scholarly journals Characterization of the Effects of Borehole Layouts in Geo-exchange

2021 ◽  
Author(s):  
Ying Lam Law
Keyword(s):  
Separation Distance ◽  
Ground Temperature ◽  
Ground Temperatures ◽  
Heating And Cooling ◽  
Aspect Ratios ◽  
Ground Source ◽  
Thermal Imbalance ◽  
Cooling Loads

In a ground-source heat pump (GSHP) system, when the heating and cooling loads are not balanced, the ground temperature may migrate up or down after a few years of operation. This change in ground temperature can lower system efficiency because of the ineffective heat transfer temperatures. The present work contributes to fundamental understanding of thermal imbalance in borehole design. Long term ground temperatures were simulated using finite element methods to imitate the performance of GSHP systems. Borehole field configurations are explored and different aspect ratios of borehole layouts were compared. In addition, an alternative borehole configuration was studied, which involves alternating the length of individual boreholes within a single system. The results of the studies expressed potential in alleviating the effects of thermal imbalance by changing borehole field layout and potential in reducing borehole separation distance by altering individual borehole lengths.

scholarly journals Characterization of the Effects of Borehole Layouts in Geo-exchange

2021 ◽  
Author(s):  
Ying Lam Law
Keyword(s):  
Separation Distance ◽  
Ground Temperature ◽  
Ground Temperatures ◽  
Heating And Cooling ◽  
Aspect Ratios ◽  
Ground Source ◽  
Thermal Imbalance ◽  
Cooling Loads

In a ground-source heat pump (GSHP) system, when the heating and cooling loads are not balanced, the ground temperature may migrate up or down after a few years of operation. This change in ground temperature can lower system efficiency because of the ineffective heat transfer temperatures. The present work contributes to fundamental understanding of thermal imbalance in borehole design. Long term ground temperatures were simulated using finite element methods to imitate the performance of GSHP systems. Borehole field configurations are explored and different aspect ratios of borehole layouts were compared. In addition, an alternative borehole configuration was studied, which involves alternating the length of individual boreholes within a single system. The results of the studies expressed potential in alleviating the effects of thermal imbalance by changing borehole field layout and potential in reducing borehole separation distance by altering individual borehole lengths.

scholarly journals Characterization of the Effects of Borehole Configuration and Interference with Long Term Ground Temperature Modelling of Ground Source Heat Pumps

2021 ◽  
Author(s):  
Ying Lam E. Law ◽  
Seth B. Dworkin
Keyword(s):  
Fast Food ◽  
High Efficiency ◽  
Separation Distance ◽  
Heat Pumps ◽  
Ground Temperature ◽  
Conventional Heating ◽  
Ground Source Heat Pumps ◽  
Heating And Cooling ◽  
Ground Source

Ground source heat pumps (GSHPs) are an environmentally friendly alternative to conventional heating and cooling systems because of their high efficiency and low greenhouse gas emissions. The ground acts as a heat sink/source for the excess/required heat inside a building for cooling and heating modes, respectively. However, imbalance in heating and cooling needs can change ground temperature over the operating duration. This increase/decrease in ground temperature lowers system efficiency and causes the ground to foul—failing to accept or provide more heat. In order to ensure that GSHPs can operate to their designed conditions, thermal modelling is required to simulate the ground temperature during system operation. In addition, the borehole field layout can have a major impact on ground temperature. In this study, four buildings were studied—a hospital, fast-food restaurant, residence, and school, each with varying borehole configurations. Boreholes were modeled in a soil volume using finite-element methods and heating and cooling fluxes were applied to the borehole walls to simulate the GSHP operation. 20 years of operation were modelled for each building for 2x2, 4x4, and 2x8 borehole configurations. Results indicate that the borehole separation distance of 6 m, recommended by ASHRAE, is not always sufficient to prevent borehole thermal interactions. Benefits of using a 2x8 configuration as opposed to a 4x4 configuration, which can be observed because of the larger perimeter it provides for heat to dissipate to surrounding soil were quantified. This study indicates that it is important to carefully consider ground temperature during the operation of a GSHP. Borehole separation distances, layout, and hybridization should be studied to alleviate ground fouling problems.

scholarly journals Characterization of the Effects of Borehole Configuration and Interference with Long Term Ground Temperature Modelling of Ground Source Heat Pumps

2021 ◽  
Author(s):  
Ying Lam E. Law ◽  
Seth B. Dworkin
Keyword(s):  
Fast Food ◽  
High Efficiency ◽  
Separation Distance ◽  
Heat Pumps ◽  
Ground Temperature ◽  
Conventional Heating ◽  
Ground Source Heat Pumps ◽  
Heating And Cooling ◽  
Ground Source

Ground source heat pumps (GSHPs) are an environmentally friendly alternative to conventional heating and cooling systems because of their high efficiency and low greenhouse gas emissions. The ground acts as a heat sink/source for the excess/required heat inside a building for cooling and heating modes, respectively. However, imbalance in heating and cooling needs can change ground temperature over the operating duration. This increase/decrease in ground temperature lowers system efficiency and causes the ground to foul—failing to accept or provide more heat. In order to ensure that GSHPs can operate to their designed conditions, thermal modelling is required to simulate the ground temperature during system operation. In addition, the borehole field layout can have a major impact on ground temperature. In this study, four buildings were studied—a hospital, fast-food restaurant, residence, and school, each with varying borehole configurations. Boreholes were modeled in a soil volume using finite-element methods and heating and cooling fluxes were applied to the borehole walls to simulate the GSHP operation. 20 years of operation were modelled for each building for 2x2, 4x4, and 2x8 borehole configurations. Results indicate that the borehole separation distance of 6 m, recommended by ASHRAE, is not always sufficient to prevent borehole thermal interactions. Benefits of using a 2x8 configuration as opposed to a 4x4 configuration, which can be observed because of the larger perimeter it provides for heat to dissipate to surrounding soil were quantified. This study indicates that it is important to carefully consider ground temperature during the operation of a GSHP. Borehole separation distances, layout, and hybridization should be studied to alleviate ground fouling problems.

Attempt predicting slab-on-ground temperature for bioclimatic buildings

2020 ◽  
pp. 1-29 ◽  
Author(s):  
Hassan Mahach ◽  
Amin Bennouna ◽  
Brahim Benhamou
Keyword(s):  
Heat Transfer ◽  
Ambient Temperature ◽  
Simulation Software ◽  
Ground Temperature ◽  
Climatic Zones ◽  
Insulating Material ◽  
Ground Temperatures ◽  
Vertical Heat ◽  
Almost All

Abstract The prescriptive approach of the Moroccan Building Thermal Regulation (2015) provides for the insulation of buildings ground in almost all climatic zones of Morocco. This work demonstrates that it is an unnecessarily expensive constraint for most climatic zones of this country (only 8.6% of the cold semester days with slab-on-ground temperatures below 19°C and only 22% of the hot semester days above 26°C). This work shows also that the ground floor of a building is subject to (i) a slow mono-dimensional vertical heat transfer (outdoor ambient temperature long-term extrema delayed for – 22 days), (ii) a faster bi-dimensional horizontal heat transfer (outdoor ambient temperature singularities delayed for – 2 days for five meters from the edge of the building). To limit this, the authors recommend lateral insulation the first 50cm of the building foundations, with any adapted insulating material. In addition, building thermal simulation software need better site-specific models of the seasonal evolution of buildings slab-on-ground: a solution is proposed to obtain the seasonal variation of building slab-on-ground temperatures directly from the evolution of outdoor ambient temperature. It shows that this slab-on-ground temperature under cover varies almost like the at 1.6 m depth underground temperature of a non-covered soil.

scholarly journals Exploring the Impact of a District Sharing Strategy on Application Capacity and Carbon Emissions for Heating and Cooling with GSHP Systems

2020 ◽  
Vol 10 (16) ◽  
pp. 5543
Author(s):  
Yi Zhang ◽  
He Qi ◽  
Yu Zhou ◽  
Zhonghua Zhang ◽  
Xi Wang
Keyword(s):  
Carbon Emissions ◽  
Urban Areas ◽  
District Heating ◽  
Low Carbon ◽  
Heating And Cooling ◽  
Ground Source ◽  
Sharing Strategy ◽  
Low Carbon Energy ◽  
The Impact

To meet long-term climate change targets, the way that heating and cooling are generated and distributed has to be changed to achieve a supply of affordable, secure and low-carbon energy for all buildings and infrastructures. Among the possible renewable sources of energy, ground source heat pump (GSHP) systems can be an effective low-carbon solution that is compatible with district heating and cooling in urban areas. There are no location restrictions for this technology, and underground energy sources are stable for long-term use. According to a previous study, buildings in urban areas have demonstrated significant spatial heterogeneity in terms of their capacity to demand (C/D) ratio under the application of GSHP due to variations in heating demand and available space. If a spatial sharing strategy can be developed to allow the surplus geothermal capacity to be shared with neighbors, the heating and cooling demands of a greater number of buildings in an area can be satisfied, thus achieving a city with lower carbon emissions. In this study, a GSHP district system model was developed with a specific embedding sharing strategy for the application of GSHP. Two sharing strategies were proposed in this study: (i) Strategy 1 involved individual systems with borehole sharing, and (ii) Strategy 2 was a central district system. Three districts in London were selected to compare the performance of the developed models on the C/D ratio, required borehole number and carbon emissions. According to the comparison analysis, both strategies were able to enhance the GSHP application capacity and increase the savings of carbon emissions. However, the improvement levels were shown to be different. A greater number of building types and a higher variety in building types with larger differentiation in heating and cooling demands can contribute to a better district sharing performance. In addition, it was found that these two sharing strategies were applicable to different kinds of districts.

scholarly journals Hybridization of Heat Pump Systems With Natural Ventilation To Improve Energy Efficiency in Cooling Dominated Buildings

2021 ◽  
Vol 6 ◽  
pp. 33
Author(s):  
Nuno R. Martins ◽  
Peter J. Bourne-Webb
Keyword(s):  
Heat Pump ◽  
Natural Ventilation ◽  
Energy Performance ◽  
Ground Temperature ◽  
Improve Energy Efficiency ◽  
Final Energy ◽  
Heating And Cooling ◽  
Energy Needs ◽  
Energy Simulations ◽  
Cooling Loads

Building foundation piles can be used as heat exchangers in ground-source heat pump (GSHP) systems to provide highly efficient renewable heating and cooling (H&C). Unbalanced H&C loads lead to heat build-up in the ground, decreasing the system's overall performance. In this study, the introduction of natural ventilation (NV) has been examined to decrease cooling load imbalance in cooling-dominated buildings to improve system efficiency. Building energy simulations estimated the H&C loads for an office building in three Portuguese cities: Lisbon, Porto and Faro, yielding heating loads of 0.2–3.6 MWh/year and cooling loads of 260–450 MWh/year. Four renewable H&C technology scenarios were used to assess energy performance: (1) an air-source heat pump (ASHP) system; (2) a GSHP system utilizing energy piles; (3) hybrid ASHP-NV and (4) hybrid GSHP-NV. Over 50 years of operation, in Scenario (1) COP values of 2.45–2.55 (heating) and 3.62–4.15 (cooling) were obtained. In (2), COP values increased to 4.15–4.34 (heating) but fell to 3.36–3.79 (cooling), which increased annual final energy needs by 7–8%. Unbalanced cooling loads increased the ground temperature by 21–24 °C, which is unlikely to be acceptable. Compared to (1), introducing NV reduced cooling loads by 65–90% in Scenarios (3) and (4), with the final energy needs decreasing by 59–80% and 62–88%, respectively. A further benefit of the GSHP-NV hybrid is that the ground temperature increase was limited to 8‑12 °C. For cooling, the COP in (3) decreased compared to (1) (3.14–3.69), while in (4), COP improved to 3.45–6.10. This study concludes that hybrid GSHP-NV systems should be considered in some cooling-dominated scenarios.

WARMING ISSUES ASSOCIATED WITH THE LONG TERM SIMULATION OF HOUSING USING CFD ANALYSIS

2016 ◽  
Vol 11 (2) ◽  
pp. 57-74 ◽  
Author(s):  
Aiman Albatayneh ◽  
Dariusz Alterman ◽  
Adrian W. Page ◽  
Behdad Moghtaderi
Keyword(s):  
Air Temperature ◽  
Cfd Simulation ◽  
Heating And Cooling ◽  
And Performance ◽  
External Volume ◽  
Cooling Loads ◽  
Long Term Performance ◽  
Term Performance

The determination of internal building air temperature has an impact on the design and performance of a building in measuring thermal comfort and heating and cooling loads. There is software to assist with measuring internal building air temperature such as Autodesk CFD simulation. However, the use of Autodesk CFD simulation for the analysis appears to have an issue with simulations extending over a long term (i.e. months or years) as the internal air temperature in a building keeps rising with time. This paper addresses the challenges encountered using CFD simulation in the modelling of a building for long term performance. A new method to overcome the issue of the progressive rising of internal air temperature using two external air boundaries, one for the external volume (sky boundary) and the other surrounding the building, is suggested in the paper.

scholarly journals It Works—Long-Term Performance Measurement and Optimization of Six Ground Source Heat Pump Systems in Germany

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4691 ◽  
Author(s):  
Franziska Bockelmann ◽  
M. Norbert Fisch
Keyword(s):  
Heat Pump ◽  
Heat Exchangers ◽  
Control Strategies ◽  
Ground Source Heat Pump ◽  
Cooling Systems ◽  
Heating And Cooling ◽  
Ground Source ◽  
And Performance ◽  
Term Performance

Long-term studies of ground source heat pump (GSHP) heating and cooling systems for six different buildings (commercial, institutional and multi-family buildings) were conducted in Germany by Steinbeis-Innovationszentrum (SIZ) energy+. Three of them are equipped with borehole heat exchangers, and the others use energy piles as heat exchangers. This paper deals with a demonstration of the investigated buildings, the measured values and performance, and the obtained results include important findings and experiences, problems encountered and possible preventive measures to avoid mistakes. After ten years of operation, it can be stated that the systems work and achieve their planned efficiency but require constant control and regulation to avoid faulty operation. An analysis of the implemented control strategies shows that, for all these heating and cooling systems, holistically coordinated control strategies that are verified during commissioning are required.

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