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.

REFERENCES

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.

We end May with our 7th General Assembly!

The GEOFIT consortium successfully held its 7th Virtual General Assembly on May 20 and 21 2021, our first GA for 2021! The meeting was organised online in two intense half-day sessions during which work package leaders where able to present the progress made with the core technologies, demonstration activities and coordination work packages.

Kicking-off our 7th meeting!

The first-day session started with a focus on the state of the art of technical work packages (WP). Lead by our colleagues from IDS Georadar, Groenholland, AIT, and Nuig Galway, we got to review WP2 which focused on-ground research, worksite inspection, and improved drilling technologies, and wrapped up its work last April 2021. The presentations for WP 3, 4, and 5 presented the different advances made with our Shallow Ground Heat Exchangers, Heat Pumps, system integration and efficiency management. After a short coffee break, we had the presentation of the progress of pilot implementation. In this sense, we were celebrating the commissioning of our first pilot site in Perugia, an important milestone for the project! Our Bordeaux pilot has also taken important steps in the past months when it comes to drilling.

The GEOFIT Team

On the second day, we were able to review the advances made on our GeoBIM platform and the standardisation, exploitation, and communication activities and R2M started an open discussion on possible business cases, UNE presented different approaches to the standardisation language including the CWA and COMET updated on the most recent events and the new website design and materials.

The meeting wrapped up with high hopes that next time we might meet again in person and with a clear view of the next steps that will be taken by all partners during the next 6 months.

Marco Calderoni elected as New Chair of the RHC-ETIP

GEOFIT project coordinator, Marco Calderoni, was elected as new chair of the RHC-ETIP, the European Technology and Innovation Platform on Renewable Heating and Cooling. His mandate started on the 1st January 2021 and will run until the end of 2021. The RHC-ETIP represents stakeholders from the biomass, geothermal, solar thermal sectors, heat pumps, district heating and cooling, thermal storage and hybrid systems. It is, therefore, a unique ETIP covering all the renewable heating and cooling technologies.

Marco Calderoni takes over for Javier Urchueguía, RHC-ETIP Chairman in 2020. As key takeaways from his presidency period, Dr.Urchueguía pointed out the influential role of the RHC-ETIP to tip the balance of the budgetary distribution towards renewable heating and cooling. During his first meeting as Chairman of the RHC-ETIP, Marco Calderoni highlighted the potential positive impact of new alliances formed in 2020, such as the one with ETIP SNET and the Clean Energy Transition Partnership.

GEOFIT is already part of their project database and is now closer to the RHC Platform that it has been so far. Thus we can indirectly contribute to their work of maximising synergies and strengthening efforts towards research, development and technological innovation of Geothermal Energy within the European Union.

You can now read the full press release from RHC-ETIP here.

On Wednesday and Thursday 4th & 5th November, We Held Our GA#6!

The GEOFIT consortium successfully held our 6th General Assembly (GA) on November 4th and 5th, 2020, hosted remotely by R2M Solution. Important progress has been carried concerning the design of the GEOFIT systems to be installed in each of our five pilots. And although we are facing some delays during this installation phase due to the COVID-19 sanitary situation, the geothermal field in the school of Sant Cugat has been completed during the summer and installation at other pilots is planned to start before the end of the year.

Drilling and civil works for the horizontal connection to the plant room in Sant Cugat pilot (AJSC)

During the two-day meeting, we discussed the progress of our work and individual Work Packages, putting special focus on the pilots’ progress. The project moves in the right direction and the work is getting more advanced.

Among the progress included in the partners’ presentations, overviews on the last decisions made regarding the Bordeaux and Galway pilots were shown by NUI GALWAY and NOBATEK, progress on the engineering design tool for ground heat exchangers was shown by GROENHOLLAND, as well as how the GeoBIM platform is being implemented by IDP in the more advanced demo-sites, Sant Cugat and Perugia.

Two workshops were also organized during the GA, the first one to discuss the life cycle approach within the project context, led by EURECAT, and the second one to start analyzing the pilot business cases and discuss why Geothermal is an appealing technology for building retrofitting, led by R2M.

The meeting closed by setting up the next steps and plans for the upcoming six months.

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

SIART and IDSGEORADAR Perform Structural Monitoring at Sant Cugat Pilot

From 27th to 31st July, SIART and IDSGEORADAR were at Sant Cugat pilot for structural monitoring, during the same week drilling works started. The goal was to perform structural monitoring before and during drilling, and see any impact in the school buildings.

IDSGEORADAR installed a Hydra-G system which monitored real-time measurements of sub-millimetric displacements in the administrative building and in the primary school. This system provides the high-accuracy and resolution radar technology. The system was accompanied by an optical and infrared HD camera providing real- time visual inspection of monitored area, draping radar data on a 3D model of the scene created using the radar system.

On the other hand, SIART installed several accelerometers in both buildings, administrative and primary school, to monitor vibrations before and during the first drilling carried out on 31st July. The goal of monitoring before drilling works is to know the building frequency, and see, once the drilling starts, if it has changed due to the vibrations propagation throughout the terrain. Once data has been captured, SIART will analyze them and present some results.

On the left: one of the accelerometers installed by SIART; On the right: Hydra-G system and camera installed by IDSGEORADAR.

Drilling Works Have Started at the Sant Cugat Pilot Site

On 31st July, Catalana De Perforacions (CDP) started the drilling works at the Sant Cugat demo site. The design of the geothermal field consists of 12 boreholes up to 120m deep and one Horizontal Directional Drilling (HDD).

Image 1: location of the 12 boreholes.

While drilling the first well, some problems with the ground material, mainly clays, and the groundwater level at depths beyond around 60 meters were faced. The borehole heat exchangers are double U PERC 100 SDR 11 PN16, with a diameter of 32mm.

On the other hand, on 3rd of August, the works related to the horizontal connection between the collection chamber and the plant room where the Ground Source Heat Pump (GSHP) will be installed, also started.

These works, including the geothermal field and the horizontal connection between the chamber and the plant room, should be completed on 31st August according to schedule.

 

Image 2: the second borehole drilled

 

Image 3: excavation of the collection chamber of the pipes coming from the 12 boreholes

 

Fourth Assembly in Bordeaux

Bienvenue a Bordeaux! The most elegant city in France! Last week we were at the Geofit 4th General Assembly where we had the chance to share all the advances achieved since the last meeting.

We managed to get into intense planning and discussing agenda, mostly related to very important issues regarding the implementation of the pilots and how the technical solutions and legal issues could be approached. 

We found out, for example, of an interesting opportunity involving the different types of soils in the five different pilot sites. Drilling on different soils are options that can be explored and harnessed for the project interests.

The assembly also dealt with technical issues that will affect the activities scheduled for the next six months.

We also visited the demo site in Talence, in the very same building where we carried out the meeting. Our host (SAED) kindly showed the space where the future Geofit installation will be placed. It was almost as being on a living lab! Technical discussions and problem solving for the heat pump installation were part of the second day too.

The weather wasn’t very inspiring but we managed to get a very clear path for the next six months and everyone left with a positive feeling facing the new work roadmap. Merci la France!

Geofit Presentation Video

Here is the first video of Geofit, a video that presents the project and launches, with its premiere, the Geofit video series, which will include interviews, updates on demo sites, and will last until the end of the project.

This video presentation of motion graphics explains the context from which the European project Geofit arises: the environmental problem and the barriers and difficulties it faces, as well as the effective and integral solutions provided by the project to overcome them. It also describes the characteristics of our geothermal retrofitting systems and our innovative tools, methods and technologies.

Finally, the video presents the pilot sites where the Geofit systems will be installed to demonstrate the results and all the countries that make up our consortium.

The video is uploaded to Geofit’s YouTube channel, so that everyone can share and help us spread the word about it!

Remember that very soon our first newsletter will be published, with more news.
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GEOFIT WORKSHOPS: Galway & Aran Islands

At the end of January we held two workshops in Ireland linked to two of our pilot sites, one located in Galway and the other in the Aran Islands. These pilot sites have different characteristics and represent different challenges for the demonstration of our project. In this post we will talk about the development of the workshops, as well as these two pilot sites, so that they can be better known.

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