Proposal abstract

In the future, a large part of the supply of heating or cooling in urban areas will be provided by low-temperature district heating systems. In addition to  renewable and waste sources, heat pumps, which are the most energy-efficient heat generators, will be used to increase the temperature required for hot water production. Similarly, heat pumps will serve as one of the main means of heating and cooling low or zero energy systems in rural areas.

The vast majority of heat pumps are based on vapor compression technologies. The biggest problem with these technologies are the refrigerants, which have a considerable influence on the global warming. Another problem regards low energy efficiency related to small devices. Although great efforts are being made to find new refrigerants, the number of realistic alternatives is unfortunately extremely small. Vapor compression cycle systems are also a source of noise pollution.

Numerous worldwide studies show that magnetocaloric cooling or heat pump technology is the best or most developed alternative to vapor compression technologies. Since this technology is still in development, research and activities are urgently needed to properly demonstrate the application of the technology. It is also necessary to solve the basic problems of heat transfer and magnetic field generators, which due to the inefficiency of current solutions prevent the applied research and related development of the technology.

Therefore, the main objective of the proposed research project is the development of a magnetocaloric booster heat pump as a support unit in the thermal substation of a low temperature district heating system. The advantage of magnetocaloric technology over the current technology of vapor compression systems is therefore the possibility of higher energy efficiency and the use of environmentally friendly refrigerants. The magnetocaloric technology is also an important advantage in urban environments, as it enables vibration-free operation. The research and development of the proposed project will initially focus on addressing two major obstacles to magnetocaloric technology. The applicant possess the ideas and the patent application, which offers the possibility of
significantly improving the power density and performance of existing active magnetic regenerators. With the help of knowledge and ideas we will overcome the problems of rotating permanent magnet assemblies from rare earths. For this purpose we will develop an energy-efficient, static and fast-oscillating magnetic field source without rare earths. An efficient hydraulic system will be designed and implemented. For the variable and multi-parametric operation of the electronic, electromechanical and hydraulic elements of the system, we will develop control electronics that will also act as the interface between the user and the heat pump of the substation.

The magnetocaloric heat pump will be integrated into the substation and tests will be carried out under various laboratory conditions. This will allow appropriate control adjustments and preparation for realistic operating conditions. Finally, we will integrate the magnetocaloric heat pump booster and the substation into the district heating system to demonstrate its operation.

Due to the broader range of applications of the developed technology, we will analyze the possibilities of using the technology and implementing it in other niches, such as household appliances (tumble dryers, dishwashers and washing machines) and for the heating and cooling needs of residential, low energy buildings.

Due to the importance of scientific research in the fields of advanced energy materials, cooling  and heat pumps and the development of future district heating systems, the results will be adequately disseminated through a wide range of media and high quality publications. We also intend to use the classical and several advanced approaches to communicate the results to the various stakeholders representing experts, the general public or policy makers.

Relevance to the development of science or a scientific field

The research and development of the magnetocaloric heat pump will assist in improvement, realization and testing of the latest concepts which represent potential solutions to the heat  transfer and viscous losses problems currently occurring in active magnetic regenerators. Further on, we want to test the thermal control elements in combination with a magnetocaloric material. In addition, we will upgrade our newest and breakthrough knowledge in the field of development and research of high oscillation and static magnetic assemblies to the level of their energy efficiency being comparable to the currently used
slowly rotating permanent assemblies which incorporate rare-earth materials. Since our research will tackle the areas that have not been investigated yet and enrich our latest results, we expect a significant influence and multiplicated effect on development of the primary are a magnetocaloric energy conversion ( heat pumps, and the areas of magnetocaloric cooling and energy generators). By the developed magnetocaloric heat pump and adequately developed control system we want to demonstrate the actual operation of a magnetocaloric heat pump as the support unit of a district heat system. This
will certainly enable transfer of knowledge and set a solid base for exploitation of the magnetocaloric energy conversion in new scientific and technological fields. On the other hand the project will enable comprehensive analyses on operation of the heat substation and the related heat pump. The obtained knowledge and experiences will be transferred to the scientic society. This especially regards the control of such units, as well as the knowledge on the optimization of operation or the adaptation of the substation unit with the heat pump to different operating conditions of future district heating systems.

Importance for the company Danfoss, district heating/cooling sector and heat pump sector

Danfoss Trata is the world's leading supplier of products for energy-efficient solutions for the district heating, cooling and air conditioning of buildings. The research and development of the magnetocaloric booster heat pump can therefore represent an important future global benefit for Danfoss by providing a competitive advantage with high added value for district heating or heat pump products. This can certainly influence the opening of new jobs and further strengthen Danfoss' position as a major global player in these two areas. The EU's investment in the district heating and cooling market is estimated at EUR 40 billion in 2020 (www.gminsights.com/industry-analysis/europe-district-cooling-market), while the global value of district heating and cooling in 2019 was over EUR 150 billion (www.gminsights.com/industry-analysis/district-heating-market). According to Technavio (www.technavio.com/report/global-heat-pump-market-analysis-share-2018), the worldwide annual growth of the heat pump market is estimated at about 8%, which corresponds to an annual growth of about 7 billion USD. Importance for the low (zero) energy buildings sector and future household appliances The heat output of a small booster heat pump is close to that of heat pumps for household appliances. Therefore, a further future use of the developed technology could serve as a future alternative replacement for the recently used vapour compression heat pumps in household dishwashers, tumble dryers and washing machines. In addition, the low or zero energy houses in rural areas will certainly use heat pumps as one of the most commonly used technologies for heating or cooling. According to Technavio (www.intellasia.net/dishwasher-market-trends-and-forecasts-by-technavio-599780), only the global dishwasher market will reach USD 21.8 billion in 2021. The same company reports that the global market for household appliances is growing by 7% (or USD 31 billion per year).

Importance for society
With dissemination of the project results, important information about efficient energy use and environmentally friendly solutions for existing refrigerants will be passed on to experts as well as to the general public. In addition, the importance of the energy efficiency of heat pumps as one of the future means of decarbonising buildings will be explained, demonstrated or highlighted in communications to various target groups. We will have the opportunity to train new generations of students and engineers in the field of magnetocaloric energy conversion. This will be done by introducing the topic into the regular educational process and by organizing summer schools. As the project results will have a multiplicative effect, the knowledge and experience gained from the project results will be successfully transferred to other areas of caloric energy conversion (magnetocaloric, elastocaloric, barocaloric, multi-caloric).

Objective of the proposed research project – beyond the state of the art

The main objective of the proposed research project is to develop a magnetocaloric heat pump booster, which can serve the low temperature district heating system. This will be achieved by the implementation of the following sub-objectives and related research activities (Figure 3): To overcome two main barriers of magnetocaloric technology The applicant possesses a patent application pending idea [45], which offers the possibility to significant improve of the power density and efficiency of the existing active magnetic regenerators. Moreover the knowledge and own new ideas will be applied (extension of the own work, presented in the patent application [46] and the recent article by Klinar et al [42]), which can lead to an energy efficient, static, and fast operation of the magnetic field source without use of rare-earth materials. Presently known rotary permanent magnetic assemblies cannot operate with such performance.
To provide optimized solutions to hydraulic and electronic control of the magnetocaloric heat pump An efficient hydraulic system will be designed and implemented to achieve a fast distribution of the heat transfer fluid to/from the active magnetic regenerator and to/from the heat source/heat sink
heat exchangers, while avoiding parasitic viscous losses and dead volumes of the whole system. Heat exchangers with the high effectiveness will be designed. For variable and multi-parametric operation of electronic, electro-mechanical and the hydraulic elements of the system, an electronic control
circuit (with all the sensory elements) will be designed and implemented. Such a control system will represent the interface between the user, the heat pump and the heating substation. To adapt, integrate, test and demonstrate the operation of the magnetocaloric heat pump as the booster in the district heating substation We will integrate the magnetocaloric heat pump into the heating substation. This will be done by adapting the market available heating substation with its internal elements for the application of the magnetocaloric heat pump and laboratory testing of the system at different operating conditions. The
characterization assessment of the performance will be followed by the demonstration at real operating conditions. The small size/power of the proposed heat pump enables further exploitation. Therefore the evaluation will be made for applications in other potential (realistic) market niches, such are household appliances (household clothes dryer, dishwasher, washing machine), and residential heating/cooling.

Detailed description of the work programme

The work program (see also Figure 3) consists of FIVE vertical work packages (WP). The TWO horizontal work packages (WP) regard the dissemination and the project management. The work package on the project management (WP7) is described in the chapter 27.5.

Work Package 1 (WP1): Magnetocalorics and heat transfer

This WP concerns the design, numerical modelling and optimization, construction of the selected principle, and experimental testing of new design concepts for active magnetocaloric regeneration principle with high power density. It consists of five tasks denoted as T1.1 to T1.5 as follows:

T1.1: Several different designs for new AMR principles for high power density will be conceptualized. The task is finished.
T1.2: The most promising design concepts will be numerically modelled. Parametric performance analysis will help evaluating the most efficient design concept from heat transfer perspective. The task is finished.
T1.3: The chosen concept will be numerically optimized with regard to its geometry, magnetocaloric properties and operating conditions. The task is finished.
T1.4: The optimized and designed active magnetic regenerator will be constructed. The task is in progress - 70 % realized.
T1.5: Preliminary experimental on the performance of the designed and built advanced magnetic regeneration principle.

Deliverables:
D1.1. Report: conceptual design, modelling, numerical optimization of magnetocaloric regenerator
D1.2. Embodied heat regenerating structure of the magnetocaloric material

Work Package 2 (WP2): Magnetic field sources

This WP concerns the design, numerical modelling, and experimental testing of new design concepts for rare-earth free and energy efficient magnetic field source. It consist of five tasks denoted as T2.1 to T2.5 as follows:

T2.1: Several designs will be considered to target compactness and high energy efficiency. The task is finished.
T2.2: The most promising designs will be numerically modelled and analysed. The task is finished.
T2.3: The most energy and cost efficient design will be optimised geometrically in order to fit the constraints of the active magnetic regenerator designed in WP1. The task is finished.
T2.4: The optimized and designed magnetic field source will be constructed. The task is in progress - 70% realized.
T2.5: The magnetic field source will be experimentally tested

Deliverables:
D2.1. Report on design, development and testing of magnetic field source
D2.2. Magnetic booster heat pump magnetic field source developed

Work Package 3 (WP3): Heat Exchangers & Hydraulics

This WP concerns the design, dimensioning, numerical/experimental optimization of the hydraulic circuit and heat source/heat sink heat exchangers. It consist of five tasks denoted as T3.1 to T3.5 as follows:

T3.1 Different hydraulic system designs of the magnetic heat pump will be considered. Several commercially available heat exchanger designs will be evaluated. The task is in progress - 50 % realized.
T3.2 Heat exchangers will be dimensioned with regard to the demands on the side of the heat sink and heat source, as well as with regard to the minimized pressure losses. The whole hydraulic system will be dimensioned to minimize all the pressure losses inside the peripheral elements such as check valves,
bleed valves, tube connections, pressure gauges, etc. The task is in progress - 80 % realized.
T3.3 All the elements of the hydraulic system will be tested separately in order to determine the correct pressure losses. If needed, optimization of particular elements will take place within this task. The task is in progress - 50 % realized.
T3.4 Heat exchangers, all the peripheral elements and the active magnetic regenerator will be assembled together with the pumping system in one complete hydraulic circuit.
T3.5 Experiments of the whole hydraulic circuit dynamic behaviour will be performed.

Deliverables:
D3.1. Report on optimal selection and tests of heat exchangers and their integration into the whole hydraulic system
D3.2. Designed, constructed and optimized overall hydraulic system with all the components

Work Package 4 (WP4): Control

This WP concerns the design and integration of the electronic and control circuit, which will be performed through the following tasks (T4.1 to T4.4):

T4.1 Based on defined control algorithms the appropriate circuit will be designed: Special consideration of magnetic field intensity and change, fluid flow rate, fluid direction and operating frequency for the mutual operation of the whole device. The task is in progress - 50 % realized.
T4.2 Following the circuit design a prototype electronic circuit will be built. Special emphasis will be devoted to time response of reactive elements of the circuit.
T4.3 Experimental tests on how efficient does the control systems control the dynamic operation of the magnetic field source and the pumping system. Furthermore, tests of the heat pump dynamics with the change of the temperatures on supply/demand sides.
T4.4 adjustment and optimization of all the control signals for the correct operation of the magnetic booster heat pump.

Deliverables:
D4.1. Report on design and integration of the electronic and control circuit
D4.2. Designed, constructed and calibrated control electronics of magnetic booster heat pump

Work Package 5 (WP5): Integration and demonstration

This WP concerns the integration of the magnetocaloric heat pump system into the heating substation, which can be used in the low DH system. The work will be performed through the tasks T5.1 to T5.5:

T5.1 Successful integration of MAGboost within the laboratory-scale heating substation.
T5.2 Tuning the control system of the MAGboost to operate at real conditions, prescribed by the temperature and heating demand of the DHW.
T5.3 Extensive set of tests and iterative modifications based on parametric experimental analysis.
T5.4 Implementation of MAGboost into already operating DH. Extensive stress testing prior fully automated operation of the device.
T5.5 Field testing of successfully implemented MAGboost inside the operating DH system.

Deliverables:
D5.1. Report on the integration and demonstration of MAGboost within laboratory and field testing.
D5.2. Fully operational MagBoost prototype in different real-world scenarios.

Work Package 6 (WP6): Dissemination and communication

These tasks are in progress all the time.