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NARRATOR: Autoclaves are devices used
to sterilize medical tools in hospitals, clinics,
and doctor's offices.
To be effective, they require a steady supply
of pressurized steam at a temperature
of about 125 degrees Celsius for roughly 30 minutes.
This is usually provided by electrical or fuel powered
boilers.
However, in many rural areas, especially the developing
world, power can be unreliable or unavailable,
and fuel is often quite expensive.
A team of researchers at MIT and the Indian Institute
of Technology has designed and tested
a device that can generate the needed steam using
just the power of sunlight, meaning no need
for fuel or electricity.
The key to their new system is the use
of optically transparent aerogel.
the material is essentially a lightweight foam made of silica
and consists mostly of air.
Light as it is, the material provides
effective thermal insulation, reducing the rate of heat loss
by tenfold.
The insulating material is bonded
to their solar collector, which consists of a copper
plate with a heat absorbing black coating
bonded to a set of pipes on the underside.
As the sun heats the plate, water
flowing through the pipes underneath picks up that heat.
With the insulating layer on top,
plus polished aluminum mirrors on each side of the plate
to direct extra sunlight, the system
can generate high temperature steam
instead of just hot water.
Using gravity to feed water from a tank into the plate,
the steam then rises to the top of the enclosure
and is fed out through another pipe, which
carries the pressurized steam to the autoclave.
The team tested their prototype in Mumbai, India.
And even though the sky was hazy and cloudy
during their testing, providing only 70% of insulation
compared to a sunny day, the device
still succeeded in producing a steady supply
of steam needed for sterilization for the required
half hour period.
The researchers say once the aerogel material becomes
commercialized, the entire system
could be built at a very low cost,
since all the other components are already
widely available throughout the developing world.