The freedom to float

Figure 1. In 2020, BayWa r.e. completed the largest floatingphotovoltaic (PV) system outside of Asia – the 27.4 MWp Bomhofsplas plant. The plant is located on a quarry pond in Zwolle, in the province of Overijsse, the Netherlands.

Toni Weigl, BayWa r.e. Solar Projects, Germany, highlights the role floating-PV can play in the future to maximise the world’s use of solar energy while diffusing debates around land usage.

As climate targets become more ambitious by the day, diversifying the renewable energy mix is more important than ever. Due to its flexibility and ability to work in a range of environments, solar energy is playing a key role in ramping up these efforts. Ground-mounted solar installations are already well-established and are highly efficient in terms of performance and production costs providing power at lower cost than conventional energies. However, as the world looks to extend the enormous potential of solar energy, floating-photovoltaics (PV) is an exciting solution that must be further used. The World Bank recently estimated that there are 400 000 km2 of man-made reservoirs around the world. If that was to be converted to floating-PV, the space has a theoretical energy production potential on a terawatt scale. A humbler goal shows that in Europe alone, accommodating floating-PV on just 10% of man-made freshwater reservoirs would create approximately 200 GWp. Although these figures show that the known potential for floating-PV adoption is considerable, the unrealised potential of this technology remains vast.

A snapshot of the European market

While floating-PV has been more commonly associated with the Asian solar market, the technology is gaining momentum across Europe as the region races to meet its decarbonisation goals. The technology is becoming an attractive solution for developers who are often faced with land scarcity issues – making it a viable option for high-population density localities without competing against other uses for the land.

The Netherlands has taken an early lead in the sector. Due to the falling cost, subsidy schemes, and an increased understanding of the benefits of the application, the market is expected to grow by 2 GW by 2023 in the country. The Netherlands’ sustainable energy subsidy scheme (SDE++) – which replaced the SDE+ last year – is a great example of how subsidies are foundational in the realisation of CO2 reducing technology.

Floating-PV is expanding into other European countries, as a technically and economically feasible complement to other PV applications such as standard ground-mounted PV or agri-PV systems. In Germany, special tariffs have been introduced, enabling a specific tender category for technologies such as floating-PV. However, like so many other countries, the project size within these tenders will need to expand in order to unlock its full potential.

Advantages of floating-PV

As already touched on, a key benefit of floating-PV technology is that by using unused bodies of water – from disused coal quarries and mineral extraction pits to reservoirs – it can make an important contribution to the green energy revolution while diffusing debates around land usage.

Not only does floating-PV save on land space, but the solar panels also naturally aid the reduction of water evaporation. This is particularly important for countries facing water security issues and shortages – it is currently estimated that more water evaporates from reservoirs than is consumed by humans. By absorbing a proportion of the incoming solar radiation, the panels act as a physical barrier for the water and, therefore, play a key role in wide-ranging water conservation strategies. Water quality can also be improved, with the panels discouraging the growth of certain algae.

Compared to other renewable energy technologies, floating-PV offers comparatively easy installation and maintenance. The layout of the panels is generally the same as is required for land-based plants, but these modules are mounted on floating platforms – along with the inverters and sometimes the transformers.

Installation costs

Getting anchoring and mooring technology right is a critical factor for any floating installation, for costs and risks: due to adverse weather conditions, there have been examples in the past where several systems have been literally blown away because of insufficient anchoring. Providing robust solutions that stand the test of time is clearly important in ensuring the operation is not only uninterrupted but also avoids costly repairs or replacements – because only a long lifetime of the generator leads to the lowest possible electricity cost.

Today’s remotely operated GPS tracking and monitoring systems can flag any issues with arrays that experience higher motion than anticipated, as well as alerting operators to any maintenance or operational issues. The small, but growing pool of suppliers and developers are helping to increase uptake and ensure these systems are easy and safe to install and maintain.

Figure 2. Construction of a floating-PV site.

Exploring the environmental impact

Before the installation of a floating-PV project commences, it is important to understand how it will affect the waterbody. Lately, more research is being carried out in this area.

In a first-of-its-kind study, independent research was recently carried out by Hanze University of Applied Sciences Groningen to assess how floating-PV affects the environment. The studies started at the construction of BayWa r.e’s Bomhofsplas plant in February 2020 in Zwolle, the Netherlands – one of the largest floating-PV farms outside of Asia. The initial results were extremely positive and showed no adverse effects on the surrounding environment at the floating-PV farm. It has to be mentioned though that those results are only applicable to BayWa r.e.’s system, which is significantly different to other floating types, as the generator has a very small footprint on the water surface. With results being published in MDPI’s peer-reviewed Sustainability journal, the study compared different water quality parameters below floating solar panels with a location away from the park, with the parameters outlined next.

Figure 3. The 41.1 MWp Sellingen park and 29.8 MWp Uivermeertjes park are now the two largest floating-PV parks outside of Asia, and combined will generate enough electricity to supply more than 20 000 households.

Water quality

The water quality showed no major differences in the measured key water quality parameters below the solar panels, such as conductivity, temperature, or dissolved oxygen. The temperature at the upper layers was only slightly lower under the solar panels, and there were fewer temperature fluctuations detected. The used floating-PV system which allows wind and sunlight to easily reach under the panels was identified to be a possible reason for this. When looking at the site as a whole, the researchers found that the water quality below the floating-PV farm remained at the same good level as the surrounding water surface.

Biodiversity and ecology

It was found that the presence of the floating-PV panels leads to less wind activity on the water surface, resulting in less erosion of the banks. Vegetation growth was therefore protected and stimulated.

In terms of wildlife, ongoing research is also being carried out to assess the impacts on the fish population at the lake. Bio huts made by Ecoocean have been filled with seashells and submerged beneath the floating-PV panels to potentially encourage marine life and greater biodiversity. Positive effects have been observed after the first year review. The bio huts showed positive evolution prospects (including some fish) for the scientists to analyse further in the coming years.

Continuous multi-year research

The initial results of the research carried out on the Bomhofsplas site are positive and serve as a solid foundation in how the company can produce renewable energy while also preserving and improving the conditions for the surrounding environment at floating-PV sites – at least for the chosen technology.

However, continuous research into floating-PV is needed to map out a complete picture for the future. The more the effects on ecology, wildlife, and water can be measured, the easier it will be for future installers to demonstrate minimal environmental impact. This will also pave the way for easier, more straightforward permit procedures.

What is next for floating-PV?

As floating-PV continues to evolve, it will become a technical and economical option that is complementary to ‘standard’ PV systems. As a result of the falling cost and increased understanding of the benefits of the application, the future of floating-PV is bright. The European expansion of floating-PV will serve as an important contribution to the green energy revolution without competing against other uses for land.

Ongoing research, such as that carried out by Hanze University of Applied Sciences Groningen as well as Buro Bakker/ATKB, will be vital in understanding and unlocking the potential of floating-PV technology. Beyond this, floating-PV can create new job opportunities in the renewable industry in everything from business and design to construction and maintenance. Not only does this offer a unique set of skills drastically needed in the industry, but it will also boost local economies and strengthen communities.

The priority for the next few years should be to roll out floating-PV at sites where it is already economically feasible to do so. In order to ensure regulatory approvals, it will be important to maintain regular dialogue between all stakeholders in order to encourage knowledge-sharing and best practices. The hope is that the development of tariff systems from country to country will support the growth of the sector, to the point that (in a similar vein to ground-mounted solar) subsidiaries will be less important and projects will become self-sufficient, for example, via participation in the power market through Power Purchase Agreements (PPAs).

For now, it is clear that floating-PV has an exciting role to play in the expanding renewable portfolio alongside other so called ‘double-function-applications’ such as rooftop-PV, agri-PV, or carport-PV. Across various countries and markets, the cost of installations will fall as technology and construction methods mature, expertise increases, and the use of floating-PV becomes more mainstream.