High Voltage vs Low Voltage Direct Drive Solar Cooking

I am very pleased to find this forum. I am working with Living Energy Farm in Virginia. We have developed what we call a DC Microgrid that, among other things, uses electricity straight from PV panels to cook. We are in a much cooler, cloudier climate than either southern California or most of Africa. We are using a combination of biogas (and hopefully using biogas to fuel small agricultural machinery) and direct drive solar. We have been using direct drive DC power  for 10 years. It's great! We use high voltage systems, 180 volt in particular. We use our PV system to cook and run myriad machines at the same time, not the least of which are heat collection blowers that provide most of our space heating needs (by pulling air from solar hot air collectors and blowing it under the dwellings). Our systems are community scale, and do multiple duties running a lot of different machines. The limitation of our high voltage systems is that they have a much higher setup cost. The low voltage systems under discussion are cheaper to set up, though lower capacity. We have found that we can overload our system 300% in the summer, and cook at the same time. We cook for 10 - 15 people in the summer. We use hayboxes (insulated cookers), but we insulate cooking pots after they are heated on a solar powered hot plate. One could put heating higher voltage heating coils in an insulated box, though one would have to be careful about overheating, melting the heating coils or starting a fire. We are expanding our work, with projects on the Navajo and Hopi Nations in Arizona, and a project in Jamaica. The latter project involves using direct drive DC in commercial food processing operations. I am very pleased to see what you folks are doing and hoping we can support each other. We will be experimenting with your designs.
Alexis Zeigler, Living Energy Farm (.org)

Alexis,

Thanks for the introduction to your community. Yes, DDS (Direct Drive Solar) is the cheapest source of electricity, and was the general focus of my research, although now we focus exclusively on ISEC. 180 V would work fine if you use a 220 V electric burner for the heater... which would provide probably around 800 W.

Also, the hay box or "magic basket", or "retained heat cooker", is how I used to cook a lot of my food, as I explain in this story about my home. Then, it occurred to me that I could put a heater into the hay box and it would not only keep it hot, but heat and cook it. AND, as you point out, then you have to be careful not to start a fire. We get around this by employing thermal switches to turn off the voltage if it gets too hot, and thermal fuses... in case the thermal switch doesn't work. You can read more about the construction in the construction manuals on our ISEC research page. But in short, your ambition to employ ISEC with thermal storage on the community scale is perfect (in my opinion). You'd be able to cook after dark. The thermal storage would work better with larger amounts of phase change material. It's a great idea. I look forward to our future communications.

Very rich article from Alexis Zeigler.Thanks !