How to eradicate power poles in Nigeria

How to eradicate power poles in Nigeria

Postby Richard Akindele » Mon Jul 31, 2006 9:04 pm

A familiar sight in Nigeria a electric power poles, with aluminium wires on them for carrying electricity all across a city.

Go and look down the street in a major city. You'll see cars and buildings and people, but if you're a typical city-dweller, it may take a conscious effort for you to notice the aluminium cables festooned from poles everywhere.

You see the poles and cables so often, so regularly, so completely ubiquitously, that they don't even register. The same part of your brain that studiously ignores Web page ad banners is called upon to erase poles and wires from your memory.

Don't expect these particular ubiquitous pieces of technology to go away any time soon.

Many of the wires that are used for data - moving data from device to device, or around within the one gadget - are already being replaced by better technology. Radio communication gets rid of the cable; optic fibre massively reduces the number of cable strands needed for a given amount of data bandwidth.

Optical data transmission from place to place is now the rule, not the exception. It's now quite difficult to telephone anybody anywhere in a developed nation without your voice being turned into photons for part of the journey.

Most of the cables that are still strung around cities today, though, aren't data wires. Here in Australia, thick cables strung low on the pole are probably for cable TV, but the thinner wires further up carry power. You can't run your toaster from an optic fibre.

Strung power wires are pretty much all made of aluminium. A cable of a given thickness made from aluminium isn't as good a conductor as a cable the same size made from copper, but by weight, aluminium's more than twice as good. And weight is very important when you're hanging wires from poles. So we have aluminium power cables, that're thicker but lighter than a copper cable would be.

As urban power demands rise - and they are rising, despite our best efforts - the power transfer capacity of the electrical grid has to rise too. That means larger transmission towers for the long cable runs, with thicker cables (for more current capacity), held further from the towers (for more voltage capacity without arcing). The more power you want to move, the bigger and uglier and more expensive all this stuff gets. You also start striking problems like finding room for extra suburban substations, to step down the long-distance high voltage to domestic low-ish voltage.

Power wires can be run underground; some are. But doing that requires a lot of conduit space and a surprising amount of cooling. That's because of resistance. Power cables aren't perfect conductors, so they turn some of the electricity passing through them into heat. That means they need to be cooled if they're underground, and it also means that they have to be rather fat if they're to transfer a lot of power, even if it's at very high voltage and thus relatively low current.

Resistanceless materials - superconductors - look like a very good thing in comparison. Up to a point, a superconductor has literally no electrical resistance. No power's wasted as heat, and a very large amount of electricity can be pumped through a quite small conductor. And we can make cable-ish things out of high temperature superconducting material, now. They're being used in some trial power transmission projects already.

Don't expect to see them in your neighbourhood any time soon, though. "High temperature", in this context, still means "cooled by liquid nitrogen". Room temperature superconductors remain quite a long way off.

Cryogenic superconductor cables let city-level power supplies be routed through relatively small conduits with near-zero loss, but they're hardly user-friendly. They're prize bastards to repair, for instance. Never mind grafting in a new piece of ceramic cable to replace a damaged portion; before you can even start a repair job on a cryo-cable you have to wait for it to warm up. And, after you've finished, you've got to cool it down again before it can be put back in service. The cool-and-warm cycle can take weeks.

You can't, in case you're wondering, beam domestic power through the air. Once again, data can be broadcast or narrowcast with relative ease, but power can't.

Microwave power transmission is quite practical, provided you've got line of sight and it isn't raining. But microwave transmission either has to use narrow high energy beams that're a very severe health hazard indeed for any living thing that cops one in the giblets, or wide low energy beams that need gigantic receiving antennae. This latter solution could work if we ever build solar power satellites and need a way to get the power to the ground; a vast receiving antenna bathed in rather less radiation per square metre than the sun delivers at noon would be a safe way to get the megawatts from there to here. But you couldn't fit such an antenna in your back yard. Actually, there's a good chance that it wouldn't fit in your postcode.

Getting plain old suburban power cables off poles and under the ground is, at the moment, just a matter of money. Here in Australia, Local councils that can raise the money can do it. In cities in some other countries, particularly where the population density is high and the mean income is large, overhead cables are already a thing of the past, and nothing but existing technology's been used to vanish them.

Ordinary wires-in-a-ventilated-tunnel technology is what we're going to have to keep using for some time, though, because non-cryogenic superconductors are still fantasy tech, and no other sensible option exists.

Wires inside our gadgets may turn into lightguides, and most of the world's short interconnecting cables may go away, thanks to 802.11 and Bluetooth and so forth. But power wires will be with us for a long time yet.

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Richard Akindele
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