The overall goal of the TOpTEn project, Topology Optimization of Thermal ENergy systems, is to further develop topology optimization (TO) as a design methodology for optimizing heat transfer performance in energy conversion systems. A secondary objective is to generate optimized structures for specific design conditions of each technology to be studied. The optimized structures will have enhanced heat transfer performance and e.g. reduced pumping power, which will allow regenerative devices and TEGs to operate at higher efficiency. The project is sponsoret by ” Det Frie Forskningsråds Sapere Aude-program – bevillings-ID: DFF – 4005-00320” (Danish Council for Independent Research).