Bike-Powered Shredder Makes Short Work Of 3D Printer Waste

June 16, 2026 by Donald Papp 17 Comments

[Brogan M Pratt] and his students do a lot of 3D printing, and as such found themselves producing a lot of plastic waste. Seeing an opportunity, they built a bike-powered plastic shredder that turns a little human exercise into the power needed to transform waste plastic into small bits. Shredding plastic is a necessary first step for any sort of processing, so getting this part working reliably is as important as it is educational.

Shredding is a necessary first step to processing plastic waste.

Being in the Netherlands, using a bike makes perfect sense. But it turns out there’s a lot more to making a human-powered plastic shredder than simply bolting a sprocket to a shredder, looping the bike chain over it, then climbing on and working up a sweat.

In between the bike and the shredder is a large gear reduction, a fifteen kilogram flywheel, and a heavy-duty frame to anchor everything in the face of so much mass and torque. Add some covers and safety guards and the result is a stationary bike with a hopper for waste, a bin for output, and enough rotational torque and inertia to chew through stubborn bits without stalling.

Now that the shredder works, what’s the plan for all the little plastic shreds? The goal is to turn it back into usable filament which is obviously very useful, but we’ve also seen that compression molding plastic waste can work pretty well, too.

Being an educator, [Brogan] makes it clear that a bike-powered shredder, while pretty cool, is not the only missing link in sustainability. There is currently no easy way to recycle plastic at scale. But the shredder is a critical part of demonstrating the whole process in a hands-on way, and learning why recycling plastic at scale is a genuinely difficult job.

Continue reading “Bike-Powered Shredder Makes Short Work Of 3D Printer Waste” →

Desalinating Seawater With Solar And No Brine

June 7, 2026 by Maya Posch 40 Comments

Although desalination is very commonly used these days to convert seawater into fresh water, one of the major disadvantages of current approaches is that commercial desalination plants produce a lot of brine, which has to be dumped somewhere ideally without causing major environmental issues. A new solar-thermal method as demonstrated by [Luheng Tang] et al. was published in Light: Science and Applications, with accompanying PR article.

This method is claimed to require no pre-treatment or leave brine, using special panels that wick water across their surface and then use solar radiation to distill this water. This differs from previous similar methods through a special surface treatment that prevents build-up of salts which would require cleaning or replacement.

The salts and other contaminants that would normally end up in the brine slough off these cells and can then be further processed to recover everything from plain table salt to lithium as well as gold, uranium and other substances of interest that are prevalent in seawater.

So far these self-cleaning cells have been tested with water from a number of oceans with a claimed 74% solar-to-vapor conversion efficiency and nearly 100% salt extraction. As always the challenge will be in scaling this up to industrial levels, but so far it looks promising.

From Scrappy Pallet Wood To Fancy Tea Tray

June 2, 2026 by Maya Posch 16 Comments

Pallets are a wonderful way to package goods and move them around, but especially the wooden ones have a very finite lifespan. This means that many of them are discarded every day, even though there is still good wood on them. Even if it’s not the highest quality wood, you can still use it for some nice wooden items, like the tea tray that [GR Woodworking] recently put together.

The reclaimed wood is the typical fast-growing, soft type, with the suspicion of it being paulownia here. Of course, wooden pallets use a wide variety of wood varieties, so not all reclaimed wood is equally suitable for applications like this, and identifying the type can be a challenge in itself.

In the video it’s shown how the wood is planed to make it smooth and straight, before the joints are created and it is married to the poplar or aspen base plate. Of note is that absolutely no power tools or bulky things like router tables are used here, just basic hand tools that should make this kind of woodworking accessible to people even without that kitted-out woodworking shop.

After assembly it’s finished with Vararhana oil-based stain to give it a darker look and really bring out the grain. Naturally, since it’s a tea tray it has to be commissioned with a proper tea ceremony, which it passes with flying colors.

Continue reading “From Scrappy Pallet Wood To Fancy Tea Tray” →

On The Wisdom Of Replacing A NiMH Module In A Prius Battery Pack

June 1, 2026 by Maya Posch 81 Comments

Old versus new Prius NiMH module. (Credit: HubNut, YouTube)

It’s possible to get a pretty good deal on used Toyota Prius cars, but as with all hybrid cars that also means a used battery pack and resulting issues. In the case of the Gen 2 Prius that [HubNut] recently acquired it was clear that its battery was effectively toast, with the engine running constantly and the car often giving up due to detected issues with the pack. After getting to an EV-focused garage for repairs, a spare NiMH module was used to replace a problematic module to bring it back to good health, while raising the question of how sensible such a repair is.

Certainly, compared to the average BEV where a much larger battery is generally integrated well into the frame, a Prius makes things very easy, with the compact battery readily accessible and removable from the trunk. It is also a very modular battery, with some elbow grease and bolt-twisting enough to disassemble it.

Even with that it still a high-voltage battery with all the associated risks, and as raised in the comments there’s a big question about putting a new(er) cell into a pack with more worn-out NiMH cells as generally the cells wear out fairly evenly. While this fix can give the pack some more life, the new cell won’t match the internal resistance and other parameters of the pack, leading to issues like voltage drift. Then there’s the issue that if one cell failed, others probably aren’t far behind, so this hack would soon become a regular ritual.

Much like swapping one bad 18650 Li-ion cell in a bigger battery, it’s probably a more sustainable solution to simply replace the entire battery at once, or at least replace all modules or cells to properly refurbish it. For [HubNut] this fix suffices because he suspects that this pack was already assembled from random modules, it’s an important consideration to make if you don’t enjoy ending up stranded during a trip.

Continue reading “On The Wisdom Of Replacing A NiMH Module In A Prius Battery Pack” →

Power From Gravity

May 26, 2026 by Al Williams 65 Comments

Gravity batteries aren’t exactly a new idea. You can store energy by lifting something heavy, converting kinetic energy into potential energy. To get it back, you let the mass fall and convert that motion to electricity. [Valeriamayara22] shows how to build a working demonstration model of such a system.

This isn’t free energy. Something has to lift the weight. In this case, the height is 1.8 meters, and the mass is 15.65 kg. Even so, the model achieves 13 W peak output and 58% efficiency, according to the post. Reportedly, it takes 394 drops of the weight to fully charge an iPhone 16, so this isn’t a practical project, but it does show how a gravity battery works. One nice thing is that the system stores as much energy on its 1,000,000 th charge as it does on the first one, especially if you keep the chain lubricated. Try that with a chemical battery.

The mechanical part uses a bicycle chain and some sprockets. There is a battery to even things out since, like wind power, when you make energy with a mechanical battery, you either use it now or lose it.

The cost of the build is about $400, and there’s a GitHub repo with all the files if you want to take your own shot at it. The energy efficiency number references the potential energy stored versus the energy produced. Obviously, if you are using some other energy source to lift the weight, that’s another calculation.

As you might expect, a practical system like this can be very large.

Low Head Turbine Generates Plenty Of Power

May 22, 2026 by Bryan Cockfield 32 Comments

Engineering design makes all kinds of tradeoffs. Power trades off with torque, strength trades off with weight, and cost can trade off with quality. For designing a hydroelectric turbine, one of the main tradeoffs is hydraulic head with flow rate. Many large dams meant for bulk power generation will go with high head (or medium) designs, and for small dams with low head it’s usually not cost effective to build any generation. But if you’re really determined, you’ll want to build a low head water turbine like this one.

The build aims to use easy-to-find materials and simple tools. It uses 110mm and 160mm PVC pipe to not only siphon water up and over a dam, but to house the turbine as well. The turbine is built from a computer fan and sits inside the pipe with a shaft running through a Y-type fitting to the generator. The generator is built from a scavenged hoverboard wheel, and outputs a reported 3.3A DC at 60V for around 200 watts of power with only around 3m of head. The design allows the turbine to be placed at the point in the pipe that best suits the environment.

[OpenSourceLowTech], the creators of this project, make a compelling case that this build is cheaper than a 150W solar panel and it might even be able to produce more energy as well over certain timeframes, provided there’s a reliable source of water available and the owners of the dam don’t mind someone siphoning water over it continuously. The build video is worth a watch as well if for nothing else than the animation, which documents the build in excellent detail. Generating usable energy from hydropower doesn’t even need this big of a dam; if all you need is to charge your phone this tiny waterwheel will get the job done.

Thanks to [Keith] for the tip!

Continue reading “Low Head Turbine Generates Plenty Of Power” →

Improving An Aquarium Chiller With An Industrial Controller Transplant

May 22, 2026 by Maya Posch 7 Comments

A healthy aquarium ecosystem requires very specific conditions, with factors like the salinity and temperature having to be just right to keep said ecosystem happy. As some species are adapted to fairly cold water, this requires the use a water chiller. Recently [The Blunt Oracle] modified one of these aquarium-focused chillers with a much better controller to make it both more accurate and potentially more efficient as well.

The target for the surgery was a generic Shanhuchong Y-160 chiller that after a brief teardown turned out to use an STC-1000 style controller. The biggest disadvantage with this unit is probably that it just has one temperature probe, which monitored the temperature of the heat exchanger rather than that of the chilled water tank.

This controller was replaced with a Wi-Fi-equipped Elitech ECS-974T sourced for $50 off AliExpress that uses the same 71 x 29 mm form factor. Following that it was just a matter of some creative rewiring – as shown in the top image – and installing the twin temperature probes of the new controller.

Being able to monitor also the temperature of the chilled water adds a layer of redundancy that’s very welcome after splurging thousands of clams on a fancy aquarium and its inhabitants. As a bonus the Wi-Fi interface allows for it to be monitored and controlled remotely, with [The Blunt Oracle] pushing the Home Assistant configuration in a PR as well that recently got merged. They’d also like to extend their thanks to Elitech for having pretty good documentation that really helped with creating the HA configuration file, which is a rarity with many of such controllers.