The HTF tanks, continuously exposed to temperature fluctuations and varying liquid levels, experience cyclic loads that put considerable stress on their supports. The anchoring and insulation system on the tank’s sliding supports had deteriorated over time, with the following problems identified:

Deteriorated Interface

The absence of a proper bond between the cementitious grout and the sliding plates led to progressive cracking of the insulation layer.

Loose Anchor Bolts

Poor anchorage contributed to excessive movement during contraction–dilatation cycles, resulting in elevated loads on the footings.

Stress Concentration

The steel base plates were acting as stress concentrators, further exacerbating the degradation of the insulation material.

Alphatec Engineering proposed a comprehensive repair strategy to rehabilitate the interface between the grout and the sliding plates beneath the footings. The solution was designed to restore the integrity of the insulation system and ensure the tanks remain stable under cyclic loads. Key steps included:

Surface Preparation

Material Removal: Pneumatic chippers were used to remove approximately 50 mm of the degraded grout from underneath the sliding plates.

Leveling: The team ensured that the exposed concrete was healthy and level without altering the saddle’s position.

Installation of Alphapads® and Regrouting

Alphapads® Placement: Alphapads® (sized D2) were set in place and adjusted to the correct height, enabling the hydraulic levelling system to work effectively.

Epoxy Grouting: ALPHATEC® 800 epoxy grout was carefully applied to the interface between the sliding plates and the newly prepared surface beneath the footings. This process ensured that the full weight of the tank was transferred securely onto the grout.

Final Checks and Quality Assurance

A thorough inspection verified that all grouted areas were properly aligned and free from sharp edges.

The repair work was conducted on all six footings of the two parallel tanks, reinforcing the foundation for long-term stability.

Following the repair, the HTF tank footings demonstrated restored stability and improved insulation performance. The comprehensive grout restoration reduced the adverse effects of cyclic loading and minimised further degradation, ensuring that the thermal storage system continues to operate reliably. This successful intervention underscores the importance of meticulous surface preparation and precise regrouting in the renewable energy sector.

By addressing these critical issues with targeted repairs and advanced materials, Alphatec Engineering has ensured that the Andasol solar power station’s HTF tanks remain robust against temperature-induced stresses, contributing to the plant’s overall efficiency and sustainability in renewable energy production.