[cmlek]

This originally came from an argument about saving on the electricity bill, but I want to be sure there's not some major point I'm overlooking.

I need to keep my rental house between 50-80 Fahrenheit, for my pet bunnies. The house is 3 bdrm, living room, tiny dining area, decently sized kitchen. I am aiming for a temperature between 76 and 78 Fahrenheit. I am arguing that it is cheaper to keep windows open, employ 3 box fans full-time for air circulation, and use strategic placement of milk jugs full of frozen water (since the fridge will be on regardless).

I am being counter-argued that central air or a window unit will be more efficient, as once the house is cooled down it will take less energy to maintain than will be eaten by the rest of the process mentioned above.

(I live in West Lafayette, Indiana. Average summer temperatures growing up went 80's-upper 90's and its lower mid-to-high on the humidity scale.)

I will be very grateful for your thoughts.

-MJH

[gnm]

Hmmmm, you could eat the bunnies, turn up the thermostat, and sit around in your shorts...


Sorry, refrigerated air is pretty inefficent but depending on the size of the room, perhaps a window type refrige unit? Some of the small ones aren't too bad. Unless you are expecting power outages that should work. Too bad you can't use a swamp cooler because I suspect our humidity is pretty high. Swampers are pretty efficent.

-G

[RonMN]

I got away with NO air conditioning by this method...I would have 1 fan pointing out the window and another window (on the other side of the house) open AT NIGHT ONLY. The cool night air got dragged thru the house & by morning the whole house was getting a little cold.

In the morning i would close it all up & the house would usually stay pretty cool all day even when it was 90+ degrees outside.

Once the darkness fell i'd open up the 2 or 3 windows again & turn the fan back on.

Saved me about $250 a month in electric costs!

[pip]

The milk jugs of frozen water aren't free like you seem to imply. Your fridge will need more energy to freeze the water. The question is whether a refrigerator is more efficent than an air conditioner, and I have no idea.

[pip]

Hold on a second, I'm wrong. Refrigerators do not produce cold. They move heat from inside the fridge and expel it through coils on the outside. There is a net gain of heat from the inefficiencies of the moving parts (energy flows into your house).

Freezing water and putting it around your house will increase the temperature due to the net flow of energy (electricity) into the system defined as your house. Freezing water in a refrigerator inside your house is counterproductive.

Think of it like this. If you have a perfectly insulated room and put a refrigerator inside and leave the door open, you will heat up the room. The fridge simply moves heat around, and it's all still inside the room. The friction heat created by the fridge's moving parts will cause a temperature rise.

[Pops]

Pip has it right, you are simply moving the heat of the water from the freezer compartment to the air in the kitchen – the refrigerator is ‘on’ as long as it takes to bring the contents to the desired temperature. The more warm things you put in the more it runs – the longer it runs the more energy is lost to mechanical inefficiency.

But if you take Ron’s “open at night close during day” and keep the bunnies in a north facing room with foil over the windows, add BARRELS of water to suck up the heat of the day and release it at night (depending on how much cooler night air is) you might be able to get away with no cooling at all except on the most hot and humid nights. To get the most efficiency from a window air conditioner run it as much as possible at night when the outside air is coolest.

Removing some of the water vapor from the air is the benefit of the conditioner – less heat holding capacity in dryer air plus it 'feels' cooler.

Just some ideas, YMMV…

[pip]

I like your question. (Sorry, I’m an engineer)

I calculate the heat absorbed by 1 gallon of water going from 30F to 76F to be 1,563 BTU. A small window air unit is 8,000 BTU/hr. So you’ll need to melt 5 or 6 gallons of water per hour to equal one small window unit air conditioner. (Assuming your fridge is not inside the house.)

Somebody feel free to check me. I used 6.00 kJ/mol for Hm of water.

[smiley]

One of the most efficient ways to cool your house is to spray the roof with water. It works extremely well with flat roofs, but it is a lot of work.

But anyway 32 degrees doesn't sound too bad. Your bunnies should be able to handle it, they are better equipped to deal with heat than we are.

[bruin]

If you freeze the water at night, presumably the heat generated by the fridge will easily escape the room at night with the windows open. Then during the day, the fridge is not used and the ice would then be placed out in the room.

Since you are running the refridgerator (freezing the water) at night, it will work less to freeze the water as well during the night. However, you must wait until the room cools some from the outside before returning the jugs to the freezer.

So a question is, what temperature is the room at night versus the day?

[ArimoDave]

There's one other problem with running box fans which circlulate air throughout the house. The box fans produce heat. The mere action of moving the air also heats the house.

If the house gets too hot later in the day after you have cooled it at night with a box fan pointing out one window while the others are open, the window air conditioner will work.

One method I am going to try this summer, if it gets too hot, is to make a series of coils in which I run water through. I will put the coils in one window and a box fan exhausting air out another. The time it gets too hot is usually early evening -- about the time I should start watering the lawn. So, the lawn gets watered, and the house gets cooled all at the same time.

The copper coiled heat exchanger is going to take some design. I don't want to use an automotive radiator -- especilally one that is used. New ones are too expensive.

ArimoDave