More explanation of function please?

I tested the dripwall delta this spring and it was a qualified success. I had the earliest peas in victoria. There were a couple of severe frosts but also the dripwall stored enough energy in the soil and water to keep the young plants alive. I was able to measure energy transfer and it collected up to about 150 watts of heat when the sun was shining on the "wall". The wall was various things, slate tile, metal, and ceramic coated metal shelf for the oven. Also charred wood was tried. Heat gain was several degrees as the water dripped down the wall and the heat slowly transmitted along under the soil and warmed the plants gradually from the bottom. A problem was that my seedbed was too monolithic and another was that I have a spider mite infection that ruined the experiment from about April on. But for sure, it works. Energy input was about a watt. Brian October 18 2014