Wind turbines along the Kadayanallur-Tenkasi state highway road in Tamil Nadu.
| Photo Credit: Jothi Ramalingam. B

The story so far: Tamil Nadu, which is a pioneer in wind mill installations, has wind turbines that are over 30 years old. The Tamil Nadu government released the “Tamil Nadu Repowering, Refurbishment and Life Extension Policy for Wind Power Projects – 2024” in August this year. However, wind energy generators have opposed the policy, approached the Madras High Court and got a stay. They have demanded a policy that will “promote wind energy generation”.

Also read: Wind energy generation in Tamil Nadu expected to drop slightly

What is the wind energy capacity and potential in India?

The National Institute of Wind Energy (NIWE) says that India has wind power potential for 1,163.86 GW at 150 metres above ground level, and is ranked fourth in the world for installed wind energy capacity.

At 120 metres above ground level, which is the normal height of wind turbines now, the potential is 695.51 GW, including the 68.75 GW from Tamil Nadu. Only about 6.5% of this wind potential is used at the national level and nearly 15% in Tamil Nadu. Gujarat, Tamil Nadu, Karnataka, Maharashtra, Rajasthan, and Andhra Pradesh are the leading States for installed wind energy capacity, collectively contributing 93.37% of the country’s wind power capacity installation. Tamil Nadu has seen the installation of wind turbines since the 1980s, and today it has the second largest installed wind energy capacity with 10,603.5 MW, according to data available with the Ministry of New and Renewable Energy (MNRE). Of the 20,000 wind turbines in the State, nearly 10,000 are of small capacities, that is less than one MW.

How are wind turbines maintained?

Wind turbines that are more than 15 years old or have less than 2 MW capacity, can be completely replaced with new turbines, which is known as repowering. They can also be refurbished by increasing the height of the turbine, changing the blades, installing a higher capacity gear box, etc., to improve the energy generated. These can be done for standalone wind mills, or a group of wind mills owned by multiple generators. When wind energy generators take up safety measures in the old turbines and extend its life, its called life extension.

The MNRE first came out with a “Policy for Repowering of the Wind Power Projects” in 2016 and based on consultations with stakeholders, released the “National Repowering & Life Extension Policy for Wind Power Projects -2023”. The NIWE estimates the repowering potential to be 25.4 GW if wind turbines of less than 2 MW capacity are taken into consideration.

What does repowering and refurbishing entail?

Wind energy generators say that when turbines were installed in the 1980s, potential wind sites were mapped and the mandatory gap required between two wind mills were determined based on the technology available then. All the turbines were in the sub one MW category. Over the years, the wind mill manufacturing sector has matured and technology has evolved. Habitations have come up between wind sites, posing new challenges, and wind energy evacuation and transmission infrastructure close to the wind sites needs to be strengthened to match the generation.

Sources in the wind energy industry point out that a 2 MW wind turbine is usually 120 metres high and requires 3.5 acres of land. It can generate upto 65 lakh units of power. A 2.5 MW turbine, which is available in the market now, is 140 metres high and can generate 80 lakh units. It requires five acres. So, when an existing wind turbine is to be repowered by replacing it with a high capacity turbine, more land is required.

Further, at Aralvaimozhi in Tamil Nadu, a high potential wind site, the 48 MW installed capacity now is made up of mostly 250 KW turbines and the potential at the site is for 100 MW. A project to have three sub-stations of 230 KVA each at ₹800 crore was sanctioned six years ago and is yet to take off for multiple reasons. In Tamil Nadu, wind mills installed after 2018 do not have banking facility. When a turbine is repowered, it will be treated as a new installation and the generator cannot bank the energy generated. This impacts the financial viability of the project, say the sources.

What is the way forward?

Among the wind energy generating States, the repowering potential is the highest in Tamil Nadu with over 7,000 MW of installed capacity that can be replaced or refurbished. If the small turbines are repowered or refurbished, the contribution of wind energy to total energy consumed during the peak windy seasons can go up easily by 25%, says wind energy consultant A.D. Thirumoorthy.

While there have been generators which have replaced turbines in the past without government support, the policy itself does not promote wind energy generation, claim the generators. It should look at challenges on the field and consider how the wind energy potential can be harnessed fully by the generators. “No industry or energy generator will want to invest in a project that is not financially viable. The repowering policy is not commercially beneficial,” said a textile mill owner in Coimbatore who has invested in wind energy.