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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 technologyincredibly 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

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  • You may have noticed that we introduced a new thumbnail design the channel.

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  • We needed to rethink our strategy for branding, and I felt the blueprints strength was that

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