Renewable energy sources, such as wind energy, are gaining a lot of traction across the world. India intends to improve the amount of wind energy integration into the national electricity system. Wind/solar energy's major drawback is its inherent changeability and source unpredictability, making it a challenging resource to dispatch.

A proposed PHS system known as Subsea Pumped Hydro Storage (SPHS) has been assessed from a techno-economic standpoint. As intermittent renewable energy sources become increasingly widespread in the electrical system, the demand for power regulation grows. Implementing energy storage in the system is one approach to balance the demand for power with the supply. This thesis looked at an idea that is a sea-based variant of the existing pumped hydro storage technique. A SPHS unit is made up of a hollow structure on the seabed that may be emptied of water using a pump during periods of low demand and high energy generation in the system, and the unit is charged at that moment. When the system requires more energy, water is permitted to flow into the tank through a turbine, creating power.

In India, a locality study of prospective areas where the PHS may be placed and operated effectively is carried out. Muppandal (Tamil Nadu) is used as a case study. When the PHES is used, a positive influence on the power system's behavior may be seen, with the degree of wind integration being raised and dispatched on demand. The generation of peak demand by inefficient and costly units is reduced, lowering the total generating cost.

The main goal of this work is to determine the Technical feasibility of a proposed SPHSP system and to evaluate Levelised cost of storage. The study will be conducted to reach out to the suitable selection of turbines and pumps and to design the concrete storage tank in such a deep-sea environment. It is observed that the maximum depth upto which the storage tank can be built is 1200m depth for 5m high wall and 1000m depth for 7m high wall. The appropriate turbine is selected based on specific speed and it comes out that Francis turbine is suitable for depth 200m to 1200m. The levelised cost of storage (LCOS) is also calculated, and it works out to be $4.53 per kilowatt hour for 1200m depth. There are different methods suggested to increase the bearing capacity of the soil and compaction grouting seems to be the most appropriate improvement method.