What’s wrong with Hydrogen cars?

Wednesday 21st October, 2015
In a big push for attention, dragging in the likes of Boris Johnson, Toyota has embarked upon the launch of the new Mirai - a car powered by water.

Well, not quite, hydrogen can indeed be extracted from water - the split "H2O" compound being broken down into its constituent elements of hydrogen and oxygen, by electrolysis of a salty water solution - essentially sea water. So we take sea water, bubble the hydrogen out of it and then use it to fuel the car. In the car's "engine", actually a complex fuel cell, the hydrogen is reacted with oxygen in the air to re-form water whilst generating electricity. The resulting exhaust is literally just running water, which drips out of the exhaust pipe. Technically so clean you could drink it.

So, science bit done, where is the catch? There is always a twist in these new eco cars, so where is the sting in the tail for the Mirai?

It makes sense at this point to draw a comparison to "all electric" cars like the Nissan LEAF. I've been a big critic of this one in the past and little has changed to alter that viewpoint.


The LEAF carries batteries which hold the charge required to power the car. The problem with batteries is that they don't carry enough energy, so you need lots of them. They are bulky and heavy, which makes the car a lot less efficient than it might be without. You lose all the weight of fuel and a heavy petrol engine, replacing with a lighter electric motor but then you add in a load of heavy batteries which ruins a lot of the potential savings.

By comparison, the Mirai also has a battery but it's much smaller. It's essentially just a hybrid battery, similar to that found in the Prius. It holds temporary charge from the fuel cell and also captures charge regenerated when the car is braking, to improve efficiency. So we have a lighter battery pack, a light electric motor and then a fuel tank full of hydrogen - a gas that is lighter than the helium we use to fill up kids party balloons. In fairness we need to add in the weight of the fuel cell engine but, unlike the electric car batteries, it isn't made from rare earth metals that have to be mined and shipped from over the world.

So how about refuelling? Electric cars can take hours to charge and repeated use of fast chargers can degrade their batteries faster. Even Tesla owners have been complaining about reduced range from their cars as they get older. There are many criticisms of electric car charging, from the time it takes, out of service charging points to coiling up a wet cable in the rain. So how does the Mirai compare? Well, you pull up to a filling station, open the fuel flap and pump it full. Takes moments and gives you hundreds of clean miles of range. In many respects, it's just like filling up a petrol car - but without the fumes. With hundreds of miles in the tank, range anxiety isn't a major issue, although it will obviously take a little while for hydrogen filling stations to come online. Unlike electric chargers, however, the refuelling model is very compatible with forecourt petrol stations. These depend on lots of customers who are only there for a few minutes each - most of the profits being made in the shop, not on the fuel, a high turnover of customers is essential - not the one or two an hour you get from an electric charger.

So what about heating the car? These shorten the range a lot on an electric car. A 100 miles summer range can easily drop to 60 miles if you heat it like a petrol car in winter. Petrol cars have always had an advantage here. Whilst EV owners point at them being very inefficient, a lot of the waste is heat. We capture some of that heat to warm the car, so the heater in a traditional car is effectively free of both cost and range loss. In an electric car you need to have an electric fan heater, like having a hair dryer in the dashboard. This, like your teenage daughter doing her hair, uses a lot of electricity and kills the range.

So how does the Mirai compare? Well, the fuel cell converts hydrogen and oxygen to water and electricity. This isn't 100% efficient but a lot of the waste is...heat. So we can heat and defrost the car for "free" again, just like an old petrol car.

Incidentally, all "eco" cars use electric air conditioners these days so the costs of cooling each car type in summer is pretty much equivalent.

So what about that hydrogen fuel and the energy costs for extracting it from its source? We all know that you can be naive enough to put a solar panel on your roof and (somewhat falsely) claim your electric car is environmentally friendly and zero emissions. Well, let's just put a solar panel on the roof of the hydrogen factory and a wonderful turbine in its car park. That's clean, right? Well actually, technically it is. We could do similar for an oil refinery, dramatically reducing the alleged carbon footprint, but there will still be horrible chemicals and gases used and created in the process. No reason why living next door to a hydrogen factory would be an issue and certainly better than living next to a coal fired power station.

So who's paying for all this? Electric cars got massive subsidies from the government for assembly plants, battery factories etc. On top of that, they paid up to £5000 of the price of any electric car - middle class solar panel owners taking £5k of tax payer's money every time they buy an £80k Tesla. By comparison, there is no such subsidy on hydrogen cars like the Mirai - which may make them more expensive.. They will, however, undoubtedly be exempt from the London Congestion Charge for the foreseeable future. A car that you can drive both to and into London without paying a congestion charge or having to refuel every 100 miles.

So what's wrong with hydrogen cars? To be honest, I'm struggling to find anything. We've effectively got a Prius that is powered by water, only emits water and the fuel can be produced with no additional environmental emissions. The only thing is that the water will drop all over your garage floor. Oh, Toyota thought of that too, it stores the water until it's on the open road after which you can release it with a button on the dashboard. Genius!

Never mind Back to the Future, the future is now!

Comments/Trackbacks [1]