Hydrogen Fuel Cell

Hydrogen FCEVs are essentially electric buses (hence Fuel Cell Electric Vehicle), but with energy stored in compressed hydrogen tanks rather than in batteries, extending daily range up to 500km. A fuel cell electric bus powertrain typically comprises of a fuel cell stack and storage tanks, in combination with batteries or super-capacitors. FCEVs also have regenerative braking to recoup energy in the same way as BEVs.

Fuel cells are electrochemical cells that convert the chemical energy stored in a fuel (in this case hydrogen) and oxygen (taken from the air) into electrical energy. To achieve sufficient electrical power to propel a vehicle, multiple cells must be compiled into a fuel cell ‘stack’. The leading fuel cell type for automotive applications is the polymer electrolyte membrane fuel cell or “PEM”.


Fuel cell design means they produce a constant power output, so a battery or supercapacitor is needed to act as an intermediary energy store to provide variable levels of power to the motor, as the driver accelerates at different rates throughout the service. As compressed hydrogen is the main energy store, battery packs in FCEVs can be much smaller.

Hydrogen can be produced from a variety of methods, including from fossil fuel based industrial processes to electrolysis of water using renewable electricity. The carbon intensity of hydrogen production needs to be considered when calculating WTW GHG emissions. 

For further information on hydrogen fuel cell buses and infrastructure, please download the Zero Emission Bus Guide.

Download the Zero Emission Bus Guide

Alexander Dennis






Off-Site Refuelling

Case Study: Hydrogen Off-Site Refuelling

Operator: First Bus, Aberdeen

Fleet: 25 x Wrightbus StreetDeck Hydroliner

Infrastructure Provider: BOC

First Bus have introduced twenty-five double deck hydrogen FCEV buses into service in Aberdeen following historic trials. The project saw the rollout of 10 buses, the world’s first hydrogen double deck fleet. These buses were jointly funded by the EU JIVE Project, Scottish Government and Aberdeen City Council and followed by a further 15 vehicles funded as part of the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) JIVE II project.

Aberdeen City Council has invested consistently in developing the hydrogen economy for transport, investing £19m since 2015 in infrastructure and vehicles, creating the world’s first combined hydrogen production and multi-modal refueling station.

The hydrogen is generated via a 1 MW on-site electrolyser operated by BOC. The site is supplied with renewable energy purchased by the council from a local wind farm, ensuring low carbon hydrogen production. This enables each FCEV bus to save a total of 84 tonnes of greenhouse gases per year compared to the previous diesel fleet.

Depot Based Refuelling

Case Study: Hydrogen Depot Based Refuelling

Operator: Metroline, London

Fleet: 20 x Wrightbus StreetDeck Hydroliner

Infrastructure Provider: NEL / Ryze Hydrogen

Metroline and Transport for London (TfL) introduced twenty double deck hydrogen FCEV buses to London in 2021, the first such vehicles to enter service in the capital. The vehicles manufactured by Wrightbus, follow historic hydrogen fuel cell trials in the city dating back many years. The buses were jointly funded by TfL and the Office for Zero Emission Vehicles (OZEV) alongside European bodies including the Fuel Cells and Hydrogen Joint Undertaking, and the Innovation and Networks Executive Agency (INEA), an executive agency of the European Commission.

Transport for London has led the way with rolling out zero emission buses in the UK, with almost 900 such vehicles in service today. Mayor Sadiq Khan has the aim to make all London buses zero emission by 2030. The new hydrogen fuel cell double decker buses are first being introduced on route 7 between East Acton and Oxford Circus, based at Metroline's Perivale depot.

The hydrogen for the buses is currently being produced at Air Liquide’s plant in Runcorn, harnessing waste hydrogen as a by-product from an industrial chlor-alkali plant, while Oxford-based Ryze Hydrogen is responsible for transporting the fuel to the fuelling station. In future, the hydrogen is expected to be produced by electrolysis powered by a direct connection to an offshore windfarm. Danish firm NEL Hydrogen installed a refuelling station on site enabling buses to be refuelled once per day in as little as five minutes.

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