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[en] Expansion of a large commercial geothermally-heated greenhouse is underway and requires additional geothermal fluid production. This report discusses the results of a cost-shared U.S. Department of Energy (DOE) and A.R. Masson, Inc. drilling project designed to construct a highly productive geothermal production well for expansion of the large commercial greenhouse at Radium Springs. The well should eliminate the potential for future thermal breakthrough from existing injection wells and the inducement of inflow from shallow cold water aquifers by geothermal production drawdown in the shallow reservoir. An 800 feet deep production well, Masson 36, was drilled on a US Bureau of Land Management (BLM) Geothermal Lease NM-3479 at Radium Springs adjacent to the A. R. Masson Radium Springs Farm commercial greenhouse 15 miles north of Las Cruces in Dona Ana County, New Mexico just west of Interstate 25 near the east bank of the Rio Grande. The area is in the Rio Grande rift, a tectonically-active region with high heat flow, and is one of the major geothermal provinces in the western United State
[en] This study deals with an exergetic performance evaluation of a geothermally heated building. This building used in the analysis has a volume of 1147.03 m3 and a net floor area of 95.59 m2, while indoor and exterior air temperatures are 20 and 0 deg. C, respectively. The geothermal heating system used for the heat production was constructed in the Ozkilcik heating center, Izmir, Turkey. Thermal water has a pressure of 6.8 bar, a temperature of 122 deg. C and a mass flow rate of 54.73 kg/s, while it is reinjected at 3.2 bar and 72 deg. C. The system investigated feeds three regions. Among these, the Ozkanlar region has supply/return pressure and temperature values of 4.6/3 bar and 80/60 deg. C, respectively. Energy and exergy flows are studied to quantify and illustrate exergy destructions in the overall system. Total exergy input rate to the system is found to be 9.92 kW and the largest exergy destruction rate occurs in the primary energy transformation at 3.85 kW
[en] In recent years, for several types of buildings and users, the choice of conditioning by heat pump and low enthalpy geothermal reservoir has been increasing in the Italian market. In fact, such systems are efficient in terms of energy and consumption, they can perform, even at the same time, both functions, heating and cooling and they are environmentally friendly, because they do not produce local emissions. This article will introduce the technology and will focus on critical points of a geothermal field design, from actual practice, to future perspectives for the geo exchanger improvement. Finally, the article presents a best practice case in Bologna district, with an economic analysis showing the convenience of a geothermal heat pump. Conclusions of the real benefits of these plants can be drawn: compared to a non-negligible initial cost, the investment has a pay-back period almost always acceptable, usually less than 10 years.
[it]Negli ultimi anni, per diversi tipi di edifici e di utenze, la scelta del condizionamento con pompa di calore e reservoir geotermico a bassa entalpia e in crescita sul mercato italiano. In realta, tali sistemi sono efficienti in termini di energia e di consumo, possono svolgere, anche al contemporaneamente, entrambe le funzioni, riscaldamento e raffreddamento, e sono rispettosi dell'ambiente, in quanto non producono emissioni locali. Questo articolo introduce la tecnologia e si concentra sui punti critici di una progettazione di un campo geotermico, dalla pratica attuale sino alle prospettive future per il miglioramento del geoscambiatore. Infine, l'articolo presenta un caso di studio in provincia di Bologna, con un'analisi economica che mostra la convenienza di una pompa di calore geotermica. Possono essere tratte alcune conclusioni sui reali benefici di questi impianti: rispetto ad un non trascurabile costo iniziale, l'investimento ha un tempo di ritorno quasi sempre accettabile, di solito inferiore ai 10 anni.
[en] Bulgarian territory is rich in thermal water of temperature in the range of 20 - 100oC. The highest water temperature (98oC) is measured in Sapareva banya geothermal reservoir. Electricity generation from geothermal water is not currently available in the country. The major direct thermal water use nowadays covers: balneology, space heating and air-conditioning, domestic hot water supply, greenhouses, swimming pools, bottling of potable water and geothermal ground source heat pumps (GSHP). The total installed capacity amounts to about 77.67 MW (excl. GSHP) and the produced energy is 1083.89 TJ/year. Two applications - balneology and geothermal ground source heat pumps show more stable development during the period of 2005 - 2010. The update information on the state-owned hydrothermal fields is based on issued permits and concessions by the state.
[en] Highlights: • A 3D model couples flow and heat transfer processes of DHE, wellbore and reservoir. • The model is validated against experimental data with a maximum error of 8.3%. • The entire temperature and flow fields of DHE system is analyzed comprehensively. • Performances of single U-tube, double U-tube and spiral tube are compared. • Effects of key factors on heat extraction performance of DHE system are studied. - Abstract: The downhole heat exchanger (DHE) geothermal system is commonly used to exploit geothermal energy for space heating. In this paper, a 3D unsteady state numerical model is established to couple fluid flow and heat transfer processes of DHE system. The model is validated by field experimental data. Temperature and velocity fields are analyzed to understand thermal process of DHE system. Heat extraction performances of three different DHE structures, including single U-tube, double U-tube and spiral tube, are compared. Subsequently, cases are studied to investigate how key parameters affect DHE performance. Simulation results depict that spiral-tube has the best heat extraction performance. As working fluid mass flow rate rises, outlet temperature declines and thermal power increases. When inlet temperature ascends, outlet temperature rises while thermal power decreases. Effects of reservoir porosity and tube wall heat conductivity on DHE performance are minor. Higher subsurface water velocity and larger rock heat conductivity can improve DHE performance, but the former has a more significant influence. Besides, subsurface water flow direction has neglected influence on performances of single and double U-tube, but appreciable impact on that of spiral tube. Key findings of this work are beneficial for optimal design and optimization of DHE geothermal system.
[en] This publication, illustrated by examples of application and their characteristics, proposes an overview of surface geothermal energy through six good reasons to choose it: a well controlled bill, an environmental exemplary way, a promotion of local resources, an energy which is adaptable to anticipate future challenges, an energy which is harmoniously integrated into its environment, and a proven technology.
[en] This publication first proposes a brief overview on the status, context and perspectives of geothermal energy in France by evoking the great number of heat pumps installed during the last decades and the choice made by public and private clients for this source of heating and cooling. While indicating how geothermal energy intervenes during a building project, this publication outlines that this energy is discrete and renewable, and that its technology is proven. Some examples are then evoked: use of geothermal energy for a public building in Saint-Malo, for estate projects near Paris, for a shopping centre in Roissy, and for office buildings
Atlas of the very-low-energy geothermal potential of the Centre region - Final report + Intermediate report + Cartographic and statistical study of specific flow rates of water drillings - Intermediate report n. 2a + Geometry and piezometric levels of the main aquifer formations - Intermediate report n. 2b
[en] A first report recalls some definitions (geology and aquifers in the Centre region, possible production flow rate, depth of aquifers and of piezometric levels, chemical characteristics of underground waters, sheet temperature), reports the study of the geothermal potential of aquifers, proposes a map of geothermal potentialities and a typology of buildings which may be heated by using geothermal energy. The second report proposes an overview of the French energy context and political tools, a general recall of geothermal energy (production situations and processes), the principles and implementation of heat pumps (on surface aquifer and on underground water), and a regional assessment (number of operations, underground water resources). The third report describes the geological and hydrogeological contexts of the Centre region (geological map, aquifer systems, alluvial systems, hydrogeological domains, aquifer overlapped formations), reports and discusses data related to surface aquifers, reports the determination of geological levels captured by the studied water drillings, reports a cartographic analysis and a statistical analysis of specific flow rates. Results are compared with those of previous studies, and synthesis maps are proposed. The fourth report describes the geometry of the main aquifer formations of the Centre region, and provides piezometric maps of water sheets located in different geological formations of the region
[en] Geothermal energy is a renewable energy source which consists in exploiting the heat coming from the Earth. It covers a wide range of techniques and applications which are presented in this article: 1 - the Earth, source of heat: structure of the Earth, geodynamic model and plate tectonics, origin of heat, geothermal gradient and terrestrial heat flux; 2 - geothermal fields and resources; 3 - implementation of geothermal resources: exploration, main characteristic parameters, resource exploitation; 4 - uses of geothermal resources: power generation, thermal uses, space heating and air conditioning heat pumps, district heating, addition of heat pumps; 5 - economical aspects: power generation, heat generation for district heating; 6 - environmental aspects: conditions of implementation, impacts as substitute to fossil fuels; 7 - geothermal energy in France: resources, organisation; 8 - conclusion. (J.S.)
[en] Highlights: ► The doublet geothermal heating system at Rotorua Hospital has a unique design. ► The system has been running with 300 % redundancy and 100% availability since 1977. ► Geothermal fluid with more than 130 °C is produced from 85 meter depth only. ► Full infield reinjection insures the sustainability of the shallow resource. ► Two-phase flow and non condensable gas reduces the overall heat transfer coefficient. - Abstract: Rotorua township is situated on top of a shallow geothermal reservoir within the Taupo Volcanic Zone of New Zealand. The resource is easy to access for private users and is commonly used for domestic and commercial heating. The Rotorua Hospital is located on one of the up flows of the geothermal reservoir and uses a doublet geothermal heating system that was commissioned in 1977. The performance of the heating system is evaluated and the impact on the geothermal reservoir is assessed. The heating exchanger system has a unique design of 18 once through counter flow 4 m long heat exchangers connected in series. It was built with significant safety margin of 300% in redundant production well capacity and is reliably serving the hospital’s heating requirements at 100% availability with the potential to increase the heat output. The infield reinjection of the produced water is neither causing temperature decline nor pressure drawdown on the geothermal reservoir, which is following natural cycles. The chemistry of the produced fluid is not causing any significant scaling or corrosion in the heat exchangers. Recommendations were given to improve the data acquisition system for better understanding of the system performance.