Are fuel cells environmentally friendly? Not always

Are fuel cells environmentally friendly? Not always
Two fuel-cell cars have been on the market since 2015: the Hyundai ix 35 fuel cell (above) and the Toyota Mirai (below). A study conducted at Empa concludes that these cars will only become more environmentally friendly than today’s models in the future, once there is hydrogen from renewable sources. Image: hyundai.presscorner.ch

Fuel cells are regarded as the technology of the future for both cars and household heating systems. As a result, they have a key role to play in the switch to renewable energies. But are fuel cells always more environmentally friendly? An international team of scientists headed by Empa performed a series of calculations and reached a conclusion: it depends on the fuel.

In the future, we might be driving fuel-cell cars that burn solar-generated hydrogen. This would make the "zero emissions " a reality. At the same time, small combined heat and power units - also based on - could be placed in our cellars at home. They convert natural gas and biogas into electricity while generating heat as an added "bonus" to warm the building.

Although this is technically possible, does it also make sense for the environment? Empa researcher Dominic Notter teamed up with colleagues from Greece and Brazil to analyze the life cycle assessments for the use of fuel cells: From their production, throughout their entire service life, all the way to their eventual recycling.

How the electricity is generated the key

The result was conclusive: Fuel cells for cars are only ecologically sound if they are able to run on hydrogen from renewable energy sources. It doesn't make any sense to draw electricity from the European power grid, use it to produce hydrogen via hydro-electrolysis and fuel cars with it; the CO2 emissions per kilowatt hour of electricity would be far too high using this method. At present, industrial hydrogen is predominantly obtained directly from natural gas. However, the fuel cell does not really have any environmental advantages with this kind of fuel, either. A car with a combustion engine currently has the edge: The production of conventional cars is less harmful for the environment.

Nor does the fuel cell stand a chance in the eco-comparison with electric cars for now: First of all, electricity is needed to generate hydrogen, which the car tanks up on. Electricity is then produced from hydrogen again in the car. This double conversion significantly reduces the efficiency level. People who use the same electricity to charge the battery in their directly travel more economically and thus in a more environmentally friendly way.

It could be different story in future, however, says Notter. A fuel cell car will become competitive as soon as a company chiefly produces its electricity from solar, wind and hydro power - because the vehicle will guzzle fewer resources during production than a battery-operated electric car, have a far greater range and can be refueled more rapidly.

Combined heat and power units: world champions of energy efficiency

When it came to comparing combined heat and power units, the research team pitted a fuel cell based on state-of-the-art carbon nanotubes against a Stirling engine. This zero-emission machine, which was invented and patented by the Scottish clergyman Robert Stirling in 1816, converts heat into kinetic energy. Both types of combined heat and power unit can be operated with natural gas. The result of the calculation: a slight advantage for the fuel cell as it converts a higher proportion of natural gas into valuable electricity. Anyone who uses it to produce heat and electricity simultaneously exploits 90 percent of the energy contained in the - a huge proportion. Combined heat and power units - regardless of the type - are therefore masterpieces of energy efficiency. The drawback, however: A fuel cell contains rare metals such as platinum, which are becoming increasingly more expensive and might be difficult to obtain in the future; the Stirling engine, on the other hand, can simply be constructed from steel.

Electric cars with EU electricity not more environmentally friendly than gas-powered cars

For their calculations, Notter and his team used the life cycle assessment instrument, which enables the environmental impact of goods and services to be calculated and compared. The researchers calculated the components of the fuel cells from scratch themselves: For the combined heat and power unit, the fuel cell has an output of 1 kW (kilowatts) and is comparable to a Stirling engine, which generates the same amount of electricity. The fuel-cell vehicle in the study has an output of 55 kW and is comparable to a 55-kW, strong electric car and a small, 55-kW, gasoline-powered car.

The result: Taking the current EU power mix as a comparison, with an assumed consumption of 6.1 l/100 km after 150,000 km of mileage, the gasoline-powered compact car is ahead by a nose. The electric car charged with EU electricity produces slightly more environmental pollution - comparable to 6.4 l/100 km of gasoline consumption. Today, a small fuel-cell car that uses EU electricity to generate hydrogen would easily be the worst option. The car would have the same environmental impact as a luxury sports car with a gasoline consumption of 12.1 l /100 km.

However, the could be a key future technology - especially when surplus electricity from wind power and solar energy is stored temporarily in the form of hydrogen and thus becomes accessible for household heating or mobility. Currently, wind farms are simply switched off when there is too much on the market and the eco-energy goes to waste.


Explore further

Hyundai sees green future in hydrogen-powered cars

More information: Life cycle assessment of PEM FC applications: electric mobility and ì-CHP", D.A. Notter, K. Kouravelou, T. Karachalios, M.K. Daletou, N. Tudela Haberland, Energy & Environmental Science, 2015, DOI: 10.1039/C5EE01082A
Journal information: Energy & Environmental Science

Citation: Are fuel cells environmentally friendly? Not always (2015, July 15) retrieved 19 July 2019 from https://phys.org/news/2015-07-fuel-cells-environmentally-friendly.html
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Jul 15, 2015
Too many assumptions here.

With the new advances such as this one:
http://phys.org/n...ml#nRlv, we will not need to use electricity from the dirty European grid for Hydrogen. Liquid fuel reformers can make it as needed from biofuels.

Jul 15, 2015
They should spend their money developing PEM fuel cells to catalyze natural gas. The transport structure is already in place and burning a little hydrocarbon to replace a little gasoline never hurt anyone.

A-GW/A-CC is a fraud. Freeman Dyson

Jul 15, 2015
Fuel cells for cars are only ecologically sound if they are able to run on hydrogen from renewable energy sources.

No shit, Sherlock.

It doesn't make any sense to draw electricity from the European power grid, use it to produce hydrogen via hydro-electrolysis and fuel cars with it

That really depend on when you're drawing the power. If you're drawing the power at times when renewables are creating more energy than the grid can handle it makes a lot of sense to use that excess for hydrogen creation. And since hydrogen is storable it would be an ideal way to get rid of the variability (and a good business, too, because the energy has to otherwise be dumped or sold at below cost)

Electric cars with EU electricity not more environmentally friendly than gas-powered cars

...at current EU energy mix. That mix is changing rapidly. Look at the mix by the time hydrogen powered cars come to market and do the calcs again.

Jul 15, 2015
This comment has been removed by a moderator.

Jul 15, 2015
we will not need to use electricity from the dirty European grid for Hydrogen.


I agree with you gkam, it doesn't make sense making hydrogen (or another synfuel) with a coal-heavy grid. The best interim solution still remains SMR (Steam Methane Reforming) then we could make hydrogen from biomass.
Also, no need for reformers, SOFCs does that in-situ during operation.

the vehicle will guzzle fewer resources during production than a battery-operated electric car, have a far greater range and can be refueled more rapidly.


All the advantages of fuel cells resumed in one sentence.

Jul 15, 2015
LOL "Fuel cells are regarded as the technology of the future for both cars and household heating systems"....LMAO

On what planet? What F'ing moron thinks fuel cells are the technology of the future for cars? They're a miserable failure for light duty vehicles...and a joke compared to CNG for long haul trucking. How do you expect us to take you seriously when you start the article with that assertion? Why don't you go ahead and throw in that we're all going to ride unicorns to work!

Jul 17, 2015
The future of energy is in tech that Solar Hydrogen Trends is developing:
http://www.solarh...nds.com/
Nothing can compare with the efficiency. Only renewables could have less environmental cost.

Jul 20, 2015
Forgive me for asking a very stupid question; but what's the point of making hydrogen fuel from solar energy? When you already have solar energy that's viable enough to use in the production of hydrogen, wouldn't that suggest that electric cars are the way to go? Surely DC high speed charging infrastructure is easier to implement than anything else. Solar panels + batteries (like the ones Tesla is making), and we are done!

Jul 20, 2015
When you already have solar energy that's viable enough to use in the production of hydrogen, wouldn't that suggest that electric cars are the way to go?

Several issues:
1) Cost of storage. The cost of storing via batteries scales by volume (double the energy requires double the batteries). The cost of storing via H2 fuel tanks scales with the surface area (doubling the volume does not double the surface area)
2) Recharge time. Filling up a H2 fuel tank is very much faster than charging batteries.
3) Batteries degrade over time (so do fuel cells, but not fuel tanks)
4) Speed charging (without a buffer) could put a very large load on the infrastructure. H2 can be 'buffered' easily against peak demand (via reservoirs)
5) Fuel cell cars currently have the range advantage over EVs
6) Hydrogen, unlike batteries, can serve as long-term crisis backup structure (like national oil reserves do now).

That said: EVs have enough advantages as to make this not a clear cut case.

Jul 20, 2015
So you use electricity (clean or not) to produce hydrogen to fill up in your car so that it (hydrogen) can eventually produce electricity for your car? Anyone else think this is stupid?

Jul 20, 2015
If you're drawing the power at times when renewables are creating more energy than the grid can handle ..
- AA

Does this ever occur? I'll 'do a Stumpy' and insist on a reference with empirical data.

Jul 20, 2015
Same with your 'several' issues, of which there are six!

Total rubbish and each easily dismissable as the work of a dribbling dimwit unless substantiated by references to reputable sources.

Each of your issues could just be another one of your worthless opinions, right?


Jul 20, 2015
So you use electricity (clean or not) to produce hydrogen to fill up in your car so that it (hydrogen) can eventually produce electricity for your car?

Depends what you want? Do you want long range? Do you want fast refueling? Is weight an issue? If you answer yes to any of these then hydrogen makes sense.
Think about trucking (and shipping!) applications. They need the range. Time is money (they can't hang around for hours at scharging stations every 100km). Batteries are heavy and reduce the amount of cargo you can carry.

Does this ever occur?

5 second google:
http://www.renewa...ity.html

http://www.iowaen...-issues/
(Note that in the latter article it says we are already PAYING OTHERS to take the excess energy off our hands, Now if we could dump that into H2 .... )

Jul 20, 2015
Total rubbish and each easily dismissable

Points 1 and 4 are simple math. How do you easily dismiss math as "pure rubbish"? This I gotta see.
3) Battery degradation: See second comment in this thread from Tesla tech talk
http://www.quora....ome-sort

5) Tesla gives a range of 426km for the model S. The Mirai has 502km on a full tank of H2 (see respective wikipedia entries)

Still: My next car is going to be an EV.

Jul 20, 2015

Depends what you want? Do you want long range? Do you want fast refueling? Is weight an issue? If you answer yes to any of these then hydrogen makes sense.
Think about trucking (and shipping!) applications. They need the range. Time is money (they can't hang around for hours at scharging stations every 100km). Batteries are heavy and reduce the amount of cargo you can carry.


Your argument about range & fueling time is not convincing. Stopping (20-30 min) at a supercharger every 3/4 hours makes sense. I think Tesla has proven the viability of EVs over any other type to a point where it's just obvious that that's the way to go. Only thing left is for other car-makers to stop treating EVs as pet projects and actually advance battery technology. The only reason FC research is even carrying on at this point is simply because big oil stands to lose big in the transition to a solar powered world. Nothing else.

Jul 20, 2015
Total rubbish and each easily dismissable


Point 2) Refueling
Tesla gives a number of 20 minutes to recharge a model S to 50% at a supercharger (again from the wikipedia site). Home charging will take hours.

According to this the Mirai can be refueld in 5 minutes:
http://www.extrem...-do-that

So let me conclude. Your comment about "total rubbish" was total rubbish. And you could have checked all this easily yourself.

Jul 20, 2015
Your argument about range & fueling time is not convincing. Stopping (20-30 min) at a supercharger every 3/4 hours makes sense.

You're not stopping for 20 minutes for a full charge (20 mins is a 50% charge from completely empty). You're stopping every 1-2 hours for 20 minutes.
It's really good if you mostly commute (that's why I want their model 3 as soon as it comes out...providing a supercharger will be built within 20-30km range until then. Currently the closest one is 100km away)
You also have to factor in: if X number of people want to recharge at a supercharger station and X number of people want to recharge at a hydrogen station then the supercharger station (given comparable ranges) has to be 8-10 times larger. Fuel stations already suffer congestion during rush hours. Charging stations...

I think Tesla has proven the viability of EVs

I agree. But I'm not yet sure if hydro isn't better in some (most?) situations. Wet streets may be a problem tho.

Jul 20, 2015
Another thing to consider; hydrogen distribution and storage is not a walk in the park. In fact it's far from it. Another reason why we should be focusing on what we already have working right at the moment. The sun! That's all planet earth ever needed for its energy consumption.

Jul 20, 2015
hydrogen distribution and storage is not a walk in the park. In fact it's far from it.

True about the storage part. Building a hydrogen 'gas station' is certainly more expensive than building a regular gas station.
I don't see the distribution as much of an issue, though. There's no reason why the hydrogen should not be generated at the filling stations themselves. In times of 'overgen' they could run their own hydrogen splitters and energy companies could still make a buck without having to dump or sell at negative prices. Win-win for everyone.
(Even failing that: hydrogen tanker trucks aren't exactly a new technology)

I think hydrogen works perfectly well hand in hand with solar power. We have an overabundance of sunshine at some times. However, battery storage will not be enough to tide over seasonal variations. Hydrogen can be stored for half a year to bringthat overproduction in the summer to where it's needed most (wintertime) at far lower cost.

Jul 20, 2015
Fuel cells are regarded as the technology of the future for both cars and household heating systems.

Yep, that was the marketing slogan 30 years ago, and it's still "true" today.

Jul 20, 2015
I think the number 1 reason why fuel-cell technology is silly has to be the Law of Conservation of Energy. If hydrogen only yields 25% of the energy that goes into making it, then what's the point? Producing hydrogen literally means wasting 75% of the energy you already have. I'm sorry but the benefits of hydrogen-fuel only exist in theory, in the minds of those who stand to benefit from a hydro economy. But in reality, however, hydrogen-fuel makes no (practical) scientific or economic sense. This H2 hype needs to die, it's been 30 years now. I'm tired.

Jul 21, 2015
I think the number 1 reason why fuel-cell technology is silly has to be the Law of Conservation of Energy. If hydrogen only yields 25% of the energy that goes into making it, then what's the point?


The point is economics and resource security.
Because with a purely EV based economy you have to dump excess production. With some H2 in the mix you can at least retain a percentage of that.
Also it makes you resilient against longer lasting problems with the electricity infrastructure. It is never a good idea to have all eggs in one basket. Knocking out power lines - whether from natural causes or due to acts of war/terrorism would kill all mobility almost instantly.

Personally I think the best mix of the two would be flow batteries, With those you can store electricity whenever you need in bulk, fill up quickly, have high efficiency (...and it's even less dangerous during a crash situation than H2 or solid battery EVs because you can't get them to short)

Jul 21, 2015
With some H2 in the mix you can at least retain a percentage of that.

I'd like to make a bit more clear what I mean by this: We should NOT use primary energy production (i.e. electricity that can immediately be used) for H2 generation. We should only use overgen capacity for that (i.e. energy that would otherwise be completely lost)

When we get to the point of having 100% renewables - most of which will be wind and solar - it will be necessary to either have large buffer/storage systems or have significant overcapacity so that enough energy is produced on days where the availability of sun/wind is low. But this means on days with high sun/wind we'll have an overabundance. To me it would make no sense to waste this when there's a perfectly reasonable use for it.

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