As the last of the winter's fuel bills drops on to your doormat, there seems little prospect of lower prices. But there might soon be an answer that will save you money without your having to turn down the thermostat. Nanotechnology could give your central heating system an energy-efficiency boost.
This is a big idea that depends on the very small. The ideas man is Professor Richard Williams of Leeds University and his inspiration is the carbon nanotube - more than 50,000 times thinner than a human hair. Add these nanoparticles to a fluid, even water, and they'll disperse to form a nanofluid. And it is the strange behaviour of such fluids that Williams hopes to harness commercially.
"Mixing tiny particles and fluids and trying to make them stable has been around for a while," says Williams, who has worked in this field for more than 20 years. More recently, scientists have begun to explore the thermal properties of these mixtures.
A carbon nanotube is a hollow cylindrical arrangement of carbon atoms that demonstrates remarkable properties of strength, flexibility and electrical conductivity. This miracle material is also expensive: a kilogram of multi-walled nanotubes (tubes within tubes) might cost £20,000 while the purer single-walled tubes may cost five times that. "They look like a very fine black powder. Often, the particles are in clumps because of the electrostatic charge," says Williams.
Rapid heat transfer
By using this soot-like material, Williams and his colleague, Dr Yulong Ding, have created nanofluids with rates of forced convective heat transfer - the sort you get when you pump a hot fluid to warm a system - four times better than the norm. (Once the fluid being pumped has forcedly warmed your radiator, the heat rises off it passively - that is, by natural convection.)
While that efficiency won't be matched within your boiler's circulating fluid, Williams reckons a 10% gain makes commercial sense.
Nanoparticles behave very differently from bulk materials, rewriting the text books with expressions like quantum effects and nano-enablement.
"In thermal nanofluids, even the mechanisms by which heat is transferred may be different for small particles," says Williams. "It has been surprising that thermal nanofluids have such good thermal properties."
Nanoparticles are already here - in tough shin pads, water-repellent clothing and self-cleaning windows. But putting them in your central heating system is a trickier proposition. How, for example, would you ensure the carbon nanotubes - all you need is a few percent by volume - remain evenly dispersed and don't clog your radiators with a black goo? "We're focusing on getting the formulation right," says Williams, who claims the project is three to five years away from home use.
So what does Dr Doug Parr, the chief scientist at Greenpeace UK, think of carbon nanotubes? After all, fine particulates are already a known health risk. "In terms of established evidence that they are hazardous, the jury must be out," says Parr. "If you think something's going to be hazardous, introducing it to domestic premises has to be a bad idea. There should be no releases to the environment until there is evidence of safety."
Such evidence is not being gathered quickly enough for Professor George Smith of Oxford University. As a materials engineer, he has significant worries. Nanotubes' elongated shape may bypass the body's defences, while research has revealed toxicity problems with water fleas, fish and rodents. But carbon nanotubes are found naturally in the environment from combustion sources - even in 10,000 year-old ice cores.
"Not enough is known about the possible biological hazards associated with the use of nanomaterials in general, and not enough resources are being devoted to the precautionary research needed to find out what the risks are," says Professor Smith.
Harry Swan, carbon nanomaterials business manager at the chemicals company Thomas Swan & Co Ltd, and the great-grandson of the founder, appreciates the safety concerns. "I'm trying to be as open as possible about our nanotube project as it helps for everyone to understand what we are hoping to develop."
The company makes carbon nanotubes by passing methane gas over an iron-and- magnesium-based catalyst in a furnace. Carbon nanotubes grow on the catalyst by chemical vapour deposition, then are washed off to leave a black paste. Swan is working with government departments and other agencies to develop risk assessments and a regulatory regime.
But what happens in 20 years' time if, despite everyone's caution, manufactured carbon nanotubes become the new asbestos? Fortunately, this doesn't seem likely because of the more sensitive measurement techniques, a growing knowledge of particulate risks and the intense global scrutiny of nanotechnology. In an age of high fuel prices, the carbon nanotube might soon be a useful palliative for those painful winter bills.
Right here, right now
More than 200 commercially available products already incorporate nanotechnology. This may be in the form of nanofibres or particles, as well as ultra-thin coatings that enhance the beneficial effects found at the nanoscale. Like all new technologies, many nano-enabled products will command a premium price. Here are some examples of how nanotechnology has been used in certain products:
· stain-repellent clothing: nanofibres keep water from soaking into fabric
· stronger, stiffer tennis racquets and golf clubs: hit the ball harder and more accurately because they flex less
· bouncier tennis balls: less heat lost in flexing means more energy is restored to the bounce
· anti-microbial wound dressings: nanofibres and particles with medically active coatings get to all parts of wound.
· better sunscreen: nanoparticles provide a more even skin coverage
· tougher paint: dried matrix is more resistant to impact
· skin care cream: nanoparticles carry moisture deeper into pores
· car wax: like skin cream and sunscreen, it offers more complete coverage
· self-cleaning windows: dirt slides down nanoscale coating on the outside of windows
· If you'd like to comment on any aspect of Technology Guardian, send your emails to email@example.com