Researchers at a US university say they have beamed energy from an orbiting satellite to a detector on Earth, proving that harvesting energy from solar panels in space is technically possible.
The eggheads at the California Institute of Technology, aka Caltech, said they used a satellite launched into orbit in January to demonstrate the ability to wirelessly transmit energy into space and also transmit detectable energy to Earth.
Known as the Space Solar Power Demonstrator (SSPD-1), the satellite is the first technology prototype from Caltech’s Space Solar Power Project (SSPP) to enter orbit.
SSPP was founded about ten years ago, with the aim of collecting solar energy in space and transmitting it to receivers on the ground, such as The register previously reported.
All electromagnetic radiation carries energy, which can be seen in powered radios by the received radio signal itself. The trick is to be able to direct the energy to a desired target instead of radiating it in all directions.
The commercial end of the SSPD-1 satellite is the Microwave Array for Power-transfer Low-orbit Experiment (MAPLE), a series of flexible, lightweight microwave power transmitters driven by custom electronic chips to direct a beam of energy wherever needed .
An interaction of constructive and destructive interference between individual transmitters directs the beam, such that a bank of power systems can shift the focus and direction of the energy it radiates. This is similar to the technique used in military phased-array radar systems to scan the horizon without physically moving the antenna.
In this case, the transmitter array uses precise timing control to focus power to the desired location using the coherent addition of electromagnetic waves, according to Caltech, so that most of the transmitted energy is focused on the desired location of the target. .
However, in this case, the energy didn’t have to travel very far. MAPLE includes two receiver arrays approximately 12 inches apart from the transmitter to receive the energy. When power is received, it turns on some LEDs to demonstrate system operation.
This isn’t much of a test. MAPLE also features a small window on the satellite through which the array can radiate energy. This was used to transmit a test signal to a receiver on the roof of a laboratory on the Caltech campus in Pasadena.
While this provided only a small amount of power, Ali Hajimiri, Bren’s electrical engineering professor and co-director of SSPP, claimed the result for the first time.
“As far as we know, no one has ever demonstrated wireless energy transfer in space even with expensive rigid structures. We are doing it with flexible, lightweight structures and our integrated circuits,” he said in a statement.
“Through the experiments we’ve conducted so far, we’ve received confirmation that MAPLE can successfully beam energy to receivers in space. We’ve also been able to program the array to direct its energy towards Earth, which we’ve detected here at Caltech We’ve obviously had it tested on Earth, but now we know it can survive space travel and operate there.”
The satellite has other experimental hardware besides MAPLE. Deployable on-Orbit ultraLight Composite Experiment (DOLCE) is designed to test the deployment mechanisms of a lightweight, foldable structure to support solar panels, while ALBA is a collection of 32 different types of photovoltaic cells. They are arranged to evaluate which types work best in the space.
Looking to the future, the SSPP project said it aims to deploy a constellation of satellites to harvest sunlight and transmit microwave power wherever it’s needed, including locations that lack reliable access to power. This assumes that the equipment achieves sufficient efficiency to make the effort worthwhile.
“No power transmission infrastructure on the ground will be needed to receive this power. This means we can send power to remote regions and areas devastated by war or natural disaster,” said Hajimiri.
The idea behind solar energy from space is that energy is always available without being subject to day and night cycles, seasons and cloud cover, says the SSPP, potentially producing eight times more energy than the solar panels on the ground.
However, a previous study by the European Space Agency (ESA) of solar harvesting satellites calculated that they would need to be somewhere in the region of a kilometer or more in diameter to transmit about 2 GW of power to the surface which would correspond to the production of a nuclear power plant.
It seems that the SSPP will aim for more modest goals, at least for now.
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