Construction of a Pit Thermal Energy Storage pond via Solmax

By Solmax – What does the next generation of Pit Thermal Energy Storage (PTES) look like? This question is the focus of the Efficient Pit research and development project funded by the German Federal Ministry for Economic Affairs and Energy via a resolution by the German Bundestag. Over the project’s four-year duration, project participants Solmax Geosynthetics GmbH and Solites, a division of Steinbeis Innovation GmbH, are dedicating themselves to the overall goal of further developing PTES in such a way that they can permanently meet the requirements of the German and European heating sector – paving the way for a successful heating transition. Solmax is contributing its expertise in the field of materials and construction methods, while Solites is focusing on research and development.


In the Efficient Pit project, materials and designs are to be developed that remain permanently stable at storage temperatures of up to 95° C (203° F). Another objective is to ensure that the geosynthetic system solutions can meet the high demands placed on pit thermal energy storage projects in terms of impermeability and durability at high operating temperatures and the resistance and robustness of their coverings to UV radiation and weathering. Working together, the project participants are investigating solutions for cost-effective, durable construction methods as well as operational control of the heat storage’s sealing and insulating function. An expansion of simulation models and design tools to support the industry are also part of the project. Among other things, a modular system for different storage sizes is to be developed.

The project participants are planning to build a test PTES at Solmax’s production site in Rechlin where they test the refined materials, designs and functionalities under real conditions. Aside from laboratory tests on the stability and aging of the temperature-resistant geosynthetics, a focus is also placed on the further development of new system components. In addition, installation teams can optimize the handling, assembly and welding of different products and installation parts in its storage laboratory and develop repair options under real conditions.

Construction of a Pit Thermal Energy Storage pond via Solmax

With the aid of its own installation teams, Solmax has been building pit thermal energy storage systems worldwide for several years, using geosynthetic products such as Solmax High-Temperature Liner. By seasonally storing larger amounts of thermal energy, they are a cost-efficient and effective solution. Using PTES, heat generation from renewable energies and industrial processes can be exploited all year round.

With the launch of its Efficient Pit project in September 2021, the company is emphasizing its commitment to environmental protection and is making a significant and active contribution to a climate-friendly future.

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