29 Finally, MIT will need to drill one or multiple test bores to assess the subsurface geology and temperature gradient. This will help determine whether geoexchange is cost-effective and how deep/how many bores will be needed to meet campus HVAC demands. Risk and Innovation The primary risk of deploying a geoexchange district energy system is operational disruption to MIT’s campus. Long before beginning building retrofits, MIT should proactively communicate with students, faculty, and staff about the reasons for undertaking this initiative. If deployed successfully, MIT would be viewed as a leader in low-carbon district energy system deployment. Because of the age of existing infrastructure and spatial constraints, there is a sense that “if we can make it work here, we can do it anywhere.” Example Deployments In this section, we provide a brief overview of planned and operational district energy systems in similar contexts and geographies. Princeton University Much like MIT, Princeton currently has a steam-based district heating system powered by a natural gas-fired cogeneration facility. Over the next 30 years, the campus is transitioning to a hot water-based system that leverages seasonal geoexchange as part of its plan to achieve climate neutrality by 2046. 6 geoexchange facilities will be constructed, each housing heat pump equipment to extract and reject heat to underground borefields (consisting of 900 bores). Existing buildings will be converted from steam to hot water. Campus cooling will be provided using chilled water produced by the same geoexchange facilities. The existing cogeneration facility will be upgraded to provide supplemental heating and cooling and backup electricity. Stanford University Stanford’s district energy system uses a combination of heat recovery and thermal storage to meet campus heating and cooling needs. Because of Palo Alto’s mild climate and diversity of campus loads, 88% of heating load is met by recovered waste heat. Hot water (at 160 – 170ºF) and chilled water (at 42ºF) are distributed from a central energy facility that houses industrialscale heat recovery chillers. The campus also uses model-predictive software to optimize system performance by shifting the timing of building energy consumption. Framingham Geoexchange Pilot The electric and natural gas utility Eversource is constructing a geoxchange pilot project in Framingham, MA (20 miles west of Cambridge). The system will provide heating and cooling to 37 buildings using 88 borefields using an ambient temperature loop. Each building will have a ground source heat pump. Though significantly smaller in scale compared to MIT’s campus, this project is illustrative of how ambient loop technology can be used in a cold climate.
RkJQdWJsaXNoZXIy MjA2MzQ5MA==