The above graph was obtained by placing line probes behind the middle Energie Solaire panel, one at the top and one at the bottom. The strange behavior of the panel is due to the bad weather conditions on these days. There was never more than intermittent sun, so rather than picking up heat during the day, the system is losing heat. A possible problem with these measurements is that the probes were not well insulated and were only sandwiched between the stucco wall and the panel.