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While reading up on energy efficiency, I came across a report on
copper rotors in the news section of Scientific American (Nov.
2007). If copper were used instead of aluminum for the rotors of
electric motors, as much as 93 percent of energy can be saved.
There was an item in a local paper on Feb. 22
that PASAR plans to spend US$19 million this year to expand its
smelting operations.
I’d like to suggest that instead of making
more cathodes for export, PASAR should think of going into the
business of manufacturing copper rotors. PASAR could make more
money, create hundreds of new jobs, and introduce a new technology
to local industries.
There are millions of electric motors all over
the world to drive pumps, compressors, fans, conveyors, elevators
and other devices in factories and homes.
Automobile makers are experimenting with
ultra-efficient electric motors with copper rotors. Tesla Motors,
for example, produced a prototype of a battery-powered electric
racecar that can accelerate from zero to 96.54 kilometers per hour
in 3.9 seconds and has a driving range of 321.8 kilometers with a
250-horsepower copper-rotor motor. The US Department of Defense is
ordering a hybrid vehicle that can energize field hospitals, command
and communication centers, and airstrips. It uses a 140-horsepower
electric motor with a copper rotor.
In short, the market for copper rotors can only
go up in the coming years.
Present-day three-phase AC induction motors with
aluminum rotors that generate from one to 20 hp are 90-percent
efficient. The difference is energy efficiency between them and
motors with copper rotors is 3 percent.
This might not sound much but given that over 30
percent of the world’s electricity is used to drive AC induction
motors, the potential saving is huge. Researchers at the Copper
Development Association (CDA) in the US calculate that
copper-rotor-equipped machines pay for themselves in about a year in
energy saved.
Engineers and materials scientists have known
for a long time that copper is better than aluminum because
“copper has substantially higher electrical conductivity than
aluminum, which significantly cuts the resistive losses in
rotors,” to borrow the words in the SA article of Dale Peters, a
metallurgist at the CDA “But copper melts at 1,083 degrees
Celsius, significantly hotter than aluminum’s melting point, which
poses big problems for die casters.”
It was the technology of die casting that held
back the adoption of copper rotors.
Die casting involves pouring molten metal into a
reusable steel mold called dies. When molten copper is injected into
steel dies, the heat causes the die to expand and then contract
making it difficult to produce uniform casts.
It took Peters and the CDA a decade to discover
a reliable and cost-effective die-casting method. Their initial
discovery that by pre-heating the steel dies it was possible to make
industrially acceptable casts. Except that pre-heating shortened the
useful life of the die—and making a die is a large part of overall
costs. After numerous trials, they found a heat-resistant alloy
based on nickel.
Die-cast copper rotors reduce resistive losses.
The motors in which they are incorporated are also smaller, lighter
and more durable. However, they cost 5 percent more than motors with
aluminum rotors. But with fuel prices at all-time highs and no sign
of dropping, copper rotors could become the industry standard.
Already the US, Japan, Brazil, India and China
have begun to make electric motors with copper rotors. Siemens and
SEW Euro drive have introduced them in the European market.
PASAR should perhaps acquire the license to the
new technology from CDA. Why should we export our copper cathodes
to, say, China and then import electric motors that use our copper?
Die-casting is labor-intensive and can be
adapted to small and medium enterprises. We should be competitive
with China and Brazil on labor cost and product quality.
But in addition to profits, getting into
copper-rotor making will help reduce greenhouse gases in the long
term.
The Department of Energy, the Department of
Trade and Industry and the Department of Science and Technology
should collaborate to make copper rotors one of the Philippines new
export products.
mlatimes@gmail.com
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