Heat Pump Technology

Refrigerants circulate as a working medium in the refrigeration circuit and transport heat from the cold to the warm side of the process. The refrigerant choice is crucial for the cycle efficiency in heat pumps and refrigeration applications. In addition, different refrigerants have varying degrees of global warming potential, toxicity and flammability, which also places special demands on their technical implementation in refrigeration circuits.

The F-Gas regulation of the European Union specifies that the use of climate harmful refrigerants be drastically reduced. Therefore, system and equipment manufacturers must either develop new systems or convert existing systems to adapt to the new requirements. Natural refrigerants such as propane (R-290), propene (R-1270) and ammonia (R-717) offer good possibilities which are technically feasible. However, these refrigerants also require new approaches for plant safety.

Fraunhofer ISE is focusing on sustainable, efficient and long-term solutions using natural refrigerants such as propane or water. Propane, which is climate-friendly but also highly flammable, is becoming increasingly attractive as a working fluid in heat pumps for heating applications. At Fraunhofer ISE we develop solutions which enable its safe and efficient use.

Current R&D Approaches:

• reducing refrigerant charge with more compact designs of heat exchangers and compressors
• performing coordinated, evaluated safety tests, e.g. leakage tests on appliances and refrigeration circuits
• develop safety concepts for heat pumps with flammable refrigerants
• using water as refrigerant for thermal refrigeration: Waste heat utilization for cooling by thermal cooling processes (adsorption/absorption) 

Most heat pumps in buildings use air as a heat source. The ambient air is drawn in, passed through a heat exchanger and cooled. The heat is absorbed in the heat pump's cooling circuit. The air flow and the heat pump compressor can cause noise, which is radiated by the air, the housing and the surroundings, depending on the type and place of the equipment and installation. These noise emissions can be perceived as disturbing by the surrounding environment. With the rising number of outdoor heat pumps in the vicinity of buildings, the device acoustics are becoming more important – especially in dense urban areas.

Fraunhofer ISE is focusing on the characterization and evaluation of structure-borne noise and is deriving suitable measures for noise reduction. To perform acoustic measurements and vibration analyses, we have a broad range of experimental equipment and analytical expertise. Besides the implementation of noise reduction measures, our current research activities concentrate on simplifying the test procedures. We also want to make it possible to quickly and easily use standard market equipment for the analyses.

Current R&D Approaches:

• develop simplified methods to identify noise sources
• perform acoustic and structural dynamic evaluations of components (compressors) and devices
• analyze fatigue of connections and refrigeration circuits

The market for modern heating and air-conditioning technology is growing and changing rapidly. Manufacturers must act quickly to ensure their competitiveness, as products are becoming increasingly efficient and intelligent. At the same time, the complexity is increasing due to hybridization, innovative control concepts and smart system integration. With these developments, the measurement of devices and systems under controlled conditions is becoming increasingly important for product development and evaluation.

In the TestLab Heat Pumps and Chillers, Fraunhofer ISE performs accredited measurements for energy labeling, HP Keymark or passive house labeling for almost all of the usual product groups. We support our industrial partners in the development process by offering innovative testing and evaluation methods to gain reliable information on product performance under different operating conditions. Therefore, our partners can considerably reduce the time between the concept and the product launch. In addition, we develop new and innovative testing methods that will form the basis of product qualification in the future. We incorporate our extensive experience gained in numerous R&D projects on heat pumps and refrigeration equipment into our procedures.

Services:

• expanded service offer for accredited tests and evaluations: new product groups and test methods
• development of new testing methods for innovative technologies and hybrid energy systems
• development of new and expanded test methods for energy labeling
• Hardware-in-the-Loop tests
• solutions for secure data transfer for real-time measurement and simulation between the laboratory and customer
• participation in national and international committees to develop innovative approaches to quality assessment
• cross-technology product characterization in R&D and quality assurance

Heat pump units have become much more efficient due to the technological advances of the past years. The next optimization step focuses on improving the ecological and economic efficiency of the overall system rather than on the individual device and puts installation and operation in the spotlight. Heat pump systems are not always installed and adjusted optimally. They may not be sufficiently customized to meet the conditions specific to the respective building. This results in unnecessary efficiency losses and prohibits them from realizing their full potential, which hinders them from fulfilling their important role in the future energy system.

Fraunhofer ISE develops methods for digital quality assurance during installation using artificial intelligence to optimize operation. This not only allows heat pumps to be installed faster and with less errors, but also enables self-optimization processes and monitoring during operation. 

Current R&D Approaches:

• use of digital methods to optimize heat pump design, planning, installation and operation
• standardization of planning process, e.g. by categorizing different heat pump systems
• simplification and acceleration of the installation phase
• self-learning heat pump systems for optimization during operation

Sector coupling is a core element of the energy system transformation, in particular the direct and indirect use of renewable electricity in all consumption sectors. This means that combustion heating systems will eventually be replaced by electrically based systems. Heat pumps will play a key role in this process. To carry this out successfully, it is essential to intelligently integrate heat pumps into the energy system. When used optimally, more flexibility is possible in electricity use, which contributes to grid stability. For this to be happen, however, intelligent control and operational management systems are required. New business models for utilities, grid operators and plant owners will emerge. At Fraunhofer ISE, we develop and test tools and concepts for the optimal integration of heat pumps into the future electricity system.

Current R&D Approaches:

• analysis of heat pump/PV combined systems with consideration to self-consumption of PV and interaction with the power grid
• investigation of the flexibility potential of heat pumps in the power grid
• monitoring and control and design optimization of heat pump systems ("SG Ready 2.0")
• development of standardized communication solutions
• operational management systems based on model-predictive or agent-based control strategies
• optimal integration of heat and electricity storage