Electric cars and hydrogen
In our series on sustainable energy, we move on to the question of how hydrogen may be used as an adjunct to engines that don’t run on fuel that has to be mined from the ground.
Hydrogen is well known as the lighter-than-air gas that fills balloons and makes them rush skyward if you let go of the string, but its much more common presence in our lives is in combination with oxygen as H2O – in other words, water. It’s the lightest and most abundant chemical element, and when you look beyond our own somewhat mundane use of it, you’re into some startling facts. The stars that we see in the night sky mainly composed of hydrogen in its plasma state, when it has a purple glow.
Plasma? This is what gas becomes if its electrons relax to lower energy states after being heated. You’ll have seen plasma lamps with filaments of colour that have derived from their basic gases. These colours are, to put it simply, the result of gases becoming ‘excited’ and entering a lower energy state. Plasma isn’t a solid or a liquid – it has no shape unless you enclose it in something – but it contains electrically charged particles. Neon signs work on it, but on a larger scale, plasma is the most common state of matter. Hydrogen, as the simplest atom known, in its plasma state constitutes roughly 75% of the Universe’s chemical elemental mass. It’s what the stars are made of.
We’ve been artificially producing hydrogen gas ever since Henry Cavendish recognised what it was in 1766 and understood that it produces water when burned. Its two largest uses at the moment are for fossil fuel processing (e.g. ‘fracking’ to split rocks and release buried oil) and ammonia production, mostly for the fertilizer market. However, on its own, it’s a difficult gas to handle. It embrittle many metals, which means it will quickly eat its way out of storage tanks, so it’s impossible to carry around by road or rail, or to use as a direct fuel in engines. However, it has potential uses as a new form of energy storage that could solve a lot of problems.
Electric cars, as we all know, are being enthusiastically promoted, particularly in cities where recharge facilities can be provided amply enough to reduce the disadvantage of the short battery life. For the designers of such cars, the problem has always been the weight of the batteries they have to carry around. We need a new system of storing electricity – something better and handier than banks of lorry batteries, and more realistic than recharging cars with electricity that may well have been produced by coal, gas or nuclear power stations.
This is where hydrogen comes in. It can combine with an energy-carrying liquid called N-ethylcarbazole to provide a source of power for automotive engines. The driver seeking to refuel a car would pump out the ‘used’ carbazole at the filling station and replace it with more of the newly-charged, high-energy stuff. Its substance is not burned as petrol or diesel are, butgives out hydrogen that can power a fuel-cell electric drive. The pumped-out carbazole would go off to be recharged and put into the normal tanks for re-use. This is being intensively researched by a university team in Nuremberg. Energy-carrying substances such the trade-named Carbozol can also be used for the stabilization of the electricity system and for energy storage in solar powered homes
