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Die fluktuierende Verfügbarkeit regenerativer Energiequellen stellt eine Herausforderung bei der Planung und Auslegung regenerativer Gebäudeenergiesysteme dar. Die in einem System benötigten Speicherkapazitäten hängen dabei sowohl von der eingesetzten Regelungsstrategie als auch von den temperaturabhängigen Wirkungsgraden der Anlagenkomponenten ab. Genauere Einblicke in das Betriebsverhalten eines Gesamtsystems können dynamische Simulationen liefern, die eine Analyse der Systemtemperaturen und von Teilenergiekennwerten ermöglichen.

Gas driven sorption heat pumps can be an efficient alternative to conventional gas condensing boilers for heating buildings. Measurement results of a functional prototype of a gas adsorption heat pump with 40 kW nominal capacity and the SAPO-34-water working pair are presented. The innovative adsorption heat exchanger is directly crystallized applying the partial support transformation technique. A transient lumped-parameter model of the gas adsorption heat pump is developed. For the first time, it is possible to perform an annual simulation of the GAHP within the heating system of a multi-family house with full adsorption dynamics based on calibrated and validated component models. This annual performance calculation is carried out for the two different low-temperature heat sources geothermal heat (bore hole heat exchanger) and exhaust air. Using exhaust air as low-temperature heat source for a GAHP is an entirely new approach that is evaluated in this study. Compared to a gas condensing boiler, the annual gas consumption is reduced by 22 % for the case of bore hole heat exchanger and by 27 % for the case of exhaust air as low-temperature heat source for a building with heating circuit design temperatures of 45 °C/35 °C.

A main focus of recent R&D on adsorption modules for thermally driven heat pumps and chillers has been to enhance the volume specific power output while maintaining a reasonable coefficient of performance (COP). An adsorption module using a new type of heat exchanger based on aluminum sintered metal fiber structures brazed on flat fluid channels has been developed. The heat exchangers for adsorber/desorber and evaporator/condenser are identically constructed. The adsorption heat exchanger is coated with a silico-alumino phosphate (SAPO-34) by a partial support transformation direct crystallization (PST) [1]. Both components are placed in a vacuum tight housing using a valve-free configuration. Water is used as adsorptive. The experimental characterization of the module shows a high volume specific power (up to 82 W/litre module for cooling, 320 W/litre for heating). Although no heat is recovered between ad- and desorption cycle, a COP of almost 0.4 is reached for cooling and 1.4 for heating. Driving temperature differences are defined for the analysis of the heat exchanger performance. The evaporator/condenser shows extremely good performance with about 240 W/K specific evaporation power per litre of heat exchanger, while the adsorber is limiting the module performance.

This document is the Deliverable "D3.3 - Experimental characterization of the hybrid heat pump module " of the European project "HYCOOL - Industrial Cooling through Hybrid system based on Solar Heat." (hereinafter also referred to as "HYCOOL", project reference: 792073). This deliverable reports about the experimental performance evaluation of the hybrid cascading chiller under lab-controlled working conditions. The chiller was manufactured by Fahrenheit by connecting in cascade a silica-gel water adsorption cooling machine with a vapour compression chiller using R1270 (propylene) as refrigerant.

In this paper, the activity carried out within the H2020 project ZEOSOL is introduced. Making use of the lessons learned from previous solar cooling projects, an advanced hybrid solar cooling system was developed. It consists of a thermal and an electric unit in parallel integrated in a single unit with the drycooler. ZEOSOL is based on commercial components but was optimised in order to guarantee optimal seasonal performance, high reliability (and therefore reduced maintenance) and easy installation. The components of the system were experimentally tested in the laboratories of AkoTec, CNR ITAE and Fahrenheit, with a specific attention to the definition of performance maps as a function of operating and design parameters. During the tests of each component, possible control strategies and rules were identified. Subsequently, a simplified sizing tool was developed, which can be adapted to different configurations and climates and takes into account user-experience for different stakeholders, such as engineers and installers. The methodology implemented is described, in order to be used as a guideline for the definition of standard sizing procedures for solar cooling systems. As exemplary cases, the results for three different climates (Athens, Berlin and Ryiad) are also presented.

This document is the deliverable "D3.4 - Design review of the hybrid heat pump" in the European project "HYCOOL - Industrial Cooling through Hybrid system based on Solar Heat" (hereinafter also referred to as "HYCOOL", project reference: 792073). HyCool Project Mission is increasing the current use of Solar Heat in Industry Processes, and to do so the project proposes the coupling of a new Fresnel CSP Solar thermal collectors (FCSP) system with specially build Hybrid Heat Pumps (HHP) (a "two in one" combination of adsorption and compressor based heat pumps) for a wider output temperature range (Solar Heating & Cooling -SHC-), and a wide range of design and operational configurations to increase the potential implementation of the proposed Solar Heat in industrial environments. The solutions encompassed in the project will be implemented and tested in operational processes in two different pilot cases in the food and chenmical industry. The purpose of this deliverable is to describe the key findings of the review process, which focuses on the design of the Hybrid Heat Pump. This report contains the findings with regard to control strategy, interconnection of the heat pumps, selection of the suitable adsorbent and refrigerant, as well as an optimal size of the HHP.

In the following report the design of the dry cooler unit for the ZEOSOL system will be shown. It was carried out on the basis of experimental data of the sorption chiller produced by the partner FAHREN. The design process took into account the dynamics of sorption chiller in order to determine the most difficult operating conditions. A simple basic commercial software was employed for the design process and the calculation of main HEX parameters and selection from a supplier catalogue. The designed unit is a dry heat rejection device with high efficiency at very high temperatures. It was designed for Southern Europe climate (39.6 °C is the design ambient air temperature). Detailed drawings are also enclosed. A description of the back-up heat pump and it`s design is given at the end of the report.

This document is the deliverable "D3.2 - First design of the modular hybrid heat pump" in the European project "HYCOOL - Industrial Cooling through Hybrid system based on Solar Heat" (hereinafter also referred to as "HYCOOL", project reference: 792073). This document contains the first system image of a cascade chiller as part of the research project - "HYCOOL". The system presented forms one of the core elements of this project. A novel, two-stage cascade connection is the focus of the investigations. Driven by hot water, an adsorption unit represents the warm stage of the cascade. The adsorption process provides cold water at a low thermal level. The colder stage of the modular hybrid heat pump is based on a compression refrigeration unit. Both working principles are combined. The cold water from the adsorption plant will be used to dissipate heat in the condenser of the lower stage. In this way, the temperature lift between evaporator and condenser of the compression circuit is reduced and consequently energy efficiency is increased while compressor power consumption is reduced. First, the cascade system is analysed to get a first general impression of systems elements to be examined. The current state of research is included. Subsequently formulated boundary conditions and assumptions are consistent with the intended application area and location of the modular hybrid heat pump. Furthermore, the use of the conventional solution for cooling requirements is taken into account using a mathematical analysis as a basis for comparison. The internal calculation tool of FAH is used to identify the operating characteristics of the adsorption unit. An online calculation tool from GEA Bock confirms the energetic balance of the compression refrigeration part. Using the data publicly available from weather stations, the weather conditions at the planned installation site are sufficiently well represented. All results are processed and evaluated with Microsoft Excel. A laboratory scaled hybrid heat pump is designed based on the operating characteristics of the reference system. The calculation results of the cascade system with a cooling capacity of 19 kW show significant performance savings in operation. This configuration has a positive effect on the cooling capacity. Increases in cooling capacity over the entire operating range are included. An electrical power saving of 14 % is combined with an increase in cooling capacity of 9 %. Moreover, an increase in nominal EERof 26% is achieved in the investigated area compared to conventional system solutions. As a result, the main components of the experimental modular hybrid heat pump are identified and a first system image in form of the Piping & Instrument diagram is developed. Furthermore, it is pointed out that the declared assumptions for the calculation of the hybrid heat pump only provide a good approximate result. However, a more efficient operation is expected as part-load conditions have not yet been taken into account due to a lack in perfomance data. Therefore, the operation of the entire system has to be tested. The electrical power savings of the compressor are continuously compromised using a larger re-cooling unit and a larger number of circulation pumps. On the other hand, intelligent partial load operation holds further energy saving potential. Following, the first layout of the modular hybrid heat pump is designed, and all other system components are identified. Within the task T3.3 the realized hybrid heat pump will be installed and tested at CNR lab. The results will be crucial to do the final layout of the hybrid system.

The aim of this document is to assess the performance of the ZeoSol system with focus on different locations. From these investigations it can be shown whether the simplified design tool developed within ZEOSOL leads to a system layout that shows the performance expected. From the comparison of the performance in different climatic conditions necessary modfications of the system design can be deduced.

This document is the deliverable "D3.1 - Optimization of the hybrid heat pump configuration and control strategy through dynamic modelling under different scenarios" of the European project "HYCOOL - Industrial Cooling through Hybrid system based on Solar Heat." (hereinafter also referred to as "HYCOOL", project reference: 792073). The present deliverable aims at defining a dynamic simulation tool for the modelling of the hybrid cascade chiller, which represents one of the core systems of the HYCOOL project. This system is based on the coupling of a thermally driven adsorption chiller and a vapour compression chiller. In particular, the operation of the adsorption chiller is primarily meant to dissipate the heat of condensation that needs to be rejected by the vapour compression chiller. In this way, reducing the temperature lift between evaporator and condenser, less compression work is needed and the energy efficiency ratio is improved. Firstly, a components selection was performed, in order to identify the most suitable refrigerant as well as the sizing of the heat exchangers, compressor and valves of the two machines. Particularly the refrigerant for the vapour compression chiller was selected by means of a thermodynamic optimization, coupled to considerations regarding the compressor sizing and its environmental impact. An innovative natural refrigerant, R290 (i.e. propane) was identified as the most promising for this application, also according to the current technology being developed by FAHRENHEIT. The dynamic model was implemented in the language Modelica through the software Dymola. It allowed exploiting standard libraries for the modelling of relevant components as well as physical phenomena, such as heat and mass transfer, which can be easily adapted to properly model the defined technology under investigation. For this reason, for all the components of the hybrid chiller, technical data from manufacturer datasheets and existing experimental data were used to make the model reliable. The implemented model was successfully validated against experimental data collected on a lab-scale prototype previously produced by FAHRENHEIT and tested at the CNR ITAE lab. The operation of a 20 kW cooling power machine, which will represent the rated power for the lab-scale experimental activity during the T3.3, was then simulated under different conditions. They represent the operation under variable heat source and sink and implement an experimental dynamic load profile provided by GIVAUDAN, whose meaningfulness can be extended also for the application to the Bo de Debò pilot plantThese simulations were used to optimize the ratio between cooling powers of the adsorption chiller and vapour compression chiller, demonstrating that the adsorption chiller needs to provide at least 20% more cooling power than the vapour compression one, to properly operate the hybrid configuration. Furthermore, some Key Performance Indicators were defined, namely, the cooling capacity and the thermal COP of the adsorption chiller and the average inlet temperature at the condenser of the vapour compression chiller. These were employed to comparatively evaluate the operation of the cascade chiller under different boundary conditions, thus highlighting which might be the most effective control strategy to maximize the overall efficiency. The outcome of this analysis was the identification of performance maps, as function of boundary conditions and part load, useful to identify the best management strategy of the cascade chiller and to give a comprehensive indication on its operation in different conditions The implemented simulation tool will be further refined as soon as all the components will be designed during the T3.2 and then used, during the T3.3 to identify further management strategies to be tested on the lab-scale prototype. The performance map obtained, which summarises the energy flows in and out from the hybrid heat pump will be employed during WP5 and WP6 as input for the control development and system integration design. Finally, it will represent a useful tool throughout the project also to support the sizing of the hybrid chiller for the demo site installations.

Adsorption cycles can be used for thermally driven heat transformation applications such as heat pumps or chillers. A major challenge in building such devices is the design of the adsorbent heat exchanger (Ad-HX). Two main design criteria are discussed here: the coefficient of performance (COP), relating the useful heat or cold with the energetic expenses, and the (volume or mass) specific cooling or heating power (SCP/SHP). Addressing the aim of designing an adsorbent heat exchanger, the article proposes a two-step procedure. The first step is the analysis of the COP, which is determined by the thermophysical properties of the adsorbent material and the working fluid, the temperature levels of the process, and the mass ratio between active adsorbent and heat exchanger material. Promising configurations reach a required COP and can be specified more detailed in a second step by estimating the power density. A simplified design approach taking the chain of heat and mass transfer resistances into account is presented, and examples of recently developed innovative adsorbent heat exchangers are shown.

Thermal storage is essential to increase energy efficiency of thermal systems. Phase change materials (PCM) can store high energy densities in small temperature differences by changing their phase from solid to liquid. To ensure not only high storage densities, but also suitable output power, a heat exchanger (e.g. a fin-and-tubes heat exchanger) has to be designed. To optimise PCM storages with such devices, a simulation model is helpful. To this aim, a model for a fin-and-tubes heat exchanger filled with PCM was developed in COMSOL Multiphysics. As the main focus of the model is on the behaviour of the PCM in combination with the fins, this part was modelled in 3D. The specific heat capacity of the PCM was included as input file, based on measurements of the material carried out in differential scanning calorimeter (DSC). This provides exact representation of the PCM behaviour, which could be shown by simulating DSC-experiments. The pipe flow in the heat exchanger was simplified to 1D to shorten simulation time. Both components are coupled to each other. The model was validated with measurement data from two fin-and-tubes heat exchangers with PCM. The heat exchangers differ in dimensions and in the PCM used: one uses a sugar alcohol (D mannitol, Tm=166 °C) and the other one uses a paraffinic commercial PCM (Plus ICE A82, Tm=82 °C). Results of both validations show good accuracy. Additionally natural convection in the liquid phase of the PCM was modelled. For small fin distances it has a negligible influence, but it becomes important for larger ones depending on the PCM. This was shown by further simulations. Afterwards the model was used to optimize both fin-and-tubes heat exchangers with PCM. The model, validation and optimisation results will be presented in this paper.

This paper presents a heat and mass transfer simulation of an adsorber, taking into consideration the geometry of the heat exchanger and the diffusion in the adsorbent medium. In this model, an increment in the direction of heating/cooling fluid containing one (or more) fin pitch was considered. In the domain of this increment, the distribution of the adsorbent temperature was evaluated in the radial and axial directions. The model is validated by experimental data of different adsorbents, volume flows and temperatures. All data were collected in an adsorber test-bench at Fraunhofer ISE. As a result it was found a coefficient of multiple determination of around 0.94 and an error of 20% during the transient. Finally, the model was run on typical operation for cooling application and compared with data from literature. A numerical energy balance was also evaluated. In summary, the results obtained by a independent group shows the same range of confidence of the model developed here, in terms of the tendency of the curves and even the absolute values.

An integrated system combining highly efficient III–V solar cells in an optical concentrator system with a polymer electrolyte membrane electrolyser is presented. Hydrogen and oxygen are produced by solar water splitting. The integrated design and the high concentration factor of 500 allow material savings and high system efficiencies. The thermoneutral solar to hydrogen conversion efficiency of a prototype system with an area of 96 cm 2 was measured outdoor to be 18%.

Membrane electrode assemblies for regenerative polymer electrolyte fuel cells were made by hot pressing and sputtering. The different MEAs are examined in fuel cell and water electrolysis mode at different pressure and temperature conditions. Polarisation curves and ac impedance spectra are used to investigate the influence of the changes in coating technique. The hydrogen gas permeation through the membrane is determined by analysing the produced oxygen in electrolysis mode. The analysis shows, that better performances in both process directions can be achieved with an additional layer of sputtered platinum on the oxygen electrode. Thus, the electrochemical round-trip efficiency can be improved by more than 4%. Treating the oxygen electrode with PTFE solution shows better performance in fuel cell and less performance in electrolysis mode. The increase of the round-trip efficiency is negligible. A layer sputtered directly on the membrane shows good impermeability, and hence results in high voltages at low current densities. The mass transportation is apparently constricted. The gas diffusion layer on the oxygen electrode, in this case a titanium foam, leads to flooding of the cell in fuel cell mode. Stable operation is achieved after pretreatment of the GDL with a PTFE solution.

A fuel cell has been designed that combines three methods of spatially resolved measurements. The experimental setup allows to perform a simultaneous evaluation of current, temperature and water distribution in a polymer electrolyte fuel cell (PEFC) under operation. The test cell has a segmented anode flow field for current distribution measurement. The back plate of the cathode flow field is made of an optical window, which is transparent for infrared (IR) as well as for visible wavelengths. This allows infrared thermography and optical surveillance of water droplets and flow field flooding.

Multi-junction solar cells from III-V compound semiconductors can generate ideal voltages for the electrolysis of water. This paper presents results of a PV-concentrator HyCon® with Ga0.35In0.65P/Ga0.83In0.17As tandem solar cells which are directly connected to the electrodes of a local polymer electrolyte membrane electrolyser. This electrolyser is integrated into the base plate of a concentrator module. A prototype system with an area of 96 cm2 has been realized. The solar to hydrogen conversion efficiency of this system was measured outdoor in Freiburg to be 18.2 % (based on the thermoneutral voltage of 1.485 V).