Ambient Backscatter-Free Energy Harvesting

[markdansie]

Thought this would appeal to the electronic hobbyists.


http://revolution-green.com/2013/07/09/ambient-backscatter-free-energy-harvesting/


Kind Regards
Mark

[conradelektro]

The most promising technology seem to be "rectennas" or "nantennas" to "receive" infrared radiation (heat). But nobody has ever built a useful device. May be it will be possible to build the necessary diodes and antennas with nano technology (on a nano scale).

Greetings, Conrad


http://spie.org/x51851.xml

Cited from the above web page:

Antenna-coupled diode solar cells, also called rectenna solar cells, work on an entirely different principle, much like a crystal radio receiver but for light. Incoming solar radiation (electromagnetic waves) is received by sub-micron-size antennas, which convert it to ultra-high-frequency alternating current (AC). This current passes through a nanometer-scale, ultra-high-frequency diode, which converts the AC to direct current (DC) and provides usable power (see Figure 1). A solar cell would incorporate a large array of millions of these elements in tandem deposited onto a glass or plastic substrate. Fabrication costs can be low, with devices processed cheaply in a roll-to-roll process.

In principle, the conversion efficiency for rectenna solar cells can be very high, limited to 93% by the entropy of the photon gas, but other constraints limit the efficiency to well below this number. The demands placed on the diode are extreme. First, it must operate efficiently at extremely high frequencies—close to a petahertz (10¹⁵Hz) for visible light—orders of magnitude higher than the fastest electronics. Second, it must couple electrical power efficiently from the antenna. To do so, the impedance (a measure of the ratio of the voltage magnitude and phase to that of the current in an electronic element) of the diode must match the low impedance of the antenna. Unfortunately, the two requirements conflict with each other. An additional challenge for rectenna solar cells is power loss in the antenna, because, at petahertz frequencies, metals become very resistive. One possible solution is to use dielectric antennas.

A particular implementation for rectenna solar cells was patented in 1984. In a project led by ITN Energy Systems, our group developed metal/insulator/metal (MIM) diodes for rectenna solar cells. MIM diodes make use of femtosecond-fast transport of electrons tunneling through a nanometer-thick insulating region.


http://en.wikipedia.org/wiki/Rectenna

Cited from the Wikipedia page:

It has been theorized that similar devices, scaled down to the proportions used in nanotechnology, could be used to convert light into electricity at greater efficiencies than what is currently possible with solar cells. This type of device is called an optical rectenna or nantenna. Theoretically, high efficiencies can be maintained as the device shrinks, but experiments funded by the United States National Renewable Energy Laboratory have so far only obtained roughly 1% efficiency while using infrared light. Nevertheless, Missouri University recently reported on work to develop low-cost, high-efficiency nantennas (optical-frequency rectennas).

[profitis]

up-conversion of light may be the key rather than rectification.a one thomas prevenslik has created nano sized silica shells that glow with intense visible light non-stop,up-conversion of ambient infrared to visible/uv taking place with no expenditure of energy in the shells.we could put them in front of a photovoltaic cell and get electricity at all times anywhere.