For off-grid renewable electricity, solar seems to make sense. Just throw some PV panels on the roof and you’re all set to stick it to the man, right? But the dirty little secret of the king of clean energy is that very few places on the planet get the sort of sunshine needed to make residential PV panels worth their installation cost in the short term, and the long-term value proposition isn’t very good either.
The drearier places on the planet might benefit from this high-power thermoelectric generator (TEG) developed and tested by [TegwynTwmffat] for use on a wood burning stove. The TEG modules [Tegwyn] used are commercially available and rated at 14.4 volts and 20 watts each. He wisely started his experiments with a single module; the video below shows the development of that prototype. The bulk of the work with TEGs is keeping the cold side of the module at a low enough temperature for decent performance, since the modules work better the higher the difference in temperature is across the module. A finned heatsink and a fan wouldn’t cut it for this application, so a water-cooled block was built to pump away the heat. A successful test led to scaling the generator up to 10 modules with a very impressive heatsink, which produced about 120 watts. Pretty good, but we wonder if some easy gains in performance would have come from using heat sink compound on the module surfaces.
Using thermal differences to generate electricity is nothing new, but a twist on the technique is getting attention lately as a potential clean energy source. And who knows? Maybe [TegwynTwmffat]’s or one of the other Hackaday Prize 2018 entries will break new ground and change the world. What’s your big idea?
Continue reading “Thermoelectric Generator Shines Where the Sun Doesn’t”
We will all be used to the thermoelectric effect in our electronic devices. The property of a junction of dissimilar conductors to either generate electricity from a difference in temperature (the Seebeck effect), or heating or cooling the junction (the Peltier effect). Every time we use a thermocouple or one of those mini beer fridges, we’re taking advantage of it.
Practical commercial thermoelectric arrays take the form of a grid of semiconductor junctions wired in series, with a cold side and a hot side. For a Peltier array the cold side drops in temperature and the hot side rises in response to applied electric current, while for a Seebeck array a current is generated in response to temperature difference between the two sides. They have several disadvantages though; they are not cheap, they are of a limited size, they can only be attached to flat surfaces, and they are only as good as their thermal bond can be made.
Researchers in Korea have produced an interesting development in this field that may offer significant improvements over the modules, they have published a paper describing a thermoelectric compound which can be painted on to a surface. The paint contains particles of bismuth telluride (Bi2Te3), and an energy density of up to 4mW per square centimetre is claimed.
Continue reading “Thermoelectric Paint Opens Prospect Of Easier Energy Harvesting”
We’ve covered many thermoelectric beverage coolers in the past, but none come close to the insane power of the AbsolutZero. [Ilan Moyer] set out to design a beverage cooler that chills a drink from room temperature to 5 degrees Celsius as quickly as possible, and it looks like he succeeded. The AbsolutZero consumes around 2.5kW of power and runs 8 water-cooled thermoelectric modules to quickly chill a drink.
[Ilan] put his machinist skills to work and fabricated many custom parts for this build. He machined water blocks for each thermoelectric cooler out of solid copper which draw heat away from each thermoelectric cooler. He also fabricated his own bus bars to handle the 200A+ of current the system draws. To transfer heat from the beverage to the thermoelectric modules, he turned and milled a heat spreader that perfectly fits a can of any beverage.
[Ilan]’s design uses a closed-loop water cooling system and 4 radiators to dissipate all of the heat the system produces, which is quite a lot: thermoelectric modules are typically only 10-15% efficient. The whole design is buttoned up in a custom polycarbonate enclosure with a carrying handle so you can conveniently lug the massive setup wherever quickly chilled beverages are needed. Be sure to check out [Ilan]’s build photos to see his excellent machining work.
Thanks for the tip, [Stefan].
Like many of us, [C] enjoys an ice-cold, refreshing soda while coding. Driven by a strong desire to keep a soda ice-cold indefinitely without using ice, [C] started Project Frosty Mug.
[C]’s stated goal is to keep a 20oz plastic bottle of soda at ~35F indefinitely while it sits in a room temperature environment. He started with a thermoelectric unit to cool an aluminium disc, like a cold coaster. Builds one and two made him realize that dealing with the generated heat was a big issue: it got so hot that it deformed the PLA frame. [C] also realized that bottom-only cooling wasn’t going to get the job done.
This project is now in its third build, which is pictured above. As you can see, it’s more koozie than coaster. That 3-D printed holster is lined with aluminium sheeting. Another flat piece covers the opening and attaches to the cooling element. A beefy CPU heat sink does its best, and a couple of U-brackets hold it all together.
[C]’s tested it with a glass bottle of Diet Sun Drop chilled to 38F. After 30 minutes in an ambient temperature of ~70F, the soda measured 45F. [C] lamented having not used a control bottle for comparison and reports that the power supply became quite warm. [C] isn’t going to give up that easily. Do you have any ideas for the fourth build?
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This is a great example of using a thermoelectric generator for a project. [Joohansson] made both a functional, and aesthetically beautiful fan using components from a computer.
Thermoelectric generators (TEGs for high temperatures, and cheaper TECs for lower temperatures) are also called peltier elements, which look like small square pieces of ceramic with two wires sticking out of them. If you supply power to it, one side will become hot, and the other cold. The TECs [Joohansson] is using want a temperature difference of 68C between either sides. They are typically used for cooling electronics and even some of those cheap mini-fridges will make use of one with a giant heat sink on the hot side.
In addition, they can be used as an electric generator, thanks to the seebeck effect. If you can create a temperature differential between the two sides, you can generate electricity. Using a CPU heatsink, cooler, and fan, [Joohansson] was able to power a small DC fan using only a candle. It’s a brilliant demonstration of the seebeck effect.
Continue reading “Candle Powered Fan Keeps You Cool Using a Thermoelectric Generator”
[Steven] manages to power an LED for 15 minutes using hot and cold water as a battery. He does this using the thermoelectric effect also known as the Seebeck effect, Peltier effect or Thomson effect. This isn’t particularly new; in fact there are commercial products that you can use to charge a cell phone using a small campfire or internal burner that works on the same principle.
What is interesting about [Steven’s] device is that he uses a salvaged Peltier device not meant for generating electricity, coupled with a home built joule thief circuit. In the video he describes how the joule thief functions and powers the LED using the small voltage generated by the Peltier device. The energy for the thermoelectric effect is conducted from a hot water bath through aluminum plates, through the positive and negative sides of the Peltier device, through more aluminum plates and finally into a cold water bath. As the heat energy transfers through the Peltier device a small electric current is generated and flows in two small wires coming out the side of the device. The energy generated by the Peltier device is stored in the joule thief and periodically dumped at a voltage high enough to forward bias the LED “on” for a brief moment. Technically the LED is flashing but at a frequency too high for our eyes to see. As the hot water bath cools, the LED goes from very bright, to dim, to off in about 15 minutes.
Not a very practical power supply but still quite the parlor trick. He wraps up the tutorial specifying that a TEG thermoelectric generator would be a much better choice for generating power and can handle much higher temperatures. You can watch the video after the break.
Continue reading “Peltier Joule Thief Power Supply”
Here’s a thermoelectric generator which [x2Jiggy] built. The concept uses heat from a flame, biased against cooler temperatures produced by that huge heat sink making up the top portion of the build to produce electricity via the Peltier effect.
The build is passively cooled, using a sync assembly that takes advantage of heat pipes to help increase the heat dissipation. A nearly flat heat sink makes up the mounting surface for the hot side, which faces down toward a flame driving the generator. [x2Jiggy] started the project by using a can, wick, and olive oil as the heat source. He managed to get about 2V out of the system with this method. What you see here is the second version. It swaps out the olive oil lamp for an alcohol stove. The cans with holes punched in them act as a wind screen while also providing a stable base. This rendition produces about 3V, but it doesn’t sound like there are any precise measurements of what it can do under load.