The Truth about Hydrogen

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This episode of Real Engineering is brought to you by Skillshare, home to over twenty thousand classes that could teach you a new life skill. As the world grapples to eliminate fossil fuels from our energy diet, electric cars have seen an incredible boom over the past few years. Last year, over one million electric cars were sold around the world. The number of Nissan Leafs, Teslas, and other electric vehicles in circulation worldwide is now more than three million. And while there are many brands of electric car to choose from, there are only two choices when it comes to powering electric vehicles: fuel cells or batteries. Both produce electricity to drive electric motors, eliminating the pollution and inefficiencies of the fossil fuel powered internal combustion engine. Both hydrogen and electricity for batteries can be produced from low­ or zero ­carbon sources, including renewable energy like solar and wind, and therefore both are being pursued by car manufacturers and researchers as the possible future of electric vehicles. However, a great debate is being waged by supporters of each technology. Elon Musk has called hydrogen fuel cell technology “incredibly dumb,” claiming they’re more of a marketing ploy for automakers than a long-term solution. In contrast, Japan has announced its intention to become the world's first hydrogen society, with the Japanese government and the auto industry working together to introduce 160 hydrogen stations and 40,000 fuel-cell vehicles by March 2021. So which is actually better? At first glance, hydrogen seems like an extremely clever way to power a car. Compressed hydrogen has a specific energy (aka energy per unit mass) of neary 40,000 watt hours per kilogram. Lithium ion batteries at best have a specific energy of just 278 wh/kg, but most fall around 167 wh / kg. That's 236 times as much energy per kg for hydrogen. And because of its energy density and lightweight nature, compressed hydrogen and fuel cells can power cars for extended ranges without adding much weight, which as we saw in our last video is a gigantic road block for incorporating the technology into the aviation industry. The designers of electric vehicles are caught in a catch 22 with energy density and range. Each extra kilogram of battery weight to increase range requires extra structural weight, heavier brakes, a higher torque motor, and in turn more batteries to carry around this extra mass, This weight compounding limits how far a battery powered vehicle can travel, until new technology can help reduce the weight of the batteries. For hydrogen fuel cell vehicles, this weight compounding is not an issue. Additionally, a hydrogen fuel cell vehicle can be refueled in under 5 minutes, where a battery powered electric vehicle, like the Tesla model S, takes over 3 hours to fully recharge. When looking at the range and refuel times hydrogen can offer, you can see why some car manufacturers are investing in this technology. On the face of it. Hydrogen is a clear winner, but it falls behind when we start considering the end-to-end production process. While both batteries and hydrogen fuel cells are both forms of electricity storage, the cost differ drastically. Fully charging a Tesla Model 3 with a 75 kiloWatt hour battery, costs between 10-12 dollars depending where you live. With a rated range of 500 kilometers, that’s between 2 and 2.4 cent per kilometer. A great price. In a previous video, I visited a petrol station that introduced a hydrogen pump, fed by its own on-site production facility. which used off-peak electricity to produce hydrogen. The hydrogen from this station cost $85 dollars to fill the 5 kg tank of the Toyota Mirais on site, which had a range of 480 kms. That’s 17.7 cent per kilometer, 8 times the price. And here lies the problem, Hydrogen simply requires more energy to produce. To understand the economic viability of hydrogen let’s dig deeper into the production process. Before any hydrogen vehicle can hit the road, you first need to produce the hydrogen, but hydrogen is not a readily available energy source. Even though hydrogen is the most abundant element in the universe, it is usually stored in water, hydrocarbons, such as methane, and other organic matter. One of the challenges of using hydrogen as an energy storage mechanism comes from being able to efficiently extract it from these compounds. In the US, the majority of hydrogen is produced through a process called steam reforming. Steam reforming is the process of combining high-temperature steam with natural gas to extract hydrogen. While steam reforming is the most common method of industrial hydrogen production, it requires a good deal of heat and is wildly inefficient. Hydrogen produced by steam reforming actually has less energy than the natural gas that the steam reforming began with. And while hydrogen fuel cells themselves don’t produce pollution, this process does. So if we want to assume a future scenario with as little carbon emission as possible, this method won’t cut it. Another method to produce hydrogen is electrolysis - separating the hydrogen out of water using an electric current. While the electricity needed for this process can be provided from renewable sources, it requires even more energy input than steam reforming. You end up losing 30% of the energy from the original energy put in from the renewables when you carry out electrolysis. So we are sitting at 70% energy efficiency from hydrogen fuel cells if traditional electrolysis is used, before the car even starts its engine. A slightly more efficient method of producing hydrogen is polymer exchange membrane electrolysis. Using this method, energy efficiencies can reach up to 80%, with the added benefit of being produced on site, which we will get to in a moment. But this is still a 20% loss of energy from the original electricity from the renewables. Some experts say the efficiency of PEM electrolysis is expected to reach 82-86% before 2030, which is a great improvement, but still well short of batteries charging efficiency at 99%. [1] A 19% difference in production costs doesn’t explain the difference in costs yet, so where else are we losing energy. The next hurdle in getting hydrogen fuel cell vehicles on the road is the transport and storage of the pure hydrogen. If we assume the hydrogen is produced on site, like it was for this petrol station, then we eliminate one energy sink, but the cost of storage is just as problematic. Hydrogen is extremely low density as a gas and liquid, and so in order to achieve adequate energy density, we have to increase its actual density. We can do this in two ways. We can compress the hydrogen to 790 times atmospheric pressure, but that takes energy, about 13% of the total energy content of the hydrogen itself. Alternatively we can turn hydrogen into liquid, cryogenically. The advantage of hydrogen liquefaction is that a cryogenic hydrogen tank is much lighter than a tank that can hold pressurized hydrogen. But again, hydrogen's physical properties means hydrogen is harder to liquefy than any other gas except helium. Hydrogen is liquified by reducing its temperature to -253°C, with an efficiency loss of 40%, once you factor in the added weight of the refrigerators and the refrigeration itself. So pressurisation is a better option at a 13% energy loss. Once the hydrogen is produced and compressed to a liquid or gas, a viable hydrogen infrastructure requires that hydrogen be able to be delivered from where it's produced to the point of end-use, such as a vehicle refueling station. Where the hydrogen is produced can have a big impact on the cost and best method of delivery. For example, a large, centrally located hydrogen production facility can produce hydrogen at a lower cost because it is producing more, but it costs more to deliver the hydrogen because the point of use is farther away. In comparison, distributed production facilities produce hydrogen on site so delivery costs are relatively low, but the cost to produce the hydrogen is likely to be higher because production volumes are less. While there are some small-scale, on-site hydrogen production facilities being installed at refuelling pumps, such as the station mentioned in the last hydrogen video. until this infrastructure is widespread, we have to assume that the majority of hydrogen is being transported by truck or pipeline, where we know that energy losses can range from 10% up to 40%. In comparison, assuming that the electricity that we use for charging the batteries comes completely from renewable resources (like solar or wind), we just have to consider the transmission losses in the grid. Using the United States grid as a reference for typical grid losses, the average loss is only 5%. So in the best case scenario for hydrogen, using the most efficient means of production and transport, we lose 20% of energy during PEM electrolysis, and around 13% for compression and storage, amounting to a 33% loss. In other systems, this could be as much as 56%. For battery power, up to this point, we have lost just 6% to the grid and recharging. Bringing our best case efficiency difference to 27% and our worst case to 50%. The next stage of powering electric vehicles is what is called the tank to wheel conversion efficiency. For hydrogen fuel cell vehicles, once the hydrogen is in the tank, it must be re-converted into electric power. This is done via a fuel cell, which essentially works like a PEM electrolyser, but in reverse. In a PEM fuel cell, hydrogen gas flows through channels to the anode, where a catalyst causes the hydrogen molecules to separate into protons and electrons. Once again the membrane only allows protons to pass through it, while electrons flow through an external circuit to the cathode.This flow of electrons is the electricity that is used to power the vehicles electric motors. If the fuel cell is powered with pure hydrogen, it has the potential to be up to around 60% efficient, with most of the wasted energy lost to heat. Like hydrogen fuel cells, batteries also come with inefficiencies and energy losses. The grid provides AC current while the batteries store the charge in DC. So to convert AC to DC, we need a charger. Using the Tesla Model S as an example, its peak charger efficiency is around 92%. The Tesla model S runs on AC motors; therefore, to convert the DC current supplied by the batteries into AC current, an inverter has to be used with an efficiency of roughly 90%. Additionally, lithium ion batteries can lose energy due to leakage. A good estimate for the charging efficiency of a lithium ion battery is 90%. All of these factors combined lead to a total efficiency of around 75%. However, hydrogen fuel cell vehicles also have some of these same inefficiencies. Any kind of electrolysis requires DC current, and therefore, a rectifier will be required to convert the AC current from the grid to DC. The conversion efficiency here is 92%. We also need to convert the DC current produced by the fuel cell to AC to power the motor through an inverter with an efficiency of 90%. Finally, the efficiency of the motor must be considered for both fuel cell and battery powered vehicles. Currently, this is around 90-95% for both of them, which is amazing when you consider that internal combustion engines running on petrol have an efficiency of only around 20-30%. If we add up all these inefficiencies and compare current generation batteries, to the best and worst case scenario of current gen hydrogen. We can see how they measure up. Even with the BEST case scenario. Not taking into account any transport due to onsite production, and assuming very high electrolysis efficiency of 80%, and assuming a HIGH fuel cell efficiency of 80%, hydrogen still comes out at less than half the efficiency. The worst case scenario is even worse off. So while you may be able to go further on one fill-up of hydrogen in your fuel cell vehicle over a battery powered electric vehicle, the cost that is needed to deliver that one fill up would be astronomically higher compared to charging batteries due to these energy losses and efficiencies. Based on our worst case scenario, we would expect the cost per kilometre to be about 3.5 times greater for hydrogen, but as we saw earlier it’s actual 8 times the price. So additional costs of production unrelated to efficiencies are obviously at play. The cost of construction of the facility is one and the profit the station will take from sale is another. For now, these inefficiencies and costs are driving the market, where most investment and research is going into battery powered electric vehicles. So which wins? Both are equally more green than internal combustion engines, assuming equal renewable resources are used to power them. Fuel cells allow for fast fill up times and long ranges; a big advantage. But battery powered vehicles might catch up in range by the time there are enough hydrogen stations to ever make fuel cell vehicles viable. While fuel cells are efficient relative to combustion engines, they are not as efficient as batteries. They may make more sense for operation disconnected from the grid or as we saw in our last video using hydrogen for planes actually could make a lot of sense, but once again that’s a topic for another video. For now, battery powered electric vehicles seem to be the sensible choice going forward in the quest for pollution free consumer transport. As battery-powered cars become more common, we’re also starting to see self-driving cars become the norm. If the job of driver is slowly automated away and consumers have a bunch of free time to read or watch online video, it may be wise to use that opportunity to start learning new skills and Skillshare is great place to do it. You could take this course on Photoshop for beginners and learn a skill that has helped this channel immensely. You may have noticed that we introduced a new thumbnail design the channel. This done in part because the channels views we trending downwards for past 2 months, despite putting extra effort into production quality. We needed to rethink our strategy for branding, and I felt the blueprints strength was that it was easily recognisable as mine, but they all also look so similar it’s difficult to tell when there is a new video. So we got to work in photoshop to use the strengths of blueprint design and build on its weaknesses and we can up with this transitioning effect. Taking designs to reality, which I think fits the theme channel perfectly. We saw immediate effects with the views on our last video jumping 80% compared on our 2 month average. This is the power of illustration and you can learn how to use software like Photoshop and Illustrator on Skillshare These days you can teach yourself pretty much any skill online and Skillshare is a fantastic place to do it. With over 20,000 classes ranging from animation, electronics, programming and much more. The classes follow a clear learning curve, so you just click and watch without having to curate your own learning experience. A Premium Membership begins around $10 a month for unlimited access to all courses, but the first 1000 people to sign up with this link will get their first 2 months for free. So ask yourself right now. What skill have you been putting off learning. What project have you been dreaming of completing, but you aren’t sure if you have the skills to do it. Why not start right now and sign up to Skillshare using the link below to get your first 2 months free. You have nothing to lose and a valuable life skill to gain. As usual thanks for watching and thank you to all my Patreon supporters. If you would like to see more from me, the links to my twitter, facebook, discord server, subreddit and instagram pages are below. I’m about to do a Q&A on the subject matter of this video on my instagram stories, so if you are interested in having some questions answered the link for that is belo
Channel: Real Engineering
Views: 2,852,155
Rating: 4.7327881 out of 5
Keywords: engineering, science, technology, education, history, real, hydrogen, battery, renewable, energy, electric, car, energy density, climate change, fossil fuels, tesla, toyota, honda, vehicle
Id: f7MzFfuNOtY
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Length: 14min 58sec (898 seconds)
Published: Fri Jul 27 2018
Reddit Comments

Weird chart at 2 minutes using both imperial (miles) and metric (kgs).

And according to this chart a vehicle that can do 300 miles should weigh slightly less than 2500kgs when in reality the Model 3 is rated at 310 miles and weighs 1,730kg.

Funnily enough the Hydrogen powered Toyota Mirai weighs 1,850 kg and gets the 312miles.

👍︎︎ 25 👤︎︎ u/Mantaup 📅︎︎ Jul 28 2018 🗫︎ replies

An important point left out - it wouldn't be practical for people to have their own hydrogen generator at home, whereas everyone has electricity in their home already. The 3 hour charging time is a moot point, if you charge your car like your phone, especially during off-peak hours its actually an huge advantage over hydrogen.

👍︎︎ 17 👤︎︎ u/KuyaEduard 📅︎︎ Jul 28 2018 🗫︎ replies

The video sounds so monotonous and confusing.

Per Wikipedia Proton exchange membrane (PEM) electrolyser has 70-80% efficiency. What does that mean?

A theoretical best case scenario to produce 1 kilogram of hydrogen via electrolysis is ~40kWh of energy and 8 liters of water for the electrolysis process itself. Using a 70-80% efficient process (PEM), the electrolysis takes up to 50kWh for 1 kilogram of hydrogen. In order to make it a liquid hydrogen (so it can be stored in the car), we need additional ~15kWh of energy per kilogram for the compression.

That adds up to approximately 65kWh of energy required for producing 1 kilogram of liquid hydrogen.

Toyota Mirai has 5kg fuel capacity, and with it it can go 300 miles. In order to get the full tank, we need 5 * 65kWh = 325kWh of energy.

Tesla Model 3 can go 300 miles with approximately 75kWh of energy. Which means that a Model 3 can go about 1300 miles using the same amount of electricity as a Mirai uses for 300 miles.

From a financial perspective, we should consider the total savings per, for example, 100 000 miles:

To drive a Mirai that much, with the current hydrogen prices ($14/kg), it would cost about $23000.

To drive a Model 3 that much, with the current electricity prices ($0.2/kWh), it would cost about $5300.

For 200 000 miles, it's $46000 vs $10600. That's a lot of savings. Keep in mind that, in some parts of the world, electricity costs as little as $0.02/kWh.

It means that one more car could be bought using the fuel savings alone.

Regarding the charging time:

As some people have already mentioned, an electric car can be charged at home overnight. Or at any parking spot that has a simple 110/220V outlet. The whole infrastructure is already there, it just needs to be improved.

Also, even though a hydrogen car can be topped in 5 minutes, what is a total throughput of a hydrogen fuel station and what is its production rate and capacity? I know that hydrogen stations are often an order of magnitude more expensive than electricity charging stations, but I can't determine the exact proportion while taking into consideration the same amount of miles charged per day.

All hydrogen cars have to be charged at a charging station. How many electric cars have to be charged at fast charging stations (not at home/work), maybe 30% (a wild, wild guess)? Without getting too deep into speculative calculations, I'd say that a 5 minutes waiting time for hydrogen is a very ideal situation. What if, during a rush hour, 100 hydrogen cars arrive at the same time at a station with 4 stalls? Some would wait 5 minutes, some would wait 125 minutes. In order to serve them faster, more stalls would have to be added. Therefore, the production rate and/or capacity of the station would have to be significantly increased. Even with 8 stalls, some people would have to wait for an hour. What if the station can't produce enough to satisfy peak demand? Would stall count and production rate/capacity increase hydrogen costs? I don't know, but it doesn't sound as scalable and reliable as the video might imply.

In the meantime, 70 out of 100 electric cars were already charged at home or at work, and only 30 arrive at the charging station at the same time. They can all be served at the same time on a bit bigger supercharging location.

Keep in mind that EV drivers would put their cars to charge and walk away, while hydrogen drivers would have to stay in their car and move up the queue every 5 minutes.

Where I live, electricity is very cheap ($0.05 on average for households), while gasoline/diesel prices are huge ($1.6 per liter or $6 per gallon). 60% of the gasoline/diesel price is the excise tax. Government can almost randomly control the fuel price via excise, because it hits the drivers/companies only. I imagine the same would happen if hydrogen took over. With electricity, it isn't that easy, because it is a general commodity, and it can even be produced at home. Even if it goes twice as expensive (which would make pitchfork emporium a billionaire), electricity and electric drivetrain would still be far more cheap and practical to use.

👍︎︎ 24 👤︎︎ u/teapotato 📅︎︎ Jul 28 2018 🗫︎ replies

Illustrates the over all efficiencies of battery powered EVs over Fuel Cells when you take large scale production of hydrogen into the equation.

👍︎︎ 9 👤︎︎ u/UrbanArcologist 📅︎︎ Jul 28 2018 🗫︎ replies

Hydrogen isn't a reasonable alternative to batteries for several reasons. Like the video said, it will always be less energy efficient than batteries, but it's also much less convenient for users since you have go to a station to refuel, and carries more safety concerns. Beyond that, the infrastructure costs are much higher, and always will be, and the vehicles themselves are more expensive, though that could change. It doesn't make sense to spend more on a car that is less convenient and more dangerous than a battery powered car.

👍︎︎ 3 👤︎︎ u/thatguy5748 📅︎︎ Jul 28 2018 🗫︎ replies

Toyota started down the fuel cell path when the earth was a different place - Much less focus on renewables and plans by the major oil companies to move to liquid gas products. I remember early versions of the Mirai built into Hylander SUV's... Opening the hood and seeing a fuel cell instead of an engine was cool. In the 15+ years it took to bring the Mirai to market, the world changed.

👍︎︎ 3 👤︎︎ u/6562 📅︎︎ Jul 28 2018 🗫︎ replies

He didn't really point out the inconvenience of having to go somewhere to get juice for your car. Who's going to be willing to give up the convenience of charging at home? No mention of power density either. What's the kW/kg comparison of batteries and fuel cells? Efficiency is nice, but not everyone is looking for the cheapest ride.

👍︎︎ 2 👤︎︎ u/tkulogo 📅︎︎ Jul 28 2018 🗫︎ replies

So many false info in the vid. For being "Real engineering" he said the Tesla needs 3 hours to charge while showing a supercharger station.

Then he says a hydrogen car with a bigger fuel capacity does not weight more. The hydrogen tanks have to grow in volume if they want to have more capacity. Some current hydrogen cars have 3 tanks already.

Had to close video at that point.

👍︎︎ 4 👤︎︎ u/ggclos 📅︎︎ Jul 28 2018 🗫︎ replies

They never mention the re-pressurizing time between hydrogen fill-ups. It takes between 15-20min per car to get the stuff compressed again to fill the next vehicle.

👍︎︎ 1 👤︎︎ u/supratachophobia 📅︎︎ Jul 29 2018 🗫︎ replies
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