these papers, and from follow-up contacts with representatives of these countries, are: (1) a total of 24 countries now generate electricity from geothermal resources; (2) the total installed capacity worldwide is approximately 8930 MW_e, corresponding to about 8030 MW_e running capacity and electric energy production is nearly 57,000 GWh (early 2005 data); (3) Costa Rica, France (Guadeloupe), Iceland, Indonesia, Italy¹, Kenya, Mexico, Nicaragua, Russia, and the USA have increased the capacity of their power plant installations by more than 10% with respect to the year 2000; (4) the new members of the geothermal electricity generating community comprise Austria, Germany and Papua New Guinea; (5) the installed capacity in Argentina and Greece is now null since their geothermal power plants have been dismantled; (6) nineteen countries have carried out significant geothermal drilling operations since 2000, with 307 new wells drilled.