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Build a warming/cooling box for maintaining temperature range year-round Answered

Hi all,

I need to build a box about 75cm wide, 50cm tall, 50 cm deep, that will maintain a temperature range of 20-30 degrees C (about 68-86 F) in ambient temperatures of 0-35 C (32-95 F).  What are my best options for heating and cooling?

For temperature regulation I imagine I'll be using an aquarium thermostat for the heating end of things.  What would be best for cooling?

I am imagining a plywood frame with a plastic tray insert, covered with styrofoam sheets. Pretty simple stuff. It will probably hinge open on the front face.  I'll be keeping fermenting and sprouting foods in it.

thanks for any help and ideas!


Use a Peltier fridge/warmer. All you need, except they don't have thermostats, you'll have to provide that. Superinsulate the box, and you should be good to go.

Steve, thanks much. I will definitely look into one of these but I don't think it'll be very readily available in Japan. The reversible of these nature is really intriguing.

I would think they'll be very easy to pick up in Japan actually.

I was only able to find small ones via internet searches. Perhaps finding some contacts in specific industries would be a good route, but I don:t think I could come up with anything by the time the weather turns cold...

What do you mean by "small ones" here ? You should only need a 50 W cell to get the sort of control you're talking about, if you can superinsulate your box ?


Hm, OK, 64 watts for 6100 yen. Time to look into this more closely. Thanks for the info!

Ouch, I was worried it was going to be one of the expensive ones ... will keep it in mind, thanks!

Go the all natural rout and bury your insulated box underground. If you put your box about 3 or 4 feet under ground the earth's temp should keep things in the range you want it.

If you do use a Peltier, be aware that you should use a good heat sink with them. I seen them burn out even with heat sinks after they become blanketed with dust, so keeping them clean is a must. Also you may need to look to the ratio the pelter chips will cool and the volume. if the outside temp is very high then the cooling ratio may mean the inside temp may be unacceptable.

Another approach (means a lot more work) would be pump a fluid underground to cool and return to a heat exchanger in the tank. You may have to bury several hundred feet of pipe in the ground to get the result you want.

Also another way to cool something is to use the sun. You can do this by using a evaporative-cooling system. It works by placing something you want chilled inside a inner metal cylinder and then close it up. That cylinder goes inside another cylinder made of something porous. Then you put something like sand in between the cylinders. You then pour fresh water into the area between the cylinders, saturating the sand. Then you place it in the sun.  As the outer cylinder heats up the outer cylinder, the water evaporates. The sand is touching the inner cylinder, and heat is pulled away from the inner cylinder as the water evaporates.

There is other ways to use the sun which is more complex.  There are ways to build absorption refrigerator which requires a heat source to cool. Like a camper refrigerator which uses a flame (or heating element when using electricity) to cool. But instead of using a flame you could use the sun. One word of caution, ammonia is used in some of these type of systems and can be deadly if inhaled. I recommend lots of research before tackling such a project.  You can start with Wikipedia's article on absorption refrigerator on absorption refrigerator

Wow, ongytenes, great info. Most of those are much more involved than I need right now, but very interesting for the future. The kitchen I'm using does have a sunken storage area directly above bare ground, but I think it's all rock. Still, very interested in using geothermal when available.

I think what I'll end up doing is using either a bare lightbulb, a japanese kotatsu heater unit, or a hair dryer, and a mini refrigerator core, attached to a $20 temperature controller. Should be the easiest way to go for the time being.

My first thought would be "bring it indoors!" Otherwise;

How long do you need to maintain the temperature for, and what sort of volume do you need to have inside the box?

What power supply do you have available?

Hi Kiteman! That ambient temperature is actually the ambient temperature indoors. I'll have three tanks with up to 12 liters in each. Power is 100V.