16 May 2016 14:14:01 IST

Dam the solar

India has 4,862 large dams with huge reservoirs, it is time to use these spaces to harvest solar power

India wishes to install 100,000 MW of solar power capacity by 2022. Today, we have 6,000 MW. So, the task is to add 94,000 MW in the next six years — a tall order — but that is not the point of this article.

The aim of the Ministry of New and Renewable Energy is to install 40 GW out of the 100 GW on rooftops; the other 60 GW will come on vast vacant lands. But to harvest 60 GW of solar, you would need lands roughly twice the size of Mumbai city. (Here is the math: One MW of solar takes 5 acres, 60,000 MW will be 300,000 acres, which is 1,214 sq km. Mumbai city is 603 sq km.)

The land issue

Now, it is a challenge to find land that can be as large as two Mumbai cities, unless you poach into agriculture, which is not a smart idea. And, the ugly thing about land is its price. Experience has shown that when people know you want to buy their land to put up an industrial project, they jack up the prices, dig in their heels and refuse to budge. Land is the big cost driver and its effect will be felt in the price of energy the solar plants produce.

Fortunately, there is a way out. Say goodbye to land area, look instead for water area. You can put up floating solar power projects on water bodies, such as dam reservoirs.

Temples of modern India

India is a land of dams. According to the National Register of Large Dams, the country has 4,862 large dams, and another 312 under construction. Each dam creates a huge lake, most parts of which are open to uninterrupted sunlight for most part of the year. Where better to put a solar plant?

To give you an idea of the area covered by reservoirs: The NRLD, based on certain criteria, classifies 59 of the large dams as ‘Dams of National Importance’. These 59 dams have a total reservoir surface area of 12,732 sq km, or 21 Mumbais. These 59, mind you, are ‘dams of national importance’, not necessarily biggest of the 4,862 ‘large’ dams. In fact, many of the others cover significantly larger area.

There is enough water surface area to accommodate India’s solar ambitions a hundred times over.

But can it be done? For sure, it can be.

In January, Japan announced the start of the world’s biggest floating solar power project — 13.7 MW — on a water area of 0.18 sq km, roughly the size of 18 football fields. The country is clearly after renewable energy, after the Fukushima incident — as mentioned in the previous columns, Japan is building the world’s biggest offshore wind plant, a 5 MW Mitsuibishi turbine.

Been there

Japan’s solar module company, Kyocera, is putting up the project — yes, you guessed it — on a dam reservoir. A French company called Ciel et Terra, which specialises in floating solar, is helping Kyocera put up the project on the Yamakura dam.

Ciel et Terra? At least for the residents of Bengaluru, the name should ring a bell. Ciel et Terra partnered with a company called Enzen Global Solutions to build floating solar power plants on the lakes of Bengaluru, back in 2011. The project never took off, presumably because of the costs — those were the days when solar was still new and project costs were a lot higher.

So, it is not that India never thought of it. Indeed, there are a number of tiny floating solar plants in many places. The solar module maker, Vikram Solar, made news in 2014 when it put up a 10 kW plant on a lake in New Town, West Bengal. More recently, in Kozhikode, Kerala, a 10 kW plant was put up on the Banasura dam reservoir.

Science says that solar panels work better when they are cool – they need light, not heat. Floating on a barge on a water body can raise the output of the panels by 10 per cent. The advantages are too obvious to ignore. That India’s dam reservoirs will see large solar power plants is really a one-sided bet.