Reflectors or inflatable mirrors spread over a vast swath of space, directing solar radiation onto solar panels. These panels convert solar power into either a microwave or a laser, and beam uninterrupted power down to Earth. On Earth, power-receiving stations collect the beam and add it to the electric grid. The two most commonly discussed designs for SBSP are a large, deeper space microwave transmitting satellite and a smaller, nearer laser transmitting satellite.
Designs for microwave transmitting satellites are massive, with solar reflectors spanning up to 3 km and weighing over 80, metric tons.
They would be capable of generating multiple gigawatts of power, enough to power a major U. The estimated cost of launching, assembling and operating a microwave-equipped GEO satellite is in the tens of billions of dollars. It would likely require as many as 40 launches for all necessary materials to reach space.
On Earth, the rectenna used for collecting the microwave beam would be anywhere between 3 and 10 km in diameter, a huge area of land, and a challenge to purchase and develop. Weighing in in at less than 10 metric tons, this satellite is a fraction of the weight of its microwave counterpart. It would be possible to launch the entire self-assembling satellite in a single rocket, drastically reducing the cost and time to production. Also, by using a laser transmitter, the beam will only be about 2 meters in diameter, instead of several km, a drastic and important reduction.
First demonstrated at LLNL in -- and currently still under development there -- this laser would be about the size of a kitchen table, and powerful enough to beam power to Earth at an extremely high efficiency, over 50 percent.
While this satellite is far lighter, cheaper and easier to deploy than its microwave counterpart, serious challenges remain. The idea of high-powered lasers in space could draw on fears of the militarization of space.
This challenge could be remedied by limiting the direction that which the laser system could transmit its power. At its smaller size, there is a correspondingly lower capacity of about 1 to 10 megawatts per satellite. A possible way around this would be to generate solar energy in space. There are many advantages to this. A space-based solar power station could orbit to face the Sun 24 hours a day.
A space solar array could consist of one large structure, or many smaller ones gathered together Credit: Nasa. But one of the key challenges to overcome is how to assemble, launch and deploy such large structures. A single solar power station may have to cover as much as 10 sq km 4. Using lightweight materials will also be critical, as the biggest expense will be the cost of launching the station into space on a rocket. One proposed solution is to develop a swarm of thousands of smaller satellites that will come together and configure to form a single, large solar generator.
In , researchers at the California Institute of Technology outlined designs for a modular power station , consisting of thousands of ultralight solar cell tiles. They also demonstrated a prototype tile weighing just g per square metre, similar to the weight of card. Recently, developments in manufacturing, such as 3D printing, are also being investigated for their potential in space power.
At the University of Liverpool, we are exploring new manufacturing techniques for printing ultralight solar cells on to solar sails. We are exploring how to embed solar cells on sail structures to create large, fuel-free power stations. These methods would enable us to construct the power stations in space. Indeed, it could one day be possible to manufacture and deploy units in space from the International Space Station or the future lunar gateway station that will orbit the Moon.
Such devices could in fact help provide power on the Moon. Solar energy is already used to power spacecraft, but beaming that energy back for use on Earth would become the next level Credit: Nasa.
While we are currently reliant on materials from Earth to build power stations, scientists are also considering using resources from space for manufacturing, such as materials found on the Moon. But one of the major challenges ahead will be getting the power transmitted back to Earth.
The antenna would then convert the waves back into electricity. Researchers led by the Japan Aerospace Exploration Agency have already developed designs and demonstrated an orbiter system which should be able to do this. There is still a lot of work to be done in this field, but the aim is that solar power stations in space will become a reality in the coming decades. Researchers in China have designed a system called Omega , which they aim to have operational by To produce that much power with solar panels on Earth, you would need more than six million of them.
Smaller solar power satellites, like those designed to power lunar rovers , could be operational even sooner. Across the globe, the scientific community is committing time and effort to the development of solar power stations in space.
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