Talk:Wireless energy transfer/Laser

Laser
The benefits of Laser based energy are:
 * 1) collimated monochromatic wavefront propagation allows narrow beam cross-section area for energy confinement over large ranges.

http://nobelprize.org/educational_games/physics/laser/facts/index.html "Every part of the beam has (almost) the exact same direction and the beam will therefore diverge very little. With a good laser an object at a distance of 1 km (0.6 mile) can be illuminated with a dot about 60 mm (2.3 inches) in radius. As it is so parallel it can also be focused to very small diameters where the concentration of light energy becomes so great that you can cut, drill or turn with the beam. It also makes it possible to illuminate and examine very tiny details."

http://nobelprize.org/educational_games/physics/laser/facts/applications.html

http://nobelprize.org/educational_games/physics/laser/facts/use.html

http://nobelprize.org/educational_games/physics/laser/facts/history.html

(63.146.69.17 (talk) 20:36, 4 November 2008 (UTC))

These allow laser-based Wireless Energy Transfer concept to compete with RF or inductive methods.
 * 1) compact size of solid state lasers-photovoltaics allows ease of integration into products with small form factors.
 * 2) ability to control radio-frequency interference to existing communication devices i.e. wi-fi and cell phones.
 * 3) control of Wireless Energy Access, instead of omnidirectional transfer where there can be no authentication before transfer.

The Laser "powerbeaming" technology has been mostly explored in military weapons (in Directed-energy_weapons ) and aerospace Laser_propulsion  applications and is now being developed for commercial low-power applications. Wireless energy transfer system using laser for consumer space has to meet critical Laser safety requirements standardized under IEC 60825.

Laser beam propagation The wiki Laser page has "Laser light is usually spatially coherent, which means that the light either is emitted in a narrow, low-divergence beam, or can be converted into one with the help of optical components such as lenses.". The page on diffraction has the following information on diffraction of a spatially coherent monochromatic beam "http://en.wikipedia.org/wiki/Diffraction#Propagation_of_a_laser_beam". Is this a sufficient source for point (63.146.69.17 (talk) 23:29, 17 October 2008 (UTC))

Spatial and Temporal Coherence in a Laser beam
 * 1) http://www.rp-photonics.com/coherence.html
 * 2) http://scienceworld.wolfram.com/physics/SpatialCoherenceScale.html(63.146.69.17 (talk) 00:36, 18 October 2008 (UTC))

Laser


In the case of light, power can be transmitted by converting electricity into a laser beam that is then fired at a solar cell receiver. This is generally known as "powerbeaming".

Its drawbacks are:
 * 1) Conversion to light, such as with a laser, is moderately inefficient (although quantum cascade lasers improve this)
 * 2) Conversion back into electricity is moderately inefficient, with photovoltaic cells achieving 40%-50% efficiency. (Note that conversion efficiency is rather higher with monochromatic light than with insolation of solar panels).
 * 3) Atmospheric absorption causes losses.
 * 4) As with microwave beaming, this method requires a direct line of sight with the target.

There are also a few unique advantages of Laser based energy transfer that outweigh the disadvantages. These allow laser-based Wireless Energy Transfer concept to compete with conventional energy transfer methods.
 * 1) collimated monochromatic wavefront propagation allows narrow beam cross-section area for energy confinement over large ranges.
 * 2) compact size of solid state lasers-photovoltaics semiconductor diodes allows ease of integration into products with small form factors.
 * 3) ability to operate with zero radio-frequency interference to existing communication devices i.e. wi-fi and cell phones.
 * 4) control of Wireless Energy Access, instead of omnidirectional transfer where there can be no authentication before transferring energy.

The Laser "powerbeaming" technology has been mostly explored in military weapons  and aerospace  applications and is now being developed for commercial and consumer electronics Low-Power applications. Wireless energy transfer system using laser for consumer space has to satisfy Laser safety requirements standardized under IEC 60825.

To develop an understanding of the trade-offs of Laser "a special type of light wave" based system:
 * 1) Propagation of a laser beam  (on how Laser beam propagation is much less affected by diffraction limits)
 * 2) Coherence and the range limitation problem (on how spatial and spectral coherence characteristics of Lasers allows better distance-to-power capabilities )
 * 3) Airy disk (on how most fundamentally wavelength dictates the size of a disk with distance)
 * 4) Applications of laser diodes (on how the laser sources are utilized in various industries and their sizes are reducing for better integration)

Geoffrey Landis  is one of the pioneers of Solar Power Satellite and Laser-based transfer of energy especially for Space and Lunar missions. The continuously increasing demand for safe and frequent space missions has resulted in serious thoughts on a futuristic Space elevator that would be powered by Lasers. NASA's Space elevator need wireless power to be beamed to it, for it to climb a tether.

NASA's Dryden Flight Research Center has demonstrated flight of a lightweight unmanned model plane powered by a laser beam. This concept allows a periodic recharging using Laser beam and an unlimited time in air. —Preceding unsigned comment added by 59.92.95.170 (talk) 17:22, 26 February 2009 (UTC)