Steam generating heat pumps – Overview, classification, economics, and basic modeling principles

Heat pumps (HP) are a key technology for decarbonizing heat supply in various sectors. In the past decades, extensive research has been carried out to achieve higher supply temperatures and heating capacities. In addition, modified heat pumps for the supply of steam – so-called steam generating heat pumps (SGHP) – have been developed. Since steam is the main heat carrier in the low- and medium-temperature range (up to 300 °C), SGHPs enable the use of HPs in various industrial processes and promote decarbonization of the industrial sector. This paper presents the current state of SGHP, relevant technical and economic data, and basic modeling principles to provide better access to this technology. Since SGHPs are based on conventional HPs (e. g. compression heat pump) or sometimes a combination of different HPs (e. g. compression heat pump with mechanical vapor recompression), relevant high and very high temperature heat pumps (HTHP and VHTHP) with supply temperatures above 100 °C are presented first. Closed-loop systems can currently achieve supply temperatures of up to 250 °C. With open-loop systems, even higher temperatures such as 350 °C are possible. Application examples of SGHPs with a TRL between 1 and 9 are discussed and used to develop five fundamental designs of SGHPs. Since many of these fundamental designs involve a combination of multiple technologies, a wide range of potential SGHP configurations are possible. This leads to high planning efforts, especially in the early stages of projects. In order to reduce this effort and enable a wider access to these technologies, basic modeling approaches and common parametrizations are presented for the main components. Case studies are used to discuss the fundamental impact of selected technical boundary conditions on the efficiency of the technologies. In addition to a technical update, economic data is presented to estimate the specific equipment cost of such heat pumps.