This project will install a networked district hot water piping system to add capacity, meet our carbon goal and replace our aging, existing steam network. Princeton had a decision to make - replace old steam pipes in kind, or invest in new hot water pipes. This was a tipping point, and we decided now is the time to make the switch. All factors together justified the decision to change direction, from fossil fuels and steam to geo-exchange and hot water, powered by renewable energy, and embrace this once-in-a-generation opportunity.
- Add Capacity - The new campus plan involved one of the most extensive building programs in our history — adding some 3 million square feet in new construction to house more students, expand research facilities, and replace aging buildings and infrastructure.
- Carbon Goal - Princeton embraced both as a once-in-a-generation opportunity to not only achieve our campus plan, but also to lay the foundation needed to achieve net-zero greenhouse gas emissions before mid-century.
- Aging steam network - Princeton’s steam system began operation in the 1860s and we estimate that at least 30% of the heat made in the cogeneration plant is being lost in the ground due to aging pipes and inefficient technology.
Installation Locations
The project will affect locations campus-wide to connect main campus buildings to the new TIGER thermal energy facilities. This project will require 13 miles of trenching and hot-water piping to connect to each building’s heating system. Hot water thermal distribution and steam thermal distribution use different pipes, and so new hot water piping needs to be installed campus-wide. Unlike a new building construction site with permanent fencing, this project will move and impact different areas of main campus at different times. Converting from steam to hot water will result in campus-wide energy efficiencies, as well as campus-wide disruptions as sections of main campus get dug up to install new piping to bring geo-exchange heating and cooling to over 180 buildings. The Meadows Neighborhood was built from the beginning with hot-water and geo-exchange infrastructure.
A Glimpse of How it Works at Meadows Neighborhood
The illustration and descriptions below offer a glimpse of how thermal distribution will work in our new Meadows Neighborhood, off Washington Road in West Windsor. This brand new neighborhood provided a rare occurrence on our historic campus, a blank slate with an opportunity to build contemporary, highly-efficient systems from the beginning.
- Campus buildings: During summer months, heat is removed from campus buildings, including Meadows Graduate Housing designed to passive house standards. The heat is transferred into the water stream that returns to CUB (Princeton’s Central Utility Building), where it is then directed into the geo-exchange bores and stored in the rock beneath the surface. In winter, the heat is pulled out of the ground and returned to CUB and campus buildings via the same system.
- Low-temperature heating and chilled water distribution lines: Distribution pipes carry chilled water for cooling spaces and heated water for heat and hot water from CUB to campus buildings. The buildings also send heat from campus buildings to CUB, where it is directed into the geo-exchange piping and stored in the geo-exchange bore field in the summer.
- CUB/heat recovery chiller facility: The main facility controlling the energy needs for the Lake Campus, CUB is being built to achieve LEED certification from the U.S. Green Building Council, with a system of passive ventilation and cooling for the equipment it will contain. It will house heat recovery chillers, machines that capture heat generated during the process of chilling water.
- Geo-exchange piping: Geo-exchange piping will send heated water from CUB (either harvested from campus buildings that are being cooled or captured by the heat recovery chillers) to be stored in the geo-exchange field. At times when heat is needed for campus, it will transport the energy back from the geo-exchange field to CUB.
- Geo-exchange field: Geo-exchange bores, holes dug 600 feet deep on the new campus (and 850 feet on Princeton’s existing campus), will contain piping that recirculates water in the ground, transferring heat energy to the rock beneath the surface via conduction. The rock stores the heat until it is needed in the winter.
- Heating and chilled water thermal energy storage tanks: Thermal energy storage tanks will store heated and chilled water that are produced at optimal times for the lowest cost and greatest energy efficiency. That water can then be drawn down and supplied to the campus during periods of high demand. These tanks will typically be cycled on a daily basis.
- Backup hybrid coolers: In the summer, when the geo-exchange field is warm and unable to absorb additional waste heat from the cooling process efficiently, the backup hybrid coolers will reject waste heat into the atmosphere. The coolers can operate in dry or wet/hybrid mode. In dry mode, cool air is blown across the warm water coils, like a typical car radiator. When more heat needs to be rejected, the coolers can operate in wet/hybrid mode, where water is sprayed and evaporated to pre-cool the air, prior to blowing over the coils. The pre-cooled air will absorb more waste heat from the coil before being rejecting into the atmosphere.
- Electrical yard: The main electrical feed for Meadows Neighborhood enters at the CUB electrical yard, where it is distributed to buildings and facilities, which will eventually run primarily on renewable energy including Princeton’s own solar panels. A generator will be installed there, keeping CUB up and running in the event of a power outage.
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The time is now
Going deep: Princeton lays the foundation for a 'net-zero' campus
Path to Net-Zero
Check out the other projects that will enable us to begin converting from steam to hot water, conserve energy, increase our efficiencies, and decrease our carbon footprint and reliance on fossil fuels: