Introduction: How to Make a Dehumidifier (Thermoelectric Cooling)

If you live in a humid area, or want to decrease the level moisture inside your house to prevent the growth of mold. This is the perfect Instructable for you, because I'm going to show you have to build a very easy to build dehumidifier from inexpensive parts you can find on Ebay. It will quickly remove moisture from the air by a phenomenon called condensation.

Basically we will build a device that extracts water from the air, maybe it also has a secondary use? Comment below!

Step 1: Materials

Picture of Materials

One of the main components is the peltier chip, also called a thermoelectric cooler. This is a 40x40mm chip that does something amazing! When powered from a 12V source (like a battery), one side will increase in temperature while the other side will decrease. The temperature difference is the required condition to make the water vapour in the air around us to transform into a liquid state, also called condensation.

You will also need an electric fan to pull the humid air through the device. The heat sinks will spread the heat and cold, making it more effective. Heat sink compound is necessary to achieve a good surface bond between the peltier and the heat sinks.

You can power the dehumidifier by either a 12V battery, or an adapter. In this Instructable I will be using a lithium polymer battery.

-Computer fan

-Large heat sink

-Small heat sink

-Peltier chip (thermoelectric cooler)

-Heat sink compound

-Scrap material, such as foam.

-12V battery

All these parts can be found on Ebay for under 30$! You will also need some tools:

-Hot glue
-Solder station
-Screwdriver + screws

Step 2: Assembly

Picture of Assembly

Fasten the 80mm electric computer fan to the larger heat sink. This is the heat sink that will be increasing in temperature by the peltier chip. The fan will be pulling the air into the larger heat sink. Flip the heat sink over and add the compound to where the peltier will be placed.

Place the peltier chip in no specific orientation or upside/downside. If reversed, meaning the larger heat sink decreases in temperature, swap the positive and negative wires.

Place the peltier chip and press down firmly. Add compound to the smaller heat sink and push it agains the peltier chip. Screw it down if necessary.

Step 3: Stand

Picture of Stand

Take some scrap pieces of foam, or even cardboard, and cut 4 rectangular legs for the dehumidifier to stand on. Cut one of the short ends at a 45 degree angle and hot glue it to the fan as shown in the pictures.

Since the heat sink on the bottom will collect water it might start dripping if the air is humid enough. Make sure you have high enough legs to place a container underneath.

Step 4: Wiring

Picture of Wiring

You will have a total of four wires, two from the peltier (black and red) and two from the electric fan (black and red). Solder the black wires to one of the pins on the electronic switch and solder another piece of wire to the middle pin from the switch.

Glue the switch to a convenient position on your dehumidifier, and solder the connector to the remaining two red wires and the black wire comming from the electronic switch.

I took the liberty to add LED lights, the main reason is because it makes it look better and lights it up during the dark hours. It also signals when the battery is connected to the dehumidifier, which can be very useful if you tend to forget things easily.

Step 5: Usage

Picture of Usage

Connect a fully charged battery, but remember to also purchase a small voltage alarm that will alarm you once the batteries is low.

After just 2 minutes drops of water is forming on the cold black heat sink indicating our dehumidifier is working properly. After 5 minutes the heat sink is covered with water extracted from the air. Proving that the device is very efficient and performs very well inside my garage where the humidity is low.

At just a 3 amps this setup will run for a little less than 1 hour. However, you can definitely get a much larger battery and achieve hours of run time on a single charge.

Don't buy does expensive dehumidifiers when you can build your own. Follow my instructions and you will have a device that runs efficiently, quietly and performs really well! Good luck, and comment below if you have any questions.

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Gerdnaxela (author)2017-12-20

I am trying to build a miniature version of this. To make it small enough to be easily portable. I have a peltier module that has a max amp of 6 and a max volt requirement of 2.1.

My question is how to select the correct battery. If I choose a battery that has an output that exceeds the amp or the volts what happens?

egagnon1 (author)2017-10-15

use 2 peltiers.

one to cool the other, and use a big heat sink to cool the last one.

nealalan (author)2016-09-27

My brain instantly started wondering, looking at this design, what would it take to convert this to an outdoor solar powered water collector? (Or for that matter, build it so that it will pull distilled water.)

1) Build into a large mouth funnel. Likely add a "collar" to the top of the funnel. Cut vent holes all the way around the funnel above the area where the cool-sync will drip.
2) Add an "air filter" cloth around the vent slots.
3) Add a 12v solar panel lead and a battery charging circuit.
4) Put the funnel in a clean milk jug. Glass milk jug will have more weight.


dglad4 (author)nealalan2017-08-02

This is a terribly inefficient method to obtain water. You shouldn't drink the water you collect as it is either as the heatsink fins are a great breeding ground for bacteria, even more so when dust builds up. You could filter it and boil the water if you really wanted, but this is consumption we're talking about let alone the inefficiency of using a peltier.
"While peltiers are useful, they're not very efficient. Only around 5% of the electrical energy used to power them gets used for cooling."
In addition, photovoltaic (solar) panels only make electrical energy out of ~22% of sunlight.
In conclusion, yes it would work but you're better off taking fabric soaked in sea water, dirty water or even leaves from tree branches and having them sit in the sun inside a mini glass house. The suns direct thermal energy (~55% of sunlight) will evaporate the water and it will condense on the glass/plastic.

jsprenkle (author)nealalan2016-10-13

The self filling water bottle is on indiegogo

nealalan (author)jsprenkle2016-10-14

Awesome!!! Glad to see someone is working on it! Exactly what I envisioned - particularly the bike model. While this wouldn't work in the desert, it could be amazing somewhere humid!

kuma.rhyu (author)nealalan2016-09-27

Unless your airborne humidity is very high (ie, high dew point temperatures), the likely hood of a peltier module getting it's cold junction plate below the dew point of free air and making water is low and production would likely be very limited. A mechanical refrigeration system would be more likely to be effective on a cost per gallon basis IMHO.


jimvandamme (author)nealalan2016-09-27

There are commercially available peltier cooler dehumidifiers. You could dry your cellar and get distilled water. However, the efficiency ratings tend to be vague.

They should last a long time if made well, and the parts should be easily repaired (power supply, fan, cooler module) compared to a refrigerant based machine. Then again, I have a 30 year old dehumidifier that still runs like new.

Stevie0424 (author)2017-03-20

How did you connect the Lipo Battery to the Computer Fan and the Peltier Chip wires?

Stevie0424 (author)2017-03-14

Does a large or small heat sink matter?

toddbatzler (author)2016-09-28

Nice idea but have a look at the efficiency of the thermo-electric
device. You'll find that the number of 'input watts' is much higher
than the number of 'output watts' of cooling. Another way to look at
this is the 'hot side' has to dissipate both the 'input watts' from the
12V supply and the 'cooling watts' pulled out of the 'load' (air/water
vapor) so will get much hotter than the cold side gets cold. Coolers use these because they 'have to' to make a mobile
device. Its far more efficient to use a refrigeration cycle if you
don't need portability. If this wasn't the case, a lot of refrigerators
would use the same technology.

starphire (author)toddbatzler2016-09-28

@toddbatzler, reading through all of the comments it seems yours is the most honest and reasonable comment regarding the actual efficiency of this device. Many people seem to have no idea just how much energy is needed to dehumidify basements, etc. in humid climates. Peltier devices have been available for several decades, but never replaced traditional cooling systems for good reason! They are ONLY a better choice than mechanical refrigeration pumps when portability, small size, or quietness are absolutely required features and efficiency (and cost, in utility bills) can be sacrificed in exchange for these special cases. It is laughable to call any Peltier-based cooling or dehumidification device "efficient", unless perhaps comparing it to some even worse method - like repeatedly baking out dessicant so that it can be used to "efficiently" remove humidity from a dank closet.

SteveD8 (author)starphire2016-09-30

I wouldn't say it is "laughable" to say it is efficient... if you have an unused 12V solar panel laying around, use that instead of, or in conjuntion with a battery. Use the sun to do the work. THAT'S efficient.

starphire (author)SteveD82016-09-30

OK, if you need only a small number of Watts of cooling power to effectively dehumidify a space and you can get your power free from the sun. So perhaps to control the humidity in a drawer, or small cabinet. Anything more than that, it still doesn't make sense.

Many commenters here seem to think that could be enough to dehumidify a room, or even a whole basement. An average "room" dehumidifer uses about 500W, and the adjacent air and soil provides essentially unlimited fresh humidity into a space that's being actively dehumidified, so a duty cycle of 100% is not unusual. In the Northeastern US, it can easily cost hundreds of dollars worth of electricity to run a dehumidifer half of the year:

A Peltier cooler is 1/3 as efficient, roughly speaking (yes, it really is TERRIBLE efficiency in comparison to mechanical refrigeration). So a comparable Peltier-based dehumidifer would need about 1500 Watts to do the same work.

So if someone needs enough cooling power to justify even a very small commercial dehumidifier, and they would like to make the most efficient use of their spare solar panels it would be better by far to convert the DC output of the solar panels to AC using an inexpensive inverter, and use that to power their mechanical dehumidifer. A single Peltier device being used to draw moisture from the air is a nice demonstrator of the concept, but it is basically a toy for most of the applications where dehumidification is needed.

SteveD8 (author)starphire2016-09-30

True. It is inefficient compared to a refrigeration unit. And obviously solar would be better being used to power a conventional dehumidifier.
However, since i began using Peltiers around a quarter century ago, their prices are now maybe 2% what they used to cost. "laughable" was what i took exception to.
Who knows... tomorrow all refrigerant gases may be banned as environmentally unacceptable. And Peltier devices could be mass produced to fill the gap, making them cost efficient.

whit3rd (author)starphire2016-09-29

There are good possibilities for dehumidification in a basement, though. One could run a cooling-water loop to the outside, and during the coolest part of the morning, turn the thermoelectric condenser on for an hour or three. This way, most basement moisture condensation happens over your drain, rather than on the concrete walls...

starphire (author)whit3rd2016-09-29

Despite a lot of hopeful comments here (maybe based on the false impression that Peltier devices offer high efficiency for cooling), any basement-scale dehumidification really would make more sense using a traditional compressor-based refrigeration system if it is to be affordable to operate, or for it to have sufficient capacity (as noted by JerryS42) without spending massive amounts of money on Peltier devices (and generating 3x the amount of waste heat in the process).

How the cooling loops are arranged to collect condensation, or how waste heat is removed from the cooler, is more adaptable to personal choice and experimentation though.

JerryS42 (author)whit3rd2016-09-29

Great idea but a basement can hold hundreds of gallons of water in walls and slab alone. You would need quite a few Peltier coolers and even though there are cheep ones online, the good ones are expensive.

zack832 (author)2016-09-27

While I think this project would be great for keeping the contents of small containers dry, I do not think it's feasible to scale it up for use in a large area. During the summer my dehumidifier can pull up to 4 gallons of water out of my basement daily. This is at a cost of about $40/mo. I'd need a whole wall full of these units to accomplish something similar. Odds are the energy cost would exceed what I'm now paying.

I'm always looking for alternatives in the hope of cutting my costs by at least 1/2, Have yet to find anything that will do that.

SteveD8 (author)zack8322016-09-30

Use a solar panel / battery / inverter. Panel charges battery. Inverter changes battery dc to your regions ac supply. Some initial outlay, but then free for life of solar panel or your dehumidifier. I live in tropical north Australia... it works fine.

IngenuityAtWork (author)zack8322016-09-27

Your comment gave me an interesting thought about the efficiency. If there was a means employed to to take advantage of the "waste" heat, for instance to heat water, then it would become much more useful from an efficiency perspective. I wonder if they make larger Peltier modules, and if scaling up the module would require an increased voltage vs. current. Maybe it would be practical to have a solar-powered unit that collects and heats water for human use for hygiene and cooking. Even if paired with a standard water heater, if the temperature of the incoming supply was increased, it would save on energy that the water heater has to expend.

TechPaul (author)IngenuityAtWork2016-09-27

Water cooling should improve the efficiency of the device by 10, unfortunately the water would have be running though constantly. There is also the problem of plumbing.

treekids (author)TechPaul2016-09-28

"Water cooling should improve the efficiency of the device by 10,
unfortunately the water would have be running though constantly. There
is also the problem of plumbing". Interesting. I'm tempted to attach a peltier junction to the cold water inlet to my water heater. There's a lot of thermal mass in a copper pipe full of water! And any heat generated will mean the water heater doesn't have to work as hard when it activates. This would be particularly effective for people with a timer recirculation system like the inlaws do in arizona.

zack832 (author)TechPaul2016-09-27

Perhaps the condensate could be used to cool...

BillbockD (author)zack8322016-09-27

Peltier unit are often found in Coldman electric Cooler so it indeed can be used to cool stuff :)

zack832 (author)BillbockD2016-09-27

Well, what I was referring to was using the water that collects to cool the unit - increasing efficiency. At some point there would be excess water that would need to be drained, but using the byproduct of the cooling, might simplify things - or not.

BillbockD (author)TechPaul2016-09-27

Not much of a problem, this system run on a peltier unit that is used in overclocked computer. so basically you could use an H50 water radiator from corsair and it would pretty much be bolt on. The drawback is that it consume more electricity. But water is not a good heat conductor compared to air, so you better off upgrading the heatsink/fan on the hot side instead.

BigJRM (author)BillbockD2016-09-27

I beg to differ. Air is a thermal insulator and water is a thermal conductor. Example: enter a freezer locker at -20F and no blower wearing a snow mobile suit. Now try a pond at 32F with a snow mobile suit. You will last only minutes in water! If you stay in 90F water long enough, you will get cold.

miguipda1 (author)2016-09-27


do not you "collect" the condensation in a box otherwise it will back humidify the room. That seems it should be interesting to have your black heatsink isolated in a box that collect the water.

What do you think about it ?

och (author)miguipda12016-09-27

It cannot be "isolated", otherwise it would't collect moisture from the air. But yes, it would be a good idea to add a small water collector underneat.

treekids (author)och2016-09-28

'do you not "collect" the condensation in a box "'. I have a commercial model that uses the same principle as this. It has a reservoir drawer underneath, and the lid is shaped like a funnel with a small hole. So the drips collect, and then you can remove the reservoir drawer and dump it out. I dump mine on my plants, which love the chlorine-free condensation.

Ray Hebert (author)2016-09-28

This project could have potential use in reducing the humidity in a cabin type boat!

DrGurk (author)2016-09-27

I have heard examples of peltier elements loosing effect over time. Have you noticed anything like that? I guess it would depend on the cheapness of the elements that you buy...

kuma.rhyu (author)DrGurk2016-09-27

If the junction between the hot and cold halves of the peltier module delaminates, the unit will lose capacity and the alternate expansion of the hot plate and contraction of the cold plate places stresses on this junction. Less well made modules will show this failure effect more quickly. Peltier modules also do not like anything but pure DC power and as most AC to DC power suppliea age, their filter capacitors break down and leak more AC-like waveforms into the output, reducing the module capacity, effectiveness and lifespan. Hope this helps...


DrGurk (author)kuma.rhyu2016-09-28

Thanks, great input!

jaswant9 (author)2016-09-27

Very good project. I will definitely try it.

BigJRM (author)2016-09-27

Great project! I think the best part is that these instructables catch our minds and get us thinking. I love to read the comments which show how much they get us thinking and how much added knowledge they provide. To RCLIFEON: this is a great instructable, I enjoyed reading and undertanding it. To COMMENTORS: thank you for your thoughts in expanding the knowledge of this instructable.

RBlibit (author)2016-09-27

This is a GREAT little project, and many people have 3/4 of the stuff in their computer junk boxes! Getting that heat off of the one side of that module is CRITICAL. I burned up two of them when my fan kept stopping, but they were only a few dollars each. I read that you can get better efficiency out of them with better heat dissipation, and that makes sense. I am going to get CRAZY and I am going to use 5 of the BIG 80 watt modules and make a car A/C system. I have two solar panels (420 watts total) and I am going to bolt them to the roof of my 17 years old Honda SUV to supply power for five 80 watt Peltier modules that will hang down from the roof inside the cabin, each with aluminum fins and small, quiet fans, while on the roof under the solar panels will be large, long custom aluminum cooling fins 6 feet long inside a closed channel with a squirrel cage blower for all of the "hot" sides to dissipate heat. The panels will shade the car while they supply power to the modules to cool it off inside on hot, sunny, days here in Florida. It won't get cold, but it WILL cool it off by 10 or 12 degrees (I hope). Heck, just the shade from the solar panels will help on hot sunny days. I say again - GREAT project! You sparked my imagination for more uses for the Peltier modules..

Meena_Bassem made it! (author)2016-09-27

close enough :D

DianaP7 (author)2016-09-27


Exactly. When I saw the title I was so excited that I might finally get relief from the expense the dehumidifier in the basement. But, as you say, this is not it. :(

iamchrismoran (author)2016-09-27

What size room or space would you expect this to be sufficient in? Or is it just about how much air can be moved into the system?

Would a peltier chip of different amp ratings make a difference? I see then on amazon but with relatively wildly different amperage.

gwlinn123 (author)2016-09-26

Very nice, thanks! Just what I need for storing 3D printer filament reels which are notorious for absorbing moisture and not printing as well. I built a sealed cabinet for storing reels and have a humidity meter in it. Currently, I use an Eva-Dry desiccant pack which can be recharged by plugging it into a wall outlet.

I have already purchased a completely assembled Peltier cooler from Ebay. But, I hadn't fully thought about how to use it until your article:

1. Use my 3D printer to print plastic panels instead of the foam ones you used for long term durability.

2. As another suggested, use a DC power supply instead of a battery.

3. Either run continuously, put on a simple timer, or use a humidity sensor and an Arduino to monitor and control.

4. Add a drain tube from the cabinet to remove the condensate. Since I'm far away from a real drain, drain into a larger container and let the house AC evaporate.

I have also been "vacuum sealing" open reels, but, that is somewhat of a pain.

whittey (author)gwlinn1232016-09-27

"...drain into a larger container and let the house AC evaporate." an expensive way to "empty" a container; you are paying to evaporate it, then remove it from the conditioned air...

gwlinn123 (author)whittey2016-09-27

Thanks for your comment! My filament storage container is relatively small so I don't think I will have that much condensate. Secondly, I haven't done this yet so I don't know what will happen. Lastly, I have a pretty large home so evaporating maybe a small amount will not be that wasteful.

RCLifeOn (author)gwlinn1232016-09-26

Glad you liked my Instructable! Awesome suggestions, have a nice day!

ChristopherC2 (author)2016-09-27

Can this be used in a similar way as a dehydrator for food?

kuma.rhyu (author)ChristopherC22016-09-27

What kind of temperature do you want to maintain in the dehydrator and what entering air temperature do you expect? The modules I have worked with generally can generate about 20 deg F delta T on each plate with proper air flow, so the module's entering air would have to be 100 deg F to achieve 120 deg F in the chamber, assuming you have enough BTW capacity.

whydotheycometometodie (author)2016-09-27

Nice - I wonder how it performs liters/watt hour and how long it will last without repair/replacement. I'm envisioning many of these hooked up to a car battery charged by solar cells...

Too many variables to even estimate L/Hr...

scott5134 (author)2016-09-27

First Peltiers are not very cost effective, also the electronically remove heat not create cold, technically you cannot create cold

Also you only put a dot of T Greast in the center, it will smooth out, too much will actually lower the heat conduction

About This Instructable




Bio: My name is Simon Sörensen and I am the creator of RCLifeOn. I´m 19 years old and live in a town called Trollh ... More »
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