India will soon get to see windmills generating power from the sea as the Centre has floated tenders to set up offshore windmills along the coasts of Tamil Nadu and Gujarat.

The Ministry of New and Renewable Energy has floated tenders for offshore wind power at Dhanushkodi in Tamil Nadu and in three coastal zones in Gujarat. The three zones are Saurashtra, South Gujarat and Gulf of Khambhat coastlines.

The ministry has called for bids for 4000 MW (mega-watt) or 4 GW (giga-watt). The tender document says that the selection of developers will be through an international competitive bidding process. Unlike onshore wind power mills where the capacity is less than 1MW, offshore wind power mills will have a minimum capacity of 13MW. The bidder offering the highest lease fee per sq km of sea bed area would be declared as the winner for allocation of the project. Evacuation and transmission of power from offshore pooling substation (PSS) to onshore transmission will be provided free of cost for all offshore wind capacities that will be bid out up to 2029-30.

As this is the first time India will have offshore windmills, there is no experience in setting up of these windmills and therefore companies from either UK or Denmark will be investing in Tamil Nadu and Gujarat.

The scheduled date for commissioning of the full capacity of the project shall be 48 months from the effective date of the agreement.

"National Institute of Wind Energy (NIWE) or its designated agency will issue a letter of consent to the selected developer for carrying out the offshore wind measurement and other surveys after obtaining requisite clearances from the concerned ministries according to the national offshore wind energy policy," said the official document.

The grid connectivity and long-term open access to the grid will be in the scope of the offshore wind power developer and the energy generated will be consumed in captive mode or sold to third parties under open access framework or sold through power exchange.

The developer shall set up the offshore wind projects, including the offshore pooling station at the voltage level of 220kV (kilovolt). Metering for the purpose of energy accounting shall be done at respective onshore pooling stations, said the ministry.

The minimum capacity for acceptance of first part commissioning shall be 100 MW or 50% of the allocated project capacity, whichever is lower. Projects with capacity more than 500 MW can be commissioned in parts of at least 200 MW each, with the last part being the balance capacity.

As per a study done by the Gujarat state government, the 1,600 km-long coastline offers a potential of 32GW to 35GW of offshore wind power generation.

With more than 18,000 MW capacity of onshore windmills, Tamil Nadu is the wind power capital in the country. But the onshore wind power is seasonal and it is available only between May 15 and September 15.

A similar study done by Tamil Nadu Generation and Distribution Corporation (Tangedco) has found that the state will get offshore wind between June 15 to January 15, and that too round the clock without any break in between.

"On behalf of Tangedco we conducted a study in and around Dhanushkodi and Palk Strait areas. The study says that Tamil Nadu will get offshore wind between June and January and unlike the UK or other European countries, where the offshore wind power is discontinuous. We will get uninterrupted power supply," said Tangedco chairman Rajesh Lakhani.

In European countries, the offshore wind power is continuous but at times they have to depend on other power sources as the wind suddenly stops. "In Tamil Nadu, even during the onshore wind power season (between May 15 and September 15), we have our thermal units on standby as suddenly wind power generation declines. But with offshore wind power, we are confident of not having any thermal unit on standby for continuous power supply," said Lakhani.

The Palk Strait is more or less a wind tunnel. "It is only through the Palk Strait that wind passes through between June and January, and thus the Strait acts as a wind tunnel," he said.

Till now, Dhanushkodi used to be a ghost village as the entire place was destroyed in the 1964 cyclone. But in recent times, Dhanushkodi is slowly limping back to life with a proper road being laid between Rameswaram and Dhanushkodi. “It is slowly becoming a tourist place and all those who visit Rameswaram are visiting Dhanushkodi as there is a good road. Small shops selling conch, sea shells have come up," said a Tamil Nadu tourist department official. A few fishermen families have also settled in the town.

"Dhanushkodi is the best offshore for evacuating wind power and the wind power projects will have a bigger capacity unlike onshore wind power mills. The offshore wind mills will be set up inside the sea up to 30 km," said a Tamil Nadu tourist department official.

"The offshore wind power projects will not use any concrete to set up the windmill. Instead, the projects will use steel which will not corrode. Thus there is no danger to any marine animals," the official added.

An offshore wind energy test facility is likely to be set up by the NIWE (National Institute of Wind Energy, Chennai) at Dhanushkodi. This is regarded as the first such project in the Asia-Pacific region. "The mast in offshore wind will have to be at least 100 meters, and another 50 meters will be under the sea. For this we need to have a pile foundation and it will cost more than 70% of the total cost," a NIWE official said.

Funded by the Government of India, this project will come up in two years and will involve the setting up of two wind turbines of over 8 MW capacity, in order to perform studies and collect data on the feasibility of large-scale projects of this kind. A total of ₹350 crore will be spent towards this testing facility. Such a facility is required to test turbines for specific Indian conditions, as against European conditions, where most tests are conducted by default. Notably, wind turbines from Europe don’t perform at their optimum levels in India, given the difference in conditions.

"We will be setting up an offshore wind energy test bed and research centre at Dhanushkodi. We have got 75 acres of land allotted for the project. Generally, turbines are tested only in Europe and their wind profile is different. Testing here in Indian conditions will give us confidence to re-design the turbines for best performance in Indian conditions," said the official.

National Institute of Wind Energy (NIWE)

For the first time, India will have windmills in sea soon; massive 13MW mills planned