That Ultra-White Paint That Helps Cool Surfaces? Make Your Own!

July 22, 2023 by Donald Papp 53 Comments

It started with [KB9ENS] looking into paints or coatings for passive or radiative cooling, and in the process he decided to DIY his own. Not only is it perfectly accessible to a home experimenter, his initial results look like they have some promise, as well.

[KB9ENS] read about a type of ultra-white paint formulation that not only reflects heat, but is able to radiate it into space, cooling the painted surface to below ambient temperature. This is intriguing because while commercial paints can insulate and reflect heat, they cannot make a surface cooler than its surroundings.

Anecdotally speaking, this painted battery section of a solar recharger gets too hot to touch in full sunlight. But when painted over, it was merely warm.

What really got [KB9ENS] thinking was that at its core, the passively-cooling paint in the research is essentially a whole lot of different particle sizes of barium sulfate (BaSO₄) mixed into an acrylic binder. These two ingredients are remarkably accessible. A half-pound of BaSO₄ from a pottery supply shop was only a few dollars, and a plain acrylic base is easily obtained from almost any paint or art supplier.

[KB9ENS] decided to mix up a crude batch of BaSO₄ paint, apply it to some things, and see how well it compared to other paints and coatings. He wetted the BaSO₄ with some isopropyl alcohol to help it mix into the base, and made a few different concentrations. A 60% concentration by volume seemed to give the best overall results.

There’s no indication of whether any lower-than-ambient cooling is happening, but according to a non-contact thermometer even this homemade mixture does a better job of keeping sunlight from heating things up compared to similarly-applied commercial paints (although it fared only slightly better than titanium dioxide-based white paint in the initial test.)

[KB9ENS] also painted the battery section of a solar recharger with his homemade paint and noted that while under normal circumstances — that is to say, in full sunlight — that section becomes too hot to touch, with the paint coating it was merely warm.

Actual passive cooling can do more than just keep something less warm than it would be otherwise. We’ve seen it recently used to passively and continuously generate power thanks to its ability to create a constant temperature differential, day and night.

Physical Neural Network Can Be Trained Like A Digital One

July 20, 2023 by Donald Papp 11 Comments

Here’s an unusual concept: a computer-guided mechanical neural network (video, embedded below.) Why would one want a mechanical neural network? It’s essentially a tool to explore what it would take to make physical materials work in nonstandard ways. The main part is a lattice of interlinked mechanical components. When one applies a certain force in a certain direction on one end, it causes the lattice to deform in a non-intuitive way on the other end.

To make this happen, individual mechanical elements in the lattice need to have their compliance carefully tuned under the guidance of a computer system. The mechanisms shown can be adjusted on demand while force is applied and cameras monitor the results.

This feedback loop allows researchers to use the same techniques for training neural networks that are used in machine learning applications. Ultimately, a lattice can be configured in such a way that when side A is pressed like this, side B moves like that.

We’ve seen compliant structures that move in unexpected ways before, and they are always fascinating. One example is this 3D-printed door latch that translates a twisting motion into a linear one. Research into physical neural networks seems like it might open the door to more complex systems, or provide insights into metamaterial design.

You can watch the video below just under the page break, or if you prefer, skip the intro and jump straight into How It Works at [2:32].

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Crab Shells Massively Improve Zinc-Ion Batteries

July 18, 2023 by Lewin Day 32 Comments

In the fast-moving world of battery research, scientists are constantly on the lookout for innovative materials with the right properties to help improve energy storage. Meanwhile, batteries are in greater demand than ever as production of EVs and renewable energy projects ramp up to new heights.

In the hunt for new and better battery materials, scientists found an unexpected hero: crab shells.Researchers at the University of Maryland have uncovered a remarkable breakthrough by exploring their use in battery production.

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Improving Ocean Power With Static Electricity

July 16, 2023 by Al Williams 19 Comments

Water is heavy, so if you think about it, a moving ocean wave has quite a bit of energy. Scientists have a new way to use triboelectric generators to harvest that power for oceangoing systems. (PDF) Triboelectric nanogenerators (TENGs) are nothing new, but this new approach allows for operation where the waves have lower amplitude and frequency, making traditional systems useless.

The new approach uses a rotor and a stator, along with some aluminum, magnets, and — no kidding — rabbit fur. The stator is 3D printed in resin. The idea is to mechanically accumulate and amplify small low-frequency waves into high-frequency motion suitable for triboelectric generation.

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Gravity Wave Detector Is Galactic Sized

July 15, 2023 by Al Williams 13 Comments

Detecting gravity waves isn’t easy. But what if you had a really big detector for a long time? That’s what researchers did when they crunched 15 years’ worth of data from the NANOGrav data set. The data was collected from over 170 radio astronomers measuring millisecond pulsars as a way to potentially detect low-frequency gravity waves.

Millisecond pulsars spin fast and make them ideal for the detection of low-frequency gravity waves, which are difficult to detect. The bulk of the paper is about the high-powered data analysis for a very large data set.

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Keeping Thermal Plants Cool Without Breaking The Cooling Water Budget

July 13, 2023 by Maya Posch 19 Comments

Steam generators in thermal (steam-cycle) power plants require a constant influx of cool water to maximize the transfer of thermal energy. How this water is cooled again in the condensor after much of the steam’s thermal energy has been spent in the steam turbines or heat exchangers is a very important consideration in the design and construction of these plants. The most obvious and straightforward system is direct “once-through” cooling, where the water is drawn straight from a nearby river or other body of water and released after passing through the condenser. This type of system is by far the cheapest, but is also impacted by both the seasons and environmental considerations.

Where cool surface water is less abundantly available, evaporative cooling in a recirculating system such as with spray ponds and cooling towers is a good alternative. Although slightly more costly, a big benefit of these is that they require far less water and have much more control over the intake water temperature, which can raise plant efficiency. Finally, dry cooling is essentially a closed-loop system, which is exceedingly useful in areas where water is scarce. This latter type of cooling is what allows thermal plants to operate even in desert regions.

As the global climate changes – with more extreme weather events – picking the right cooling solution is more important than ever, and has us looking at retrofitting existing thermal plants with more efficient solutions. If you were ever curious how power plants keep the cool side cool, read on!

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Improved Hydrogen Fuel Cells Are Groovy

July 7, 2023 by Al Williams 13 Comments

According to [Charles Q. Choi], a new study indicates that grooves in the hydrogen fuel cells used to power vehicles can improve their performance by up to 50%. Fuel cells are like batteries because they use chemical reactions to create electricity. Where they are different is that a battery reacts a certain amount of material, and then it is done unless you recharge it somehow. A fuel cell will use as much fuel as you give it. That allows it to continue creating electricity until the fuel runs out.

Common hydrogen fuel cells use a proton exchange membrane — a polymer membrane that conducts protons to separate the fuel and the oxidizer. You can think of it as an electrolyte. Common fuel cells use an electrode design that hasn’t changed in decades. The new research has catalyst ridges separated by empty grooves. This enhances oxygen flow and proton transport.

Conventional electrodes use an ion-conducting polymer and a platinum catalyst. Adding more polymer improves proton transport but inhibits oxygen flow. The grooved design allows for dense polymer on the ridges but allows oxygen to flow in the grooves. In technical terms, the proton transport resistance goes down, and there is little change in the oxygen transport resistance.

The grooves are between one and two nanometers wide, so don’t pull out your CNC mill. The researchers admit they had the idea for this some time ago, but it has taken several years to figure out how to fabricate the special electrodes.