HYBRID HYDROGEN

Dick Pountain /Idealog 333/ 08 Apr 2022 10:08

I write about energy fairly often in this column, mainly in the context of CPU efficiency or the foibles of mobile batteries, but now seems like the time for a wider look. Putin’s invasion of Ukraine has thrown the global fossil markets into chaos, while the UK government has just revealed its long-term (not entirely feeble) strategy for increasing nuclear and wind power over the next 8 years. So this time I’m talking about the long run. 

I’ve been a convinced supporter of both nuclear power – fission and ultimately fusion – and the ‘hydrogen economy’ for around 50 years when neither was at all fashionable. I won’t rehash all the problems both face, which are well-known and debated, but will instead present two indisputable facts. Firstly the primary mode of energy delivery in advanced Western economies is turning toward electricity (and demand for it will soon exceed supply); and secondly, hydrogen is an impractical fuel for road, and perhaps for air, transport. It’s terribly inflammable, hard to store and has a knack of diffusing out of containers and pipelines.

You only have to remind yourself of the horror of power-cuts, when your phone and laptop batteries have run out, your router and internet connection are down (and maybe your gas central-heating controller is going nuts). Then think about the fact that electric car sales are approaching take-off, thanks to the soaring price of petrol and diesel, concern over air pollution and climate change. You don’t need a degree in economics to figure out what happens to electricity demand if all car users go that route. One solution would be to distribute the generation of electricity more widely, using small-to-medium nuclear and on-shore wind power stations. But I suggest that the solution we need to be looking at instead is a hybrid one, in which we keep electricity generation centralised – perhaps coastal – using nuclear, solar and wind power to generate hydrogen by the electrolysis of water. Then, instead of trying to distribute that hydrogen as gas or liquid, both fraught with danger, use it to make metal hydrides that can be distributed in standardised battery-like modules. The national chain of petrol stations replaces its pumps with hydrogen-pack replacement and recycling, which also eventually displaces the too slowly growing national grid of EV charging points. Such a distribution network of hydride packs would efficiently store and distribute energy produced by intermittent sources like solar, wind and tide, and replace bottled gas in remote rural areas beyond the reach of town gas. Such a system would require bringing two existing research technologies to commercial fruition: metal hydrides and hydrogen fuel cells, and I think that both can be achieved with sufficient investment.

A fuel cell turns a fuel like hydrogen into electricity directly, combining it with oxygen from the air within an electrolyte and electrodes rather than by burning it for heat. Invented way back in 1838 research has been extensive – as so often in history the military have lead the way in search of mobile battlefield power sources, and NASA has used them in spacecraft since the 1960s. 

Metal hydride storage has been around less long and remains more experimental. Hydrogen gas gets combined with a metal to form a liquid or a solid powder that requires neither high pressure nor cryogenic low temperatures to store, and the gas can be recovered by heating. Promising candidate metals include lithium, sodium, magnesium and aluminium, while boron combines with ammonia that can be turned back into hydrogen via a catalyst (the French company McPhy Energy is working on the first commercial product using magnesium). The Metal Hydride Fuel Cell combines these twin technologies into the same container, which gets recharged with hydrogen gas and outputs electricity directly: these are more experimental still, and once again the chief developers are currently the military.

It’s not yet clear what would be the best overall architecture for such a hybrid hydrogen economy: build a fuel cell into the electric car with exchangeable hydride packs; electric car with exchangeable metal-hydride-fuel-cell packs; existing EV with a fuel cell to recharge its conventional battery via hydride packs; even cars with hydrogen internal combustion engines and hydride packs. All sorts of questions over energy densities, performance and safety remain to be answered. 

But the history of the automobile tells us that eventually one architecture would triumph, witness the world-wide network of petrol stations. It’s also likely that an intermediate network of hydrogen liquid or gas to regional hydride recycling centres would need to evolve. What’s certain is that governments ought to be considering advice from people fluent in these technologies, then stump up the research funds that might just save both our current way of life and eventually the planet itself.  

[Dick Pountain has a picture of the Hindenburg disaster on his spare bedroom wall]