Chennai: During his address to the Tamil Nadu Legislative Assembly in June 2021, the state governor said that old and inefficient wind mills, or wind turbines, would be re-energised. In industry parlance, this is called repowering, where old turbines are replaced with new ones that can produce more energy.

India's alternative energy programme to produce electricity from wind started in earnest in the late 1990s, although the pilot project was started in Tamil Nadu in 1986, industry hands told us. Tamil Nadu, Gujarat, Karnataka, Maharashtra, Rajasthan and Andhra Pradesh, with high wind power densities essential for wind power generation, are best suited to harness wind power.

Tamil Nadu had the highest installed wind power generating capacity, with 9.6 gigawatt (GW) as of March 31, 2021, per Ministry of New and Renewable Energy (MNRE) data. Gujarat stood second, with 8.56 GW capacity. As the states that took to wind energy generation first, Tamil Nadu and Gujarat have the oldest wind turbines, many of which are located at the best sites for harnessing wind energy. For better utilisation of wind resources and increased safety, these old wind turbines need to be repowered.

India's current installed wind power generating capacity is 39.2 GW; the country is targeting installation of 60 GW by 2022. The average annual capacity addition over the last five years, however, has been only 2.48 GW. Attaining the target will need new capacity addition, as also repowering on a large scale.

India's electricity demand could grow three-fold from 949 TWh (terawatt-hour) in 2015 to between 2,074-2,785 TWh by 2030, according to a 2018 report by Brookings India, a non-profit public policy organisation. Renewable energy generation must increase at least six-fold to meet Paris Agreement climate change goals, per the Global Energy Transformation: A Roadmap to 2050 report by the intergovernmental International Renewable Energy Agency. Repowering wind farms could be part of fulfilling India's commitment to obtain 40% of its installed capacity from non-fossil fuel sources by 2030 under the Paris Agreement, besides ensuring low carbon growth in the power sector.

Repowering, however, has yet to take off, despite an MNRE policy announced five years ago, partly because existing public utility infrastructure in the states cannot carry increased energy output from windfarms, say industry experts. Daunting costs and a lack of financial incentives from the government are further roadblocks to repowering, they say. Further, they point to the lack of mechanisms to ensure implementation of the repowering policy including its advisory nature, which does not compel stakeholders in industry and state utilities to repower, or add the required infrastructure to handle higher loads from wind farms. Successful repowering models in Europe can show the way forward for India, they say.

India's wind capacity target

India has a target of installing 175 GW of renewable energy capacity including solar power, wind, bio-power and small hydro-power by 2022. This is part of India's nationally determined contribution to reduce emissions, made in October 2015 under the Paris Agreement, a legally binding international treaty to combat climate change. The target is also to have a higher percentage of renewables in the energy mix in the country's electricity grid. Of the total 175 GW, the target for wind energy is 60 GW, apportioned to states per the NITI Aayog's Report of the Expert Group on 175 RE by 2022.

India's current installed wind energy capacity is 39.2 GW and another 9.07 GW capacity (excluding capacity installed by March 2021) is under installation, per the Indian Wind Power Association (IWPA), a non-profit industrial body headquartered in Chennai. This leaves a shortfall of 11.73 GW against the targeted 60 GW by 2022, i.e. to be achieved in a single year. The average annual capacity addition over the last five years, by contrast, has been only 2.48 GW.

What is repowering

"Repowering means replacing a high number of smaller, less efficient turbines with a smaller number of bigger, more efficient turbines. This comes with increases in capacity, hub height, rotor diameter, etc.," Christoph Zipf of Belgium-based Wind Europe, an association working for the promotion of wind energy, told IndiaSpend.

The height of the turbines' hub from the ground was 25 to 30 m in demonstration models used in the late 1980s in India, and in early projects launched in the 1990s. The rotor diameter, or the circle formed when the turbine's blades rotate, was around 30 m, per information shared by K. Boopathi, director and division head of the R&D wing of Chennai-based National Institute of Wind Energy (NIWE), an autonomous institution under the MNRE.

The amount of energy produced increases with an increase in blade length, and hence the rotor diameter. Rotor diameter and hub height have been increasing over the years--the very first wind turbine installed in India had a capacity of 55 kilowatt (KW). The capacity of present day turbines can be more than 3,000 KW (3 MW).

As the latest turbines can produce more energy, and as the older machines occupy the best wind sites when land is scarce, industry experts said that the old turbines must be repowered to realise the maximum potential of the available wind resources and increase power generation. Repowering can thus contribute a reasonable capacity addition to India's renewable energy target, they said.

Repowering potential

As the pioneering state, Tamil Nadu has the oldest wind turbines, which are more than 30 years old and ideal for repowering. "Some would be older because at first we installed imported second-hand machines that would have already run for a few years," K.R. Nair, an IWPA council member based in New Delhi, told IndiaSpend.

The capacity of the first set of turbines in Tamil Nadu and Gujarat ranged from 55 kW to 550 kW. In Tamil Nadu, 53% of turbines of 550 KW or lesser capacity--called sub-550 kW--were installed before the year 2000, according to NIWE literature.

The repowering potential of sub-1 MW turbines was put at 1,577 MW, in a 2017 study on repowering by the Indo-German Energy Forum, Idam Infrastructure Advisory Pvt Ltd and MNRE. At 834 MW, Tamil Nadu presents the most repowering potential, followed by Maharashtra at 400 MW.

For sub-1 MW turbines installed before 2007, the repowering potential is 4,394 MW and Tamil Nadu (2,346 MW), Maharashtra (592 MW) and Karnataka (536 MW) are the key states.

Benefits of repowering

Recent repowering projects in Europe have doubled and tripled their energy production, said Zipf of Wind Europe. "The early wind turbines have a plant load factor (PLF) of 10-15%, whereas the latest machines have a PLF of 30-35%," said Nair. PLF is a measure that indicates a turbine's performance. This shows how power generation could be doubled or tripled, he explained. El Cabrito Wind Farm in Spain reported a 16% increase in energy production after repowering 23-year-old turbines. The Nørrekær Enge Wind Farm and Klim Fjordeholme Wind Farm in Denmark have respectively doubled and tripled their energy production. At the Reussenkoege community wind farm in Germany, 2 MW turbines are being replaced with 3.6 MW turbines.

"Compared to a new project, repowering would cost less, since existing land and infrastructure are being used," said Nair. The latest wind turbines have incorporated measures such as low voltage ride through (LVRT) that enables a turbine to stay connected to the power grid and avoid power outages, and supervisory control and data acquisition (SCADA) that helps monitor and process data remotely. Such mechanisms make electricity transmission more efficient. The older turbines do not have these tools. Repowering will enable installation of new turbines with these tools to make them more compatible with the modern power grid, added Nair.

There are also safety concerns with old turbines. Nair cites the example of Kanyakumari in Tamil Nadu, where a national highway and major roads run close to wind farms. "Decades ago when these turbines were installed, the localities hardly had any inhabitants. But now all the villages have become populated," said Nair. Repowering will eliminate safety risks associated with worn, old turbines. "In addition to increased power generation, repowered turbines will be better aligned to the grid and will eliminate safety concerns. As repowering involves reduction in the number of existing turbines, it improves the aesthetics of the landscape too," added Nair.

Above all are the environmental benefits. "Since the number of total turbines gets reduced when you repower, the risk of birds colliding with turbine blades is reduced. Some of the new turbine models are so tall that some species of birds and bats don't even reach that high," said Zipf. "Repowering also means more electricity production per unit. When wind turbines replace other forms of electricity production such as fossil fuels, there's a higher reduction of carbon dioxide emissions per wind turbine, which ultimately helps us fight climate change. As climate change is the number one threat to biodiversity, biotopes and environment, reducing carbon dioxide emissions helps in restoring biotopes, securing breeding and hunting grounds for birds and bats and facilitating the preservation of these species," he added.


The industry cites lack of financial incentives as a reason for failure to repower, including limits on capacity addition imposed by discoms. "In general, land that has 4 x 250 kW machines can accommodate a single 2 MW or 3 MW turbine. But discoms permit replacing the four machines by a single 1 MW turbine so that the capacity remains the same," Nair explained. This means, for instance, that the energy output of a 1 MW turbine could be doubled or tripled, but state level public utilities don't permit windfarms to increase their capacity after repowering due to inadequate electricity infrastructure to carry the extra load, according to a retired government official who spoke to IndiaSpend on the condition of anonymity.

There is no clarity between the public utilities and stakeholders on sale and tariff of the additional energy produced after repowering. In August 2016, the MNRE brought out a repowering policy "to optimally utilise" the resources, but states have been slow to take it up, though some like Karnataka have taken some initiatives. During deliberations on the procedure and tariff for repowering that the Tamil Nadu Generation and Distribution Corporation Limited had submitted to the Tamil Nadu Energy Regulatory Commission, wind sector stakeholders argued that the MNRE's policy is advisory in nature and need not be followed. The retired official echoed these views, saying that the MNRE policy may not be pragmatic.

The MNRE policy states that if a certain segment of the current electricity evacuation infrastructure (from the point of wind energy generation to the grid) is insufficient to carry the added load after repowering, the infrastructure should be augmented by the state transmission utility, per the retired official. "The utilities say that the transmission infrastructure is not sufficient to carry the added load but without any financial incentive, it's not possible to upgrade the infrastructure," he said. "The government has to realise that we have to move beyond making policies and take up repowering seriously," said Nair.

Some windmill owners are not keen to repower because they continue to get revenue from the old turbines, said Nair. They do not want to go through the procedural formalities involved in repowering. "Old wind turbines continue to be operated because in India there is no restriction on running them, like the restrictions for using old cars," said Nair.

"Wind turbine owners have to spend money to repower. It might take them another 10 years to recover that investment. Instead of that hassle, they are happy with whatever they earn," C. Karthikeyan, who acts as an intermediary for buying and selling existing turbines, told IndiaSpend. In the early years, many people pooled resources to own wind farms. Such multiple ownership of wind farms and lands poses a challenge as not every owner is willing to invest to repower, said Nair.

The MNRE policy, however, precludes additional financial liabilities for the ministry besides those provided for new projects--leaving no incentives for repowering projects. For the latter, the MNRE says that the Indian Renewable Energy Development Agency will provide an additional interest rebate of 0.25% over and above that available on loans for new projects. No one has availed of the repowering rebate thus far, IREDA officials told IndiaSpend in May 2021.

Way forward

In June 2020, when Windpark Zeewolde B.V., a farm owned by more than 200 farmers, residents and entrepreneurs in the Netherlands repowered its turbines, it created a buzz as it showed the earning possibilities of a cooperatively financed effort. In similar cases of multiple ownership of wind farms in India, Nair suggested adopting this cooperative model. There is investment potential for corporate entities that own farms, and for retail investors, he said.

"Banks are willing to lend money to such regional energy collectives. In what we call citizen energy, a special purpose vehicle serves just this one wind energy project. If the banks see that the special purpose vehicle has enough equity, they are very much willing to lend money," explained Zipf, "The loans are stretched over the lifetime of the turbine. The company gains revenues from electricity production and uses them to repay the loan up to a certain break-even point; from there on the company makes a profit. In a worst-case scenario in which the company cannot pay, the banks would take ownership of the wind turbine." He added that he was not aware of any such asset having been seized.

"IWPA has been making representations to the ministry about the challenges. It's the government's responsibility to ensure that the repowering policy works on ground," said Nair. Industry stakeholders say that the government needs to address the concerns of the developers as well as utilities, arrive at a viable commercial proposal, and provide an enabling environment so that the aim of the MNRE policy is achieved.

(This story has been produced as part of Earth Journalism Network's Renewable Energy Media Fellowship 2020.)

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