I've been looking at a commercial composting toilet for a mobile, off-grid application ("boondocking rv"). I've done a power budget and the toilet is coming out as the biggest user of energy. Power is provided via solar PV panels, and the system needs to work in the winter when there's 3x less sun than summer (at 48 deg N, Montana, USA). Are there any tips or tricks to make the energy consumption smaller, or the supporting electrical system less expensive?
- 120W heater element, thermostatically controlled, nominally 50% duty cycle
- 12VDC, 4W fan, continuous
Assuming that the heater's energy is 100% devoted to evaporating liquid, this amounts to 1.5 kWh evaporating about 2.4 L daily. Would insulating help, or are the primary losses due to evaporative cooling (and hence, fixed)? What are the consequences of unplugging the heater at night (and reducing battery size)?
Edit: To clarify, I'm looking for the kinds of tips and tricks which wouldn't violate the warranty on a commercial product or suggestions about alternative commercial products which have different operating principles.