Capmix is a new technology that - like RED - makes it possible to harvest energy from water streams with different salt content. The process is based on the absorption of ions in carbon electrodes. Capmix took shape as a collaborative project between four university institutions (from Italy, Spain, Poland and the Netherlands) and two companies (REDstack from the Netherlands and Mast Carbon International from England). This resulted in a European Union subsidised project running from 2010 to 2014. Capmix is seen as a promising new technology for generating energy. The aim of the project was to produce a working prototype and an analysis of the applicability of Capmix technology.

REDstack's contribution to this project was mainly in the design and early technology validation phases. REDstack has extensive experience with the design of RED stacks and was able to use this knowledge to optimise the performance of the Capmix stack. REDstack also had the facilities to test the process with natural water. This first took place at a site in Harlingen and in the final stage at the installation on the Afsluitdijk. These tests included the effect of pollutants from the surface water used (IJsselmeer and Waddenzee) and the required pre-purification.

REDstack also provided contributions on the possible introduction on a large scale. To this end, the ten most promising locations in Europe were identified and an analysis was made of economic, social and environmental aspects. To a large extent, these matters run parallel with the introduction of RED technology and the newly acquired knowledge was useful for both Capmix and RED. The future will tell if either technology will take the lead in the application of SGP; possibly both will seek their own niche.