Efficiency and economic analysis of utilizing latent heat from groundwater freezing in the context of borehole heat exchanger coupled ground source heat pump systems

Zheng, Tianyuan; Shao, Haibing; Schelenz, Sophie; Hein, Philipp; Vienken, Thomas; Pang, Zhonghe; Kolditz, Olaf; Nagel, Thomas

doi:10.1016/j.applthermaleng.2016.05.158

Cited by 49 publications

(14 citation statements)

References 32 publications

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“…It is aware in the community that 3D numerical simulations are often computationally expensive. Therefore, their application in the long-term performance analysis was only investigated for the sustainability of shallow U-type BHE (Hein et al 2016b;Lazzari et al 2010) and the impact of latent heat (Zheng et al 2016). Wu et al (2019) performed simulation on a new single-well circulation (SWC) groundwater heat pump system.…”

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Numerical investigation on the performance, sustainability, and efficiency of the deep borehole heat exchanger system for building heating

et al. 2019

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IntroductionWith the growing demand on renewable energy all over the world, geothermal heating and cooling is increasingly utilized by applying borehole heat exchanger (BHE) coupled ground source heat pump (GSHP) systems. One of the factors preventing the further application of GSHP system in densely populated urban areas is the limiting land surface for installing the BHEs. Therefore, deeper boreholes with a depth of 2302 m have been AbstractIn densely inhabited urban areas, deep borehole heat exchangers (DBHE) have been proposed to be integrated with the heat pump in order to utilize geothermal energy for building heating purposes. In this work, a comprehensive numerical model was constructed with the OpenGeoSys (OGS) software applying the dual-continuum approach. The model was verified against analytical solution, as well as by comparing with the integrated heat flux distribution. A series of modeling scenarios were designed and simulated in this study to perform the DBHE system analysis and to investigate the influence of pipe materials, grout thermal conductivity, geothermal gradient, soil thermal conductivity, and groundwater flow. It was found that the soil thermal conductivity is the most important parameter for the DBHE system performance. Both thermally enhanced grout and the thermally insulated inner pipe will elevate the outflow temperature of the DBHE. With an elevated geothermal gradient of 0.04 °C m −1 , the short-term sustainable specific heat extraction rate imposed on the DBHE can be increased to 150-200 W m −1 . The quantification of maximum heat extraction rate was conducted based on the modeling of 30-year-long operation scenarios. With a standard geothermal gradient of 0.03 °C m −1 , the extraction rate has to be kept below 125 W m −1 in the long-term operation. To reflect the electricity consumption by circulating pump, the coefficient of system performance (CSP) was proposed in this work to better quantify the system efficiency. With the typical pipe structure and flow rate specified in this study, it is found that the lower limit of the DBHE system is at a CSP value of 3.7. The extended numerical model presented in this study can be applied to the design and optimization of DBHE-coupled ground source heat pump systems. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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Numerical investigation on the performance, sustainability, and efficiency of the deep borehole heat exchanger system for building heating

et al. 2019

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“…• Groundwater [20][21][22] • Even from mechanical energy [23,24] • Coal process [25][26][27] The next section details the characteristics for compression and absorption heat pumps.…”

Section: Distillation -Innovative Applications and Modelingmentioning

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Energy Evaluation of the Use of an Absorption Heat Pump in Water Distillation Process

Romero¹,

Silva-Sotelo²

2017

Distillation - Innovative Applications and Modeling

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It is impossible to transform the whole energy into useful work. It is impossible to increase the processes of cultivation of foods without water. It is impossible to separate all ions and minerals from water. Most of the real processes are thermodynamically irreversible. Calculations may indicate the fraction of efficiency of a thermal process. All the above mentioned facts have led to some proposals of cycles that exchange energy in order to produce a useful effect for the society. The key sustainable related parts are: to obtain water free of minerals or ions by distillation process. In this chapter, thermodynamic cycles will be explained for distillation using thermodynamic cycles of thermal machines called absorption heat pumps (AHPs). Distillation process offers to the AHPs an opportunity to diminish the consumptions of fossil fuels. The AHPs are able to work with 2% of mechanical energy to carry out a sustainable distillation process. Most of the energy of an absorption heat pump operation is thermal energy. The operation of the AHPs are defined with the coefficient of performance (COP); the variations of this parameter are shown as function of the different scenarios to obtain sustainable distilled water.

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“…Therefore, the thermal convection of the groundwater flow could impact the results calculated by the LSM [12]. Hence, many studies are recommended to perform multi TRTs at different places with different groundwater flow velocities, to assure accurate calculations of the soil properties and borehole thermal resistance [13][14][15][16][17][18][19][20][21].…”

Section: Introductionmentioning

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The Effect of Groundwater Flow on the Thermal Performance of a Novel Borehole Heat Exchanger for Ground Source Heat Pump Systems: Small Scale Experiments and Numerical Simulation

et al. 2020

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New small-scale experiments are carried out to study the effect of groundwater flow on the thermal performance of water ground heat exchangers for ground source heat pump systems. Four heat exchanger configurations are investigated; single U-tube with circular cross-section (SUC), single U-tube with an oval cross-section (SUO), single U-tube with circular cross-section and single spacer with circular cross-section (SUC + SSC) and single U-tube with an oval cross-section and single spacer with circular cross-section (SUO + SSC). The soil temperature distributions along the horizontal and vertical axis are measured and recorded simultaneously with measuring the electrical energy injected into the fluid, and the borehole wall temperature is measured as well; consequently, the borehole thermal resistance (Rb) is calculated. Moreover, two dimensional and steady-state CFD simulations are validated against the experimental measurements at the groundwater velocity of 1000 m/year with an average error of 3%. Under saturated conditions without groundwater flow effect; using a spacer with SUC decreases the Rb by 13% from 0.15 m·K/W to 0.13 m·K/W, also using a spacer with the SUO decreases the Rb by 9% from 0.11 m·K/W to 0.1 m·K/W. In addition, the oval cross-section with spacer SUO + SSC decreases the Rb by 33% compared with SUC. Under the effect of groundwater flow of 1000 m/year; Rb of the SUC, SUO, SUC + SSC and SUO + SSC cases decrease by 15.5%, 12.3%, 6.1% and 4%, respectively, compared with the saturated condition.

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Efficiency and economic analysis of utilizing latent heat from groundwater freezing in the context of borehole heat exchanger coupled ground source heat pump systems

Cited by 49 publications

References 32 publications

Numerical investigation on the performance, sustainability, and efficiency of the deep borehole heat exchanger system for building heating

Numerical investigation on the performance, sustainability, and efficiency of the deep borehole heat exchanger system for building heating

Energy Evaluation of the Use of an Absorption Heat Pump in Water Distillation Process

The Effect of Groundwater Flow on the Thermal Performance of a Novel Borehole Heat Exchanger for Ground Source Heat Pump Systems: Small Scale Experiments and Numerical Simulation

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