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The University of French Polynesia has built a photovoltaic-powered hydrogen generation unit that combines a hydrogen chain with a thermochemical unit. The latter is used to recover waste heat from the electrolyser and the fuel cell to allow delayed production of cold for air conditioning.
The University of French Polynesia has developed a solar-powered microgrid that supports the generation of hydrogen, which in turn is used to produce electricity and cooling.
The system couples a hydrogen generation chain formed by an electrolyzer and a fuel cell with a thermochemical unit. The hydrogen chain is used as a storage unit, using electrolysis to split water into hydrogen (H2) and oxygen and then converting the H2 back into electricity using a fuel cell. The thermochemical unit is designed to recover waste heat from the electrolyzer and fuel cell to enable delayed production of cold for air conditioning purposes.
“The RECIF installation consists of the following components: a hybrid inverter, photovoltaic panels, a lithium-ion battery pack, a PEM electrolyzer for H2 production, an H2 storage tank, a PEM fuel cell for production of electricity from the stored H2, a controllable electrical load and a custom-made air conditioning system with a thermochemical unit for the storage of thermal energy and the delayed production of cold,” researcher Franco Ferrucci explained to pv magazine, noting that The components are installed in a 6 meter container.
As a solid/gas thermochemical pair, the system uses a barium chloride salt (BaCl2) that reacts with ammonia (NH3), which in turn serves as a cooling fluid in the refrigeration circuit. “This pair has the advantage of being able to operate with relatively low temperature heat sources (55ºC), which makes it compatible with PEM electrolyzers and fuel cells,” the researchers say.
The research group deployed the system in 2018 and questions have since been raised about its security. “The implementation of a facility of this type was very challenging, mainly due to the lack of experience in the territory with this type of facility and an unclear regulatory context in relation to safety systems and explosive atmospheres,” they explained. the scientists.
To resolve these safety issues, the group also developed a safety system aimed at reducing explosion risks related to H2 and NH3 gases. In a small hydrogen installation, the greatest risk can materialize in the event of a hydrogen leak that cannot be detected within a poorly ventilated room.
“Our installation has solar panels that cover an area of ??23m2, and the protection system has 1000 V contactors that disconnect the panels when the security system detects an accident condition, since one of the security actions is to interrupt the production of renewable electricity,” explains Ferrucci.
“In the case of a larger PV installation, it is not practical to disconnect the panels directly, as there is not a wide variety of high voltage DC contactors on the market. In that case, the security system would have to disconnect the inverter so that it cannot supply power to the rest of the installation. Furthermore, there should be a physical distance between the photovoltaic electrical panel and the hydrogen installation,” he adds.
The safety system also includes an electrical cabinet that contains a safety programmable logic controller (PLC), which can disconnect the electrical flow. Another tool used is a forced ventilation system with continuous air renewal and emergency ventilation modes, along with fire extinguishers and smoke detectors.
Additionally, a set of relief values ??is installed in the H2 storage unit, and sensors can monitor H2 levels in the fuel cell and electrolyzer. Additionally, various transmitters can interrupt the power supply to the thermochemical unit when a hazard is detected. All security tools can be controlled and monitored by a control and data acquisition system (SCADA) and a security instrumented system (SIS).
“Broadly speaking, the main objective of the installation is twofold: to supply energy to the electrical load and to maintain an adequate level of thermal comfort within the container in which the components are installed,” explains Ferucci, referring to the security system.
The microgrid concept and the corresponding safety system were presented in the study “ Design and implementation of the safety system of a solar-driven smart micro-grid comprising hydrogen production for electricity & cooling co-generation ” safety of a solar-powered smart microgrid comprising hydrogen production for cogeneration of electricity and cooling.), published in the International Journal of Hydrogen Energy .
“The study establishes the reliability of the gas detection system, affirming its adherence to the SIL-2 safety integrity level based on the risk analysis and recommendations of the company specialized in inspection and certification that supervises the validation of the RECIF installation. ”said Ferrucci. “The simulations carried out demonstrate that the safety system quickly detects and stops any leak inside the container, effectively reducing the gas concentration to negligible levels.” |
