Space-Based Solar Power Comes Closer to Reality

This concept of a solar power satellite provided by NASA shows the assembly of a microwave transmission antenna.

Industry dares to go where governments will not.

The decades-long dream of harnessing the sun’s power in orbit as a source of clean, renewable energy on Earth may lie just over the horizon. Yet, unlike traditional space efforts, this concept may come to fruition as a result of commercial—not government—commitment.

Government agencies, both in the United States and internationally, have touted the benefits of such programs. They include the U.S. Defense Department, Energy Department, NASA and the European Space Agency. However, the majority of funding for these efforts is coming directly from industry.

The concept behind the space-based solar power (SBSP) programs is to place very large solar arrays into continuously and intensely sunlit Earth orbit, collect gigawatts of electrical energy and beam it to Earth. The solar energy received on the surface could be converted into manufactured synthetic hydrocarbon fuels or could be used either as base load power via direct connection to the existing electrical grid or as low-intensity broadcast power beamed directly to consumers. Satellites could deliver energy around the clock, virtually all year long, because the sun’s rays are up to 10 times stronger in space and there is no weather-related interference or loss of sunlight at night.

In the United States, NASA, the Department of Energy and the Defense Department all have studied SBSP. NASA and the Energy Department collectively have spent $80 million over three decades in erratic efforts to study the concept. By comparison, the U.S. government has spent about $21 billion over the last 50 years continuously pursuing nuclear fusion.

The most recent study, done in 2007 by the Defense Department’s National Security Space Office, states that preventing resource conflicts in the face of increasing global populations and demands is a high priority. A single kilometerwide band of geosynchronous Earth orbit experiences enough solar flux in one year to nearly equal the amount of energy contained within all known recoverable conventional oil reserves on Earth today, according to the Defense Department study. That amount of power offers enormous potential for energy security, economic development, improved environmental stewardship, advancement of general space faring and overall national security for those nations that possess an SBSP capability, the Defense Department study explains.

The various government reports and recommendations have not yet led to significant action, according to industry sources. One reason policy makers elected not to pursue development is that other forms of energy were relatively less expensive; however, recent world events—including the cost of oil and the stability of oil producing nations—have changed those calculations. The Japan Aerospace Exploration Agency is one exception to government funding of SBSP. It has committed to developing the technology to provide electrical power from space in the 2030s.

The lack of government support has not stopped companies from developing SBSP technologies. “Space solar is really a no-man’s land in that the Department of Energy is interested in generating electricity, but they don’t do anything in space. The Department of Defense doesn’t generate electricity, and NASA has no funding right now,” says Cal Boerman, vice president of sales and electricity delivery for Solaren, one of the companies investing in SBSP technology. “A lot of people out there are hoping for government funding, but we have not sought government funding, and we’re not seeking it,” he adds.

Solaren was formed in 2001 by a team of space scientists and satellite engineers with extensive experience in the U.S. Air Force and with major aerospace and defense companies. The company’s goal is to deliver 200 megawatts of base load space solar power by 2016. Solaren executives believe they are the first company to receive an actual contract to provide electrical power from satellites. The company announced an agreement in 2009 with Pacific Gas and Electric (PG&E), a major utility in northern California.

Under the contract, the amount of which has not been disclosed, Solaren is required to provide 200 megawatts of clean, renewable power over a 15-year period. Solaren is paid only if it delivers. PG&E is not funding Solaren’s current technology development efforts. For technology development funding, Solaren executives are turning to qualified investors. The company may opt to provide an initial public stock offering once it has a satellite in orbit and is able to demonstrate that it works. Boerman concedes that finding investors in today’s economic climate is hard work, but he says the company is succeeding well enough to meet its 2016 deadline.

Solaren’s patented solution includes satellites using solar cells to convert the sun’s energy into electricity to power high-efficiency generators onboard the satellite. The generators convert the electricity into radio frequency energy and transmit it to a ground receive station, which then converts the energy into direct current electricity and uses the local power grid for transmission to the PG&E delivery point.

Some experts—even some proponents of SBSP—believe achieving such a capability will cost tens of billions of dollars and will require satellites larger than the International Space Station, too large to be launched by conventional means and possibly requiring construction by robots in space.  However, Boerman contends that modern-day communications satellites already use solar panels to collect power, convert it to radio frequency energy and transmit it to Earth. Those satellites have been in use for more than four decades. Solaren will use the same basic technology and build a much larger satellite, one that might have to be constructed in pieces, launched and then docked together in space using traditional, proven docking methods.

This NASA photo depicts the energy emanating from the sun. Companies around the world are racing to capture some of that power with orbiting satellites to provide electricity on Earth.

“We describe it as more of an engineering problem than a technology development problem. The technology is pretty much there. We need to build a satellite that’s larger than current communications satellites. We don’t need to invent solar cells, antennas or radio frequency transmission technologies. All that’s been done. We just need to do it on a bigger scale,” Boerman says. He predicts that the satellite antenna could be a kilometer in diameter and that the ground receiving station also likely will be a kilometer or more in diameter. “It’s large, but it’s do-able. It’s just a matter of building it. Today, you could buy 15-kilowatt capable satellites. We’re transmitting megawatts instead of kilowatts, but it’s the same technology, the same concept.”

EADS Astrium, a major spacecraft manufacturer headquartered in Paris, France, is taking a different approach. The company intends to beam energy from space satellites using high-powered infrared lasers rather than radio frequency signals. EADS vowed earlier this year to put its own solar-collecting demonstration satellite into orbit by decade’s end.

That satellite will beam energy toward a mobile receiver 20 to 30 meters in diameter rather than to a large, fixed receiving station. The receiver will be specifically tuned to the laser’s wavelength, which will be eye-safe, and the power on the ground will be about as warm as it feels when walking in normal sunshine.

The mobile concept has commercial appeal and could be used for disaster management, but it also offers a military advantage for forces in remote areas, explains Matthew Perren, Astrium innovation manager. One drawback, he volunteers, is that the laser will not be effective on foul-weather days. “What you have to do is take a global perspective. From the satellite’s point of view, it can point anywhere, and I guarantee there will be receivers not in cloud that will need that power. It won’t be available to every receiver because of cloud cover, but from a global perspective, we are always able to provide energy to the ground.”

If the demonstration proves successful, the company will work toward its long-term vision of putting larger satellites in orbit and providing energy directly to the electrical grid. Astrium is investing its own money and is seeking partners to share the investment. “We’re not going to do this in isolation. We’re actively seeking technical partners and investment partners to push this forward. We’ve had lots of interest from around the world, and that door is still open,” Perren states.

Meanwhile, PowerSat Corporation, Everett, Washington, has patented a new technology similar to cloud computing in space. The company’s BrightStar technology allows individual power satellites to form a wireless power transmission beam without being connected physically to each other, a process company officials dub “electronic coupling.” The technology eliminates the need for a single satellite to handle large gigawatt levels of power. Instead, hundreds of smaller satellites coupled together could transmit a single, powerful beam. In addition, if any individual satellite fails, it can be replaced without significantly affecting the overall performance of the entire system.

PowerSat Corporation, a subsidiary of PowerSat International, which is based in Gibraltar, also has patented a novel spacecraft propellant system known as Solar Power Orbital Transfer. The system reportedly propels a spacecraft into geosynchronous orbit using electronic thrusters powered by the same solar array that later is used for wireless power transmission. That eliminates the need to use chemical propulsion and reduces satellite weight by nearly 70 percent, which in turn reduces launch costs. Using the orbital transfer system, satellites can be launched into low orbit via rockets, deploy their solar-powered electronic thrusters and then fly themselves into geosynchronous orbit.

As its competitors elsewhere, Space Energy, a Swiss company, intends to launch a demonstration satellite before placing larger satellites in orbit. The demonstrator will be placed in low Earth orbit and will be designed to prove the viability of orbit-to-ground wireless power transmission and space robot assembly capabilities.

Peter Glaser, an American scientist, is widely credited with introducing the concept of SBSP generation in 1968, the same year astronauts first orbited the moon. The first significant U.S. effort occurred in the 1970s where scientific feasibility of the concept was established and a design was proposed, but at the time, the architecture and technology levels could not support an economic case for development relative to other lower-cost energy alternatives. A NASA study completed in 1997 re-examined the concept and found that the technologies needed to satisfy SBSP development were converging quickly. The National Research Council validated that report, but no government support resulted from this research.

Since the initial investigation of this technology more than three decades ago, oil prices have jumped from $15 per barrel to about $80. In addition to global concerns over climate change, U.S. and allied energy source security is now under threat from those seeking to destabilize or control global energy markets, and increased energy demand by emerging global economies is leading to competition for the resources. U.S. national security strategy acknowledges that many nations are too dependent on foreign oil, often imported from unstable portions of the world. The strategy seeks to remedy the problem by accelerating the deployment of clean technologies to enhance energy security, reduce poverty and reduce pollution in a way that will ignite an era of global growth through free markets and free trade. 

While governments hesitate, industry experts say this is the time to move forward. “This is important stuff—green energy, limitless energy,” Perren says.

WEB RESOURCES
National Space Society: www.nss.org/settlement/ssp
National Security Space Office study: www.nss.org/settlement/ssp/library/nsso.htm