Canal-top solar plant revolutionizes solar farming

2012-10-30 - Innovating in Chandrasan, Gujarat, to combine solar power generation with water and land conservation

About 25 kilometers from the city of Ahmedabad in Gujarat is a strange sight − instead of the sparkle of water in the distributary canal, a vista of blue solar panels stretches as far as the eye can see. The one-kilometer stretch that forms the canal-top solar farm has transformed everyday life for the people who live and farm along the Narmada canal.

In India, providing reliable access to electricity and safe drinking water in rural areas is the greatest challenge a state government faces. The failure of the monsoon can lead to acute water shortages and in drought-prone areas many villagers think nothing of a five-kilometer trudge to fetch potable water. Water is vital and the Narmada canal and its branches extend over some 19,000 kilometers in the western state of Gujarat.

Despite this provision, an enormous amount of water is lost, first through evaporation and then by the wind that whips the water vapor away. The hot sun also promotes the growth of algae, which clogs the motors of the pumps farmers use to irrigate their land.

The 1 megawatt (MW) Narmada Solar Energy Plant project was awarded to SunEdison with a mandate to provide solar power and simultaneously conserve canal water. The project was sited at Sanand branch canal near Chandrasan for good reason – accessibility to a grid, good roads and a north-south orientation to take maximum advantage of daylight. The 16-meter spans of the Narmada Solar Plant rest on one center support and
connect to the banks on either side of the canal. The blocks forming the spans cover about one kilometer of the canal. In the center of the span an opening provides access for maintenance. Walkways, 15 meters apart, are used for regular cleaning of the panels.

One of the biggest challenges was to prevent loss of water through evaporation. The engineers responded with an innovative new design for ‘floating windbreakers.’ Vertical panels were attached to the first and last row of the structures, connected to free floating barrels in the water. The barrels rise with the water level, lifting the panels above. In this way the water is shielded from the wind and yet allowed to flow unimpeded. By this clever stratagem, almost seven million liters of water will be saved annually.

There is another advantage to the canal-top solar farm: the panels are cooled by the water flowing below adding a further 15% to power generation capacity, as compared to land-based solar plants. In the long term, if just ten per cent of the 19,000 kilometer canal network in Gujarat is dedicated to canal-top solar farming, it has the potential to produce 2,200 MW of power while freeing 11,000 acres of arable land and saving about 2,000 crore liters of precious water every year.

We too had a part to play in this intelligent solution to tapping the sun and saving water and land, all at the same time. We received an order for a compact substation (CSS) with a 1 megavolt ampere (MVA) transformer, based on delivery time commitment. The CSS was shipped out from Nashik, in neighboring Maharashtra and installed on site in short order. Soon after, in July 2012 we received a follow-up order to install a ring main unit
(RMU), a type of switchgear, typically used in a secondary distribution system. The job of the RMU is to protect the distribution transformer from current fluctuations and assure uninterrupted power supply.

On April 25, 2012 what the press called “the world’s first canal-top solar power project” was inaugurated in Chandrasan. The second phase of the project will increase the solar power generation capacity to 2 MW. In the future, the conventional panels may be replaced by a new, sun-tracking solar panel technology, in which the panels will move in synchronization with the sun as it travels across the sky.

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