To keep up with the 2030 renewable energy target, India is fighting costs, climate change and windmill capacity

Glistening in the bright rays of the sun, rows of rotating white turbines dot both sides of National Highway 44 in Tamil Nadu’s Kanyakumari district. Located in one of the regions with the highest wind potential near the southernmost tip of the subcontinent, some of these wind turbines are also among the oldest in the country and are now nearing the end of their life cycle.

“The first of these windmills was installed here in 1994. At that time, these 250 KW missions could generate up to 4.5 lakh of units per year. Over the past 28 years, their capacity has plummeted to 2.5 lakh units per year, mainly due to aging, “says SV Subbaraj, AGM at Ramco wind farms located in Muppandal, where winds from the Arabian Sea blow across. the mountain passes by turning the blades.

The village in the Kanyakumari district is home to the country’s largest operational onshore wind farm, with a generation capacity of 1,500 MW, and is an integral part of Tamil Nadu’s total installed capacity of 9,600 MW. The state is the hub of wind energy in India and significant if it is to reach the goal of 500 GW of renewable energy by 2030, announced by Prime Minister Narendra Modi in Glasgow last year. And a key part of that goal has been to push for repowering old missions that have passed their design life with high-capacity missions, a transition also made necessary by a government policy for repowering wind projects released in 2016.


The average life of a wind turbine is 25 years, after which its efficiency begins to decline. But with most of these older turbines still running at the wind-rich sites, also called Class I sites, it left little room for setting up the new high-capacity missions, which now need to be moved to fewer windy sites. . Government estimates suggest that more than 10 GW of older wind turbines with a capacity of less than 1 MW are installed at wind-rich Class 1 sites across all states.

“When it comes to clean energy, we have to look at the bouquet of solutions and we could lose if we don’t capitalize on the benefits of repowering,” says Deepak Sriram Krishnan, Associate Director for Energy Program at the World Resources Institute (WRI), India. “Tamil Nadu has been a pioneer in wind power installations, and it is in the state’s best interest to get busy with repowering existing missions, provided there is additional capacity and a fair price for it.”


The oldest wind turbines date back to the 1990s, when small capacity 250 KW missions were organized to some of the best windy sites. Their towers were no more than 25-30 meters tall, much less than the current 100-meter tall towers, which produce anywhere between 1-3 MW of power. The diameter of the old turbines was also about 26 meters compared to about 86 meters for a 1.65 MW mission currently in use.

Wind farms at the Muppandal and Radhapuram sites in Kanyakumari, Tamil Nadu, which are wind-rich sites near the mountain passes.  The Muppandal wind farm is one of the largest in India.  (Photo: News18)
Wind farms at the Muppandal and Radhapuram sites in Kanyakumari, Tamil Nadu, which are wind-rich sites near the mountain passes. The Muppandal wind farm is one of the largest in India. (Photo: News18)

Some of the developers also decided to redesign some of the existing missions on a test basis and to carry out research and development (R&D) work. “One of the missions that overlooks the palm trees is about 114 meters high and generates a power of 950 KW. As the height increased, so did the efficiency, “says Subbaraj.” If we put high-capacity missions on this first-class site, then we could possibly become the number one site in the world. ”


Repowering – or replacing old existing missions with newer ones is the government’s goal for better utilization of wind resources – crucial if India is to achieve its RE goals. The plan, however, has yet to get off the ground, as existing transmission capacity cannot support the increased energy production and the lack of infrastructure to handle a greater load. Windmill owners further complain about the lack of incentives due to the high costs involved in the transition.

With higher wind speeds nearly 100 meters above the surface, increasing the height of existing missions is another way. But this requires more land, considering that each turbine should be positioned at a distance that is five times (or seven times) the diameter of the turbine (5D-7D concept). To date, a 1.65 MW mission requires approximately 2.5 acres of land.

Another challenge is the impact on nearby windmills – a phenomenon called the wake effect – the tendency of the wind to slow down, lose energy and become turbulent once it passes from one turbine to the other behind it. According to the developers, the cost of repowering – replacing an existing mission with a high-capacity mission is an expensive undertaking, with an amount roughly equal to what is needed to increase the height of the mission.

With further concerns about climate change, Francis Jayasurya, Director India, Global Wind Energy Council, however, says it’s important that the government re-evaluate wind speeds in different regions of the state and determine the wind potential that can drive new developers. “If they can do wind mapping and publish the data, they can guide future missions,” he added. “And, for repowering, we need to be prepared on all four scales: land, technology, network and economy.”


Favored by the seasonal monsoons, the turbines here generate a speed of 32 m / second during the high season which lasts from May to September, when 80% of wind production is recorded. While a minimum generation of 20% is recorded during October-March when the wind speed decreases.

While the developers rule out any significant changes in wind patterns over the years, concerns remain about the fluctuating monsoon winds, its accurate forecasts, and any long-term impacts of climate change in the near future. This is important as 80-90% of wind generation occurs during the monsoon months.

Windmill owners deal with changes in wind variability with windmills carrying pitch control, where pitch control allows the blades to move a few degrees each time the wind changes to keep the rotor blades in place. optimal angle to maximize production for all wind speeds.

According to meteorologists, wind speed does not undergo much variation up to at least 100 meters above the ground surface, where windmills tend to operate, and wind speed variability is believed to be mainly due to local factors such as soil warming, development of low-pressure areas, they add. However, uncertainties due to climate change need to be taken into account in the long-term stability of these projects.


With the highest installed capacity of all states, Tamil Nadu is currently at the forefront of India’s clean energy transition and could pave the way for India to meet its 2030 renewable energy targets. Progress, however, depends on how it capitalizes on the opportunities ahead, removes bottlenecks in repowering that can pave the way for a clean energy future, and helps drive the government towards its 60 GW wind power target.

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