As the concept of solid oxide cell elecrolysis is the main issue this paper concerns, its operation principles, theory, construction, employment in power sector are in detail considered in separate chapters. Here, however the technology is presented briefly in comparison with the above discussed electrolysis techniques (alkaline, PEM). In a SOE cell electrolyte is solid ceramic oxide – yttria stabilized zirconia (YSZ). Cathode is composed of YSZ with nickel content. Operation temperature range is 700-1000