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Advanced materials and processes to improve performance and cost-efficiency of Shallow Geothermal systems and Underground Thermal Storage

Periodic Reporting for period 3 - GEOCOND (Advanced materials and processes to improve performance and cost-efficiency of Shallow Geothermal systems and Underground Thermal Storage)

Reporting period: 2019-11-01 to 2021-02-28

Buildings hold a large untapped potential for renewables and energy efficiency in order to decarbonise the EU economy, to ensure security of supply and to provide cost savings to EU households and businesses alike. In this context, Shallow Geothermal Energy Systems (SGES) are a stable, reliable and renewable energy source with some key features compared to many other Renewable Energy Sources (RES): being available everywhere and being capable of providing not only heating, but also cooling with unparalleled efficiency. But there is still a need to remove market barriers and gain competitiveness, but also to develop the next generation of geothermal systems with new materials for penetrating further the market of building construction and renovation.
By a smart combination of different material solutions under the umbrella of sophisticated engineering, optimization, testing and on-site validation, GEOCOND project worked on developing solutions to increase the thermal performance of SGES. The overall objective is a reduction of the total costs of a geothermal installation by about 25%, which means a substantial increase in competitiveness.
Objectives of the project could be shortly resumed as follow:
1.- Geothermal pipes improvement of thermomechanical ageing resistance and surface properties.
• High thermal Conductive HDPE pipes and fitting elements.
• New pipes configuration based on the use of pipes with different thermal conductivities.
2.- New additives for grouting.
• New additives for grouting.
• Phase Change Materials (PCMs) with various range in the transition temperatures.
3.- Tailor-made performance grouting.
• High thermal conductivity grout for BHE applications
• Moderate thermal conductivity grout with PCM for BTES applications
4.- Optimize efficiency and minimize costs.
Different test fields (Spain, Sweden and Germany) are aimed to demonstrate upscaling of material production from lab scale to full size, and to confirm the efficiency improvements in real application of the new products developed within the project.
GEOCOND project began in May 2017 and the first steps were aimed at achieving the optimal specifications of the new products to be developed. New plastic pipes have been developed showing a balance between process ability, thermal conductivity (high and low) and mechanical performance. Development of PCMs included modification of existing formulations and adaptation of manufacturing equipment. Experimental batches were produced for incorporation in the grouts. New hybrid additives have been developed in order to increase the compatibility with the grout constituents and also enhance the thermal conductivity of grouts.
In March 2019, the production of new developed materials (plastic pipes and grout) was upscaled, firstly for the shallow test field at UPV (<15 m depth). With material on site in Valencia in October 2019 drilling and installation could begin, the test field was operational in February 2020, and the tests were carried out until June 2020, with evaluation of the data going on further. The results confirmed the expectations from the lab tests, in particular the improved heat exchange efficiency. Production of material was further upscaled in the first half of 2020 for the full-size installations in Germany and Sweden, with the installation of a 50-m-deep BHE at Borås in Sweden ready in June 2020 and the subsequent thermal tests for PCM-grout running until August 2020. Material for the BHE of 100 m depth in Germany was ready in August 2020, and BHE could be installed at two different sites. The installation at full scale showed good handling properties of the materials, and the TRTs carried out at these BHE (until the very end of the project in February 2021) confirmed the improved efficiency.
Sustainability was validated by assessing environmental, cost and social impacts using GEOCOND’s pipes and grouting. Main contributions to all impacts were ascribed to the electricity consumption and the heat pumps needed. The single U configuration borehole using GEOCOND’s pipes and grouting proved to be the most sustainable solution.
A large number of articles in high impact scientific journals and international conferences have been released promoting the dissemination of the project results. Dissemination materials are available to the public to have a better understanding of the different GEOCOND´s undertakings. The e-learning materials represent the legacy of GEOCOND project’s outcomes whereby the technological developments have the ability to instigate extensive business impacts, across the shallow geothermal sector. Four practical courses were carried out where some of the submodules were presented. All this information has been carefully compiled on an online repository, which we hope is going to be highly educative (for further details, please visit the Project Activities section at GEOCOND´s website).
In terms of exploitation, there is a clear business case for the GEOCOND project and for the future deployment of its solutions to the industry. Several of the enhancements that have been produced during the project have a clear potential to thrive on the market of the shallow geothermal systems due to their proven performance in real environments as shown during the project.
GEOCOND project has increased the percentages of different conductive particles in geothermal plastic pipes to obtain enhanced thermal conductivity (at least 1.4 W/mK) and to improve the ageing of the current pipes. New developed conductive pipes showed thermal conductivities 2.5-3 times standard PE100. Production costs estimated for high conductive and low conductive pipes are viable considering the benefits idenfied when used in different geothermal configurations.
Novel PCMs for use in shallow geothermal energy systems has been developed and successfully incorporated within grouts in particulate form. In order to obtain cost-competitive, improved thermal and low viscosity grout formulations, hybrid additives have been synthesized. These innovative additives enhance the thermal conductivity of grout in the range of 2.0 to 3.0 W/m K.
The new GEOCOND developed materials offer an improved heat exchange efficiency for borehole heat exchangers (BHE). A reduction of the borehole thermal resistance of >20% compared to the current state of the art could be confirmed in the field, allowing for the reduction of BHE length by about 10% without losing overall efficiency. The possibility to include PCM directly into the grout also could be demonstrated, with improvment in storage efficiency expected.
The use of more thermally conductive materials developed along the GEOCOND project for the pipes and grouting will reduce the overall costs, environmental impacts and social footprint of the whole shallow geothermal facility.
The GEOCOND outcomes will increase the competitiveness of the European geothermal and pipe industry and SMEs by promoting innovative and high performance products to favour market opportunities for new developments of materials and products. Future actions for evaluating the products in real applications are planned for the next future. In those case, new installations outside the framework of the project will be selected where the final validation of our enhancements will be corroborated, and the process of intellectual protection and marketing of the products developed within the project is currently being undertaken.
Kick-off meeting
M7 plenary meeting