Nov 152017
 

Li-ion batteries have become so much better, and so quickly, that there’s no longer any role for fuel-cell vehicles.

These days, Toyota is the best known auto maker promoting fuel cell vehicles.  Yes, they are a very sensible and very successful company.  But even the most successful companies in the world are not always right on every product they develop/support; indeed, it could be said that the more successful the company, the more willing it is to risk failures.

Look at Microsoft or Google for examples of successful companies proudly surrounded by their many failed products.  Or look at the many technological developments that promised to be the future of something, but which instead became dead ends.  Eight track tape cartridges.  Or, more recently, plasma screen televisions, and quite possibly, 3D screens too.

The mere success of a company is no guarantee that all its products will be successful.  And so one should not automatically equate Toyota’s support of fuel-cell technology as guaranteeing the good sense of this technology, and indeed Toyota itself is increasingly hedging its bets – having been an early and successful pioneer of hybrid vehicles, and now moving to fully battery-electric vehicles too and investing into future battery technology research.

Fuel Cells – Once A Promising Future, Now an Obsolete Past

Perhaps it is fair to say that there was a time when fuel-cell powered vehicles looked viable, but the rapid developments and improvements in battery technology have obsoleted and/or are obsoleting the fuel-cell concept.  This is similar to many other technologies that have appeared only to be displaced by other technologies.  Also similar is the slowness with which some proponents of the displaced technology react and respond to the changed marketplace and competitive environment.

There is really only one still one remaining advantage claimed by fuel-cell vehicles – the ability to refuel your vehicle almost as quickly as you could pump gas (ie petrol not hydrogen) into a regular vehicle, and to have a comparable range per full tank.  Indeed, some fuel-cell vehicle options offer more range between fill-ups than do similar petrol or diesel powered vehicles.

Back when battery powered cars had very short range (under 50 miles) and very slow charging (maybe adding only 3 – 10 miles of range per hour of charging), this long-range and fast-refuel capability of a fuel-cell type vehicle had great appeal, as did – also back then – the lower extra cost of fuel-cell technology compared to battery technology.

But now, not so much.  You can get 150 miles of range added to an electric car in 20 minutes – sure, that is nowhere near as good as 400 miles of range in 10 minutes, but it is also nowhere near as crippling as the previous slow charging was.

Furthermore, the whole ‘slowness to recharge’ issue is very much a red herring. The currently comparatively slow rate of charging of electric vehicles is only seen as an issue by people who do not have electric vehicles.  There is also a huge and balancing benefit of having an electric vehicle that few people who don’t own them appreciate – the ability to recharge your vehicle, at home.  For those of us with designated parking spaces that can have a home charger placed alongside, we are freed from the hassle of having to detour off our route to buy petrol.  Buying petrol isn’t just the five minutes of pumping time – it is the time to get to the gas station, maybe to wait for a pump, to pump the petrol, to pay for it, and then to get back onto your route to where you were going again.

Talking about range as well as recharge time, electric cars nowadays will often go 200 – 300 miles on a single charge.

For most of us, most all the time, we never drive more than 200 miles in a day (few people even drive over 50 miles a day) and so, similar to our cell phones, we simply connect our car to its charger each night, and never, during the day, have to think about range or worry about running out of charge.  Indeed, whereas cell phones struggle to get through a day and seldom could last two days, an electric car, at 50 miles or less a day, and 200 miles or more total range, is likely to manage for almost a week between charges.

The future trend in battery technologies suggests faster charging and greater ranges will continue to evolve, whereas for fuel-cells, their filling and storage technology is more mature and there is less chance of matching improvements.

It isn’t just the charging speed and driving range of electric cars that has been improving.  The cost, the size, and the weight of batteries has all been positively evolving over the last decade or so, removing these once major negative factors for battery powered cars.  Between 2010 and 2016, the cost of Li-ion batteries has dropped more than four-fold, from $1000/kWh to $227/kWh, and continues to drop further.  Back in 1991, the cost was $3,200/kWh.  At the same time, a battery of given size can now hold over ten times as much electricity.

Looking speculatively into the future, there are several promising new battery technologies that may give not just further incremental improvements in cost, size/weight, capacity, and recharging speed, but massive disruptive improvements.  There are no such opportunities available for hydrogen, due to the unavoidable physical and chemical limits on the process.

So, maybe hydrogen fuel-cell vehicles were once a great idea.  But they are no longer.  It is time for Toyota and other manufacturers to stop focusing on them, and – more to the point – it is time for governments to stop encouraging and subsidizing this technology.

The Little Talked About Problem with Fuel Cells

Battery powered vehicles haven’t just caught up with fuel-cell powered vehicles.  They’ve zoomed on past.

Sure, you’ve read the gushy stories about how fuel-cell vehicles have no emissions other than a bit of pure water mist, and how their cost is coming down.  Quiet clean technology, low maintenance with almost no moving parts.  And so on and so forth – it is easy to understand the enthusiasm that supporters of fuel cells have.

But how often do you read stories about how much per mile the hydrogen costs to fuel the car?  How often do you read stories that look beyond the ‘clean burning’ fuel cell and its water vapor output to an analysis of what hydrocarbons may have been burned to create the hydrogen in the first place?

The ugly reality is that hydrogen is a much more expensive fuel than electricity, and expressed in terms of a ‘miles per gallon equivalent’ is massively inferior to batteries, and possibly inferior to gasoline as well.  Let me explain why.

It is All About Electricity, Not Hydrogen

Forget the hydrogen.  The surprising fact is that both fuel cell and battery powered vehicles actually use the same ultimate source of power.  Electricity.  Hydrogen is merely a way to transport the electrical energy.  Electricity is used to extract hydrogen, and then in the fuel cell, the ‘stored electricity’ in the hydrogen (gack – that’s a terrible simplification, but an acceptable one for these purposes) is then recovered as part of the process where the hydrogen bonds with free oxygen in the air to form water.  The recovered electricity then powers an electric motor.

As for a battery powered vehicle, electricity is stored not in the form of hydrogen, but in a battery (as chemical energy), and then converted back to electricity, which is then used to power an electric motor – quite possibly a motor identical to the one in the fuel-cell vehicle.

The only difference in these two processes is the relative efficiency and convenience of how the source – electrical energy – is transported from wherever it is generated to the wheels of your car.

In the case of battery vehicles, our existing power grid is used to transport the electricity to your home or wherever else you then charge your car’s battery.

In the case of a hydrogen powered vehicle, there are hydrogen producing plants at various places around the country, and if hydrogen became more widespread as a fuel, there would of course be further plants established.  Unfortunately, unlike gasoline, the hydrogen – in liquid or highly compressed gaseous form can’t be piped to fueling stations, due to its enormous pressure.  Instead, it needs to be trucked, and then stored in tanks at filling stations – all somewhat analogous to how regular petrol and diesel gets to filling stations at present, but without the pipelines efficiently connecting the major sources and distribution points.

Hydrogen distribution systems are clearly less efficient than the electrical grid, and there’s another inefficiency that is obscured but important.  There is also an energy cost associated with either compressing the hydrogen from regular air pressure to its storage pressures, or liquefying it.  Hydrogen tanks in cars are typically rated for a maximum of either 5,000 or 10,000 lbs per square inch of pressure – and of course, the higher pressure tanks allow more hydrogen to be stored.

As a comparison, a SCUBA air tank for a diver usually has air pressures of between 2,000 and 3,500 psi.  Less obvious is that hydrogen can leak more readily than air, because its molecules are very much smaller than nitrogen and oxygen molecules.  So a hydrogen tank and transfer system is not only at very much higher pressure, but the hydrogen can and will leak much faster, too.

The cost of compressing hydrogen to these types of pressures is considerable, and even the small losses due to leaks and inefficiencies becomes measurable.

So let’s look at the actual differences in efficiencies in terms of how much driving you can get per kWhr of electricity, whether it be via a fuel-cell or battery type system.

The Numbers Don’t Lie

If we start off with 100 kWhr of electricity, in the case of a battery powered vehicle, you could expect to lose about 10% of those 100 kWhr in the charging process, and another 10% in the battery.  In other words, if you had three watt meters – one before the charger, one between the charger and the battery, and a third between the battery and its motor, you would first see 100 kWhr go into the charger, then you’d see 90 kWhr come out of the charger and go into the battery, and then you would finally see 80 kWhr of electricity come out of the battery and go into the motor.

In the case of a fuel cell powered vehicle, if we start off with 100 kWhr of electricity, we can either convert natural gas to hydrogen or we can electrolyze water.  Natural gas is – ooops, a non-renewable hydrocarbon, and also has a cost associated with it, so let’s assume instead we electrolyze the water, which is less expensive (but pure water is seldom free).  This is about a 75% efficient process, so we have about 75 kWhr of hydrogen after the electrolysis (yes, I know, that’s a really strange way of measuring hydrogen!).

Now we want to pressurize it.  Liquefaction is actually more energy costly, so we’ll look at compressing.  That’s a 10% energy cost, bringing us down to 67.5 kWhr.

Now we need to truck it to a filling station.  That is probably about a 20% energy cost, so we’ve now got 54 kWhr of net electric energy equivalent remaining.  We fill our car (and will ignore the small loss in this process) and then use the fuel-cell to convert it into electricity, ready to go into the motor, the same as if it came out of a battery.

A perfect fuel-cell can theoretically reach 83% efficiency.  But a real world one seems to run about 50% efficient (due mainly to thermal losses).  So our 54 kWhr of hydrogen ends up giving us 27 kWhr of electricity into the motor.

And that is the fatal problem which hydrogen can never resolve.  Using batteries means that we have an 80% efficient process.  Using hydrogen means we have a 27% efficient process.

(Note – we are ignoring losses/inefficiencies in the electrical transmission lines, and also in the vehicle’s electric motors, because those issues are very closely the same for both battery or hydrogen/fuel-cell systems.)

Looking Into the Future

It is possible that in time, some of the hydrogen steps can be slightly optimized, but even if we were to get closer to impossible perfection at each step of the process, we’re unlikely to go much over 50% efficiency.  Meantime, there are opportunities to improve on the efficiency of the battery process too, although with an already very high 80% efficiency, these optimizations won’t be enormous, but can be realistically expected to perhaps take the overall process up to an 85% efficiency, possibly even slightly higher.

So, in round figures, currently a battery based power source is about three times as efficient as a hydrogen based power source, and even in the future, is likely to remain twice as efficient.

The cost and convenience factors of battery based vehicle power systems can be expected to continue improving.  Not only is there steady incremental improvements in Li-ion battery technology, causing their cost to reduce, their energy density to improve, their recharge-cycle capacity to increase, and the speed at which they can be recharged to also increase, but there are new battery technologies at various stages of development that promise major leaps forward.

Solid state batteries promise to be half the size of Li-ion batteries, capable of being fully charged in a single minute.  It would be very difficult to supply electricity at this rate from the power grid, but perhaps super-capacitors will help smooth the load, and if the recharge speed is slowed down five-fold or more to a rate comparable to pumping petrol, then the grid pressures will greatly reduce.  Solid state batteries also promise a longer life – perhaps 100 times more charge/discharge cycles than current Li-ion batteries before suffering appreciable reduction in capacity.

These new batteries are not yet in commercial production, but may become practical in about five years time.  Interestingly, Toyota is one of the champions of solid-state batteries – clearly it sees a future where its fuel-cell technology may no longer be relevant.

It is foreseeable that within a decade, not only will a battery powered vehicle be at least twice as fuel-efficient as a fuel-cell vehicle, but its battery pack will be smaller, lighter, and less expensive than the hydrogen tank and fuel cell in a fuel-cell powered vehicle, while having longer range and being capable of being recharged more quickly than either fuel-cells or regular petrol/diesel vehicles.

Our point is that not only is there no remaining opportunity for fuel-cell powered vehicles today, the future sees their niche market getting smaller and smaller.

But what if electricity were free, or so low in cost as to make the different efficiency levels irrelevant?  That doesn’t address the other benefits of a battery powered vehicle, but let’s still consider this possible future, which is actually more likely than you might think.

What if Energy is Free?

Believe it or not, there are times every day when in much of the world, energy is indeed close to free.  These are times when renewable energy sources (mainly solar and wind) are generating more electric power than the region they serve is consuming.  At present, the rest of the energy they produce is just wasted – if you don’t use electricity as and when it is generated, you lose it.

There are some elaborate way of storing electricity – perhaps in enormous battery banks, or maybe by running a hydro-electric power station in reverse, pumping water uphill and storing it in the lake above until it is needed, then running it back down and through the generators.  There is growing interest in such systems due to the growing use of renewable (but uncontrollable) energy sources.  Storing surplus energy could then be used when solar stops generating at night, etc.

So, with the continued growth of renewable energy generation, there will be more occasions when there is ‘free’ spare or waste energy.  Could we use that energy, at those times of days, to then create hydrogen almost for free?

Yes, we could, but we could also use that ‘free’ energy to top up our car batteries.  Increasingly we are seeing utilities developing ‘smart metering’ type technologies and demand-based pricing that allow them to direct surplus energy into ‘discretionary’ uses such as battery charging, or into an energy storage system, and which encourage electricity uses to shift their usage from peak periods to off-peak.

Whether or not the electricity is free, it will always be desirable to get twice the use from it.  Only if or when all energy is always free and abundant, at all times of day, every day, will it no longer matter how efficient the storage and subsequent use of that energy is.

One could also argue that even if we always had ‘too much’ energy, we should still be careful at its use.  If we can reduce the infestation of wind turbines, wouldn’t that be a nice thing?  And while there might be ‘too much energy’, it isn’t actually truly free, even if it is solar or wind sourced.  The capital costs of such generating facilities are definitely not and never will be free, it is only the variable costs that sometimes go down very low.

In other words, no matter what the cost of the energy, being able to drive twice the miles per unit of energy is always going to be a good and valuable thing.

Summary

Fuel cells are an interesting technology that once held a lot of promise, but has been obsoleted by the rapid advances in battery capabilities and costs.

Even a theoretically perfect fuel-cell based vehicle will still be only half as efficient as a battery based vehicle.  In terms of operating cost, the differential may become even greater.

Most of the interest and funding for fuel-cell vehicles is the result of state and federal incentives.  These would be better redirected to battery powered technologies and vehicles, and currently these incentives are encouraging the development of obsolete technology that now is only justifiable based on the presence of such incentives.

Resources

Here are some sources for the information in the article above.

Cost per Mile of Hydrogen/Fuel Cells

https://www.cars.com/articles/fill-er-up-refueling-the-2016-toyota-mirai-1420690448036/

Improvements in Li-ion batteries

1991 – 2005 http://grist.org/article/are-the-batteries-ready-100-clean-energy-requires-progress-on-storage/

2010 – 2016 https://www.dvhardware.net/article65919.html

Comparable Energy Efficiencies

https://www.greenoptimistic.com/hydrogen-cars-efficiency/

Future of Batteries

https://www.androidauthority.com/lithium-ion-vs-solid-state-battery-726142/

https://electrek.co/2017/11/14/fisker-solid-state-battery-breakthrough-electric-cars/

  2 Responses to “The False Promise of Fuel-Cell Vehicles”

  1. The government is funding fuel cell technology for much the same reason they were funding electric cars in the golden age of fossil fuel driving. It’s the same reason they were funding self driving cars in the 1980s. No one really knows the technologies of tomorrow. Governments have to hedge their bets. If they only cared about stuff that was ready for commercialization, we’d never half most of the technologies we have today.

    Fuel cell technology may be a dead end, but they said that about electric cars in 1915. Fuel cells and flow batteries are related technologies, and flow batteries might wind up the default storage system for utilities. Right now, lithium based utility power storage has the edge, but it’s good to know someone is wasting money on a chance to find something even better.

    • Hi

      I’m a strong believer in both pure and applied research, so it is awkward for me to argue against any sort of research, even into hydrogen fuel. But, having said that, there are a couple of points that should be understood.

      First, I don’t think the govt is investing into research. It is simply subsidizing the sale of hydrogen powered/fuel cell vehicles and the establishment of a distribution system for hydrogen. That does nothing at all to help hydrogen become cost effective. It is like the saying ‘give a hungry man a fish, and tomorrow he is hungry again; teach him how to catch fish, and he’ll never be hungry again’.

      Second, even if there were to be major investment into how to obtain and distribute hydrogen more cost effectively, and how to make fuel cells more efficient, there is little apparent hope of improvements. The problem is one of theoretical limits and unavoidable chemical/physical ‘conversion costs’.

      Yes, I’m very uncomfortable making such didactic statements, because they are often proved wrong, in many fields. But there is no evidence of any possible new methods or breakthroughs in the field of fuel-cell/hydrogen power.

      Finally though, a qualified word of encouragement to hydrogen enthusiasts. The one potential value for hydrogen is as a means of storing electricity. If there are electricity generating surpluses from renewable energy (solar/wind), and there sometimes are, why not use the spare/free electricity to make hydrogen.

      But, as already discussed in the article, even that argument has an answer. Why not make hydrogen with ‘free’ electricity? Because you can store the free electricity more efficiently and at lower cost in batteries.

      So, no matter what the scenario, I don’t see a future for hydrogen based fuels.

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