Scientists have developed a new mathematical model which indicates floating solar on fish farms could be a lucrative option in land-scarce Taiwan. Although floating arrays could hinder fish production, the losses would be largely compensated by electricity-related income.
Researchers from the National Taiwan University and National Chiayi University, also in Taiwan, have assessed floating PV potential on the country’s abundant fish farms.
Taiwan’s 40,000ha of aquaculture ponds could host 40 GW of solar capacity, the researchers estimated, more than twice the volume of PV capacity the government aims to deploy by 2025.
A model developed by the researchers examined floating PV as an investment option at a typical Taiwanese milkfish pond, with measurements taken at a PV-free site and at one 40% covered by a floating array during production cycles from October 2017 to April 2018 and from April to September last year.
Energy output was simulated using the PVWatts DC power model developed by the U.S. National Renewable Energy Laboratory and based on 310 W solar panels supplied by Taiwanese manufacturer URE Corp, which was known as Neo Solar at the time. The model was also tested by simulating a floating array over 60% of a pond surface.
Data suggested covering almost half a pond significantly reduced dissolved oxygen, water temperature, biochemical oxygen demand and the concentration of chlorophyll a and encouraged the presence of nitrogen and phosphorus needed for plant growth. Less dissolved oxygen meant reduced fish appetite, particularly during the day, when fish usually feed, hindering fish growth. The effect would be exaggerated if more of the pond were covered by PV panels, according to the modeled results. “Accumulated over a five-month period, these effects lead to an estimated reduction in fish production of 10% in winter and 5% in summer, under 60% [PV panel] cover”, the researchers wrote.
Based on the recently-expired feed-in tariff (FIT) of US$0.155/kW available to the PV installation used in the study, the researchers calculated pond owners could have generated US$20,150 of annual electricity revenue. Although FIT payments are now under review by the government, the proposed new rates would still more than compensate for the estimated US$1,197 in lost revenue due to stunted fish growth calculated by the study.
Using the now-expired FIT rates, the researchers said annual revenue from a pond 20% covered by a 150 kW solar array could double, while a site 40% covered by a 301 kW system could see fourfold growth. Covering a pond 60% with a 452 kW system could increase turnover fivefold.
The findings of the research were presented in the paper Mathematical modeling suggests high potential for the deployment of floating photovoltaic on fish ponds, published in Science of the Total Environment.
Source: pv magazine