"Gasthermenersatz" - Modular heat pump with environmentally friendly refrigerant to replace natural gas-based heating systems in large-scale residential buildings

The project "Gasthermenersatz" aims at developing, manufacturing, and testing a functional prototype of a decentralized, sound-optimized heat pump solution with refrigerant circuit modules connected in series or parallel. This renewable technology is well-suited to replace existing natural gas-based heating systems in large-scale residential buildings and to pave the way to carbon-neutral cities.

Short Description

Starting point / motivation

Natural gas-based heating systems are common in small single-family homes and large-scale residential buildings and provide heating - and if necessary domestic hot water - without storage system. In opposite to conventional central heating systems, each flat is equipped with its own natural gas-based heating system.

This natural gas-based heating system works on-demand, requires limited space, and allows to easily determine the energy consumption of each flat.

On the journey to a carbon-neutral city, it is necessary to use existing renewable energy sources in a resource-efficient, emission-free, and effective way and employ the building services as energy efficient as possible.

Contents and goals

The project "Gasthermenersatz" aims at developing a decentralized, sound-optimized, heat pump solution based upon multiple refrigerant circuit-modules. The heat pump runs under the constraint of minimal refrigerant charge. This renewable technology is especially well-suited to replace the currently installed natural gas-based heating systems, to increase the share of renewable energy sources, and to maximize thus the degree of decarbonization of existing housings in an urban environment.


To reach the targets of this project, five work packages have been defined, whose interconnections are listed below.

Work packages

  • WP 1: Project management & WP 5: Dissemination
  • WP 2: Concept development
  • WP 3: Laboratory setup
  • WP 4: Laboratory testing


  • Goal 1: Development of a technically feasible concept and its economic and ecological evaluation
  • Goal 2: Construction, commissioning and testing of the functional prototypes
  1. Concept development (WP2)
  2. Numerical simulation of the identified concepts (WP2)
  3. Economic and ecological evaluation (AP2)
  4. Construction of a first refrigeration circuit module (AP3)
  5. Testing of the first refrigeration circuit module (AP4)
  6. Construction of the complete system (AP3)
  7. Testing of the overall system (AP4)

With the help of expert knowledge, suitable components for the refrigerant circuit are chosen and translated into numerical models. By using the simulation environment Modelica/Dymola the refrigerant cycle is simulated on a module level first and subsequently the optimal combination of parallel and serial refrigerant charge modules is determined.

Based on established boundary conditions the technical specifications are created and detailed with design software provided by manufacturers and CAD-tools of the project partner Ochsner. In test runs, the control and safety criteria are checked and the sensors and data acquisition qualified. Under well-defined lab conditions, a refrigerant cycle module and later the full system are measured, whereas automatic data acquisition and analysis (incl. plausibility checks) with adequate software (LabView, Matlab, Python) are used.

Expected results

The project focuses on gathering knowledge on the modular design of a decentralized, sound-optimized, heat pump solution to ensure heating and if necessary domestic hot water. In addition, these insights are of relevance for real estate developers and property management for large-scale residential housing, respectively district planning.

"Gasthermenersatz" shall initiate further research projects as well as lead to profitable commissioned research for the implementation of heat pump solutions in the medium-term.

Project Partners

Project management

OCHSNER Wärmepumpen GmbH

Project or cooperation partners

AIT - Austrian Institute of Technology GmbH

Contact Address

Stephan Preisinger
Ochsner-Straße 1
A-3350 Stadt Haag
Tel.: +43 (5) 04245 - 548
E-Mail: stephan.preisinger@ochsner.com
Web: www.ochsner.com