Any long-term base camp on Mars will need to be powered by renewable energy. A proposal developed in response to a competition run by the European Space Agency suggests using a giant kite flown by robots to harness high Martian wind speeds, which could provide enough energy to sustain several astronauts in their everyday work.

Producing and storing renewable energy on Mars is difficult. It is further from the sun than Earth, so it only gets 43 per cent of the sunlight Earth does, making solar power less effective. Much of the technology we use on Earth, such as wind turbines and regular batteries, is far too heavy to reasonably ship to Mars.

To solve these problems, Roland Schmehl at the Delft University of Technology in the Netherlands and his colleagues have proposed using an enormous, lightweight kite with its strings controlled by robots to harness the energy of Martian winds. These are, on average, faster than Earth’s, though the atmosphere isn’t as dense.

“The higher windspeeds and lower density to some degree balance out, but not fully, so we also need to increase the surface area of the kite quite drastically,” says Schmehl. “We have seen something similar with the Ingenuity helicopter that is now flying on Mars – this helicopter has much bigger rotor blades than the small drones that you see here on Earth.”

Read more: NASA’s Ingenuity helicopter has made its fourth and furthest flight

The kite that he and his team proposed is similar to some that are under development to capture wind power on Earth, but bigger, with a surface area of 50 square metres. As it climbs higher through the sky, more of the cable with which it is tethered to the ground spools out from a large bobbin-like drum, and energy can be harnessed through the rotation of this drum. Eventually the kite’s height must be reduced and it is reeled in again. This uses power – but not as much as was generated as the kite climbed higher, say the researchers, so the end result is an energy generating system.

To provide enough power to sustain a Mars base, this system would be supplemented with 70 square metres of solar cells. The researchers propose that the energy produced by those two methods could be stored so that the astronauts could have steady power at night and in different seasons. A short-term energy storage solution would be offered by lithium-sulphur batteries, and a longer term storage system would be achieved by compressing carbon dioxide gas from Mars’s atmosphere in underground caverns – this gas could later by decompressed to reclaim the stored energy.

This whole system could provide about 127 megawatt-hours of energy per year – equivalent to the power produced by about 75 barrels of oil. “If we relate it to Earth, it would power about 20 households here in the Netherlands or about five households in the US,” says Schmehl. “[A Mars base camp] is basically one household, four to five astronauts with a small lab.”