Wireless Power Transfer using Microwaves

This was the first time anyone has managed to send a high output of nearly two kilowatts of electric power via microwaves to a small target, using a delicate directivity control device .Japanese scientists have succeeded in transmitting energy wirelessly, in a key step that could one day make solar power generation in space a possibility. Solar power generation in space has many advantages over its Earth-based cousin, notably the permanent availability of energy, regardless of weather or time of day. While man-made satellites, such as the International Space Station, have long since been able to use the solar energy that washes over them from the sun, getting that power down to Earth where people can use it has been the thing of science fiction. But the Japanese research offers the possibility that humans will one day be able to farm an inexhaustible source of energy in space. The idea, said the JAXA spokesman, would be for microwave-transmitting solar satellites—which would have sunlight-gathering panels and antennae—to be set up about 36,000 kilometres (22,300 miles) from the earth. But it could take decades before we see practical application of the technology—maybe in the 2040s or later. There are a number of challenges to overcome, such as how to send huge structures into space, how to construct them and how to maintain them.

Phasers Locked on Target: In a test of space-based solar power, Mitsubishi Heavy Industries and JAXA sent 10 kilowatts 500 meters by microwave.

The obvious question here is one of efficiency: being able to transmit power is great, but if you lose most of it along the way, will the overall system ever reach commercial viability? At this point, the conversion system (solar to DC to microwave to DC to AC) is about 80 percent efficient, but that excludes loss of energy in transit. Within the next five years or so, Mitsubishi is hoping that they’ll be able to use this system for short range high power delivery (like electric car charging), and medium range delivery of small amounts of power (like powering warning lights on transmission towers). Meanwhile, JAXA is planning on testing the technology in space by 2018, with a small satellite transmitting several kilowatts from low Earth orbit to a microwave receiver on the ground. JAXA hopes to have a 100 kW satellite in orbit by 2021, and a 200 MW version by 2028. By 2031, if everything goes well, a 1 gigawatt commercial pilot plant will be in operation, with a full on commercial space-based power industry to kick off with one launch per year starting in 2037.

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