Off-Grid solar system:refrigeration

inthejungle

I am in need of a bit of help and wondered if someone could give me a few thoughts


Here is what I have for a solar setup


3 245w panels 735 total, 4 hours of usable sun, so 2940wh a day, all items in my house are running 12vdc, I do not invert anything


I have one Sundazer freezer, the larger type and that is great for keeping things frozen.

Our situation:

We are in the middle of nowhere in W. Africa, we are having a problem when rainy season comes we are cut off from supplies in the main city for about 3 months. This freezer does a great job of keeping items frozen and we can bring cans of other things.

My main problem is that we can't always eat everything in one day. We would like to save some things for a few hours to finish tomorrow.My wife wants to just freeze cooler packs and stick them in a cooler to create a fridge. I want to do something better for her.


I could purchase a new sundazer fridge, but money isn't there for that.

Here is my current thoughts:

When we lived in the city we had an older chest style 110AC freezer, could I convert this to run as a fridge DC?
If I did can I make it run 12vdc or would I have to run this on an inverter?

Is there a way to use this old chest freezer to keep things cold in any other way? I am a practical guy and don't usually care how things look, only if they work!

Are there any other ways that you could think of to keep things cool for 24-48hours without using a ton of energy? Using raw materials that I could get at any hardware store?


Thanks for your help

Ben

Blackcherry04

Re: Off-Grid solar system:refrigeration

I have one of these, it is a Refrigerator or Freezer, you set the thermostat, it's runs on 12 / 24 V and has a DC compressor. I have had it for 25 years and no problems. We freeze fish in it, cool off drinks. It's portable and can be used in a car / truck. I have the biggest one, they have all sizes. You can find them closer to where you live, so google them. 4-5 different companies make them. Be careful of the size and buy a big one, they mix up the capacity and it's tricky.

http://www.defender.com/product.jsp?path=-1|406|10789|86418&id=680834

http://www.campingworld.com/shopping/item/dometic-portable-refrigeratorfreezer-2-8-cu-ft-85-qt/43942

http://www.engel-usa.com/index.php?page=shop.product_details&flypage=vmj_genx.tpl&product_id=27&category_id=1&option=com_virtuemart&Itemid=59 ( one I have, has no fans , not cheap, for sure 25 years is a long time )

http://search.defender.com/?Action=2&AnswerId=62066&SH=QT1yZWZyaWdlcmF0aW9ufkI9cmVmcmlnZXJhdGlvbn5EPTI1fkk9UHJpY2V_Sz00fkw9MX5NPTd_&SI=88e30496-1c26-47d5-bfc7-195d8c502ff1
.

https://www.google.com/search?q=dometic+refrigerators&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a#hl=en&client=firefox-a&hs=dQa&rls=org.mozilla:en-US%3Aofficial&sclient=psy-ab&q=dometic+refrigerators+portable&oq=dometic+refrigerators+portable&gs_l=serp.3..0i22i30l7j0i22i10i30j0i22i30l2.4227.8183.1.9146.9.9.0.0.0.0.181.1297.0j9.9.0...0.0...1c.1.7.serp.rcy5g6A_6K0&psj=1&bav=on.2,or.r_qf.&bvm=bv.44442042,d.aWc&fp=61a1900d14fb6d01&biw=1178&bih=712

Do not confuse these with a Peltier Chip box cooler.
.

Muskoka

Re: Off-Grid solar system:refrigeration

This post would help with your suggestion, but I'll give you some numbers to think about, another option perhaps. My propane fridge just quit one me. I didn't repair it, although it's only 8 years old, I wanted to get away from spending $600 a year on propane just to refrigerate. To replace it would have cost $1600 CDN, no thanks.

I ended up buying a small 4cu. ft Magic Chef ac fridge and it works great. It has a separate top freezer that works great as well, no problem freezing items. The fridge itself I keep at 3 degrees Celsius, about 4 on the dial. I bought it at Home Depot and the cost with taxes was $300 CDN. I don't know if you would have access to something like that where you are, it's just an option.

As far as power requirements. It runs for about 10-12 minutes every hour, and consumes between 85-90 watts while it's running. The initial surge when it starts is close to 1100 watts, so you would need a inverter sized to handle that surge.

I also looked at the "offgrid" fridges and freezers, and there was no way I was going to spend that kind of money, considering the price of solar panels today. This fridge / freezer uses roughly 600 Watt*Hours [-BB. Bill] a day, quite easy to do on solar alone. Anyways, it doesn't help with what your asking, just some numbers for a alternate solution.

The fridge....http://www.homedepot.ca/product/4-cubic-feet-2-door-refrigerator/972046

Glen

Cariboocoot

Re: Off-Grid solar system:refrigeration

Guys, this one may be more of a case of what he can get for a refrigerator in Africa and then how to power it. The cost of shipping something from far away can be horrendous there, so he probably needs to stick with "locally available".

There are threads on here about converting chest freezer to refrigerators (it is basically a change in the thermostat). As for switching to 12 VDC, probably not. Many if not all of the newer refrigerators and freezers do not have motors that are easily accessible (all-in-one units) and in the end you'd require the same amount of power to operate the compressor anyway.

I think you're going to have to find about another 1kW hour of electric per day, or go with your wife's suggestion and freeze reusable packs to keep the refrigerator cool.

john p's simple conversion: http://forum.solar-electric.com/showthread.php?19001-reversable-conversion-of-chest-or-shelf-freezer-to-fridge-for-less-than-15

BB.

Re: Off-Grid solar system:refrigeration

Note that freezing water in your freezer will increase its power usage too--So, going with a true refrigerator may be a "wash" for energy usage.

The extra freezer energy usage will depend on how much ice you make and how often you do it. Also--If you are looking at long term freezing (months at a time, etc.), adding water bottles to the freezer does warm it some--So can affect the quality of the frozen food. So, keep an eye on how much ice you produce and its effect on the rest of the contents of the freezer.

-Bill

Blackcherry04

Re: Off-Grid solar system:refrigeration

Said he had no 120 v or inverter, so I came up with options. Here is a Option, cut a 2 " hole in the side of the Freezer and put a insulated tube / hose between it and a Cooler and use a 12 v muffin fan to bring in cold air from the freezer. You have a disk you could move across the outlet in the cooler to control the temperature.

WARNING ::

You have to figure out if there refrigerant lines where you cut the hole if they are under the "skin " of the freezer.

inthejungle

Re: Off-Grid solar system:refrigeration

THANK YOU so much for everyone's thoughts

Getting things over here is quite difficult and I try not to do it unless I need it and can't get it here. Things like deep cycle batteries, solar panels and such all had to be brought in. I could bring something in, but would want to make sure it is exactly what I wanted/needed. Usually I prefer to make things out of local items, makes troubleshooting much easier.


The freezer that I have is older, probably 15 years, I am sure it is not a all in one unit. Probably right though that by the time I get converted to DC it would use too much power.

I like the idea of venting the freezer to the cooler, only problem is that is a nice new Sundazer and I am going to go cut holes in it, the Mrs. may not like that.

One other added item that I could use, would be our old refrigerator from the city. It was a 220 upright with freezer and fridge together.


One of our friends recently brought in a Dometic small 12v cooler that runs, LP, 110 or 12v, I checked with her and she said that she would sell me it. This maybe the easiest option, but when I went to look at it, the specs on the back made me wonder


It says that it runs 12v 6.7a, 110 .67a it is a Dometic model RC4000egp like this

http://www.dometic.com/enie/International/Site/Caravan/Coolboxes-Freezers/Products/?productdataid=89971


This page says it runs 80w thats 6.6 so this sounds accurate. What do you think, I know this won't run all day, but it sure seems like it would use a lot of power.


What about using water and a small 12v fan to cool down this old chest freezer?

Cariboocoot

Re: Off-Grid solar system:refrigeration

The power rating on the Dometic is for when it is operating, not constant. That's the tricky thing about any device that is thermostatically controlled; the Watt hour use depends on how long it is actually operating for, which is variable. In your climate the duty cycle is bound to be high, but probably still not 100%.

Water + fan = evaporative cooling. Works in dry climates, but I doubt it would bring temperature down to the refrigeration level (<4C).

In short, it takes energy to cool things down (ironic considering what you're actually doing is removing energy) and that energy has to come from somewhere. Compressor-based refrigeration is actually fairly efficient, and can be made more so with attention to details like insulating cabinets and keeping the coils out of heat and in good air flow.

vtmaps

Re: Off-Grid solar system:refrigeration

inthejungle wrote: »

It says that it runs 12v 6.7a, 110 .67a it is a Dometic model RC4000egp like this

Beware of these... They are terribly inefficient on electric. They're not a bad choice if you want to burn propane.

--vtMaps

Rybren

Re: Off-Grid solar system:refrigeration

vtmaps wrote: »

Beware of these... They are terribly inefficient on electric. They're not a bad choice if you want to burn propane.

--vtMaps

I agree. I have an older one that I bought for my parents to use with their tent trailer about 25 years ago. I have it now and use it for drinks when we have a lot of people at our camp.

It barely stays cool when running on 12V. It works fairly well when running on AC, but I haven't measured the energy usage. It works really well on propane and seems to just sip the gas.

Blackcherry04

Re: Off-Grid solar system:refrigeration

I agree, a absorption system works poorly on any heat source other than propane. The 12v & 120v are both cartridge heaters and neither one produce enough heat to create the absorption cycle very well. As was said the propane flame is not much more than a pilot, but it creates enough heat for the cycle. There is also a big time lag between the time the thermostat call's more cooling and it reacts inside. If you load it down with hot food they have a hard time catching up. Another issue is usually if they will work on 12 V they also have to be hooked up to it before they will work on Propane and thats a built in drag. Something with a 12 / 24 V compressor is the way to go.
.

Rybren

Re: Off-Grid solar system:refrigeration

Blackcherry04 wrote: »

Another issue is usually if they will work on 12 V they also have to be hooked up to it before they will work on Propane and thats a built in drag. Something with a 12 / 24 V compressor is the way to go.
.

Mine starts fine without a 12V connection. It has a "push-button" type igniter.

Slappy

Re: Off-Grid solar system:refrigeration

http://en.m.wikipedia.org/wiki/Pot-in-pot_refrigerator#section_4. Ok chew me out for this one. Just throwing it out their probably wont work during rainy season but who kows could make one and help it along with a ice pack or two.

Blackcherry04

Re: Off-Grid solar system:refrigeration

Rybren wrote: »

Mine starts fine without a 12V connection. It has a "push-button" type igniter.

Then it probably has a " Standing Pilot " thats the best kind unless you want to waste a bunch of watts on a controller and igniter. What Brand is it ?? Most standing pilot stuff has been banned here, if it's classified as a RV refrigerator it might get some kind of a exemption.

gww1

Re: Off-Grid solar system:refrigeration

Slappy
I actually found your provided link interesting.
gww

mike95490

Re: Off-Grid solar system:refrigeration

Blackcherry04 wrote: »

Said he had no 120 v or inverter, so I came up with options. Here is a Option, cut a 2 " hole in the side of the Freezer and put a insulated tube / hose between it and a Cooler and use a 12 v muffin fan to bring in cold air from the freezer. You have a disk you could move across the outlet in the cooler to control the temperature.......

This will introduce a lot of humidity into the freezer, that it is not made to handle. I don't know what the results might be.

Rybren

Re: Off-Grid solar system:refrigeration

Blackcherry04 wrote: »

Then it probably has a " Standing Pilot " thats the best kind unless you want to waste a bunch of watts on a controller and igniter. What Brand is it ?? Most standing pilot stuff has been banned here, if it's classified as a RV refrigerator it might get some kind of a exemption.

Mine is a Dometic, very similar to the first one in the links a couple of posts back. Mine is just ~25 years older.

http://www.defender.com/product.jsp?path=-1|406|10789|86418&id=680834

Blackcherry04

Re: Off-Grid solar system:refrigeration

Rybren wrote: »

Mine is a Dometic, very similar to the first one in the links a couple of posts back. Mine is just ~25 years older.

http://www.defender.com/product.jsp?path=-1|406|10789|86418&id=680834

I'v had 3 Norcold's and they aren't worth much. They have a 12v controller board, thats a pain, the problem is without it, it won't work.

icarus

Re: Off-Grid solar system:refrigeration

To further confuse the issue. Dometic (as well as Danby and one other maker whose name escapes me tonight) continue to make standing flame absorbtion fridges. In the case of Dometic they make the RV service Electronic controlled series that ignightors the fridge as needed. The largest of these units burn ~1500 btu/hour. Since they come with unfinished cases, it is very easy to add insulation to the case on the sides , top and front, making them very efficient. With a evaporator and a condenser fan added on, mine have run times in the summer of ~30% down to ~10% in the winter.

The other series has complete cases (enameled steel doors and case) have a 12 vdc igniters, but instead of "going completly out" as the stat says the box is cold enough, they go to low flame, perhaps 200 btu/hour. These too can be quite efficient, since the low flame keeps the boiler temp up such that it takes less flame to bring the ammonia solution to a a boil, to make it curculate.

I have found over the years with dozens of these fridges that they are quite efficient if used properly (not on electic power!) and properly filled, not over or under filled. They are also very reliable. Our neighbor has one that has been burning continuously for over 20 years, with one thermocouple and one tstat change!

All that said, if I was building a house, or cabin off grid from scratch today, i would go with a larger pv system (since it is so cheap now!) and go with a conventnal energy star fridge. The price difference between a good energy star fridge and a good Dometic would pay for the additional PV, and you could do away with the propane. My propane costs me ~$50/month, perhaps 1/3 of thqt going to the fridge.

Tony

inthejungle

Re: Off-Grid solar system:refrigeration

THANK YOU everyone for all of your help


Here is what I hear, domestic unit is OK for propane use but 12v and 110 are not that great. I can get propane if I bring it up with me, but 9 bottles of US style BBQ propane bottles in my roof rack, may not be the best idea.

OK so that leaves me back to the drawing board


I can bring something else in with a 12v compressor but it is a lot of work and hassle.


Slappy, I have heard of this and did a bit more research and found a lady who tested this here

http://solarcooking.wikia.com/wiki/Pot-in-pot_cooler



She mentioned that on a 109F day it was at 74 so 35 degrees less than ambient. It runs about 90-95 here all the time that would be us at 60-65F. This is not quite cool enough for what we need to store. Plus we need to lower the humidity to preserve things.

We are looking to store, daughters meds, vitamins, produce, the things you would normally keep in your door.

My idea is what if we could do this but on a larger scale with an insulated box. If I took our old chest freezer, and filled it with dirt and put a large clay pot inside for food and such. This would lower ambient temp and get the pot in pot fridge accomplished.

I am wondering thought if this will work because it seems that the outer pot wicks away the heat, if this is so, then an additional pot would be needed and would the added insulation prevent proper cooling?

What about if we manually pumped water through the old cooling tubes that way the water inside was constantly cool? I could use a very small 12v aquarium pump to cycle through the water keeping the water cool

Any thoughts, any ideas, I am open for any non traditional ideas we live in the middle of nowhere so people don't see things when they are a bit ugly and unusual!


Thanks

Ben

Slappy

Re: Off-Grid solar system:refrigeration

Inter pot glazed to prevent water seepage from getting items wet. Outer pot provides the wickig. Your post make me think of greenpowerscience from a while back when Dan tried this in Florida and it worked but the environment is different than probably from your neck of the woods. I am going to try this this summer when it starts to get above the nineties and see if it works first hand. Cheers

Slappy

Re: Off-Grid solar system:refrigeration

One other possible way similar as another poster mentioned about cutting hole bit instead use a 4 inch sheet of foam board backed with ply board use as lid and two insulated flex pipe one with muffin fan inside with a variable resistor for speed adjustment. The two pipe will let the cooled air recirculate with out drawing in hot air. And use a self stick foam for a as the "door" gasket. Just a quick idea on the cheap. But it will put extra load on the freezer but it depends on how well this is done?

Slappy

Re: Off-Grid solar system:refrigeration

This way there wont be no damage done to your freezer, and that will keep. The lady happy. And should work until you can get something more permanent. Sorry for split post. But this smart phone is not smart.