Saturday, January 24, 2015

Off-grid refrigeration - chest freezer as a fridge

Today's topic is off-grid refrigeration.  Honestly this is a lot more complex topic than I expected it to be.  Most people really don't know what consumes energy in their homes, or how much.  Only by reading, doing an energy audit with a kill-a-watt meter, and doing some simple math do we start to figure out that our refrigerators eat a large portion of our household electricity. I speak for myself included that when I started into all of this I didn't know how much or where my energy was being consumed.  Over time I figured it out and it helped me to get a handle on my power use and it cut the bill a lot, but I wasn't ready to take the real leap and prepare to go off grid. Now this gets serious! :-D

Now before running off and doing anything I first started by asking myself some basic questions. For example can I live without a refrigerator?  How did they do this back in the pioneer days?  What would the cost be to try and produce the electricity to feed this thing we call a refrigerator?  Is it worth the cost and complications to accommodate this? 

Well the mental exercises began and the research project was under way.  I went back and forth looking at the options.  Power requirements, cost, conservation ideas, and comparison to old world technologies such as a root cellar.

Back in the old days we would have worked with a root cellar, or an old dry well, or some other way to go under ground, insulate with straw, hay, and preserve winter squash, root vegetables, and some fruits like apples, cabbages etc.  We would have packed a root cellar with canned goods and would have been living off of the things we saved from that years harvest through the winter.  This is a great idea, but there are a few complications.  First I don't currently live near or on my off-grid homestead.  Second I have hired contractors to come out to the property to do work and they didn't do it right, wasted my time, money, and I ended up just having to redo things.  So when I started calculating cost for excavation, and construction of a root cellar at this time and having someone else do it for me I realized we are talking 2000-3000 bucks.  And this still only addresses longer term storage and not really day to day use. However it could be made to work.  The cost factor and the fact I cannot be there to supervise the construction really makes this move a non-starter at this point in time.  However I will be planning on doing this as soon as we get more pressing issues solved on the property like water, and a stove for heating, cooking, and sanitizing water.  So lots and lots of projects in line before I get to the root cellar.

Next point that comes to mind is that while I am still living in an urban environment I would like to transition to a very low energy footprint just as if we were living off grid on our property.  So we began changing things here at the house as we work to get our consumption down to a target I think we can meet with solar and wind power.   We have a lot of work to do to get there, but one of those things we could do is to conserve and the largest consumer is a refrigerator.  So if we really want to shoot for an off grid lifestyle it is time to make changes today.  We started shutting things off, putting them on power strips and turning them off.  We moved from our electric stove to a portable propane cooktop.  We looked for any way to reduce what we use.  We still have a ways to go like changing behaviors like the dishwasher, and using a the clothes dryer.  I have a clothes line, but getting everyone on board with using it takes some coaxing and work. So we still have lots of room for improvement.  I am looking forward to seeing the progress so far on the next bill.  Conservation is key... The cost to produce the amount of power we use would be insane if we were to build a solar and wind system to address our current energy use.  So the only real answer is to conserve.

Back to Refrigeration:
So we started looking at the lowest power consuming refrigeration units on the market.  Looking at solar and propane specific units.  Looking at the consumption figures.  We looked at and looked at the most efficient models available and weighed the costs.  All of them still seemed to use more power than I was prepared to produce.  Then my searches stumbled upon some folks talking about an off grid solution by converting a chest deep freezer to a refrigerator.  I started digging and watching the videos.

Basically the concept is sound. The chest freezer is highly insulated.  When the door is opened the cold air does not escape and tumble out of the fridge out onto the floor.  No wasted energy and very efficient.  Next the idea is to put a external thermostat on the freezer to control the temperature.  You set the temp you want and the thermostat power cycles the freezer on and off to keep it within a range of temps you set.  They make these thermostats and many people who apparently like beer a great deal are converting these old freezers into what they call a kegoratror or some variation of that...  You get the idea.  Well I found a few people who have done this for off-grid applications also.  They reported a great reduction in power consumption on their power system once they made this conversion.   The concept works.  Power consumption reduced greatly and refrigeration needs still met. 

The downsides?  Well crawling around inside of a chest freezer is a pain in the behind to put it mildly.  A system of organization would be needed to use this as a fridge.   Maybe some plastic bins and baskets so that the items can be arranged and accessed more easily and managed.  Secondly I see that some people reported that the more your in and out of the fridge that condensation becomes an issue.  So they felt it was needed to raise things up off the bottom of the conversion fridge, and to wipe down the walls when your in there.  There is a drain plug at the bottom of most chest freezers so it shouldn't be too difficult to manage moisture, but that may depend on your location, amount of humidity in the air and how often your in and out of the fridge. 

Overall it looks like a good idea and fit even with the compromises.  So instead of looking for an old deep freeze to re-purpose I wanted to go with the most efficient model I could find.  Chest freezers are not that expensive to begin with unlike a full blown fridge/freezer combo.  I was looking for something small as we don't need a large capacity fridge.   We already have a small chest freezer that we can continue to use as a freezer and will use the new conversion fridge as a fridge only.  So I hit up and found the most efficient model that was in the 7cf-8cf size range.  I settled on a 8.1cf unit that uses 189 kilowatts a year when functioning as a freezer.   Of course when we put it on a thermostat and run it like a fridge I fully expect that power consumption to be at least half of that. 

So I found the freezer online and placed my order.  I get a call a week later to tell me that they were shipping our freezer but found it was damaged.  They didn't have another one in stock.   They offered to give me a big price break on another freezer if I would accept the replacement.  I told them I had specifically chosen this model due to the power consumption figures and I will be using it for an off-grid application.  They understood and told me that the new unit will be arriving by the end of the month and they will be shipping it to me as soon as they have one.

So now we wait.  I will be posting the data comparing my existing fridge with the new one when it arrives to see the differences in the consumption figures.   Hopefully this will knock a nice chunk out of our monthly kilowatt usage figures and get us much closer to where we need to be.  We will post our data so you can see for yourself and maybe this will help you decide how you want to address your own energy consumption and your refrigeration needs.

The model we chose is:
DCF081A1WDD    Danby White 8.1 Cubic Foot Chest Freezer

For a thermostat there are several options to choose from.  There are some cheap Chinese imports that frankly I just didn't want to mess with all the conversion stuff that I saw other people doing.  By the time I added up a project box, wire, shrink wrap, outlet, and thermostat you almost have as much into it as buying one prebuilt like the Johnson Controls one that I found.  You have two Johnson Controls models to choose from that I found.  I went that route for the controller.  Simple, plug it in and go.  No messing around.  Of course if you have the time and want to play then by all means get the inexpensive one and build it.  I hear they work fine.   

The two ready made options are:
Johnson Controls Digital Thermostat
Johnson Controls Analog Thermostat

If your considering your refrigeration needs and trying to figure out how to make it work a chest freezer with a thermostat might just be just what your looking for.  Personally I will feel a lot better when we are on our property full time and a root cellar becomes a viable option, but until then we are improvising solutions that hopefully will have long term payoff.  Trying to provide power from solar or wind to any conventional fridge just wasn't an option and many of the other solutions I have seen offered really didn't add up to a solution that would work for us.  Always look for people to provide actual data for how many watts their fridge is consuming.  Too many folks just didn't provide enough data and worse yet you follow up later on with them and you see them replacing what they previously recommended because the power consumption was still too high.  Many of the 12v DC powered options out there either draw way too much power or they are insanely expensive.   The solar specific fridge market is also just way over priced for what your getting.  So I think by buying a very efficient conventional deep freezer and using this controller we can get most of the benefits of these very high dollar solutions at a small fraction of the cost.  I will keep you posted and post the data on the before and after.

I hope you found this helpful.

Take care and God Bless,


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