Sparks

Hydrogen engines boost by lasers

 By Robin Wylie

Hydrogen, the most abundant element in the universe, is a promising zero-emissions fuel. In theory, the only emission from burning hydrogen is water, however inefficient ignition can lead to the release of harmful pollutants, such as CO2, carbon monoxide and nitrous oxides. A solution to this problem is to use a high-powered laser to ignite the hydrogen. In a new study, Indian scientists developed a new kind of laser-ignition system for hydrogen. It used an ultraviolet laser, and was able to burn the hydrogen very efficiently and cleanly, while producing “inconsequential” amounts of polluting carbon compounds. This study sets the scene for greener, more efficient hydrogen power systems in the future…

Humanity’s greatest challenge in the coming century can be summed up in three words: adopt clean fuel. It’s an easy phrase to say, but as our continued reliance on fossil fuel shows, it’s much harder to achieve in practice.

Luckily though, one of the best candidates to bring about a carbon-neutral future also happens to be the most abundant element in the universe — hydrogen (H2). When this gas is burned, the only major byproduct is water. As well as being greener than fossil fuels, hydrogen fuel is also safer. Due to its extremely low density, hydrogen rapidly floats away when released (for example during an automobile accident) reducing the chances of a fireball; hydrocarbon fuels on the other hand, being denser, tend to stick near the ground.

Another benefit of hydrogen as a fuel is that it’s around ten times easier to ignite than gaseous hydrocarbons, making it more fuel efficient. But therein lies a problem.

As promising as hydrogen is, it’s not a perfect fuel source. While it’s 100% green in theory, in practice the oils that are required in hydrogen engines cause a small amount of carbon (compounds like carbon dioxide, carbon monoxide and hydrocarbons) to be released when hydrogen is burned. Compared to a petrol engine, the amount of carbon released by a hydrogen engine is insignificant. However, since the presence of carbon compounds reduces an engine’s efficiency, there’s still an important incentive to cut them out.

One way to reduce the carbon output of hydrogen engines is by using so-called “laser ignition.” Many hydrogen engines use a spark plug to ignite their fuel, much like conventional petrol engines. Laser-igniting engines, however, use a pulse of laser light to ignite the fuel by creating a high-intensity plasma. This technique is more efficient, and cuts down on the unwanted carbon produced during hydrogen combustion.

A laser pointer (Imagine by Andrea Pacelli)

Laser-igniting hydrogen engines have been built before. But researchers from the Indian Institute of Technology in Kanpur have just developed what might be the cleanest-burning hydrogen engine yet. In a study published in December, the team converted an existing diesel engine into a hydrogen engine by fitting it with a customized infrared laser spark plug.

The engine performed remarkably. The researchers found “almost zero” emissions of carbon monoxide, while emissions of carbon dioxide and hydrocarbons were low enough to be considered “inconsequential,” they say.

Reducing the carbon footprint of hydrogen engines is not the main barrier to their use. Even in hydrogen engines that use conventional (non-laser) ignition systems, the amount of carbon compounds produced are inconsequential compared to hydrocarbon-powered engines. But advances like this one from India are still important. The more efficient hydrogen engines become, the more likely they will be to be implemented on a wider scale. A small step, but a good one.

about the author
Robin Wylie
Freelance earth/space science journalist. Currently finishing off a PhD in volcanology at University College London.