I ran a space heater through the current transformer primary today to get a strong secondary voltage, and I varied the resistance across the secondary to develop a VI curve so I could find the maximum power point. I solved for current and obtained the following graph:
Plotted in terms of power as a percentage of the open circuit voltage, I get this graph:
It shows me that the power harvesting hits a maximum at about 66% of the open circuit voltage. Previously, I had the harvesting circuit set to a voltage of 80% of the open circuit voltage. I should be able to obtain 0.035 W at 66% of Voc as opposed to the 0.024 W I obtained at 80% of the Voc. This should yield an efficiency improvement of about 46%. I was hoping for a doubling in one of my previous logs, but I will settle for a 46% improvement if I can actually achieve that at the output of the energy harvesting circuit.