Challenges to Grid integration of RENEWABLE ENERGY IN INDIA
India has witnessed increasing capacity additions in renewable energy (RE) with an installed capacity of close to 22 GW for solar and 34 GW for wind as on March 31, 2018. The achievement of the planned capacity shall have the country’s task cut out in terms of planning the transmission infrastructure and managing the integration of the laid-out capacities with the grid, which indeed is a challenge. The transmission infrastructure is still a fragile link observing additions far from what was envisaged to evacuate the kind of green power injected in the grid. Although, the central government has embarked upon the Green Energy Corridor (GEC) initiative and the integration of storage systems on grid scale is envisioned, there are challenges to setting up the evacuation infrastructure. As observed, the biggest challenge is to guarantee that transmission systems are in place before the renewable projects are ready, since executing transmission projects takes up to five years as compared to the 12–18 months in case of solar projects.
DIFFERENCE IN NUMBER OF DEMAND CENTRES AND THE AVAILABLE CORRIDORS FOR RE
There is some incongruity in the number of demand centres and the available corridors for RE due to the lack of an effective plan to design a dedicated infrastructure for RE evacuation. For instance, the 1 GW substation project at Kayathar in Tamil Nadu, which was scheduled to be commissioned in early 2018 could not be commissioned on time because independent power producers are more inclined to evacuate the power to Gujarat and Maharashtra which have adequate demand centres as compared to the north-eastern states through the planned corridor. This is because there are limited demand centres to consume the power and less likelihood to earn premium under open access in the north-eastern states. However, the GEC is being established to evacuate power from large scale renewable energy systems, therefore are being implemented in states where RE resource is huge and large RE projects are coming up. The excess power being generated in these states are being transmitted to other states through the national grid. The grid infrastructure to connect to the demand centres is already in place and any strengthening required is done by the States.
In the case of solar power, distance is a major constraint for the planned long-range transmission due to the power purchase agreements (PPAs) under the auctions of solar power. Six states in the western and southern parts account for 80% of the country’s installed solar capacity but only 38% of the power demand, and at present India lacks afordable storage facilities for RE power. However, on a positive note the excess power being generated in these states are being transmitted to other states through the national grid, i.e., Inter State Transmission System.
INADEQUACIES IN GRID INFRASTRUCTURE
Adequate transmission networks for upcoming RE projects have been planned and are under approval. These would be set up as and when Stage-II connectivity is received from developers so as to match the grid infrastructure with RE generation and to not keep the grid idle. But there is a need to address issues of the existing grid infrastructure. In India, several electrical parts of the country are unevenly connected to the national grid in order to optimally evacuate large wind farms or solar parks, which otherwise demand the installation of the entire infrastructure. Although the GEC programme is aimed at evacuating power from renewable-energy-rich states to other states through 765 kV and 400 kV high-voltage transmission lines, but there have been delays and infrastructural development does not match the pace of tenders coming out.
In some states, tenders are released without consulting the respective state electricity regulatory commission (SERC); as a result, when PPAs go to regulatory commissions for approval, they get held up because the SERC cites a lack of transmission infrastructure.
BACKING DOWN OF WIND POWER IN WIND-RICH STATES
In spite of the must-run status for renewables, given their near-zero variable/marginal costs and higher ranking in the merit order, there have been some instances of backing down of renewable power, especially wind power. Ideally, such generation cannot be backed down except in the case of grid contingency. The Indian Wind Power Association has noted that the Tamil Nadu State Load Dispatch Centre (TNSLDC) has been backing down 50% of the wind generation in the state, as ‘variation in wind power endangers the grid’. (CERC, 2016). This is causing financial losses for wind generators. In 2015–16, there was an apparent backing down of 5000 MU of wind power. At a tariff of
3.5/kWh, this adds up to a potential loss of1,650 crore. At present, there is no provision for compensation for ‘deemed generation’ when wind power generators are available but are backed down by grid operators.
Grid operators and generation owners face major technical issues, such as
intermittency (which is an uncontrolled variability) and location dependency. The three distinct issues that affect the grid integration of wind and solar energy are:
- Variability of resources: Power plant operators cannot control the wind and solar output because wind speeds and solar intensity vary dramatically, affecting power output. To balance the supply and demand on an instantaneous basis, there should be additional energy input as well as peripheral ancillary services, such as voltage and frequency regulation.
- Unpredictability: The availability of wind and solar energy is unpredictable to an extent. Electricity is only produced when the wind is blowing, and the presence of sunlight is crucial for PV systems to work. Systems that use advanced forecasting technologies can manage unpredictability. The availability of standby reserves to supply power when the renewable sources provide less power than predicted and the presence of dispatchable load to soak up excess power in case of renewables producing more power than predicted are parts of technological systems.
- Location dependence: Quality wind and solar resources that are most feasible for renewable energy generation are, unfortunately, based only in specifc locations, and unlike in the case of various fossil fuels, such as coal, oil, gas or uranium, transporting them to a generation plant that is grid optimal is not possible. Generation is co-located with the resource, and the place where the power is ultimately used is ofen far from these locations. Connecting wind and solar energy resources to the grid involves the use of new transmission capacity. Moreover, transmission costs are especially high for ofshore wind resources, ofen utilizing technology not employed in land-based transmission lines.
Source: Mr Jonathan Donald Syiemlieh is Associate Fellow at the Centre for Resource Efficiency & Governance, TERI, New Delhi.