Off Grid Air Conditioning and Refrigeration

Off Topic
#1

I suppose it is a little whimpy to want air conditioning, but I’m just not that much of a frontiersman.

Here in the south, it is pretty miserable without it. I imagine the same is true in Australia, and elsewhere.

But air conditioning kicks energy demand to a whole new level.

I am wondering if any of you have tackled this challenge, and what kind of solutions you have come up with.

So far, I am thinking that if you have the luxury of new construction, then you can incorporate passive technologies to significantly help with this problem.

But beyond that, you will still need some sort of air conditioning (short of living in a cave).

From what I understand, air conditioning based on vapor compression of refrigerants is the most efficient way to transport heat, and those which have a ground source or water source heat exchanger are the most efficient of these.

This contrasts with absorption cycle air conditioners, such as ammonia-water systems, which are about 80% less efficient, but are more easily implemented, and have the additional advantage of merely needing a heat source rather than electricity to run a compressor.

Swamp coolers are great in arid areas, but won’t do in places like the Southern US, with our high humidity.

Based on these observations, I am thinking that a well insulated and well shaded house (possibly partially underground) with a high efficiency vapor-compression air conditioning system is the way to go.

I would also observe that an additional consideration for system resiliency is the ability to “do it yourself.” Most refrigerants are heavily regulated and may be difficult for the layman to obtain. I notice that Propane works as a good refrigerant, although it has the down-side of being flammable.

Any thoughts?

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#2

Maybe incorporate thermal mass in the form of double drywall, we’ll insulated slabs and water storage and store cold(yes yes not cold but lack of heat) just like we store heat here. Overcool when the sun is out using a conventional air conditioner running on solar and mostly coast at night. Just another form of energy storage

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#3

There was an experimental house built last yeat here in the city of Ljubljana being complitely independant for energy for heating/cooling. It has two giant tanks undergrownd, a hot and a cold one. During winter the warm water is pumped trugh the house heating sistemu where it cools and passes in a cold tank. During the summer it flows the other way, cooling it and provideing heat for the einter.
It is an interasing and inovative way to use exess energy but i dare not to think of a price for such a system. Just think of that giant tanks and the amount of insulation neaded!

I was thinking about diy air condition for a while now. There is like a milion videos of it on youtube on that topic on youtube and l havent found many usefull. Folks put plastic bottles in the fridge and then “cool” the house with itplaceing them in front of a fan. Looks like they havent put their hand on the back of an refridgerator yet…

For a low humidity enviroment l think evaporative cooling is the key. But conventional types have a downside makeing the air to humid, so in the end you feel eaven hotter. l was thinking of system similar to a nuclear plant. The evaporator shuld first cool the water in an outside unite, wich wuld then cool the air insyde. What do you guys think?

ps; i get the best air condition in our wine cellar. Cools you from both outside and insyde :wink: lf you spend enough time in it eaven the high outside temps stop botheryng you :grin:

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#4

I think the answer is to use a car engine to generate your power and use the auto ac compressor for your ac. the engine cooling system and exuaste can heat your water. Until you start stacking your functions you will never see any kind of systems efficiency. If you have a well and pump water for watering this can also be used as a chiller by running it through a condenser on its way to the garden. reuse the energy you are already using to do more.

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#5

To cool your house in the night: paint it black
To prevent heating in the day: shining aluminium

How to make it black in the night and shiny at daytime ?? :grin:

Using thick concrete slab at the bottom,
wetted concrete , mixed with lime, for the sun pointing walls ( evaporation from the water in those walls will cool down the entire house )
The lime in the concrete will attract the humidity in the air inside the house towards the wall and evaporate even more and better.

did some tests here in Thailand, concrete roof slab, 20 cm, outside heated the concrete up to 46 Celcius, inside 26 degrees… only a little water mist to wet the outside…

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#6

I think cooling Like other energy use. To be off grid you simply must reduce consumption.
Underground houses are very easy to heat and cool because of the constant moderate temperature of the ground below frost level. But if you are not building new, other means of conserving cool are needed.
Growing up, My dad insisted on opening the windows at night when it was cool, and then closing everything up tight in the morning to keep the heat out. The house usuallly stayed prettly comfortable. A small window ac was saved for the really hot days.
Now when my mother was growing up, they had a windmill to pump water and it of course pumped whenever the wind blew. The water ran into a tank for the livestock, but first went into a barrel buried in the ground, which then overflowed to the stock tank further down the hill. So the barrel was always fresh cold water. they then put their cans of cream in there to keep it cold.

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#7

In 1987, my wife and I made a trip to Eureka Springs, Arkansas, and I remember touring a house there that had an exterior wall made of stacked triangular shaped stones about an inch thick. One flat side of each stone triangle faced inside, leaving a point facing out. As they explained it to us, since heat dissipates from a point more efficiently than from a flat surface, the outside points acted to draw the heat from the inside. The inside of the house was noticeably cooler than the outdoor ambient, with no active air conditioning.

Of course, that was 30 years ago, so I’m fuzzy on the details. Has anybody else ever heard of this?

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#8

Alex, I do vaguely remember hearing something about that. Was it mentioned in the mother earth news? I guess I’ll do a little looking for it’

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#9

This is what I’m going to try. Our water sits in the ground at 41.5 degrees. The static pressure of the water in our well is at 8’, which makes it easily accessible from the well cap. Initially to test it out, I will just drain the outgoing water on the ground outside. Eventually it can be used to water the garden or something useful.
This heat exchanger runs at 12-24 volts and I have a small pump that also runs at 12 volts. I got it for free from a neighbor back when I had that J O B thing.
http://www.comairrotron.com/content/patriot-pq24b7-e2-039032?language=en

_20160630_215634.JPG2078×1889 586 KB

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#10

Great find for the money. Ground water is a never ending source, and 8’ is easy to pump. Windmill maybe?

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#11

Insulation and planned landscaping/shading will help a lot. I also found keeping the attic close to the outside ambient temperature helps quite a bit for cooling, so you might want to check venting options. If the attic is too hot, then the hot air pushes back into your living space compounding the issue. If you have a basement, then an attic vent fan will push hot air out of your attic and can pull cooler air up from your basement, but a lot of southern homes don’t have them.

Geothermal or ground source heat pumps work quite well. Typically you want a closed loop system. It saves groundwater but I think it is also more efficient since you need less pumping pressure and they use a slightly different temperature range for operation. If you can install your own horizontal loop in your yard, you can save a lot of money since that is a huge upfront cost for an initial system. I think it is like pvc or pex buried like 40 inches down with a ditchwitch type of machine which you can rent. Some municipalities are coupling geothermal with their municipal water supply now.

If you run a CHP gasifier, an absorption chller might be a good. It isn’t as efficient, but you have a use for the excess heat that way. Ammonia is actually a better refrigerant then the flourocarbon ones, but it is highly corrosive and a dangerous gas when it escapes.

Solar PV coupled with a compressor ac or even just to make ice to couple to your existing hvac system might be the easiest. There are a couple of products on the market, they are typically used for load shifting, ie buy cheap electric at night make ice, melt it during the high rates during the day for AC. but it is also applicable if you are generating excess power during the day and you don’t have net-metering available. It isn’t as efficient to make ice during the day because of the hotter temperatures for the heat exchanger. I have seen some homemade ones.

A lot of it depend on your locality, and what resources you have, how much time/money you are willing to put into the issue.

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#12

I know this feeling man. My state gets the worst of both worlds: extreme cold and hot.
During the summer its around 95+ with 90-100% humidity. Doesn’t help that i live near a river.
I will say, reflectix is a must. Literally the best thing since sliced bread for blocking that giant ball of burning gas thats trying to kill me. A white roof helps as well and good insulation. Also insulating the outside of the house underground. You want to trap the temperature of the ground to the house. My grandfathers work building is like this. Lots of insulation but the concrete slab is surrounded by 2 inch foam about 2 feet down which is the frost line. The ground itself heats and cool it. During the super hot summer months it might hit 76 inside. Upper 40s during the winter with no heat. Thats part of the reason i am looking at wood gas. I want to run a BIG air conditioner off a generator. I dont want to sacrifice if i dont have too. I just need to research more.

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#13

Where are you at Joshua? What do you do for a living? Do you have access to a lot of wood?

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#14

We managed a new standard this year we hit 34 Celsius above and had over 12 days above 30 c ;we have never seen that before. Even I considered getting an air conditioner. Ended up sleeping in the basement.

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#15

West virginia and yes i do somewhat. My neighbor has 40 acres of forest I am allowed to scour for wood. Can’t cut but plenty of downed trees and sticks to make charcoal out of. The cost of wood is cheap here. Pretty sure a cord of wood is under 100 bucks. I’ve seen it as low as 70. I work for walmart. :frowning: The economy is pretty bad here.

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#16

Wow. A cord( 4m3) of first class beachtree firewood is sold for about 250€ (300$?) here, oak for 200€. If someone wuld say he is willing to pay me 70$ for a cord of wood he wuld most likely have to see a doctor for being atacked by a “klin” (a peace of round wood 1 m long for measuring wood before being cut and split).

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#17

While perusing my vintage popular science collection I ran across this article on gas refridgerators. (July 1963 issue pg. 128) very succinct drawing helped me to understand it’s operation a little better.

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#18

Servel gas refrigerators are famous for two things: working very well and carbon monoxide poisoning. A house we bought had an old one. Man, that thing worked great. just a small, continuous flame and was a great extra fridge, even made good ice, electric cord only for the lamp inside!. We got a notice of the CO danger, actually a recall. They were offering a bounty on them. I finally dragged the thing out of the basement (heavy-built right.). Foolishly, I tried to demo it (outdoors). The ammonia just about killed me. It’s like the anhydrous ammonia the farmers use, strong and volatile. Don’t mess with it.
Actually, now I wish I had it back. It would have lasted another 50 years! Live and learn. :sweat_smile:

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#19

l always wanted to get my hands on one of them but they are rare here. l only seen one in my life in a wild dupm not far from us. To damaged to be revived.

I eaven considerd building one but like Mike sayd, ammonia isnt a toy…

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#20

:confused: that probably would have been great for a “partially outdoors” fridge/freezer; just build a drafty shed around it and problem solved. :stuck_out_tongue:

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