Solar Power

GWguy

GWguy

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Set it all up today, didn't expect much with the lack of sun. Even in this overcast, it's still producing 38VDC open circuit. Connected, I'm getting 14-20VDC and about .5-.8A. It's not enough to cover the usage of the fridge while running but since the fridge only runs 7-8% of the time, the other 92-93% of the time it's trickle charging and makes up for what was used over the long run.

Found a small wheeled toolbox at BJs for cheap. Going to mount the battery, inverter, solar charger and wiring in it for a nice clean portable system. Ordered some surface-mount cutoff switches for the battery and inverter. Tractor Supply has a nice full sine wave inverter for a lot less than others I've seen. Might do that.

Have to admit, this has been a fun project, regardless of whether it worked or not.
 
GWguy

GWguy

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The panel was providing power before the sun even got to it this morning, about the same as yesterday in the overcast. But once the sun hit it, the battery was fully recharged and then some in about an hour, after running the freezer all night.
This is so easy and so productive....

I had the shipping packing for the freezer, so had the bright idea to use it to provide a thermal cover. Re-used everything, got a sheet of 1/2" styrofoam and made an enclosure. The original box slips right down over the whole thing. Made the lid removable so I can still get in, and cut open the vent holes for the compressor air flow. Running a new KWH usage test to see if it was of any benefit at all.

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GWguy

GWguy

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I let the system run for a while, but was very puzzled by the results. Run time went up significantly. It has previously been running at 5-8%, now it was running 10-15%. wtf. After scratching my head for a while, I realized I had used metal foil tape to attach the thermo probe inside the freezer. I removed the tape and let the probe hang like I had before. Reset the timers and let it run overnight. Much better. Down to 4.5% run time. So the added insulation did have a beneficial effect. Every little bit helps when it gets hot outside.

Waiting on parts, some power switches and a new inverter.
 
GWguy

GWguy

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I've been letting this system run on it's own since the 2nd. Even as cloudy and overcast and rainy as it was yesterday, the panel still provided enough power to recharge the battery for overnight. Battery got low a few times, but never got to the 'abort' point. Once the sun rises, it starts charging again. When the full sun hits it, it produces 150 watts at 32-38VDC with a full load.

Had the freezer thermostat range set for 30.5 to 36 degrees. Realized that wasn't realistic, and reset it to 30.5 to 34 degrees. That 2 degree change bumped the duty cycle usage from 8 to 12%. I was expecting it to run more often, but for shorter times. Each run cycle is just as long as before and more often. Must have something to do with the how the space gets cooled. It was also much warmer today, so I need to account for that. But it has enough power to cover the increase in cycle times.

Still waiting on the new inverter. ETA Wen. Have to wait until I have it before mounting everything up in the portable tote, to make sure the clearances between components is good.
 
PeoplesElbow

PeoplesElbow

Well-Known Member
GWguy said:
The panel was providing power before the sun even got to it this morning, about the same as yesterday in the overcast. But once the sun hit it, the battery was fully recharged and then some in about an hour, after running the freezer all night.
This is so easy and so productive....

I had the shipping packing for the freezer, so had the bright idea to use it to provide a thermal cover. Re-used everything, got a sheet of 1/2" styrofoam and made an enclosure. The original box slips right down over the whole thing. Made the lid removable so I can still get in, and cut open the vent holes for the compressor air flow. Running a new KWH usage test to see if it was of any benefit at all.

View attachment 136109 View attachment 136110 View attachment 136111 View attachment 136112
Click to expand...
nice experiment

One thing that might help is getting the heat generated by the compressor and coils away from the unit more efficiently. I would say insulate better between the compressor/coils and the unit but there probably isn't room for that.
 
GWguy

GWguy

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PeoplesElbow said:
nice experiment

One thing that might help is getting the heat generated by the compressor and coils away from the unit more efficiently. I would say insulate better between the compressor/coils and the unit but there probably isn't room for that.
Click to expand...
I can look into that. Might be able to slip a piece of styrofoam in there. I saw a video where someone squirted GreatStuff all around the compressor and slid styrofoam between the coils and body. I'll have to see if I can find that vid and if his mods made a difference. I think he did it "just because" and didn't really run any performance testing.
 
PeoplesElbow

PeoplesElbow

Well-Known Member
GWguy said:
I can look into that. Might be able to slip a piece of styrofoam in there. I saw a video where someone squirted GreatStuff all around the compressor and slid styrofoam between the coils and body. I'll have to see if I can find that vid and if his mods made a difference. I think he did it "just because" and didn't really run any performance testing.
Click to expand...
I would be afraid the greatstuff would make it overheat, it has to shed heat.
 
GWguy

GWguy

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Got the new inverter today. The old one worked, but this one is much better, better performance, better power safeguards for over and under-voltage protection, draws less current at idle than the old one did, and has a "soft start" so as not to damage induction motors and such, like a fridge.

Outputs at 120VAC as opposed to 115VAC. I'm thinking this might shorten the fridge on-cycle times. New one holds 60 Hz, the old one was a few cycles under, and if there was no load, it drifted all over the place, as high as 138 Hz. Old one had a fan that kicked on as soon as there was power draw. It was kind of loud and I knew when the fridge was running. New one has a fan, but it won't kick in until the internal temp reaches 65 degrees C. With as little load as I'm pulling, it may never turn on. The whole system is whisper quiet now.

So reset the stats monitoring and will let it run for a few days. It's been running totally standalone since the 2nd of April, fridge temps hovering around 30 degrees with nothing in it.
 
GWguy

GWguy

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GURPS said:
would something like that run a Window AC Unit in the summer / during the day?
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@GURPS
Regarding supplementing your A/C, this s probably what you need to do. It's a small solar transfer switch. When the solar batteries are depleted, it kicks over automagically to grid power.
 
GURPS

GURPS

INGSOC
PREMO Member
there are also these 'inverters' you just plug into the wall to offset electric coming from the meter
 
GWguy

GWguy

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Been running now for about a week and a half non-stop. I'm really pleased. With the new inverter and resetting the temp range, it has a duty cycle of about 10% +/- 1%.

Going to dismantle it today and permanently mount it all up in a nice portable package.
 
GWguy

GWguy

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Pretty much done. Waiting on an external display for the solar charger, that will get mounted on top. Also need to mount a remote on/off switch for the inverter. Otherwise, not a bad little package.

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Chris0nllyn

Chris0nllyn

Well-Known Member
Looks awesome!

Are you worried about heat build up in the inverter box? Would it be worth adding a small 12V computer fan?
 
GWguy

GWguy

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Chris0nllyn said:
Looks awesome!

Are you worried about heat build up in the inverter box? Would it be worth adding a small 12V computer fan?
Click to expand...
Thanx.
Not really. I ran it for days on the bench and it barely got warm. It got a few degrees warmer in the box, but not enough right now to worry about.
 
GWguy

GWguy

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Just an FYI for anyone using a 12VDC to 120VAC inverter. They all have a 3 prong outlet (hot, neutral, ground) but the ground is not connected to a real ground. If you use one in damp conditions where you'd normally use a GFI circuit breaker for protection, a GFI cannot work and there is no GFI protection.

I came across this out of curiosity, used a GFI tester on the 120VAC output, knowing it was going to be used outside in potentially damp/wet conditions. GFI tester showed no ground circuit. Tried 2 other inverters, same thing. There is no "earth" grounding. The inverter frame is "grounded", but only to the negative pole of the battery.
 
GWguy

GWguy

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I have a spare full size fridge, top freezer, just sitting there. I got curious if the solar system could power it, so I hooked up the watt meter. Again, surprised. Initial turn-on surge was about 1500 watts, but quickly fell to 120 watts. In partial sun, the solar system can easily cover 120 watts. After it ran for a few hours, it fell to 95 watts. Barely more than the freezer/fridge I put together. But being bigger, it will run much much longer. During the day, not a problem, but it would need a much bigger battery than the 45Ah I have now to carry it thru the night.

So, in a pinch, the little, portable solar system could run a full size fridge. Interesting.
 
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