Decarbonisation Technology November 2026 issue

at a pressure linked to temperature. The system uses that ability to generate hydrogen pressure as part of the process for converting waste heat into electrical power. From the metal hydride reactors, the high- pressure hydrogen is then sent to the stack module, where expansion across JTEC’s electrochemical stacks produces electrical power. After expansion, the low-pressure hydrogen leaves the stack and can be absorbed back into a separate metal hydride reactor in the waste-heat conversion module, where it can later be heated, re-pressurised and used to generate power again. Through this process, JTEC has developed a waste-heat-to-power conversion technology that circulates a single charge of hydrogen in a fully closed loop. No hydrogen is consumed by the system, and waste heat is the only ‘fuel’ the process needs to operate. During passage through the stacks, the hydrogen gas is humidified to keep the membranes in the stacks operating at peak performance. However, excess water exposure can damage metal hydrides by contributing to the development of oxide layers that limit hydrogen absorption and reduce reactor performance. As a result, the process must maintain enough moisture to support stack performance, then dry the hydrogen stream before it reaches the reactors. Humidity measurement is critical to JTEC because its two system parts work well together, but to integrate them, it must tightly control humidity moving back and forth between them. Before selecting Vaisala, it used conventional relative humidity and dew point sensors in lab and R&D work. However, the sensors were not always robust enough for the application, especially when exposed to condensation or saturation events. In R&D applications, a saturated humidity probe forced engineers to stop an experiment, dry down equipment, clean the system, and begin again. In one case, an engineer spent three days trying to complete a six-hour experiment because the sensor saturated partway through the test and the system had to be reset. The risks posed by inaccurate or unreliable moisture measurements are even greater in a production system, where the waste-heat conversion subsystem can represent more

than a third of total system cost and is needed to operate continuously while the system is running. Moisture overexposures can degrade reactor system performance and require offline maintenance for recovery, adding unacceptable downtime to power production infrastructure. Standardising on Vaisala for humidity and dew point measurement JTEC first piloted a Vaisala dew point sensor in an internal R&D project in 2023. As the company worked towards its first production system and field pilot, Vaisala became the preferred option based on low dew point performance, calibration stability, availability, integration flexibility, and technical support. In JTEC’s production system architecture, Vaisala sensors support three critical moisture measurement points. The first is a high-humidity measurement after the initial stage of the dehumidification system. At that point, hydrogen has left the electrochemical stack, and much of its moisture has already been removed. JTEC used a Vaisala HMP7 relative humidity and temperature probe (see Figure 2 ) to confirm system performance and help avoid condensation in the line. The second is a low dew point measurement after the later stages of moisture management. At this stage, hydrogen must be dried back Figure 2 Vaisala HMP7 relative humidity and temperature probe