NASA backs solar power satellite

Will the US win the space race to beam solar energy back to Earth?

A Californian technology consultancy has joined the race to launch a solar power satellite [SPS] designed to generate solar energy in space and beam it down to earth.

Artemis Innovation Management Solutions has recruited former NASA engineer John Mankins to develop a prototype, with seed funding from NASA. Mankins has already come up with the concept, called SPS-ALPHA, for ‘Solar Power Satellite via Arbitrarily Large Phase Array’. Which, very basically, means building huge platforms in space comprising concentrated photovoltaic [PV] panels and systems for wireless power transmission.

Mankins is confident about the technology; it’s the cost that worries him. Of course, it all depends on the scale. Even a small prototype, say 10-20kW, will cost a few tens of millions of dollars to build, but could be done in just two to three years. With increasing size, the cost per kW reduces – but the total bill would still be sizeable, says Mankins. He estimates the cost of a large pilot plant, in the region of 10-20MW (a thousand times larger than the prototype) could be 100 times more than the smaller version.

The total surface area of a full-size SPS plant will be vast. A 1MW system, about 25% efficient over the surface as a whole, would entail a total area of almost 3 million square metres. Building something of this scale brings with it additional challenges, such as in-space transportation, and in-space assembly and construction – and would take eight to 10 years.

But the economics are beginning to look more promising, Mankins says, with progress in the efficiency of critical components, such as PV and other solid state electronics. Multi-junction solar cells, which have been finding their feet – here on Earth – in concentrated PV systems, are made by several companies, most of whom have roadmaps for pushing up their efficiencies from 30-40% today to as much as 50% in the next few years. Further progress in computing, materials and robotics mean SPS concepts by Artemis and others could be feasible in the next 10 years.

The race is on. Already, Californian start-up Solaren has a contract under negotiation with Pacific Gas and Electric to deliver 200MW of power for at least 15 years, starting in 2016. And Japan Aerospace Exploration Agency [JAXA] is also working with the private sector to launch a test version of its SPS in 2020, a project that will cost over $20 billion.

Once a pilot plant has been demonstrated, the next challenge is industrial scale-up of SPS manufacturing and launch. Mankins suggests it will take perhaps 40 years for SPS to make a significant contribution to global energy needs. “This is exactly the same type of timeline that wind and [terrestrial] solar power have followed, looking back some 30 years to the early development of these technologies”, he says. – Sara Ver Bruggen