A WINTER鈥檚 night. Wind whistles around chimney pots, rattles windows and
sends flurries of snow spiralling down the street. Stepping inside, you switch
on the heating system. Immediately, your cheeks and legs begin to tingle, then
the rest of your body. Within seconds you can feel the heat flowing into your
cold, aching limbs. But there鈥檚 not a radiator or fan heater in sight. And while
you鈥檙e warming up nicely, the walls, furniture and even the air in your house
remain icy cold. So what鈥檚 going on?
Welcome to the world of microwave heating, where your living room is a giant
version of the microwave cooker in your kitchen. Switch it on and microwaves
begin to excite water molecules in your body raising its temperature.
Believe it or not, microwave heating is the subject of serious research in
the US. American researchers have built microwave-heated rooms and even tested
the devices on themselves. They claim microwave heating is safe and far more
efficient than conventional heating.
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The idea is not new. The first tests took place more than a decade ago when
two researchers at Litton Microwave Cooking, a now-defunct cooker maker in
Minneapolis, began to experiment using a small room designed to test the
resilience of standard electronic components to microwaves.
A microwave test room is unlike any ordinary living quarters. In the American
experiments, one wall contained a hole allowing a standard 800-watt transmitter,
about as powerful as those used in kitchen cookers, to beam microwaves into the
room. The walls were clad in metal to reflect the microwaves around the room and
to prevent them escaping. These reflections can cause hot spots, areas where the
microwaves become concentrated. So the room had to be 鈥渟tirred鈥� with large metal
blades attached to the walls. As they revolve around their long axes, these
blades reflect microwaves in different directions and prevent hot spots from
forming鈥攎icrowave cookers contain similar devices.
The guinea pigs were the researchers themselves: Charles Buffler, now at the
Microwave Research Center in Marlborough, New Hampshire and his colleague Ronald
Lentz. Their aim, to determine the radiation threshold at which humans could
sense heat and the power levels at which this remained comfortable.
During each test, the subject sat on a single chair in the room holding a
response button to indicate when he thought the microwave generator had been
switched on. Outside, the other researcher adjusted the power level of the
transmitter.
The pair discovered that they could first detect heating when the power
levels on their skin reached 10 milliwatts per square centimetre (10 mW/cm2),
several hundred times less than the level inside a microwave oven. The first
parts of their bodies to heat up were their legs and cheeks, followed quickly by
the rest. And the effect remained comfortable up to 30 mW/cm2. The results
persuaded them that a household system could be viable.
Buffler says a home system would be a hugely efficient way of keeping warm.
He calculates that microwave heating systems could cut household heating bills
by 75 per cent. And since microwaves cause light bulbs to fluoresce, such a
heating system could also double as the power supply for a system of wireless
lights.
Fear of frying
It would also be possible to control the level of heating. 鈥淲hen food heats
up in a microwave oven, the amount of radiation it absorbs or reflects changes,鈥�
explains Gordon Andrews, chairman of the Microwave Association which represents
the industry in Britain. Advanced microwave ovens already sense this change and
make appropriate adjustments. Andrews believes a room heating system would work
in a similar way, adjusting the power as people enter and leave a room.
But persuading the public will be tough. 鈥淕etting public acceptance of the
idea will be the biggest problem,鈥� says John Osepchuk, a member of the American
Institute of Electronic and Electrical Engineers and a supporter of Buffler鈥檚
ideas. 鈥淎t the moment we have a pervasive electrophobia. People are scared stiff
of the prospect.鈥�
The critics agree and say that the system is doomed. 鈥淚 can鈥檛 believe it
would work,鈥� says John Stather, assistant director of Britain鈥檚 National
Radiation Protection Board in Harwell, Oxfordshire. Buffler鈥檚 experiments were
performed in a room at 24 掳C. If the room were colder, microwave heating would
not necessarily make you feel warmer, says Stather. While microwaves would heat
up internal organs, the skin always remains in contact with cool air. 鈥淵ou鈥檇
still feel cold.鈥�
Buffler admits that furniture would have to be covered in a material that
also heats up so that it wouldn鈥檛 feel cold to the touch. And he and Osepchuk
say there are other drawbacks too. The microwaves would interfere with radio
reception and television displays. And small metal objects such as keys and
coins would become extremely hot. Microwave heating might be cheaper, but it
could still burn a hole in your pocket.
Neither can researchers be certain that microwave heating would be safe.
Buffler admits that heat might build up in parts of the body that are
particularly exposed or poorly supplied with blood. 鈥淭he main areas of concern
are the cornea and the testicles,鈥� he says. Some researchers even worry that the
skull might focus microwaves into the brain. 鈥淚t will take decades of research
before we see any movement from the government agencies who will need to approve
these ideas,鈥� says Buffler.
Nevertheless, Osepchuk believes microwaves could transform society. 鈥淥ne of
the things I foresee is solar satellite power systems鈥攕atellites that
collect solar power and beam it to Earth using microwave radiation,鈥� he says.
This radiation could be used to heat an entire state, perhaps even preventing
frost and the millions of dollars of damage it does to citrus crops. At the same
time, anyone in the area would also heat up, whether they wanted to or not, a
prospect that is nothing to worry about, says Osepchuk. 鈥淟et鈥檚 face it, as it鈥檚
freezing they鈥檇 appreciate a little bit of heat.鈥� Just whether the public will
be as thankful as Osepchuk anticipates, remains to be seen.