How efficient is - Efficient
NASDA is already starting trial production of experimental equipment, and "plans to launch the first orbital test satellite around 2010, and put the system into practical use around 2020."
As planned by Mori, the satellite will contain an array of mirrors and focusing lenses to gather sunlight onto a component called a "solar pump" that converts the photons of normal light into several more potent solid state lasers. Waiting down on Earth below will be a giant tank of seawater on a vast artificial island moored under the clear skies of Japan's southern extreme, perhaps near the island of Okinawa. An optical assembly above the tank would concentrate the laser beams again to compensate for atmospheric scattering, and inside that tank NASDA scientists would place the chemical catalyst titanium dioxide, to turn the approximately 10 megawatts of laser energy into a force to shatter H2O into separate hydrogen and oxygen molecules. The oxygen can be sold for industrial use, or released into the atmosphere. The hydrogen can be used as is, or put into new compounds.
"If it is made to react with CO2 in air and methanol can be produced, preservation and transportation is also possible," Mori asserts.
If that plan seems loopy, consider that hydrogen is a solution crying out for it's own solution. The problem with hydrogen is that it's not a fuel as much as it's a battery, a means of storing and transporting energy. Unlike petroleum, it takes more energy to refine hydrogen out of other things, like water and hydrocarbons (including, ironically, petroleum-related products) than it releases when burnt or run through a fuel cell. The most common technique for breaking the chemical bonds that hold hydrogen in larger compounds is electrolysis, but the idea of producing clean cars powered by hydrogen by burning coal at a dirty old power plant has limited appeal.
That leaves Japan's energy planners scrambling for alternatives through a "New Sunshine" program administered by the Ministry of International Trade and Industry. Cleaning up current means of production goes only so far. It would be politically palatable and scientifically viable to generate the needed electricity from green resources like terrestrial solar panels, wind farms, hydroelectric dams, or tidal energy. But none of these options could replace the power density of the roughly 504 billion kilowatt hours of electricity Japan produces from fossil fuels annually. Nor the 61 million tons of petroleum products and 33 million tons of crude oil brought into Chiba each year. Nuclear fission reactors already supply 13 percent of Japan's electricity needs, but like in many developed democracies, many citizens would resist building more. Mastering nuclear fusion remains a goal in Japan, as it does in Europe and the United States, but it too has been ten years away since the 1950s.
Meanwhile, the pressure to break the petroleum addiction in Japan is growing. It is the second largest "Greenhouse Gas" producer among the G-7 circle of the world's most advanced economies. That problem has been contained only by it's decade-long economic fizzle. And energy dependence has been nudging Japan's foreign policy leaders into uncharted territory that smacks of Japan's imperial past to some important neighbors. Just as oil needs served as a justification for expansionism in the earlier twentieth century, it has factored into slightly more elastic interpretations of Japan's non-aggression constitution. This has allowed Japan to play a supportive role in both the Gulf War and the current efforts to destroy the Al Qaeda terrorist network.
And again, it's oil that hydrogen proponents have in their crosshairs. Fuel cells for buildings and homes might make good backup generators, but not daily energy sources.
"Hydrogen can be produced on Earth by water electrolysis. This process may be very efficient (in excess of 80%), but (there is always a catch) this process uses electricity. It therefore does not make much sense to use electricity to generate hydrogen to generate electricity. This does make sense if use of electricity is detached (in time and/or in space) from the generation of electricity. This is the case with electricity from renewable sources (which are inherently intermittent), or back-up power, or use of hydrogen in automobiles," explains Dr. Frano Barbir of the International Association for Hydrogen Energy.
The solar power satellite idea that might prove to be Japan's salvation has American roots. Peter Glaser proposed the idea over thirty years ago, and remains an evangelist for the cause. But what Glaser favors is a system to add electricity to the power grid by gathering sunlight with photovoltaic panels and converting that energy into weak microwaves that can be turned back into electricity on Earth. Several resort islands are already dabbling in microwave radio relay systems to crisscross their tourist paradises with electricity without unsightly power lines. The microwaves are so mild that birds can fly through them without harm. People already receive higher doses of radiation during long flights and other routine activities. The rectifiers in Glaser's plan would be transparent (they need only absorb microwaves, not visible light) so that farms could even be placed below them.
But every layer one adds to an energy system incurs losses. Electrical resistance, scattering, heat, and other factors drain valuable power from the system. Taking power produced in space and transferred through the power grid to electrolyze hydrogen would be less direct than Dr. Mori's concept -- especially if that power also needed to be transmitted over long distances through metal cables. Hydrogen, like natural gas, could be piped over long distances without great loss.
So far, Japanese laboratories have reported an energy efficiency of 16 percent in converting sunshine into hydrogen using visible light. But Mori's laser-oriented team now boasts of a more substantial 30 percent rate. But the satellite solar power boosters note the NASDA effort must still play catch up to match traditional space-based systems. The Space Studies Institute puts the bar at a steep 80 percent.
"We are now confident of being able to deliver to the electrical grid about 90 percent of the energy transmitted from a power satellite since that was demonstrated in real world systems 27 years ago. That is not to say that this is the only possible solution, it is one solution that is known to work. It MAY be possible that there will be other, economically superior, ones developed," writes Dr. Lee Valentine, Executive V.P. of the Princeton, N.J. think tank and space commercialization advocacy group.
"If... the conversion efficiency of the power beam to hydrogen is about 80 percent or so, and assuming the capital costs for the receiving structures are the same then they would be economically equivalent. The reasoning is as follows: The net conversion of transmission beam energy to grid electrical energy is about 90 percent and the conversion efficiency of electrical energy to hydrogen using the best present-day electrolytic cells is also about 90 percent...Ninety percent times 90 percent is about 80 percent, so an 80 percent conversion efficiency of beam energy to hydrogen would then be equivalent to the classic SSP microwave transmission followed by an hydrolysis step to produce hydrogen."
And it's not clear that NASDA's idea conforms to other standards laid out for solar power satellites - that they should be environmentally benign and unusable as a weapon.
But Valentine notes, "There is another, minor, advantage that the photolytic system of hydrogen production has over direct electrical production. One is that the hydrogen production system provides an easy storage method to buffer the power outages caused by Earth's shadow falling on geostationary orbit. Those last up to about 25 minutes and occur daily for a few days twice yearly at the time of the equinoxes."
Tomlin Coggeshall, Vice President of the Hydrogen Energy Center, wasn't familiar with the specifics of the NASDA plan, but thinks that some other innovative idea, like using bacteria to break hydrogen out from compounds, could hold promise too. Nonetheless, Coggeshall wrote in an email that, "If it is feasible, our organization would approve of this method because it produces hydrogen renewably from solar power and water. I believe it is not too far-fetched (but it sounds expensive)."
But the "miserable science" of economics is as real as physics when it comes to erecting new energy infrastructures, and so some folks in the hydrogen crowd are watching the Japanese program skeptically, at least for now.
"It does sound far-fetched. I doubt it would be practical in the near term future, but it does sound interesting for large-scale hydrogen generation in the future," says Barbir.
Valentine doesn't think that day is too far off. The way he sees it, the moon and asteroids are waiting to be turned into power plant hardware, maybe even for hydrogen production to replace crude oil.
"The costs should not boggle the mind. Petroleum infrastructure on the Earth will cost about one trillion dollars over the next decade and will be useless for producing energy when the oil runs out," argues SSI's Valentine. "A similar investment in SSPs built of non-terrestrial materials would give us an inexhaustible energy source and open the universe for settlement, too."
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