I may have more in common with Marf the Dragon Master than I care to admit. Earlier this month, California energy regulators approved the nation’s first utility contract for a space-based solar power plant. I thought of Sim City. In the game, metropolises receive energy from microwave power plants. However, distracted players can find their downtowns obliterated from errant microwave beams. Marf posted a discussion thread, “Sim City Microwave Power Plant“, reacting exactly as I did to this space power announcement.
In “California gives green light for space-based solar“, CNET reports that the California Public Utilities Commission approved a petition by San Francisco, CA based utility Pacific Gas & Electric (PG&E) to purchase 1,700 gigawatt-hours per year for 15 years starting in June 2016 from space solar power startup Solaren of Manhattan Beach, CA.
Space-based solar power has been evaluated since the 1960’s for its three key advantages over terrestrial photovoltaic plants. First, compared to diurnal ground-based installations orbital solar arrays enjoy nearly 100% capacity factor. Second, with no atmosphere or weather to absorb or deflect photons, space solar energy density is higher than on the ground. Third, land use for megawatt-scale plants is much smaller. Despite these benefits, orbiting a solar power plant carries prohibitive costs, making the approach a non-starter.
Solaren’s key innovation to overcome high launch cost is dramatic weight reduction. According to the company’s patent, a 1-kilometer-diameter orbital inflatable Mylar mirror will collect and concentrate sunlight onto a smaller mirror. The energy is then focused onto photovoltaic modules. According to a Grist.org article “California utility bets on space-based solar power“, instead of being tethered together, the components will float free in space, kept in alignment by small station-keeping rockets.
The New York Times reports in “Solar plant in space gets go-ahead” that Solaren’s proposed 200-megawatt orbiting plant will convert solar energy to radio waves, which will be beamed to a ground station near Fresno, CA. On the ground, the radio waves are converted into electricity for power grid distribution.
Could this technology turn Fresno into a fried Sim City? Speaking with the San Francisco Chronicle (see “California’s new power source a solar farm“), Solaren’s director of energy services, Cal Boerman, said that the energy beam was too diffuse to cause harm. “This isn’t a laser death ray,” Boerman told the Chronicle.
On page 26 of its 2007 report, “Space‐Based Solar Power as an Opportunity for Strategic Security“, the National Security Space Office reports that microwaves “can be beamed at densities substantially lower than that of sunlight and still deliver more energy per area of land usage than terrestrial solar energy.” Moreover, “low energy density and choice of wavelength also means that biological effects are likely extremely small.”
Despite these assurances from both the federal government and Solaren, a space microwave power safety debate is ongoing in the comments section of Kevin Bullis’s “Startup to beam power from space” post at his Potential Energy Blog within MIT’s Technology Review site. Unresolved questions about microwave beam frequency and rate of dissipation are confounding energy density calculations.
Convincing the public of safe operation is one among many headaches Solaren must overcome to realize space-based solar power. According to an MSNBC article “PG&E makes deal for space solar power,” Solaren CEO Gary Spirnak said his company currently employs 10 aerospace industry professionals hailing from Hughes Aircraft, Boeing, Lockheed Martin, and the U.S. Air Force. The company must immediately increase its workforce to 100 to stay on track for 2016 power delivery. On top of a tenfold workforce cost increase, Kevin Bullis of Technology Review estimates that the company must raise billions of dollars to construct their orbital plant.
Regulation will also be an issue. As with so many new ventures, the law has not caught up with Solaren’s technology. Clearances from the Federal Aviation Administration and the Federal Communications Commission along with federal and state safety officials are minimum requirements for deployment. Moreover, California regulators already decided that PG&E could not count the project toward its state-mandated renewable energy quota unless specific milestones were met.
Most importantly, it still remains unclear whether the economics of space-based solar are viable. While the underlying utility contract was approved, the rate PG&E agreed to pay Solaren for the produced electricity remains confidential. Compared to terrestrial power plants, substantially more capital must be invested to orbit the Solaren station, yet to achieve competitive economic viability, the resulting power cannot exceed the cost of terrestrial power. The 2007 National Security Space Office report indicates that even at a rate of $1 to $2 per kilowatt-hour, an order of magnitude higher than the cost of terrestrial power, space-based solar energy is not economically viable.
I suppose Marf the Dragon Master and I will simply need to continue entertaining ourselves with Sim City awaiting 2016 to see whether Solaren’s gamble pays dividends.