A streak of blue cuts across the yellow landscape as one takes a turn while travelling through the Mehsana district of Gujarat. The dry smell of dust alerts one about the arid zone ahead and the heat is an indication of impending summers in this terrain. Soon, the blue line turns grey with a dense criss-cross of steel.
This is a 750-metre stretch of the Sanand Branch Canal, part of the Sardar Sarovar project, with solar panels on top of it, which make it a one megawatt (MW) solar power plant. This pilot setup, in Chandrasan village in western India, is touted to be the world’s first canal-top solar installation.
Launched in April 2012, by Indian prime minister Narendra Modi, who was the then chief minister of Gujarat, the canal top photovoltaic technology (CTPV) garnered attention internationally. “Solar energy requires a vast expanse of land. With this innovation, we will not need land.
The transmission cost will also reduce as canals are near villages, so the consumers are right there. The power generation from CTPV is better because the panels are cooled by the water underneath. With these advantages, energy generation from CTPV will become cheapest in times to come,” said Modi while addressing the media at the inauguration on April 24, 2012.
“Replicating the pilot project can generate 2200 MW from just 10 per cent utilisation of branch canals,” claims the Gujarat State Electricity Corporation Ltd (GSECL) brochure, the state-owned company which carried out the pilot project. The Sanand Branch Canal, the pilot site, is part of the Sardar Sarovar Narmada Nigam Limited (SSNNL) project, which, at 63,546 kilometres, is the longest canal network in the state. Expert says each megawatt of power from ground-mounted solar panels requires 4 to 5 acres of land. If the estimated 2200 MW capacity were to come up, with panels on Narmada canals, it would save 11,000 acres of land.
But despite the fanfare, 11 years down the line, little progress has happened with respect to CTPV. In 2014 and 2017, the SSNNL installed 20 MW CTPVs across two stretches of the Vadodara branch canal. In 2019, they announced the setting up of 100 MW CTPV, but the project never took off.
The main reason for the slow progress is the high cost of mounting structures on which panels are installed. “Solar power is a competitive market in India. If it does not make clear business sense, developers will not take it,” said Gurpreet Singh Walia, co-founder of Green Ops Private Limited, a solar PV consulting firm in Ahmedabad.
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Solar power is a competitive market in India. If it does not make clear business sense, developers will not take it.
Gurpreet Singh Walia, co-founder, Green Ops Private Limited
“CTPV makes sense in places where land cost is high, like in densely populated areas or agriculturally rich zones. But Gujarat has a lot of barren land available, so why will companies spend on the mounting structure,” said Kaushik Patel, Senior Project Officer, Project Management and Consulting Group, at the Gujarat Energy Research and Management Institute (GERMI), Gandhinagar.
Five days before the canal top solar pilot project in Chandrasan was inaugurated, the then-largest solar park of India, the Gujarat Solar Park in Patan district (also known as Charanka Solar Park) was inaugurated. Located in Charanka village, it is built on, what the authorities claim is “unused land”.
Since then, four large solar parks, including the 30-gigawatt hybrid park in Kutch, that is currently under construction, have come up on 77,704 hectares of ‘wasteland’ in Gujarat. This is apart from the 15 MW solar capacity that was added to Charanka Park later. The cumulative capacity of these parks is more than 32 GW.
However, the ‘wastelands’, as the government claims them to be, are what the pastoralists of Gujarat depend on for their livelihood. These are now under threat from large-scale renewable energy parks. “It is a trade-off. CTPV has a high skeleton cost, while ground-mounted solar has a high land cost. When the trade-off is positive for the people and environment, we go for CTPV. But when the companies get land free or at subsidised rates, a different kind of economics is at play,” an SSNNL official told Mongabay India, on condition of anonymity.
Bright aspect
Even as the cooling effect of water increases solar generation in CTPV, the solar arrays contribute by preventing evaporation of the water below. Sagarkumar Agravat of GERMI conducted a study, on the Chandrasan project, three years after it was commissioned and found that solar modules mounted on canals operated at 10 degrees Celsius lesser temperature than ground-mounted modules, leading to 2.5 per cent better solar efficiency. The study found that around 90 lakh litres of water per MW per year can be saved from evaporation if solar panels shade the canals.
“After energy, water is the next big crisis facing humanity. Canal water is meant for irrigation and it is expensive to reach it in far-off areas. In a hot country like ours, saving on this precious water will create the real water-energy nexus,” said Bela Jani, a retired Gujarat State Electricity Corporation Limited (GSECL) official who played a key role in conceptualising Chandrasan CTPV. “Cleaning panels, which is important for optimal generation, is also easy with solar canals, unlike ground-mounted solar where water has to be specially sourced for the purpose,” Jani told Mongabay India.
SSNNL has eight canal lifting stations in Saurashtra and Kutch districts. It needs 165 MW of power capacity to run these, most of which comes from its hydel projects, while 35 MW comes from its captive CTPV and canal bank solar plants, in which solar panels are installed in the space around canals. From the time they were commissioned to July 2022, the CTPV and canal bank solar projects of SSNNL have generated 294.6 million units, setting off Rs. 1750 million in electricity bills for SSNNL. “The electricity generated here is sent to the local grid and exchanged against our utilisation at the lifting stations. The market rate of electricity right now is Rs. 7 per unit (Kilowatt hour), so that gets saved,” said Nirav Trivedi, executive engineer (Narmada Project Hydropower) at SSNNL.
CTPV can reduce electricity transmission and distribution losses as generation is closer to the consumption point, thereby strengthening the grid. “Since canals reach remote areas, they can be doubly used to provide electricity to farmers in those areas for running irrigation pumps. And at a nominal cost compared to large parks,” said Jani. “The hybrid park in Kutch will need a 250-kilometre-long transmission line for bulk evacuation of power so one can imagine that cost,” the SSNNL official said.
Blocking direct sunlight to water retards algae growth which means less clogging of pumps and irrigation equipment. “Low algal growth also reduces the cost of water treatment if the canal supplies drinking water,” said Walia of Green Ops. Dual use of manpower employed for canal maintenance to clean the panels, canal safety and cleanliness (the entire 3.6-kilometre stretch on which the Vadodara CTPV is installed has been fenced), no pilferage of water and no disturbance to flora and fauna are some other benefits of CTPV.
Pitfalls of canal solar photovoltaic
Because the solar panels on canals are higher than ground-mounted, a CTPV requires a sturdy mounting structure. “The structure has to be heavy; otherwise, wind speed above and below the panels can blow them away. The mild steel frame is also galvanised with zinc to prevent rusting as it will always be exposed to humidity,” informed Patel. “Of the entire capital cost of a CETP, 40 per cent is that of the mounting structure, more than the cost of panels,” said Patel.
The cost of setting up a one-megawatt CTPV is Rs. 15-20 million more than a ground-mounted plant. “Steel prices have increased recently because of the Ukraine war as well as China stopping production. Meanwhile, other cheaper alternatives have come up like floating solar that requires only floaters made of HDPE and PVC, a type of plastic which is not as expensive,” said a former GERMI scientist who didn’t want to be named as he is employed with another organisation now.
The average cost of floating solar comes to less than Rs. 3 per unit, informed Walia. The cost of power from CTPV is beyond Rs. 4-4.5 per unit against Rs. 2-2.85, which is the prevailing rate of solar. “The rate of solar paid by the discoms (distribution companies) is the same for both ground-mounted and CTPV, so why will a developer invest more? Unless the government provides subsidies, CTPVs will not be economically viable,” said Yogesh Sehgal, director of SAM Solar Private Ltd. In 2017, SAM Solar installed two projects of 2.5 MW each in the Ludhiana and Sangrur districts of Punjab. Punjab has a total installed capacity of 20 MW canal-top solar.
In 2014, the union Ministry of New and Renewable Energy (MNRE) launched central finance assistance at the rate of Rs. 30 million/MW for CTPV and Rs. 15 million/MW for canal bank solar. The scheme was meant to assist in setting up 50 MW each of CTPV and canal bank but has wound up now, informed Sehgal.
The linear format of CTPV- the solar arrays are laid out in lengths instead of a plot- also poses electrical and maintenance issues. “A floating solar occupies four acres of the waterbody, an MW of ground-mounted solar takes up to 2.5 acres (with the latest improved efficiency panels) while an MWp of CTPV on a four-metre wide canal will occupy 2.5 kilometres. All the cables have to be brought to a central control room, increasing the cost of cabling and higher losses” said Walia. A Megawatt Peak (MWp) is a measure of the maximum potential output of power produced in ideal conditions as direct current (DC). “The only advantage of CTPVs is that the developer has to deal with a single party- there is no botheration of land acquisition, dealing with people, police, and prices,” he said.
Maintaining a CTPV is cumbersome, says Jaideep Parmar, Deputy Executive Engineer (Solar) at SSNNL. “If there is a wiring fault, 2-3 hours are lost in rectifying it as the technician can’t go below the arrays without safety equipment. All this while, the entire unit has to be shut off. Repairing cracks in the civil structure also becomes difficult with panels overhead,” he said.
Monetising indirect benefits makes a strong case for solar canal
“The present capacity of CTPV in India is less than 100 MW, informed Saptak Ghosh, Senior Policy Specialist at the Centre for Study of Science, Technology and Policy (CSTEP), Bengaluru. However, there is no official data from MNRE on this. CTPVs will, however, help meet renewable targets soon in the face of increasing land scarcity, said Ghosh. CSTEP has calculated the potential of 131 GW in India in an ongoing study that is assessing the feasibility of innovative solar applications that do not require land. This study is being conducted in collaboration with GIZ, Earnst and Young, and Fraunhofer ISE.
“The potential has been determined based on filters like irradiance, 10-kilometre proximity to rail/road, and 25-kilometre proximity to a 132 kV substation. But the MNRE says that since canals are linear, there can be smaller distribution transformers along the length and dispatch power directly from there. That increases the potential manifold,” said Ghosh.
“States like Uttar Pradesh and Bihar who do not have land will go for it sooner,” he said.
The Punjab Energy Development Agency (PEDA) has identified suitable locations for 50 MW of CTPV and is applying for viability gap funding from the Central Government for the payment of differential rates to solar developers. “Land costs are very high in Punjab as all our land is agricultural. The Punjab state utility pays Rs 2.75 per unit for solar, which is too less for developers to come forward. VGF will help there,” said Kulbir Singh, joint director of PEDA.
SSNNL is planning 1200 MW canal-top solar installation on 650 kilometres of the canals in the next three years, informed VP Kapadia, Secretary to the Government of Gujarat and Director of SSNNL. “The progress was slow till now because the canal network was incomplete. Now that it is on the verge of completion, big industrialists have approached SSNNL to build CTPVs for their captive use. They are interested as they can use power for their own industries, and since they own distribution grids, they can sell the power too,” said Kapadia.
Research to reduce the structure cost is ongoing. Panels suspended with high tensile steel rope – where ingredients like chromium, molybdenum, silicon, etc. are mixed to increase its durability – have been installed in Uttarakhand while the Punjab projects are mounted on piers constructed in the canal bed. Experts shared that cantilever-type and vertical panels that do not need to spread across the canal width are also being tried.
According to Patel, the actual cost of ground-mounted versus CTPV can be calculated only when its benefits are monetised. “A private player will only take up a CTPV project when he sees a profit. So, if there is benefit from saving water, its treatment or carbon credits, he should get a share in it,” said Walia.
This story was published with permission from Mongabay.com.
