Oceans of potential

2nd October 2020

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Julie Stevens

New innovations in the electrolysis of seawater could create almost unlimited clean energy, says Alan Asbury

The take-up of electric vehicles is increasing across the world, helped by government grants, incentives and the rapid expansion of battery range. The UK government's consultation on the future of transport has already suggested an end to the sale of internal combustion engine and hybrid cars from 2035. However, there are concerns that battery electric vehicles cannot, on their own, replace the internal combustion engine.

The reason for this is that, in the UK, transport currently accounts for only 1% of electrical energy. Already there are difficulties in locating sites for rapid (43kW+) electric charge points that can draw around 100 amps at the commencement of the charge. The UK has around 32m cars on its roads, and this number annually increases by around a million. Indeed, the case for like-for-like replacement of all of these cars is flawed. Technology allows for the booking and collection of cars on a needs basis, and the idea of owning a car that is parked on a road or driveway most of the time is 20th century in its logic. Cars depreciate, and so calling on the right car for the task is surely the sustainable thing to do. COVID-19 has made it clear that reduced car ownership would have a beneficial effect on air quality.

Even with reduced ownership, the grid as it stands could not contend with a fleet calling on electrical power for all mobility needs. Waiting times at charging stations cannot be sustained on a fleet of so many cars. Additionally, most of the 500,000-plus HGVs serving the UK's freight needs could not contend with the loss of payload capacity caused by the introduction of high-mass onboard batteries.

Clean, green hydrogen

Hydrogen has many beneficial transport and heating fuel properties. It fuels rapidly, can be stored in pressurised or solid form, and releases only water as an exhaust product. If it is to be used for heating and transport, it needs to be decoupled from fossil fuels, meaning it must not be derived from natural or landfill gas (predominantly methane). The reasons for this are plentiful: fossil fuels are finite, and their use deprives future generations of the opportunity to use them more wisely; they cause conflict within the destabilised regions where they are often found; and the degradation of the 'non-value environment' through the exploitation of this 'value resource' is unsustainable.

“If hydrogen is to be used for heating and transport, it needs to be decoupled from fossil fuels, meaning it must not be derived from natural or landfill gas“

CO2 has an atomic weight of 44: the atomic weight of one carbon atom, which is 12, plus two oxygen atoms, each with an atomic weight of 16. The amount of carbon in a quantity of CO2 can be found by multiplying the quantity of CO2 by 0.27 (12 divided by 44). Therefore, 1kg of CO2 can be expressed as 0.27kg of carbon.


Producing clean hydrogen from seawater via electrolysis could be the key to the widespread adoption of hydrogen-run vehicles

Methane (CH4) has four hydrogen atoms for every carbon atom. On the surface, this makes methane look like a viable hydrogen generating gas. However, while methane is plentiful, its global warming potential (GWP) is up to 28 times greater than carbon; cracking it leads to the release of carbon that has a lower GWP but stays in the atmosphere for more than a century. The atomic weight of a carbon atom is 12 and the atomic weight of hydrogen is 1, meaning a methane atom's atomic weight is 16. The amount of carbon in a quantity of CH4 can be found by multiplying the amount of methane by 0.75 (12 divided by 16); thus 1kg of methane releases 0.75kg of carbon.

As such, maintaining any future fuel linkage to oil and natural gas will do nothing to limit the effects of climate change. While methane (the major constituent of natural and landfill gas) is relatively plentiful and the carbon that is cracked could arguably be retained through carbon capture and storage, this is only a short-term measure (akin to vitrification and storage of spent nuclear fuels) and the technology is still in its infancy. This is problematic given that the world needs to act in the next 10 years.

Solutions in the sea

The most viable route for accessing hydrogen would be electrolysis from water. While there are approximately 326 million trillion gallons of water on earth, only 3.5% is potable; of this, 68% is held in ice and glaciers, 30% is underground and just 2% is available to us in rivers, lakes and reservoirs. This makes it a scarce commodity, and the idea of fuelling all the world's vehicles from potable water is ludicrous.

Seawater has generally been discounted as an option for hydrogen production. This is because electrolysis – the splitting of water into hydrogen and oxygen with electricity, using positive electrodes (anodes) and negative electrodes (cathodes) placed into water to produce hydrogen at the cathode and breathable oxygen at the anode – has always been problematic with saltwater. The negatively charged chloride in seawater salt corrodes the anode, which limits such a system's lifespan.

However, new research from Stanford University seems to have found a solution. Researchers found that by coating the anode with layers that were rich in negative charges, the layers repelled chloride and slowed down the decay of the submerged and underlying metal. In ordinary seawater electrolysis, the anode typically lasts up to 12 hours before crumbling. Laboratory tests have shown that the addition of anode coatings helps the anode last for more than 1,000 hours.

Hydrogen fuelling canisters

In fact, without the risk of salt corrosion, the device matched current technologies that use purified water, operating at the same electrical currents used in industry today. Since the process produces breathable oxygen, divers or submarines could bring devices into the ocean and generate hydrogen and breathable oxygen deep below the surface of the sea, without having to surface for air.

Time to act

Naturally, the energy source required to conduct electrolysis on the scale required must be renewable. With swathes of wind and solar at overcapacity during evening and summer weekends respectively, the potential to generate and store energy as hydrogen is available and growing. Indeed, √òrsted and ITM Power have recently unveiled an offshore wind turbine that can electrolyse hydrogen offshore.

To stand any chance of avoiding runaway climate change, the time to commit to a technology is now. Short-term solutions that appease the oil and gas industry lobby are not the answer. Green electrolysed hydrogen is the necessary and traversable chasm to be navigated – but it can't be crossed in two short leaps.

Alan Asbury, FIEMA CEnv, is a director of CLS Energy (Consultancy) Ltd.

Picture credit: iStock

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