Geothermal District Heating Using Centralized Heat Pumps and Biomass Peakers: Case-Study at Cornell University

As part of the university’s commitment to become carbon-neutral by 2035, Cornell University is researching and developing a geothermal deep direct-use system to provide baseload heating for its main campus in Ithaca, NY. The term Earth-Source Heat (ESH) was adopted to distinguish Cornell’s approach to extract thermal energy from rock formations 2.5 to 5 km deep at low temperatures. Over the last several years, we have characterized the local subsurface using well log analysis and bottom hole temperature interpretation, and tools such as gravity, aeromagnetic and seismic surveys. We investigated optimal integration of ESH into the existing district heating network. Promising sedimentary formations have been identified with temperatures in the range 70–90°C, and a fractured basement target (90–100°C) has been considered. Reservoir simulations indicate acceptable thermal drawdown over a 30-year lifetime. Enhanced Geothermal System technology may be applied to increase formation permeability. Techno-economic modeling results show hybridizing the ESH with centralized heat pumps enhances the performance and results in an attractive levelized cost of heat on the order of $5/MMBTU. Biomass is considered to produce renewable natural gas that on an annual basis covers the campus peaking heating load. Currently, a borehole is being designed to obtain cores from target formations and in-situ measurements of critical parameters. The ESH project at Cornell serves as a regional demonstration site, which, if successful, could accelerate the development of geothermal district heating in other communities in the northeastern U.S., where subsurface temperatures in the range 50–100°C are widespread. In the northern tier of the U.S., heating loads are high and dominated by fossil fuel combustion, and contribute significantly to statewide greenhouse gas emissions. Geothermal district heating could be key to decarbonize heat supplies and meet the enacted greenhouse gas reduction targets.