Indonesia faces the challenge of attaining renewable energy goals and reducing carbon emissions by 29% by 2030. Despite a renewable energy goal of 23% of the national energy mix by 2025, only 14% of electricity production is projected to be generated from renewable sources by 2023. Accelerated deployment of renewable energy solutions is required to achieve these goals.

Indonesia has abundant renewable energy sources, such as hydropower, solar, and wind. Yet, a challenge arises from the difference between the electricity demand and supply patterns of these sources, which do not match throughout the day. Fluctuating energy supply patterns and variable energy demand necessitate using efficient Energy Storage Systems (ESS) to bridge the gap.

With its extensive coastline, Indonesia can potentially explore single reservoir Seawater Pumped Hydro Storage (SPHS), a variant of Pumped Hydro Energy Storage (PHES), as an alternative to solve these challenges. Similar to an enormous rechargeable battery, the reservoir in an SPHS system functions as an energy storage system. The system works by pumping up the seawater to the reservoir to store surplus energy during periods of ample supply and discharging it to generate electricity through a hydropower plant during periods of high electricity demand. This research aims to identify the ideal locations for SPHS systems in coastal areas of Indonesia. A Python GIS algorithm was developed to automate the selection process. The identified SPHS sites are then evaluated economically to ascertain their viability. The study concludes by comparing the carbon reduction potential of these systems to Indonesia's carbon emission reduction goals.

The research reveals 609 potential SPHS sites across Indonesia, with a total peak power that can be regenerated of technically potential sites of 29 Gigawatt-peak (GWp). Among these, 297 locations are deemed economically feasible, contributing a potential peak power that can be regenerated of 15 GWp. The peak electricity demand in Indonesia is approximately 44 GW, typically occurring at 8 p.m. The technical potential of SPHS promises an 11% reduction in carbon emissions from the energy sector, while the economically feasible sites could achieve a 6% reduction in carbon emissions projected in 2030.