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Hydrogen – Future Fuel or Folly?

By autotech-nath on March 17, 2024

Transport is the single biggest contributor to the UK Domestic Greenhouse Gas Emissions, in a 3-part series of articles, Andy Crook will examine the role of hydrogen in decarbonising UK Transport.

By Andy Crook, GotBoost AAT AAE FIMI

Battery Electric Vehicles (BEVs) are currently the dominant decarbonising technology for passenger cars and vans. Hydrogen is seen as the solution for aviation, shipping and, potentially, for buses and Heavy Goods Vehicles (HGVs), especially in heavier weight classes or when charging infrastructure and range are considerations.

The Zero Emissions Vehicle (ZEV) mandate required 22% of all vehicles manufactured by carmakers to be ZEVs by the start of 2024, rising to 80% by 2030. The vast majority of which are expected to be BEVs, but is that the best technology?

What is a Zero Emissions Vehicle?

Is it even possible to have a vehicle that does not produce any emissions? The answer depends on where you measure the emissions. The UK Government defines a ZEV as a vehicle that produces 0 grams CO2/km at the tailpipe during the Worldwide Harmonized Light Vehicles Test Procedure (WLTP).

Figure 1: System boundries

Therefore, all BEVs and Fuel Cell Electric Vehicles (FCEVs) are classified as ZEVs. In fact, under this regulation, any vehicle, regardless of drivetrain technology, can qualify as a ZEV, as long as they emit 0 grams CO2/km.

No other greenhouse gases are targeted because currently there are no internationally agreed testing regimes for light vehicles. Therefore, NOx emissions are not currently considered when classifying a ZEV, which means that Hydrogen Internal Combustion Vehicles (HICEVs) could be classified as ZEVs.

The UK government states it is technology neutral and will allow the markets to dictate the best solutions, but this definition of a ZEV does not create a level playing field for all technologies. Zero Emissions at the tailpipe, is not the same as a Zero Emission Vehicle.

This method of emission measurement is called Tank to Wheel and is only part of the total CO2 emissions of the vehicle during its life. Life Cycle Assessment is a method of assessing the CO2 impact of products, including vehicles from the cradle to the grave. Careful consideration is given to each phase of the life cycle, from manufacture to the in-use phase and finally, disposal/recycling.

Figure 2

The use of system boundaries reduces the complexity of the assessment and separates the life cycle phases for convenience and comparison. The whole life cycle is considered, so the true CO2 impact is to be measured, not just tank to wheel emissions.

Well to Tank emission measurements are used to measure the CO2 produced during the production transportation and storage of the fuel. In the case of BEVs, this includes the different methods of generating electricity, known as the ‘Energy Mix,’ see Figure 2. In 2023, approximately 35% of the UK’s electricity was generated by fossil fuels, 36% by renewable energy, and 15% Nuclear, see Figure 3.

Figure 3

It is clear from the electricity generation data, that despite being considered ZEVs, BEVs do in fact produce CO2 emissions. Until the energy mix is 100% decarbonised this will continue to be the case. Grey Hydrogen produced using fossil fuels (steam reforming of Natural gas) also generates significant CO2 emissions, while green hydrogen production from renewables does not.

Life Cycle Assessments

The results of Lifecycle Assessments (LCA) for a vehicle with different drivetrains are shown in Figure 4. Due to the lack of data for recycling the batteries, the end-of-life boundary has not been accounted for. Currently, most batteries are re- purposed and not recycled.

The calculations are based on 200,000 km of driving using the current UK energy mix and the use of Grey Hydrogen. The total CO2 equivalent of the Plug-in Hybrid and the Battery Electric drivetrain is the same 94,000 Tonnes.

Despite not being a ZEV, Plug-in Hybrid technology matches the BEV CO2 emissions, partly due to the CO2 embedded in the battery manufacturing, and the fossil fuels used in the Energy Mix. Once the battery recycling data is made available it will be possible to compare all the technologies from cradle to grave, the smaller batteries used on PHEVs might just tip the balance in their favour.

As the energy mix continues to use more low-carbon generation (renewables & nuclear) the fuel total CO2 emissions for BEVs will reduce. However, the trend for more range means bigger batteries, which means more CO2 during production.

While the petrol engine and FCEV are similar at 132,000 and 129,000 Tonnes of CO2, respectively, the production of green hydrogen could see LCA CO2 emissions from FCEVs reduced to levels below that of BEVs. However, the required infrastructure for green hydrogen production is not yet in place.

Early demand is expected to be driven by bus and HGV applications, which would require a new hydrogen refuelling network. However, the current demand estimates indicate that road transport will not require significant volumes of green hydrogen. The relative costs and benefits of hydrogen vehicles do not add up when compared to electrification.

Future transport demand for green hydrogen is expected to be from the shipping and aviation sectors, not as a fuel but an energy carrier.

Next time, Andy will examine the various uses of Hydrogen as a fuel and an energy carrier for transportation.



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