Power Chips

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Power Chips
A presentation by Tim Reece
(Introduction to Electrical Engineering ,
Semester 2 , 2002 )
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Thermotunneling
Power Chips are small, solid-state devices which
generate electricity through a process known as
Thermo-tunnelling, which uses heat to transfer
electrons from one side of a diode to
another.This system is still under development by
the company Power Chips plc, and it is hoped
this technology will be able to recover energy
from the waste heat generated in traditional
engines and turbines,or replace them
completely.Their abilities could also be used to
increase output and reduce costs for Geothermal
power .
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Thermionic Convertors
The main hurdle in producing an effective
Thermo-tunnelling device has been the inability
to produce a surface gap small enough for
electrons to Tunnel rather than jump.Systems in
which electrons jump across a gap are referred
to as Thermionic Converters , which have a gap of
between 1 10 microns , which is the limits of
current machining finishes .
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Although this is a very small distance , it is
quite substantial on the atomic level , and these
systems require extreme temperatures to raise the
materials work function (V l)to a level high
enough to promote the movement of electrons ,
most of which will be lost in the gap.
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Current Thermo-tunnelling devices contain a
cathode and anode separated by an insulating
material , such as Aluminium Oxide . But these
systems also contain the same drawbacks as their
Thermionic counterparts .
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The ideal solution would be to combine the
positive characteristics both techniques ,
Thermo-tunnelling through a vacuum . Now , with
Power Chips plcs new production technique , this
will be possible.
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Copper wafer
1-10nm
gap
silicon wafer
Their solution is to work with the imperfections
in the surfaces, matching these minute pits and
ridges on one side of the chip with the other
side.
They began first with a silicon wafer polished
until the ridges are about 0.5 microns.
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100nm
A 100nm film of lead was then deposited onto the
wafer of silicon.
Then a 5micron strip of copper is grafted on top
of this , and grown until it is in the vicinity
of 650microns.
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These two wafers are then separated , and the
lead is then removed by freezing the entire chip
with liquid nitrogen , which turns the lead to a
dust allowing its easy removal.
Once the lead has been removed , the two wafers
are then brought back together within
10nanometres of each other , an acceptable
distance for a tunnelling converter with the
added benefits associated with Thermionic
Converters .
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To maximize efficiency the chips are best used in
an array , wired electrically in series and
thermally in parallel . This maintains the
current and boosts the voltage due to their high
amperage/low voltage characteristics .
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The projected Carnot efficiency calculations show
a loss of merely 12-15 , which compares
extremely well with the more established
technologies . And the most exciting part of
these comparisons is that Power-Chips are in
there infancy , whereas these other technologies
have been developed for years.
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I V curve
Power-Chips claim to have achieved tunnelling
currents of up to 10 amps , which is several
times higher than any other converter , across
an area of 1 square cm. Their ultimate goal is to
produce a chip for under A1.00 , from which
power could be produced for about 1-10 cents per
watt capacity(dependant upon the heat source)
.Tests are still under way which may vastly
improve these results , but they are still a
long way off.
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RESOURCES
www.solaraccess.com   www.powerchips.gi   www.cres
t.org   Encyclopaedia Britannica