Thermal Power Plant with Salt Energy Storage at Sicily – High Precision Foundation design for the mirror construction

Thermal Power Plant with Salt Energy Storage at Sicily – Delicate foundation design for a mirror structure with high-precision requirements

AquaSoli has supplied the foundation design for a new mirror power plant in Sicily. The foundations under the collector mirrors have to support dead weight, thermal expansion, wind and earthquake loads with tiny allowable deformations of a few millimeters (Fig. 1).


Figure 1 – Comparable Mirror Construction at preceding thermal Power Plant in Spain with AquaSoli as well in charge of the foundation engineering

This is a state-of-the-art mirror power plant with a salt storage system developed by AquaSoli’s customer FRENELL (Fig. 2), which operates on the basis of “FRENELLS Direct Molten Salt Technology”. In this technology, the molten salt serves as both heat transfer medium and storage medium.

The molten nitrate salts are heated directly in the collector field to up to 550 °C and stored in insulated tank systems. Due to the low specific costs of the tanks, their volume and salt content can be designed for up to 20 hours of full-load power generation. Due to the precise controllability and high system dynamics of the FRENELL CSP power plant design, the power plant output can be adapted to load changes in the grid within a very short time and continuous and demand-based solar power generation can be ensured around the clock.


Vergleichbare Anlage mit Salzspeicher - Comparable Plant with Salt Storage

Figure 2 – Comparable Plant including Salt Storage

The special requirement for AquaSoli is the extremely low permissible deformations of the foundations (Fig. 3) during operation of the mirrors. This is the only way to sustainably direct the sun’s rays from the high-precision adjusted collector-mirror construction precisely onto the salt solution in the collector tube.

AquaSoli and Frenell have been working together on the geotechnical tasks of these ThermoSolar power plants for about a decade. This was preceded by joint power plant projects and planning in Spain (Fig. 1), Chile and India (Fig. 2), among others.


PanoramaAufnahme der ThermoSolarBaustelle während der Tests

Bild 3 – Panoramic View of the construction site “Bilancia 1” during the execution of geotechnical Tests by AquaSoli [Photo: AquaSoli]

At the end of 2021, the financing of the FRENELL-developed CSP power plant project Bilancia 1 (Fig. 4) in Sicily could be concluded with the Swiss utility EBL (Genossenschaft Elektra Baselland) ( and Swiss Life Management ( as investors. The CSP power plant is based on FRENELL’s liquid salt-based Fresnel collector technology and has an electrical capacity of 4 MW. The integrated thermal energy storage system has a capacity of 15 full load hours. With Bilancia 1, FRENELL thus consolidates its market success of storage-based CSP power plants and has opened another chapter in the long-standing and trusting cooperation with AquaSoli (Fig. 5).

Fundamentbau für das Kraftwerk Bilancia 1 auf Sizilien [Foto: Frenell]

Bild 4 – Foundation construction for Power Plant Bilancia 1 in Sicily [Photo: Frenell]

Von AquaSoli beim Fundamentbau für das Kraftwerk Bilancia 1 auf Sizilien durchgeführte Eignungsprüfung und Qualitätssicherung [Foto: Frenell]

Bild 5 – Suitability testing and quality control carried out by AquaSoli during foundation construction for the Bilancia 1 power plant in Sicily [Foto: Frenell]

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