A new journal publication presenting HYBUILD outcomes has just been released: Solar cooling systems are a promising solution for reducing the electrical consumption of conventional building cooling systems. Among various alternatives, photovoltaic driven vapour compression chillers are currently the most mature and economically feasible solar cooling technology. This study focuses on the semi-dynamic modelling of a vapour compression chiller coupled with a novel refrigerant-phase change material (PCM)-water heat exchanger (RPW-HEX) which replaces the conventional chiller’s evaporator, allowing the efficient storage of the produced cooling energy. A custom-build lumped parameter model was developed in TRNSYS and was used to assess the performance of the proposed system on annual basis. Using as benchmark a conventional PV driven vapour compression chiller with electrical storage, the retrofitted hybrid storage system showed improved performance, limiting the cooling demand peaks and enhancing the solar fraction, especially for partial cooling loads. Last, a comparison of the PCM thermal energy storage to conventional batteries was carried out, leading to enhanced performance characteristics for the latter.
A new journal paper presenting HYBUILD results has been released in the Energies journal.
The area-proportional baseline method generates phase fraction–temperature curves from heat capacity data of phase change materials. The curves describe the continuous conversion from solid to liquid over an extended temperature range. They are consistent with the apparent heat capacity and enthalpy modeling approach for the numerical solution of heat transfer problems. However, the curves are non-smooth, discrete signals. They are affected by noise in the heat capacity data and should not be used as input to continuous simulation models. This contribution proposes an alternative method based on spline approximation for the generation of consistent and smooth phase fraction–temperature, apparent heat capacity–temperature and enthalpy–temperature curves. Applications are presented for two commercial paraffins from Rubitherm GmbH considering heat capacity data from Differential Scanning Calorimetry and 3-layer-calorimetry. Apparent heat capacity models are validated for melting experiments using a compact heat exchanger. The best fitting models and the most efficient numerical solutions are obtained for heat capacity data from 3-layer-calorimetry using the proposed spline approximation method. Because of these promising results, the method is applied to melting data of all 44 Rubitherm paraffins. The computer code of the corresponding phase transition models is provided in the Supplementary Information.
The conservation and rehabilitation of buildings of vernacular architecture is a sustainable approach, not only because it leaves a small ecological footprint, compared to the erection of new buildings, but also due to the passive bioclimatic design features integrated in vernacular buildings. This paper will investigate the thermal performance of vernacular architecture in lowland area in diverse climatic contexts.
The findings of the current research are based on an on-site investigation carried out in a representative vernacular building that is going to be upgraded to a hands-on technology exhibition area of renewable energy systems complimented with visual means to enhance the experience of visitors under a Research European Programme (Horizon 2020). The current study provides a basis for the formulation of a site-specific design strategy to improve thermal conditions and achieve energy conservation within lowland constructions in diverse climatic conditions. Understanding and analysing the thermal behaviour of these spaces is the first step towards this strategy. The quantitative analysis reveals the various challenges faced and opportunities provided by lowland structures and contributes to informing current design policies. Moreover, the analysis will inform the sizing of the technical systems throughout the year.
Work is ongoing at the Langenwang Austrian pilot, to prepare the installation of the HYBUILD hybrid storage system.
The continental climate system will be installed at this pilot site. The maximum heating power consumption expected after the foreseen retrofitting operations is 10 kW. The following technologies will be applied in the building: PV, PCM thermal latent storage, Heat pump.
One of the main limitations for the wide diffusion of sorption systems, either as stand-alone and in hybrid configurations, is the low heat transfer inside the adsorber, as well as the low volumetric cooling power.
In this context, HYBUILD partners (CNR ITAE, AKG, Fahrenheit and Mikrometal) have just released a new scientific paper which reports the experimental activity on four different advanced configurations for the adsorber, based on microchannel heat exchangers where the gap between the channels is filled with porous structures where zeotypes of SAPO-34 family were synthetized.
The porous structures evaluated are high-density fins, two different aluminium foams and compressed chips from the waste of aluminium machining. The sorption dynamic and cooling power density of each structure were measured through a Gravimetric Large Temperature Jump testing apparatus.
The results obtained showed that the best-performing configuration is the one with high-density fins, that, for a 90/30/20 °C cycle showed a Specific Cooling Power up to 1.1 kW/kg. The other structures exhibit a much slower adsorption process, corresponding to power densities of about 0.3 kW/kg. The results were used for sizing a full-scale adsorber, whose expected Volumetric Cooling Power is 500 kW/m3.
This paper experimentally investigates the direct integration of 3.15 kg of phase change materials (PCM) into a standard vapour compression system of variable cooling capacity, through an innovative lab-scale refrigerant-PCM-water heat exchanger (RPW-HEX), replacing the conventional evaporator. Its performance was studied in three operating modes: charging, discharging, and direct heat transfer between the three fluids. In the charging mode, a maximum energy of 300 kJ can be stored in the PCM for the cooling capacity at 30% of the maximum value. By doubling the cooling power, the duration of charging is reduced by 50%, while the energy stored is only reduced by 13%. In the discharging mode, the process duration is reduced from 25 min to 9 min by increasing the heat transfer fluid (HTF) flow rate from 50 L·h−1 to 150 L·h−1. In the direct heat transfer mode, the energy stored in the PCM depends on both the cooling power and the HTF flow rate, and can vary from 220 kJ for a cooling power at 30% and HTF flow rate of 50 L·h−1 to 4 kJ for a compressor power at 15% and a HTF flow rate of 150 L·h−1. The novel heat exchanger is a feasible solution to implement latent energy storage in vapour compression systems resulting to a compact and less complex system.
The European Energy Efficiency Conference 2021 shows how we can make a green recovery happen in practice and how energy efficiency is a cornerstone of this deep transformation.
What is it all about?
Europe has the ambitious goal of becoming the first climate neutral continent by 2050. The Green Deal and the EU Climate Law are first concrete steps. The current economic challenges are also an opportunity to accelerate decarbonisation and to create a fairer society and a more competitive economy.
In 2021, the conference – which attracts over 400 participants from over 50 countries each year – shows how we can make a green recovery happen in practice and how energy efficiency as an investment engine can contribute to this deep transformation.
HYBUILD is preparing a workshop at the 2021 European Energy Efficiency Conference in which the first results from its pilot sites, which are demonstrating the impact of the overall hybrid storage system, will be presented.
The use of Thermal Energy Storage (TES) in buildings in combination with space heating, domestic hot water and space cooling has recently received much attention. End of 2019, the CHESS-SETUP H2020 project organised a webinar in which HYBUILD participated together with two other research projects RELaTED and SunHorizon.
A new scientific paper published by the GREiA Research Group (Universitat de Lleida) and the Center for Energy of AIT (Austrian Institute of Technology) has been released on the Energies journal.
Monitoring of the state of charge of the thermal energy storage component in solar thermal systems for space heating and/or cooling in residential buildings is a key element from the overall system control strategy point of view. According to the literature, there is not a unique method for determining the state of charge of a thermal energy storage system that could generally be applied in any system. This contribution firstly provides a classification of the state-of-the-art of available techniques for the determination of the state of charge, and secondly, it presents an experimental analysis of different methods based on established sensor technologies, namely temperature, mass flow rates, and pressure measurements, tested using a lab-scale heat exchanger filled with a commercial phase change material for cooling applications.
The results indicate that, depending on the expected accuracy and available instrumentation, each of the methods studied here can be used in the present application, the deviations between the methods generally being below 20%. This study concludes that a proper combination of two or more of these methods would be the ideal strategy to obtain a more reliable and accurate estimation of the state of charge of the latent heat thermal energy storage.