Proven reliability of concentrating collectors in coastal and dusty conditions

The long-term operation of the concentrating collectors at the fruit juice factory Kean Softdrinks in Cyprus has shown that this technology can reliably supply steam even in dusty environments and near the sea. Since commissioning in 2018, the plant has operated without any major failures. Routine mirror cleaning has been the only maintenance measure required to ensure consistently high performance. These findings have been independently confirmed through a comprehensive evaluation of the plant’s monitoring data of the year 2024 conducted by the German consulting firm Solar-Experience and the research institute Fraunhofer ISE. The work was supported by the German research project ProSolNet.
Photo: Kean Softdrinks

“The evaluation of the 2024 monitoring has shown that the solar system at Kean Softdrinks delivers the targeted high temperatures of around 300 °C even after six years of operation”, confirmed Stefan Abrecht, Managing Director of Solar-Experience, Germany. “With regular cleaning of the mirrors, the achievable system efficiency of the solar field is 48.4 %.”

The two rows of parabolic trough collectors are installed only a few hundred metres from the sea and are therefore continuously exposed to salty air. Moreover, Cypriot summers are typically dry and prone to high dust levels due to extended periods without rainfall. As a result, the mirrors must be cleaned approximately every ten days to maintain optimal efficiency, as confirmed by the monitoring analysis.

Monitoring results confirm reliable operation

The parabolic trough field was installed 2018 by the German project developer and parabolic trough manufacturer Protarget. After six years of operation the monitoring data was now analysed. In 2024, the factory operated for juice production on 190 days. The site benefits from a high annual direct solar irradiation of 1,949 kWh/m², of which 868 kWh/m² were available in the collector plane for solar steam generation during the factory’s operating hours.
The analysis shows a specific annual yield of 370 kWh/ m²*a, corresponding to a system efficiency of 42.6 % based on the available irradiation of 868 kWh/m2. With more regular cleaning at ten-day intervals and a minor adjustment of the control settings an improvement to 420 kWh/m²*a and an system efficiency of 48.4 % can be expected, according to the independent experts.

Schema of the solar process heat plant at the juice factory Kean Softdrinks in Limassol, Cyprus. Source: ProSolNetz

Solar process heat integration with concrete solid-state storage

The parabolic trough system, with a collector area of 279 m² (175 kW), generates thermal oil at temperatures ranging from 285 to 330 °C. The heat transfer fluid, Helisol XA, is subsequently used in a steam drum to produce steam, which is fed into the factory’s steam network operating at approximately 184 °C. The valve connecting the steam drum to the factory’s steam network – otherwise supplied by fossil-fueled boilers – remains continuously open whenever sufficient pressure is available in the steam drum to enable steam injection into the plant’s energy grid.

The generated steam is utilized in two main processes: juice pasteurization and plastic bottle inflation. To reduce transportation costs, plastic bottles are delivered in compressed form and subsequently expanded on site using hot air.

In addition to the parabolic trough field, a key component of the plant is the integrated concrete thermal energy storage system. This system consists of two modules and can reach temperatures of up to 380 °C. Both the thermal storage unit and the steam drum are compactly installed within shipping containers. The integration of thermal energy storage enables flexible steam production, allowing operation to continue even after sunset.

Websites of organisations mentioned in this news article:
Kean Softdrinks: https://kean.com.cy/
ProSolNetz: https://www.solarwirtschaft.de/unsere-themen/csp/prosolnetz/
Solar-Experience: https://www.linkedin.com/in/stefan-abrecht-22884511b/
Fraunhofer ISE: https://www.ise.fraunhofer.de/en.html
Protarget: https://protarget-ag.com/