Sometimes gravity is an architect’s friend.

In fact, architects can use gravity to human advantage in all sorts of ways.  In Ecology class today, I showed some diagrams of systems that use “thermosiphoning.”  That’s a fancy word referring to gravitation pull that moves fluids (like air or water).

The idea is that warm air (or water) rises and cold air (or water) sinks… because a  liquid is heavier and more dense when it is cold.

So, we can let gravity do the work if we think a system through.  Sometimes we need to move liquids in directions they don’t naturally want to go, and then we need to add electric pumps or fans to our systems.

Today, I showed my second year architecture students a tromp wall system as well as a diagram of an open loop solar hot water system.  In that type of system, you let the sun heat the same water that you will use to shower, wash dishes, or drink.

I also showed a few diagrams of basic heat exchangers… like the one in a car.  That one takes the heat from the combustion process and uses it to warm the air in the car without bringing in the “smog.”

A trombe wall system that uses air circulation (from http://www.your-solar-energy-home.com/Indirect-gain-solar.html)

A system that uses solar heat collection with back up electrical heat (from http://www.daviddarling.info/encyclopedia/T/AE_thermosiphon_system.html)

An open loop solar hot water system (from http://commons.wikimedia.org/wiki/File:Thermosiphon.png)

This is a basic heat exchanger (from http://me1065.wikidot.com/automotive-heat-exchangers)

The students were seeming to “get” the ideas, but they didn’t seem particularly jazzed up about them.  (I knew that because they were fidgeting and clearly wanted to text.)

To get them involved, I turned posed a problem for them to solve.

I asked them to pull out a sketchbook and combine the solar collector and the heat exchange into a single diagram.  They needed to figure out how you could use water with water with glycol (i.e., antifreeze) in it to collect the sun’s heat and then use that same liquid to warm the water for someone’s shower.

The challenge was to transfer the warmth into potable water without tainting it.  A couple of students caught on fast. After everyone had given it a try, I let them help each other.  More and more people got it.

At about the same time, I asked a four of the students who caught on quickly to draw their diagrams on the board and then explain how they worked to the class.  We all put our heads together to analyze the designs.

Eric Brown, Jalin Williams, and Janine Stewart caught on quickly.

Eric Brown’s system uses a roof-mounted storage tank.

Janine Stewart replicated a system she had seen during the Hampton Roads Solar Tour, at Dr. Ben Cuker’s house.

In Janine’s system, the tank is down lower (so it can be hidden in the basement). Her diagram includes a pump for moving the glycol/water liquid around.

Jaylon Floyd created the most straight-forward diagram. We discussed how to mix in colder water to allow the girl in the bathtub to regulate the water temperature.