[AI] Unplugged: Goodbye cables, hello energy beams

Subramani L lsubramani at deccanherald.co.in
Fri Jun 18 07:15:10 EDT 2010

Photovoltaic Cells (which are semiconductors) are already getting
installed to do this, but they are still too costly for widespread
deployment. Perhaps it may happen in the next few years. 



-----Original Message-----
From: accessindia-bounces at accessindia.org.in
[mailto:accessindia-bounces at accessindia.org.in] On Behalf Of aisha
Sent: Friday, June 18, 2010 1:26 PM
To: accessindia at accessindia.org.in
Subject: Re: [AI] Unplugged: Goodbye cables, hello energy beams

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
>           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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