Ayrton Energy ($1.7 million to develop membrane-free electrochemical flow reactors for hydrogen storage and transport)

Ayrton Energy, a Canadian hydrogen energy startup founded in 2021, develops low-cost membrane-free electrochemical flow reactors that use liquid organic hydrogen carriers (LOHCs) to store and transport hydrogen gas without the need for cryogenics or high pressure.

Challenges: hydrogen storage

In the pursuit of net-zero emissions, hydrogen is gaining widespread adoption as a promising alternative to conventional fossil fuels. This clean energy carrier provides numerous benefits, such as the potential for production from renewable resources, zero-emission combustion, and high energy density.

Hydrogen is a highly versatile and portable energy source that can be used in a wide range of applications. It can generate electricity through fuel cells or produce heat through combustion, all while having minimal impact on greenhouse gas emissions. Hydrogen is becoming more and more appealing as we move towards a cleaner energy future, thanks to its flexibility and sustainability.

Traditionally, the world has relied heavily on steam methane reforming (SMR) to produce over 60 million tons of hydrogen annually. However, this method comes with a significant environmental cost. It's an energy-intensive process that contributes approximately 2% to global carbon dioxide (CO₂) emissions, releasing between 5 and 9 tons of CO₂ for every ton of hydrogen it generates.

There are cleaner paths to producing hydrogen, such as water electrolysis and methane pyrolysis.

After production, transporting hydrogen to end users is necessary. Transporting and distributing hydrogen can be quite challenging because of its distinct chemical and physical properties. There are safety concerns related to the potential for hydrogen to cause material embrittlement and its tendency to escape from containment. In addition, there are additional risks associated with its wide flammability range and low ignition energy requirement. These factors present significant challenges to the widespread and safe adoption of hydrogen as an energy carrier.

Several solutions have been developed for hydrogen transportation, each with its own set of limitations:

• High-pressure/compressed hydrogen

This method utilizes bulk storage vehicles like tube trailers. However, it faces constraints in transport volume and experiences hydrogen losses, reducing efficiency over long distances. Compressed hydrogen storage and transportation can consume up to 20% of the fuel's energy content.

• Liquid cryogenic hydrogen

This approach is favored for high-volume transport, especially in the absence of pipelines. The process involves cooling hydrogen to below 20K through liquefaction and transporting it in liquid tankers with onboard cooling systems. While effective for large volumes, this method is energy-intensive, potentially using up to 40% of the hydrogen's energy content.

• Adsorption materials

Metal hydrides, which are formed by the chemical reaction of metals and hydrogen gas, provide a highly compact method of storing hydrogen. They are denser than liquid hydrogen and can be stored at normal temperatures and pressures. However, metal hydrides have a relatively low hydrogen storage capacity, ranging from 1-5% by weight. Furthermore, metal hydrides are unsuitable for flow-based transportation methods like pipelines. Metal hydrides are primarily used in stationary applications due to their high energy demand and slow kinetics associated with hydrogen absorption and release.

Ayrton Energy Technology

Ayrton Energy has developed low-cost membrane-free electrochemical flow reactors that use Liquid Organic Hydrogen Carriers (LOHCs) for hydrogen storage and transport.

LOHCs are chemical compounds that can bond and release hydrogen through chemical reactions. Toluene/methylcyclohexane is one of the most common LOHC pairs. Electrochemical reactors for hydrogenation of LOHCs typically employ an electrochemical cell with an anode and a cathode separated by an expensive proton-exchange membrane assembly (MEA).

For example, toluene is used as a LOHC. In a typical electrochemical reactor, hydrogen gas flows through the anode chamber while toluene flows through the cathode chamber. PEM insulates both electrodes and separates hydrogen gas and toluene, allowing only proton products to pass through the membrane.

During the hydrogenation process, hydrogen gas is oxidized at the anode, releasing protons and electrons. Protons pass through the PEM to the cathode, where they react with toluene molecules to produce methylcyclohexane. Methylcyclohexane can be transported in liquid form. When methylcyclohexane reaches the hydrogen demand site, it is dehydrogenated and converted back into toluene. Toluene can then be returned to the hydrogen source site for rehydrogenation.

However, electrochemical reactors with costly proton-exchange membranes are expensive. Furthermore, the leakage of organic reactants and products across the membrane reduces current densities and operating temperatures. LOHCs also cause membrane instability.

Ayrton Energy has developed membrane-free electrochemical flow reactors for either hydrogenation or dehydrogenation of LOCHs. This is accomplished by using a highly conductive emulsion solution containing multiple phases of oil LOCH, water, and hydrogen gas. The presence of multiple phases promotes reactant separation within their respective phases. This lowers parasitic reactions and increases faradaic efficiency. Ayrton Energy's LOHC technology provides a competitive volumetric storage density of 55kg/m³.

How Ayrton Energy stores and transports hydrogen

The diagram below depicts the hydrogen storage and transport system developed by Ayrton Energy.