Replacing Old Windmills

THOSE WHO TRAVEL by the National Highway from Tamil Nadu’s Tirunelveli town to Kanyakumari see something unusual. After a while, lush green paddy fields and coconut trees make way for thousands of wind mills on the horizon for kilometres on end starting from Valliyoor, a number of them with mesmerising floriculture fields. Most of these were installed 20-30 years ago to tap strong winds from the Arabian Sea wafting through the mountain pass.

Developed in 1986 by Tamil Nadu Energy Development Agency (TEDA) on behalf of its corporate clients from across the country, the Muppandal village in Kanyakumari district is known for being India’s largest operational onshore wind farm. Almost one-fourth of the country’s wind energy capacity is located in these areas spread across Tirunelveli, Thoothukudi and Kanyakumari.

There’s a plan to replace these old windmills with larger ones with two-three times their current generation capacity. In mid-October, the Ministry of New and Renewable Energy unveiled the draft ‘National Repowering Policy for Wind Power Projects – 2022’, based on feedback from a similar draft policy outlined in August 2016 to facilitate a framework for repowering old windmills.

It might also pave the way for replacing about 5,000MW (or 5GW) of outdated and low-yielding wind fields across the country. Industry experts say the plan faces challenges, since the policy has to address several issues, including handling of dismantled towers and machines, difficulty in replacing old wind mills, etc. The objectives of the repowering policy are optimum utilisation of wind energy resources by maximising energy (kWh) yield per sq.km. of the project area while utilising latest onshore wind turbine technologies. The move is expected to kickstart investments worth ₹40,000 crore (including cost of acquiring and dismantling old plants) over three-five years, nearly 3x the average annual wind power capex seen in past four financial years, according to an analysis by Crisil Ratings.

Reason to Repower

India started harnessing wind power in late eighties and as on August 31, 2022, installed wind power capacity in the country stood at 41.4GW. Over the years, wind turbine generator (WTG) technology has evolved and individual rated capacities of wind turbines increased from sub-MW scale to multi-MW scale. In November last year, Adani New Industries commissioned India's largest WTG at Mundra in Gujarat, 200 metres tall, with generating capacity of 5.2MW.

Compared to such new generation machines, most of the wind turbines installed in India up to 2000 are of sub-MW capacity and at sites with high wind energy potential. Most old wind turbines have already completed their design lifespan while some are nearing the end. Also, these machines have lower hub heights (30-60 metres) in comparison to hub heights of 120-140 metres installed these days. The lower hub height wind turbines are not able to harness higher wind speeds available at higher hub heights. The plan is to repower these older, smaller wind turbines with bigger and higher efficiency turbines in order to optimally utilise wind energy resources available at respective sites.

The National Institute of Wind Energy estimates repowering potential of the country at just above 25GW (25,000MW) considering the sub-2MW wind turbines spread across Tamil Nadu, Maharashtra, Karnataka, Gujarat, Rajasthan, Madhya Pradesh, Kerala and Andhra Pradesh. Of these, 1.610GW capacity is below 0.5MW, mostly in Tamil Nadu (1.181GW). Machines with capacity between 0.5MW and 1MW are around 8.280GW and most of these are in Tamil Nadu (2.919GW), Rajasthan (1.192GW), Maharashtra (1.068GW) and Gujarat (1.457GW). Machines with 1-1.5MW capacity are about 6.449GW, mostly in Tamil Nadu, Gujarat and Maharashtra. Machines with capacity between 1.5MW and 2MW are about 9.067GW and of this, 1.473GW is in Tamil Nadu. In total, 4.1GW capacity in Tamil Nadu is sub-2GW capacity, while 1.311GW in Maharashtra, 1.508GW in Gujarat and 1.231GW in Rajasthan can be replaced with higher efficiency machines. The National Institute of Wind Energy also plans to come up with a repowering potential map of the country considering below 2MW capacity wind turbines.

“This may lead to replacement of 5GW of old windmills with new wind power plants with 2x more generation ability. Their viability is also better because such projects can generate double-digit returns at tariffs of ₹4 per unit for incremental capacity. Such a tariff can attract customers through open access, because their average power purchase cost is ₹4-5 per unit (net of cross subsidy and transmission charges),” says Ankit Hakhu, director, Crisil Ratings.

The repowering plan will work around standalone projects (a single or group of wind turbines owned by a single entity) and aggregation projects (a group of wind turbines owned by multiple owners with shared common infrastructure). Wind repowering project aggregators (WRPA) will also have the responsibility of decommissioning of existing assets, removal and lawful disposal of all scrap from the site, including disposal of wind turbine blades.

“The policy provides clarity on extending eligibility of older machines from 1GW to 2GW to be repowered, on sale of incremental generation under the open access route and aggregation of projects (helping pool contiguous land parcels/ projects),” says Varun Marwaha, associate director, Crisil Ratings.

Wind turbine generators with capacity of 1 MW and below would be eligible for repowering, and wind farm/turbine undergoing repowering would be exempted from not honouring the power purchase agreement (PPA) for non-availability of generation from wind farm/turbine during the period of execution. Captive users will be allowed to purchase power from the grid during the period of execution, on payment of charges determined by the regulator.

In case of power being procured by state discoms through PPA, power generated corresponding to the average of last three years prior to repowering would continue to be procured on the terms of the PPA in force, and the additional generation would be purchased by discoms at feed in tariff (FIT) at the time of commissioning of the repowering project. FIT refers to the payment made to households or businesses generating their own electricity through the use of methods that do not contribute to the depletion of natural resources, proportional to the amount of power generated.

Incentives for repowering investment are an added attraction. "Concessional interest rate offered by the Indian Renewable Energy Development Agency (IREDA) over and above interest rate rebates available to new wind projects and accelerated depreciation (AD) and generation based incentive (GBI), also made available to repowering projects, will boost investments in the sector,” says D.V. Giri, secretary-general, Indian Wind Turbine Manufacturers’ Association.

Capital expenditure per MW will be higher for repowering than greenfield projects because developers acquiring old wind sites would likely pay a premium and also incur dismantling expenses of ₹80 lakh to ₹1 crore per MW. While generation will increase by 200-300%, the projects may still need higher tariffs (₹4 per unit) than the recently discovered bids of ₹3 per unit to generate double-digit returns.

Commercial and industrial customers will find ₹4 per unit tariffs lucrative compared with grid tariffs of ₹7-8 per unit in Gujarat and Tamil Nadu. “Developers could prefer repowering than setting up greenfield solar or wind capacity because the risks would be lower given the proven track record (in generation) of existing wind sites. Additionally, evacuation infrastructure would already exist, including right-of-way and feeders at grid substations,” according to the Crisil analysis.

Hurdles to Cross

Industry sources point out repowering with higher machines has many hurdles to cross.

One prime issue to be addressed relates to how the country is going to deal with the discarded machines, which is an environmental issue. Many old machines have gearboxes, which use oil, and seeping of this oil into the ground is an environmental concern.

“The policy, when it takes final shape, needs to address several issues, including availability of large and modern turbines, how to handle scrapped machines, how to transport machines to the site, evacuation infrastructure etc,” says P.K.C. Bose, vice chairman and managing director, Enercon India, the Indian arm of German wind turbine major Enercon GMBH.

Another problem is that wind mills are located in hubs, and land is owned by different companies. Right of way and dismantling may face issues and legal battles from neighbours, since everyone may not be interested in investing in new machines. Besides, new machines will have large and long blades of above 100 meters and transportation of these machines from factories in the hinterland to sites far away will be a big challenge.

Fragmented ownerships and long-term PPAs with special requirements will be another challenge. Raw material shortage for machines is also a factor. Take the case of blades, which weigh about 20 tonnes. Over 65% of the blade is glass and resin. Carbon fibre is used to make this intricately complex product, a mesh of complex technology. Many parts for the machines are imported and current capacity is for around 1,50,000 MW, and to meet the requirement for large capacity addition, special glass and related capacity needs to be doubled, say sources.