It would solve our energy needs overnight. But with huge technological and financial challenges, can space-based solar power ever take off?

“Ex-Nasa scientist seeks visionary billionaire to help change the world.  High risk venture. Return not guaranteed. GSOH a plus.”

John Mankins, the scientist in question, has not yet reached the point of placing a classified ad, but it could soon be an option. The 25-year veteran of the US space agency is the man behind a project called SPS-Alpha, which aims to loft tens of thousands of lightweight, inflatable modules into space. Once there, they will be assembled into a huge bell-shaped structure that will use mirrors to concentrate energy from the sun onto solar panels. The collected energy would then be beamed down to ground stations on Earth using microwaves, providing unlimited, clean energy and overnight reducing our reliance on polluting fossil fuels. The snag? It is unproven technology and he estimates it will take at least $15bn- $20bn to get his project off the ground.

Mankins initially had research funding from an advanced concepts arm at Nasa, but that money dried up in September 2012; hence his continuing search for a benefactor.

“I can’t think of a better solution than to find somebody who is very wealthy, very visionary and willing to make this happen,” he says.

But not everyone shares Mankins’ optimism. Space-based solar power (SBSP) is a topic that divides the scientific world into extremes. On one side are people like Mankins who believe it is the only solution to our ever increasing energy demands, whilst on the other is a sizeable chunk of the scientific community who believe any money put into solar power should remain firmly on the ground.

SBSP has its roots in the 1941 short story Reason, by Isaac Asimov, which depicts a space station – run by robots – collecting energy from the sun to distribute to Earth and other planets. No further thought was given to the idea until the late 1960s, when aerospace engineer Peter Glaser began to investigate its potential. In the following decades, various concepts were put forward but none took off. At the same time Nasa and the US Department of Energy also became involved, funding bits and pieces of research and commissioning reports into its feasibility. Most of these concluded that SBSP was too “high risk” and too costly.

But in recent years, SBSP has once again begun to attract attention with projects emerging in the US, Russia, China, India and Japan, amongst others. All are driven by increasing energy demands, soaring oil and gas prices, a desire to find clean alternatives to fossil fuels and by a burgeoning commercial space industry that promises to lower the cost of entry into space and spur on a host of new industries.

“SBSP is the ultimate energy source for the world and eventually it’s going to replace nearly everything else,” says Ralph Nansen of US-based advocacy group Solar High, with some of the characteristic hyperbole that defines both sides of the SBSP debate. “I don’t think there’s any doubt that within the next century we will be getting the majority of our power from space. It’s just a question of when.”

Nansen is calling for the US government to invest in SBSP research and development as a matter of urgency.

“England dominated the world economy during the industrial revolution because of coal. The United States dominated the world economy after the discovery of oil in Brownsville, Texas in 1901. I’m confident that whoever develops SBSP will have a similarly dominant position in the world economy,” he says.

Nansen, like other SBSP advocates, contends that instead of building huge solar farms on the surface of the Earth, which are at the mercy of fluctuating weather conditions and the cycle of day and night, mankind should fly a little closer to the sun. Specifically, they advocate building solar farms in geostationary orbit 35,800km (22,000 miles) above the Earth’s surface. There, sunlight has an intensity of 1,347 Watts per metre squared – about 30% more intense than on the Earth’s surface, meaning greater electricity production. And depending on its orbital position, an SBSP system could harness direct sunlight almost the entire year round, unlike terrestrial solar farms.

Of course, it is all well and good to collect the solar energy in space, but you still need to get it back to Earth. And since hooking a very, very long cable up to a 5 km (3.1 miles)-wide solar farm in space is not practical, most designs envisage wirelessly transferring the energy back via a concentrated microwave or laser beam to a huge receiving antenna (or “rectenna”) spread over several kilometres on Earth.

‘Kill it off’

All of which sounds simple. But two important issues need to be addressed if SBSP is ever to become reality – concerns about the efficiency of wireless power transmission (WPT) and the sheer cost of such ventures.

Even the most “cursory analysis” of SBSP shows that the advantages gained by moving the solar array into space is “not even nearly comparable” to the additional cost of operating in space and transmitting power back to Earth, says radio scientist Prof William A. Coles of UCSD’s Jacobs School of Engineering. “No space-based power system would survive a cost-benefit analysis,” he says.

But the rise in the commercial space industry has given SBSP advocates new hope for changing the economic equation. A 2011 report by the International Academy of Astronautics (IAA) found that SBSP could be commercially viable within 30 years, driven in part by the rise of private space companies.

Two names crop up with regularity in discussions about SBSP and commercial space: Planetary Resources –the wannabe asteroid mining company launched earlier this year – and SpaceX, the first commercial space firm to send a cargo to the ISS, founded by South African tech billionaire Elon Musk. If just one of these firms – which have already shown they see the potential return on taking on high risk projects in space – can be persuaded to focus its attention on SBSP, the technology has a fighting chance, advocates say.

They point to the falling costs of launching things into space.  It currently costs around $20,000/kg ($10,000/lb) to launch anything into orbit. To send a rig that could be several kilometers across and weigh several thousand tons sets a price tag starting in the billions of dollars. And that is before you have had to assemble the solar panels, an operation that would likely take at least as much skill as assembling the International Space Station – a project that has a price tag of around $100bn.

But Musk has talked openly about how his company plans to build reusable launch vehicles and slash the cost of launching into space to $1,100/kg ($500/lb) or even lower, making the prospect of building giant structures in space seem a less fanciful notion. However, any SBSP firms hoping the entrepreneur may put his financial muscle – as well as his rocket systems – at their disposal may be in for a shock. Musk has previously been hostile towards the idea of SBSP, once saying “stab that bloody thing in the heart” to suggest the idea should be killed off once and for all. SpaceX declined our request for an interview.

Budding entrepreneurs may find more enthusiasm from Planetary Resources co-founder Eric Anderson, who sees its potential, but has no immediate plans to invest in SBSP research or development.

“The only way to get solar energy that is truly plentiful, reliable, and available from anywhere is through SBSP, but the set-up costs are exorbitant,” he says. However, commercially-funded SBSP might take off if it is initially used to deliver power to markets and locations that are “insensitive to price,” such as military positions, disaster scenes, and search and rescue operations, he adds.

Source:BBC