This is exciting. A neat solution – in one hit – to the major problems (as I was referring to earlier) with hydrogen cars: the huge cost of generation, storage, distribution, and filling-station infrastructure; the poor safety, high weight, and low energy density of stored hydrogen gas; and the lack of an environmentally positive way of liberating the hydrogen in the first place.

New Scientist reported recently on a system developed by Tareq Abu-Hamed, of the University of Minnesota, and colleagues at the Weizmann Institute of Science in Israel. The key ingredient is boron.

No need for a hydrogen filling station – in this system, you liberate the hydrogen on demand, in the car itself. To have the equivalent energy storage of a 40-litre petrol tank, your hydrogen car will have:

  • a 45-litre tank of water;
  • three 6-kilogram removable packs of boron powder.

When you start the car, water is heated (with either battery power or using a small amount of stored hydrogen) and reacted with boron powder. This produces hydrogen gas and boron oxide powder. The hydrogen is combusted to drive the car (and heat the water, and generate electricity to charge the battery, run the headlights, and all those other little things). The combustion of the hydrogen produces water vapour, which is captured back into the water tank. The boron oxide powder is stored in removable packs.

When the boron is nearly used up, you go to your local garage (or supermarket, or fast food joint, or whatever), take out your packs of boron oxide, and exchange them for packs with fresh boron powder. The boron exchange place doesn’t need to have all the infrastructure of a petrol filling station: no highly explosive substances, no bowsers, just sealed powder packs. I imagine them as being like car batteries in size and weight. And you top up your tank, of course. With water.

The other half of the system is the reprocessing of the boron oxide back into boron:

While Abu-Hamed’s scheme still requires a distribution network and reprocessing plant, he has devised an ingenious plan that will allow the spent boron oxide to be converted back to metallic boron in a pollution-free process that uses only solar energy. Heating the oxide with magnesium powder recovers the boron, leaving magnesium oxide as a by-product. The magnesium oxide can then be recycled by first reacting it with chlorine gas to produce magnesium chloride, from which the magnesium metal and chlorine can then be recovered by electrolysis.

The energy to drive these processes would ultimately come from the sun. The team calculates that a system of mirrors could concentrate enough sunlight to produce electricity from solar cells with an efficiency of 35 per cent. Overall, they say, their system could convert solar energy into work by the car’s engine with an efficiency of 11 per cent, similar to today’s petrol engines.

Beautiful. A near-closed system, in terms of materials, with solar energy as the primary input and mechanical energy as the output.

There are some other issues. The main one is the sourcing of the boron oxide in the first place – the costs and environmental effects of the mining of the borax ore. It is apparently abundant on Earth, with the largest sources in Turkey and the US. I haven’t personally been to Boron, California, but I guess they’d be happy about this prospect.

Let’s hope this idea doesn’t get bought out and buried, because it’s the single best solution I’ve come across for the car problem – one of the biggest greenhouse hurdles we have. Getting rid of those stinking petrol fumes is a nice bonus.