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Archive for the ‘Appliances’ 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.
Tuesday, November 18th, 2008
We own a home which is “off grid”. Rather than use a wood burning stove, I want to install propane and get a propane range. Problem is, we don’t want the pilot light burning all the time, and the existing spark igniters are all electric! The easy solution is to light a match every time I want to light a burner, but I’m wondering if there isn’t a way to modify (or build) a non-electric spark igniter that sparks when I turn the burner on (or that is powered by a couple of AA batteries). Got any ideas?
The answer depends on the brand and model of your stove. Most very basic stoves with no electronic displays or timers, will have a spark ignition system that uses little or no electricity except for the brief period the valve triggers the spark. However, we designed an off-grid solar-powered home several years ago that based on our calculations would only need the generator to run about 3 hours once a week. After completion, the generator had to run several hours every day to avoid a drained battery each night. We said this was not possible, and returned to the site with full metering equipment.
After checking every circuit, we discovered their General Electric propane gas stove used more electricity than the entire house! Since GE loves electricity, they designed their gas stove with a “glow plate” down next to the oven burner which glows cherry red the ENTIRE time the oven is operating! Needless to say, we sent this stove back and had the homeowner purchase a non-electric model.
I would not try and modify your gas stove. Check to see how much electric ignition and controls draw when off, and then when energizing the spark ignition. If this is too much, then dis-connect and light with a match. This way there is no pilot light wasting gas.
Thursday, November 6th, 2008
I am trying to find information about how to run my electric dryer and hot water heater off of solar power. What I can’t find is information about using my current dryer and water heater off of batteries charged by solar panels. If that is even possible. I have a family of seven and am trying to cut down on my electric bill. Any advice you have will be greatly appreciated.
Sounds like you need more than a solar power system to provide energy!
Forget the solar power for your dryer, it would cost many thousands of dollars.
However, a solar hot water heater has a much lower installed cost and with a large hot water tank could pay for itself in only a few years.
Monday, October 13th, 2008
I recently setup a small off-grid solar power system in my residence. I am using three 110w, ~6amp Mitsubishi 12v panels wired in parallel, charging two 12v MK/ DEKA Gel-Cell batteries with a 184 aHr capacity (at a 10 hour rate) wired in parallel. The controller in use is a Xantrex C40. The wires in use are all oversized (#2/0 AWG as between batteries and inverter, #10 AWG as between panels and controller and controller and batteries).
I have been running the system for about a month now. Is it too late to expand my battery bank capacity? I have received advice to the effect that once you initiate a battery bank’s cycles you can’t then expand the bank later on.
My problem is that I am discharging the bank too quickly. I have only a chest type deep freezer drawing power, and when the compressor is running it draws 10 amps. The compressor runs 10 minutes out of every hour. My bank and panels produce/ store enough electricity to run the freezer for a 24 hour period, but after a nighttime of no sunlight my battery state of charge is about 12.4 volts.
It is difficult for me to imagine that load that requires 10 amps an hour will defeat a battery bank that can produce 30 (183aHr x 2 = 363/ 12 hours = about 30 amps) amps an hour in a single night, but it has been.
In sum, may I add two more 12v batteries to double my bank’s size at this point? Also, does my energy consumption and battery depletion look accurate to you or is something amiss within the system?
Thank you for your time, and amazing articles.
You have several possible problems to deal with. First, you could have the worlds largest battery bank, but if your freezer removes each day more stored energy than you are putting back from the solar, it will only take a few days for this system to run down and never catch up. I would first determine if this load is more than you thought and it may pay you in the long run to buy a more efficient refrigerator.
For example, If you review my recent article about building a solar trailer, you will see eight (8) 350 amp-hour deep cycle L-16 batteries being charged by a 600 watt array. The array can actually be extended to 1000 watts when we set it up as a display, but when sitting next to my home we only use 600 watts of array. This system will keep the battery charged for months at a time and the only load is the refrigerator-freezer. However, it is $3,000 SunFrost refrigerator-freezer which I think still holds the world’s record for being the most energy efficient. Also, it is being powered by 600 watts of solar, not the 300 watts you are trying to use.
If you really want to do this and not need to increase your battery and solar array size, I would consider switching to a SunDanzer Model #DCF225 12/24 volt DC top load freezer and then you will not need the inverter. It will operate straight from the battery and I think the 300 watt solar array you have should easily power one of these unless you live in the extreme North.
Next, since your batteries are still new enough, I do not think you would get that much of a “mis-match” if you did add more batteries, but the problem is you are operating everything at only 12 volts and this is requiring you to wire everything in parallel which is not good. We sometimes wire batteries with two parallel strings, but when you increase the number of strings you can get all kinds of imbalance and even the risk of one battery string discharging into the other if it has a weak cell. If you do decide to increase the battery bank size and you stay with 12 volts, I would switch to 6-volt deep cycle golf cart batteries which would more than double your amp-hour capacity without having to make four parallel strings.
Friday, September 12th, 2008
I am looking for plans to build a kitchen wood-cook stove.
Thanks for your help
Here are is a link to plans for building your own wood stoves: