Just before I graduated from college I applied for a position with Teach for America. I had to present a mock lesson as part of my interview. After some thinking, I spent hours preparing exaggerated, colorful pictures of bird legs (think Big Bird) and used the countercurrent multiplier theory from my animal physiology class to explain how birds kept their skinny little legs warm. I was hoping for a high school science position. I did get hired, but to teach kindergarten in rural Louisiana. For many reasons I decided not to take the job. I did save those bird pictures, though, and a part of me will always wonder what life could have been had I taught kindergarten deep in the impoverished south.
I haven’t thought about countercurrent multipliers in a long time. I am not sure that I could explain the concept anymore, at least without my bird drawings. But there has always been a very small piece of me that is a secret science nerd. I’ll credit that to my dad who was a scientist in the purest sense of the word, and even to my brother who inspired my lackluster attempt at the Science Olympiad in middle school. The competition was in Liverpool, NY. I didn’t do very well at all and I never went back to the science club.
As it turns out, building our house has been a science project of sorts. Exploring ways to reduce our energy consumption must rely on the latest science and technology. And, this week, the most spectacular of all of our science experiments happened, almost without us knowing.
On Wednesday when we stopped by the site there were huge machines digging a gigantic trench in the back yard: the trench for our geothermal heating and cooling system. By the time we returned on Saturday the pipes were laid and the trench was filled in- and I didn’t even get to photograph it (and neither did anyone else since it was a rainy day). Drat! So we’ll probably never see those pipes, but the science nerd in me still wants to know how they work. And, wouldn’t you know it, bird leg physiology isn’t so far removed from our geothermal system.
Our contractor, Geosun, explained it like this:
1. Let’s say the water [in the outdoor pipes] enters the home at 50 degrees.
2. That water enters the heat pump (looks much like a traditional furnace) where it goes through the first ‘heat exchanger’ giving its heat to the refrigerant gas.
3. That gas goes to a compressor, and when put under pressure the gas temperature increases.
4. The gas then goes to the second heat exchanger where it gives its heat to circulating air for a hot air system or water for a baseboard or radiant system.
5. The gas then goes to an expansion valve which allows the gas to cool off, and then back to step 1.
Here’s my attempt to explain it in even simpler terms. The pipes that were just placed in the giant trench will contain water or another fluid that circulates through them. The fluid equilibrates to the temperature of the earth at that depth- in our area that is about 50 degrees no matter the weather No, we’re not such green-enthusiasts that we’ll be keeping our house at 50 degrees all year round (frankly, our house will never be kept at 50 degrees- that’s crazy!). Instead the system will rely on the transfer of heat: in the winter between the relatively warm ground and the cold air, and in the summer between the relatively cool ground and hot air. Compressors and pumps help convert the energy from the heat transfer into a toasty air for our house in the winter, and nice brisk air for the summer. All of this happens with a little bit of electricity for the pump- but no fossil fuels. Kumbayah?!
As I sit here in our apartment, my thoughts muffled by the literal roar of our forced-air gas heating system, it is still hard to wrap my head around geothermal. Maybe I need to do what I did to teach about bird legs, what I did to understand kidneys and cells and hearts in med school: turn the science into drawings and have a little fun with it along the way.