Except that it's 10x higher than batteries.
Except it's not if you need to transport electricity from deep-sea wind-farm, overseas solar farms, etc.
You clearly have an axe to grind with Hydrogen, but I'd suggest a little bit of deeper thought on the topics raised above. It's nonsensical for cars indeed. We are on a railway forum, not a car forum.
Oh I've given it plenty of though and also done the calculations myself.
Firstly there is a difference between energy density and power density, batteries are much more interesting on the later basis.
The only issue I have with "Hydrogen" is the current snake oil salesmen and PR agencies attached to it in many cases. They are very selective about what is publicly shared and some how forget to mention the problems and disadvantages or benchmark it against other technologies, over the last year or so Hydrogen in rail has been subject to increasing independent scrutiny. You do presumably realise that Hydrogen MU are actually
battery EMUs as they need as much regenerative braking energy recovered as possible to reduce the Hydrogen requirements.
Might I suggest you have look at the the excellent Scottish Rail Decarbonisation Action Plan report published yesterday as it has plenty to add on this subject and funnily enough matches exactly what I have been saying:
A rolling programme of electrification is essential to achieve journey time savings, lower operating costs and reduce emissions on more busy, high speed or heavy haul routes. The alternatives to full electrification will have a role for lightly used routes and on some long distance routes, where full electrification is not financially justified. The alternatives will also have a valuable role in the transition period until the optimal electrified network can be completed. Battery-electric trains have potential to offer operating cost savings (along with zero emissions) when compared with diesel power without the capital cost of full electrification infrastructure, though the capital and operating costs of battery electric vehicles are higher than standard electric trains. They can be brought into service relatively soon. They are currently considered effective for lower-intensity services of up to around 55 miles. Recent estimates suggest adding battery capability to electric trains adds around an additional 25% to their capital cost. The cost-effective viability of hydrogen is expected to improve over time as usage volumes increase noting that the cost of diesel may increase as less diesel is required for road transport. Hydrogen fuel cells do have the potential for services over longer distances, though the comparatively low energy density of hydrogen requires large fuel storage volume on trains for longer ranges. Initially hydrogen-fuelled trains are expected to have higher capital and operating costs than diesel trains. Emissions with the use of hydrogen fuel depend on how the hydrogen is generated, but will be substantially lower than diesel use. The opportunity is to focus on using hydrogen from renewable sources for zero emissions compared with diesel trains. Already in Scotland significant investment in production and distribution for hydrogen fuel is taking place and this is expected to become a major energy source for rail as well as domestic/industrial gas supply and other forms of transport.
...
Relative energy efficiency of traction types An electrically powered train is the most energy efficient form of traction. For every 1kW of power through its wheels it requires about 1.2kW from the National Grid. The small amount of energy loss is due to transmission from production to the traction motor via the National Grid, sub-stations, the overhead line equipment and on-train equipment. This loss means that in terms of power to create and power used in its drive an electric train has an efficiency of over 80% and there is the potential of a zero-carbon option particularly if the electricity is generated by sustainable sources (e.g. wind, hydro, tidal or solar). A battery train is 12% points less efficient in its operation than an electrically powered train because of the constraints of the battery i.e. its capacity to store and release energy, which, together with the weight of the battery, has a bearing on its range and capabilities. An electric train by contrast with unlimited access to electricity has a higher power range and thus has the capability to operate more efficiently in challenging situations such as inclines. Additionally, the cost of a battery adds about one third or more to the capital cost of a similar electric train powered via a catenary system. A hydrogen fuel cell train currently has some advantages over a battery train in that it can typically operate over longer non-electrified routes than a train with battery traction. Additionally, refuelling with hydrogen is fast, though hydrogen fuel occupies some seven times the volume as diesel for the same amount of energy. However, with hydrogen, 3.4kW of power is required to generate 1kW of drive via electrolysis and compression to the on-train fuel cell and converter. This gives an efficiency rating of less than 30%. It is expected that technology advancements will be made in the coming years to improve the efficiency of hydrogen fuel cells however it remains a considerable way behind electrification. That said it will have a role particularly on those lightly used routes where catenary systems may not be appropriate or cost effective and where battery would not have the range. A diesel train is the least energy efficient source of traction as 3.9kW of oil via extraction and refining before being stored on train for delivery to the engine and transmission is required to deliver 1kW of drive. This delivers an efficiency of about 26% which is the lowest of all fuel types and fails to take into account the noxious gases and particulates produced in its use.
Rather unsurprisingly as these are accurate numbers these numbers happen to be very close to the ones I have posted on this and other RF Hydrogen threads over several years, sorry if this disappoints you.
So in summary:
Electric efficiency >80% [My previous postings 80-85%]
Electric efficiency = electric -12% i.e. > 68% [My previous postings 65-72% depending on route, battery capacity etc.]
Diesel efficiency = 26% [My previous postings 25-28%, worth noting hybrid diesel-battery rafts on DMUs would increase this through reduced idle] Also worth nothing that Transport Scotland have gone for the full Well-to-Wheel analysis
Hydrogen efficiency < 30% [My previous postings 23-28%, one well known rolling stock manufacturer agrees with my numbers]
I suspect rather rarely I have rail traction, gas compression and high pressure hydrogen expertise though all separately.
I actually believe hydrogen is part of the long term solution, just that is is being over sold by some with vested interests currently and they are being believed by some. Grayling was certainly taken in...
Efficiency of the overall energy system (i.e. use less energy) is a key part of national all sector decarbonisation strategies but Hydrogen is comparatively inefficient for rail and is more efficient in other sectors such as natural gas grid substitution where HP compression is not required (big efficiency gain if used there instead) or high temperature chemical processes such as cement manufacture where electric heating doesn't cut it. The NIC is proposing taking such a directional approach to UK Hydrogen usage in it latest murmurings so UK rail should not expect huge hydrogen availability.
yours
Dr "HWL" BEng MEng CEng
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