Present status of research and utilization of geothermal energy in China

China is troubled by a shortage of energy sources. This shortage is even more serious in rural areas. However, about 3000 active hydrothermal systems are spread over China's territory and are presumed to be related either to intraplate or to plate marginal thermal anomalies. Their energy content could, in some cases, make a valid contribution to the local energy demand. Electricity is at present generated in Yangbajain geothermal field (10 MW), direct uses still represent a very minor utilization. Geothermal research is under way all over the country.     

Prospects of future geothermal energy development

There are three categories of geothermal resources with huge resource bases: the hydrothermal convection system, the hot igneous system, and the regional conductive environment. However, under the present technical and economic condition, high temperature hydrothermal convection is the only commercially attractive resource for electric power generation, On the other hand, increasingly more attention is being paid to nonelectrical uses of moderate temperature geothermal resources.National and regional research efforts should be focused initially on the assessment and development of liquid-dominated hydrothermal resources, in order to establish confidence in geothermal energy as a viable energy option at the earliest possible time. With respect to the utilization problem of liquid-dominated resources, the development of cost-effective systems to use moderate-temperature resources for both electric and nonelectric applications would greatly expand the geothermal energy potential.Removal of the institutional uncertainties and legal barriers and encouragement by means of financial supports are necessary to stimulate the commercial activity of geothermal energy development.     

Small-medium size geothermal power plants for electricity generation

This paper describes the main methods of utilization of geothermal resources for electric energy production. A thorough review is also given of the general criteria adopted by ANSALDO in their design of new geothermal electric units. The objective of this design is to achieve a more rational exploitation of the source of the primary power. Along with the working characteristics of the units, the paper also describes the provisions taken to eliminate or reduce the problems arising when utilizing geothermal fluids.     

Application of geothermal energy for heating and fresh water production in a brackish water greenhouse desalination unit: A case study from Algeria

The aim of this paper was to outline a proposed a new brackish water greenhouse desalination unit powered by geothermal energy for the development of arid and relatively cold regions, using Algeria as a case study. Countries which have abundant sea/brackish water resources and good geothermal conditions are ideal candidates for producing fresh water from sea/brackish water. The establishment of human habitats in these arid areas strongly depends on availability of fresh water. The main advantage of using geothermal energy to power brackish water greenhouse desalination units is that this renewable energy source can provide power 24 h a day. This resource is generally invariant with less intermittence problems compared to other renewable resources such as solar or wind energy. Geothermal resources can both be used to heat the greenhouses and to provide fresh water needed for irrigation of the crops cultivated inside the greenhouses. A review of the geothermal potential in the case study country is also outlined.     

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.     

Enel activity in the research, exploration and exploitation of geothermal energy in Italy

In Italy the utilization of geothermal resources for industrial purposes began about 150 years ago. Prior to 1913, geothermal fluids were utilized both as a source of heat and chemical products; from 1913 to 1965, combined chemical and electric production was achieved; from 1965 on, power generation prevailed over chemical production, which was abandoned immediately thereafter; between 1975 and 1984, geothermal energy was mostly used for generating electricity, but a number of thermal projects were also started.An overview is given of Italian geothermal development after 1975, including electric production and direct applications of geothermal heat.More in particular, the research and development activity in the period 1975–1985 is first presented, and the criteria, programmes and development objectives through 1995 are then illustrated.     

The present status and the future development of renewable energy in China

As one of the biggest energy consuming countries, China has to pay a great attention to the development and utilization of renewable energy to meet the increasing energy demand and to protect its environment. In this paper, the present status of the resources, development and application of different kind renewable energies including solar thermal, wind, biomass, geothermal and ocean energies, are comprehensively summarized. The perspective of solar energy in China is outlined.     

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.     

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.     

Energy production and sustainable energy policies in Turkey

Turkey's demand for energy and electricity is increasing rapidly. Turkey is heavily dependent on expensive imported energy resources that place a big burden on the economy and air pollution is becoming a great environmental concern in the country. Turkey's energy production meets nearly 28% of its total primary energy consumption. As would be expected, the rapid expansion of energy production and consumption has brought with it a wide range of environmental issues at the local, regional and global levels. With respect to global environmental issues, Turkey's carbon dioxide (CO₂) emissions have grown along with its energy consumption. States have played a leading role in protecting the environment by reducing emissions of greenhouse gases (GHGs). In this regard, renewable energy resources appear to be the one of the most efficient and effective solutions for clean and sustainable energy development in Turkey. Turkey presently has considerable renewable energy sources. The most important renewable sources are hydropower, biomass, geothermal, solar and wind. Turkey's geographical location has several advantages for extensive use of most of these renewable energy sources. Turkey has a great and ever-intensifying need for power and water supplies and they also have the greatest remaining hydro potential. Hydropower and especially small hydropower are emphasized as Turkey's renewable energy sources. Turkey's hydro electric potential can meet 33–46% of its electric energy demand in 2020 and this potential may easily and economically be developed. This paper presents a review of the potential and utilization of the renewable energy sources in Turkey.     

Thermal analysis of multigeneration system using geothermal energy as its main power source

The study presented in this paper examines the operation of an integrated system. The study aims to present a method for utilizing geothermal energy in a way that minimizes energy waste and delivers maximum efficiency. A high-temperature geothermal well with a temperature of 300 °C is used as its primary source of energy. The system produces space heating, space cooling, electric power, hot water, freshwater and hydrogen as its outputs. These outputs utilize the excess energy that is obtained from the geothermal well, and by doing so, reduces waste, and increases the overall efficiency of the system. Among these outputs, freshwater and hydrogen are considered the most valuable, as water is an essential life resource and hydrogen is a prized form of energy. The novelty of this system compared to other geothermal sources is that it does not rely on any other source of input energy. It produces both freshwater, hydrogen and considerable amounts of electric power for commercial, industrial and/or residential use. Electric power is produced by two power cycles; the first one is a double flash steam cycle in the geothermal system and the second one is an organic Rankine cycle. 40% of the total electric power produced is sent to an electrolyzer to produce hydrogen gas. Freshwater is produced by single flash desalination. The system produces 22.1 MW of power as net electricity output. The system is assessed energetically and exergetically; it is found that the energy efficiency is 49.1%, while the exergy efficiency is 67.9%. Further parametric studies are carried out using Engineering Equation Solver (EES) to investigate the influence of operating conditions on the energy and exergy of the system. Moreover, major exergy destruction areas in the system are also identified.     

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.     

Front Cover

Until recently, the efficiency of generation and transmission of electric power was enhanced by increasing capacities of generating units and the voltages of transmission lines. Capabilities of new energy technologies (high-technology and high-efficiency gas-turbine units of small capacity, fuel cells, energy storage systems, FACTS, etc.) change this tendency radically. In the area of electric power generation, it resulted in a new notion, dispersed generation. In the past, these tendencies for capacity increase were also characteristic of Russia, including its Asian part, Current conditions make one review many fundamental concepts. On the whole, the trend to reject construction of large thermal and hydro power plants has been observed. The use of the up-to-date, economically efficient, and ecologically clean coal-combustion technologies is envisaged, since, in East Siberia and Far East Russia, coal will make up a considerable fraction of fuel supply to power plants for the foreseeable future. Construction of gas-fired power plants is also considered. Economic conditions for growth of dispersed generation in some areas arise. Available natural resources (geothermal energy, wind, gas and hydro energy, etc.) are conducive to it. In electric networks, DC transmission lines are the only possible solution for constructing interstate ties in the region. Firm rates of development in these directions will be determined by the global tendencies and prevailing conditions.     

Technical-economic aspects of the utilization of geothermal waters

This paper reports on the world energy consumption between 1960 and 1984 from primary energy sources (coal, natural gas, oil, hydropower, nuclear energy) and the same in percentages from 1925. This highlights the diminishing role of coal and the increased consumption of gas and oil. The latter has stabilized around 42% of the total after the drop in demand resulting from the oil crisis of 1973.The world energy consumption has then been divided into industrialized and developing countries. It appears that the latter, with a population equal to 68% of the total world population, consumed 23% of the world energy in 1982. Furthermore, the consumption figures show that the demand for domestic energy is much smaller in developing countries, and it is well-known that domestic energy consumed is one of the parameters used to assess standard of living.The total installed electric capacity throughout the world is then reported, divided between developed and developing countries, showing that the latter consumed 11% of all the electricity generated in the world in 1981. The world installed electric power of geothermal origin at the end of 1985 is shown, along with estimates for 1990. Geothermal energy represents 0.2% of the world electric power. This is obviously a small figure and indicates that geothermal energy plays a minor role on the world energy scene. However, if we distinguish between industrialized and developing countries, we can observe that, with their currently limited electrical consumption but good geothermal prospects, the developing countries could achieve quite a significant contribution to their total electric energy from that of geothermal origin, increasing at the moment from 3 to 19%.Finally, a comparison is made between electricity generating costs of different sources, showing that geothermal energy is competitive. A table illustrates the world evolution in installed geothermal capacity from 1950 to 1985.The non-electric uses of geothermal energy, on the other hand, have a rather insignificant role in both the developing and industrialized countries. It is unlikely that geothermal energy will ever achieve a greater significance in this sector, with a few rare exceptions.     

The geothermal exploration of Campanian volcanoes: Historical review and future development

Since Roman time, the heat produced by Neapolitan volcanoes was an appeal for people living in and outside the area, for the fruition of the famous thermal baths. This very large area, which spans from Campi Flegrei and Ischia calderas to Somma-Vesuvius volcano, is characterized by high temperature at shallow depth and intense heat flow, and is yet utilized for the bathing and spa treatment industry, while only in the middle of the 20th century a tentative of geothermal exploitation for energy production was performed. Pioneering researches of geothermal resource were carried out in Campanian region since 1930, until 1985, during which a large amount of geological data were collected. In this paper, we make for the first time a review of the history of geothermal explorations in the active Campanian volcanic area. By the analysis of a great amount of literature data and technical reports we reconstruct the chronology and the main information of the drillings performed since 1930 by the SAFEN Company and successively in the framework of the ENEL-AGIP Joint Venture for geothermal exploration. The available data are utilized to correlate the temperatures measured within the deeper wells with the possible sources of geothermal heat in the shallow crust, down to about 8-10 km of depth. Finally, we assess the geothermal potential of the hottest areas, Ischia Island and Campi Flegrei, which have shown the best data and favorable physical conditions for a reliable, and cost-effective, exploitation for thermal and electric purposes.     

The sustainability indicators of power production systems

One of the most important elements of economical and social development is to provide uninterrupted electric energy to consumers. The increasing world population and technological developments rapidly increase the demand on electric energy. In order to meet the increasing demand for sustainable development, it is necessary to use the consumable resources of the world in the most productive manner and minimum level and to keep its negative effects on human health and environment in the lowest level as much as possible. In this study, alignment of hydrogen fuel cells, hydroelectric, wind, solar and geothermal sourced electric energy systems, in addition to fossil fueled coal, natural gas and nuclear power plants, in respect to sustainability parameters such as CO₂ emission, land use, energy output, fresh water consumption and environmental and social effects is researched. Consequently, it has been determined that the wind and nuclear energy power plants have the highest sustainability indicators. The fuel cells that use hydrogen obtained by using coal and natural gas are determined as the most disadvantageous transformation technologies in respect to sustainability. This study contains an alignment related to today's technologies. Using of renewable energy resources especially in production of hydrogen, output increases to be ensured with nanotechnology applications in photovoltaic systems may change this alignment.     

Research on the generation of electricity from the geothermal resources in Simav region, Turkey

One of the greatest problems in using renewable energy sources is the great variability of energy level, both in the short and long term. Geothermal energy, by nature, has high availability because the source is not dependent on weather conditions, so it is among the most stable renewable energy sources. Geothermal energy has the potential to play an important role in the future energy supply of Turkey. Although Turkey has the second-highest geothermal energy potential in Europe, electricity generation from geothermal energy is rather low.This study examines the use of geothermal energy in electricity generation and investigates the applicability of the existent geothermal energy resources to electricity generation in the Kütahya–Simav region, Turkey. The binary cycle is used in the designed power plant for electricity generation from geothermal fluid in which the percentage of liquid is high and which is at lower temperature. In this power plant, R134a is chosen as the secondary fluid, whose boiling point temperature is lower than that of water, and is used instead of geothermal fluid in a second cycle. The thermal efficiency of the designed power plant is measured to be 12.93%.     

Research and development of geothermal energy production in Hungary

The basement of the Pannonian (Carpathian) basin is represented by Paleozoic metamorphic and Mesozoic dolomite and limestone formations. The Tertiary basin gradually subsided during the Alpine orogeny down to 6000 m and was filled by elastic sediments with several water horizons.A heat flow of 2.0 to 3.4 μcal/cm²s gives temperature gradients between 45 and 70 °C/km in the basin. At 2000 m depth the virgin rock temperature is between 110 and 150°C. 80 geothermal wells about 2000 m deep have shown the great geothermal potential of the basin.The main hot water reservoir is the Upper Pliocene (Pannonian) sandstone formation. Hot water is produced by wells from the blanket or sheet sand and sandstone, intercalated frequently by siltstone. Between a 100–300 m interval, 3 to 8 permeable layers are exploited resulting in 1–3 m³/min hot water at 80–99°C temperature.Wells at present are overflowing with shut-in pressures of 3–5 atm.The Pannonian basin is a conduction-dominated reservoir. Convection systems are negligible, hot igneous systems do not exist. The assessment of geothermal resources revealed that the content of the water-bearing rocks down to 3000 m amounts to 12,600 × 10¹⁸cal. In the Tertiary sediments 10,560 × 10¹⁸cal and in the Upper Pannonian, 1938 × 10¹⁸cal are stored. In the Upper Pannonian geothermal reservoir, below 1000 m, where the virgin rock temperature is between 70 and 140°C, the stored heat is 768 × 10⁸cal. A 10¹⁸ cal is equivalent to the combustion heat of 100 million tons of oil. The amount of recoverable geothermal energy from 768 × 10⁸cal is 7.42 × 10¹⁸cal, i.e. about 10,000 MW century, not considering reinjection.At present the Pannonian geothermal reservoir stores the greatest amount of identified heat which can be mobilized and used. Hungary has 496 geothermal wells with a nominal capacity of 428 m³/min, producing 1342 MW heat. 147 wells have an outflow temperature of more than 60°C producing 190 m³/min, that is, 845 MW. In 1974 290 MWyear of geothermal energy was utilized in agriculture, district heating and industry.     

地热资源的开发利用及可持续发展

地热资源作为一种新型能源矿产,具有分布广泛、易于开发等特点,其利用方式主要有地热发电和地热直接利用两种.我国具有良好的地热资源条件,主要为中低温地热资源.据计算,我国12个主要沉积盆地的地热可开采资源量为7500×1018J,相当于2560×108t标煤.当前,我国地热资源利用方式主要以供暖、洗浴、种植等直接利用为主;地热发电发展缓慢,主要分布在西藏;利用热泵技术开发地热资源得到了快速发展;油区地热资源的开发利用也取得了良好的经济和社会效益.但同时我国地热资源产业也面临着一些问题,包括大部分地区尚未开展地热资源勘查评价,影响了地热资源规划的制订及地热产业的发展;防腐、防垢技术还需要进一步加强研究;地热回灌率普遍过低;增强型地热系统研究有待加强等.为了促进地热资源的可持续发展,建议在加大地热资源勘查力度的同时,应以浅层地温能和热水型地热资源为主,发挥热泵技术的优势,开展地热资源的综合利用及梯级利用;重视和加快油气区地热资源的利用;在西藏等适宜地区加大高温地热能发电利用;集中全国优势技术力量,在一两个有利区域开展增强型地热系统技术探索;此外,走回灌开发道路是地热资源开发利用的必然选择.     

地热资源发电技术特点及发展方向

地热资源是一种清洁无污染、可再生的新型能源,对于发展低碳经济、实现可持续发展具有积极的作用.目前地热发电技术主要包括干蒸汽发电、扩容式蒸汽发电、双工质循环发电和卡琳娜循环发电等.其中干蒸汽发电系统工艺简单,技术成熟,安全可靠,循环效率可达20％以上,是高温地热田发电的主要形式;扩容式发电技术已在地热发电领域得到广泛应用,尤其是中高温地热田,二级扩容系统循环效率约为15％～20％;针对中低温地热资源,双工质循环发电技术是较为适用的,它由地热水系统和低沸点介质系统组成,循环效率较扩容式蒸汽发电技术可提高20％～30％;卡琳娜循环在低温地热资源应用领域中有其独特的优越性,通过调整氨和水的比例,可以适应低温地热水的发电特性,卡琳娜循环发电技术的循环效率比朗肯循环的效率高20％～50％.在低温地热资源的开发利用过程中,双工质循环和卡琳娜循环技术具有广阔的发展前景.作为一种新型地热资源,干热岩具有很高的开发利用价值.新型的联合循环发电技术是地热发电技术的发展方向.在浅层地热能得到大规模开发后,中深层地热资源和干热岩资源将成为地热发电技术新的资源,我国应注重中深层地热资源和干热岩资源的开发.