Floating PV - potentials and challenges in Germany

​published on 4th December 2020

Floating photovoltaic systems, also known as floating PV, have already cracked the 1,000 MWp mark in global installed capacity by 2018. Increasingly, quarry ponds of disused gravel pits are also being used in Europe, and the exit from coal mining in Germany with its then unused open-cast mines opens up a large area potential.

Current status

The first floating PV project in Germany was successfully implemented by Erdgas-Südwest in the middle of last year. In Renchen in Baden, a floating PV system with a capacity of 750 kWp now supplies an adjacent gravel plant with electricity. The amount of solar power generated and the share of own consumption was even higher than calculated in the first year. The electricity costs of the gravel plant could be reduced by 10 percent.

But project developers are also showing increasing interest outside Germany. Because such or similar projects like the one in Renchen are now being implemented in many different ways throughout Europe. In Albania, for example, a 2 MWp Floating PV system was built on the reservoir of a hydroelectric power plant, where it functions as part of a hybrid solution. In the Netherlands, the company BayWa r.e. is currently implementing the largest floating PV project outside of China with a capacity of 27 MWp.

Growing confidence in the technology ensured that, according to estimates, approx. 2.4 GWp of floating PV capacity was installed worldwide at the end of 2019. The ITRPV forecast even concludes that the worldwide installed floating PV capacity will even increase to 10% of the total installed PV capacity by 2029.  

Technical expansion potentials

In Europe, a total area of over 20,000 km² would theoretically be available for development. If only 1 percent of this area would be used for the construction of floating PV systems, a capacity of 20 GWp could be installed. It is estimated that the plants would thus produce over 19,500 GWh of renewable electricity per year.

The potential of Floating PV has also been analyzed in Germany. The Federal Republic of Germany has almost 500 opencast lignite mining lakes with a total area of 47,251 hectares. The total economic potential of 4.9 percent of the theoretically available lake area corresponds to an installed capacity of 2.74 GWp. In total, there would even be a potential of about 55 GWp. Considering the circumstances that the share of opencast lignite mining lakes only corresponds to 12.9 percent of the total of all artificially created water bodies in Germany, an even higher potential for the technology can be expected.

The identification of a suitable extension area depends on several factors. For example, in addition to an unshaded watercourse, there must be easy access to the water. Furthermore, the location must be as quiet as possible (artificial reservoirs, industrial waters such as cooling ponds and wastewater treatment plants, irrigation ponds, etc.), and in the best case, a certain electrical infrastructure is already available. Also, the water should preferably be freshwater with a shallow depth and a hard bottom to facilitate anchoring.

Furthermore, there must be sufficient land area for the use and placement of the required electrical infrastructure.

Especially the combination with hydroelectric power plants as a hybrid solution could be relevant for the future construction of floating PV systems due to the steady generation, the already existing grid connection, and the excluded other use of the restricted areas in front of the dams.

There are further advantages in terms of water ecology. The modules can reduce the evaporation reaction and the partial shading keeps the water temperature at a lower level. This reduces the risk of excessive algae formation. Also, the systems can create quiet zones for fish. 

 
Systems Engineering

In a floating PV system, the PV modules are installed on floats. The individual module parts are linked to each other by movable connecting pieces and thus ensure the most flexible possible adaptation to the water surface. The floating system is secured by a mooring system. The mooring, which is considered a key component, provides mechanical stability, can adapt to water level fluctuations, and maintains its position in the intended orientation. The robustness of the mooring system is crucial to withstand the weather. A precise design of the mooring system depends on the location. The PV system is connected to the power grid and the respective consumer via (sub)water cables.

Economic efficiency

The technology of floating PV systems is characterized by a slightly higher yield compared to conventional PV systems. This additional yield is achieved by the cooler ambient temperature and the better wind ventilation that exists compared to conventional systems. The temperature of floating modules is 5-10°C lower than in onshore installations. Thus, the output of a PV module with 270-310W at 10°C lower ambient temperature increases by about 3.9 percent. This corresponds to an increase in output of 8.25-12.1 Wp, which ultimately allows higher yields to be achieved.

Installation costs are about the same for both applications. Although the installation of floating PV systems is easier to carry out, at the same time specially trained personnel is required. Also, the maintenance costs for both types of PV hardly differ. On the one hand, floating PV systems are comparatively less dusty and the water needed for cleaning is directly available if necessary, but on the other hand, the risk of contamination by birds increases, and boats and divers may have to be called in to maintain the system.

However, the investment costs of floating PV systems are higher than those of conventional systems. The reason for this is the required water-resistance of the components, the comparatively more complex construction, and the long lines of the system. Also, economies of scale have not yet been realized as much as with conventional PV systems due to the comparatively young technology. According to the World Bank, the total investment costs of floating PV systems amount to about 0.67-1.00 €/Wp.

 
The partly strong variation of investment costs becomes clear when comparing different projects.
The investment costs of the floating PV modules as a hybrid solution for the already mentioned hydroelectric power plant in Albania, as well as for the largest implemented floating PV project "OMEGA 1" in France to date, amounted to 1.00 €/Wp each. However, while the German project in Renchen required an investment of around 1.33 €/Wp, the world's largest Floating PV plant (155 MWp) in China cost only 0.88 €/Wp. This shows that the costs can certainly drop as the size of the projects increases.

When calculating the economic efficiency of floating PV systems, in addition to considering the rising investment costs and higher yields, the proportion of the plant's electricity consumption is also decisive.

The table shows that the yield of a floating PV project depends strongly on the share of the own power consumption and tendering systems are currently not yet competitive in tenders. From this, it can be concluded that Floating PV systems in the size of max. 750 kWp on EEG eligible areas are particularly attractive, especially in the vicinity of large consumers.

Summary

Since floating PV is only just beginning to be perceived as a serious technology, many positive developments can be expected soon. Economies of scale will lead to cost reductions in substructures, the increased application will increase confidence and thus lower the perceived risk. The fact that floating PV systems, like agro-PV, are not in direct competition with food production tends to increase acceptance.

In Germany, due to the regulatory framework, especially quarry ponds with adjacent production and thus high own power consumption are economically profitable. Hybrid solutions in combination with hydropower are intelligent solutions to stabilize electricity generation.

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