As India moves rapidly towards its target of 175 GW of installed renewable energy capacity by 2022, it is experiencing some hiccups in integrating the new capacity into the country’s underdeveloped grid. Solar plants are being forced to curtail generation, a practice that is not only against the “must-run” status accorded to renewable energy plants by the government, but also results in huge financial losses for developers, thereby reducing investor interest in the segment.
To overcome the challenges of power evacuation and strengthen the grid network, the Ministry of New and Renewable Energy (MNRE) launched the Green Energy Corridors (GEC) programme, which is being spearheaded by Power Grid Corporation of India Limited (Powergrid). The GEC programme is aimed at strengthening power evacuation from multi-megawatt solar parks that account for 40 GW of the targeted solar power capacity. Its implementation, however, has been patchy so far, with ground-breaking for the first corridor having taken place only recently.
The GEC programme was introduced to modernise the grid network in order to enable smooth evacuation of power from renewable sources. The programme also entails network renovation and expansion to remote areas.
The GEC programme will facilitate the evacuation of power from renewable energy-rich states to other states through 765 kV and 400 kV high voltage transmission lines, a 765/400 kV substation and associated equipment. It will also enable inter-regional connectivity between the country’s western and southern regional power grids through four high voltage direct current (HVDC) terminals (two at the 800 kV level and two at 320 kV).
Powergrid was requisitioned by MNRE and the Forum of Regulators to conduct the GEC study for the identification of transmission works and investments required across the country to accommodate the renewable energy capacity being added until 2022. The study is currently under way, with specific transmission requirements identified for upcoming solar parks across various states. The total cost of the project has been estimated at $2.5 billion, of which the Asian Development Bank has pledged support of $500 million, while KfW has pledged another $500 million. Work is in progress for the inter and intra-state transmission systems. The former comprises 13 solar parks aggregating 9,220 MW of capacity across seven states – Gujarat, Madhya Pradesh, Andhra Pradesh, Karnataka, Rajasthan, Arunachal Pradesh and Himachal Pradesh – while the intra-state transmission system includes 21 solar parks with 10,780 MW of installed capacity.
Development of the transmission network for power evacuation from upcoming solar parks is currently under way in many states. Multiple high capacity corridors have been considered for development across the country. These include inter-regional corridors, which will help evacuate renewable energy from renewable-rich states to other parts of the country.
Work on the first corridor started in May 2017. The Raigarh-Pugalur 800 kV ultra HVDC (UHVDC) system will connect Raigarh in Madhya Pradesh to Pugalur in Tamil Nadu. The project is being implemented by ABB in conjunction with a consortium led by Bharat Heavy Electricals Limited. Pitamber Shivnani, president, Power Grids Division, ABB India, says, “This project will be the key to ensuring efficient integration and evacuation of renewable energy through dedicated transmission corridors and in the process provide access to energy across various load centres, considering the seasonal patterns with the back-up of the main grid. The 1,830 km link will be among the longest in the world. With a capacity of 6,000 MW, equivalent to more than six large power plants, the corridor will be able to meet the electricity needs of over 80 million people in India. The two-way link will integrate thermal and wind energy for transmission of power to high-consumption centres located thousands of kilometres away, supporting electricity demand in the south when wind strength is low, and transmitting clean energy to the north when there is excess wind generation. The project is on track and has no anticipated delays.”
The Raigarh-Pugalur line is being built at a cost of Rs 57 billion and nearly all the equipment will be supplied by ABB. The major equipment supplies include the complete UHVDC stations comprising transformers, converter valves, cooling systems, and control and protection technology. According to Shivnani, “ABB will leverage the extensive local manufacturing and engineering base in India to deliver the core HVDC technology system design and engineering as well as supply key equipment and components, and undertake commissioning and system testing, including civil works and installation work.”
The setting up of renewable energy management centres (REMCs), co-located with state, regional or national load despatch centres (SLDCs/RLDCs/NLDCs) in renewable energy-rich states, has been proposed in order to create a centralised energy management mechanism. The REMCs will be responsible for forecasting the renewable energy generation within their jurisdiction for different time horizons, real-time tracking of generation and close coordination with their SLDC/RLDC for smooth grid operation. Currently, the decentralised forecasting/scheduling approach is being followed, whereby each wind farm and solar park, with a capacity of more than 10 MW and 5 MW respectively, has to submit its schedule individually.
Further, scheduling can be done in both centralised and decentralised ways through REMCs. In the centralised scheduling approach, system operators or independent organisations forecast/ schedule generation on behalf of all the wind farms and solar parks. The centralised scheduling mechanism reduces forecasting errors as the data is aggregated from various solar plants. It also enables the use of advanced forecasting technologies for better quality and faster resolution of problems. In a decentralised system, data (static/real-time supervisory control and data acquisition) is not readily available to system operators. In centralised forecasting, too, ensemble forecasts by multiple agencies need to be aggregated as a single forecast so that the strengths of each service provider can be harnessed. As part of renewable contracts, a competitive model structure should be developed, which will help determine the fees paid to each forecast provider, based on the accuracy of the forecast.
The GEC programme has witnessed significant delays, owing primarily to bureaucratic hurdles and the lack of a push from the industry, particularly in Rajasthan, Gujarat and other solar-rich states. None of the six substations planned under the first phase of the GEC project, to be completed by 2019, has been commissioned so far. Powergrid plans to commission at least three substations, two in Rajasthan (Chittor and Ajmer) and one in Tamil Nadu (Tirunelveli) by the end of the current financial year. There is also a glaring mismatch between the number of demand centres and the available corridors. A case in point is a 1,000 MW substation at Kaythar in Tamil Nadu, which was scheduled to be commissioned by early 2017 but for which construction has not yet commenced as the independent power producers were keen to evacuate the power to Gujarat and Maharashtra, instead of to the Northeast through the planned corridor. Developers and power producers are not applying for long-term access to the central transmission utility in advance. As a result, the transmission infrastructure is not adequate to evacuate the power generated. Also, since last mile connectivity, the point of connection, between interstate and intra-state transmission lines, has to be provided by the states, and there is often a disparity in project execution, which leads to delays.
The way forward
With the construction of the first project finally under way, the GEC seems to be making some headway after the long delay. It is expected that the first phase of the GEC will be implemented in time for evacuation from the upcoming solar parks. Considering the importance of these corridors in the development of the renewable energy sector and the achievement of the 2022 target, it is imperative that the pace of work is accelerated.