Possibilities for the application of solar energy in the European Community agriculture

In this paper are described the methodology followed and the main results of a study performed under contract for the Commission of the European Communities. Its aims were to collect energy consumption data in European Community agriculture broken down by regions and final uses, to perform a state of the art of the solar energy systems that have been tried in agriculture, to analyze the variables and barries that influence the development of solar energy systems in agriculture and to provide a general assessment for each region regarding the various possible solutions for each agricultural application. Our study was limited to thermal forms of energy consumptions and the sectors analyzed were: rural houses (space heating and hot water production), shelter heating, hot water production for animal husbandry, greenhouse heating and crop drying. In any of the sectors we give an assessment on the possibilities of penetration of solar technologies in European Community countries.     

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.     

油区地热能综合利用方案分析——以福山油田为例*

油田区域地热资源十分丰富,并且存在大量的用热需求。在油田地区综合开发地热能,不仅可以解决油田伴热、社区供暖/制冷等问题,还可以降低环境污染,减少二氧化碳的排放,有利于油田的持续稳定发展。基于海南福山油田的地热资源条件及用能需求,将油田生产伴热、热泵尾水升温和地热驱动吸收式制冷技术相结合,设计了多种油田地热能综合利用方案,并计算比较了各个方案的经济收益,进一步分析了地热水温度和流量对各个方案适用性的影响,研究结果可为其他油田区域地热资源的综合开发利用提供参考。     

Heating requirements in greenhouse farming in southern Italy: evaluation of ground-source heat pump utilization compared to traditional heating systems

Greenhouse farming, where energy consumptions are mainly related to the greenhouses heating, is one of the sectors consuming the most energy in the agricultural industry. High costs and the uncertain availability of fossil fuels constrain the use of heating applications. Among possible solutions, the utilization of renewable heating systems such as geothermal energy through ground-source heat pump systems (GSHPs) at competitive prices has to be taken in consideration. The competitiveness of these systems depends mainly on the characteristics of the end-users, i.e., the annual heating loads. Few studies focusing on the potential of using these systems start with an analysis of the thermal requirements and end with a cost evaluation in tune with local assets, geo-climatic conditions, and landscape protection. This paper analyzes the greenhouse crop industry in the Apulia region in southern Italy, as a potential end-user of GSHP systems. Data collected from an area mainly devoted to greenhouse crop production have been used to (a) describe greenhouse farms, (b) define the heating requirements of a greenhouse model representative of the most used typology in the investigated area, and (c) examine the economic viability of greenhouse heating with GSHP systems. Both vertical and horizontal ground heat exchanger (GHE) configurations are compared with conventional fossil-fuel heating systems. In all scenarios considered, the observed payback periods appear reasonable and worthy of consideration. The results suggest that these technologies can fully satisfy the winter heating requirements in a cost-effective way and they can support the planning of measures aimed to improve the sector competitiveness.     

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.     

Present status of underground thermal utilization in Japan

Utilization of low-enthalpy geothermal energy in Japan, especially with the application of geothermal heat pumps, is far behind other industrial countries. In 1998, a feasibility study was made of utilizing Japan's low-enthalpy geothermal resources. Since 2001 the Geo-Heat Promotion Association of Japan (GeoHPJ) began its activities with the objective of installing 140,000 heat pump systems in private houses by the target year of 2010. The Geothermal Research Society of Japan has also launched new activities in this sector. Research groups in universities and other national institutes have started geoscientific research on the utilization of low-enthalpy resources and private, academic and governmental sectors have consequently begun promoting geothermal heat pump utilization.     

Recognising the potential for renewable energy heating and cooling

Heating and cooling in the industrial, commercial, and domestic sectors constitute around 40–50% of total global final energy demand. A wide range of renewable energy heating and cooling (REHC) technologies exists but they are presently only used to meet around 2–3% of total world demand (excluding from traditional biomass). Several of these technologies are mature, their markets are growing, and their costs relative to conventional heating and cooling systems continue to decline. However, in most countries, policies developed to encourage the wider deployment of renewable electricity generation, transport biofuels and energy efficiency have over-shadowed policies aimed at REHC technology deployment. This paper, based on the findings of the International Energy Agency publication Renewables for Heating and Cooling—Untapped Potential, outlines the present and future markets and compares the costs of providing heating and cooling services from solar, geothermal and biomass resources. It analyses current policies and experiences and makes recommendations to support enhanced market deployment of REHC technologies to provide greater energy supply security and climate change mitigation. If policies as successfully implemented by the leading countries were to be replicated elsewhere (possibly after modification to better suit local conditions), there would be good potential to significantly increase the share of renewable energy in providing heating and cooling services.     

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.     

The effectiveness of policy instruments in promoting bioenergy

Bioenergy could make a significant contribution in reducing greenhouse gas emissions in Europe and is unique in its potential to service all three of the major energy demand sectors for heat, electricity and transport fuels. Consequently during the last two decades many different initiatives have been launched and policy instruments employed in different countries to develop the bioenergy sector, some of which have been more successful than others.This paper analyses the relationship between the growth of bioenergy in four European states and national energy policy. The policy instruments used are critically evaluated alongside the evidence base of bioenergy capacity and output achieved. The possible reasons for success or failure of different instruments and any unexpected impacts are discussed and some general conclusions drawn.     

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.     

Greenhouse gas emission savings of ground source heat pump systems in Europe: A review

An overview is presented on the last decade of geothermal heating by ground source heat pumps (GSHPs) in Europe. Significant growth rates can be observed and today's total number of GSHP systems is above 1 million, with an estimate of about 1.25 million mainly used for residential space heating in 2011. These systems are counted among renewable energy technologies, though heat pump operation typically consumes electricity and thus only a fraction of the energy produced is actually greenhouse gas (GHG) emission free. Consequently, only in the most mature markets of the Scandinavian countries and in Switzerland, calculated emission savings reach more than 1% compared to standard heatings. However, Sweden shows that more than 35% is possible, with about one third of these systems in Europe concentrated in this country. Our calculations demonstrate the crucial role of country-specific heating practices, substituted heat mix and primary electricity mix for country-specific emission savings. For the nineteen European countries studied in 2008, 3.7 Mio t CO₂ (eq.) are saved in comparison to conventional practice, which means about 0.74% on average. This reveals that many countries are at an early stage with great potential for the future, but even if the markets would be fully saturated, this average would barely climb to about 30%. These numbers, however, take the current conditions as reference, and when extrapolated to the future can be expected to improve by greener electricity production and increased heat pump performance.     

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.     

Importance of geothermal energy and its environmental effects in Turkey

Geothermal energy, a relatively benign energy source when compared with other energy sources due to reduction in greenhouse gas emissions, is used for electricity generation and direct utilization. Turkey has a place among the first seven countries in the world in the abundance of geothermal resources, but it has only used about 4% of its potential. The paper presents the status of energy needs and renewables, potential, utilization and the importance of geothermal energy in Turkey. It also gives a comparison between geothermal energy and other energy sources regarding environmental issues. It is estimated that if the geothermal heating potential alone in Turkey is used, 5 million residences will be heated and as a result, releases of 48 million ton/year CO₂ emissions into the atmosphere will be prevented. In addition to this, if the other geothermal potential (i.e. electricity) is used it will provide considerable environmental benefits. Therefore, it is expected that geothermal energy development will significantly speed up in the future.     

Monitoring and operational results of a hybrid solar-biomass heating system

Solar thermal systems, that provide auxiliary energy for space heating, represent a growing opportunity in European countries like Austria and Germany. However, such systems are as yet not widely known in the rest of Europe, unlike thermosyphon water heating systems. In addition, the need for energy conservation and reduction of CO₂ emissions, to combat climate change, demands the use and advance of renewable energy sources in new sectors than for common domestic water heating.The purpose of this research work is to present a full cycle of operational results of a hybrid solar thermal-biomass space heating system in Greece.The hybrid heating system was installed at the Centre for Renewable Energy Sources (CRES), Pikermi, central Greece in September 2005 with the intension to provide all the heat requirements for a specific office block of 60 m² area. The system was analyzed and optimized over a period of 6 months. The solar contribution during the actual measurement period (60% of the operating period) covered 52.9% of the total heating demand.The operational results of this unit from November 2005 till April of 2006 are presented and analyzed. The main parameters presented here include the operation of the system, the results, the coverage fraction (f%) of the solar and the biomass subsystems, the actions taken to increase its efficiency and the technical problems faced along with possible solutions to overcome them.     

Heat Roadmap Europe: Combining district heating with heat savings to decarbonise the EU energy system

Six different strategies have recently been proposed for the European Union (EU) energy system in the European Commission's report, Energy Roadmap 2050. The objective for these strategies is to identify how the EU can reach its target of an 80% reduction in annual greenhouse gas emissions in 2050 compared to 1990 levels. None of these scenarios involve the large-scale implementation of district heating, but instead they focus on the electrification of the heating sector (primarily using heat pumps) and/or the large-scale implementation of electricity and heat savings. In this paper, the potential for district heating in the EU between now and 2050 is identified, based on extensive and detailed mapping of the EU heat demand and various supply options. Subsequently, a new ‘district heating plus heat savings’ scenario is technically and economically assessed from an energy systems perspective. The results indicate that with district heating, the EU energy system will be able to achieve the same reductions in primary energy supply and carbon dioxide emissions as the existing alternatives proposed. However, with district heating these goals can be achieved at a lower cost, with heating and cooling costs reduced by approximately 15%.     

Atlas of geothermal resources in Europe

The geothermal resources of most European countries have been estimated and compiled in the recently published Atlas of Geothermal Resources in Europe, a companion volume to the Atlas of Geothermal Resources in the European Community, Austria and Switzerland. Publication of this Atlas comes at a time when the promotion of a sustainable and non-polluting energy is high on the agenda of local energy suppliers, municipal administrations and all European governments. The participating countries are: Albania, Austria, Belarus, Belgium, Bosnia-Herzegovina, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Netherlands, Poland, Portugal, Romania, Russia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Ukraine and the UK. A volumetric heat content model for porous reservoirs was the basis for calculating the resources, assuming that exploitation of the geothermal resources would take place in a doublet well system. The geothermal reservoirs are defined in a set of 4 maps, by depth, thickness, temperature and resources. The assessment methodology is simple and is based on a small number of parameters so that regions with very limited data coverage can also be evaluated. An example is given in this paper of the eastern North German Basin. The maps presented in the Atlas permit a first order evaluation of the geothermal potential in terms of technical and economic viability. This uniform procedure applied to all countries and regions allows comparisons and serves as a guide for setting priorities and planning geothermal development. This Atlas also helps in the search for appropriate partners for international cooperation in geothermal exploration in Europe.     

Energy management in horticultural applications through the closed greenhouse concept,state of the art

The commercial greenhouse has the highest demand for energy as compared to all other agricultural industry sectors. Here, energy management is important from a broad sustainability perspective. This paper presents the state-of-the-art regarding one energy management concept; the closed greenhouse integrated with thermal energy storage (TES) technology. This concept is an innovation for sustainable energy management since it is designed to maximize the utilization of solar energy through seasonal storage. In a fully closed greenhouse, there is no ventilation which means that excess sensible and latent heat must be removed. Then, this heat can be stored using seasonal and/or daily TES technology, and used later in order to satisfy the heating demand of the greenhouse. This assessment shows that closed greenhouse can, in addition to satisfying its own heating demand, also supply the demand for neighboring buildings. Several energy potential studies show that summer excess heat of almost three times the annual heating demand of the greenhouse. However, many studies propose the use of some auxiliary system for peak load. Also, the assessment clearly point out that a combination of seasonal and short-term TES must be further explored to make use of the full potential. Although higher amount of solar energy can be harvested in a fully closed greenhouse, in reality a semi-closed greenhouse concept may be more applicable. There, a large part of the available excess heat will be stored, but the benefits of an integrated forced-ventilation system are introduced in order to use fresh air as a rapid response for primarily humidity control. The main conclusion from this review is that aspects like energy efficiency, environmental benefits and economics must be further examined since this is seldom presented in the literature. Also, a variety of energy management scenarios may be employed depending on the most prioritized aspect.     

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.