Mega transmission schemes planned for offshore wind energy evacuation

The National Committee on Transmission (NCT), in its next meeting scheduled later this month, will deliberate on mega transmission schemes for power evacuation from wind farms offshore Gujarat and Tamil Nadu.

Offshore wind energy potential of around 30 GW each has been indentified off the Gujarat and Tamil Nadu coasts. Though India yet does not have installed offshore wind energy capacity, efforts are on to commission at least one 500-MW project in Gujarat by March 2028 and a similar sized project in Tamil Nadu by March 2029.

In the imminent NCT meeting, two schemes – one for Gujarat (500 MW) and one for Tamil Nadu (1 GW) – with a total envisaged outlay of Rs.18,371 crore will be discussed.

These two transmission schemes are aimed at creating power evacuation infrastructure to match the commissioning dates of the upcoming offshore wind farms.

Among other things, NCT will also deliberate on the mode of implementation – whether TBCB or RTM – of these two schemes. However, it is important to note that a meeting held under the then Union Minister of Power and New & Renewable Energy in June last year, had recommended that Power Grid Corporation of India Ltd (PGCIL) be awarded the initial schemes on RTM basis whilst adopting the TBCB modality for future schemes. The Union Cabinet, on as recently as June 19, 2024, also approved the proposal of PGCIL developing the initial schemes on RTM basis.

A total of 10 GW of offshore wind energy evacuation has been envisaged – 5 GW in Gujarat and 5 GW in Tamil Nadu. In the ministerial meeting of June 2023, it was proposed that the initial 2 GW (1 GW in Gujarat and 1 GW in TN) would be developed by PGCIL under the RTM route while the remaining 8 GW (4 GW in Gujarat and 4 GW in TN) would come up under the TBCB philosophy.

 

Gujarat

The Gujarat scheme is estimated to cost Rs.6,886 crore, including Rs.2,186 crore for the onshore infrastructure and the remaining Rs.4,700 crore for the offshore facilities. This project will be officially referred to as “Transmission System for Offshore Wind Zone Phase-1 (500 MW VGF off the coast of Gujarat for Subzone B3)”. The major elements of this scheme will include the new Mahuva onshore pooling station (GIS), a 400kV line connecting this pooling station to the under-construction Vataman pooling station, and an offshore pooling station termed as “B3-OSS-1”. This project will involve 45 km of cabling that will include 35 km subsea and around 10 km underground.

 

Tamil Nadu

Termed as “Transmission System for 1 GW Offshore wind farm (Phase-I) in Tamil Nadu,” this is the larger of the two schemes with an envisaged cost of Rs.11,485 crore that includes Rs.1,193 crore for the onshore system and Rs.10,292 crore for the offshore facilities. There will be two offshore substations, while the onshore pooling station is planned to come up at Avaraikulam in Tirunelveli district. ISTS connectivity will be established with the existing Tuticorin pooling station.

 

Technical parameters

Currently, it has been tentatively agreed upon that operating voltage of the substation and the transmission lines would be kept at 220kV. Substation transformers will have configuration of 2×315 MVA, while subsea cables will be of 2×300 MVA capacity.

 

Schedule of offshore wind farms

As discussed above, a total of 10 GW of offshore wind farms have been planned, including 5 GW each off the Gujarat and Tamil Nadu coasts. The initial development will involve Central government assistance in the form of viability gap funding (VGF). The tentative schedule of the capacity build-up is as follows:

• 500 MW off-Gujarat by March 2028 (VGF)
• 500 MW off-Tamil Nadu by March 2029 (VGF)
• 4 GW off-Tamil Nadu by March 2030 (non-VGF)
• 4 GW off-Gujarat will be tendered based on response to #3 (non-VGF)

The two transmission schemes discussed in this story includes 500 MW (VGF) in Gujarat; and 500 MW (VGF) plus 500 MW (non-VGF) in Tamil Nadu.

 

Cabinet approval

On June 19, 2024, the Union Cabinet approved the VGF scheme for offshore wind energy projects at a total outlay of Rs.7,453 crore, including an outlay of Rs.6,853 crore for installation and commissioning of 1 GW of offshore wind energy projects (500 MW each off the coast of Gujarat and Tamil Nadu, #1 and #2 in the above list), and grant of Rs.600 crore for upgrade of two ports to meet logistics requirements for offshore wind energy projects. The VGF support from the Government will reduce the cost of power from offshore wind projects and make them viable for purchase by discoms. These offshore wind energy projects will be set up by private developers, selected through a transparent bidding process.

Also read: Mega Transmission Projects See Slowdown In FY19

Featured photograph (source: Siemens) showing an offshore wind farm substation is for representation only.