SubSie Platform – Sorption Steamers for Vessel Temperatures Less 0°C

Platform for Scientific Quality Assurance and Market-Oriented Networking

Duration: 06/2019 - 05/2023
Contracting Authority/ Sponsors:
Bundesministerium für Wirtschaft und Energie (BMWI); Projektträger Jülich, Energieeffizienz für Industrie und Gewerbe (ESN2)
Project Partners: Technische Universität Berlin, Fachgebiet Maschinen- und Energieanlagentechnik
Project Focus:
Logo TU Berlin
© TU Berlin
Boiling water in low pressure region (10-20 mbar) induced by a porous boiling structure
© Fraunhofer ISE / Photo: Rahel Volmer
Boiling water in low pressure region (10-20 mbar) induced by a porous boiling structure. Study of evaporation behaviour of water around the freezing point is focus of the project network SubSie.

SubSie is a thematic research group within the Research Network Industry and Trade in the field of waste heat utilization. The aim of the SubSie group is to increase the application range of both refrigeration and heat pump systems that use water as refrigerant and are powered by heat - especially waste heat - for industry and businesses.  The goal is to realize the energy saving potential in the provision of cold and heat by utilizing waste heat.


Today most thermally driven sorption chillers and heat pumps use water as a refrigerant. The freezing point of water, however, puts restrictions on their field of applications. Up to now, water evaporators risk damage due to freezing. Because of this, these systems cannot be used for refrigeration applications with temperature requirements around and below 0°C and in heat pump applications for low-temperature heat sources in this range (especially outdoor air in winter). The declared objective of the Federal Government’s 7th Energy Research Programme under the "Efficiency First" principle is the increased utilization of necessary waste heat.  In Germany, there is a large amount of unused waste heat in the temperature range <120°C and at the same time a high demand for cooling, especially in the temperature range around 0°C, e.g. in industrial refrigeration and food cooling. Moreover, there is a growing demand in the refrigeration industry for technologies with climate-friendly refrigerants, which is driven by the F-Gas Regulation.

The main R&D question to be addressed is the use of water as refrigerant within the freezing point range of 0°C. The individual projects within the research network investigate and develop innovative technical solutions for water evaporation. These shall facilitate an energetically and economically efficient supply of thermally driven refrigeration systems in an extended temperature range as well as the use of air as a heat source in thermally driven heat pumps.

The overall scientific coordination, consolidation and preparation of the content of the subprojects within the SubSie platform are carried out  cooperatively between Fraunhofer ISE and TU Berlin. This platform ensures the cross-comparison of results, allows for the exchange of generally valid results and provides room for discussions on expanding the applicability of energy-efficient refrigeration systems and heat pumps at market-oriented networking events.