A New Way to Make Microwaves Will Change the World
The Adventurer is a portable battery-powered microwave the size of a Thermos. Campers, hikers, and anyone else away from the grid can make a hot meal in minutes without a fire. Camp cooking could get a whole lot easier.
The three-pound Adventurer is more than a handy piece of kit, though. This is one of the first fruits of a new technology that could not only nuke your lunch on the go, but also make an impact in areas as diverse as crop protection and oil extraction.
The microwave oven was famously discovered by accident in 1946 when Raytheon engineer Percy Spencer found the peanut cluster bar in his pocket had melted while he was working with a military-grade radar magnetron. The idea took some time to catch on; by 1986 only a quarter of households had one. Now microwaves are ubiquitous, and America has warmed to the idea of microwaving popcorn, instant meals, and even, in rare cases, healthy food.
Over all those many decades, though, the heart of the microwave oven has stayed the same. It is the cavity magnetron, developed during WWII for radar. It is big, heavy, and inefficient. The transformer that steps up the voltage from the wall outlet to the Magnetron's operating voltage emits a loud hum, accompanied by the sound of the fan needed to keeping the Magnetron cool, as well as the noise from the turntable that makes sure the food heats evenly.
The military moved away from magnetrons many years ago and now uses solid-state microwave sources. These are transistor-based devices are compact and more efficient at turning electricity into electromagnetic radiation with less waste heat (it's like comparing an LED to an old-fashioned light bulb). Now we're starting to see consumer-grade gadgets finally move away from the old technology and into the world of solid-state.
Enter the Adventurer. This microwave-on-the-go is built around an LDMOS ("laterally diffused metal oxide semiconductor") microwave source made by Dutch company NXP, similar to those used for microwave communications systems. "LDMOS operates on 50 volts, rather than the 3,000 volts that Magnetrons in traditional microwave ovens need," says Professor Alwyn Seeds of University College London. That removes the need for the heavy, noisy transformer and makes the device small enough to put in your day pack.
The Adventurer, set to be launched in the U.S. early next year, will cost $199 and come with a battery that can supply six "cooking cycles" of around five minutes, each enough to make a hot drink or an adult portion of food. Phil Stevens, Chief Operating Officer of manufacturer Wayv, says the Adventurer recharges from mains or vehicle power, and is compatible with portable solar panels. Hikers with solar backpacks could cook meals wherever they go, even on the move. Wayv built the Adventurer with the military in mind, and it may also prove useful for disaster relief and other situations where portability and convenience matter.
Portable gadgets like the Adventurer are just the start-solid-state microwave sources are driving a new generation of kitchen appliances. The Sage is a "smart oven" developed by NXP that combines a convection oven with several microwave sources. Dan Viza of NXP explains that the multiple sources produce a beam that sweeps through the interior of the oven ("like raster scanning"), to produce precise and even heating with no need for a turntable. Alternatively, the beam can sense and heat up different items at different rates, so you could have chicken, potatoes and corn on the same plate all cooked to perfection. There is no release date yet.
Because Sage could sense change of state (frozen to thawed, liquid to steam), it could stop heating just in time to prevent a dish from boiling over. This is not possible with a Magnetron, and it is the key to new applications that go far beyond cookery.
"The 'more controllable' feature cannot be overestimated," says Klaus Werner, executive director of the RF Energy Alliance, an organiation dedicated to realizing the potential of this technology. "It gives you perfect process control via fast control loops. The Magnetron is very slow at best. Sensitive processes such as food pasteurization, blood thawing, sous vide cooking or pharmaceutical reactions all benefit greatly from this technology."
Looking further afield, Werner says that solid state has myriad other possibilities. "The technology allows a number of hitherto impossible radio-frequency applications-automotive ignition, radio-frequency ablation, hypothermia treatment, plasma lighting, novel industrial heating systems…"
At the extreme end of the microwave revolution is a novel alternative to fracking. Rather than injecting the ground with chemicals at high pressure to force hydrocarbons out of shale, Peter Kearl and colleagues at Qmast LLC use microwaves. A high-powered emitter is lowered down a shaft. The microwaves pass through the rock as easily as they do through cookware, heating trapped water and turning it to steam. This opens up cracks and channels, and heats up waxy hydrocarbons so they flow easily and can be recovered (there's an animated video of the process here). The same approach can rehabilitate old 'stripper' wells blocked by build-up of wax.
QMast's current microwave source is a complex device known as a Sheet Beam Klystron, but low-cost, high-power solid-state devices will make the technique increasingly attractive.
The highly efficient heating provided by microwaves also makes them appealing for crop protection. Vines in particular are vulnerable to frost after new leaves break out. The traditional protection is to set out thousands of frost candles to warm the air, which are spectacular but inefficient. Some wine growers are now experimenting with microwave-based heating such as Raytheon's Tempwave in which a series of emitters bathe the vines in gentle warmth when frost threatens. Someday, maybe solid-state microwaves will take our wines to a better state.
