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Why Hydrogen?

A long read by David Dundas, member of Interest Groups Online's Countdown to COP group 

The UK’s Primary Energy demand is the energy that we consume from all sources; in 2022 it was around 2,000 TWh and electricity supplied around 20% of that 1. Although hydrogen is a powerful energy source, very little energy is presently delivered by it; most is used in the oil and petrochemical industries in the preparation of their products. The Government Hydrogen Strategy published in August 2021 2 predicts that by 2050 up to 35% of our primary energy will be delivered as hydrogen, so how will hydrogen become a major part of our energy consumption?

Hydrogen is a gas that is rare on its own on Earth, but it is very widespread when combined with oxygen as water. Water is a very stable molecule of two hydrogen atoms and one oxygen atom that requires a lot of energy to split it into hydrogen and oxygen; When hydrogen is burnt in air this makes water as steam, releasing a large amount of energy as heat. Hydrogen can also be joined with oxygen from the air in a fuel cell which delivers the energy as electricity. Either way, hydrogen is a powerful source of energy.

Plant life made our air breathable

About 4 billion years ago the first signs of life were protocells 3. The atmosphere was hot and thick with carbon dioxide and little oxygen, so animals couldn’t breathe in it; this primitive plant life started to use photosynthesis to capture the energy of the sun to split water into hydrogen and oxygen; the oxygen was released into the air, gradually making it breathable by animals. These protocells extracted the carbon dioxide from the air and with the hydrogen from water, built plant material to form hydrocarbon plant tissues. Carbon dioxide is a powerful greenhouse gas so the atmosphere was cooled by plants extracting it and turning the atmosphere into one that animals can live in. Plants today do the same thing, extracting carbon dioxide from the air and releasing oxygen as they grow, but as the plants die and rot, this releases methane gas. This then decomposes into carbon dioxide returning it to where it started, completing the cycle.

We were burning hydrogen when we discovered fire

Mankind started burning hydrogen when we discovered fire. We burnt the hydrocarbons in wood and other combustible materials, using the hydrogen in the hydrocarbons and oxygen in the air to make steam; and as the hydrogen has hitched a ride on the back of the carbon in these hydrocarbons they also burn to produce carbon dioxide. If these hydrocarbons are not from plants and wood that grew recently, but come from fossil carbon in coal, oil and gas laid down millions of years ago, we are unlocking the fossil carbon dioxide that was captured years ago that made our atmosphere one in which we can live.

Most vehicles with electric traction have a battery

Most electric vehicles, whether battery (EV) or fuel cell battery electric vehicle (FCEV) save energy when braking or slowing down, when the motor becomes a generator in regenerative braking, returning the power to the battery. In a hydrogen powered vehicle (FCEV) the battery is also needed to provide extra energy when accelerating, but it is small compared with the battery of an EV. Most EV and FCEV vehicles need to store energy on board to power the traction, the exception being trains and trams with overhead catenary supported wires supplying the power. When more and more energy is required to be stored on board, the battery gets heavier and heavier, so for large heavy vehicles that may need to drive long distances, the battery weight can become a significant part of the load, wasting energy in transporting it.

EVs for short local trips, hydrogen EVs for long distance and heavy loads

For small vehicles travelling short distances, battery only is the most efficient, but for heavy vehicles such as trucks pulling heavy loads and buses that need to travel long distances, or trains on lines that are not electrified, then hydrogen-battery power is the better choice. Refilling with hydrogen is much quicker than charging the battery, about the same speed as filling with petrol or diesel. Hydrogen powered cars are a good solution for people living in terraced houses with no driveway to locate a charging point, or drivers who need to drive long distances.

In the UK around 40% of our railways are not electrified as it is very expensive, especially on old Victorian lines with low bridges and tunnels that may need to be rebuilt to provide the space for the overhead catenary wires, when the low traffic volume does not justify the cost. Network Rail has a target to replace all diesel power by 2040 so the least cost solution would be to retrofit existing diesel-electric trains (DMUs) replacing the diesel engines with hydrogen fuel cell electric power. This can be done one at a time as funds allow; trials with passengers have already been completed successfully on main lines: eg Hydroflex converted by Birmingham University and leasing company Porterbrook, and Breeze converted by Alstom and Eversholt Rail.

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