Why don’t we use something similar to the tech in microwaves to heat ourselves instead of central heating or electric heaters? Are they less efficient at converting electricity to heat? Do they not have very much range? Or are they too dangerous (I doubt this otherwise the anti-microwavers would have had a field day over it)?
It doesn’t heat the air around you like the majority of home heating methods, but instead, would heat you directly. This is a Very Bad Thing as you would literally be cooking your flesh.
Have you listened to anti-microwave / anti-cellphone people lately? They are already having all kinds of field days of their own.
Actually, you aren’t the first to propose heating via microwaves. Theoretically it would be more efficient since you only heat the people in the room and don’t have to heat the entire room.
In practice, though, it is difficult to do. When radio waves bounce off of things they can get more concentrated in some places, which leads to hot and cold spots all over the room. Get enough concentration and the heating can get to the point of burning human flesh, which is generally considered to be undesirable for this sort of thing.
Because of the safety issues involved, the current exposure limits to radio waves are well below the point where they causes significant heating to humans.
The high power radio waves will also cause all kinds of other problems. They will cause interference to electronic devices and make them work improperly, and in some cases will actually cause damage to them. The radio waves will set up eddy currents in metal objects, which depending on the thickness of the metal could cause them to get very hot.
ETA: Forgot to mention that magnetrons (which are how microwave ovens generate high enough strength radio waves) are about 70 to 75 percent efficient at converting electricity into radio waves, with the rest of the energy going into waste heat at the magnetron.
microwaves penetrate and heat food and cook it. good for food, bad for still living things.
infrared radiation does a good job of heating people/animals without having to heat the air. look for infrared heating or quartz heaters.
- You wouldn’t be able to wear metal jewellery.
- It wouldn’t work unless you sat on a giant turntable in the middle of the room.
Depends entirely on the power level, just as surely as other methods of heating.
If you wanted personal microwave heating to be efficient, you’d have to direct the beam at each person in the room. If it missed, it would just go through the walls and off into oblivion, energy wasted. If you didn’t want that to happen, you’d have to make your walls out of microwave-reflective material, same as the walls of your microwave oven. Windows too: they’d have to all be covered with the same fine screen mesh you see on your microwave oven’s window.
thanks for the answers, in my head I had some sort of maser mounted on a turret heating up people in my garden so we could have a barbecue in crap weather but i guess we’ll just have to deal with it
Come to think of it: Have microwaves ever been proposed as an execution method? Sort of burning at the stake in the 21st century.
Would you want to be the guy who cleans up the ones that “popped?”
Would be regarded as cruel/unusual for humans, since the bulk of incident microwave energy is absorbed in the first inch of depth; a victim would experience extreme pain and severe burns before enough damage was incurred to render him unconscious.
The same is not true for much smaller animals, such as lab rats. Microwave devices like this one are used to “fix” brain tissue, i.e. to preserve the brain chemistry that existed at the time of death. Because a rat’s head is so small, the entire brain heats up evenly throughout its depth, unlike a massive human cranium. My understanding is that this procedure is performed on living animals, and death comes fast enough (<1 second) so that the animal does not experience physical pain before unconsciousness.
There is such a device - it is called Active Denial. It uses short bursts of mm radiation (somewhat longer than microwaves) to heat the outer 0.4mm of the targets skin to approximately 41-55[sup]o[/sup]C for period of a few seconds. The stimulation of nociceptors in this thin layer of skin induces excruciating pain almost instantly, with only a small risk of actual burns forming, and any such burns are shallow. However, this is classified as nonlethal weaponry.
By contrast, actual microwaves penetrate up to 20mm into the skin, and form full depth burns below the nociceptor layer, making microwave burns far more damaging but less painful during the actual burning process.
I believe they’ve been used in test as crowd control devices. Unless I’m not recalling correctly, police have tested microwave devices that they can aim in a direction of a crowd. Anyone in the path of the beam immediately feels an uncomfortable level of heat.
Here we go:
Although I’m not sure if the frequency of the waves they use knocks it out of the microwave range.
Damn, too slow.
When I first started working with microwaves, I was solemnly cautioned never to look down a waveguide because the cornea of the eye was very sensitive to microwave heating and instant cataracts would result. (The sources we were working with could definitely heat your fingertip from the inside, an interesting sensation)
Looks like that’s no longer held to be the case:
You could use microwaves to heat water, then pump it into a radiator/fan assembly. Probably less efficient, or equally efficient but more complicated and expensive than normal electric heaters, though.
It depends on whose definitions you are using. 1 to 100 GHz is a common definition in RF engineering, in which case the active denial systems (which operate at about 95 GHz) would be at the top end of the microwave band. Other folks like to call 30 GHz to 300 GHz the millimeter wave band (since the wavelength works out to between 1 and 10 mm).
So either microwave or millimeter wave is correct. Calling them “high frequency microwaves” might start a few less fights with the folks who like to call them millimeter waves though.
Calling them EHF radio waves also probably wouldn’t get you in too much trouble.
Radient heaters work well if you just want to keep yourself warm and not heat up all the air in a room.
I’ve read that if you turn one of the radars in the nose of an F-15 on to full power you can cause some serious damage to someone 50 feet in front of it.
Sounds like a perfect business opportunity to sell my Faraday Cage lined hazmat suits around rioting crowds and mobs.
Only $49.99 each!
You could make a little more if you add a regulator and usb port, so the rioters can keep their Blackberrys and iPhones all charged up while being irradiated - a good riot is no fun without social networking and instant messaging to keep things on the go 
IMO, radiant heaters actually don’t work all that well, for heating people:
[ul]
[li]If they’re overhead heaters, you get a hot face, but your feet are still frozen[/li][li]If you get close enough to feel the warmth through your clothes, exposed skin will be toasted[/li][li]The side of you facing the heater may be warm, or even too hot, whilst the side facing away will be chilly.[/li][/ul]
I’ve seen them used by loading docks, to try to take the worst of the chill off the folks loading/unloading trailers. They’re still wearing cold weather gear.