Floating photovoltaics – uncovered 

    By now, it has become clear that there will not be a transition to clean energy sources without photovoltaics. Both ground-mounted and rooftop installations have gained precedence, however floating photovoltaics, agrivoltaics and building-integrated photovoltaics have yet to be adopted into the mainstream.  

    In this post, we will consider floating photovoltaics and their advantages over regular photovoltaic installations.  

    What are floating photovoltaics?  

    Floating photovoltaics (FPV), alternatively known as floatovoltaics, are an emerging technology in which solar PV systems are floating upon bodies of water.  

    The first-ever commercial floating photovoltaic system was installed as early as July 2007 in Napa Valley, California, by a SPG Solar. It was a 400 kWp installation and cost $4.2 million. The beformentioned price corresponds to $10.500 per kilowatt peak. Today, costs are much lower, but we will address the issue of costs later in this post. 

    Firstly, let´s look at some of the advantages and disadvantages of FPV and some of the most interesting installations around the globe.  

    The advantages and disadvantages of floating PV 

    Advantages: 

    First of all, FPV is more efficient. There are several of reasons for this; For one, FPV benefits from additional diffuse irradiation from surface reflections. Secondly, the cooling effect of the water contributes to keeping the solar panels cooler. Temperature control is crucial because a solar panel’s efficiency decreases with heat.  

    Besides increased efficiency, floating photovoltaics do not require land or rooftops. Some options to install FPV are ponds, lakes, reservoirs, offshore or even some rivers.  

    Further, FPV can also give back to the environment, as it helps to reduce evaporation and algae bloom by protecting the water underneath from solar irradiation. In addition to this, it can improve water quality.  

    Naturally, floating photovoltaics do not only have advantages but disadvantages as well.  

    Disadvantages: 

    One disadvantage is the requirements for a high-quality racking system. As this floating system must hold the solar panels for 25 years or so, the racking system needs to have high corrosion resistance, a long lifespan and a high load capacity. 

    A further disadvantage is the cost. We will address this later in the post once we have reviewed some of the most interesting floating photovoltaic installations to date.  

    Floating photovoltaic use cases  

    In the picture below, you can see the FPV system installed at the highest altitude so far. Located in the Swiss Alps at an altitude of 1,810 metres above sea level. The high altitudes make it as efficient as solar plants in desert regions. A Swiss company called Romande Energie built the site on a reservoir with a primary use of generating electricity from hydropower.  

    1: Copyright by Romande Energie

    The world’s largest FPV solar farm is under construction in Indonesia, with an expected nominal capacity of 2.2 GWp. This construction requires a surface as large as 1.600 hectares, or the equivalent of around 3.000 football fields.  

    Singapore has already installed one of the largest floating PV plants, which has been in operation since August 2021. This plant is part of Singapore’s goal to quadruple solar energy capabilities by 2025.  

    Europe’s first floating solar farm is in Pirolenc, France. It is situated on an artificial lake and offsets thousand of tonnes of carbon emissions each year.  

    The costs of floating photovoltaics  

    As promised, we will now have a look at the costs of floating photovoltaics. To keep this short and simple, we refer back to the levelized costs of energy metric, that helps us compare costs of energy no matter the energy source.  

    The formula used to calculate this is as follow:  

    LCOE = [Sni=0 (Ii + OMi + Fi – TCi – D– Ti + Peni + Ri) / (1+r)i] / [Sni=1 Ei / (1+r)i]   

    where (i) Ii is the invested capital in period i, (ii) Mis the costs of maintenance in period i, (iii) Fis the cost of fuel in period i, (iv) Ei is the energy output in period i, (v) TCi is the tax credit in year i, (vi) Peni is the sum of the production loss and the penalty (paid for non-compliance) in year i, (vii) Di is the depreciation in year i, (viii) Ti is the tax levy, and (iv) Ri) is the royalties of the corresponding year. Tax credit and Penalty are subject to each specific PPA. 

    If we were to simplify the above formula, we would rewrite it as follows:  

    LCOE = NPV (CAPEX + OPEX) / NPV (GENR)  

    where NPV is the Net Present Value, CAPEX the capital expenses, OPEX the operational expenses, and GENR the amount of electricity generated.   

    According to a recent report by DNV GL, current LCOEs floating PV are estimated to be 354 €/MWh. This is still more expensive than ground-mounted alternatives. However, the cost is expected to level out in the future.  

    Summary – Why floating photovoltaics 

    Floating solar photovoltaic installations open up new opportunities for scaling up solar generating capacity, especially in countries with high population density and competing uses for available land. They have certain advantages over land-based systems, including utilization of existing electricity transmission infrastructure at hydropower sites; close proximity to demand centres (in the case of water supply reservoirs); and improved energy yield thanks to the cooling effects of water and the decreased presence of dust. All of these advantages are yielded at a nearly competitive price at utility-scale capacity.  

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