Floating photovoltaic (FPV) systems, which consist of a single or multiple photovoltaic (PV) modules mounted on a buoyant platform, are generally designed to be arranged as an array on the surface of a closed body of water such as an inland lake or pond. However, there is now growing interest to take this technology to the sea.
For countries that have land constraints, FPV systems are a viable path to developing a domestic solar market. They do not compete for land with other uses, and the aquatic environment offers benefits that can boost PV modules’ performance. One specific advantage is that the abundantly available water can be used to keep the modules cool, thus improving their conversion efficiency. Moreover, FPV systems that are deployed over surfaces of ponds, lakes, and reservoirs fulfill other environmental engineering functions such as reducing evaporative loss and inhibit eutrophication. On the whole, FPV systems are now widely recognized to have the potential to achieve other objectives besides facilitating the transition to carbon-free energies. And as a result, installations of FPV systems have also been rising over the recent years.
The vastness of the seas and oceans provides the impetus for moving FPV systems offshore, as more space for deployment will lead to greater generation capacity. In July, a European consortium composed of several engineering firms (Tractebel, DEME, and Jan De Nul Group), a solar developer (Soltech), and Ghent University announced a plan to set up a renewable energy project in the marine environment. The consortium has stated that this multi-purpose project will combine FPV systems, offshore wind turbines, and an aquaculture facility.
Similar projects are also being considered or under development in other parts of the world. In May, the Singapore Times reported that a local solar developer Sunseap Group is in the process of building a 5MW floating solar power plant along the Strait of Johor. This project, which aims to be the first its kind in the world, is scheduled to be completed by the end of this year. DEWA, the state-run utility and infrastructure company of the UAE, has expressed strong interest in deploying FPV systems on the waters of the Persian Gulf. In June, DEWA formally issued a request for proposal for the appointment of consultants to examine the feasibility of such venture.
Advances in the development of FPV systems for the marine environment have been driven by a niche group of solar technology companies. For example, Swimsol, an Austrian company operating in the Maldives, designs and manufactures PV modules specifically for this application area. Several other research agencies and green energy startups have also been drawing up plans for the large-scale installation of FPV systems along the coastal areas or in the open seas.
Among nations, the Netherlands has been a leading advocate of offshore solar. The country’s research institutions, renewable energy developers, and private enterprises have been collaborating with each other since 2018 to develop marine solar projects. They include Oceans of Energy, the Energy Research Center of the Netherlands, and Utrecht University. Oceans of Energy is currently constructing a floating solar power plant located 15km off the shores of Scheveningen. The company aims to have this project connected to the grid by 2020.
Oceans of Energy estimates that FPV systems situated offshore can generate as much as 15% more power compared with ground-based PV systems. According to Swimsol, the additional gain in power yield is around 5-10% versus rooftop PV systems.
Although offshore solar offers many advantages such as higher generation and no land occupancy, this approach also presents some serious challenges. The marine environment contains many hazards that do not exist in inland lakes, reservoirs, and ponds. FPV systems designed to operate in the sea must be able to withstand against strong waves and saltwater corrosion. Implementing protective measures against these hazards will increase costs for PV product manufacturers and solar project developers. Molly Cox, a research associate at Wood Mackenzie Power & Renewables, told GTM that the capital cost of an inland floating solar project is about 10-15% higher than that of a ground-mounted solar project. Hence, offshore floating solar projects are expected to be even more capital intensive.
Ocean Sun, a Norwegian manufacturer of FPV systems, has come up with an innovative solution to improve the durability of the whole generation unit, especially against strong waves. Currently, there are two principal configurations for PV systems that operate above the water surface. The first configuration is known as pure floats and it involves PV modules (or solar panels) affixed directly on top of a specially designed buoyant platform or vessel. The floating units can then be linked together to form an array. The second configuration is floats with supporting trusses. In this concept, solar panels are mounted on a supporting structure that is similar to the one for land-based systems. The structure is then affixed to an anchored pontoon. Both configurations allow solar panels to move around the surface of the water.
Ocean Sun’s design concept is quite different: Solar panels are held together by a blue-colored hydroelastic membrane surrounded by a rigid circular frame for anchoring. This configuration is also humorously described as the “floating solar trampoline.” The membrane, which is in contact with the water, provides better cooling effect compared with the two above-mentioned configurations. Furthermore, the membrane allows solar panels to rise and fall with the waves, thus minimizing the wind drag. Tests conducted by Ocean Sun show that the entire generation unit can withstand sustained winds of up to 275km/h. Thus, it basically has no problem surviving a violent typhoon.
The World Bank’s data on the deployment of FPV systems worldwide show that the cumulative installed capacity in inland lakes and reservoirs reached 1.1GW by September 2018. The World Bank also estimates that the global scale of inland floating solar generation could eventually grow to 400GW. The overall installed capacity is expected to be even more massive and difficult to measure with the addition of marine solar projects in the future. Looking ahead, the demand for offshore FPV systems could grow rapidly in places such as Taiwan, Japan, the Netherlands, and the UAE. Just as in the case of wind power, regions and countries that want to pursue the development of renewable energies but have a land scarcity problem may try to take solar energy to the sea.
(This article is an English translation of news content provided by EnergyTrend’s media partner TechNews. The credit for the photo at the top of the article goes to Pixabay.)