Hydrogen (H2) is the lightest element on the periodic table and is the most abundant chemical substance in the universe. In 1766, Henry Cavendish was the first to recognise that hydrogen produces water when burned, a property which later gave it its name: in Greek, hydrogen means “water-former”.
The main concern with hydrogen safety is flammability, and hydrogen has, after acetylene, the widest explosive/ignition mix range with air of all gases. This is, however, mitigated by the fact that hydrogen, due to its low atomic weight, rapidly rises and disperses before ignition. Unless accumulated in an enclosed, unventilated area, hydrogen is very unlikely to induce serious risks.
Elestor’s storage systems incorporate a number of parallel and independent safety systems to ensure safe use of hydrogen:
- All storage systems are equipped with forced ventilation in the hydrogen area, to make sure that any present hydrogen escapes and disperses easily.
- The presence of hydrogen is continuously monitored by dedicated sensors, which can shut down the hydrogen circuit instantly, even at very low concentrations.
- The pressure in the hydrogen reservoir is continuously monitored to immediately detect any leakage, after which the system can be shut down instantly.
- The hydrogen circuits and cell stacks are physically isolated from all electronic circuits, as well as from the bromine subsystem.
Bromine, from ancient Greek, meaning “stench”, is a chemical element with symbol Br, and atomic number 35. It is a halogen.
Free bromine does not occur in nature, but occurs as colorless soluble crystalline salts, analogous to table salt. The high solubility of bromide ions has caused its accumulation in the oceans, where it is abundantly available. Commercially, the element is easily extracted from brine pools, mostly in the United States, Israel and China.
Elemental bromine is a red-brown liquid at room temperature. It is corrosive and toxic, with properties between those of chlorine and iodine. The major applications of bromine are as water purifier/disinfectant in swimming pools and hot tubs, and as flame retarders in all kinds of fabrics. Another key use of bromine compounds is in the manufacturing of pharmaceuticals: Brominated substances are important ingredients of many over-the-counter and prescription drugs, including analgesics, sedatives, and antihistamines.
Elestor’s storage systems incorporate a number of parallel and independent safety systems to ensure safe use of bromine:
- The use of specially designed double-walled reservoirs provides maximum protection in case of mechanical shock.
- The use of a chemical neutralising agent, in which the electrolyte reservoirs are submerged.
- Addition of a so-called Bromine Complexing Agent (BCA) to prevent the bromine from fuming, in the unlikely case that bromine would come in direct contact with open air.
To guarantee proper use and safe handling, Elestor has entered a close cooperation with the world’s largest supplier of bromine, ICL Industrial Products, who prepared below promotional movie about the unique advantages of Bromine for electricity storage purposes:
Approval Dutch authorities
In October 2015, Elestor installed its first GEN1 pilot system in the field connected to the offices of Witteveen+Bos in the city of Deventer, the Netherlands.
Apart from the need to demonstrate the proper working of the flow battery under real conditions, the necessity to seek formal approval from the authorities in an as early as possible stage was clearly acknowledged.
Prior to every subsequent installation of a GEN2 system, Elestor passed the safety procedures as defined by the local and provincial authorities, even for applications in a built environment. For one of the pilot systems, approval was received for in-house installation.
The Elestor system design therefore fulfils formal Dutch safety criteria.