Princeton University geothermal heating system replacing steam has drilled over 2,000 of a planned 2,900 wells since 2021

Princeton University geothermal heating system replacing steam moves campus wide

Princeton University geothermal heating system replacing steam is drilling geo exchange wells, boreholes sent hundreds of feet into the ground that move heat between the earth and campus buildings through hot water pipes instead of the natural gas fired steam Princeton has burned for decades. The university has drilled over 2,000 of those wells since 2021, working toward a long range plan of 2,900. The wells feed 2 new plants called TIGER and CUB, which will work alongside a renamed West Plant to heat and cool 180 campus buildings once finished. Princeton says the conversion supports its goal of reaching climate neutrality, when the university adds no net carbon dioxide to the atmosphere from its own operations, by 2046.

What Princeton own geo exchange plants add beyond heating

ZGF Architects, the firm that designed TIGER and CUB, states on its own project page that it built the plants to be seen rather than hidden, so each one works as a teaching tool for anyone walking past. The same page states the 2 parking garages built alongside the project add 104 electric vehicle charging stations, a detail that shows the project reaches beyond heating alone. Princeton own facilities flyer states its geo exchange wells run about 850 feet deep, and that TIGER holds 2 thermal energy storage tanks 40 feet tall that store hot and cold water so the system can shift when it draws power.

Princeton has moved 25 of its 180 buildings off steam so far

Princeton has fully converted 25 of the 180 buildings the project eventually covers, with 5 more partially converted and still using some steam. That leaves 155 buildings still on steam, 180 minus the 25 already finished, a subtraction this article makes from those 2 counts rather than a figure either source states directly. Energy Plant Manager Ted Borer confirms the combined TIGER and CUB systems cost hundreds of millions of dollars, and says the total could still swing 30 to 40% depending on how much of that cost Princeton can claim under the Inflation Reduction Act, a federal law that offers tax credits for clean energy projects, a question still being worked out with outside counsel.

Princeton old steam plant loses 32 of every 100 units it burns

Dave Weis, Energy Plant Director, says the existing cogeneration plant, which burns fuel to make electricity and steam together, delivers the benefit of only 68 of every 100 units of energy it burns, losing the other 32. Weis says the new heat pump system moves 5 units of heat for every 1 unit of energy it uses, since a heat pump moves heat that already exists rather than burning fuel to create it.

I think that the thermal piggy bank is a great way to describe geo exchange.

Dave Weis, Princeton Energy Plant Director. Source 4.

Through the conversion to high temperature hot water supplied by heat pumps, we're essentially electrifying campus.

Sarah Boll, executive director of Princeton Office of Sustainability. Source 4.

Energy Plant Manager Ted Borer describes what that means for the new plant in his own words.

That means we're delivering to this campus 4.5 times the energy we're putting into the plant.

Ted Borer, Princeton Energy Plant Manager. Source 5.