Green Hydrogen Construction: Tilbury Hub to Replace 12 Million Litres of Diesel

Green Hydrogen from Electrolysis to Excavator

Electrolysis is the foundation of the entire green hydrogen supply chain and a concept that A-level Chemistry students will recognise from electrochemistry. Pass a direct current through water, and it splits into its constituent elements: hydrogen collects at the cathode, oxygen at the anode. The minimum theoretical voltage required is 1.23 volts at standard conditions, derived from the Gibbs free energy of water decomposition. In practice, industrial electrolysers operate at 1.8 to 2.4 volts per cell to overcome kinetic and ohmic losses, giving an energy efficiency of roughly 60 to 80 per cent.

GeoPura’s 1-megawatt electrolyser at Tilbury uses proton exchange membrane, or PEM, technology. In a PEM electrolyser, a solid polymer membrane acts as both the electrolyte and the separator between the hydrogen and oxygen sides. Water is fed to the anode, where it is oxidised to produce oxygen gas, protons, and electrons. The protons migrate through the membrane to the cathode, where they combine with electrons from the external circuit to form hydrogen gas. PEM electrolysers respond quickly to variable power inputs, making them well-suited for coupling with intermittent renewable energy sources such as solar panels.

Once produced, the hydrogen must be compressed for storage and transport. At atmospheric pressure, hydrogen occupies roughly 11 cubic metres per kilogram, making it impractical to store in useful quantities. Compression to 350 or 700 bar reduces the volume dramatically but requires energy, typically equivalent to 5 to 15 per cent of the hydrogen’s own energy content. The compressed gas is stored in high-pressure composite cylinders, usually made from carbon fibre wound around an aluminium or polymer liner. A-level Maths students might recognise the thin-walled pressure vessel formula here, where the hoop stress equals the pressure times the radius, divided by the wall thickness. However, at 700 bar, the vessels are decidedly thick-walled, and the analysis is more complex.

On the construction site, hydrogen can be used in two ways. In fuel cells, it reacts with oxygen on a catalyst to produce electricity and water, without combustion. The electricity then drives electric motors in the plant equipment. In dual-fuel engines like the ULEMCO-retrofitted excavator demonstrated at Tilbury, hydrogen is injected directly into a modified diesel engine alongside a reduced quantity of diesel. Hydrogen burns with diesel, displacing a portion of the diesel and reducing both carbon dioxide and particulate emissions.

The engineering challenge for construction sites is logistics. Hydrogen is lighter than air and disperses rapidly if released, which is a safety advantage over diesel or petrol vapour that tends to pool at ground level. However, it is also odourless and invisible when burning, which means leak detection systems and flame detectors must be more sophisticated than those used for conventional fuels. Storage infrastructure must be hardened against impacts from moving plant, and refuelling procedures require careful controls.

For students interested in chemical, mechanical, or environmental engineering, this project sits at the intersection of electrochemistry, thermodynamics, materials science, and construction management. The transition from diesel to hydrogen on construction sites is not just an environmental decision. It is an engineering one, demanding new infrastructure, new safety protocols, and new ways of thinking about how energy flows through a building site.