Refrigeration 101

As summer draws closer, the last remaining challenge at Winsol3 rises up again: providing energy for food refrigeration.  Summers here can get up to 90F in July and August.
Over the years my biggest nemesis in balancing a comfortable lifestyle with net-zero energy remains food refrigeration.  This is a long blog on a very important issue for all net-zero and off-grid dwellers.

Let me start by reviewing common food storage techniques and then relate my attempts at solving this challenge over the last few years at WinSol3.

 

Food Storage:

In the old days (60% of households in the US owned a refrigerator by the 1930s, it was not until 40 years later that the refrigerator achieved a similar % in the UK) there were no refrigerators in most households.  Mothers (usually) did summer and fall canning of foods, some people dried or salted their foods for winter storage.  Nearly every household had some type of root cellar, and consumed seasonal and local foods only.

With the advent of cheap electricity, transportation and then cheaper labor, the green (agricultural) revolution bought food from faraway places to every ‘super’market in the world through a complex global supply chain.  In the USA every one calorie of food requires 7 calories of fossil fuel to get it there! After 30+ years of this fossil-fuel driven supply chain, we are accustomed to having any food at any time - and we feel entitled to it.

Bigger is better?

Gone are root cellars, cold boxes, ice houses/ponds and seasonal/local consumption habits.

Instead we have twenty+ cu.ft. double-door 'french' refrigerators that defrost automatically with an endless array of temperature and humidity controlled compartments.  Additionally,  American suburban homes have at least one big chest freezer (usually in the garage) where endless cold meats are stored endlessly.  Some buy a whole or half of a cow and keep it in those freezers for consumption months later. One of the sad facts is that over 50% of the food pushed to the back of refrigerators usually ends up in the garbage can.

The rest of the world is slowly catching up to the USA.  Even though most European and Asian households have small 2-4 cu.ft. refrigerators, I've noticed many of these new households having bigger and bigger refrigerators.

We have grapes from Chile available in all USA/Europe/Asia supermarkets in January.  We can have any food available to us from anywhere in the world 24/7/365.  With peak oil in the past, and rising prices and shrinking supplies inevitable, what will the future of this food supply chain look like?  One can only imagine its slow demise.  Are we going to go back to root cellars, canning, and ice ponds?  Probably not.

So what are the solutions?  That is where eco-village and local off-grid visionaries may provide some possible solutions.

Added note:  Off-grid homes usually have a propane powered    Sun Frost Refrigerator.   These units cost well over $1,200.  and use a substantial amount of propane gas each year.  They are 80% more efficient than off-the-shelf electrical refrigerators.

Now, back to WinSol3’s food refrigeration history. Here's the story of my food storage journey over the past 5 years, summarized into  four main areas: (Note:  I had a digital thermometer inside each cold box.)

#1 Try= small fridge

My first attempt 5 years ago, was to use a small ‘bar’ refrigerator.  These small refrigerators provide ~two cu.ft. of cold storage with a tiny freezer.  Their compressors draw about 3.5 LRA (locked rotor amps) as opposed to 20+ LRA for big fridges.   

Since there is an inductive load presented to an inverter, fridges have a high amperage surge as they startup.  My 3,000 watt inverter usually beeped (draws more than it’s rated amps) for a few seconds while the compressor surges on startup.   As long as I have bright sunlight (no problem in California summers) the small fridge worked fine.  After sunset, each time the compressor cycled on, the inverter load was exceeded and eventually the battery voltage went below 12.1 VDC (my low voltage setpoint).  I tried putting frozen water bottles in and keeping the fridge off overnight, but could not continuously freeze enough water bottles during the day  for the small freezer.

#2 Try = two cu.ft. cooler inside a cold box

My next try was keeping the food cold in the fridge during daylight hours and transfering critical foods like chicken, seafood, etc into a cooler overnite.  That lasted one week before I realized that doing this every summer day was going to be labor intensive.  I tried transferring frozen water bottles into the cooler and eventually transitioned totally to the cooler using the fridge to occasionally freeze water bottles.  Several people on the internet commented this was their preferred method.  Again, after a few weeks I also gave up on this, because it was still too labor intensive.

I purchased a new, bigger, more insulated cooler.  I made a cold box under the kitchen counter (the bottom of the cooler was in direct contact with the cold basement) and put in extra 4”of XPS insulation all around it – except for the bottom; and placed the cooler into the box.  This ‘cold box’ is still used to this day with #3 ice added.

#3 Try = Success! Cold Box + purchased Ice

Every time I went to the local grocery store I started buying ice blocks to put into the cold box cooler.  This worked great – the cooler inside the cold box would stay below 40F for over 7 days with the ice block.  Eventually tho this was tiresome, as spending money and transporting ice blocks from a store was not my idea of sustainable living.  So I purchased an electric ice maker.

#4 Try = Cold Box + PV produced ice.

My thoughts turned to what other mainstream consumer products were available that could make things cold without upsetting my solar powered inverter.  I researched various portable ice makers and purchased one for $99.  

It works great, and I can make about 3 pounds of ice each summer day in bright sunlight with my PV panels.  I use the ice for my cold drinks and put the rest into the cooler inside the cold box. It’s still a bit labor intensive, but it works.

(Note:  from November to April at WinSol3 there is no issue since snow is readily available)

Changing lifestyle cooling practices

The real issue in food cooling is having the convenience of cold storage at our finger tips with minimal efforts.  As RMI + Avory Lovins recently have stated:  'We don’t use energy, we use energy services.' 

The energy service I wanted was to keep certain foods cold.  

I started researching how others had done it before compressors and cheap electricity were available.  There’s a lake off Hwy 50 between Placerville and Tahoe called ‘Ice House’  named appropriately because here pioneers of the 1800’s skimmed ice from the top of large ponds specifically designed for this use – and delivered the ice via heavily insulated cold boxes to the supermarkets in the hot summer California Valleys.  Image the embodied energy of human labor on each ton of delivered ice!

But the real solution to refrigeration lies much deeper:  our lifestyle of eating and preparing food and basic physics.  Language is also important: instead of calling it refrigeration, I like saying ‘cold food storage’ – which is really the energy service we want.

 The key questions are:

(a)             which foods need which temperatures for how long?

(b)             Which foods do we need for nutrition?  And how long from harvest to eating?

The latter is all about choice.  As in any lifestyle choice, this is a personal question and no science or debate can convince someone to do with or without a certain food.  But once I had the answer to (a),which can be found through siteslike this one from Virginia Tech:

 "For optimal quality and safety, dairy products should be stored at refrigerated temperatures between 34°F and 38°F, meats between 33°F and 36°F, and eggs 33°F to 37°F.  Fresh vegetables and ripe fresh fruits should be stored between 35°F and 40°F.  Always store refrigerated foods at temperatures less than 40°F."

It was really easy to change my lifestyle choices with some knowledge of the refrigeration energy it takes to cool foods and to change a little bit of lifestyle.

My keys to net zero energy Food cooling

The first step to reducing an energy profile for cold food storage is to inventory your households eating habits (especially during hot summer months):

My personal food habits include:

1. Eating ice cream in the summer
2. Seafood once a week.
3. Papayas, pineapple, yogurt, eggs,

Given these personal food habits,  I had to adjust my life style a bit. Instead of ice cream, I make smoothies with fresh berries and ice cubes from the icemaker.  I only store seafood  about once a week and use the local grocery store as my 'outsourced' freezer supplier - its free! (cold storage only :-)

A personal note:

I don’t freak out about having 'perfect' food - I don't understand why a little blemish on a strawberry or apple make some people throw the whole thing away.  I am a firm believer that farm kids are much healthier than city kids because of their exposure to all kinds of bacteria at a young age.  I also believe we need to continue this throughout our adult lives keeping our immune and other systems tuned-up.  So,  I do not abhor eating a little 'dirt' every now and then. Since all my vegetable beds are biodynamic (no chemical fertilizer or spray, +++), a little bit of dirt on the lettuce or radishes is no biggie!

If it wasn’t for my experimenting through steps #1-4 above, I don’t think I can go into step #5 below.

Step #5 – my ultimate solution for cold food storage

It’s a five step process:

First, and foremost are WinSol3’s gardens, greenhouse and hotbox. These three places can provide me with green leaf veggies and more, year round.  Nothing, and I do mean – nothing! – beats freshly picked produce from a garden where biodynamic principles are practiced along with local rainwater.

Second, are my de-hydrators and canning processes. This takes either my, or a local neighbor’s excess harvest and prepares it for long term storage.  I like to store dried herbs and mushrooms this way.

Third, is the root cellar which is currently under construction in the basement of WinSol3.

Fourth, is the cooler within a cold box and summertime PV driven Icemaker (#4 above).  Right now that is located below the kitchen counter, and is a bit awkward to access.  I wish I had built an upright vertical cold box.  I am still contemplating on doing this – the added convenience of not having to stoop down to access cold food as I get older (20" is the lower limit). 

Fifth, are for special occasions for parties, tours, weekend visitors, etc.  This is outsourced to the local grocery store and perhaps an ice block.

Future cold food services

Technology will undoubtedly change and improve as our fossil fuels diminish.  There are new chemicals and wonderful innovations coming along. Check out this Ted Talk by Adam Grosser on a tiny fridge that uses no electricity for medical deliveries to remote areas.

I wonder what will happen first:  Changes to our food supply and habits, or new hi-tech, appropriate + balanced solutions?

Personally, I’m not waiting for the promise of hi-tech.  Changing my cold food habits has been a long journey, and I still have a ways to go.  Change is difficult, if it’s not – you’re not changing.  Try putting your sweater or coat on with the opposite arm – see how weird it feels? That’s change.

Adsorption refigeration is making big inroads in the cooling industry.  This proven technology has been used by industry for decades.  With the advent of affordable solar thermal systems and California’s sunny summers, solar hot water with adsorption chilling is a huge promising industry. Stay tuned.