This article is written by Rachael Taljaard, Technical Consultant at Smarter Grid Solutions
India has ambitious plans to increase the installed capacity of Renewable Energy (RE) to 175GW by 2020. Accommodating such a volume of generation capacity will have a profound impact on the power system. While the target installed capacity is the subject of many headlines, it is the existing grid itself where many of the challenges will be faced.
Regulation reform around curtailment of generation
The Renewable Energy Management Centres (REMCs) are tasked with forecasting and scheduling the output of RE, however, forecasting introduces error and leads to over curtailment. Using enhanced forecasting and scheduling can assist, but a fast-acting and autonomous control structure to respond to fast rate-of-change events will help to minimise curtailment to RE.
There have also been discussions around compensation for curtailment that still require finalisation. In Germany curtailment is compensated, and India can look to that example.
Proposed Framework for Compensation on Grid Curtailment
Up to 2%
50% of energy at contracted price
50% of energy at contracted price; Will involve review by stakeholders
Low System Demand
If curtailment is done after curtailing conventional generators up to technical minimum limits, then compensation at 50paise/kwh.
Else at power market price during the concerned time block
Source: Ind-Ra, Ministry of Power
In a recent reverse auction a 750MW PV site in Rewa bid at the lowest rate seen, which included the provision for compensation in the event of curtailment. The recommended Power Purchase Agreement (PPA) format for future wind and solar projects should also include provisions for curtailment compensation.
Displacement of traditional forms of generation
RE displaces other forms of generation, in India the main source of traditional power is coal and they cannot be shut down or curtailed below their technical minimum operating point without incurring substantial costs to ‘restart’. They also have long ramp rates which limit their flexibility. In a network where RE is prevalent flexibility is beneficial to help compensate for the variability in energy output across the day.
From a technical power system perspective, the implications include congestion through the transmission and distribution networks resulting in curtailment and the proliferation of Special Protection Schemes to protect the security of supply under contingency events. The consequence is that for system security, grid congestion and market economic reasons, curtailment of RE is a growing problem and opportunity in India.