Ground heat exchangers—A review of systems, models and applications

Florides, Georgios A.; Kalogirou, Soteris A.

doi:10.1016/j.renene.2006.12.014

Cited by 599 publications

(204 citation statements)

References 17 publications

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“…For that, brine is circulated either in vertical, u-shaped pipes in ground boreholes of depths between 50 and 300 m, where the ground temperature is more or less constant all year long or in horizontal pipe arrangements at a depth of about 1-4 m, where the ground temperature is dominated by solar irradiation and precipitation and hence varies with the seasons. 147 The second approach is usually more cost-effective but can only be used if sufficient space is available around the building and hence is not well suited in cities. In water-water heat pump systems, flowing water, often times ground water, is used as the heat source; whereas, in air-water systems, heat is extracted from the surrounding air.…”

Section: Heating Systemsmentioning

confidence: 99%

Energy in buildings—Policy, materials and solutions

Koebel

Wernery

Malfait

2017

MRS Energy & Sustainability

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Buildings account for ∼40% of global energy demands, and the increased adoption of innovative solutions for buildings represents an enormous potential to reduce energy demands and greenhouse gas emissions. Here, we critically review the current and future materials and solutions for the construction sector. We describe how policy affects innovative businesses and the adoption of new products and solutions. We investigate how the building envelope and user behavior determine building energy demands. Compared to conventional solutions, superinsulation materials (vacuum insulation panels, silica aerogel) can achieve the same thermal performance with drastically thinner insulation. With low-emissivity coatings and appropriate filler gasses, double and triple glazing reduces thermal losses by an order of magnitude. Vacuum and aerogel glazing reduce these even further. Switchable glazing solutions maximize solar gains during wintertime and minimize illumination demands whilst avoiding overheating in summer. Upon integration of renewable energy systems, buildings become both producers and consumers of energy. Combined with the dynamic user behavior, temporal variations in energy production require thermal and electrical storage and the integration of buildings into smart grids and energy district networks. The combination of these measures can reduce the energy consumption of the building's stock by a factor of three.

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Section: Heating Systemsmentioning

confidence: 99%

Energy in buildings—Policy, materials and solutions

Koebel

Wernery

Malfait

2017

MRS Energy & Sustainability

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“…The types of heat pumps that are adaptable to geothermal energy are the water-to-air and the water-to-water. Heat pumps are available with heating capacities of less than 3 kW to over 1,500 kW [35,36].…”

Section: Heat Pumpsmentioning

confidence: 99%

Direct Utilization of Geothermal Energy

Lund

2010

Energies

132

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Abstract:The worldwide application of geothermal energy for direct utilization is reviewed. This paper is based on the world update for direct-use presented at the World Geothermal Congress 2010 in Bali, Indonesia (WGC2010) [1] which also includes material presented at three world geothermal congresses in Italy, Japan and Turkey (WGC95, WGC2000 and WGC2005). This report is based on country update papers prepared for WGC2010 and data from other sources. Final update papers were received from 70 countries of which 66 reported some direct utilization of geothermal energy for WGC2010. Twelve additional countries were added to the list based on other sources of information. The 78 countries having direct utilization of geothermal energy, is a significant increase from the 72 reported in 2005, the 58 reported in 2000, and the 28 reported in 1995. An estimate of the installed thermal power for direct utilization at the end of 2009, reported from WGC2010 is 48,493 MWt, almost a 72 % increased over the 2005 data, growing at a compound rate of 11.4% annually with a capacity factor of 0.28. The thermal energy used is 423,830 TJ/year (117,740 GWh/yr), about a 55% increase over 2005, growing at a compound rate of 9.2% annually. The distribution of thermal energy used by category is approximately 47.2% for ground-source heat pumps, 25.8% for bathing and swimming (including balneology), 14.9% for space heating (of which 85% is for district heating), 5.5% for greenhouses and open ground heating, 2.8% for industrial process heating, 2.7% for aquaculture pond and raceway heating, 0.4% for agricultural drying, 0.5% for snow melting and cooling, and 0.2% for other uses. Energy savings amounted to 250 million barrels (38 million tonnes) of equivalent oil annually, preventing 33 million tonnes of carbon and 107 million tonnes of CO 2 being release to the atmosphere which includes savings in geothermal heat pump cooling (compared to using fuel oil to generate electricity).

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“…The former is preferred when the installation area is limited and is characterized by high installation costs due to drilling operation. The latter, located slightly below the Earth's surface (1-2 m depth), known also as very shallow geothermal (VSG) systems, is attractive due to its merits of low installation cost and less restricted legal constraints and easy maintenance, even if ample ground areas are required [12,13].…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, they are also a valid alternative to vertical systems installed at shallow depths (up to 25 m) [27][28][29][30]. Anyway, used as horizontal collector, helix requires shorter trenches and less land space [12], so a great interest in their possible implementation is registered.…”

Section: Introductionmentioning

confidence: 99%

Factors Influencing the Thermal Efficiency of Horizontal Ground Heat Exchangers

Sipio

Bertermann

2017

Energies

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Abstract:The performance of very shallow geothermal systems (VSGs), interesting the first 2 m of depth from ground level, is strongly correlated to the kind of sediment locally available. These systems are attractive due to their low installation costs, less legal constraints, easy maintenance and possibility for technical improvements. The Improving Thermal Efficiency of horizontal ground heat exchangers Project (ITER) aims to understand how to enhance the heat transfer of the sediments surrounding the pipes and to depict the VSGs behavior in extreme thermal situations. In this regard, five helices were installed horizontally surrounded by five different backfilling materials under the same climatic conditions and tested under different operation modes. The field test monitoring concerned: (a) monthly measurement of thermal conductivity and moisture content on surface; (b) continuous recording of air and ground temperature (inside and outside each helix); (c) continuous climatological and ground volumetric water content (VWC) data acquisition. The interactions between soils, VSGs, environment and climate are presented here, focusing on the differences and similarities between the behavior of the helix and surrounding material, especially when the heat pump is running in heating mode for a very long time, forcing the ground temperature to drop below 0 • C.

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Ground heat exchangers—A review of systems, models and applications

Cited by 599 publications

References 17 publications

Energy in buildings—Policy, materials and solutions

Energy in buildings—Policy, materials and solutions

Direct Utilization of Geothermal Energy

Factors Influencing the Thermal Efficiency of Horizontal Ground Heat Exchangers

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