Model development and performance analysis of Novel Shallow Ground Heat Exchangers

by Henk Witte – Groenholland

One of the key aspects of the EU GEOFIT project is the development of integrated engineering design tools for different types of ground heat exchangers. This toolkit provides design methodologies for vertical borehole heat exchangers, shallow horizontal and slinky type heat exchangers, and earth basket (spiral) heat exchangers.

Ground heat exchangers (GHEX) are used to provide a heat source or heat sink used for heating or cooling a building. They are typically constructed of plastic pipes installed in different configurations in the ground. A fluid is circulated in the pipes and the GHEX extracts heat from the ground (heating operation) or rejects heat to the ground (cooling operation).

For the validation of the analytical solutions used in the integrated engineering design toolkit, especially the new finite line source solutions developed for earth basket (spiral) heat exchangers laboratory experiments (figure 1) and detailed numerical simulations (figure 2) have been performed.

Figure 1. Experimental sandbox setup for earth basket (spiral) heat exchanger characterisation (foto: AIT)

The performance of a ground heat exchanger can be summarized to two key parameters:

  1. Pressure drop: A measure of the pump energy needed to move the fluid through the heat exchanger.
  2. Thermal resistance between fluid and ground: A measure of the thermal performance of the GHEX.
Figure 2. CFD simulation of earth basket (spiral) heat exchanger (foto: AIT).

The goal of the performance analysis is to identify key-design parameters affecting the overall system performance. Parameters investigated include:

  • Diameter of the earth basket (spiral) heat exchanger
  • Pipe diameter in relation to flow rate and pressure drop
  • Distance between adjacent rings in relation to total length and buried depth
  • Soil thermal parameters

Evaluation of the results of the performance analysis should take into account the actual effect on system performance. As an example, it can be attempted to reduce the thermal resistance in all cases as much as possible. However, the effect on performance is related to the actual heat rate of the system (figure 3). It is clear that with a low heat rate (5 W/m) the thermal resistance can be allowed to be high without affecting performance. These results will have implications for operating these systems during part-load conditions, which is important in view of the application of frequency-controlled compressors in the heat pumps. In this way, the results of the GEOFIT project not only provide designers with the tools to evaluate different types of ground heat exchangers in one integrated tool but also allows optimization of actual system operational control.

Figure 3. Relation between thermal resistance (fluid to ground) and energy performance degradation for different specific heat rates.


Meeng, C.L (2020). Development of an engineering tool for the design of novel shallow ground heat exchangers – GEOFIT. MSc Thesis TU Eindhoven.

Dörr, C.J. (2020). CFD Analysis of Ground Heat Exchangers. MSc Thesis Montan Universität Leoben, Austrian Institute of Technology.

Kling, S. (2020). Experimental characterization of Helix-Type Ground Source Heat Exchangers Configurations for Developing a Standardized Design Tool. MSc Thesis FH Burgenland University of Applied Sciences, Austrian Institute of Technology.

GEOFIT at Sustainable Places 2020

On Day 3 of the 4-day virtual Sustainable Places 2020 (SP2020) conference, Thursday 29th October from 14.00 – 17.00 CET, Marco Calderoni from GEOFIT contributed to the “Renewable Heating and Cooling Solutions for Buildings and Industry Workshop”, and the presentations and video recordings are publicly accessible.

Banner for “Renewable Heating and cooling solutions for Buidlings and Industry” at SP2020

The workshop brought together a selection of H2020 EU-funded projects involving experts from the biomass, geothermal, solar thermal and heat pump sectors to discuss a common strategy for increasing the use of renewable energy technologies for heating and cooling for buildings and industry. Renewable energy technologies for heating and cooling are safe, clean, efficient and increasingly cost-competitive. The workshop comprised four thematic sessions, namely “RHC for industrial applications”, “Storage solutions for RHC support in buildings”, “Innovative solutions for RHC deployment in buildings”, and finally the one that GEOFIT presented in called “Demonstration actions for RHC in buildings”.

Marco Calderoni from R2M Solution presented the GEOFIT project and highlighted first lessons learnt based on experience at the five demonstration sites.

R2M Solution organizes the annual international Sustainable Places conference, and the recent 8th as usual focused on the built environment at building, district, and urban scales to include our transport and energy infrastructures. Renowned for showcasing results coming out of the EU Horizon 2020 Framework Programme via the participation of cutting-edge research and innovation projects, the scope of Sustainable Places is captured directly in its name. It involves designing, building and retrofitting the places we live and work in a more sustainable way.

A GEOFIT poster was also displayed in the virtual room of Sustainable Places 2020.

Participating projects wereSWS-Heating – HYBUILD – CREATE – TRI-HP – HYCOOL – SHIP2FAIR – SUNHORIZON – Heat4Cool – GEOFIT – SCORES – Innova microSolar – Hybrid BioVGE – RES4BUILD – SolBioRev – FRIENDSHIP

Chair of the workshop: Andrea Frazzica (CNR ITAE) – partner of GEOFIT

Control Solutions for Air-conditioning, Refrigeration and Heating & Energy Efficiency

Control solutions for air-conditioning, refrigeration and heating & energy efficiency

Article by Raul Simonetti from CAREL

From a control point of view, the energy efficiency opportunities can be grouped into three approaches:
1. Product-level approach
2. System-level approach
3. Supervision and IoT

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