Metal-Organic Frameworks (MOFs), thanks to their type V water adsorption isotherms ("S-Shape") and large water capacities, are considered as potential breakthrough adsorbents for heat-pump applications. In particular, Al(OH)-fumarate could enable efficient regeneration at a lower temperature than silica-gel which would allow us to address the conversion of waste heat at low temperature such as found in data centers. Despite its greater adsorption capacity features, heat and mass transport limitations could jeopardize the potential performance of Al(OH)-fumarate. Heat and mass transport depend on the size of the bodies (mm range), their packing and on the pore structures, i.e. macro-mesopore volumes and sizes. This paper describes the cost-efficient and scalable synthesis and shaping processes of Al(OH)-fumarate beads of various sizes appropriate for use in water Adsorption Heat-Pumps (AHPs). The objective was to study transport limitations (i.e. mass and heat) in practical e beads which meet mechanical stability requirements. Dynamic data at the grain scale was obtained by the Large Temperature Jump method while dynamic data at the adsorber scale was obtained on a heat exchanger filled with more than 1 kg of Al(OH)-fumarate beads. Whereas the binder content had little impact on mass and heat transfer in this study, we found that Knudsen diffusion in mesopores of the grain may be the main limiting factor at the grain scale. At the adsorber scale, heat-transfer within the bed packing as well as to the heat exchanger is likely responsible for the slow adsorption and desorption kinetics which have been observed for very low desorption temperature. Finally, the dynamic aspects of the observed water adsorption isotherm shift with temperature are discussed in light of reported reversible structure modification upon temperature triggered water adsorption-desorption.

The cooling power of a closed adsorption system is depending on the thermo-physical properties of the sorbent/sorbate material combination. A good adaption by synthetic measures of the material properties to the temperature levels and mass flow rates of the external heating and cooling hydraulic loops has to be done consequently. Based on experimental results gained on a single vacuum chamber 1 kW average cooling power closed adsorption-desorption laboratory test rig, a scale-up to a four chamber 10 kW cooling power demonstrator was carried out. This scaling comprised the water sorbate evaporator and water vapour condenser design and the two combined fin-tube fixed sorbent bed adsorber/desorber heat and mass transfer units. The heat transfer fluid mass flow rates from the external heat sources and heat sinks was determined though simulation with an experimental results based model and is described for the mid temperature loop. In this paper, the design of the 10 kW prototype is described and technical decisions that were done as well as component choices are documented.

In urban multifamily houses, decentralized DHW systems using gas or electric boilers are still widely used. Their replacement with renewable energy sources is difficult and generally needs centralized DHW systems with a circulation system that ensures comfort and hygiene at the price of elevated heat losses. A consortium of three academic and one industry partner developed a decentralized DHW system, which uses the residual heat from the exhaust air of a controlled ventilation unit as energy source for a micro heat pump. The entire system, including ventilation unit, heat pump, and storage tank fits into the bathroom prewall and produces hot water for one apartment. This contribution gives an overview of the system and focusses on the development of the flat storage tank that fits into the prewall space of less than 30 cm width.

Stratified water storage tanks are used for storing solar heat for space heating and domestic hot water in one device. When this kind of storage is used in combination with a heat pump, the temperature stratification of the storage is a decisive factor for the overall efficiency and thus for the consumed end energy of the system. A test method is introduced and a key performance indicator for stratification efficiency is defined based on the second law of thermodynamics, i.e. on the entropy balance of the storage system. The laboratory test is based on a 24 hour cycle where realistic and dynamic charging and discharging is applied according to boundary conditions of real weather data of a day in the year. This particular day of the year was chosen because of its representativeness for the effect of stratification on the system performance, such that the annual performance can be derived directly from the performance shown in the 24 h test cycle. (C) 2018 The Authors. Published by Elsevier Ltd.

Geothermal energy as a heat source for heat pumps is increasingly unused in the city of Zurich. However, as indicated by other authors, the renewable potential for shallow geothermal heat use is limited due to the fact that natural regeneration in the absence of ground water flow is slow. Constant heat extractions from dense geothermal heat pump installations continuously cool down the affected ground layer.. In this case boreholes have to be dril led deeper or regenerated in order to avoid freezing around the borehole. The aim of this simulation study is to find the most economic geothermal heat pump concept, which does not lead to borehole freezing after 50 years of operation in areas with dense installations (an exemplary mean geothermal heat extraction of 35kWh/m2/a was supposed for this this study). Therefor a multi-family house with a standard ground source heat pump was simulated for a period of 50 years in Polysun. Various solar concepts, an air heat exchanger concept, a geo cooling concept and also a system without regeneration were added to the system. These concepts were compared under the assumption that all neighboring installations are using an equivalent regeneration strategy as the simulated system For the different system concepts, highly variable total borehole length were needed to avoid freezing, reaching from 1020m for a system with a large glazed collector field to 2160m for the un-rege nerated case. The heat cost of the analyzed system concepts was in the range of 21 - 27 Rp/kWh. The most cost-effective system concepts according to this analysis are the air heat exchanger or unglazed collectors. Increasing the total borehole meters was not only one of the most expensive options, but also the least sustainable, since the continuation of ground temperature decrease after 50 years was more pronounced with this option than for any other option.