PV Cooking For {NOT} Dummies. Keep Panel At Power Point With Boost Converter And 100W 12V Panel
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- Опубліковано 8 лют 2025
- Found a pot which was 600W at 120V which has a resistance of 21 ohms. This small pot is a steamer, the reason for the high wattage. Most are way more than double this resistance and less than half the wattage. This makes it possible to use a boost converter with a 12V panel.
I had a 300W boost converter which was pretty typical with an idle current of 20ma, 100V capacitors and was set up with a maximum voltage of 33V. I increased that to 40.5V maximum, the most I thought the semiconductors could take. The solar panel is a RENOGY 100W with 22,5V open circuit. Max I observed was 20.5V, these panels are old and went thru a lightning event. Vmp is 18.9V and Imp 5.29A.
Power point control is a voltage divider, 40K into a 10K pot. FET gate voltage is used as a reference. Drain feeds current into switcher reference pin (2.54V) thru diode to fake converter into thinking voltage is too high and shutting down.
TEST RESULTS
18C start at 10am 16.2V power point 52W19oz of water panel facing east
33C 11 minutes 10WH 57W 16.6V in 32V out
55C 30 minutes 27.6WH
66C 45 minutes 40.7WH hot enough to kill bacteria
76C 60 minutes 54.8WH 62W keep warm thermal trips (not used)
86C 120 minutes 113WH
87C 154 minutes 146WH this is the terminal temperature where input = loss
This does work. If buck converter totally shuts off it does a pass thru to heating element. 10K resistor not low enough to shut down converter so boost converter went into a death spiral down to 9.6V. They shut down at that voltage to protect the FET. Power point for panel was 16.7V and converter had about 15% loss and ran quite hot. This is still more effective than direct connect methods others have used and this uses a standard pot. Most of the choices with 100W panels are not very good.
Found a pot which was 600W at 120V which has a resistance of 21 ohms. This small pot is a steamer, the reason for the high wattage. Most are way more than double this resistance and less than half the wattage. This makes it possible to use a boost converter with a 12V panel.
I had a 300W boost converter which was pretty typical with an idle current of 20ma, 100V capacitors and was set up with a maximum voltage of 33V. I increased that to 40.5V maximum, the most I thought the semiconductors could take. The solar panel is a RENOGY 100W with 22,5V open circuit. Max I observed was 20.5V, these panels are old and went thru a lightning event. Vmp is 18.9V and Imp 5.29A.
Power point control is a voltage divider, 40K into a 10K pot. FET gate voltage is used as a reference. Drain feeds current into switcher reference pin (2.54V) thru diode to fake converter into thinking voltage is too high and shutting down.
TEST RESULTS
18C start at 10am 16.2V power point 52W19oz of water panel facing east
33C 11 minutes 10WH 57W 16.6V in 32V out
55C 30 minutes 27.6WH
66C 45 minutes 40.7WH hot enough to kill bacteria
76C 60 minutes 54.8WH 62W keep warm thermal trips (not used)
86C 120 minutes 113WH
87C 154 minutes 146WH this is the terminal temperature where input = loss
This does work. If buck converter totally shuts off it does a pass thru to heating element. 10K resistor not low enough to shut down converter so boost converter went into a death spiral down to 9.6V. They shut down at that voltage to protect the FET. Power point for panel was 16.7V and converter had about 15% loss and ran quite hot. This is still more effective than direct connect methods others have used and this uses a standard pot. Most of the choices with 100W panels are not very good.
and i have one of those boost converters as well so what still works good as long as you put a fan on them and you can fix them easily
When you want a 30% improvement by using a boost converter on a fixed resistance and half of that is lost in conversion, is that a worthwhile design.
This pot when plugged into my 12V system (8W) makes a great dough proofing pot for donuts now that we have cooler days.
Will the boosted DC burn the thermostat contacts when it switches on and off? I guess if you had more panels you could use your reservoir capacitor - switching MPPT circuit to break the power at a few hundred Hz which would quench any thermostat arcs.
I had more to say but my wife dragged me off shopping, Arcing could be a serious issue. The boost converter would be a minimal off the shelf solution. The boost converter never really got above 35V with that panel in fairly good conditions, Most contacts can take 30V DC, 35V DC switching on tungsten contacts could be survivable. The buck would have to be limited to that voltage,
The steamer pot would be useful at home as well in a camping situation. I wanted to use an off the shelf pot. There are 50W 12V pots that some videos have connected to 100W panels. These are overpowered at times and could be damaged. Direct connect also showed them working at half power because of mismatch. That solution would require a single panel. I see RENOGY has 120W panels and that extra power is really needed.
This video was to see how much power was really needed to cook a meal and I was surprised it was less than 100W. These pots do reach a temperature limit where loss = input power. They are poorly insulated. Primarily it was to show the basic method to control input voltage, another video will follow. I had done a water heater where panels drove a boost converter to high voltage and then that was pulsed according to panel voltage. That was disappointing because high boost converter loss ate up half the gain of going to power point control. Moving soon, if I get
the time will do an efficient AC transformer based design.