HTWP – Bosch

Development of a gas driven and electric heat pump for multi-family houses Bosch/ISE

Funding code: 03ET1377 A/B/C

Funding period: 01/2018 until 12/2020

Project partner: Fraunhofer ISE, Bosch Thermotechnik, Robert Bosch GmbH


Bivalent (hybrid) heat pump heating systems in the field of the energetic renovation of multi-family houses


Development and implementation of dimensioning and operating strategies for bivalent systems in the field of the energetic renovation of multi-family houses, under consideration of

  • different hydraulic integration for room heating and drinking water heating
  • different optimisation objectives (primary energy, CO2, investment cost,…)
  • grid support
  • building and heat transfer system


The main challenges posed by the installation of heat pumps in existing multi-family houses are the required high flow temperatures – specially to comply with health regulations with regard to domestic hot water –  and the limited availability of adapted heat sources in the surroundings.

A promising solution for the renovation consists in installing so-called bivalent (hybrid) systems in which an electric heat pump and a fossil power heat generator operate in parallel through a superior control system.

With this solution the heat pump (incl. source) must not be dimensioned for maximum performance and the heat generators can run more efficiently (for example with regard to the operating costs or primary energy consumption).


Bivalent temperatures and shares of the heat generators gas boiler and heat pump in covering the heat load under variation of use (renovated or non-renovated existing buildings) as well as the optimisation objectives (primary energy consumption, CO2 emissions and consumption costs); results of simplified, static calculations.

Work plan

Basics, evaluation of state-of-the-art-technology

  • Survey of available technologies, analysis of influencing factors on the operating strategy of bivalent systems
  • Research and evaluation of essential legal and normative requirements

Preliminary study of relevant fields of application in multi-family houses

  • Definition of reference buildings
  • Investigations on the flexibility of load ranges depending on building standard and heat transfer system

Simulation-based evaluation of various dimensioning and operative strategies for different system concepts

  • Definition of the relevant use cases and implementation of relevant system diagrams in the analysis tool
  • Conduct of scenario calculations with different optimisation objectives
  • Derivation von regulatory and operative strategies

Controller development and implementation

  • Simulation based control design
  • Implementation in system controller and tests

Demonstration projects

  • Selection of a demonstration building and creation of measurement concepts
  • Plant monitoring including optimisation and error monitoring

Contact persons


Björn Nienborg, project manager   
Thermal systems and buildings
Fraunhofer ISE
Heidenhofstraße 2, 79110 Freiburg
+49 761 4588-5883

Dr. Christian Glueck
Bosch Thermotechnik GmbH
Postfach 11 61, 35453 Lollar
+49 (0)6441 418-2340

Uwe Clement
Bosch Thermotechnik GmbH
Postfach 13 09, 73243 Wernau
+49 (0)7153 306-1947


Poster HTWP