Curtailment of solar and wind power: Five key strategies which India can learn from different countries experiences on curtailment
India’s renewable sector has been grappling with various issues but one of the overarching problems present in this industry is of curtailment of solar and wind power. While the current installed capacity of solar and wind projects accounts for about 83 GW, it is expected to reach to the tune of 160 GW by 2022. Given the intermittent nature of solar and wind power, increasing curtailment in view of grid stability has a much greater adverse impact in achieving the RE targets in India. The issue of curtailment has been in the centre of legal battles with cases like Adani Solar v SECI, wherein the renewable energy developer is facing losses due to the generation loss faced because of the curtailment due to cited “technical reasons” instead of commercial reasons even after being given the “Must run” status by the central government. But as the renewable penetration in the grid increases and they become a major source of grid power supply, the “Must Run” status will have to be removed for renewables as it would no longer be viable to have the compulsory ‘must run’ for the renewable power generation. Curtailment will become the reality for every solar or wind developer and they need to realize that the grid infrastructure cannot be made to accommodate to absorb 100% of the power they produce. The reality is that here onwards according MUST RUN status given to renewables will not be economical. Rather than a considering curtailment as a problem, it should be a solution for grid balancing. The system operator should be able to control the spin of wind turbines and manage the grid and also throttle the solar inverters by tweaking the MPPT set-points. The large-scale deployment of solar and wind capacities in Indian electricity grid shall be only possible if we allow a reasonable curtailment of solar and wind power to manage the grid stability. This article talks about five different approaches to handle the issue of curtailment. May be a combination of these approaches’ is a viable solution to the policy makers to address the curtailment.
- Compensating the loss of revenue to renewable energy developer
In this system, the solar and wind power generator does not have to face any loss of income due to generation loss as the loss incurred by the developer is compensated by valuing the generation loss and providing the same amount to the renewable energy developer. This leads to the grid achieving the stability through the curtailment yet the power generator not facing revenue losses due to the generation loss. This approach is being followed in Canada, where the solar and wind energy supports almost 18% of total energy consumed and is constantly on rise and thus to make the investment viable for the solar and wind power developers and improve the grid stability the system in Canada has accepted that with the future being the renewable energy, curtailment has become a solution rather than the problem for providing grid stability. Canada thus has a system in place to compensate the solar and wind power developers for the generation loss resulted through curtailment.
2. Efficient scheduling and forecasting
Efficient forecasting with improved application of automatic generation control of solar and wind power dispatch makes the scheduling for solar and wind power much more efficient which further leads to a decrease in curtailment of and makes its usage even more sufficient. This approach is being implemented in China which has a total capacity of 790 GW of renewable energy in order to have a better scheduling and decrease the amount of curtailment. In India, the grid operators have recently made the scheduling of the solar and wind power projects mandatory. Recently CERC has amended the DSM regulation 2015, and has made it mandatory to al the interstate solar and wind power projects to forecast their generation schedule for day ahead and week ahead period. Subsequently many states have also issued the guidelines for scheduling and forecasting of solar and wind power projects.
3. Strong Interconnections with the neighbouring systems and well-functioning international markets.
Curtailment is essentially done to bring stability in the grid in case when the electricity is over produced. One of the methods to address this problem is to have strong interconnections to neighbouring systems and well-functioning international electricity markets. This leads to there being a market for electricity where one state can sell the electricity to another in case there has been an over production of electricity. This approach is being practised in Denmark where there are strong interconnections to the neighbouring systems and well-functioning international electricity markets. This leads to the excess generation from the areas of Denmark being transmitted to its neighbouring states. Also, negative price signals are used during the times when the electricity is over produced. Another feature to this approach practised by Denmark is the sale of electricity at the wholesale market. India also practices this this with its neighbours like Nepal and Bangladesh however India needs stronger interconnections and better functioning international energy market. There is a little coordination among the Discoms/SLDCs in the states, which leads to grid inefficiencies. There is a greater role required by the NLDC to manage and coordinate with the SLDCs to absorbe larger solar and wind capacities.
4. Transparency on reasons for which curtailment can be issued.
To reduce the curtailment of renewable energy, it is necessary to have the reasons for curtailment specified very clearly instead of a grey area everything under which could be considered reasons for curtailment. The specified reasons for curtailment increase the transparency in system while also reducing the curtailments. This approach is being practised in Ireland which has set up a unique system in place for addressing the issues of their energy sector. They have a distinction between a system wide (curtailment) and local network (constraint) issue. While the curtailment can be issued only if one of the five conditions, that are, system stability, operating reserve, voltage control, morning load rise, and exceedance of SNSP limit are met. The constraint can happen a few times during the day due to network limitations which is being currently addressed through various schemes in the country that are aimed at reducing the constraints. This leads to a decrease in curtailment as the reasons for the curtailment have been specified and expressed very clearly leaving the offtaker no scope for any unnecessary curtailment for the renewable power India currently does not have clear and specified reasons under which the curtailment of renewable energy can be performed rather the reasons for curtailment in India are very vague and broad terms that come under the umbrella of technical and commercial reasons and thus is easily being misused by the offtaker.
5. Revamp of Transmission and energy storage infrastructure
Transmission congestion and lack of energy storage capacity in the grid is being considered as one of the major factors which leads to curtailment of the wind and solar resources. Introduction of energy storage options in the grid infrastructure, can lead to time shifting of peak generation congestion in the grid and provides the grid flexibility in handling the large variations in the solar and wind power peaks. US, Germany, and Australia have opted front of the meter energy storage to accommodate larger penetration of renewables. A majority of US utilities are considering energy storage along with renewables as an integrated project. As per recent Woodmac’s report US will deploy energy storage capacity of the order of 365 GW by 2030. In India also some of the upcoming tenders of SECI are considered in terms of renewables with energy storage to address the issue of curtailment. Recently SECI has awarded 400 MW RE capacity to Renew power as a part of round the clock (RTC) renewables, where the developer will dispatch solar, wind and energy storage hybrid capacities to meet the criteria of supply of power during the peak hours. This initiative will be able to tackle the issue of intermittency at the point of generation on behalf of the RE generator.
As Indian RE capacity is to double by 2022, there is a challenge to handle the intermittency of the solar and wind power generation. There is no single way to address this issue of curtailment, however a mix of multiple approaches in a coordinated way will be the best solution. There is a need to model the Indian grid with multiple interventions and analyse how a combination of these approaches will be adopted in handling the larger penetration of solar and wind capacities in Indian electricity grid.