Hydrogen – the next revolution?

Automotive engineer and all-round technical seer Andrew Marsh checks the Periodic Table to see if hydrogen might be the next great leap forward in vehicle technology

Published:  01 October, 2020

For as long as I can remember, the questions arising from presentations to our sector usually involve at least one about hydrogen. This can be seen as an abundant, readily available resource and a solution to long-term electric power generation akin to nuclear fusion, in that in both cases the by-product is harmless.    
    
Pure hydrogen is an important component of many industrial chemical processes, so generation of more hydrogen to feed transportation will add pressure to existing industrial capacity. Hydrogen exists either in association with itself (H3 – which is unstable) or with other atoms (for example water, H2O – which is stable). It also exists inside many, many organic compounds, but effectively is not available in nature as a pure gas.  
    
Pure hydrogen can be manufactured from coal, oxidation of methane or steam reforming of methane. Methane is a principle component of natural gas, so there is a plentiful supply of raw material. Most of the pure hydrogen available for use today is made by one of these industrial processes, which all require energy to effectively extract the hydrogen and then more energy to compress it to the point the gas liquifies.
    
Hydrogen can also be extracted by passing electricity through water, and there have been many aftermarket kits that do exactly this to generate a form of hydrogen peroxide which is then ducted into an internal combustion engine intake system to offset the hydrocarbon fuel burn rate. However, if we need to generate pure hydrogen on a scale to develop transport, this process needs to be upscaled.
    
The conclusion: Pure hydrogen prefers to be attached to other atoms to achieve stability, and if we need to extract it requires is an energy investment. Further, the most common source of pure hydrogen is from natural gas, where the by-products are carbon dioxide and carbon monoxide. Hardly right-on.  

The application
Let’s skip eco-obstacles. What can we do with it?
    
There are essentially two routes to use hydrogen. Some manufacturers openly experimented with hydrogen as a fuel for internal combustion engines.
    
Mazda built several Wankel engines fuelled by hydrogen. In theory, apart from trace hydrocarbon pollution due to lubricants, the tail pipe emissions would be zero in terms of traditionally measured pollutants. The reason for Mazda doing this? The Wankel engine has two major drawbacks – sealing, and a long, thin combustion volume with a vast surface area to volume ratio. Yes, the Wankel engine is ‘emission disabled’.
    
Meanwhile, BMW built a few factory-owned 7 Series E65 based long wheel base limousines, complete with CFRP body structure inserts around the rear sill/subframe/C pillar area. The V12 engine was fed with hydrogen stored in a large tank located in the boot above the rear subframe (hence the CFRP structural magic parts) and had a small fuel tank located under one rear passenger seat. The vehicle was bristling with contradictions – a huge engine which could run further on the tiny petrol tank that it could from the huge insulated hydrogen fuel tank, which was designed to keep the liquified fuel at -273°C for as long as possible. Oh, and it needed a system to ensure the liquid hydrogen became gas as it entered the pointlessly vast engine.
    
These experiments confirmed what was already known before any of these prototype vehicles were built. Hydrogen does not have the energy density of petrol or diesel, and there are significant issues in storage of the fuel either at under pressure at normal temperature (i.e. serious pressure vessels) or super cooled at ambient (i.e. seriously bulky insulation).
    
The second route? Drum roll…the hydrogen fuel cell. This is a form of battery. It has taken many years to develop, and the once sky-high cost of the main component – the ‘stack’ – is gracefully gliding downwards. Essentially pure hydrogen atoms are introduced to oxygen atoms, where a membrane allows the atoms to join and the electricity generated in the process is extracted. This is electric power generation from pure hydrogen and air, using the oxygen in the air. Hydrogen has a greater affinity to oxygen than oxygen has for hydrogen, so only one component needs to be made unstable to create the vital atomic level re-assembly.
    
Do we need pure hydrogen to do this? Well Chrysler many years ago developed a fuel cell stack that would run on petrol or diesel, but of course the tail pipe emissions, while dramatically reduced, were higher than if we put pure hydrogen into the system. In addition, early membrane technology was highly intolerant of impurities, but much important work has taken place to make the fuel cell stack tougher.

Other considerations
Let’s not forget, if we consider hydrogen fuel cell stack electric power generation to be the future of transport, and bypass the significant issues in creating additional production capacity for pure hydrogen let alone the increase on electricity demand or environmental impact, there is a further important factor to consider. Fuel cell stacks like to generate power under steady state conditions. They do not like Vmax/ standing starts/traffic light GPs.
    
So, we have electricity generated at a steady rate, but we have demands which are variable and include dumping harvested energy back into the system (regenerative braking). Yes. There’s the clue. In a pure electric system, we have to add a pure electric vehicle in its entirety (low voltage system, high voltage system, power controller, DC-AC converters, on-board recharging, electric traction motor and the energy storage system).
    
That means we have two powertrains. An on-board electricity generator powered by hydrogen, and a pure electric powertrain. Oh, and while fuel cell stack prices have fallen below €10,000, that’s still way, way more than either plugging a vehicle into a larger, more efficient power generation system (and yes, that’s a story for another time) and even more than an internal combustion engine used as an emergency power generator.
    
Then there’s business interests. Manufacturers of bottled gas are naturally very supportive of the hydrogen power movement, as are many oil companies. True, initially only Total supported this, but most companies now recognise in the new lobbyist infested world of eco-warriors, selling hydrocarbon fuels needs some ‘eco’ messaging.
    
The upshot is oil companies (considering profits) and especially government (considering the ludicrous 80%+ tax revenue per litre) do not want to switch off the oil-based economy just yet, and as usual for the public sector, there is no strategy nor plan for any potential transition should the prevailing economic objections to hydrogen (or any other great idea) change. That immediately gets in the way of ‘what comes first’: Fuel supply system or vehicles which can use the ‘new fuel’. The prototype of this situation is rolling out now – electric vehicles have relatively poor access to public charging points, and recharging them in an urban environment can be hazardous for residents. In the UK there are handful of hydrogen refuelling stations, and for the most part the main source of the energy is from bottled gas. Not quite seamless.
    
While the refuelling station lines and nozzles for hydrogen are bulkier, heavier and bigger than the equivalent petrol, diesel or natural gas LPG systems, there have been zero accidents due to hydrogen leaks during refuelling. Yes, there are tiny numbers of vehicles and some users – such as those operating buses or trucks – could be considered to be even more considerate than the general public could be. There is another major benefit – recharging the energy source takes as long as we are used to, a matter of minutes rather than hours, being kind to the battery, or 30 minutes plus, if we want to sustain long-term damage to the battery.

The future
Is the future hydrogen? Nope. Not for personal transportation, and COVID-19 has just buried the plans for some manufacturers to introduce hydrogen fuel cell powered vehicles.
    
And yet, there is one need right now. Semi-trailers which are refrigerated are a cornerstone of food transportation as well as medication, and have the ability to be run from the tractor unit, from the national grid or a small, badly made diesel engine. For anyone who can remember being at a Channel Port or EuroStar waiting to board, the sound of these little diesel engines is very clear. It is not always possible to hook up a refrigerated trailer to a fixed electricity source, so a quiet system is required – the fuel cell! This is already underway.
    
There’s more though. In the unsolved hard-wired world of pure electric vehicles, the process of energy transfer is firmly in the 1800s. If we casually assume this problem will be solved at the same pace as the energy density improvement of batteries, and we venture away from the leafy suburbs of North London, much drama awaits. Further, if one lives ‘in the provinces’ running a pure electric vehicle is not straightforward due to availability of energy top-up points. Enter the hydrogen fuel cell. Suddenly apart from cost of the base electric vehicle, the cost of the additional fuel cell stack system, the energy/environmental impact of making the pure gas… we have a solution.
    
Rather than drinking the pure water that comes out of the tail pipe, perhaps we really should just drink the finest socialist Champagne. Still, who knows what the future holds?


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