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High-Tech Electro-Defroster
DahBaker writes to mention a News.com story about an ingenious way to de-ice a surface. From the article: "Dartmouth College engineering professor Victor Petrenko, not to be confused with one of the Champions on Ice, has devised a way to use a burst of electricity to remove ice caked on walls or windows. For surfaces coated with a special film, the jolt gets rid of ice in less than a second, far less time than it takes to hack at it with an ice scraper. While drivers might find easy-cleaning windshields convenient, the technology--called thin-film pulse electrothermal de-icing, or PETD--could have significant economic impact if widely deployed. It could, for example, cut the costs of repairing power lines downed by ice storms and keep plane windshields frost-free, decreasing fuel consumption."
from the article:
"We built a solar cell made of ice," he recalled. "While it is not as efficient as a silicon solar cell, it costs a penny a square mile."
Solar panel that uses ice! This could be very cool for people in colder climates.
In Soviet Russia, articles before post read *you*!
When I was in school, during one of the ASME meetings we had a presentation of a device to remove the ice from the wings. The plan was to have a series of these plates on the leading edge of the plane. during normal flight they would be inlayed into the wing and be aerodynamic. If you were in an icing condition you would start a trickle charge a bank of compactors. Then once the charge was built up a series of panels would "pop" pushing the ice off the wing. Then the caps would recharge and a second series of panels would knock more ice off. and so on. Don't know what happened to the project. anything dealing with aviation takes a long time to develop. It has only been 8 years, which is not really that long for a industry with those types of safety standards.
The problem with it in light aircraft, though, is that such aircraft tend to have very low power budgets--there's not much surplus energy around. If there were, they'd use anti-icing systems, but intermittently shedding accumulated ice is very energy-efficient, especially when compared to energetic ice prevention (some aircraft carry alcohol anti-icing solution, which is excreted through "weeping wings" to forestall ice formation, but such systems are limited in the protection they can offer, both in severity and duration of icing conditions). Thermal anti-icing is cost-prohibitive, and electrical systems in light aircraft tend to be adequate, but with little overhead--while this system is more efficient than (presumably electrical) heating, it still may not be efficient enough. I'd also be interested to see what kind of electrical and magnetic noise this system might generate, though I'm sure that's been considered.
The actual pulse needed to operate the stuff according to the article is in the manner of milliseconds all but the most heavily avionics laden aircraft should be able to handle the short pulse required to remove the ice from the surfaces.
When I was at Cessna, working in the Experimental department, we tested just such a system. That was in 1985 or 1986. One major issue was that the interference with avionics was quite unacceptable, another was that the manufacturing cost was a lot more than the pneumatically inflated de-icing boots that were the status quo. It was quite fun to hold a penny near the leading edge and have it disappear, then hear it hit the wall on the other side of the hangar. Oh, yeah. That reminds me. Metal fatigue of the underlying structure. Simply not acceptable in aircraft.
Preface: I was a grad student at the Thayer School of Engineering, where Petrenko does this research. During a power electronics class, we learned about the workings of some of this technology, and some classmates of mine designed some of the HF electronics that are behind this.
Electrically heated windshields, propellers, etc... have been around for 70+ years. Yes, but those devices have heating elements that conduct heat into the bulk ice. You don't want to spend all the energy needed to melt all of the ice, or even a sizeable portion of it, but rather melt just the ice that's adhered to the windshield or airfoil. This technology does that. It creates HF eddy currents in the ice at the ice-windshield interface, liquifying that thin layer almost instantly. The liquification happens quickly enough that very little heat is conducted away into the bulk, which means that you aren't wasting or losing much energy. What's more, the heat is applied directly to the ice - no heater elements needed. Instead of pumping XX watts of power into heater elements and waiting for enough ice to melt to easily be removed, you pump (let's say) 10 times the power for 1/1000 the time into just the ice that matters, then let gravity, airflow, and wiper blades take care of the rest. It is a far more efficient way to remove ice.
Jet planes spend 95% of their flying time way above or below the icing levels. Unfortunately, the place where icing is most likely is also the place where it is most dangerous: during takeoff and landing. Just because it is not a continuous threat during the flight doesn't mean that it isn't still extremely dangerous.
Jet turbines have a virtually free and unlimited amount of hot air availbale for deicing. The hot gasses need to be hot if they are to produce thrust. Were the gasses diverted through some complicated heat exchanger to melt ice from the airfoils of aircraft, the exit gasses wouldn't produce nearly as much thrust. Once again, this technology works only on the ice that is adhered to the surface, and so works very efficiently. Using hot gasses, like heater elements, inevitably has most of its heat conducted into the bulk, where it does little good.
It's not affordable to load down a plane with 100's of pounds of extra generators, batteries, and/or capacitors that are only needed in very rare and usally avoidable circumstances. This is not additional equipment for an airplane, it is meant to replace the de-icing equipment that some already have. Consider the cost of applying thousands of gallons of chemical de-icing to aircraft wings on the ground, or the electrical equipment needed to generate the huge amount of electrical power that goes into heating elements. If anything, this technology would have less equipment associated with it than other methods, because it uses far less energy. The amount of energy that it takes to use this equipment, even over the entire leading edge of an aircraft's wing, it relatively small compared to the power needed to run everything else, or the tremendous power output of the engines. It makes use of high-frequency power electronics, which are much more compact and efficient than traditional power electronics. True, it isn't need all the time, but there is tons (literally, tons) of equipment in an airplane that is only used occassionally. They all serve a specific purpose. I will admit that it will be expensive technology at the beginning, especially for retrofits, but most new technology is. Airbags were initially only seen in high-end luxury cars, but eventually trickled down to lower models.
The planes that would need this the most, little prop planes that can't climb above icing, are also the ones that can least afford the weight penalty of this deicing system. Adding even 150 pounds to a small plane can make it a non-viable flying machine. Once again, this is not additional equipment, it is meant to replace existing de-icing equipment on a plane.