Experience in developing and utilizing geothermal resources in iceland

Geothermal energy plays a larger role in the energy economy of Iceland than in any other country-Iceland is The Geothermal Country. This development dates back to 1930, when the first district heating system was started in Reykjavik, and since then geothermal water and steam have been utilized for a broad range of applications. Iceland has seen an unprecedented activity of geothermal projects over the past decade; geothermal district heating systems being installed wherever possible in cities and rural areas, a 30 MW_e, electric power plant at Krafla, small scale production of salt and carbon dioxide, heat extracted from the newly erupted lava in the Westman Islands for district, heating, increased use in industry and agriculture, and now recently an explosive development in fish farming. For a number of years the investment in geothermal projects represented 1.5% of the gross national product of Iceland.The largest use of geothermal energy in Iceland is for space heating and domestic use. At the moment 85% of all houses in the country are heated with geothermal water. This is of great importance in a country where heating is required practically throughout the year. The climate is rather temperate ranging from −15 to +20°C, and with the building codes now in effect that call for double and triple glazing and 150–200 mm of roof insulation, heating demand is 20 W/m³ and the annual usage 60–80 kWh/m³. Heating of greenhouses, industrial drying, fish farming, swimming pools, chemical production and electric power generation also make use of this energy source.This development has on the whole been very successful from the economic and technical standpoint, and has contributed to the wellbeing of the population of some 240,000 persons.This review paper will focus on some of the engineering experience gained in harnessing this “unconventional” energy source.     

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.     

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.     

Geothermal energy utilization in Turkey

This paper investigates the status of geothermal development in Turkey as of the end of 1999. Turkey is one of the countries with significant potential in geothermal energy. Resource assessments have been made many times by the Mineral Research and Exploration Directorate (MTA) of Turkey. The main uses of geothermal energy are mostly moderate‐ and low‐temperature applications such as space heating and domestic hot water supply, greenhouse heating, swimming and balneology, industrial processes, heat pumps and electricity generation. The data accumulated since 1962 show that the estimated geothermal power and direct use potential are about 4500 MW_e and 31 500 MW_t, respectively. The direct use capacity in thermal applications is in total 640 MW_t representing only 2 per cent of its total potential. Since 1990, space heating and greenhouse developments have exhibited a significant progress. The total area of greenhouses heated by geothermal energy reached up to about 31 ha with a heating capacity of 69.61 MW_t. A geothermal power plant with a capacity of 20.4 MW_e and a CO₂ factory with a capacity of 40000 ton yr^?1 have been operated in the Denizli‐Kizildere field since 1984 and 1986, respectively. Ground source heat pumps have been used in residential buildings for heating and cooling for approximately 2 years. Present applications have shown that geothermal energy in Turkey is clean and much cheaper compared to the other energy sources like fossil fuels and therefore is a promising alternative. As the projects are recognized by the public, the progress will continue. Copyright © 2001 John Wiley & Sons, Ltd.     

Potential of geothermal energy in the Kingdom of Saudi Arabia

The Kingdom of Saudi Arabia has rich geothermal energy resources. In Saudi Arabia, the studies on geothermal resources exploration were started in 1980. Saudi Arabia is among the most geothermally active countries in the Middle East. The geothermal power plants are not yet installed in Saudi Arabia. Some direct-use low-grade geothermal applications are already installed in the five last years. Some refreshment and swimming pools are already constructed in the Bani Malik-Jizan area. Geothermal energy can be utilized in various forms such as direct use, electricity generation, space heating, heat pumps, greenhouse heating, and industrial usage. The Kingdom of Saudi Arabia government has plans to become completely powered by difference forms of renewable energy such as solid waste, solar, geothermal, and wind.     

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.     

Production engineering in geothermal technology: A review

Geothermal energy is abundant and renewable, but only a very small fraction can currently be converted commercially to electricity and heating value with today's technology. In recent years, the installed geothermal capacity worldwide has more than doubled. The increase in the use of geothermal energy is the result of a multi-disciplinary effort. Highlighted are some production engineering advances that have played a significant part in making geothermal a competitive renewable energy resource.     

Multiple integrated applications for low-to medium-temperature geothermal resources in Iceland

There is an increasing global demand for a faster, more expansive development in the energy sector, in order to improve the standard of living of the world's population by the creation of more jobs and better living conditions. The public is, however, well aware of the damage that has been done to the environment, in the form of deforestation, despoiling of lakes and rivers and, in particular, greenhouse effects, and it is unwilling to further sacrifice its natural environment. This decision puts pressure on scientists, engineers and developers to find ways and means of attaining “sustainable energy development”. In other words, the challenge now is to achieve the sustainable development of alternative renewable energy resources. Sustainability may be achieved in a number of ways, but the one most likely to result in a rapid increase in energy output without a deleterious impact on the environment is the revamping and integration of what we already have. This paper attempts to address sustainability as it applies to geothermal energy. We describe the concept of a multiple integrated use of geothermal energy, including the tenable benefits that can be obtained from applying this concept, such as a longer reservoir lifespan, a lower specific environmental impact, and greater marketing flexibility and profitability. The paper also emphasises the importance of achieving a maximum effective temperature drop across the application, commensurate with a minimum flow rate, optimal pumping characteristics and minimal fluid extraction from the geothermal reservoir. In geothermal house heating systems this means using large and effective radiators, dual-pipe heating systems, and thermostatic controls on each radiator. Where modifications to existing house heating systems are not feasible, e.g. by conversion from a single-pipe to a dual-pipe system or installation of larger radiators, an alternative solution is to adopt a cascaded flow of the geothermal fluid through a combination of heating systems operating at different temperature levels. For economic reasons it is always better to use the geothermal water directly if its chemical quality permits us to do so, otherwise heat exchangers made of resistant materials will be needed to isolate the geothermal fluid from the heating fluid in order to avoid corrosion or scaling in the pipes and radiators. The heat exchangers should be designed in such a way as to obtain a maximum temperature drop of the geothermal fluid. The paper also describes some heating system configurations, the characteristics of geothermal heating systems and their automatic control systems, as well as recommended geothermal field management and monitoring systems. The paper also includes a few examples of existing projects to demonstrate what has already been achieved and what could be done in the future; some suggestions are also made for new developments and innovations to make geothermal energy more generally attractive and useful worldwide.     

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.     

国外能源公司地热能利用现状以及对中国石化的启示

地热能作为一种无污染、可再生的清洁能源,具有稳定可靠、成本低廉、清洁环保等优点。国外能源公司在地热能利用方面积累了成功的技术和管理经验．其中以冰岛绿源公司为代表的地热供暖、以雪佛龙为代表的地热发电、以壳牌为代表的干热岩发电处于国际领先地位。这些公司都拥有雄厚的资金实力、良好的国际声誉以及完整的产业链;并且都集中优势资源,重点发展某一项地热业务．而后再逐渐向地热能利用的其他领域扩张;同时还具备完善的科研设备和一流的科研人员,注重科技创新。中国石化正在积极扩大地热能研究和利用工作,旗下新星石油公司已发展成为国内常规地热能开发利用的第一大公司。截至2012年底,新星石油公司地热供暖能力达1000×10^4m2,约占全国常规地热供暖面积的25％。今后中国石化应逐步拓展地热能利用范围。延伸地热能利用产业链;加强科研攻关,积极创新,促进地热开发利用关键技术研发及推广应用;同时要加强国际交流与合作,加快地热开发利用技术的制度建设,并积极争取国家、地方的优惠政策和支持,推动我国地热产业快速健康发展。     

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.     

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.     

太阳能与浅层地热能联合供暖运行模式分析

文章通过太阳能与浅层地热能联合供暖的必要性,介绍了一种太阳能与浅层地热能联合供暖系统,探讨了联合供暖的运行模式,并对其经济性进行了分析,为综合利用太阳能和浅层地热能提供参考。     

The use of natural gas and geothermal energy in school units. Greece: A case study

The ever-increasing degradation of the environment along with high demands for energy consumption in buildings has prompted many countries to use other energy sources such as natural gas and geothermal energy instead of oil.This study refers to the use of natural gas in school units in Greece. More specifically, it focuses on school units that are connected to the natural gas network and on the economic and environmental benefits arising from this.In this context, the advantages and disadvantages in using natural gas are compared with those resulting from the use of geothermal energy. In areas which have a significant geothermal potential, the choice of geothermal heating and cooling of large school units is the best solution, but this however does not apply to all areas. Clearly, the development of geothermal energy in school units is still in pilot stage.However, the use of natural gas in school units has been rising over the last decade and it has already contributed to some extent towards the reduction of carbon dioxide and towards saving natural resources. Thus, the survey shows clear advantages in using natural gas and in plans to extend its use to other school units.     

Prospects and problems for geothermal use in agriculture in Europe

The agricultural uses of geothermal energy were the centre of attention during the initial stages of geothermal direct applications in Europe, e.g. in Hungary, Macedonia, Bulgaria, Serbia. The focus now seems to be on district heating systems, integrated systems, large balneological/tourist centres, etc. This paper analyses the problems involved in the development of agricultural uses in different regions of Europe and how this sector can be promoted. An analysis of the situation in Europe and in Hungary, Macedonia and Greece, in particular, has revealed different requirements and potentials, different combinations of influencing factors, and the need for different development strategies. It is, however, clear from this analysis that the agricultural uses of geothermal energy are not in collision with modern trends in direct geothermal developments in Europe. On the contrary, they can improve the economic aspects of any district heating or integrated system by offering excellent possibilities for cascade use of the geothermal water and combinations of users with different day/night and seasonal heat requirements.     

A key review on performance improvement aspects of geothermal district heating systems and applications

This paper deals with a comprehensive analysis and discussion of geothermal district heating systems and applications. In this regard, case studies are presented to study the thermodynamic aspects in terms of energy and exergy and performance improvement opportunities of three geothermal district heating systems, namely (i) Balcova geothermal district heating system (BGDHS), (ii) Salihli geothermal district heating system (SGDHS), and (iii) Gonen geothermal district heating system (GGDHS) installed in Turkey. Energy and exergy modeling of geothermal district heating systems for system analysis and performance evaluation are given, while their performances are evaluated using energy and exergy analysis method. Energy and exergy specifications are presented in tables. In the analysis, the actual system operational data are utilized. In comparison of the local three district heating systems with each other, it is found that the SGDHS has highest energy efficiency, while the GGDHS has highest exergy efficiency.     

北方清洁供暖现状和趋势分析

冬季供暖是我国季节性能源需求波动的重要因素,推进冬季清洁取暖,关系北方地区广大群众温暖过冬、雾霾天能不能减少等问题,是能源生产和消费革命、农村生活方式革命的重要内容.本文梳理了我国冬季供暖工作近年来的进展和成绩,对我国供热热源结构、供热能效进行分析,提出了改进方向,并指出在推进清洁取暖中,扩大集中供热规模,推进煤改电、...     

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%.