There has been a lot of complaining in Japan, China, and elsewhere
about the high price of (mostly Western) copper lately, but is
anyone really looking at alternatives seriously?
With hybrid cars, this can be an important issue - as they need
much more electrical conductor - and the buyer ends up paying a
huge premium for a traditional metal (required by codes) - which
might not be the best choice for many applications - that is, if a
surprising (and light weight but corrosive) alternative conductor
ever gets into mass production. Of course, there is aluminum, as
an alternative - but an even lighter and much cheaper choice (yet
more of a corrosion risk) is sodium. Plus Na is a byproduct of
PVC production. It can be clad with anodized Al or plastic, and
still be much cheaper.
A 'conspiracy theorist' [do any frequent this forum?], might opine
that copper prices are possibly being manipulated as a competitive
measure to lower the high demand for the Hybrids vs Detroit iron.
The buyer of a Prius is paying, in effect, an added $500 copper
tax... hmmm... probably more of a situation of 'market
opportunism' - than real manipulation.
25 years ago a decent study was done on the subject of alternative
conductors; and this report came out of it: "A single insulated
sodium conductor for HVDC underwater power transmission" Author:
Dunlap, R. M. It would be interesting to know if anyone is
pursuing alternative like this, in today's economy - or have the
Alcoa's of the world squelched such inquiry... Terry might know?
Abstract
The minimum energy transmission cost cable configuration for HVDC
underwater power transmission is considered. Cable material costs,
energy losses, operating temperatures, bend radii, terminal
voltages, currents, and resistances are determined. Electrode
design, single vs two conductor transmission, splices, insulation,
control of buoyancy, operating hazards, and the cost per unit of
energy are analyzed. It is concluded that the use of a sodium
conductor insulated with polyethylene for HVDC underwater power
transmission is superior to copper conductor with the same
insulation due to its reduced transmission cost, avoidance of
strategic materials (copper), flexibility, near neutral buoyancy
in water avoiding high stresses laying in deep water, lower
received voltage, and lower operating temperature.
END of 25 year old report.
Nowadays, copper is at least ten time higher in cost then it was
when the study was done, and sodium is little different (in
potential cost as a by-product). As for properties:
Sodium - on a per weight basis - will carry three times more
current than copper for the same temperature rise; but is 9+ times
less dense; consequently, for a wire of the same size it will
only carry about a third the current. Plus sodium requires much
better insulation against air and water. Wire diameter, as opposed
to actual weight, is important in motors, generators and
alternators - but with a cost differential (per amp carried) of at
least 10-1 (in today's market) and a weight advantage which makes
hanging wire much easier for crews, it is puzzling why we have
not seen some published R&D (relating to why it is not feasible to
switch some applications to clad-Na) or else consider changing the
standards - especially by the Japanese, who have neither much
copper nor aluminum resources ...but are totally surrounded by
megatons of sodium <g>.
Jones
