Friday is here, and the weekly 'A Taste of Science for the Weekend' column is back — issue 63.
This week: how hydrogen vehicles work, and whether they are the true future of the automotive world.
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Using hydrogen as a fuel is an invention that has been around for decades.
In fact, mass-produced cars powered by an electric motor and hydrogen fuel are already on the world's roads today, with one of the most well-known being the Toyota Mirai.
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In its natural form, hydrogen is a molecule consisting of two hydrogen atoms, each made up of nothing more than a proton and an electron.
Hydrogen is a gas, and to convert it into a liquid it must be cooled to minus 253 degrees, or stored in extremely high-pressure tanks (350–700 bar) — the approach used in hydrogen vehicles.
While driving, when the driver presses the accelerator, a small amount of hydrogen is released into a fuel cell that operates on the principles of an electrochemical cell (anode, cathode, and a potential difference between them).
Hydrogen enters one chamber, where a small amount of platinum acts as a catalyst that splits the molecule into 2 protons and 2 electrons, while oxygen is fed into a second chamber. The two chambers are separated by a membrane that allows protons to pass through but not electrons.
The protons travel through the membrane into the oxygen chamber; the electrons, unable to cross it, reach that same chamber via an external circuit — and their flow through that external circuit is the electric current that powers the vehicle's motor.
In the oxygen chamber, the protons and electrons combine with the oxygen to form distilled water, the only byproduct of the entire process, with zero pollution.
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Most hydrogen produced today is 'grey hydrogen' — made from a mixture of methane and steam at very high temperatures, releasing polluting carbon dioxide into the atmosphere.
Blue hydrogen is based on the same production process, but the carbon is captured at the power plant rather than released into the air.
Hydrogen-based transportation is the cleanest form of transport available, but for it to be truly clean it must rely on green hydrogen, produced by the electrolysis of water using renewable energy.
Additional drawbacks include the high costs of building refuelling stations, the high cost of hydrogen itself, and expensive vehicles due to the small market segment. These costs are expected to decrease gradually as demand grows.
Governments such as China are pushing to advance the adoption of hydrogen vehicles both for their environmental and safety benefits, and for their high energy efficiency (40–60%, compared with 20–30% for petrol-powered vehicles) — yet as of today, almost none of these cars are being sold and the number of refuelling stations is negligible.
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There is a strong case for a hydrogen-based transportation future, and it is possible that these vehicles will eventually replace the electric cars we see today.
Despite the advantages of battery electric vehicles, they still rely on a massive battery containing toxic metals, lose significant energy in transmitting electricity from power plants to charging stations, and are notoriously difficult to extinguish in the event of a fire.
If the challenges that still lie ahead can be overcome, hydrogen vehicles will solve all of these problems and deliver a cleaner, quieter, and more energy-efficient world.
Shabbat Shalom 😊
In the video: a hydrogen vehicle manufactured by BMW, planned for mass production in 2028.
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