Though Toyota may be a big fan, hydrogen cars have a problem. Energy must move from wire to gas to wire to power the car. There are always significant losses when the energy vector changes. For Battery Electric Vehicles (BEV) the energy stays on wires all the way to the car. Tom Baxter at the University of Aberdeen looks at the losses at each stage to show that for hydrogen only 38% of the original electricity gets used. For BEVs it’s 80%. Hydrogen has other advantages. Its energy density means a full tank gives it a far greater range, and refuelling is quick. But refuelling innovations for BEVs are catching up. Specifically, the concept of not recharging but swapping your low battery with a fully charged one at a station – it can take minutes – solves the range problem. That implies the renting of your battery, which usefully spreads its cost (the battery can be 25% of the up-front cost of a new BEV). Baxter believes hydrogen will play an important role in industry and heating, but very much doubts it for cars.
Hydrogen has long been touted as the future for passenger cars. The hydrogen fuel cell electric vehicle (FCEV), which simply runs on pressurised hydrogen from a fuelling station, produces zero carbon emissions from its exhaust.
It can be filled as quickly as a fossil-fuel equivalent and offers a similar driving distance to petrol. It has some heavyweight backing, with Toyota for instance launching the second-generation Mirai later in 2020.
The Canadian Hydrogen and Fuel Cell Association recently produced a report extolling hydrogen vehicles. Among other points, it said that the carbon footprint is an order of magnitude better than electric vehicles: 2.7g of carbon dioxide per kilometre compared to 20.9g.
Significant role for Hydrogen. But not in cars
All the same, I think hydrogen fuel cells are a flawed concept. I do think hydrogen will play a significant role in achieving net zero carbon emissions by replacing natural gas in industrial and domestic heating. But I struggle to see how hydrogen can compete with electric vehicles, and this view has been reinforced by two recent pronouncements.
A report by BloombergNEF concluded: The bulk of the car, bus and light-truck market looks set to adopt [battery electric technology], which are a cheaper solution than fuel cells.
Volkswagen, meanwhile, made a statement comparing the energy efficiency of the technologies. “The conclusion is clear” said the company. “In the case of the passenger car, everything speaks in favour of the battery and practically nothing speaks in favour of hydrogen.”
Hydrogen car’s efficiency problem
The reason why hydrogen is inefficient is because the energy must move from wire to gas to wire in order to power a car. This is sometimes called the energy vector transition.
Let’s take 100 watts of electricity produced by a renewable source such as a wind turbine. To power an FCEV, that energy has to be converted into hydrogen, possibly by passing it through water (the electrolysis process). This is around 75% energy-efficient, so around one-quarter of the electricity is automatically lost.
The hydrogen produced has to be compressed, chilled and transported to the hydrogen station, a process that is around 90% efficient. Once inside the vehicle, the hydrogen needs to be converted into electricity, which is 60% efficient. Finally the electricity used in the motor to move the vehicle is around 95% efficient. Put together, only 38% of the original electricity – 38 watts out of 100 – are used.
Battery Electric Vehicles lose less power
With electric vehicles, the energy runs on wires all the way from the source to the car. The same 100 watts of power from the same turbine loses about 5% of efficiency in this journey through the grid (in the case of hydrogen, I’m assuming the conversion takes place onsite at the wind farm).
You lose a further 10% of energy from charging and discharging the lithium-ion battery, plus another 5% from using the electricity to make the vehicle move. So you are down to 80 watts – as shown in the figure below.
In other words, the hydrogen fuel cell requires double the amount of energy. To quote BMW: “The overall efficiency in the power-to-vehicle-drive energy chain is therefore only half the level of [an electric vehicle].”
Refuelling innovations for BEVs are coming
There are around 5 million electric vehicles on the roads, and sales have been rising strongly. This is at best only around 0.5% of the global total, though still in a different league to hydrogen, which had achieved around 7,500 car sales worldwide by the end of 2019.
Hydrogen still has very few refuelling stations and building them is hardly going to be a priority during the coronavirus pandemic, yet enthusiasts for the longer term point to several benefits over electric vehicles: drivers can refuel much more quickly and drive much further per “tank”. Like me, many people remain reluctant to buy an electric car for these reasons.
BEV “battery swap” stations
China, with electric vehicle sales of more than one million a year, is demonstrating how these issues can be addressed. The infrastructure is being built for owners to be able to drive into forecourts and swap batteries quickly. NIO, the Shanghai-based car manufacturer, claims a three-minute swap time at these stations.
China is planning to build a large number of them. BJEV, the electric-car subsidiary of motor manufacturer BAIC, is investing €1.3 billion (£1.2 billion) to build 3,000 battery charging stations across the country in the next couple of years.
Swapped, rented batteries benefit consumers
Not only is this an answer to the “range anxiety” of prospective electric car owners, it also addresses their high cost. Batteries make up about 25% of the average sale price of electric vehicles, which is still some way higher than petrol or diesel equivalents.
By using the swap concept, the battery could be rented, with part of the swap cost being a fee for rental. That would reduce the purchase cost and incentivise public uptake. The swap batteries could also be charged using surplus renewable electricity – a huge environmental positive.
Admittedly, this concept would require a degree of standardisation in battery technology that may not be to the liking of European car manufacturers. The fact that battery technology could soon make it possible to power cars for a million miles might make the business model more attractive.
It may not be workable with heavier vehicles such as vans or trucks, since they need very big batteries. Here, hydrogen may indeed come out on top – as BloombergNEF predicted in its recent report.
Emissions: BEVs charged with 100% renewable power match Hydrogen
Finally a word on the claims on carbon emissions from that Canadian Hydrogen and Fuel Cell Association report I mentioned earlier. I checked the source of the statistics, which revealed they were comparing hydrogen made from purely renewable electricity with electric vehicles powered by electricity from fossil fuels.
If both were charged using renewable electricity, the carbon footprint would be similar. The original report was funded by industry consortium H2 Mobility, so it’s a good example of the need to be careful with information in this area.
Tom Baxter is a Senior Lecturer in Chemical Engineering, University of Aberdeen
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Hugh Sharman says
Good article but a pity the headline is so ambiguous!
Don’t ignore the prodigious use of scarce metals in BEVs. https://www.nhm.ac.uk/press-office/press-releases/leading-scientists-set-out-resource-challenge-of-meeting-net-zer.html
Mining pollutes big time and, for Heavens’ sake emits untold quantities of GHGs
Mr Burl Solomons says
Don’t forget the prodigious use of rare earth metals in Hydrogen fuel cells as well. Not to mention their use in the oil refubing industry.
Mark Smith says
Completely irrelevant to the hydrogen economy and biased, climate change is about reducing CO2 to zero, it’s not about reducing energy use unless you are still using fossil fuels. If you are using surplus renewable energy at source to convert to fuel you don’t have to push absolutely everything through your electricity grid.
Colin Megson says
The green hydrogen from intermittents movement is becoming an unstoppable juggernaut. Every day for the last 6 months, intermittents companies and fossil fuel money have combined to announce developments, investment and plant builds.
Green hydrogen is the only – the one and only – technology that can solve the INTERMITTENCY PROBLEM and provide genuine 24/7/365 electricity from intermittents and make use of the massive capital investment that has to go into surplus intermittents’ installed capacity.
But hydrogen stores that surplus electricity and like any storage technology, it has to be put somewhere (for returning back to electricity when the wind don’t blow and the Sun don’t shine). Humongous volumes have to be stored in salt caverns and converted back to electricity through a Power-to-Gas-to-Power (P2G2P) infrastructure.
But this plan will turn out to be the longest suicide plan ever known to man. Because advanced nuclear power companies have an even more cunning plan. 5 years or so down the line, when all of that capital from oil and intermittents companies have got the piped, trucked and on-site production infrastructure for green hydrogen in place, up they will step.
Advanced nuclear power plant (npp) manufacturers, like GE-Hitachi with their BWRX-300 Small Modular Reactor (SMR), will proclaim they can build these SMRs in 2 years for 1/5th of the capital investment needed for onshore wind and guarantee investors 7.5X more in earnings. What’s more, they can manufacture green hydrogen, to replace natural gas and petroleum for all heating, transport and industrial use at 1/5th of the capital investment required for intermittents.
And they generate 24/7/365 electricity without any need whatsoever for the extra, wasted capital investment for a green hydrogen storage and a P2G2P infrastructure. Politicians dictating the UK’s energy strategy to get to zero carbon should have uppermost in their minds, the regards of the what their decisions will mean to future generations in terms of environmental impact.
The advanced npp way will use 1/15th of the materials and resources of intermittents. But more importantly, environmentally they will have 1/3000th of the ecosystem destruction, species wipe-out and waste mountains of any mishmash mix of intermittents technologies.
Mike Malone says
. . . . and, furthermore, the electricity so generated will be too cheap to meter!
What about hydrogen from plastic waste
Colin McKeown says
Yes H2 generated from waste plastic and also waste tyres should be doubly transformational by addressing THREE environmental problems at once! 1.Elimination of unrecyclable plastic waste 2. Elimination of unrecyclable tyre waste 3. Production of a zero carbon energy source.
The technology currently exists to use waste as a fuel source to produce H2. The production process has a minimal carbon footprint as the process is fully enclosed.
What’s not to like about this approach?
Colin Mckeown says
Yes as suggested above you need to measure and factor in the average resources and energy used to make the battery versus the same to make an average equivalent fuel cell.
Sven NV says
Of course you loose a lot of efficiency by taking a detour through hydrogen. But currently this is not the issue.
Storing and transporting the energy — especially when it is generated from wind and solar — to deliver it when and where it is needed is currently the more pressing obstacle.
The bigger energy density of H² seems to be more important for both, the convenience of shorter stops to recharge a vehicle, but more importantly for “greening” the power grid at large
Hydrogen is greener than virtually every EV powered by a battery. Where does the energy to charge the EV come from? A coal or gas powerplant is usually the answer. This focus on energy conversion is highly misleading. The focus should be on sustainable energy that doesn’t add to climate woes.
Kees Onman says
And where does the energy for hydrogen come from?
Hydrogen for person transportation is 100% dangerous bullshit.
Eare materials for BEV are also user for Hydrogen and fossil fuel. Cobalt is used in abundance to make petrol and diesel.
Hydrogen uses 2x the amount of power and mandates many extra trips to the garage for replacement and mantenance.
Hydrogen has NO advantage. It is dangerous,expentsive, impractical.
Even filling up a tank will cost on hell of a lot more of youre tine compared to charging. Not only because you need to male detours but also because of the requered 700 bar pressure buildup.
Hydrogen maybe something for intercontinental transport.
AA KK says
Solar and wind energy are very cheap at peak times. There are even cases where the price drops below zero.
Batteries are not suitable for long time storage, hydrogen is (better), making the business case for hydrogen (cars) valid.
Colin McKeown says
I don’t understand why some people need to slag off battery technology or hydrogen as a fuel source. They can both happily co exist. They both have their differences and merits. I don’t see this as some kind of competition where one has to win or dominate the market. All of this is in the name of progress and to the benefit of the environment.
Sergei Popov says
I’m agree completely with your point.
While BEV vis kind of ideal for city shuttling Mom’s with their kids, taxi (with fast change of batteries), and likes, the H2 is for buses, trucks, and even for aviation – from regional to super jumbo jets (today I’ve found one nice study on LH2, FC, butteries and turbofan).
See, Japan’s Energy motto is “Energy, Economy, and Environment with inherent Safety”, so when it comes to the issue of hydrogen, there is the answer – follow regulation and keep strict eye on technology rules implementation.
Gopal Duleep says
While a agree that EV and hydrogen can theoretically co-exist, I don’t see how the transition would work as it would destroy demand for oil and gas (which is already happening). If the conversion of light vehicles to EV is even partially successful, oil will trade below $30/bbl making any transition much harder. Only a strong regulatory push will do this, but given the push back against even wearing a mask during a pandemic, the West will have armed rebellion if everyone is forced into EV and FCEV vehicles!
Dan Thacker says
The 700 bar hydrogen fuel cells won’t be an issue. Several companies have already cracked that.
BEV will most like work out best for the car but hydrogen will more likely power large trucks and aeroplanes of the future. Batteries for either of these use cases is completely unfeasible right now.
So both EV and hydrogen will play a significant part in future green vehicle strategy.
Hydrogen and nuclear will both likely play a part in future power generation as well as natural gas.
Any suggestions that any one of these power sources willl not have significant use cases in future will likely prove erroneous I would imagine.