Wireless electricity products spark a new industry

2. Radio-frequency

PowerCast offer a wireless electricity technology based on what's known as radio frequency, or RF. This can transmit power across distances of up to 85 feet. A transmitter plugs into the wall, and a dime-size receiver (the real innovation, costing about $5 to make) can be embedded into any low-voltage device. The Powercast demonstration transmits 3 Watts at 900Mhz through a patch antenna that is received by several LED equipped rectenna, which is a simple dipole antenna with a Schottky diode at the feedpoint that converts radio waves into direct current. Powercast and its first major partner, electronics giant Philips, are set to launch their first device powered by electricity broadcast through the air.

3. Laser

PowerBeam showcases wireless lamps and picture frames. Located in Sunnyvale, Calif., the company uses yet another wireless-powering approach. Its technology beams optical energy into photovoltaic cells using laser diodes. Although the company says it can maintain a constant energy flow across long distances, the difficultly of targeting a laser means that it's not ideal for charging moving devices. Their laser can currently generate about 1.5 watts of power to solar cell 10 metres away. This would be enough to power an electronic speaker or small LED (light-emitting diode) lights, but not enough to operate a laptop, which requires an estimated 30 to 50 watts. However, the company claims that the technology could comfortably be scaled up.

4. Conductive Pad

Boulder, Colorado based WildCharge is demonstrating a mat that uses a conductive powering technique. This is more efficient than inductive powering but requires direct contact between the devices and the charging pad. Though most of the mats or pads on display are intended to power only a handful of devices at a time, WildCharge says the product design is certified for up to 150 watts - enough to power 30 laptops.

5. Magnetically Coupled Resonance

Another wireless power technology is on display in a private suite high in the Venetian hotel tower. Magnetically Coupled Resonance was demonstrated in 2007 when an MIT scientist demonstrated wireless powering of a 60W light bulb with 40% efficiency at a 2m (7ft) and has been dubbed WiTricity. As proof that it works, an LCD TV is powered by a coil hidden behind an oil painting located 5 feet away. Another demonstration involves walking in the direction of another coil with an iPod Touch in your hand, it starts to charge when it gets within two meters.

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