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Scientists from the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) in Germany and Tarbiat Modares University (TMU) in Iran have built a system that can reduce electricity costs in aquaculture. It consists of an open-channel pond, a mechanical paddle wheel, a motor and power transmission system, a motor speed control circuit, a 100 W photovoltaic module and a 12 V battery with a capacity of 60 Ah, an inverter and a 10 A charge controller.
Scientists at the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) in Germany and Tarbiat Modares University (TMU) in Iran have designed a photovoltaic system for the co-production of microalgae and electricity.
They explained that aquaculture facilities typically have high electricity costs, accounting for approximately 40% of their total energy costs, and that around 0.5% of global greenhouse gas emissions are attributable to aquaculture. “Microalgae cultivation in open pond systems, when integrated with photovoltaic technology, can improve energy efficiency and reduce water evaporation, further aligning aquaculture practices with climate change mitigation goals,” they stressed.
The research group described the proposed technology as a “small aquavoltaic” system composed of an open channel pond, a mechanical paddle wheel, a motor and power transmission system, a motor speed control circuit, a 100 W photovoltaic module, and a 12 V battery with a capacity of 60 Ah, an inverter, and a 10 A charge controller.
The key element of the system, the polyethylene channel pond, was designed with an open design to allow access to sunlight and air. Typically, these ponds have a shallow design to reduce evaporation and contamination, as well as to promote continuous water circulation.
The academics set the optimal water depth for microalgae production in the pond at 0.3 m. “By controlling this specific water depth together with other parameters such as rotation speed and reaction time, it is possible to create favourable conditions for both microalgae production and electricity generation in the aquavoltaic system,” they further explained.
The system performance was evaluated through a series of experimental tests carried out from 9 to 15 May, under different meteorological conditions. The main parameters were solar radiation, air temperature and wind speed.
The analysis showed that shading caused by the solar panel has a “significant” impact on temperature control and pH range in the microalgae production pond. Nevertheless, the module was able to cover approximately 98.6% of the annual electricity demand of the aquaculture facility.
The team also conducted a techno-economic analysis of a system hosting the cultivation of Spirulina, a blue-green algae containing vitamins, minerals, antioxidants and proteins, and found that it was able to achieve 7% lower electricity costs compared to a reference system powered by grid electricity.
“The cost of spirulina produced with the aquavoltaic system in the fifth year was calculated at 0.4975 USD/g at a 10% interest rate and 0.331 USD/g at a 10% interest rate,” the scientists noted. “In addition, the cost per litre of spirulina produced with the aquavoltaic system was calculated at 0.7133 USD/g.”
Details of the system can be found in the article « Development and experimental performance evaluation of a small-scale aquavoltaic system for microalgae production », published in Results in Engineering . «The present study highlights that aquavoltaics could have the potential to further increase microalgae production and thus reduce production costs,» the researchers conclude. |
