One of the biggest challenges in eliminating emissions from our campus is replacing gas combustion in our furnaces and heating our buildings with renewable electricity. This challenge has two main parts: 1) how do we produce heat without burning anything? and 2) how do we use emissions-free energy instead?

The first answer is "move heat - don't make heat".  Heat energy is available everywhere - the air, water, the ground.  The problem is taking that heat from one place (where it's not useful) and moving it somewhere it is useful. This is what a refrigerator does. It takes heat from inside the fridge (where you don't want it) and dumps it out into the kitchen.  An air conditioner does this as well. It moves heat from indoors, where we don't want it on a hot day, and dumps it outside. In general heat pumps are much more efficient than combustion - it's more efficient to move heat than to make it - so Brown is switching to heat pumps to heat our campus. Like refrigerators and air conditioners, these heat pumps will run off electricity.

Which brings us to the second challenge, how do we use emissions-free electricity to run those heat pumps?  Brown is committed to purchasing 100% renewable generated electricity, and we anticipate that heating the campus with heat pumps will roughly double our electricity use (while cutting emissions since we will no longer be burning gas).

But where will we get our heat? One answer, for smaller, isolated buildings, will be air-source heat pumps. As the name implies, these are heat pumps that extract heat from the air, like an air conditioner that runs in reverse. On a hot day, they take heat from indoors, and move it outside. On a cold day, they take heat from the cold air outside, and move it indoors.  This works remarkably well.

However, for our larger buildings, especially those that are connected to our central heating facility and our hot water distribution loop, there is a more efficient answer. We could take waste heat from the summer (all that heat our air conditioners and chillers are dumping outside to cool things indoors) and store that energy below ground by heating up the rocks deep beneath our feet. Then, in the winter, we could extract the heat from the warm rock, and use it to heat our campus. This geothermal approach uses the rock as a thermal battery that can store energy across seasons. It is far more efficient than air source heat pumps, because it's easier to pull heat from a hot rock than from cold air. 

Figuring out how to do this, where to drill, and how much it will cost is part of our ongoing decarbonization planning and implementation. The test wells behind these fences will allow us to understand the thermal properties of the rock, estimate how many wells we will need to drill, and to what depth. This will allow us to determine costs and logistical constraints to using the Earth as a thermal battery as we transition to an emissions-free campus run entirely off renewably-generated, emissions-free electricity.