Solar Powered refrigerator project

[ygmir]

Victron has some products where you can add micro inverters to the inverter/charger 120v output and not endanger the inverter but it's expensive and for off grid just charging batteries seems to be more cost effective.

and again, thanks for all the great info!
I'm of course, off grid at the Hof, so will make a set up for there, and one portable...

[Token]

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It is quite possible that I am using more energy in the refrigerator scenario than if it were a deep freezer. I think the temperature band in the freezer scenario is wider so there would be less startup cycles but longer run time.
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Not likely. For a set mass going one degree down will take a constant amount of energy, as long as you don’t hit phase change - going from cold to frozen. This assuming the insulation is good enough to ignore in the calculations as insignificant loss.

Even if insulation is not perfect, the temp gradient of fridge vs freezer to ambient favors the fridge having less heat transfer loss.

The length of the cycle will be proportional to the temperature range - the hysteresis.

[some seeing eye]

This is a "cool" project (sorry)

I'm starting down a small portable solar path. One of my challenges has been a portable panel at a reasonable price, so I'm hoping for ideas.

The cheapest panels are used rooftop panels. They are large to be cheap and heavy since weight is not that important. The most efficient panels are the newest rooftop panels approaching 1 meter x 2 meters. They are about fifty pounds - what an installer person can carry.

The folding camping aluminum frame panels are under 30 pounds, and smaller, but expensive from suppliers like Re__, G__ Z__, E__ F__, and survivalist suppliers line B__ B__. I can make my own stand. 12V on up is fine. I'm aiming for 100W panels at around $100/W, not $150/W on up to ridiculous.

I don't see how portable mono flexible panels can be reliable. What keeps the wafers from breaking?

I'm not really interested in compound roll panels which can't be angled to the sun.

For batteries, I'm looking at LiFePO4 built from cells. I'm excited about sodium ion cells coming out next year. I would like to get under $200/kWh.

I'm looking at the V_n electronics ecosystem, though they are expensive.

[motskyroonmatick]

Good conversation guys!

What kind of things do you want to power some seeing eye?

[ygmir]

.

It is quite possible that I am using more energy in the refrigerator scenario than if it were a deep freezer. I think the temperature band in the freezer scenario is wider so there would be less startup cycles but longer run time.
.

Not likely. For a set mass going one degree down will take a constant amount of energy, as long as you don’t hit phase change - going from cold to frozen. This assuming the insulation is good enough to ignore in the calculations as insignificant loss.

Even if insulation is not perfect, the temp gradient of fridge vs freezer to ambient favors the fridge having less heat transfer loss.

The length of the cycle will be proportional to the temperature range - the hysteresis.

do you think, though, the increased number of starts for a fridge, would be offset by the greater heat transfer loss of the freezer? I know it's a pretty fine point on the pencil to wonder, but still, since starting a motor takes more power than running it, it might be close to an offset?
My ancient chest freezer here at my house, never shuts off as far as I can tell. very small motor, just always runs. Has been running for 20 years....or maybe I'm missing something? The temp control knob feels like a valve, so maybe just moderates the amount of coolant? I've never investigated.

[some seeing eye]

What kind of things do you want to power some seeing eye?

Great question. My Playa use case is running a Ubiquiti uplink, access point, and some kind of Internet device, and a very small amount of lights. I try to have burner things I can use year around, not single use.

I live in Oregon where we have grey winters and the occasional ice storm that knocks out power, as much as 3-5 days, but usually under a day. So I would like to be able to run my carrier fiber/cable uplink, firewall, router, laptop and phone up to 18 hours a day.

Both of those cases are under 200W. Someone else showed their 100W 12V 35Ah system running their Ubiquiti on playa.

I have been following the offerings of B_H_ for batteries. I would like to keep all my pieces under 30 pounds each. I do not want to mess with the chance of battery fires.

[Token]

do you think, though, the increased number of starts for a fridge, would be offset by the greater heat transfer loss of the freezer? I know it's a pretty fine point on the pencil to wonder, but still, since starting a motor takes more power than running it, it might be close to an offset?
My ancient chest freezer here at my house, never shuts off as far as I can tell. very small motor, just always runs. Has been running for 20 years....or maybe I'm missing something? The temp control knob feels like a valve, so maybe just moderates the amount of coolant? I've never investigated.

Fist and foremost, that antique freezer you got ... don't go hacking that into a solar setup ... Museum!

On modern chest freezers, with the coils basically being the whole outside box, and the really good insulation ...

The frequency of cycling will largely depend on the active range.

If the freezer set to 0 degrees starts the compressor for a cooling cycle at 5 degrees and shuts it off at -2, the range is 7 degrees, of which 2 is the overshoot on the hysteresis.

If you run it as a fridge, and set it to 36, turn on at 41, run until 34 degrees - the energy used is the same.

In this example the numbers all match up, 5 degree range, 2 degree hysteresis.

If the fridge mode has a narrower range than the freezer mode, you will get more cycles.

[ygmir]

ha, yeah antique freezer. no, I was not thinking of running it that way, but buying a new one if I decide to put that all together.
Well ok, I accpept your calculations, so thanks for the clarification and explanation!

[Ratty]

Hi Igmir. I'm trying to reach Julia. I lost many contacts in a tragedy. could you possibly have her call me? Thank you.
I'm trying many avenues to get there.

[Captain Goddammit]

Setting up the unit isn’t that big a deal.
The big glaring problem with this whole thing is the idea of free public fridge space.

[motskyroonmatick]

So far the test of the freezer hacked in to a refrigerator running on solar power only is going well. The system is averaging 572Wh of power consumption each day. The highest day's use was 690Wh and the lowest was 490Wh. This corresponds with hot days and cool days. On the cool days the solar panel spends a small amount of time running above 90% of its rated power of 220 wats and on the hot days it does not come close. The charge controller spends about 8 hours in Bulk charging mode on average but has seen over 10 hours in bulk charging and as little as 7. Charging the battery starts when the panels exceed battery voltage by 2 volts so there is a long time in the morning where there is very light charging happening. Battery voltage drops to 13.17v or there about during the night, fully charged is 14.40v and float voltage is 13.6v. The battery is a 1200Wh LiFePo4. The inverter is a lower end 1000wat 12v DC to 110v AC pure sine wave inverter.
I think this system would work well on Playa and I am going to operate it there.
I do think for backup in case of power outage at home I would double the battery capacity to have more power in reserve for low power production days or double the size of the solar array and charge controller to have faster recovery time/sufficient charging under low light.

It's been a fun project.

[ygmir]

Hi Igmir. I'm trying to reach Julia. I lost many contacts in a tragedy. could you possibly have her call me? Thank you.
I'm trying many avenues to get there.

HI Ratty.
I'll try to message her and let her know!

[ygmir]

So far the test of the freezer hacked in to a refrigerator running on solar power only is going well. The system is averaging 572Wh of power consumption each day. The highest day's use was 690Wh and the lowest was 490Wh. This corresponds with hot days and cool days. On the cool days the solar panel spends a small amount of time running above 90% of its rated power of 220 wats and on the hot days it does not come close. The charge controller spends about 8 hours in Bulk charging mode on average but has seen over 10 hours in bulk charging and as little as 7. Charging the battery starts when the panels exceed battery voltage by 2 volts so there is a long time in the morning where there is very light charging happening. Battery voltage drops to 13.17v or there about during the night, fully charged is 14.40v and float voltage is 13.6v. The battery is a 1200Wh LiFePo4. The inverter is a lower end 1000wat 12v DC to 110v AC pure sine wave inverter.
I think this system would work well on Playa and I am going to operate it there.
I do think for backup in case of power outage at home I would double the battery capacity to have more power in reserve for low power production days or double the size of the solar array and charge controller to have faster recovery time/sufficient charging under low light.

It's been a fun project.

great info, Motz! thank you so much. I'm sure many will benefit from your knowledge here.

[ygmir]

.

[HarryN]

So far the test of the freezer hacked in to a refrigerator running on solar power only is going well. The system is averaging 572Wh of power consumption each day. The highest day's use was 690Wh and the lowest was 490Wh. This corresponds with hot days and cool days. On the cool days the solar panel spends a small amount of time running above 90% of its rated power of 220 wats and on the hot days it does not come close. The charge controller spends about 8 hours in Bulk charging mode on average but has seen over 10 hours in bulk charging and as little as 7. Charging the battery starts when the panels exceed battery voltage by 2 volts so there is a long time in the morning where there is very light charging happening. Battery voltage drops to 13.17v or there about during the night, fully charged is 14.40v and float voltage is 13.6v. The battery is a 1200Wh LiFePo4. The inverter is a lower end 1000wat 12v DC to 110v AC pure sine wave inverter.
I think this system would work well on Playa and I am going to operate it there.
I do think for backup in case of power outage at home I would double the battery capacity to have more power in reserve for low power production days or double the size of the solar array and charge controller to have faster recovery time/sufficient charging under low light.

It's been a fun project.

That is great progress. Exactly as you are observing in the testing, the power consumption varies with temperature. If the 220 watts isn't enough at your test site, it won't be enough on the playa either.

If you wire the panels in series, then the Vmp will rise sufficiently high - earlier in the day and start charging.

The alternative, is to use a PWM controller like a bogart - as those turn on essentially as soon as light hits the panel and don't need the excess voltage of Vmp - Vbat to work.

I help people with putting solar on their vans - mostly to run refrigeration and 200 watts is pretty much never enough no matter what is going on. Plan on doubling it if you want any chance of success.

[Token]

Battery voltage drops to 13.17v or there about during the night, fully charged is 14.40v and float voltage is 13.6v. The battery is a 1200Wh LiFePo4.

LiFePo4 Cell is 3.2V nominal; 2.5V discharged, 3.6V full charge.

At 13.7V you’re 3.425V per cell, not even at nominal voltage.

Plenty juice in that battery and sounds like enough charging time to top it off every day.

Makes sense actually. The battery gets used during least demand … when ambient temps are low.

Daytime, the demand increases but the solar panel is producing concurrently.

Pretty darn slick how that all works out and big fucking hugs for the effort and data.

[motskyroonmatick]

Thanks Token! Thanks Ymir!

Here is a chart from a chart plotter running on a 7 day full rotation. The peak temperature is 44 degrees F and the low temperature is 34 degrees F. This is over a weeks worth of data and the system is working reliably. There are several artifacts on the chart from before the probe was measuring box temperature.

Swing on by CrowBar at Black Rock City Welding & Repair to see if the beer is cold.

[HarryN]

Thanks for the great data collection.

What do you think is causing the high temperature excursions (> 40 F) ?

Shortage of power or just what the fridge is capable of?

[motskyroonmatick]

Thanks for the great data collection.

What do you think is causing the high temperature excursions (> 40 F) ?

Shortage of power or just what the fridge is capable of?

It could be a malfunction of the chart recorder. But...The 3 events roughly corresponds with10am when the sun would be full on the fiberglass roof of the box where the fridge is kept and the fridge not being in the shadow of the wall of the box. It seems to happen at the same point in the warming cycle and it does not happen every day. The battery voltage hasn't dipped low enough to indicate a critical power shortage has happened. It's such a sudden rise and fall that I think its a recorder malfunction because it doesn't match the ramp of normal temp rise indicated by the graph and I was not home at those times to open the lid and cause a spike in temp on the recording probe.

[motskyroonmatick]

Only one spike outside of temp range in the recent data since I flipped over the chart 6ish days ago.

[HarryN]

Thanks for the great data collection.

What do you think is causing the high temperature excursions (> 40 F) ?

Shortage of power or just what the fridge is capable of?

It could be a malfunction of the chart recorder. But...The 3 events roughly corresponds with10am when the sun would be full on the fiberglass roof of the box where the fridge is kept and the fridge not being in the shadow of the wall of the box. It seems to happen at the same point in the warming cycle and it does not happen every day. The battery voltage hasn't dipped low enough to indicate a critical power shortage has happened. It's such a sudden rise and fall that I think its a recorder malfunction because it doesn't match the ramp of normal temp rise indicated by the graph and I was not home at those times to open the lid and cause a spike in temp on the recording probe.

That makes a lot of sense.

I have built some solar power systems and tested them in my back yard. By far the sunlight hitting them was the largest source of heat vs even running the inverter pretty hard.

I have played a little bit with adding reflective tape of various colors. The silver tape works but it is a bit gaudy and a lot of glare.

[Pythonsummer]

Hi, I build solar generators for various uses, including I have one for powering the side x side refrigerator / freezer in my garage.

I would like to work with a camp or someone to do a project like this out on the playa. Sort of a "free use of a section of abest guide for refrigerator or freezer at icedetective shelf" for people that need something like that.

My motivation is that I do some volunteer work in disaster relief and would like to test one under tough / dusty conditions, by people who don't really take very good care of things, but still have someone around who can deal with challenges as they come up.

I have been trying to do this at BM for about 4-5 years, but either I could not purchase a ticket, covid, or this past year I was in an accident and was in recovery / could not work as much like before.

I am 63, so not exactly a typical burner and I am unsure if I can really attend in 2022 for health reasons, but can work with people or a team locally (SF bay area). I live in the east bay near 580 / 680.

The technical aspects of solar / battery / inverter design / selection are not really a problem, so that part is relatively easy for me.

The details related to a solar panel setup that can actually withstand the conditions are BM are more exciting to figure out and I could use some advice in that area.

Size wise, they are roughly the size of full size suite case, so ~ 12 x 20 x 30 inches.

My initial idea was to use a heavy duty ladder and mount the solar panels on it - some facing east, some facing west.

Open to ideas / suggestions or if anyone or any teams would like to participate.

Thanks

Harry

When converting single phase AC to three phase, we employed inverters and motor speed controllers/AC drives, and their electronics are essentially the same. We had a lot of issues with motor windings arcing to the bearings in Maneurope compressors twenty or so years ago. We eventually located the AC Drives as the cause. The issue was resolved by switching manufacturers.
In addition, it is known that buildings with a lot of computer equipment can overload the neutral with third order harmonics produced by the power sources. Following a few building fires, the NEC Code was changed to exclude smaller neutrals. On electronic devices, I wouldn't apply a modified sine wave. Considering you just have that, you can probably get away with it, but not worth it if buying new inverters.

[HarryN]

Hi, I build solar generators for various uses, including I have one for powering the side x side refrigerator / freezer in my garage.

I would like to work with a camp or someone to do a project like this out on the playa. Sort of a "free use of a section of abest guide for refrigerator or freezer at icedetective shelf" for people that need something like that.

My motivation is that I do some volunteer work in disaster relief and would like to test one under tough / dusty conditions, by people who don't really take very good care of things, but still have someone around who can deal with challenges as they come up.

I have been trying to do this at BM for about 4-5 years, but either I could not purchase a ticket, covid, or this past year I was in an accident and was in recovery / could not work as much like before.

I am 63, so not exactly a typical burner and I am unsure if I can really attend in 2022 for health reasons, but can work with people or a team locally (SF bay area). I live in the east bay near 580 / 680.

The technical aspects of solar / battery / inverter design / selection are not really a problem, so that part is relatively easy for me.

The details related to a solar panel setup that can actually withstand the conditions are BM are more exciting to figure out and I could use some advice in that area.

Size wise, they are roughly the size of full size suite case, so ~ 12 x 20 x 30 inches.

My initial idea was to use a heavy duty ladder and mount the solar panels on it - some facing east, some facing west.

Open to ideas / suggestions or if anyone or any teams would like to participate.

Thanks

Harry

When converting single phase AC to three phase, we employed inverters and motor speed controllers/AC drives, and their electronics are essentially the same. We had a lot of issues with motor windings arcing to the bearings in Maneurope compressors twenty or so years ago. We eventually located the AC Drives as the cause. The issue was resolved by switching manufacturers.
In addition, it is known that buildings with a lot of computer equipment can overload the neutral with third order harmonics produced by the power sources. Following a few building fires, the NEC Code was changed to exclude smaller neutrals. On electronic devices, I wouldn't apply a modified sine wave. Considering you just have that, you can probably get away with it, but not worth it if buying new inverters.

Thanks - The systems that I build have outputs for:
- 12 volt DC
- 24 volt DC
- USB
- Cig lighter
- 120 vac single phase / very high quality sine wave with a very low THD.

They are not setup for 240 vac, split phase or 3 phase.

[HarryN]

Quick update on the solar and power system portion.

The electronics and batteries are in the case.

The solar panels mount on the modified 6 ft. electricians ladder.

The camp that this is for is supposed to provide the refrigerator so no photo of that part.

In order to make the images smaller, I converted them to BW and compressed them so that they don't tax the forum.

2022 aug 22 bm ladder rack bwc.jpg

[HarryN]

Now with the panels on it.

I originally just used some cables to support the panels, but having the 2x4s attached made it a lot easier for me to do by myself.

Everything is 6 ft long or less to make transportation easier.

Some additional straps and tie downs will be added on site.

2022 aug 22 bm solar setup bwc.jpg

[motskyroonmatick]

We ran our welder off of this coupled with my travel trailer system all week long and powered all of the interactive portion of camp. Solar array was roughly 3200 real watts at solar noon. Array was connected to an all in one inverter/charger/charge controller and 200 amp hour 48 volt battery bank. This system was always fully charged by 11am and we had plenty of power to spare when the sun was shining. It was a freaking amazing setup that gave us more power than I was expecting and gave us 24 hour a day power. I didn't even bother setting up an independent system to power the 3 chest refrigerators we have in camp. Just plugged them in to the travel trailer and this.