Ingenieurbüro Dr Gerald Müller (IGM) is a Engineering consultancy for research, development and project development in low head hydropower. They developed hydropower converters based on novel concepts, such as the utilisation of hydrostatic pressure differences or the generation of head differences from currents. Further areas of expertise include the historic technology for renewable energy, the principles and the performance of historic machines in order to establish whether they have further development potential today, where improved theory, better materials and changed requirements exist.