[AI] Unplugged: Goodbye cables, hello energy beams

aisha sahani mailtoaishasahani at gmail.com
Fri Jun 18 03:55:50 EDT 2010

very interesting, but i would be much more interested to discover
something that can work completely on soller energy.

imagine, how greatly it will reduce the power consumption.

anyways, pretty interesting.

aisha sahani.

On 6/17/10, Sanjay <ilovecold at gmail.com> wrote:
>           Your gadgets are finally about to become truly wireless - as long
>           as you don't mind lasers criss-crossing your living room
> by David Robson
> LET'S face it: power cables are unsightly dust-traps. PCs, TVs and
> music players are becoming slicker every year, but the nest of vipers
> in the corner of every room remains an ugly impediment to true
> minimalism.
> Then there is the inconvenience of charging phones, MP3 players and
> PDAs. A minor hassle, admittedly, but it is easy to forget to top up
> the batteries and before you know it you have left the house with a
> dead gadget. Wouldn't life be simpler if power was invisibly beamed to
> your devices whenever you walked into a building with an electricity
> supply? Wireless communication is ubiquitous, after all, so why can't
> we permanently unshackle our electronics from power cables too?
> Poor transmission efficiencies and safety concerns have plagued
> attempts at wireless power transfer, but a handful of start-ups - and
> some big names, like Sony and Intel - are having another go at making
> it work. The last few years have seen promising demonstrations of
> cellphones, laptops and TVs being powered wirelessly. Are we on our
> way to waving goodbye to wires once and for all?
> The idea of wireless power transfer is almost as old as electricity
> generation itself. At the beginning of the 20th century, Nikola Tesla
> proposed using huge coils to transmit electricity through the
> troposphere to power homes. He even started building Wardenclyffe
> Tower on Long Island, New York, an enormous telecommunications tower
> that would also test his idea for wireless power transmission. The
> story goes that his backers pulled the funding when they realised
> there would be no feasible way to ensure people paid for the
> electricity they were using, and the wired power grid sprang up
> instead.
> Wireless transmission emerged again in the 1960s, with a demonstration
> of a miniature helicopter powered using microwaves beamed from the
> ground. Some have even suggested that one day we might power
> spaceships by beaming power to them with lasers (New Scientist, 17
> February 1996, p 28). As well as this, much theoretical work has gone
> into exploring the possibility of beaming power down to Earth from
> satellites that harvest solar energy (New Scientist, 24 November
> 2007, p 42).
> Long-distance ground-to-ground wireless power transmission would
> require expensive infrastructure, however, and with concerns over the
> safety of transmitting it via high-power microwaves, the idea has been
> met with trepidation.
> While we won't be seeing a wireless power grid any time soon, the idea
> of beaming power on a smaller scale is rapidly gaining momentum. That
> is largely because, with wireless communication, like Wi-Fi and
> Bluetooth, and ever-shrinking circuits, power cables are now the only
> limit to becoming truly portable. "The move was inevitable once
> wireless communication became popular," says David Graham, a
> co-founder of Powerbeam in San Jose, California.
> With this new impetus, engineers and start-up companies have jumped at
> the challenge, and while beamed power is still in its infancy, three
> viable options seem to be emerging. The use of radio waves to transmit
> electricity is perhaps the most obvious solution, since you can in
> principle use the same kinds of transmitters and receivers used in
> Wi-Fi communication. Powercast, based in Pittsburgh, Pennsylvania,
> has recently used this technology to transmit microwatts and
> milliwatts of power over at least 15 metres to industrial sensors.
> They believe a similar approach could one day be used to recharge
> small devices like remote controls, alarm clocks and even cellphones.
> A second possibility, for more power-hungry devices, is to fire a
> finely focused infrared laser beam at a photovoltaic cell, which
> converts the beam back to electrical energy. It's an approach
> PowerBeam has adopted, but so far its efficiency is only between 15
> and 30 per cent. While that could serve more power-hungry appliances,
> it would in practice be too wasteful.
> The technology has been used to power wireless lamps, speakers and
> electronic photo frames that require less than 10 watts to function.
> Over time, as both the lasers and photovoltaic cells improve, the
> company hopes efficiencies of up to 50 per cent will be possible.
> "There's no reason we couldn't power a laptop eventually," says
> Graham. Unlike some other possible techniques, a sharply focused beam
> loses minimal energy over large distances, preserving its efficiency:
> "A hundred metres is no big deal."
> Inconvenient beams
> Others are sceptical that this technique would be practical for truly
> portable devices, which are constantly moving around and between
> rooms. "An infrared beam would not be convenient to charge a mobile
> phone - it's too directional," says Menno Treffers, chairman of
> the Wireless Power Consortium in the Netherlands. Powerbeam's solution
> is to fit a small fluorescent bulb to the receiving device so that a
> camera on the transmitter can track the light and steer the laser beam
> accordingly. Another problem is that a separate beam is needed for
> each device you want to power, which would be tricky to engineer, says
> Aristeidis Karalis at the Massachusetts Institute of Technology,
> who is developing an alternative wireless power transmission system.
> The third possibility for wireless power is magnetic induction - the
> most attractive option for beefy domestic applications. A fluctuating
> magnetic field emanating from one coil can induce an electric current
> in another coil close by, which is how many devices, like electric
> toothbrushes and even some cellphones, recharge drained batteries. The
> snag, however, has been that while efficiency is good at close
> contact, it can drop to zero at even a few millimetres from the
> transmitter.
> Enter Karalis and his colleagues. It has long been known that such
> mechanical energy transfer is improved enormously if two objects
> resonate at the same frequency - it's how an opera singer can smash a
> glass if she hits the right pitch. Karalis wondered whether the same
> idea could improve the efficiency of magnetic induction at greater
> distances.
> The team's set-up consisted of an inducting coil connected to a
> capacitor. The energy within this circuit oscillates rapidly between
> an electric field in the capacitor and a magnetic field in the coil.
> The frequency of this oscillation is controlled by the capacitor's
> ability to store charge and the coil's ability to produce a magnetic
> field. If the frequency in the energy-transmitter's circuit is
> different from that of the receiver's circuit, they are non-resonant.
> The result is that the magnetic field coming from the transmitter
> interferes destructively with the field building up in the receiver,
> constraining energy transfer. But if the transmitter and receiver are
> resonant, the team reasoned, the oscillating fields of their two coils
> would always be in sync, meaning the interference is constructive and
> the amount of energy transferred is boosted.
> They tested their theory in 2007 with great success, transmitting
> 60 watts across 2 metres, with 40 per cent efficiency (Science,
> vol 317, p 83). The team has since founded a company called
> WiTricity to develop the idea. Last year, the firm used two square
> coils 30 centimetres across, one in the receiver and one in the
> transmitter, to power a 50-watt TV 0.5 metres from the power supply,
> with an impressive 70 per cent efficiency. "In some cases, the
> improvement in the efficiency due to resonance can be more than
> 100,000 times that of non-resonant induction," says Karalis. Unlike
> laser-based line-of-sight energy transmission, a magnetic field is not
> focused and so can pass around or through obstacles between the
> transmitter and receiver.
> The big consumer electronics companies have also been keen to
> investigate "resonant transfer". Sony, for example, has demonstrated a
> wireless TV, and Intel is investigating the technology for a range of
> devices. "Power transfer efficiency scales independently of power, so
> the same efficiency can be achieved for laptops, consumer electronics
> such as TVs, and smaller portable devices such as cellphones," says
> Emily Cooper, a research engineer at Intel's labs in Seattle. In other
> words, the same proportion of the total energy will be lost for a
> power-hungry plasma TV as for a tiny PDA.
> Sony has tested a wireless TV, and Intel is investigating the
> technology for a range of devices
> With such promising demonstrations, it seems likely that wireless
> power will one day enter our homes in a big way. A technical standard,
> dubbed Qi, is already being established for the non-resonant
> magnetic-induction technique and compatible charging mats will soon be
> available. It is early days for the other techniques, but similar
> standards are likely to emerge.
> With such promising demonstrations it seems likely wireless power will
> enter our homes in a big way
> Damage to the person
> The technology is likely to meet some objections along the way,
> however. For one thing, you would be forgiven for being a little
> worried about zapping relatively high-power energy beams through the
> atmosphere. Take laser transmission, for example. "High powers
> concentrated in a narrow laser beam could cause serious damage to a
> person," says Karalis. That shouldn't be a danger with PowerBeam's
> products: if the small camera on the transmitter fails to see the
> small light bulb of the receiver, it shuts down the laser within
> milliseconds. And as a failsafe, the receiver also sends a message to
> the transmitter via radio if it notices an unexplained interruption in
> power reception.
> Exposure to radio waves and fluctuating magnetic fields also have
> their potential dangers. If they transmit heat to our cells, they can
> damage tissue over a long period of time. "All the technologies pose a
> potential risk for thermal interaction with the body, in the same way
> that radiation from cellphones does," says Rudiger Matthes,
> vice-chairman of the International Commission on Non-Ionizing
> Radiation Protection in Oberschleioheim, Germany. But, provided the
> exposure is below the thresholds put forward in guidelines from
> ICNIRP, which companies like WiTricity are following closely, it
> should not be a problem.
> The fear remains that electromagnetic fields could damage tissue
> through some other, non-thermal mechanism, a concern raised by many
> biophysicists about cellphone signals. Without any available cohort
> studies to test exposure over a long period of time, though, they have
> had to rely on lab studies, which failed to find any clear or
> reproducible biological effects. "The matter is still open to debate,"
> says David de Pomerai at the University of Nottingham in the UK, who
> studies the effect of microwaves on nematode worms. If the wireless
> power transmission methods all fall within the ICNIRP's criteria, he
> says that the exposure should be no more risky than that from
> cellphones.
> Perhaps more pressing, though, are environmental concerns. With global
> warming an ever increasing issue, most people are looking for ways to
> improve efficiency and save energy - and therefore reduce
> power-station emissions of greenhouse gases. To some people, wireless
> power transmission will seem like a distinctly profligate and
> retrograde step.
> "The fact that these appliances are only 10 to 60 per cent efficient
> means that 90 to 40 per cent of the electricity the householder is
> paying for is wasted," says Paula Owen, who heads the statistics group
> at the Energy Saving Trust, based in London. "Consider these
> products next to other typical household appliances. Boilers, for
> example, are now over 90 per cent efficient. It seems we are going
> back to the days of incandescent bulbs, which were only 5 per cent
> efficient at creating light and are now being phased out."
> Taking individual gadgets, the energy losses might seem small, but
> scaling up to a truly wireless home would be a much bigger deal. The
> question is, would you be prepared to throw away your green
> credentials for wire-free, minimalist beauty?
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