Where the Sun Does Shine: Space-Based Solar Power Globally

A Japanese cartoon of their SBSP concept. Image courtesy http://www.treehugger.com/solar-technology/japan-space-solar-plans-of-laser-beams-and-solar-streams.html

SBSP As Disaster Relief and Third-World Electrification

On Tuesday night, April 1st, 2014, a massive earthquake registering at 8.2 magnitude struck in the Pacific Ocean off the coast of Northern Chile, sending deadly tsunami waves racing toward the coast, and leaving the nation in a state of emergency. Only in the early hours of the disaster thus far, it’s not yet clear what the scope of the damage is.

Meanwhile, on the other side of the globe, the residents whose homes were affected by the nuclear reactor meltdown in Fukushima, Japan in 2011 are only just now being allowed to return to their homes, the decontamination of the site finally completed, despite fear that dangerous radiation from the disaster still lingers. Nuclear power is one renewable option for weaning our world off fossil fuels, but clearly nuclear is not without its major faults.

All the while, the world still depends overwhelmingly on fossil fuels to power our lives, both for the everyday and in case of disasters like the ones in Chile and Fukushima. Not only do these fossil fuels spew carbon into the air, damaging our planet’s fragile climate and threatening all life on Earth, but our dependency on fossil fuels also has poor implications in cases of disaster. Even if aid workers make it to disaster sites, they might not have the power they need to run hospitals and government offices if the grid is down with infrastructure down.

One possible solution to our energy crisis is space-based solar power, and its potential for use in disaster relief efforts is staggering. With the touch of a button here on Earth, technicians could shift the satellites beaming the sun power down to earth, focusing extra power to the locations on Earth where energy is most needed.

In his TEDx Talk from 2009, Space Energy CEO Peter Sage says that SBSP technology has “the ability to transfer energy on demand anywhere on Earth, in real time as it’s needed 24 hours a day – nothing else can do that.” Space Energy was founded by the British Sage, but is based in the United Arab Emirates and boasts an international group of senior staff.

Yasuyuki Fukumuro, head of the Space Solar Power Systems (SSPS) project at JAXA (Japan Aerospace Exploration Agency – the Japanese equivalent of NASA), agreed in an interview from 2010: “For example, if a blackout occurs due to a natural disaster, a thin, portable rectenna can be unfolded and deployed to receive microwaves from space, which can be converted into electrical energy.”

This kind of portability also has implications for bringing electricity to third world countries unable to connect to the grid; said Peter Sage in the same TEDx Talk: “World governments, NGOs all understand that one of the fastest ways to take people out of poverty in the developing world is to give them access to electricity.” Space-based solar, he says, “could enable rural electrification like no other form of technology.”

A Question of Efficiency

There is not a difference in actual efficiency between SBSP and ground-based solar looking solely at the technical solar side; the same technology to convert sunlight into usable energy is at work. The world record for solar cell efficiency is currently 44.7 percent efficient, with the average solar cells in use being closer to 20 percent. However, about 30 percent of sunlight that reaches Earth never makes it to the ground, unable to penetrate the atmosphere (protecting us from harmful UV rays and cosmic radiation). In space, all that extra sunlight that can never reach a ground-based solar facility can be harvested.

Think of it this way: although both SBSP and ground-based solar will use the same solar cells, SBSP is starting with a third more raw energy.

Still, that energy has to get to the ground somehow. The orbital solar satellite would beam the sun’s energy to receiving stations on Earth, in one of two ways: by microwave beam or by laser beam. When sunlight is converted to microwave or laser beam and then back to DC electricity for use on the electrical grid, some energy is lost – but even with these losses SBSP would still provide far more energy than a ground-based facility using the same solar cells could produce.

With a microwave beam, the satellite could be in geosynchronous orbit (GEO), 35,000 km above the Earth. At such great heights, the full power of the sun could be harnessed. On the way down though, in converting the microwave back to DC electricity through a device called a rectenna (technology that already exists), a receiving station on the order of a kilometer or two would be necessary to gather the wide radius of the beam. The process of converting the microwave beam back into usable electricity through the rectenna is currently about 70 percent efficient. With a microwave transmission system in GEO, the cost between launch and the necessary construction to take place is currently estimated at $20 billion.

The other option, a laser beam transmission system, is far cheaper – a mere $500 million according to the Livermore Lawrence National Laboratory operated by the United States Department of Energy. This reduced cost is due to a lower orbit and thus lower launch costs, the design being lighter, and the receiving station only needing to be about two meters (a thousandth of the size of the microwave receiver) due to the fact that a laser beam could be more narrowly focused than to a microwave beam.

A laser beam transmission system concept for SBSP. Image courtesy Graham Murdoch / http://www.popsci.com/technology/article/2011-06/satellites-could-gather-energy-sun-and-beam-it-down-earth

At around half the price of the microwave option, lasers start to sound very exciting, but that rosier monetary price tag comes at a different cost – that of energy loss. A laser beam system would live at Low Earth Orbit (LEO), 400 km above Earth, and would thus still be subject to some atmospheric blocking of the full power of the sun. Additionally, a laser beam would not be able to penetrate clouds, preventing power from reaching the receiving station. Finally, a laser would be about 50 percent efficient in converting the laser beam to usable electricity.

Either way, the task of converting sunlight to microwaves or lasers and then to usable energy is a fairly minor hurdle; the major challenge facing SBSP remains the sheer expense associated with construction and implementation. There’s also no need to worry about laser beams or microwaves beaming down to Earth as a safety hazard – every proposal for SBSP demonstrates that the intensity of either a microwave or laser beam would only around 200 Watts/m2 – that’s just  20-25% the intensity of mid-day sun at the equator – and therefore posing no threat to humans, animals, plants or even high-flying planes.

Global Efforts Today in Space-Based Solar

Currently, in addition to the United States efforts, several countries are seriously pursuing SBSP, with Japan as leader among all nations. The other major players on the world stage in SBSP are Russia, European collaborations, and the partnership of India and China. In 2012, former Indian president APJ Abdul Kalam, who is also an aeronautical engineer, offered China a joint collaboration with India to develop SBSP for the two countries.

Japan’s space agency, JAXA, has ongoing plans to launch their Space Solar Power System by 2030. This station would generate the equivalent energy of a medium-sized nuclear plant. Rather than stuck in the study phase, like the U.S. and other countries, head of the program at JAXA Yasuyuki Fukumuro said in a 2010 interview “we have just moved from the study phase to the technology demonstration phase.”

In the past four years, more and more testing has been done, with prototypes for the Japanese design being tested. In September 2013, JAXA Senior Researcher told a website called Kyoto-Shisaku Net, “We are developing a new prototype for capturing solar power using lightweight solar mirrors.” Using mirrors to focus sunlight to satellites is JAXA’s goal, though they have not yet decided whether to use laser or microwave beams to get the power to the ground.

Even outside governmental efforts, Japanese company Mitsubishi Electric presented their proposal for SOLARBIRD, which would entail dozens of small satellites, whose combined generating capacity could produce the required power supply.

Many nations are already on board, clearly committed to SBSP. With global cooperation in development, launch, and operation of a space-based solar concept, energy use across the world could be reborn, giving Earth a chance in the climate change struggle and providing clean energy for the billions inhabitants of the planet – at least for the next four billion years the sun still has to shine.

Leave a Reply