On 21 April 2014 03:32, Denny Esterline wrote: > Perhaps I missed a good reason to not do this, but I'd have thought the > more obvious storage/efficiency option would be his refrigerator. > Might have to redesign the refrigerator controls to make it happen, but i= f > you used it as a thermal sink... Run the temperature down colder to much > colder when power is available (mid afternoon) and allow it to come back = to > "normal" during the night. > "Best of all" [tm] if you do not have it fully covered already, is hot water heating. If you have a heating element that gives 100% rated power at anything below normal minimum PV voltage then you can hard PWM it from the PV and get 100% energy utilisation less MOSFET dissipation. The system must be able to provide the peak current taken when PWM is on and this must not come from the battery. Depending on wattages involved you may need a bus capacitor to hold the voltage ~=3D constant both during the PWM on time AND during the P= V recharge time. If you allow the voltage to swing during on or off times you get I^2R losses. Note that the above water-heater system is NOT the usual attempt to use PWM as a voltage level converter without a 'flying' reactive element (ie without either an energy storage inductor or switched capacitor divider). Such systems always lose energy proportional to the difference in voltage between input and output (at least). People sometimes attempt to charge a cap to some V_low from some V_higher using switch only (eg MOSFET) and think they can get near 100% efficiency for eg 12V to 5V conversion. There is no formal resistor present but Murphy ensures that the wiring resistance and switch Rdson rise to the challenge of dissipating the difference. The water heater method above achieves potentially very high efficiency by always operating the load AT Vbus but only for part of the time. R --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .