MBA/Engineering Off-Grid Refrigerator Project

[m3s]

We are a team of Northern Arizona University MBA students, working with a group of engineers, on the product development of an environmentally-friendly refrigerator designed specifically for the off-grid residents. The goal of this project is to offer a product that will last in the harsh conditions of a region, with minimum maintenance, and be unaffected by the power fluctuations typical of off-grid systems.

You could help us identify the needs of off-grid homeowners by using the link below to complete a short online survey.   Your response will be anonymous.

Survey link:
https://docs.google.com/forms/d/1L9F_7l4EamIfAmeF_o4QZi_30lqcQWX2acIYuT9Wx-4/viewform

Thank you for your help.

[retired profile of WrethaOffGrid]

Hi, I just filled out your questionnaire, I live off grid and use a chest freezer conversion, I use an external thermostat, you set the temp you wish on that, plug the freezer into the box, then plug that up to power, when it hits the temp you set it cuts off the power to the freezer.

It works well for several reasons, being a freezer, it is much more insulated, and being a chest freezer, it opens from the top, the cold air stays inside the box. Regular refrigerators have doors that open on the side of the box, when you open the door, all the cold air falls out to the floor, now the motor has to work harder to chill the air inside the box again, this uses up precious energy.

You might want to consider a design that opens from the top. Another option you can try is something my hubby did when we were living in town and had a regular refrigerator, we had teenage boys who would open the refrigerator doors and just stare into the box, so hubby installed clear plexiglass interior doors that opened separately from the main doors, that way we could open the refrigerator and look inside (through the clear plexiglass) without losing all the cold air, once we discovered what we wanted, we would open the interior clear doors and grab the food. You could even make sectional interior doors that could be operated individually so that you could only open the section you wanted and not lose the cold air from the rest of the box.

I understand that with marine applications, they would make cooler drawers, you opened the drawer and the cold air stayed inside the drawer/box… you should consider the mechanics of cold air, it sinks, so anything you can do to keep that cold air from escaping, from falling out onto the floor, means less power consumption.

 

Wretha

[beast]

why doesnt anyone try a fridge that uses water from the well to keep it cool
just like an old springhouse?

[retired profile of WrethaOffGrid]

That would work fine for those who have a well and cool water…. we don’t have one, we haul our water so it’s in limited quantities for us…  I would LOVE to do something like that, but where we live that would be near impossible….. our freezer-fridge conversion works great for us though.

[beast]

what about an icehouse?

[retired profile of WrethaOffGrid]

Anyone ever tell you how cute you are beast? :)

[retired profile of WrethaOffGrid]

How have you been lately beast? It’s good to see you here.

[Marc_uk]

I’ve lived without a fridge for the last 9 years. For most of the time I find it no problem at all. I have an insulated cool box outside, in the shade of a north wall. Only for a short period (maybe 2-3 months) do I have any trouble, and that’s only really with fresh milk. It will only keep 24 hours or so when the weather is really warm. When I get more solar panels I may try a fridge but would only use it in the summer months.

[littlebang]

I am actually very interested in your project, as actually as of recently I have been doing my own research, and a few small experiments on solar fridges. So far I’ve decided if you could make a solar adsorption cooler, i think this would work really well. Have the sun heat up desicants such as silica, or zeolite so that you can induce evaporation. You could have the humid air that was evaporated go underground for condensation, where it can be stored and used for other purposes(if using water as your coolant) or it can be recirculated through the system.

Or you could have the humid air go to  a seperate “tank” which is basically just an empty tank. You pump all the humid air into this empty , and as the sun sets and the ambient temperature drops, the water will condense. One way to think of that is take a regular old zeer pot for example. Now zeer pots work great, granted you live in a dry environment. If its humid, it won’t work as well. My idea would basically be take a zeer pot, and rather than set in “open air”, essentially put it in a larger sealed encassing, putting into a large sealed box. of course you want to make this tank as dry as possible beforehand. Now my idea is that the water in the sand will evaporate, making the air in the tank around the zeer pot humid. After so long the air in the tank around the zeer pot will become humid and it wont work so well, but hopefully that should be about the time the sun is setting. Once the sun sets, the ambient temperature will drop and the humid air should begin to condense. If this were to work, you could have zeer pots in humid environments.

Or, of course do the solar adsorption way, have one set of desicants being by the sun, while the other set is used to dry the air inside the fridge evaporator. I have more detailed ideas for how to do this, but i haven’t tested it and honestly I may have no useful ideas for.

I do not have any background in this, no formal schooling just interested in it so it would be great if you could tell me what are the flaws, drawbacks, inefficiencies of a system like this, as i haven’t been able to do much experimentation myself. But i would love to share more ideas if I actually say anything of use.

[littlebang]

I wrote a pretty long response to this post about the fridge, but for some reason it didn’t show up. But anyway, to summarize it i also am very interested in making an off the grid fridge, and have done some of my own research into it a little. I think the way to go would be a solar adsorption chiller. Just my opinion. Let us know how it goes, i’m really interested.

[retired profile of WrethaOffGrid]

Ohhh, sorry littlebang, for some reason the software cop here decided it was suspicious and put it in pending…. if that happens again, just shoot me a message and I’ll look at it…

wretha(at)gmail(dot)com

Wretha

[beast]

ok, the water cooled fridge, if youre using a cistern and rain water it wouldnt take much to run a coil of copper tubing below ground a ways and cool the water to subsoil temp so it cools your fridge
or you could just use a closed system filled with water and runs with a pump

no one ever tells me im cute….lol

and i am doing great ty

[Author]

Posts