Reservoir Thermal Energy Storage (RTES) has been shown to be economically attractive for data centre cooling only at hyperscale in temperate climates, where it displaces an expensive chiller-based baseline; at smaller scales a cheap passive dry-cooler or cooling-tower comparator makes it uncompetitive. That conclusion is conditional on a climate in which cheap passive cooling exists. This paper tests whether it survives transplantation to a tropical monsoon city where it does not. Three cooling configurations for a representative 10 MW information-technology load data centre in Mumbai—a conventional water-cooled chiller with cooling tower, a hybrid chilled-water thermal storage retrofit, and a geothermal RTES-integrated hybrid system with three well doublets at 320 m in Deccan basalt—are evaluated on identical load and climate boundary conditions over a thirty-six month panel. The assessment covers annual cooling electricity and power usage effectiveness, cooling-tower water consumption and water usage effectiveness, carbon dioxide emissions at the published Indian grid emission factor of 0.727 t/MWh, a discounted-cash-flow levelised cost of cooling at an 8 % real discount rate over a 15-year life, and a ten-parameter one-at-a-time sensitivity analysis. The geothermal configuration reduces annual cooling electricity by approximately 35 % and cooling-tower water consumption by approximately 31.6 % against the conventional baseline, with a proportional emissions reduction of the order of 3,455 t CO₂ per year. Levelised cost of cooling falls to ₹1,880/MWh against ₹2,196/MWh for the conventional baseline and ₹2,044/MWh for the hybrid store, and the incremental capital cost of ₹10.64 crore is recovered in 3.2 years undiscounted or 3.8 years discounted. Sensitivity is dominated by electricity tariff, followed closely by aquifer transmissivity; the grid emission factor has no influence on cost. The reversal relative to the temperate reference case is attributed to the absence of a cheap passive comparator in Mumbai, which makes the 10 MW site structurally closer to the hyperscale chiller-dependent case than to its own scale class. A four-phase, gated deployment framework is proposed.

Md. Danish Qureshi, Chaitanya Shrivastava, Raghavendra, "Energy, Water, Environmental and Techno-Economic Assessment of a Geothermal RTESIntegrated Hybrid Chilled-Water Cooling System for a 10 MW Data Centre in Mumbai" International Journal of Scientific Research and Engineering Development, V9(5): Page(369-380) September - October 2026. ISSN: 2581-7175. www.ijsred.com. Published by Scientific and Academic Research Publishing.