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

Reporting period: 2018-11-01 to 2019-10-31

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 RES: being available everywhere and being capable of providing not only heating, but also cooling with unparalleled efficiency.

Against this background, 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 will develop solutions to increase the thermal performance of the different subsystems configuring an SGES and UTES. An overall cost reduction of about 25% is the overall aim, leading to a substantial gain in competitiveness. GEOCOND, with a unique consortium of Companies and leading Reseach Institutions in the area of SGES and Materials, will focus on four key development areas in a synergeic and system-wide approach: development of new pipe materials, advanced grouting additives and concepts, advanced Phase Change Materials and system-wide simulation and optimization.

The project results will presumably trigger a significant enhancement of the performance of the SGES, then subsequently, the society and the end users may be beneficied by the advances produced in the technologies. In general terms, the world-wide use of SGES will reduce the total emissions associated to H&C, increase the production of renewable energy sources and decrease the dependency of fossil fuels for H&C purposes.

Objectives of the project could be shortly resumed as follow:
Improved thermomechanical ageing resistance and surface properties
1.-Geothermal pipes improved (at least 15%) thermomechanical ageing resistance and surface properties (external layer good adhesion to grout and internal low flow resistance).
• HDPE pipes
High thermal Conductive HDPE pipes and fitting elements.

• New pipes configuration
New pipes configuration based on the use of pipes with different thermal conductivities and diameters.

2.- New additive for grouting
• New additive for grouting: Low cost structures based on chemical bondings of silica (quartz) and thermal conductive carbonous particles.

• New additive for grouting: Shape Stable Phase Change Materials (SS PCMs) with low tran-sition temperatures (30-35ºC) for heat storage at DHC

3.- Tailor-made performance grouting
Tailor-made performance grouting and thermal soil enhancement technologies (TSE).

4.- Optimize efficiency and minimize costs
Material Selection Support System within an engineering methodology to optimize efficiency and minimize costs.
Project development began in May 2017 and some initial results have been already achieved. The optimal specifications of the new products have been developed. Single-U geothermal heat exchanger with improved thermal conductivity, different grouting mixtures with optimized thermal conductivity and new geometry geothermal heat exchanger have been developed. All these new products have been installed in the Valencia testfield to verify their improved performance. All new results achieved so far have been disseminated and published in different journals, mainly at the European Geothermal Congress.
Different research lines in innovative solutions for SGES are tackled in the project. In consequence, the expected progresses beyond the state of the art are here presented for each of those main lines:

Beyond of the State of the art, GEOCOND project aims to increase the percentages of different conductive particles (up to 12% w/w) using our previous knowledge in dispersion and extrusion processing composites to obtain a polyolefin pipe and fittings with high thermal conductivity (at least 1.4 W/mK) and improving the ageing of the current pipes. Cost will be no more 20% higher than current geothermal pipes. To avoid re-agglomerations of carbon particles, GEOCOND aims to produce co-extruded multilayer pipes that permit to work in thin individual layers.

Beyond of the state of the art, GEOCOND project will analyse those previous studies to combine the positive experiences and produce an optimal design of the close-loop geometry taking into account the added value and experience supplied by the partners involved in the proposal. Using the different pipes developed with customized thermal conductivity (from 0.1 (insulating) to 1.4 W/mK (highly conductive)), several aspects as for instance the diameter of the pipes, the integration of separators the combined design of geometries (coaxial geometries), will be considered in our research with the goal of theoretically infer the most suitable configuration. At the same time, a key aspect as it is the easy workability during the installation stage will be always kept in mind as it could trigger itself a significant benefit for the installations.

Beyond of the state of art, GEOCOND project aims to produce a vast range of thermally enhanced bentonite products to have the same thermal conductivity of the ground. The research on new materials to be introduced into the admixtures such sand, vegetal silica, expanded or microsized graphite, construction and demolition waste15 (CDW),..as well as the possibilities of producing binders between silica and graphite will be done and the range of thermal conductivity will be between 1.5 to at least 3.0 W/m K. Additionally, a second research field will be focused on the forced injection of the conductive grouting into the surrounding soil in areas where the thermal properties of the ground are poor. In this field, we aim to investigate the mechanical behaviour of the ground and the possibilities of producing a forced injection of the grouting materials conceptually stimulation. Past experience has proven that applying dynamic pressure during grouting, adjusted to the properties of the ground increases grouting depth and quality. Functionalized silica will also develop (see section 1.4.4) to reduce carbon amount to achieve good conductivity and low grout viscosity. GEOCOND will trigger the optimization of the heat exchange conditions between the heat exchangers and the ground, which will subsequently produce a reduction of the total length of the borehole field (CAPEX) maintaining the other requirements of the grouting and in compliance with recommendations and standards

Beyond of the current state of the art, GEOCOND will increase the competitiveness of the European geothermal and pipe industry and SME’s by promoting innovative and high performance products to favour market opportunities for new developments of materials and products. A preliminary market analysis carried out within the GEOCOND consortium has shown that there are many exploitation opportunities. During the project and based on the performance of developed materials and products a more comprehensive market analysis will be carried out to provide a clear business case for the future deployment of the solutions in industry. Exploitation routes will be defined and Partners sole/joint ownership agreed before the end of the project.
Kick-off meeting
M7 plenary meeting