Floating solar panels or floating photovoltaics refers to solar panels that are designed for water bodies; it functions the same as ordinary solar panels that we see on rooftops, converting light into electricity. With the emergence of floating solar farms, one might wonder what the purpose of putting solar panels on the water is. Here, we explore the relative pros and cons of floating solar panels compared to conventional terrestrial ones.

Currently, the largest floating solar farm in the world is located in Dezhou, Shandong, China, generating 320 megawatts (MW) per hour. But several more countries have started to launch their own projects aimed at dethroning China’s current leading status. This includes India, which is building a 600MW floating solar farm at the Omkareshwar Dam on the Narmada River, as well as South Korea, which has permitted the construction of a floating solar farm with a capacity of 1,200 MW in the province of North Jeolla, which is equivalent to about 0.9% of the total capacity of electricity generation of the whole country. It is expected to be in commercial operation by the end of 2022.

Floating Solar Panels Have Higher Efficiency

Compared to the long history of solar energy, the concept of floating solar did not emerge until the late 2000s and is being quickly adopted. In 2021, floating solar across the world generated about 1,600 MW of electricity, but it is estimated that the number will reach 4,800 MW by 2026, with a compounded annual growth rate of 33.7%. 

One of the major reasons that this technology is being favoured by nations is its relatively high efficiency compared to ordinary photovoltaics. Floating solar can be up to 15% more efficient than terrestrial solar, according to the Environmental and Energy Study Institute, due to the cooling effect of the water. Solar panels, like other electrical equipment, operate more efficiently when kept cold. 

The ideal temperature for a solar panel is below or equal to 25C, and it will endure a decrease in productivity when its temperature is above 25C. Based on the model starting at 25C, a solar panel loses about 0.3% to 0.5% efficiency for every increase of 1C in temperature. The percentage decrease for each degree might not seem high at first, but since most solar panels can grow far hotter than 25C, reaching up to 40C, 50C, or even 60C in this era of climate change, the accumulated effect becomes much more significant. 

Although the ambient temperature in summer in most countries is around that range, the temperature of the solar panel is much higher than its ambient temperature as its primary duty is to absorb the sun’s thermal energy. Ironically, despite the purpose of solar technology in mitigating global warming, it is significantly increasing the temperature in urban areas by trapping heat on the rooftops. 

Today, the efficiency, which refers to the portion of energy in the form of sunlight that can be converted into electricity, of most solar panels ranges from about 15% to 20%. If a solar panel that can perform with an efficiency of 20% reaches a temperature of 45C or 55C, its efficiency drops down to the range of 18% to 18.8% or the range of 17% to 18.2% respectively. 

This is where the concept of floating solar comes in. Seeing that land-based solar panels do not function at their full potential, scientists have come up with the idea of using water as a coolant to maintain the temperature of solar panels at a lower level, preventing loss of energy due to high temperature.

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Floating Solar Uses Less Land

One of the world’s largest terrestrial solar farms is the Bhadla Solar Park located in Jodhpur, Rajasthan, India. It has a capacity of generating 2,245MW per hour. Yet, in order to capture that much energy, this solar farm takes up more than 14,000 acres of land to do so. Not every country is as large as India and has that much land availability to build multiple terrestrial solar farms. Floating solar, on the other hand, does not require taking up scarce land solar panel installations. Floating solar can be put in place in many types of water bodies, from oceans to lakes and reservoirs, on which the opportunity cost of building solar panels is relatively low as they are mostly idle and use only fractions of space – and do not affect recreational activities like fishing.

Cost of Floating vs Terrestrial

If we compare the two, all the disadvantages of floating solar panels such as intermittency of solar access or pollution (and the greenhouse gases) derived from the extraction and production of materials used to produce them, can also be applied to their terrestrial counterparts while the advantages of floating solar panels are not inversely replaceable; the former is essentially the more evolved version of the latter. Yet, if we truly want to nitpick, the cost of floating solar is more expensive than terrestrial solar. Estimates suggest that the cost of installing floating solar panels is about 10% to 15% higher than land-based panels, given the additional cost required to manufacture the floats. But in terms of the cost of operation and maintenance, it is surprisingly close between the two. Although activities like accessing floating panels that are located away from shore or performing preventive maintenance of anchors and mooring lines require additional costs, these additional costs are compensated by the elimination of the cost of maintaining fencing as well as the lack of vegetation, which is often applied in terrestrial solar to keep the panels cold.

The Future of Floating Solar

Due to its relative infancy, current floating solar technology does require a one-time cost of installation that is more expensive. Nevertheless, compared to its long-term effects on preventing the leak of energy up to 15%, at least during the solar panels’ lifespan of 25 years, floating solar is actually more cost-effective and one can make the case that its advantages outweigh terrestrial solar. Governments should consider adding float solar technology to the energy portfolio and part of the renewable energy transition strategies.