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Archive for the ‘Refrigerator’ Category
Friday, May 22nd, 2009
Do you have any experience with propane refrigerators? If so, what model small refrigerator do you recommend for a small cabin that will be used year-round?
Thanks so much,
We have included propane refrigerators and freezers on many solar off-grid homes, but since most are based on heating a gas to cause the cooling cycle, I would not use them in an application where the home is not occupied for many parts of the year like a typical weekend cabin. After the first few years there are some maintenance issues that you need to take care of to keep them operating properly, and they do use a lot of propane.
We have switched to the 12/24 VDC small 50 liter refrigerator or the larger 8 cu.ft. top load freezer by SunDanzer that operate from solar charged battery. They require very little solar power to operate due to their very heavy wall insulation, and do not use a flame like the propane units. I think if properly installed they are a much safer and offer a longer life solution, although they are more expensive.
Thank you for your quick reply
If you do not mind another question, I am wondering what brand of 50 liter refrigerator would you recommend? And, pardon my ignorance, but what does the “V” in VDC mean? Does it mean voltage?
You can see I am at the beginning of the learning curve relative to using solar energy/alternative energy sources to achieve energy independence for a small cabin.
SunFrost and SunDanzer both make really great super-efficient DC refrigerators and freezers. All SunFrost models are stand-up designs, and all SunDanzer models are top load. You may like the stand up version better, but they are pricey.
I have worked with both for almost 15 years and each has their advantages. Up until this year, the SunDanzer units were in the 8 cu.ft. range which is fairly large. This spring they came out with a 50 liter unit which I found to be perfect for a week-end cabin type application due to the small size and very small battery usage. However, it’s a top load and must be ordered either as a freezer or a refrigerator, but not both.
When we say “VDC” we mean “volts DC”.
Click Here for ome other useful solar terms
Hope that helps.
Friday, January 23rd, 2009
I just read your article on solar powered refrigeration. I agree that efficiency is very important as being off the grid, you have a limited amount of power. We are generating our own solar power but we run 120vAC from an inverter. Your article was for 12vDC fridges and freezers. I was wondering about 120vAC fridges instead. I would think they would be much cheaper but perhaps really efficient ones are not available as generally power availability is not a problem. If you have any thoughts on 12ovAC fridges vs 12 vDC fridges, I would appreciate hearing what you have to say.
Dwight Yachuk and Lucy Willemsen
Dwight and Lucy:
You said you had a solar powered inverter but did not say if you were actually using it to power your refreigerator, or you were just considering adding a refrigerator to your system and were not sure which to buy.
I will admit that refrigerators and freezers have really improved in the past 3 or 4 years, and they are now putting much more insulatation in the walls and using more efficient compressors. However, if you have a small solar system like I described for an off-grid cabin or weekend retreat, any refrigerator or freezer will be a really big load on the system.
The bottom line is, I have not in the past 20 years found any 120 volt AC refrigerator or freezer that was even close to the low energy usage of the solar DC refrigerators and freezers made for off-grid solar power systems.
For example, a SunDanzer 8 cubic foot freezer is rated to draw 0.36 kWh per day at 70 degree room temperature, and a SunDanzer 8 cubic foot refrigerator is rated to draw 0.09 kWh per day at 70 degree room temperature.
The 12 cu.ft. SunFrost refrigerator/freezer requires 0.29 kWh at 70 degrees room temperature, and the 16 cu. ft. SunFrost refrigerator/freezer requires only 0.48 kWh per day at 70 degree room temperature.
Now compare this with the Energy-Stare rated super-efficient General Electric 14.3 cubic foot refrigerator/freezer which draws 1.4 kWh per day, or 3 times as much as the same size SunFrost.
If I had a very small solar system and an off-grid weekend cabin, the much higher energy usage for a standard 120 VAC refrigerator, plus adding in the energy conversion of about 10% for the inverter, means your you may not have the power or batteries to power it.
If you live in a larger solar home with 4 to 6 kW of solar array, then buying a high efficiency 120 VAC refrigerator may not be a problem for your system, but it still will be the highest energy user in your solar home.
Thanks for the very informative reply. I had been thinking about adding an electric powered fridge to our new “winter” home we are designing for across the lake where our present “year round” and future “summer” home is located. We are on the east side of a narrow lake and only get 4-5 hours of sunlight a day now, with no sun before noon, so we are very solar challenged, hence building a new home to take advantage of the winter sun.
I had only been thinking of 120 VAC systems, but since writing you we thought that we could run dual 120VAC and 12 VDC systems off the same battery bank, even to the point of wiring the house for both. In that case, putting in a 12 VDC fridge, especially a very efficient one, would be practical, and economical powerwise.
We are still in our investigative phase but running a dual system is starting to make sense. The alternative would to use a propane fridge just as we are using now in the cabin. Thanks again for the info.
Dwight and Lucy
Dwight and Lucy:
I do not think what you are planning as far as the wiring you describe is the way to go, and there are too many technical reasons why to list here.
I strongly suggest that you enlist the help of a solar power system designer to guide you before you build. Otherwise, it may be costly to make the needed wiring corrections after you close in the walls.
Sunday, December 21st, 2008
In this article you said you like MPPT solar charge controllers and then endorse the Morningstar Sunsaver Model #SS-10L and 20L, a PWM controller? Is the (4x) more expensive MPPT controller worth it?
Thanks for any info.
Like everthing else, it depends on the application. If I am designing a small system under 20 amps, which would be about 200 watts of solar at 12 VDC, then to keep costs down I will usually go with the Morningstar line. These are very rugged and have lots of features you need with many smaller systems like programmed on/off control for an exterior light and low-battery cut-off of the load to prevent battery damage.
On larger systems where you are spending several thousands of dollars for the solar array, the extra annual output you would get with a MPPT charge controller is worth the extra cost. These larger charge controllers have larger wire terminals on display meters which the smaller PWM charge controllers do not. There are actually several newer brands of charge controllers now available which are also very good.
Good Luck and FYI, don’t wire your PWM to your MPPT or you will be SOL and should go ASAP with short ETA to hospital for EKG and MRI,
Thank you for the distinction. I currently have a small system (50w panel, 12V) I am learning from and could grow slightly bigger. It is only powering 12v devices off the charge controller with a 51amp/hr battery.
I am currently using the Morningstar SS-10 and I could benefit from the low-battery-cut-off and programmed on/off control. I would also like an amp/volt display that some seem to incorporate now. Any recommendations?
Thanks again for any info and any further TLAs.
Since you are already using the Morningstar line, they have a next size up model with a display window that will do what you want. However, until you increase your array size I would not spend the money.
Tuesday, November 25th, 2008
I read your article from Issue #102 entitled “Solar-Powered Refrigerators” because my family and I were considering purchasing one for our backwoods cabin. It was very helpful and I have recommended it to my family as a good source of information but I was curious to know if you still had the SunDanzer and Sun Frost solar refrigerators and if so, how they are holding up with time.
We have owned both an RF-16 and RF-19 size SunFrost refrigerator/freezer since 1994 and two SunDanzer top load freezers since 2001. Since we have had the SunFrost units longer, we have had more repairs. Although SunFrost may still be the most energy efficient refrigerator made and are clearly designed for very long life, they have in my opinion, several problems that only recently have seen any improvement.
First, the door latch is plastic with slotted screw holes and both sides are attached with screws. If these get out of alignment, and they will, when you close the door they break off. Although they are cheap and easy to replace yourself, you better have several on hand. Second, the seals around the doors are made of a thin plastic strip that has been “crimped” into a “V” shape with peel and stick adhesive on one side. These also are low cost and easy to replace yourself, but they need to be replaced about every 2 years. The thermostat for the freezer compartment will fail, and this was clearly anticipated as the design includes a spare sensor built in when manufactured. When this sensor fails, and it will, you have to abandon the mechanical capillary-tube temperature sensor that controls the compressor and install a new electronic sensor that you connect to the extra sensor wires. The earlier models also had very-easy-to-break adjustable door shelves that would always fall off and break when over-loaded, but a recent design change has made these much better.
Finally, to achieve the very high energy efficiency, no SunFrost models have automatic defrost of circulating fans, so expect to learn how to defrost a freezer and refrigerator like your parents had to do. This sounds like a minor problem, but if you live in a humid area like we do, you can build up several inches of ice in the freezer in only a few months, and the back of the refrigerator section can build up an inch of ice over the entire surface in about the same time. Once this happens, the refrigerator section will no longer keep foods below 40 degrees as all the heat removal is going into keeping the ice from melting and your food will soon spoil. Since the refrigerator/freezer models have separate compressor and temperature controls for each compartment, it is possible during de-frosting to only turn off one compartment at a time. To avoid damaging the plastic interiors while chipping off the ice buildup, we just move everything into the section that is still operating, turn off the other section, and prop open the door. In about an hour you will hear the ice start to fall, which can usually be removed as one or two large sheets all at once. Then a quick wipe down, then reverse the process and do the other compartment.
The SunDanzer has a type of “lung” or bladder somewhere in the inner workings that expands and contracts when you open and close the top door. They claim this reduces the unit “sucking” in warm humid air after you re-close the lid due to the lower interior air pressure from the cold. This actually works as we have gone as long as 2 or more years without defrosting. To appreciate what is going on, if you close the door of a SunFrost refrigerator/freezer, you can clearly hear room air being drawn into the interior as it makes a hissing sound as it passes the door seals. SunDanzer does not make combination refrigerator/freezer units, while the SunFrost can be a 2 door unit having both sections. I thought I would have problems with a top load freezer getting access to foods near the bottom, but all SunDanzer models include a system of top racks mounted in a track system that lets you move the upper half of frozen foods sideways to expose what is stored below.
If you need a super-efficient 12 or 24 volt DC refrigerator that includes a freezer section, and you can handle the nuisance repairs described above, then I still recommend the SunFrost models. They are very expensive, but with regular maintenance they will last and last. If you can get by with just a freezer or just a refrigerator that must be super efficient and run on 12 or 24 volt DC, or can afford to buy one of each, then I would recommend the SunDanzer. I think they are just as energy efficient and require much less maintenance, but again they are top loading.
On a final note, all models from both manufacturers are either 12 or 24 volt DC unless something has changed recently, and since most off-grid solar homes are starting to use 48 volt battery banks to reduce wire sizes you will need a DC to DC converter to use any of these on these higher voltage battery systems.
Wednesday, August 20th, 2008
We want to buy or build an Ice box for our cabin, but I can’t find any information online to do this.
Coolers tend to fill with water and waterlog our food.
Any suggestions on building an icebox?
Yes, you can build your own DC refrigerator. My first suggestion if you are low on cash is to buy a small propane powered RV or boat refrigerator/freezer. These are small and do require manual defrosting, but will use very little propane and no electricity. However, their freezer sections are very small so don’t expect much ice.
There are several companies that offer a 12 volt DC compressor and coils pre-plumbed and charged, and all you need to do is build an insulated box.
Click Here for one of many sources for these kits.