CARS that run on hydrogen-powered fuel cells are squeaky-clean dream
machines. The trouble is, the only way to make hydrogen at the moment is to
split water with electrical energy from polluting power stations. Now a team in
Japan has found a new way of doing the job: use a satellite to convert solar
energy into a powerful laser beam that鈥檚 capable of busting the water
molecule.
Japan鈥檚 National Space Development Agency (NASDA) and the Institute for Laser
Technology (ILT) in Tokyo have joined forces to test out the feasibility of a
space-based laser. Outlandish as it sounds, they have even planned a switch-on
date for 2020.
Here鈥檚 the plan. A series of mirrors and lenses inside the satellite will
concentrate solar energy. Another optical system, called a solar pump, will
convert the light into a powerful laser beam.
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This beam will be targeted at a reactor on Earth containing particles of
titanium dioxide, suspended in water. The oxide particles act as a catalyst that
enables the energy from the light to split water molecules into hydrogen and
oxygen. Collect the hydrogen and you can use it to run the fuel cells.
Earth-based solar pumps can鈥檛 collect enough energy to turn sunlight into
laser beams because clouds and moisture get in the way of the Sun鈥檚 rays. A
space laser wouldn鈥檛 encounter these problems, and the Japanese team say their
system will have a fairly respectable efficiency of around 30 per cent. Some
energy will be lost in the conversion from sunlight to laser light, and also as
the laser beam travels back to Earth, if it travels through cloudy moist skies.
But the researchers say they will position the collection station away from
cloudy or polluted areas.
鈥淥ur idea is to build the conversion plant on a megafloat鈥攁n artificial
island made of large steel pontoons,鈥� says Masahiro Mori of NASDA. 鈥淚t would be
anchored near islands in the south of Japan where skies are clearer. We can then
use seawater as a raw material.鈥�
Mori envisions projecting several laser beams from a single satellite with a
combined power of around 10 megawatts. He estimates that the system should be
able to generate fuel equivalent to a litre of petrol for around 9 pence.
The first research phase will look at ways of generating the laser light and
beaming it back to Earth in a controlled way. NASDA and ILT hope to have the
first experimental satellite in space by 2010 and a working model by 2020.
But it鈥檚 not going to be easy, warns Geoffrey Landis, a space scientist at
NASA鈥檚 Glenn Research Center in Ohio鈥攁nd a sci-fi author. 鈥淭his project
will require some significant technical work to become feasible,鈥� he warns.
Splitting water is very inefficient and it would take a lot of research to turn
it into a practical means of generating energy, he explains. 鈥淣evertheless, it
does sound like a fascinating research project.鈥�
