World’s largest pit thermal storage in Vojens
In Vojens, Denmark, a 200,000 m³ pit thermal storage basin stores surplus solar heat from a 70,000 m² collector field. Using Solmax geosynthetics, the system reduces CO₂ emissions by 6,000 tons annually.

A North American client managing a highly toxic wastewater pond system spanning several hundred acres required a containment solution that would completely isolate hazardous material from the environment. In addition to a full geosynthetic lining system, the project called for custom-fabricated liner penetration boxes – critical components that seal and secure pipe entry points through the liner, ensuring a fully testable, leak-proof barrier.
These components demanded precise engineering and fabrication expertise, particularly given the complex geometries and strict compliance standards involved. The client required a partner with deep experience in HDPE custom fabrication, capable of meeting both technical and schedule demands without compromise.
The challenge lay in fabricating large, high-specification liner penetration boxes from 25 mm to 50 mm thick HDPE plate, within a tight two-month window. The boxes had to meet stringent requirements for fit, sealing capability, chemical resistance, and long-term durability. They also needed to integrate seamlessly with the geosynthetic liner system to prevent any risk of leakage at pipe transition points.
The project demanded close coordination between engineers, material suppliers, fabricators, and installation teams to ensure the solution would perform as designed and pass integrity testing on-site.
Solmax’s Houston fabrication team specialize in solving geosynthetic challenges with custom solutions. Drawing on its experience with high-precision HDPE manufacturing, the team collaborated with stakeholders across disciplines to deliver custom liner penetration boxes within the required timeframe. The boxes were fabricated to exacting standards and delivered in time for concurrent installation with the liner system.
Each unit was built from thick HDPE plate, shaped and sealed to maintain structural integrity under field conditions and high chemical loads. The final design enabled straightforward field integration and long-term leak protection at each pipe interface.
The installed boxes are functioning as intended, forming a critical barrier against contamination and supporting the client’s mandate to protect the surrounding environment. The client expressed strong satisfaction with the fabrication quality, timeliness, and Solmax’s collaborative approach.
This project demonstrates Solmax’s ability to deliver custom-engineered containment components on schedule and to specification, even under demanding technical conditions.
The boxes were made from 25 mm to 50 mm (1 to 2 inches) thick HDPE plate.

They were completed within a two-month deadline to align with liner installation.
World’s largest pit thermal storage in Vojens
In Vojens, Denmark, a 200,000 m³ pit thermal storage basin stores surplus solar heat from a 70,000 m² collector field. Using Solmax geosynthetics, the system reduces CO₂ emissions by 6,000 tons annually.
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