A system and method for the thermal management of a battery-based energy storage is described. One embodiment includes a thermal management system for a battery-based energy storage system, the thermal management system comprising a residual heat source, such as a geothermal heat source, and a battery-based energy storage system thermally connected to the residual heat source The thermal connection between the energy storage system and the residual heat source may be direct (i.e., the energy storage system may be adjacent to, partially located within, or fully located within the residual heat source) or indirect (e.g., the energy storage system and residual heat source may use a heat conduit to transfer heat). In embodiments using a heat conduit to transfer heat, the thermal management system may further comprise a control system for controlling the circulation of a fluid in the heat conduit in order to regulate the temperature of the energy storage system.