Standardisation and prefabrication of solar thermal systems remains key to the delivery of high quality, cost-optimised solutions. Solar pumping and refilling stations attached to and insulated with the storage tank have already been standard in residential systems in Central Europe. Current developments from German system supplier Aschoff Solar and Belgium system supplier Sunoptimo show that prefabricated solutions are also possible for large-scale, commercial systems between 50 m² and 2,000 m² of collector area. Both companies use containers equipped with a storage tank and all other hydraulic components. The photo shows the most current installation of Aschoff Solar at the Severin Sea Lodge in Mombasa, Kenya. The 260 m² vacuum tube installation on the roof provides hot water for the guest and staff lodges, with one container including the storage tank and the hydraulic.
Photos: Aschoff Solar
“Mombasa has already been the fifth large solar thermal system that we realised with insulated containers,” explains Carsten Aschoff, Managing Partner of Aschoff Solar. The other projects were in Thailand, Kenya and in Germany. “Prefabrication saves us around one to two weeks of hydraulic work onsite, meaning costs of around EUR 5,000. Container solutions make sense if we have a turnkey contract and storage tanks are part of the delivery.” In addition to the tank, the container houses solar stations, heat exchangers connecting to the client system´s pipes, security devices, controllers and monitoring units. The hydraulic unit is module-based – standardised hydraulic solutions of 200 m² of collector area each are combined for it. “Above 600 m², a second container is needed,” confirms Aschoff, who pre-checks all hydraulic units before having the containers shipped. The largest system was the ECCO tannery in Thailand: three containers and 1,890 m² of collector area.
Opticube with a 95 m² collector field: Easy to install, even by the client’s technical staff
Standardised installation by technical team of client
Opticube is the name of the new standardised drainback solar thermal system for larger installations of up to 300 m². It was launched by Sunoptimo in December 2015. A 20-foot container will immediately be ready to be plugged into the circuit for utilisation. The plumbing work, the filling of the drainback unit and the electric wiring to the controller are all done at the Sunoptimo factory in Assesse, Belgium, before delivery of the container. The container includes a storage tank of 1,500 to 9,000 litres, depending on the size of the system. “We wanted to reduce complexity and costs,” Bertrand Fontaine, Managing Director of Sunoptimo, explains the major targets for the new development. “For a 150 m² installation, we estimate a total cost reduction of at least 33 % without compromising on quality or component performance.”
Sunoptimo searches for partners to market Opticube across different countries. “Thanks to the simplicity of Opticube standard solar partners may be interested with this new concept to help them install large systems in a short time, but new partners with less expertise may also be interested”, adds Fontaine. According to the manufacturer, the installation can be done in two ways: Either the partners install the system on their own or they inspect and commission a system that has been installed by the technical team of the end customer, which could be a hotel or a housing company.
The galvanised steel support structure has been designed for typical 2.65 m² flat plate collectors. “We are not convinced of the advantages of vacuum tube collectors,” explains Fontaine. “Additionally, the Opticube is based on drainback, making it impossible to work with certain types of vacuum tube collectors.” Sunoptimo gives a 10-year warranty on its collectors and the structure, which is tested under heavy wind loads.
Opticube is available in 34 different combinations, with collector sizes of between 30 and 300 m² and storage tanks holding between 1,500 and 9,000 litres. Solutions above 300 m² can either be realised by combining several Opticube systems or by using a so called split container, which includes only the solar station and the heat exchangers to enable the connection of larger collector fields to existing heat storage tanks.