My project partner P has done a brilliant job with the evapotron’s physical part. It starts with a platform:

The kiddie pool and the mesh tower sit on the platform, and the reservoir and pump are underneath.

In this shot, you can see the green filter bucket in the lower right (on top of the white bucket); the tower on the platform in the center; and the green reservoir bucket underneath the platform. The idea is that the water is pumped from the reservoir up a pipe running through the center of the tower and over the saucer on top. The water trickles down the tower, wetting the burlap. Here’s a shot of the drive pipe, the pump attaches at the bottom.

The tower is made of a heavy interior mesh (approx 16ga wire in 6″ squares — it’s fencing). Then the burlap is wrapped around, then a thin screening mesh is on top of the burlap. The whole thing is held together with zip-ties.

We found that it was important to draw channels on the saucer (in silicone) to get the water flowing evenly across the saucer. Otherwise (and perhaps even so), we’ll be shimming under the platform endlessly, trying to get it level.

(There is another option — to use a rotating sprinkler head inside the tower — which avoids the need to level. However, this leaves the saucer dry, and I suspect that the saucer is a big contribution to the evaporation. This may be testable.)

P packed it and hauled it to our campmates’ staging area near Reno. Now if only I can finish the control units, we’ll have data and control of the charging. Time is short.