Report on performance tests on the operation of the electrical energy storage.

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.
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Pression heat pump tests successful

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.

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European Researchers Night in Greece

The National Technical University of Athens (NTUA), the oldest and most prestigious educational institution of Greece in the field of technology presented HYBUILD during the #EuropeanResearchersNight 

NTUA’s presentation was focused on decentralized thermal systems for the production of electricity, heat, and/or cooling, from renewable energy sources and waste heat from various processes.

You can watch the video from the Researcher’s Night and NTUA’s Prof. Dr.-Ing. Sotirios Karellas’ presentation (less than 4 minutes), below:

HYBUILD at the Researchers’ Night 2020 in Lleida, Spain

On November 27th, HYBUILD was presented at the #EuropeanResearchersNight 2020 by our partner University of Lleida, GREiA Research Group.

The European Researchers’ Night, funded under the Marie Skłodowska-Curie actions (MSCA), is a Europe-wide public event that brings researchers closer to the public. The Night provides researchers the opportunity to showcase the diversity of science and its impact on citizens’ daily lives, and to stimulate interest in research careers – especially among young people. The events highlight how researchers contribute to our society by displaying their work in an interactive and engaging forum.

Within the events celebrated this year (under the EU funded project EuNightCat20 – GA 954506), specific HYBUILD content such as posters were developed for this participation, with the aim to make HYBUILD research and results accessible for a wide audience.

Examples are provided below, and further information can be found on the ‘Europe’s corner’ as well as on the ‘Our Research’ page of the event.

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Techno-Economic Analysis of a Heat Pump Cycle Including a Three-Media Refrigerant/Phase Change Material/Water Heat Exchanger in the Hot Superheated Section for Efficient Domestic Hot Water Generation

A new journal publication presenting HYBUILD outcomes has just been released !

Integration of a three-media refrigerant/phase change material (PCM)/water heat exchanger (RPW-HEX) in the hot superheated section of a heat pump (HP) system is a promising approach to save energy for domestic hot water (DHW) generation in multi-family houses. The RPW-HEX works as a desuperheater and as a latent thermal energy storage in the system. The latent thermal energy storage is charged during heating and cooling operation and discharged for DHW production. For this purpose, the water side of the RPW-HEX is connected to decentralized DHW storage devices. DHW consumption, building standards and climate, energy prices, material costs, and production costs are the constraints for the selection of the optimal storage size and RPW-HEX design. This contribution presents the techno-economic analysis of the RPW-HEX integrated into an R32 air source HP. With the aid of experimentally validated dynamic computer models, the optimal sizing of the RPW-HEX storage is discussed to maximize energy savings and to minimize the investment costs. The results are discussed in the context of a return of investment analysis, practical implementation aspects and energetic potential of the novel technology.

Profit after 20 years of operation for (a) Case #1 (passive house located in Helsinki) and (b) Case #2 (low energy building located in Strasbourg). Markers “▼”, “●” and “▲” denote small (140 L), medium (210 L) and large (280 L) decentralized DHW storage devices. Please note that for some cases, no profit can be made after 20 years of operation, so they are not shown in the figures.

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Energy assessment based on semi-dynamic modeling of a photovoltaic driven vapour compression chiller using phase change materials for cold energy storage

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.

Read more here