A new report led by our partner AIT – the Austrian Institute of Technology – is now available on the Deliverables page of the website.
The HYBUILD public report “Full hybrid storage integrated” describes the integration phase of the hybrid storages for the Mediterranean and the Continental concept in the laboratories. Special focus was put on the hydraulic and electric integration of the main components. With this report, the knowledge about the integration of the specific components of the HYBUILD concepts is passed to the demo sites inside the HYBUILD project, where the technologies will be installed. Furthermore, it may help researchers and developers working on future experiments with the same or similar components. Therefore, potential problems in the system integration can be identified in advance.
A new HYBUILD report led by our partner AIT – Austrian Institute of Technology – has just been released. It presents research outcomes from HYBUILD related to the Distributed Control System (DCS).
Executive Summary of the report
This report provides a comprehensive description of the hard- and software communication interfaces between all actors, sensors, built-in controllers of the components and modules of the hybrid thermal and electrical sub-systems, and the existing automation systems used in the laboratory infrastructure at ITAE, NTUA, CSEM and AIT. The report gives detailed information on their configuration, developed human machine interfaces and interfaces to software for advanced control and simulation.
A new HYBUILD public Report led by our partner CNR is now available on the Deliverables page of the website.
Executive Summary of the report:
The present work describes the activities performed to develop the prototype of the electric energy storage system of the HYBUILD project. The final purpose of the work done was to choose, test, and assemble the electric energy storage system.
The first action performed was to identify the behaviour of the use cases in realistic conditions,
considering a wide range of operation. To this aim, the two Mediterranean and Continental
systems were considered. In particular, the optimized behaviour for summer conditions
(Mediterranean HYBUILD solution) and winter conditions (Continental HYBUILD solution) were
taken into account. In the Mediterranean system, the electric storage mainly serves the vapour
compression heat pump for cooling production, whereas in the Continental system the electric
storage serves the vapour compression heat pump for heating production. Furthermore, in the
Mediterranean system, DHW is mainly produced directly from solar or through a back-up,
whereas in the Continental system DHW production is obtained through the RPW-HEX
accumulating condensation heat of the heat pump during its operation. In both cases,
therefore, no extra operation of the heat pump for DHW was considered. A 4.5 kWp system
was considered for the Mediterranean solution and a 6 kWp one for the Continental case. This
is due to different size of case studies, since the Mediterranean HYBUILD system is intended
for a single-family house, while the Continental solution is intended for multi-family houses
with 2-3 apartments with shared renewable energy production. Cyprus solar irradiation profile
was used for the Mediterranean case and Bordeaux for the Continental one.
The worst-case scenario was considered for testing: in the Mediterranean case, a day in July
(high cooling demand), determines an electric consumption of the heat pump of 1.5 kW,
corresponding to a heat pump with 5 kW cooling capacity and EER=3.3 (thanks to operation in
combination with the sorption module). In the Continental case, a typical winter day was
selected, corresponding to very low irradiation and therefore a lower production from the PV
field but a higher demand from the user.
After definition of the applications, a selection process among most performing electric
storage technologies was performed. In particular, attention was immediately focused on
Lithium-ion batteries due to guaranteed performances. Lithium ion batteries offer countless
advantages over other types of electrochemical storage such as:
very high specific energy (Wh/kg) achieving considerable weight and space savings;
low internal resistance, allowing them to achieve higher currents, therefore charges and discharges at high c-rates, and making them suitable for high power applications;
limited self-discharge rates, making them the best solution for long-term energy storage;
no memory effect;
high lifetime, especially for some specific chemistries;
high open-circuit voltage (typical values of 3 – 4 V except for lithium titanate where the cell voltage is in the 1.5 V – 2.7V range);
relatively flat discharge curves (Voltage – SoC) in a wide range of SoCs.
The integration of the heat pumps in a DC microgrid requires suitable converters, which were selected according to technical and economic constraints given by CSEM. In particular, recommendations were made for the AC/DC grid converters, the DC/DC converters for the integration with the electrical storage and the DC/DC converter for PV systems that might be available. In addition, a user interface was realised, to simplify monitoring and supervision during the installation in HYBUILD demonstration sites.
Abstract of the presentation and conference paper : With the diffusion of electric heating and cooling devices, coupling the electric and thermal systems in the residential sector is becoming attractive and could help to increase photovoltaic penetration. The heating and cooling needs of buildings correspond to an important component of the total energy consumption of the residential sector. Thus, it is important to properly design the thermal and electric systems accounting of the interactions from the first phases of the design process. In the design phase, detailed models implemented in dynamic simulation tools can be used for the sizing process of system components, but they hardly can be adopted in optimization algorithms due to the computational time required for each simulation. This is particularly true for multi-objective optimization algorithms, where usually a wide number of simulations is required. In this work, TRNSYS was used to train a machine learning model that is used in a multi-objective optimization with the final goal of improving the design of the thermal system and optimizing the KPIs of a coupled photovoltaic plus battery system.
The full conference paper is now available in the event proceedings, accessible here (link for a direct download here).
A new HYBUILD public report led by our partner CNR ITAE is now available on the Deliverables page of the website.
Executive summary of the report
This report describes the activity regarding the development of the sorption module, that is an essential part of HYBUILD Mediterranean solution, since it allows the operation of the compression with high efficiency by storage and conversion of solar energy.
Paraffins as phase change material in a compact plate-fin heat exchanger – Part I: Experimental analysis and modeling of complete phase transitions
Abstract: Thermal energy storages with phase change materials (PCM’s) based on plate-fin and tube-fin (gas-to-liquid) heat exchanger (HEX) designs show a comparatively high heat transfer performance and compactness. High heat transfer rates allow for optimal storage designs and operation close to the PCM’s phase change temperature. However, industrial-grade solid–liquid PCM’s and mixtures usually show a non-isothermal phase change behavior over an extended temperature range, sometimes with multi-step transitions, hysteresis and supercooling. These complex phenomena depend on the physical dimensions of the PCM in the HEX and the operating conditions. They need to be verified for each particular application and cannot be neglected. This contribution presents an experimental and model-based analysis of the phase transition behavior of three commercial paraffins filled in compact plate-fin HEX’s. The results indicate that non-isothermal phenomena critically affect the storage temperatures. Their impact on the thermal performance can be studied using relatively simple numerical models.
Paraffins as phase change material in a compact plate-fin heat exchanger – Part II: Validation of the “curve scale” hysteresis model for incomplete phase transitions
Abstract: Technical-grade and mixed solid–liquid phase change materials (PCM’s), such as commercial paraffins, can show a complex non-isothermal phase transition behavior, possibly with hysteresis and supercooling, two-step transitions and asymmetric phase transition peaks. Phenomenological modeling approaches can use data-driven methods to derive phase transition models represented by enthalpy–temperature or apparent heat capacity–temperature curves. These curves are then linked with simulation models for heat transfer in thermal storages with PCM’s. If the phase change is significantly affected by hysteresis, different curves might be tracked either for heating or for cooling. This “curve track” modeling approach is straightforward and easy to implement. However, it shows a poor performance considering conditions with interrupted phase change, which are relevant for the partial charging and discharging operation of thermal storages. This contribution presents a novel so-called “curve scale” model. Its superior performance is proved for three commercial paraffins and experiments with 31 interrupted phase change scenarios.
Quite a contrast when looking at the photovoltaics component of the HYBUILD hybrid storage system: under the snow in Langenwang, Austria, and shining in the sun in Aglantzia, Cyprus !
With its hybrid approach and its two versions, the HYBUILD solution aims to accommodate both Mediterranean climate where cooling is critical, and Continental climate where a stronger focus is put on heating demand.
Learn more about the HYBUILD technical system by watching this video, and follow the progress of the installations at the three demo sites (Austria, Spain, Cyprus) by monitoring their online photo albums on this page.
The workshop Renewable Heating and Cooling Solutions for Buildings and Industry at Sustainable Places 2020 brought together a selection of H2020 EU-funded projects involving experts from the biomass, geothermal, solar thermal, and heat pump sectors to discuss a common strategy for increasing the use of renewable energy technologies for heating and cooling for buildings and industry.