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Microwave power transmission (MPT) is the use of microwaves to transmit power through outer space or the atmosphere without the need for wires. It is a sub-type of the more general wireless energy transfer methods.Following World War II, which saw the development of high-power microwave emitters known as cavity magnetrons, the idea of using microwaves to transmit power was researched. In 1964, William C. Brown demonstrated a miniature helicopter equipped with a combination antenna and rectifier device called a rectenna. The rectenna converted microwave power into electricity, allowing the helicopter to fly. In principle, the rectenna is capable of very high conversion efficiencies - over 90% in optimal circumstances.Most proposed MPT systems now usually include a phased array microwave transmitter. While these have lower efficiency levels they have the advantage of being electrically steered using no moving parts, and are easier to scale to the necessary levels that a practical MPT system requires.Using microwave power transmission to deliver electricity to communities without having to build cable-based infrastructure is being studied at Grand Bassin on Reunion Island in the Indian Ocean.
due to ROI issues-
It's been proposed to use across the Straits of Gibralta for example- laying cables is very expensive. Beyond a certain point it's cheaper to just waste some of the power than try to deploy a very expensive system due to ROI issues- if it takes longer than 5 years to break even, you're usually not going to, ever, due to compound interest; and then a slightly less efficient system like MPT can win.
How about the ships passing through the straits? Isn't there some serious hazard involved?
A new concept for solid state wireless microwave power transmission is presented. A2.45 GHz rectenna element that was designed for over 85’%0 RF to dc power conversionefficiency has been used to oscillate at 3.3 GIIz with an approximate 10/0 dc to RFconversion efficiency. The RF radiation was obtained from the same circuit by supplyingthe dc output with reverse polarity dc power.
I. IntroductionThe rectenna is a rectifying antenna operating in a receiving mode for reception of microwave power and subsequent conversion to dc by a diode rectifier. However if an IMPATT diode is used to rectify microwave power, the same diode can also operate in the avalanche region to generate and radiate RF power in the same circuit. Thus, the circuit can convert RF to dc and vice versa but not concurrently. The polarity of the dc voltage determines the operating mode. The dc current flow is in the same direction foreither mode of operation.Based upon the conjecture of one of the authors ( Dickinson) , the concept is realized using a rectenna element obtained from the JPL Goldstone microwave power transmission experiment in 1975 . The Goldstone rectenna array consisted of 4,590 elements that delivered up to 34 kW of output dc power from a2.388 Ghz microwave beam. This rectenna array demonstrated an average 82.5% collection and conversion efficiency whereas selected rectenna elements were tested at a 87°/0 conversion efficiencylevel .
I can't believe that such a system could be as good as 50% efficient (and that, I'm sure, can't include the efficiency of the transmitter).
What frequency is used? 'Chicken wire' implies that the wavelength would need to be in the region of 50cm (if you are not to experience some loss in the reflector.
An aperture of 30m would only represent 60 wavelengths - this has a diffraction limit of about 1 degree.
The pattern of the reflector couldn't just be sin(x)/x - it would need to be tailored to suppress sidelobes - just like a good radiotelescope - the lost power problem is directly equivalent to the noise performance for radio astronomy. The actual aperture would need to be considerably oversize, to allow for tailoring of the dish illumination.
Remember that the vast majority of the power has to fall within the area of the receiving array.The straits of Gib are 14km wide - that is a required beamwidth of 0.1 degrees ('Most of' the power not 3dB points) for a 30m receiving array.
The receiving array can't be treated as an independent set of elements - they will interact and, unless you get things right, they will fail to extract all the power from the incident beam - a dipole doesn't take all the power of a passing wave.The figures really don't seem to add up. It's, in fact, far from "simple stuff". I imagine the project needs financial support from someone - don't let it be you!