Researchers of the Westphalian Energy Institute (WEI) at Gelsenkirchen Bocholt Recklinghausen University of Applied Sciences (WH) have developed a pocket-size PEM unit for water electrolysis. The electrolyzer stack is based on the WEI-invented method of hydraulic compression of individual cells [1] through the use of a patented control system [2]. The process allows for an alignment of hydraulic and gas pressure at the start-up of the system to achieve almost any pressure level