In the never ending search to squeeze energy savings out of old technology, in this case the internal combustion engine, researchers working with Takunori Taira at the Japanese National Institute of Natural Sciences have developed what appears to be a production capable laser sparkplug. Let’s unpack the last four words: Sparkplug – those are the ceramic gizmos in vehicle engines that ignite the fuel (the ‘internal combustion’); they’re critical to the timing of the engine and the efficiency of burning the fuel. Laser sparkplug – conventional sparkplugs make their spark with electricity, a sudden flash that ignites the fuel; a laser sparkplug uses the heat of focused laser light to make the ignition. Production capable – laser sparkplugs are not a new idea, but the difficulty has always been making a version that is reliable, durable, and inexpensive.
First, here are the good points for laser sparkplugs:
- They have no electrodes to corrode (the usual reason conventional sparkplugs fail).
- Lasers can focus the light within the piston cylinder (not at the top like conventional plugs) for more even ignition.
- Laser sparkplugs are faster, causing ignition within nanoseconds compared to milliseconds for standard plugs.
- By a combination of the above and the ability to use more precise timing, laser sparkplugs could make the burning of fuels in piston-driven engines more efficient (with estimates in the 10-15% range).
The difficulties with laser sparkplugs, however, are substantial. The most difficult to overcome has been size. Lasers with enough energy to fire standard fuels (gasoline) were big, difficult to manufacture and unstable. The research team addressed this problem by constructing a laser device from ceramic powders. The ceramic device can withstand the heat of the engine, while providing a ‘tunable’ laser. Technically this was accomplished by building the laser with two yttrium-aluminum-gallium (YAG) segments, one doped with neodymium, the other with chromium. Note the use of the relatively obscure elements. The bonded segments form a laser 9 millimeters wide and 11 millimeters long (e.g. about a half-inch).
Because the laser sparkplug has relatively low power, it must cycle its beam very quickly to build up ignition temperature. The way around this was to cycle the beam in 800 picosecond pulses, and to use dual beams (with a three beam version in the works).
If you think this sounds a might complicated, you could be right. The crucial test, as ever, will be to make a version that is reliable, durable, and inexpensive – that is, can it be manufactured at a commercial scale. For the laser sparkplug this is still an open question, however, the research team is working with a major sparkplug manufacturer (unnamed) and a member company of the Toyota Group. This is called industry buy-in, and it speaks well for the prospects of the laser sparkplug. The question may be: Can commercial viability of a laser sparkplug be achieved before alternative energy engines (as in hybrid or electric) replace internal combustion engines?