Most of us take it for granted that water is as close as your kitchen tap. But that’s not true everywhere. Two scientists at MIT have a new method for harvesting water from fog, especially fog released from cooling towers such as those found from power plants. It turns out, harvesting water from fog isn’t a new idea. You typically insert a mesh into the air and collect water droplets from the fog. The problem is with a typical diameter of 10 microns, the water droplets mostly miss the mesh, meaning they typically extract no more than 2% of the water content in the air.
The team found two reasons for the low efficiency. Water clogs the mesh openings which can be somewhat mitigated by using coated meshes that shed water quickly. Even in the lab that only increases the yield to about 10%. The bigger problem, though, is basically only some of the droplets hit the mesh, and even those that do may not stick because of drag. Fine meshes can help but are harder to make and have low structural integrity. Their solution? Inject ions into the fog to charge the water droplets and impart the opposite charge on the mesh.
Continue reading “Extracting Water from Fog”
[makendo] needed a portable fog machine for an upcoming project. It seemed like the kind of a thing a liberal application of money on the Internet could fix in no time. But quality fog machines are too expensive, and the cheap machines are just, well, cheap. Stuck between $800 and quickly broken crap, he decided instead to fashion his own.
Fortunately for him, a recent fad has made it so that a certain segment of the populace absolutely require dramatic clouds of scented drug fog or they get cranky. The market saw an opportunity, cost optimized, and now there are many portable fog machines just waiting to be born in the form of an e-cigarette. However, an e-cigarette needs interaction from a person’s lungs to provide an annoying cloud. So he modeled up a 3D printable case that would blow air into the intake of the e-cigarette. Instead of filling a person’s lungs with a cloud of eye drops and nicotine, it would let out a steady stream of fog.
This device does burn through emitters, because the e-cigarette was not designed for this kind of heavy duty. Even reading the Amazon comments for the $800 dollar version, this is fairly normal for these things. So now [makendo] is able to produce a nice cloud of smoke whenever he needs and it only set him back around $40 US dollars.
The greatest of Halloween costumes start with an idea, but they’ve also got to have strong execution to pull the whole thing off. This year [Johanna Jenkins] decided to put together a Fembot Halloween costume which is a wonderful example of this concept. Going as a Fembot from Austin Powers: International Man of Mystery sounds like a lot of fun right off the bat, but a bit of work at the sewing machine and access to a wig shop in Hollywood really brought it to the next level. But [Johanna] didn’t stop at that. The Fembots have machine guns in their bras. After they’ve torn through all of their ammo they’re left with smoking barrels as nipples, and that final touch even made it into the costume. In the video after the break you can see [Johanna] showing off the small battery operated fog system she piped into the costume bra.
Continue reading “Fembot costume includes smoking nipples”
Poor [Todd Harrison] spent all of Saturday and Sunday trying to make some ground-hugging fog for his Halloween decor. His fog machine hack turned out to be an utter failure. But he admits it and reports that he still had a lot of fun. Don’t feel bad [Todd], this happens to everyone from time to time. And anyone that has doubts about [Todd’s] skills need not look very far to find out that he does know what he’s doing.
The project started off with a theater-style fog machine. The problem is that this fills a room with a thin foggy-haze that doesn’t take shape outdoors. He wanted that ankle-deep graveyard effect and had seen several examples online that use a fog-machine with a bucked of dry ice. He though he’d just use his own bucket full of regular ice and salt water. Inside the bucket seen above there is a 15′ coil of copper tubing through which the fog machine’s output is passed. On the other side of the bucket there’s a plastic tube that goes to a sheet of plastic meant to distribute the cooled fog.
The problem here is that the fog machine puts out a hot mist. When it hits the ice bath the mist condenses into liquid form and that’s the end of the fog. As he attests in the video after the break, the dry-ice fog hack isn’t pumping out fog. It’s just using the heated steam to pump out carbon-dioxide vapor boiling off of the dry ice.
Continue reading “How NOT to make ground-hugging fog”
This wire-frame cube appears to be floating in mid-air because it actually is. This is a project which [Tom] calls a Laminar Flow Fog Screen. He built a device that puts out a faint amount of fog, which the intense light from a projector is able to illuminate. The real trick here is to get a uniformed fog wall, which is where the laminar part comes in. Laminar Flow is a phenomenon where fluids flow in a perfectly parallel stream, not allowing errant portions to introduce turbulence. This is a favorite trick with water.
[Tom’s] fog screen starts off with a PC fan to move the air. This airflow is smoothed and guided by a combination of a sponge, and multiple drinking straws. This apparatus is responsible for establishing the laminar flow, as the air picks up fog from an ultrasonic fogger along the way.
The only real problem here is that you want the projector shooting off into infinity. Otherwise, the projection goes right through the fog and displays on the wall, ruining the effect. Outdoor applications are great for this, as long as there’s no air movement to mess with your carefully established fog screen.
You can find a short test clip embedded after the break but there are other videos at the link above.
Continue reading “Ghostly images appear thanks to projections on fog”
Reader [Daniel] told us about a video detailing how to make your own fog machine. This project uses two disposable roasting pans to create a fog chamber. Inside you will find an upside-down clothes iron to convert fog liquid into a gas. The liquid is gravity-fed from a water-bottle reservoir on top, converted to smoke by the hot iron, then the newly created smoke is directed out of the chamber by a 12 volt fan.
You probably have an old iron sitting around (especially if you use the toner transfer method for making PCBs), as well as a fan of some type. The build method used in the video is not at the level we usually look for. Using one blade of a pair of scissors is not what we recommend for stripping wire insulation. We also don’t advocate hot gluing a wire to a battery for a reliable connection (for that you’d want wire glue). But with better building techniques, and perhaps an air intake fan for better fog direction, this has potential.
The project is predicated on the availability of “fog juice”. We’re probably not going to head out and buy a bottle of that so look into making some yourself from glycerin and demineralized water.
Though we’re pretty sure this was meant for Halloween, we think it would be a perfect addition to your election night party. [marc92] shows us how he built a fog spreader with red or blue lighting. Fog machines generally spit out the fog from a single point, relying on the breeze to spread it around. [marc92] wanted it spread a little more evenly, as well as some nice mood lighting. He built a pipe system that would emit fog from a much larger area. Mounted on the pipe are red and blue LEDs. Mix this with some of the election lighting systems and you’re set for a party. We know this is an extremely simple project, so it should give you plenty of time to get out and vote before the polls close.