Rising CO2 emissions from the combustion of fossil fuels are the single largest contributor to global warming. In the UK alone in 2019, domestic transport was responsible for emitting the equivalent of 122 million tonnes of CO2, equating to 27% of the UK’s total emissions in 2019 (455 million tonnes CO2 equivalent). Whilst most countries are transitioning to renewable energy sources for power generation with a paradigm shift occurring in the light-duty mobility sector regarding the switch to Battery Electric Vehicles (BEVs), the low energy density, charging infrastructure, and safety concerns regarding the use of liquid electrolytes within modern lithium-ion batteries have stagnated their implementation somewhat.

Hydrogen is an interesting material that has gathered momentum recently for use in Fuel Cell Electric Vehicles (FCEVs) due to its high energy density and availability. However, whilst hydrogen is the third most abundant element on earth (after oxygen and silicon) it does not tend to exist in isolation and is instead combined with other elements. Therefore, to separate hydrogen into a standalone element for use elsewhere, significant quantities of energy are required. Water is typically used as the starting compound where hydrogen gas is extracted from the water using a technique known as electrolysis. This involves running a high electric current through water to separate the hydrogen from the oxygen. If electrolysis can be undertaken using renewable energy sources, however, the electrolysis technique can be classified as carbon-neutral resulting in a carbon-free, sustainable, and renewable end-product.

Benefits and Shortfalls of Hydrogen for Fuel Cell Vehicles

Hydrogen is a valuable source of energy for a variety of reasons, the most important of which is its abundant supply. While it requires significant amounts of resources to harness, no other energy source is as limitless. When hydrogen is used as a fuel in FCEVs there are zero harmful emissions produced – only water vapour and warm air. Hydrogen has an energy density approximately three times that of diesel or gasoline and over one hundred times that of the latest lithium-ion batteries. This indicates that in theory, a vehicle powered by hydrogen energy will drive further than one powered by gasoline, diesel, or batteries.

The two main methods of extracting hydrogen are electrolysis and steam reforming with both being significantly expensive from a cost and energy required perspective to implement. This is one of the main reasons for impeding market penetration. Today, hydrogen is mostly used to power FCEVs. However, one of the biggest limitations is its low density which means it must be compressed to high pressures or stored in large volumes to be practical from a user perspective. High-pressure storage tanks carry inherent dangers making transit and frequent usage impractical. The potential hazards associated with hydrogen should not be underestimated. Although gasoline is marginally more hazardous than hydrogen, hydrogen is highly combustible and volatile and frequently creates headlines due to its potential hazards. In comparison to natural gas, hydrogen has no odour, making leak detection almost impossible. Sensors must therefore be installed to detect leakage.

Latest Developments in Onsite Hydrogen Production

In late 2021, Octopus Hydrogen, Octopus Renewables, and MIRA Technology Park (MTP), UK, announced plans to build a green refuelling forecourt at MIRA Technology Park that will provide hydrogen refuelling and Electric Vehicle (EV) charging to support the needs of the fastest-growing cluster of automotive and mobility technology businesses powering the mobility revolution. The solution created by Octopus combines the group’s hydrogen business, which focuses on offering green hydrogen-as-a-service to accelerate uptake, with Octopus Renewables, which will supply power from a purpose-built 7MW ground-mounted solar array positioned alongside the MTP forecourt. Octopus’ new on-site generator will provide enough green hydrogen to MTP’s enterprises to sustain the equivalent of 60 automobiles’ (FCEVs or ICEs) worth of fuel each day – approximately 400kg. On the forecourt, several high-power EV chargers capable of providing up to 300kW will be installed, adding to the existing network of over 70 charging sites within the MTP.

ITM Power, UK, manufacture and supply on-site hydrogen generation systems using their ground-breaking Proton Exchange Membrane (PEM) electrolyser to produce green hydrogen for refuelling FCEVs. Their PEM electrolysers use renewable electricity and water to produce green hydrogen via an electrolysis process. Green hydrogen produced can be stored as a gas or liquid and discharged into the gas grid, utilised as clean vehicle fuel, or in a variety of industrial operations, thereby decreasing carbon emissions in logistics and the heavy industry significantly. PEM electrolysers have the advantage of being able to respond rapidly to fluctuations in demand compared to typical renewable energy generation techniques, since they can be started in seconds. In comparison, alkaline water electrolysis takes significantly longer to instigate, making the PEM technique perfect for grid balancing and managing energy deficits.

In mid-2021, a breakthrough technique that produces hydrogen from conventional natural gas or renewable natural gas derived from biomass was developed to propel California’s hydrogen highways, FCEVs, and heavy-duty vehicles. The technique developed at the US Department of Energy’s Pacific Northwest National Laboratory (PNNL) is based on small heat-transfer tubes approximately the width of a credit card. These microchannels are crucial for efficiently directing energy into the chemical reactions that generate hydrogen for transportation, electricity generation, and other industrial applications. The PNNL-developed hydrogen generator was licensed to a cleantech start-up company, STARS Technology Corporation, located in Richland, Washington, USA. Since the STARS system can manufacture hydrogen anywhere natural gas is accessible, its inventors believe it will significantly minimise the requirement for hydrogen to be transported in special high-pressure tube trailers. Eliminating on-road transit enhances public safety, reduces greenhouse gas emissions, and contributes to the cost-competitiveness of point-of-use hydrogen production with conventional fuels.

BayoTech, located in Albuquerque, New Mexico, USA, has developed a system using steam methane reformers that use less energy than standard hydrogen manufacturing methods. BayoTech’s patented design harnesses high heat recovery to produce improved energy efficiency, building on technology previously developed by Sandia National Laboratory, USA. Their innovative reformer consumes 20-30% less energy, saving money and lowering the overall carbon footprint. These small modular systems link to existing natural gas pipelines or co-located biogas resources to generate up to 1000kg of hydrogen per day, enough to power up to 200 FCEVs. Larger units with capacities of 5-10 metric tonnes per day are now being developed to accommodate the expanding hydrogen market.

SimpleFuel is an on-site hydrogen generation, compression, storage, and fuelling appliance that generates high purity fuel cell-grade hydrogen using water and power predominately for use in FCEVs. SimpleFuel converts approximately 15 litres of filtered water into enough hydrogen fuel to power a FCEV for more than 360 miles. SimpleFuel is a cost-effective, safe, and dependable fuelling solution developed by a consortium of technology innovators including PDC Machines, Ivys Energy Solutions, and McPhy North America to address specific needs of the hydrogen infrastructure in automotive and industrial mobility applications.

Summary

Hydrogen is a very promising, zero-carbon fuel that can be used for all parts of the transportation sector either in ICEs or FCEVs. The global hydrogen generation market is expected to grow at a Compound Annual Growth Rate CAGR) of 9.2% from an estimated US$130 billion in 2020 to US$ 201 billion by 2025. The increasing application of fuel cell power generation is driving market expansion. If hydrogen can be produced and stored using energy provided from renewable sources, it is a real alternative to adopting batteries for light to medium duty vehicles for propulsion – either hydrogen ICEs or FCEVs. Furthermore, with a plentiful supply of hydrogen, homes could utilise this gas as part of central heating systems, replacing traditional carbon-based gases.