25 May 2016 07:02:29 IST

It’s time for floatovoltaics

Floating solar plants should be looked at seriously

Scribble-pad calculations show that India’s ambition of 60 GW of ground-mounted solar plants would call for 1,215 sq km of land, or twice the area of Mumbai. There is always the lurking fear that solar might eat into agricultural lands. Even wastelands are not truly ‘waste’ — there could be alternative uses, such as for growing fodder.

However, it is possible to achieve most of India’s solar ambitions without using up much land. How? By putting solar plants on water.

Read CleanTech Dam the solar

Enter floatovoltaics.

According to India’s National Register of Large Dams, the country has 4,862 large dams (whose walls are at least 15 metres high.) The Register counts 59 of them as ‘Dams of National Importance’. The waters impounded by only these 59 spread over 12,732 sq km is as large as 22 Mumbai’s. The reservoir area of the 5,000-odd dams will be a mind-boggling number. Can floating solar power plants be put in them?

For sure, it is technically possible. In January, Japan’s Kyocera announced it would build the world’s largest floating solar system — 13.2 MW — on the reservoir of the Yamakura dam, with technical support from a French company called Ciel et Terra, which specialises in floating solar.

Land not required Recent reports say that Maharashtra intends to set up 1.2 GW of floating solar. Indeed, the entire solar programme of India can be done without taking a square inch of land.

Against this potential, there are just two tiny floatovoltaic plants in the country, each 10 kW big, in West Bengal and Kerala. Few years back, a Bengaluru-based company attempted to put up solar plants on the city’s lakes, incidentally in collaboration with Ciel et Terra, but the project never took off.

Industry players point to two hurdles, and believe neither of them is insurmountable — technical challenges and additional costs.

As Vish Iyer, who heads Solar Business Development at Sterling & Wilson, notes, there exists not much data to arrive at an estimate of large-scale floating solar plants. Yet the industry is not so worried about the costs — it seems convinced that scale effect and on-the-hoof innovation will take care of the additional costs of the floating systems. As a thumb rule, the avoided cost of land offsets the impact of floating systems; only installation, maintenance and transmission will cost more.

Read: A lodging for the sun

On the other hand, higher generation of solar energy could be expected. Iyer, who is passionate about floating solar, guesses the generation could be 15-20 per cent more than land-mounted. Waters cool the solar panels, and cooler panels produce more electricity. Also, there is uninterrupted sunshine, relatively dust-free environment and water is available at hand to clean the panels daily.

Less evaporation loss Furthermore, there is some advantage of avoided evaporation loss. Roughly, evaporation sucks up 1.25 billion litres of water from every sq km. On the overall, floating systems will cost a little more than land-mounted today. But in future, with large-scale adoption, floating systems can be built to be even more economical than the land-mounted ones. Experts such as Pashupathy Gopalan of SunEdison, which has done floatovoltaics in Singapore, believe so.

The industry points to a few technical challenges, but these are more in the nature of ‘fear of the unknown’. Hydro power expert Shibu Kochery, who is also the Country Head, Hydro Power India Pvt Ltd, notes that water level in Indian dams, which could vary “tens of feet”, and the occurrence of flash floods, would call for careful mooring/anchoring to avoid panel damage. Rahul Gupta of Rays Power Experts points to the possibility of micro-cracks in the solar cells due to the constant bobbing movement underneath.

Connectivity to the grid is another unknown variable. The distance to the nearest substation is vital, as more the distance, the higher the cost of setting up the transmission line, notes Sunil Rathi, Director of Sales and Marketing at Waaree Energies Ltd, a company which makes solar panels and also builds solar plants for others. As a corollary, if the site is a hydro electric project it could be simpler to plug solar into the existing transmission infrastructure, provided there is spare capacity.

Industry players that BusinessLine spoke to concede that floating solar has been a passing thought, but never seriously considered. However, they are also unanimous in the view that it is technically and economically do-able.

Rathi says Waaree has been lately getting some enquiries from potential customers and “expects to see more action in the coming years.” Rays Power secured an order in 2014 for putting up a 20 MW solar plant on the slopes of the Morbe Dam in Navi Mumbai, but the project is yet to take off due to the some “internal issues” of the customer, the Navi Mumbai Municipal Corporation. “We are looking forward to floating solar in the near future,” says Gupta.