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Introduction
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May 2007 - present
Publications
Publications (49)
Raman-based Distributed Temperature Sensing (DTS) is a valuable tool for field testing and validating heat transfer models in Borehole Heat Exchanger (BHE) and Ground Source Heat Pump (GSHP) applications. However, temperature uncertainty is rarely reported in the literature. In this paper, a new calibration method is proposed for single-ended DTS c...
![Fig. 4.1. Total yearly energy [MWh] and water volume [10 3 m3] used...](profile/Mohammad-Abuasbeh-2/publication/353154176/figure/fig3/AS:1046063230238722@1626412317538/Total-yearly-energy-MWh-and-water-volume-10-3-m3-used-from-the-ATES-left-axis-to_Q320.jpg)
The majority of Aquifer Thermal Energy Storage (ATES) systems studies have been conducted in aquifer systems located in large sand aquifers. Esker formation present a more challenging geometrical complexity compared to typical sand aquifers. This study aims to conduct comprehensive and long term performance evaluation of doublet type ATES system in...
Ground Source Heat Pumps (GSHPs) connected to Borehole Heat Exchangers (BHEs) are a fast-growing technology for thermally efficient buildings. Therefore, areas with several independent GSHP installations close to each other are becoming more and more common. To guarantee an optimal operation of these systems, it is necessary to design them consider...
This paper presents a methodology for designing Laboratory Borehole Storages (LABS) intended to generate reference Thermal Response Functions (TRFs) for model validation. The design method is based on analytically-derived invariance requirements demanding the conservation of the Fourier and Biot numbers. Accordingly, convective boundary conditions...
Standard thermal response tests (TRT) are typically carried out to evaluate subsurface thermal parameters for the design and performance evaluation of borehole heat exchangers (BHE). Typical interpretation methods apply analytical or numerical solutions, which assume that the ground is homogeneous, isotropic and infinite. However in reality, the un...
Ground source heat pumps (GSHPs) are a state-of-the-art technology for heating, cooling and hot water production. They are already common in several countries and represent a promising technology for others. As the technology penetrates the market, the number of ground heat exchangers in densely populated areas may increase significantly. Therefore...
The residential sector accounts for a relevant share of global energy use; therefore it is important to use as much renewable energy as possible to satisfy its demand. Geothermal energy, among others, is nowadays used for this scope: more and more buildings in several countries are exploiting the underground to satisfy domestic heating, cooling and...
http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Akth%3Adiva-239937
This report presents the obtained results and performed tasks during the project Deep Boreholes for Ground-Source Heat Pumps, within the framework of the research program Effsys Expand.
A price model for the investment of GSHP system with deep Borehole Heat Exchangers (BHEs) is derived...
Thermal Response Testing is now a well-known and widely-used method allowing the determination of the local thermal or geometrical properties of a Borehole Heat Exchanger (BHE), those properties being critical in the design of GSHP systems. The analysis of TRTs is an inverse problem that has commonly been solved using an approximation of the ILS so...
This paper presents the design process of a 4x4 Laboratory Borehole Storage (LABS) model through analytical and numerical analyses. This LABS is intended to generate reference Thermal Response Functions (TRFs) as well as to be a validation tool for borehole heat transfer models. The objective of this design process is to determine suitable geometri...
With bore fields for energy extraction and injection, it is often necessary to predict the temperature response to heat loads for many years ahead. Mathematical methods, both analytical and numerical, with different degrees of sophistication, are employed. Often the g-function concept is used, in which the borehole wall is assumed to have a uniform...
This article details the permanent 2.6 km underground fiber optic based Distributed Temperature Sensing (DTS) system that was installed down to 69 meters below grade at the Department of Defenses first Borehole Thermal Energy Storage (BTES) system. The BTES is comprised of 306 boreholes filled with 32mm HDPE U-bends and graphite-enhanced bentonite...
This paper presents a performance study of deep borehole heat exchangers. The coaxial borehole heat exchanger (BHE) has been selected because for the present conditions it has a better performance than the conventional U-tube BHE. A numerical model has been developed to study the coaxial BHE. The model predictions are compared to detailed distribut...
In the mathematical simulation of bore fields for ground coupled heat pump (GCHP) systems, it has become a common practice to consider the boreholes as having a uniform temperature. As a rule the boreholes are hydraulically connected in parallel and the small temperature difference between incoming and outgoing heat carrier fluid justifies the assu...
In Sweden, there are more than 500 000 small and about 500 relatively large ground source heat pumps (GSHP) having a total installed capacity of about 5.6 GW delivering approximately 15 TWh energy per year. The operational lifetime and reliability of any GSHP depends heavily on the way the system is designed, installed and operated. In order to pro...
The most common secondary fluid used for the borehole heat exchangers in Sweden is an aqueous solution of ethyl alcohol (EA) due to its relatively good thermophysical properties and low toxicity. Commercially available ethyl alcohol based fluids in Sweden contain up to 10 wt-% denaturing agents in form of propyl alcohol (PA) and n-butyl alcohol (BA...
![Figure 1 Illustration of the group of buildings and the BTES [14].](profile/Patricia-Monzo-Carcel/publication/303462065/figure/fig1/AS:368505988894720@1464870082214/llustration-of-the-group-of-buildings-and-the-BTES-14_Q320.jpg)
This paper presents the description of the first stage of a project consisting on the
monitoring of a newly installed borehole thermal energy storage (BTES) system that
started to operate during the autumn of 2015. The BTES system is designed for
approximately 4 GWh per year of heat injection and 3 GWh per year of heat extraction
and will provide h...
One potential problem for the ground coupled heat pump is that the ground thermal properties is hardly to be known due to the complicated ground construction. The p(t)-linear average method has been proved that it can improve the accuracy of borehole thermal resistance. However, the p(t)-linear fluid temperature distribution approximation is not ag...
The design of a borehole field should be based on a long-term simulation of its thermal response for the intended energy loads. A well-known method to evaluate the response is based on a pre-calculated dimensionless function, the g-function. When calculating g-functions, there are two commonly used approaches for treating the boundary condition at...
Ground coupled heating and cooling systems have become very popular during the last decades in Sweden, with about 425000 small Ground Source Heat Pumps (GSHP) and 400 large Borehole Thermal Energy Storage (BTES) systems. The large installations have a total installed capacity of about 140 MW and deliver around 800 GWh of energy, out of which circa...
Ground source heat pumps are commonly used in Sweden. The dominating method of exchanging heat with the ground is by circulation of a secondary fluid through borehole heat exchangers inserted into energy wells. Due to the environmental reasons and relatively good thermophysical properties, aqueous solutions of ethanol are recommended and are common...
The design and optimization of ground source heat pump systems require the ability to accurately reproduce the dynamic thermal behavior of the system on a short-term basis, especially in a system control perspective. In this context, modelling borehole heat exchangers (BHEs) is one of the most relevant and difficult tasks. Developing a model that i...
In this paper a simplified and not fully discretized numerical model is used to simulate the performance of a non-grouted (water filled) borehole heat exchanger (BHE). The model enables simulation of the initial transient behavior of a BHE and gives transparent insight into the heat transfer mechanism acting during the startup and operation of the...
Ground-source heat pumps often use vertical boreholes to exchange heat with the ground. A transient heat transfer model has been developed for a thermal response test on a pipe-in-pipe coaxial borehole heat exchanger. The analytical model calculates the vertical temperature profiles in the fluid flowing through the pipes, which are coupled to the s...
The design of a borehole field should be based on a long-term simulation of its thermal response for specified energy loads. This response can be calculated from a pre-calculated dimensionless function, the g-function. This paper is focused on a new approach to the calculation of g-functions; in particular with a precise representation of the bound...
Circular borehole field geometries are sometimes preferred when designing borehole thermal energy storage systems, including controlled radial temperature gradients from the center and across the borehole field. A numerical model has been described in this paper in order to study the influence of connecting boreholes in radial zones with different...
A Ground Source Heat Pump system is a well-known technology used to provide space heating and cooling in residential and commercial buildings. For large energy demands, a number of boreholes, which can vary between tens and hundreds, may be required. The boreholes can be arranged in linear, square, rectangular, or any other configuration not necess...
Ground Coupled Heat Pump (GCHP) systems connected to a set of vertical ground heat exchangers require short and long term dynamic analysis of the surrounding ground for an optimal operation. The thermal response of the ground for a multiple Borehole Heat Exchanger (BHE) field can be described by proper temperature response factors or " g-functions...
Ground source heat pump systems are often coupled to the ground by circulating a fluid through vertical Borehole Heat Exchangers (BHEs). The design of a system requires estimates of the ground thermal conductivity and the borehole thermal resistance, which are usually determined by an in situ thermal response test on a completed borehole. The usual...
The design of ground source heat pump systems requires values for the ground thermal conductivity and the borehole thermal resistance. In situ thermal response tests (TRT) are often performed on vertical boreholes to determine these parameters. Most TRT analysis methods apply the mean of the inlet and outlet temperatures of the circulating fluid al...
In a distributed thermal response test, distributed temperature measurements are taken along a borehole heat exchanger during thermal response tests, allowing the determination of local ground thermal conductivities and borehole thermal resistances. In this article, the first results from six heat injection distributed thermal response tests carrie...
Different borehole heat exchanger designs have been discussed for many years. However, the U-pipe design has dominated the market, and the introduction of new designs has been practically lacking. The interest for innovation within this field is rapidly increasing and other designs are being introduced on the market. This paper presents a general s...
The mass flow rate of the secondary refrigerant flowing in the borehole heat exchanger of a ground source heat pump is an influential system parameter whose variation can influence the pumping power, efficiency of the pump, heat distribution in the borehole, heat pump heat capacity, and above all, the system Overall Coefficient Of Performance (COP)...
In a Distributed Thermal Response Test (DTRT) the ground thermal conductivity and bore-hole thermal resistance are determined at many instances along the borehole. Here, such a test is carried out at a 260 m deep water filled energy well, equipped with a U-pipe borehole heat exchanger, containing an aqueous solution of ethanol as working fluid. Dis...
![Table 3 . Total heat flow for all models [W/m]](profile/Jose-Acuna-13/publication/267428609/figure/tbl3/AS:669366442000402@1536600804668/Total-heat-flow-for-all-models-W-m_Q320.jpg)
The most common way to exchange heat with the bedrock in Ground Source Heat Pump (GSHP) applications is circulating a fluid through a U-formed closed loop in vertical boreholes drilled several tenths of meters into the ground. The quality of the heat exchange depends on the flow conditions along the channels, the pipe properties, and the relative p...
The most common way to exchange heat with the bedrock in ground source heat pump applications is circulating a secondary fluid through a closed U-pipe loop in a vertical borehole. This fluid transports the heat from the rock to the ground source heat pump evaporator. The quality of the heat exchange with the ground and the necessary pumping power t...
A research project that aims at presenting recommendations for improving the COP of ground source heat pump systems by 10-20% through better design of Borehole Heat Exchangers (BHE) is described in this paper. Experiments are carried out with temperature measurements taken in different BHE types during heat pump operation conditions as well as duri...
The thermal performance of a Borehole Heat Exchanger plays a significant role when defining the quality of heat exchange with the ground in Ground Source Heat Pumps. Different designs have been discussed and increased interest on innovation within this field has taken place during the last years. This paper presents the first measurement results fr...
Some experiences with coaxial borehole heat exchanger prototypes are discussed here. Four dif-ferent designs are described as they have been part of a research project at KTH: two pipe-in-pipe annular designs, one multi-pipe and one multi-chamber design. A special focus is given to two of the prototypes, a pipe-in-pipe design with the external flow...
Projects
Projects (4)
Measure the performance of a patented water-water heat pump and integrate the measured performance in short-term simulations of a complete system: house, buffer tank, heat pump and borehole.
The project's goal is to develop a new modeling methodology for the design and operation improvement of borehole thermal energy storage with temperatures up to 100 °C that are integrated into a district heating system.
1) Identify business opportunities related to deep BHEs,
2) Measure, document and evaluate the performance of 3 deep BHEs,
3) Build a laboratory-scale borehole thermal storage (LABS),
4) Calculate and analyze how KTH’s new heat pump system could operate at least 5% more efficiently using some coaxial BHEs within reasonable temperature limits,
5) Optimum flow in GSHP systems with deep boreholes,
6) Dissemination of knowledge,
7) Quantify the thermal influence between neighboring systems with shallow and deep boreholes,
8) Write a recommendation guide for designing deep BHEs with coaxial
collectors.
