Techno-economic comparison between generation capacity reserves and utility scale battery storage to facilitate variable renewable energy integration in Sri Lanka

At present, the Sri Lankan power system has a total installed capacity of approximately 4,087 MW by end of year 2017 with a total dispatchable capacity of 3,525 MW. The maximum demand recorded in 2017 was 2,523 MW. Sri Lanka is a country with abundance of renewable energy sources which could be utilized to generate clean energy at zero fuel cost. Currently the Sri Lankan power system has renewable capacity (except major hydro) of 609 MW, and by the Long Term Generation Expansion Plan (LTGEP) 2018-2037 of Ceylon Electricity Board (CEB), a considerable increase in integration of renewable energy into the system is projected. But integrating variable renewable energy (VRE) sources such as wind and solar energy to an islanded power system like Sri Lanka presents numerous technical and economic constraints. These constraints rise due to the inherent qualities of VRE such as intermittency of the resource, lack of inertial response for frequency regulation, high capital cost and the cost of maintaining adequate generation capacity reserves to compensate for variability and uncertainty of VRE. Therefore successfully overcoming the technical and economic barriers is essential in integrating more renewable energy in to the power system. Utility scale battery storage systems are considered as a possible solution to the variability and uncertainty of VRE, by facilitating energy storage from solar PV plants during the day and inject stored energy to the system at night. The battery storage system also can be used for ancillary services such as voltage support, frequency control and load smoothing, as well as ramp rate control in order to maintain grid stability. This study specifically explores the use of battery storag