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An interesting youtube explanation on Hydrogen Fuel Cells.
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Today I want to talk about something light. Hydrogen. Hydrogen is one of the currently most
0:06
popular alternatives to fossil fuel in transport. Many companies and nations have put money into
0:12
it. In 2021, the number of hydrogen-fueled passenger cars bought in the UK was 12.
0:20
Does that sound like a booming business? Not exactly. Indeed,
0:25
a report from the British Science and Technology Committee that just
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appeared last month warned that “we do not believe that will be the panacea
0:33
to our problems that might sometimes be inferred from the hopes placed on it”.
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Ouch. So what’s the deal with hydrogen? Hope or hype? That’s what we’ll talk about today.
0:46
Hydrogen is the first element of the periodic table. If you mix it with
Hydrogen Basics
0:54
oxygen and put fire to the mixture you get water. This reaction releases energy,
0:59
so if you do it under controlled conditions, you can drive a motor or turbine with it. The
1:05
only exhaust you get is pure water, no carbon dioxide, no nitrogen oxides, no particulates,
1:11
no radioactive waste, no chopped-up birds. It’s really difficult to complain about pure water.
1:17
But let’s not give up that easily, certainly we can find something to complain about. For example,
1:23
hydrogen is a gas that, at normal atmospheric pressure and temperature,
1:27
takes up a lot of volume, and it’s somewhat impractical to drag a zeppelin behind your
1:33
car. That’s why to store and transport hydrogen, one compresses it by putting it under a lot of
1:39
pressure. Typically, that’s something like 700 bar, or about 700 times atmospheric pressure.
1:46
At that pressure, the energy that one gets out of one litre
1:50
of hydrogen is one sixth of the energy one gets out of one litre of gasoline.
1:55
This means if you power a car with hydrogen, one needs more litres of hydrogen than one
2:02
needs litres of gasoline to cover the same distance. But litres are a measure of volume.
2:08
The amount of energy you get out of hydrogen per mass is about twice as high as what you get from
2:14
gasoline. Then again, since the hydrogen must be kept under high pressure hydrogen tanks tend to be
2:21
heavy compared to gasoline tanks. When everything is said and done, hydrogen-powered cars end up
2:27
being somewhat heavier than gasoline-powered ones, but it’s not such a big difference.
2:32
Okay, but how do you get the energy out of the hydrogen?
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The technology for this isn’t new, it’s been around for more than 200 years. The
2:43
first hydrogen fuel cell was developed by William Grove in 1839 but it was only in
2:48
the 1960s that two engineers at General Electric proposed a smart way to go about
2:53
it. They developed what’s now called a Proton Exchange Membrane. Those keep
2:59
the hydrogen and oxygen largely separate and allow chemical reactions only at the
3:04
membrane. That way it’s much easier to control the reaction which also makes the system safer.
3:11
Those hydrogen fuel cells were then further developed by NASA. One of the first uses was
3:18
on the Gemini spacecraft, which was launched in the mid-1960s. They were
3:23
later also used on the Apollo spacecraft that carried astronauts to the moon and
3:28
for the space shuttle. The International Space Station uses hydrogen fuel cells
3:33
to generate electricity and also to produce drinking water for the astronauts on board.
3:38
So, hydrogen fuel cells have been around for a long time, but they’ve never been particularly
The Hydrogen Market
3:45
popular. One of the reasons has certainly been that there was simply no need for them, because
3:51
fossil fuels are considerably more convenient. Unfortunately, they have side-effects, which is
3:58
why companies like Hyundai and Toyota have been selling hydrogen-fuelled cars for about a decade.
4:04
BMW, Ford, and other automobile giants have plans for hydrogen cars, and some governments
4:12
are looking at hydrogen to power their transit systems, for example Scotland and Germany.
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The UK with its measly 12 sales in 2021, I admit, is a particularly sad example. For one thing,
4:26
that’s only passenger cars. They also put about 50 hydrogen-powered
4:30
busses on the road. And globally the market doesn’t look quite as dire.
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In total, about 16 thousand hydrogen powered cars were sold in 2021,
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about three thousand 500 of those in the US. The total number of new cars sold in
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2021 was about 67 million, so at the moment it’s about one in four thousand
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new cars that’s hydrogen powered. It’s a small market, but it’s an existing market.
4:58
Some plans are extremely ambitious. For example, in May last year, the European
5:03
Union rolled out a strategy called REPowerEU, with the goal of replacing up to 50 billion
5:10
cubic meters per year of imported Russian gas with hydrogen. This’d mean replacing almost 10
5:16
percent of the EU’s total gas consumption with hydrogen power. That’s substantial.
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It’s not only Europe. Many other countries are also investing in hydrogen production
5:27
facilities, that includes Japan, Canada, Egypt, China, and the United States. For example,
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in March last year, the company Green Hydrogen International unveiled plans
5:37
to create a plant in Texas that’ll use 60 Gigawatt of electricity from solar and
5:42
wind to produce 2 point 5 billion kilograms hydrogen per year. It’ll be called Hydrogen
5:49
City. And Individual companies are investing in it, too. Microsoft, for example, wants to
5:54
use hydrogen fuel cells as climate-friendly backup generators for their data centres.
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As you see, hydrogen is booming. But.
The Colours Of Hydrogen
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The first “but” that might spring to your mind is: But where does the hydrogen come from? Now,
6:10
hydrogen is the most abundant element in the universe. Indeed,
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three quarters of all normal matter in the universe is hydrogen,
6:18
but you normally can’t buy it in the supermarket. So where do you get it?
6:23
Naturally occurring geological deposits of pure hydrogen are rare on Earth. Most of the
6:29
hydrogen we have is bound, either in water or in methane. And this is where the problem begins.
6:35
Because you have to break those chemical bonds to get the hydrogen and that requires energy.
6:41
Hydrogen is therefore not really a source of energy, but a storage system. You use energy
6:48
to create it in its pure form, transport it, and then you release this energy elsewhere.
6:54
How environmentally friendly this is depends strongly on where the hydrogen
6:58
comes from. To keep track of this, scientists are using a colour scale. You all know this,
7:04
but this is YouTube, so I have to say this anyway: The hydrogen itself has always the same colour,
7:09
which is transparent. This colour scale is just a way of keeping track of the production method.
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On this colour scale, the rare, naturally occurring hydrogen is white. Hydrogen obtained
7:22
from water using coal or lignite has the colours black or brown, respectively. Its production emits
7:29
carbon dioxide and methane; both are greenhouse gases. Gray hydrogen is derived from methane and
7:35
water; this also produces carbon dioxide and usually some of the methane escapes.
7:41
At the moment, almost all hydrogen is produced in one of those ways by using fossil fuels. According
7:48
to the World Energy Council, in 2019 more than 95 percent of the hydrogen worldwide was assigned
7:55
one of those colours, black, brown, or grey. This releases about 830 million tons of carbon dioxide
8:02
per year. That’s 2 percent of the total global emissions and about the same as air traffic.
8:08
But there are more colours on the hydrogen rainbow. Next there is
8:13
blue. Like grey hydrogen, blue hydrogen is made from methane,
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but the carbon dioxide is stored underground and does not escape into the atmosphere.
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This method is currently only used for1 percent of hydrogen production, but it could be expanded.
8:29
The industry association Hydrogen Council has touted blue hydrogen as a climate-friendly
8:35
initiative. It’s not entirely irrelevant, so let me mention that this council was created by the
8:40
oil and gas industry. Many of its members have a financial interest in switching from natural
8:46
gas to hydrogen produced from natural gas. So maybe one shouldn’t take their argument
8:52
that blue hydrogen is climate-friendly for granted. Hasn’t someone looked into this?
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Well, since you asked, in 2021, two American researchers calculated the amount of greenhouse
9:04
gases released by grey and blue hydrogen technology. They not only took carbon dioxide into
9:10
account, but also methane, which is a much more potent greenhouse gas. To make comparisons easier,
9:17
the greenhouse effect from methane is usually converted to a carbon dioxide equivalent,
9:22
which is the amount of carbon dioxide that would have the same effect.
9:27
They came to the conclusion that grey hydrogen has a carbon dioxide equivalent of about 550
9:34
grams of carbon dioxide per kilowatt hour and blue only slightly less, 486 grams. That’s about
9:42
the same as the emissions you get from using natural gas directly to generate electricity.
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Part of the reason blue hydrogen performs so poorly is that not all the carbon dioxide from
9:53
hydrogen production is captured and stored. Another reason is that the process of storing
9:59
the carbon dioxide also requires energy and leads to carbon dioxide emissions. The authors estimate
10:05
that under the most favourable conditions, it might be possible to reduce those emissions
10:11
to around 200 grams of carbon dioxide per kilowatt hour by using renewable energy sources.
10:17
So blue hydrogen doesn’t help much with climate protection. Then there
10:22
is green hydrogen, which is produced from water using renewable energy.
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Again that sounds good, and again, it’s not that simple. According to a calculation by researchers
10:34
from Australia, greenhouse gas emissions from green hydrogen produced with solar energy are
10:41
ideally about a quarter of those from grey hydrogen. Under realistic conditions, however,
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they find that emissions are comparable, particularly due to fluctuations in solar
10:51
radiation that make hydrogen production inefficient. There is neither data nor
10:57
any study for hydrogen production from wind but you expect this method to suffer even
11:02
more from fluctuations because wind is far less reliable than sunlight.
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And since these methods are inefficient, they are also expensive. Indeed, producing
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hydrogen with solar and wind is pretty much the most expensive way you can do it,
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according to a review in 2019. Now maybe those costs will go down a bit
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as the technology improves. But seeing that the biggest problem is that energy input
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fluctuates I doubt it’ll become economically competitive with the “dirty” hydrogen.
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This problem can be fixed by using nuclear power to generate hydrogen
11:36
which has been assigned the colour pink and purple. A few projects for
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this are underway but it’s early days and nuclear power isn’t exactly popular.
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Ok, so we have seen that it isn’t all that clear whether hydrogen is climate friendly,
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and also, it’s expensive. And this is only the production cost. It doesn’t include the entire
11:58
infrastructure that’d be necessary to fuel a fleet of hydrogen cars. Remember you have to
12:03
keep the stuff at several hundred bars and you can’t just use a normal gas station for that.
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Let’s move on to the next problem that might come to your mind: where do we get the water
Water Supply
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from? From a distance, the world has no shortage of water, but freshwater can be scarce in certain
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regions of the planet. According to estimates from researchers at the University of Delaware,
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however, water supply issues probably won’t stand in the way of a hydrogen economy. They
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looked at a scenario in which we replace 18 percent of fossil fuels with hydrogen,
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and found that this would require about 2 percent of the amount of freshwater that’s currently used
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for irrigation. Watch out, this figure has a logarithmic scale. You also see on this figure
12:51
that using fossil fuels requires freshwater too, for cooling, mining, hydraulic fracturing,
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and refining, and it’s currently actually more than the projection for hydrogen.
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That’s 2 percent on the global average,
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but in some regions the fraction can be higher. For example, estimates for
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Australia are that you’d need about 4% of the water amount used for irrigation.
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So that seems a manageable amount,
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but it’s something to take into account if you want to make this work.
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Another problem with water is that it can freeze. This is why you shouldn’t leave
13:27
the beer in the car in the winter. And it’s also why hydrogen fuel cells like
13:31
it warm. If the temperature drops more than a few degrees below zero,
The Cold Start Problem
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the water that the fuel cells create at start will freeze immediately, which swiftly degrades
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the membranes and tubes. It’s known as the “Cold Start” problem of hydrogen fuel cell. And, no, you
13:49
can’t just pour antifreeze (not an “ai) into it, remember the water is created in the fuel cell.
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So, you’ll either have to stay in California or keep your car warm.
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The solution that manufacturers pursue at the moment is pre-heating systems.
14:04
But the biggest problem for a hydrogen economy may be making
Rare Metal Shortages
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those proton exchange membranes to begin with. It’s not because it’s so difficult,
14:14
but because they’re made of platinum and iridium. Platinum you may have heard of,
14:19
it’s an expensive noble metal that’s also used for jewellery. The reason it’s expensive is that
14:25
it’s rare. Iridium is also a noble metal. It’s so rare that most people have never heard of it.
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Both of those metals are difficult to replace with anything else in the hydrogen fuel cells.
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That’s a problem because it means that the entire hydrogen economy hinges on the availability of
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those two metals. There’s only so much of those in the world and they are only in very specific
14:49
geological formations. Almost all the platinum and iridium supply comes from only three countries:
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South Africa, Russia, and Zimbabwe, and colonies have gone out of fashion recently.
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China, which has invested heavily in hydrogen technology is already feeling the consequences.
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And we’ve only just barely begun with building the hydrogen economy. This issue has been highlighted
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recently in reports from various international organizations including the International Energy
15:21
Agency and the World Bank. According to the business consulting group Wood Mackenzie,
15:26
the increased demand for platinum might be manageable in the near future,
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but it looks like by 2030 demand for iridium will be several times
15:36
higher than the supply. I don’t know much about trade, but I think this isn’t good.
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It’s possible to make fuel cells somewhat more efficient and decrease the demand
15:45
for those rare metals. But this situation isn’t going to change
15:49
and iridium isn’t going to move to the US even if you ask it really nicely.
Hydrogen Embrittlement
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One final problem that’s worth mentioning is that hydrogen is just nasty to deal with.
16:00
Hydrogen is the smallest molecule. If you squeeze it into a tank,
16:05
it’ll creep into the walls of the tank. That destroys the chemical structure of the
16:11
material and makes it brittle. It’s called “hydrogen embrittlement”. For this reason,
16:16
hydrogen tanks must be thick and specially coated, which makes them both heavy and
16:22
expensive. Like the cold start problem, this one’s basic chemistry and isn’t going to go away.
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And the need to keep the hydrogen under pressure makes the stuff inconvenient to
16:34
handle. The city of Wiesbaden in Germany, for example, recently retired its six new hydrogen
16:40
powered busses because the filling station broke down, sinking a few million Euro.
Summary
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In summary, hydrogen production at the moment has a high carbon footprint because it’s almost
16:51
exclusively done using fossil fuels. Reducing the carbon footprint of hydrogen production
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seems difficult according to estimates, but at the moment there’s basically no real-world data.
17:03
Hydrogen produced by wind and solar will almost certainly not be economically competitive with
17:10
that derived from fossil fuels but using nuclear power might be an option. Building infrastructure
17:16
for a transport-system based on hydrogen would eat up a lot of money. It seems that rare metal supply
17:23
for hydrogen fuel cells is going to become a problem in the near future which won’t help making
17:29
the technology affordable. Keeping hydrogen stored and under pressure ] adds to the
17:35
cost and makes those systems heavy which isn’t great for transport. And finally,
17:40
hydrogen-powered cars don’t like cold temperatures.
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So. Well. It seems to me that the British Science and Technology committee is right.
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A hydrogen economy isn’t a panacea for climate change. Indeed, the French have
17:55
a similar committee that likewise concluded “l’hydrogène n’est pas une solution miracle”.
18:00
I must admit that I was considerably more upbeat about hydrogen before I
18:07
started working on this video. How about you? Did
18:10
you learn something new? Did you change your mind? Let us know in the comments.
18:15
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