| 1. |
- Arghand, Taha, 1982, et al.
(författare)
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Combining direct ground cooling with ground-source heat pumps and district heating: Borehole sizing and land area requirements
- 2022
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Ingår i: Geothermics. - : Elsevier BV. - 0375-6505. ; 106
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Tidskriftsartikel (refereegranskat)abstract
- This article studies the potential combination of direct ground cooling (DGC) with district heating (DH) and ground source heat pumps (GSHP) to compare the required borehole depths and needed drilling areas. It also examines two different borehole sizing approaches to optimize investment costs and drilling areas. The results show that the required borehole depths in most cases are shorter for the DGC and DH combination than for the DGC and GSHP combination. It is also demonstrated that the optimal range of borehole outlet temperatures could be chosen based on the trade-off between borehole installation and terminal units’ costs.
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| 2. |
- Arghand, Taha, 1982, et al.
(författare)
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Combining direct ground cooling with ground-source heat pumps and district heating: Energy and economic analysis
- 2023
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 270
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Tidskriftsartikel (refereegranskat)abstract
- Direct ground cooling (DGC) is a method used in cold climates to provide cooling to buildings without the use of any mechanical refrigeration. When DGC is utilized for providing cooling, ground-source heat pumps (GSHPs) and district heating (DH) are the two commonly used technologies for providing heating to the buildings. This article investigates the coupling of DGC with GSHPs and DH in terms of purchased energy and lifecycle costs. An office building equipped with active chilled beams for cooling and radiators for heating is used as a reference. Six cases based on different combinations of building envelope characteristics and thus different building heating and cooling loads are considered. The results show that using DGC-DH significantly reduces the amount of purchased electricity. However, the total energy cost is lower when DGC-GSHP is used. In addition, the DGC-GSHP can be more viable when the ground loads are well balanced. Investment costs, including borehole installation and equipment costs, are lower for the DGC-DH in the majority of the investigated cases. The lifecycle cost is lower for the DGC-DH in most of the investigated cases due to lower equipment costs.
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| 3. |
- Arghand, Taha, 1982, et al.
(författare)
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Cooling of office buildings in cold climates using direct ground-coupled active chilled beams
- 2021
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 164, s. 122-132
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the use of a direct ground cooling system (DGCS) using active chilled beams for the cooling of office buildings in Sweden. The methodology of the study entails laboratory experiments to develop and validate a simulation model of the cooling system. The sensitivity of the input parameters, such as borehole heat exchanger (BHE) length, internal heat gains and room temperature set point, are studied with respect to BHE outlet fluid temperature and room thermal comfort. The results provide a practical insight into designing DGCSs with regard to borehole outlet fluid temperatures. The results also show that the thermal comfort criteria in the room are met by applying the DGCS even under the most critical design conditions of undisturbed ground temperature and internal heat gains. The sensitivity study quantifies the influence of the room temperature setpoint and internal heat gain intensity on the BHE length. The BHE outlet temperature level is more sensitive in shorter BHEs than in the longer ones, and BHE length and room temperature levels are highly correlated. Thus, the sizing of DGCS can benefit from a control system to allow the room temperature to float within a certain range.
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| 4. |
- Bergström, Anders, et al.
(författare)
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Field test of a floating thermal pile in sensitive clay
- 2021
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Ingår i: Geotechnique. - 0016-8505 .- 1751-7656. ; 71:4, s. 334-345
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Tidskriftsartikel (refereegranskat)abstract
- The response of floating pile foundations in deep deposits of soft clay is governed by the settlements within the clay deposit surrounding the piles. A long-duration thermal response test (TRT) has been performed to assess the impact of heating and cooling on the geotechnical performance of a vertically loaded slender tubular steel pile in a deep deposit of sensitive clay. The results from the instrumented test site indicate that negligible excess pore water pressures, up to 3 kPa during heating and down to -1·1 kPa during cooling, were generated in the soil adjacent to the pile for a 50 W/m heat flux. The heating rate was sufficiently low to facilitate the drainage of pore water. The influence radius for the excess pore water pressures, however, extended beyond the soil volume affected by temperature change. The absence of thermally triggered creep settlements could be explained by the overlap between the remoulded zone resulting from pile installation, the extent of the heating, and the low creep susceptibility of remoulded sensitive clay for moderate temperature changes. Furthermore, no difference in the ultimate bearing capacity was found between the thermal pile and the reference pile, which was only loaded with a serviceability load during the test series. The current test data, therefore, indicate that driven floating piles in a deep deposit of soft clay also function as heat exchanger piles with minimal detrimental effects, for similar operational conditions as used in the TRT. It should be noted, however, that other pile types that do not extensively remould the clay adjacent to the pile shaft may show more significant influence of the thermal changes.
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| 5. |
- Bournas, Iason, et al.
(författare)
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Energy renovation of an office building using a holistic design approach
- 2016
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 7:September 2016, s. 194-206
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a holistic approach to perform energy renovations of office buildings. A real case study is used to demonstrate how different software can be used to facilitate the work of architects and engineers during different design stages. Initially, the moisture safety of the building is coupled to its energy performance to define the optimum insulation level. The new interior layout is based on an initial daylight study, rather than on architectural intuition. On a second stage, shading and natural ventilation are studied to eradicate any cooling demand, while the interdependence between heating energy and daylight is assessed for the use of light-wells. To demonstrate the trade-offs between visual control and electrical lighting, different shading systems are examined for a cellular office. Finally, two alternate HVAC systems are analyzed to investigate whether passive standards can be achieved with an all-air system and/or a hydronic system.
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| 6. |
- Claesson, Johan, 1943, et al.
(författare)
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A load-aggregation method to calculate extraction temperatures of borehole heat exchangers
- 2012
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Ingår i: ASHRAE Transactions. - 0001-2505. ; 118:1, s. 530-539
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Konferensbidrag (refereegranskat)abstract
- Hourly simulations of extraction fluid temperatures from borehole heat exchangers tend to be very time consuming. A new load aggregation scheme to perform long-term simulations of borehole heat exchangers is presented. The starting point is the step-response function for the considered borehole heat exchanger and the corresponding long sequence of cells, each with a load and a weighting factor. On the first level, the original weighting factors are kept. On the following levels, 2, 4, 8, etc., the weighting factors are lumped together. The lumped weighting factors are obtained directly from the step-response function. The number of cells to be lumped together is chosen so that the extraction temperatures using lumped weighting factors give a sufficiently good approximation of the non-aggregated scheme. The new scheme is applied to a test case to simulate extraction fluid temperature over a 20-year time period. Comparison of the results from the new scheme with the non-aggregated setting shows that the new scheme can perform very accurate and fast simulations of borehole heat exchangers.
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| 7. |
- Claesson, Johan, 1943, et al.
(författare)
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Explicit Multipole Formulas for Calculating Thermal Resistance of Single U-Tube Ground Heat Exchangers
- 2018
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Borehole thermal resistance is both an important design parameter and a key performance characteristic of a ground heat exchanger. Another quantity that is particularly important for ground heat exchangers is the internal thermal resistance between the heat exchanger pipes. Both these resistances can be calculated to a high degree of accuracy by means of the well-known multipole method. However, the multipole method has a fairly intricate mathematical algorithm and is thus not trivial to implement. Consequently, there is considerable interest in developing explicit formulas for calculating borehole resistances. This paper presents derivation and solutions of newly derived second-order and higher-order multipole formulas for calculating borehole thermal resistance and total internal thermal resistance of single U-tube ground heat exchangers. A new and simple form of the first-order multipole formula is also presented. The accuracy of the presented formulas is established by comparing them to the original multipole method. The superiority of the new higher-order multipole formulas over the existing formulas is also demonstrated.
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| 8. |
- de Klijn-Chevalerias, M., et al.
(författare)
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The Dutch approach for assessing and reducing environmental impacts of building materials
- 2017
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Ingår i: Building and Environment. - : Elsevier BV. - 0360-1323. ; 111, s. 147-159
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Tidskriftsartikel (refereegranskat)abstract
- Buildings are one of the largest consumers of energy and materials, and hence they are also one of the largest contributors to negative environmental impacts. Traditionally, energy consumed by buildings during their operation phase was the most significant in their lifecycles and far exceeded the embodied energy. However, in contemporary low-energy buildings, the embodied energy is proportionally higher because of the prevalent use of energy-intensive materials. To determine the embodied energy and environmental impacts of building materials, the Dutch have developed an assessment method, which has also been adapted by BREEAM-NL. This paper offers an overview of the Dutch approach for assessing the environmental impacts of building materials and demonstrates its practical application. The use of the Dutch Assessment Method to identify, and quantify materials-related design improvements has been demonstrated through an exemplifying case study. It has been identified that the environmental impact of a building is largely influenced by the material choices made at the early design stage of the project.
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| 9. |
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| 10. |
- Javed, Saqib, 1978, et al.
(författare)
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A method to evaluate thermal response tests on groundwater-filled boreholes
- 2012
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Ingår i: ASHRAE Transactions. - 0001-2505. ; 118:1, s. 540-549
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Konferensbidrag (refereegranskat)abstract
- The design of borehole heat exchangers for ground source heat pump system applications requires thermal properties, like ground thermal conductivity and borehole thermal resistance, as inputs. These properties are often determined from an in-situ thermal response test of a pilot borehole. For groundwater-filled boreholes, the ground thermal conductivity and borehole resistance estimations are affected by the heat-injection rates used during the test. Most existing methods for evaluating thermal response tests were not originally developed to analyze tests on groundwater-filled boreholes, and these methods can sometimes give erroneous results in such situations. This paper presents a new method for the evaluation of thermal response tests on grouted and groundwater-filled boreholes. The method is based on an analytical solution, which considers the thermal capacities, thermal resistances, and thermal properties of all borehole elements. The proposed method simplifies the evaluation of thermal response tests on groundwater-filled boreholes and provides accurate estimations of ground thermal conductivity and borehole thermal resistance.
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