 Hi, this is Rob from Arcosanti, an urban laboratory in the desert of Arizona. At Arcosanti we work on various innovative projects to improve living conditions in urban environments. Today I'm in the Arcosanti camp and I'm going to show you how to build a geothermal air conditioning unit. It can be built mostly off things that you find around your house or can source from friends for basically no cost and it requires such little power to use that a very small solar panel will be all you need. So this is the super cube here. It's a 12 foot by 12 foot by 12 foot space obviously. So the place we're going to be installing this geothermal cooler is in the super cube here in camp. It's a 12 foot cube space. It should be about the right size to be cooled with an apparatus that's the size that we're installing. The concept of geothermal is very simple. You can see here we've dug a hole that's about 1.5 meters deep. The temperature of the ground here stays about 55 degrees. That will keep water in a big tub that we have down there at that temperature. And then the way it works is air is pulled out of the top of the cube down through a pipe into a homemade pump that we'll show you momentarily down there into the ground. The groundwater cools the air, it bubbles up and then is run through a second pipe into the bottom of the super cube. So I'll show you some of the components now for how this works. First we have a five gallon drum. This is the same type that you can get from any sort of grocery store for water. This is the perfect size hole up top for I believe one and a quarter inch pipe, your standard PVC size. Also we've drilled a secondary hole for the intake. This is the main pump mechanism of the geothermal air conditioning unit. It's all by things that we found around site here. Really simple how it works. Next we created a framework out of plywood and metal to hold the top. This is two painters buckets that were cut off. The hollow part inside is sealed through a bike tire which is connected to the buckets through zip ties. It creates a really nice seal. On the bottom there's a T for PVC which is put in and this is where the intake and the outtake of the pump go through. Up top we have an old windshield wiper motor from a car. You can use any radial motor. It doesn't need to be very strong. We found that there was lots of these lying around that we could just source from the junk pile. And then to convert that radial motor into something that pulls the bellows up and down here we just added a vertical driveshaft. Connected to this also is soldered a little nine volt power adapter so that it can be plugged into the wall. Now the only other real part to how this works is the valves themselves. The valves are important because they keep the air all going in the same direction. If the valves weren't here when this pushes up and down it would just pull and push air out both sides of it. The valves we made out of these little pieces of PVC and this is beneficial because since they're going to sit about right here and right here on either side we're going to be able to have access to them and then change them out in the event that they fail and stop working. I'll show you how these work. We did two design versions here. In the event that you have PVC that fits inside a larger diameter PVC the second design will be better because it's more simple. In the event you're just going to put the valve straight into pipe itself how that works is you can cut out a ring of plywood like that and then that ring is encased through a bike tire which creates a firm seal against the PVC. Then there is two millimeter rubber which is cut out in a circle and then duct tape to the top and that creates a very low tech type of seal. Now what we learned in this process is that we had PVC pipe that would fit inside the diameter pipe that would go inside our T so to make things more simple all we had to do was cut a circle put duct tape on it and then that will fit inside and work as a valve just through gravity so that's pretty much how it works let's assemble it now we'll put the dirt on it and get it going. So this right here is the step of the putting the geothermal system together you can see it's just filled with water we've put duct tape around the PVC up here to create a tight fit and then also when we're filling this up we're going to put gravel around here because gravel since it's larger has less chance of actually getting through any of the gaps that exist between the PVC and the water tank so let's do it. So the intake for the hot air is currently in the jug down here you can see when we had it come up we opted to run it underground a little bit just for better aesthetics now this is the piece that is going to return the cooler air in it's going to fit right into the top of the water jug like that really tight on purpose looking away so now we have both of the pipes into the water jug down here the hot air pipe which is this one comes in and then that goes fully down into the water because we want those bubbles to then come up and be cooled by the water this one which is going to take the cooler out just sits enough in the top center that way the little air pocket there where the water bubbles go to all collect and then it would naturally gets pushed out sizing can be a little tricky but once it's all down you can take it and you can duct tape the seals a little bit more which is what we're going to do right now very very easy and quick to do.