 According to (Dalenbäck, J-O., 1993), the first steps were taken in the early seventies in Linköping, Sweden, followed by a mature revision in 1983 in Lyckebo, Sweden.Inspired by this work, Finland developed its first plant in Kerava, and the Netherlands built a first plant in Groningen.These plants are reported under the International Energy Agency by (Dalenbäck, J-O., 1990).