Sealing a solid oxide fuel cell (or electrolyser) is not simple. There are two main ways to create a seal – one by using a compound that melts and fuses the repeating layers together at high temperature. Alternatively, a compression seal can be used. One of the limitations of glass seals are that they are prone to cracking and cannot handle thermal cycling situations without careful thermal control. If a seal is compromised in any part of the stack it can lead to a gas leak which can diminish the performance or lifespan of the unit or in the worst-case cause failure of the stack requiring an immediate shutdown. 2. The compression seal inside a fuel cell or electrolyser is not simply a gasket, but an engineered component that performs a number of critical functions within the stack: Provide a gas tight seal at very low loads Work from ambient up to operating temperature Cope with many thermal cycles over an extended life of 40,000 hrs or more Electrically isolate the layers to facilitate the current collection and avoid a short circuit Accurately control the gap thickness between the interconnect layers to aid with effective gas flow and proper electrical contact To be thermally, chemically & physically stable Not poison the chemistry of the cell To be compatible with both reducing & oxidising atmospheres Be able to be formed into complex shapes and to be cost effective