This is a proposal for a refrigeration system which is intended to eliminate the need for electricity as much as possible. What follows is my refrigerator and freezer; it is not for everyone, and it is not designed for commercial sale. I have no such aspirations to patent or in anyway restrict the free application of my ideas. Potentially, if a favorable method of low energy cold storage is found, I might manufacture and sell components or custom installations, but this is not the impetus for my efforts. This is purely a work of passion and a long time desire to create refrigeration capacity outside the paradigm of fleeting cheap energy. Society is far too complex and interconnected, with the technology that supposedly freed us from drudgery, has instead taken on a life and evolutionary path of it’s own, leaving our roll as the biologic hosts, and committing us towards a path of diminished autonomy, guaranteed collapse, and potential extinction.
I’ll be discussing methods to lower the energy consumption of standard refrigerator freezers, the use of passive seasonal ice to offset heat load, two-phase thermosiphons to conduct heat, slurry ice generation, thermal ejector refrigeration, wood fired absorption refrigeration, and perhaps a few more topics.
With the exception of being applied in a slightly novel and conceivably original way, none of these ideas are truly new in the sense that they were pulled from thin air. Quite the contrary, they come from the study of refrigeration technologies as they go back two centuries and beyond, where their application made economic sense given the resource limitations at that time. Although I wish to build these things and demonstrate their effectiveness, I realize they will take years of experimentation and hard-won knowledge that only comes from empiricism.
I also know there are a handful of low-tech enthusiasts that would appreciate a discussion of alternatives to a store bought refrigerator, as the model of industrial manufacturing only provides temporary nutritional advantages, setting us up for a rough withdrawal when the bottom of the fossil fuel bucket is scraped clean, and a handful of people at present want to cut ties with the technosphere. Any individual interested in these concepts is encouraged to experiment with them and contact me in regards to collaboration. Much of what follows requires a level of expertise which I do not yet possess, but I have built enough devices along these lines that I feel the problems can be solved. Many of the designs are kept technically simple and largely avoid controls and valves as we progress. These I feel, can be approached by a refrigeration novice with a desire to do some research and put the time in. There are a range of projects that get progressively more complex in the sense that the optimum operational target gets smaller and farther away, so it will only come with patience and practice. There are a handful of concepts that generally follow a theme, mixed and matched, they form several possible scenarios that depend on site specific characteristics and practical limitations of size and space available.
Energy consumption per unit of refrigeration (efficiency) is not necessarily the ultimate goal. Instead, passive systems are sought wherever possible, and when active energy inputs are required, low grade sources are preferred over high exergy electricity. Some of the initial work will in fact use electrically powered compressors, but the long term goal for these is to be backup systems during experimentation, or for unseasonably warm winters where the passive systems fail to provide year-round refrigeration. The use of DC compressors may be explored, however a photo-voltaic panel supplied compressor isn’t viewed with any higher value than a grid-tie alternating current compressor. Over the long term, there will likely be a need for DC electrical supplies, but this is intended for some night lighting and communications only. Small AC compressors are practically free, they can be readily salvaged from defunct refrigeration equipment, and it is possible to run these from an inverter or generator, in the event of brief power outages. The main goal is to severely reduce or entirely eliminate the need for electricity, not to simply switch to an alternative source and get lost in producing more of it. I know of no practical application of electricity, where the production does not incur negative environmental externalities.
In the coming installments, I want to explore refrigeration demands, concepts relating to the offsetting of heat load seasonally, the choice and principles of individual technologies, and the practical implementation of them into a home refrigeration system. As I stated before, this is my refrigeration system, and will not be suitable for all settings; it is specific to a temperate climate with sub-freezing winter temperatures, although many aspects of it could be adapted to other climates as well. Rather than explore the wide range of refrigeration options available, I’d prefer to stick to the ones I deem appropriate in the sense that they can largely be constructed with basic supplies, tools, and skills.
Food Storage Requirements
No one truly needs rerigeration to survive, but it does make life easier. Many other methods exist to preserve calories and nutrition, including canning, drying, pickling, fermentation, and root cellars. I have done some of this in the past and will continue it in the future. As a vegetarian, I can focus more on these methods than someone needing to store half a beef for the winter. Nonetheless, refrigeration is useful for keeping certain foodstuffs fresher, longer, and prolongs the life of leftovers over the short term. Freezing certain vegetables (especially when vacuum sealing) is useful for preserving crisp vegetables for months or even years, so both of these methods are desirable.
Two spearate units are to be used intitially, just like anyone would have: a stand-alone refrigerator in the kitchen, and an upright freezer in the basement, or other stable temperature environment.
Choice of Units
Although somewhat convenient, a refrigerator/freezer combo is energy hungry. Not only are very low evaporator pressures (and high power with that) needed to keep the freezer at a low temperature, forcing the compressor to work harder and longer, but the air exchange typical in these systems, circulates between the two compartments and leads to excessive drying of the goods in the refrigerator region. Produce drys and wilts more quickly, the large temperature difference between the moist air and the evaporator causes it to freeze up, and the unit requires regular defrosting with a built-in heating element leading to further energy waste. Additionally, these units have circulating fans which do provide for even cooling, but also consume yet more energy and are prone to failure.
Simple stand-alone refrigerators of earlier days worked off the same principles as their ice refrigerator counterparts where an elevated evaporator promotes natural circulation and slight temperature differences in the cabinet. Different foodstuffs are kept in different temperature regions for best results. A sufficiently large evaporator will not operate at as low of temperatures, and thus will require less power consumption to maintain box temperature. Refrigerators of the 1940s and 50s are a good example of a well thought out design. The evaporators did tend to run low enough to produce a few trays of ice, but simple convective heat transfer was enough, and didn’t require a fan. These beasts of the day also had thick, heavy walls, good sealing doors, and were very stylish too. I certainly wouldn’t mind have a late 40s GE in my kitchen.
Another option is the simple “Freezerator”. Several people, trying to shift to an off-grid lifestyle, have modified chest freezers by the simply wiring a different thermostat to maintain refrigeration temperatures. This has the effect of severely lowering power consumption. Two notable drawbacks are the inconvenience of of a chest style, and the pooling of condensation. Another option is to find an upright freezer with evaporator coils in the shelves. This has the advantage of being more convenient for access, it also has a large evaporator surface area for lower power consumption, but condensation dripping onto food is still a problem. I know one individual that has done this for a few years using an oddball under-counter freezer.
Another option would be to install a custom evaporator- large, and with a means to collect condensate. This is my preferred choice. Although I would like to have a nice mid-century fridge, practical considerations suggest it best to acquire an upright commercial freezer. These tend to be better built, heavier, with good door seals, and thicker insulation. Low energy consumption doesn’t seem to be a primary consideration in their design, so some modification with a new compressor system would be required. Commercial units are often forced air / self defrost, so they also have standard adjustable shelving systems, and wire racks, allowing for considerable customization, and better air flow than typical glass shelves found in domestic refrigerators.
I’m not a big fan of electric condenser fans either. Up to a certain amount of heat load, a black wire static condenser should be fine, or a “stack condenser” like is found on some older refrigerators.
Many of the same considerations for the refrigerator, apply to the freezer, except condensate isn’t really an issue. The main difference is the evaporator type. Manual defrost uprights have evaporator coils built into the non-movable wire shelves, so they remove heat pretty effectively, but do need defrosted periodically. Again, a simple static condenser should suffice, features that should be pretty easy to find. A chest freezer is fine too, and comparing apples to oranges, will probably outperform the uprights (not always), however they are inconvenient to use, and the typical condenser construction makes the next installment of the series slightly more difficult. This is becoming increasingly common in upright refrigerators and freezers too. The outer metal skin is bonded (foil tape) to the condenser coil, and the heat is spread across it. It is less affected by dirt, lint, and hair, but the tubing is inaccessible if needed, and adding insulation is impossible.
This is far from a complete guide to selecting a refrigerator/freezer for a homestead, but it forms a baseline for the modification of the typical “cheap energy” unit into something that needs less refrigeration capacity with the systems that follow. Up next: Insulating Refrigerators and Freezers.