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Summary of the hybridGEOTABS Project After more than 4 years working on the project this document is a summary of the context and overall objectives of the project (For the final period, include the conclusions of the action) This includes: What is the problem/issue being addressed? Why is it important for society? What are the overall objectives?   The European Union has set a path towards a decarbonised society in 2050. The European Green Deal aims to reduce the CO2-emissions by at least 55% by 2030. Heating and cooling of buildings constitutes a significant part of the energy use in Europe, and is therefore an important sector in the transition to this low-carbon society. hybridGEOTABS is an HVAC-concept that provides comfort in buildings in a clean and sustainable way. The core of the concept is GEOTABS: a combination of a geothermal system (GEO) and thermally activated building systems (TABS). TABS is a type of radiant heating and cooling emission system that is well-known for providing high thermal comfort. The heating/cooling pipes are embedded in the mass of the building elements (e.g. concrete floor slabs), therefore activating them as thermal storage. By turning entire floor or ceiling surfaces into heating and cooling systems, TABS can provide very low-temperature heating (as low as 22 - 28°C) and high-temperature cooling (as high as 15 - 22°C). These temperatures are close to the temperatures available in the shallow layers of the underground, which allows to operate geothermal (GEO) heat pumps at a very high efficiency. Moreover, in buildings with moderate cooling demands (e.g. in central and northern Europe), the underground temperatures can be directly transferred to the TABS via a heat exchanger, providing passive cooling at negligible energy cost. The geothermal source acts as a seasonal storage, from which heat is extracted in the heating season and injected again in the cooling season. This seasonal energy storage, combined with the short-term thermal energy storage in the TABS, enables an enhanced use of renewable energy. GEOTABS is the comfortable and sustainable core of the hybridGEOTABS system.

It’s here! Our @hybridgeotabs Manual in print! and on our website! RENEWABLE AND STORAGE-INTEGRATED SYSTEMS TO SUPPLY COMFORT IN BUILDINGS: PRE-DESIGN AND CONTROL FOR HYBRIDGEOTABS PROJECTS After much effort and putting together the culmination of four years work on our H2020 project. Read about the history of GEOTABS, research and results, combinations of renewables, storage and GEOTABS to create a hybridGEOTABS building. There’ll be more happening - so keep a look out! Available on our website to download hybridgeotabs.eu/publications/guidebooks Thanks to everyone who contributed Authors: Wim Boydens, Lieve Helsen, Bjarne Olesen, Lukas Ferkl and Jelle Laverge Contributions from Hector Cano Esteban, lago Cupeiro Figueroa, Jan Drgona, Filip Jorissen, Damien Picard, Jan Drgona, Rana Mahmoud, Mohsen Sharifi, Josue Borrajo-Bastero, Lien De Backer, Pascal Simoens, Ongun Berk Kazanci, Rick Kramer, Josue Borrajo Bastero, lneke Schepens @iagocupeiro @kuleuven @boydens_engineering  @uceeb_cvut  @ugent @ugent_fea @dtudk @maastrichtuniversity Edited by Eline Himpe @himpeline Graphics manual design Cactus Creative Consultants Ltd. Kevin Little @rehva_hvac @spyridonpan Organising Publishing and Print #geotabs #hybridgeotabs #energysaving #renewables #groundsourceheatpumps #GSHP #climatecrisis #zerocarbon #DTU #maastrichtuniversity #KULeuven #CVUT #UCEEB #Boydens #UGent #HVAC #sustainabledesign #rehvahvac #rehva

Our hybridGEOTABS Training Curriculum is now available on our website as webinars and slides Providing very comfortable and healthy buildings in an energy-efficient, sustainable and financially viable way, and ready to play in the smart grid?  hybridGEOTABS buildings offer huge potential to meet the key goals for buildings in the European green deal. Building-integrated radiant heating and cooling systems and geothermal heat pumps are a match made in heaven, enabling very high energy efficiencies and the flexibility of thermal storage, while providing freedom of space and high thermal comfort to the user. The hybrid combination of this GEOTABS concept with additional systems, enlarges the application field to a variety of mid-size and large buildings throughout Europe. The smart controller (a Model Predictive Controller) continuously optimises the real-life building performance and can govern the interaction with renewables and the grid. hybridGEOTABS refers to the efficient integration of the combination of GEOTABS (GEOthermal heat pumps with Thermally Activated Building Systems) and secondary heating and cooling systems in buildings, controlled using model predictive controls (MPC). This technology offers huge potential to meet heating and cooling needs throughout Europe in a sustainable way, while providing a very comfortable conditioning of the indoor space.  This training comes in two parts, How to exploit hybridGEOTABS which introduces the hybridGEOTABS concept and its key assets and is accessible for everyone fascinated by sustainable building, and, How to design and operate hybridGEOTABS which introduces the hybridGEOTABS concept and its main benefits and challenges, providing insights into the technical principles underlying the concept and the design.   The training is an outcome of an intensive collaboration between building and HVAC-designers, industry and academia throughout the EU in the hybridGEOTABS project (2016-2020) that is funded by the European Commission under the Horizon 2020 programme.   

Design Decision Trees for Download This document provides decision trees for designing hybridGEOTABS and sizing the key components. The original document with the description of the methodology behind the decision trees is found in deliverable 2.5 of hybridGEOTABS project available on our website at hybridgeotabs.eu/technology

Our consortium partner Iago Cupeiro Figueroa will be presenting his PhD defence,  "Short- and Long-Term Optimal Control of Hybrid GEOTABS Buildings" on Weds 17 March at 15.00 CET. Register here: bit.ly/3ewte7p   This thesis investigates the optimal control of hybridGEOTABS buildings in both the short and long term and with the focus on the geothermal drilling field aspect. The energy intensity of buildings has decreased since the 1990s, but is not yet sufficient to compensate for the sharp increase we are seeing in the floor space of buildings. As a result of this we see a strong increase in the global energy use in buildings as well as in the related CO₂ emissions. More efforts towards energy-efficient buildings are therefore necessary. GEOTABS is a very efficient building concept that consists of a geothermal heat pump (GEO) that is connected to a thermally activated building structure (TABS) and is expanded with a fast-reacting supplementary production and / or delivery system. However, the anticipated savings of this concept are offset by the operational complexity, making optimal controllers such as Model Predictive Control (MPC) highly recommended. However, the time constant of the dynamic processes in the ground of the geothermal drilling field is much larger than the typical MPC prediction horizon. Therefore it is uncertain whether MPC (i) provides the optimal solution and (ii) will possibly deplete the soil in the long term. The first part of the thesis discusses in detail the problem mentioned above and the motivation that led us to this research. Furthermore, it introduces the reader to the basic concepts and tools we have used during the research.   The second part of the thesis focuses on methodological developments. In a first step, the MPC formulation is extended with the short-term drilling field dynamics by integrating a variable COP formulation and a dynamic drilling field model. The drill field ground model was adapted from an event-based load aggregation scheme to a resistance-capacitance network that represents the thermal diffusion in the ground. We were able to establish that the use of a variable COP leads to better control and smarter use of the heat pump and that peak loads are avoided. A drilling field model is necessary, especially when there is a risk of soil exhaustion. To investigate the long-term dynamics of the geothermal drilling field, a so-called “shadow cost” has been added to the objective function of the MPC. The drill field ground model has been adapted from an event-based load aggregation scheme to a continuous scheme. Using predefined heat and cooling needs, the optimisation has been expanded to include energy balance equations for each specific case, in order to calculate the optimal load split between the different systems. The drilling field fluid temperature is affected by the actions of the foregoing predictions and the short-term optimisation. The methodology has been validated and demonstrated, showing that there is potential in a step beyond the standard short-term MPC formulation. Since some states are hidden or unknown within the developed drilling field models, the accuracy of the models in an actual application remains to be seen. Therefore, condition estimators were tested and evaluated in both drill field controller models. A simple 1-step Kalman filter provides accurate results for the fast processes in the heat transfer fluid and well fill, while a more complex multi-step algorithm, such as “Moving horizon estimation”, is more suitable for the slower processes in the soil around the wellbore.    With the aim of testing the practical applicability of the methods developed in the second part of this thesis, the third part presents the application of these methods in an emulator of a real building currently working with the short-term MPC. The current MPC implementation of the building assumes a constant temperature for the drilling field, leading to a thermal imbalance. The addition of a drilling field model in the controller and the shadow cost in the MPC formulation further energy savings and reduce the thermal imbalance. The system was able to operate with a drill field reduced by 72.3% compared to its original size. The new methodologies worked well even under the limits of computational power constraints and model mismatch, demonstrating the flexibility and robustness of the developed methodologies.    The fourth and final part summarizes the main findings of the study and makes new research proposals for the future that, from the author's perspective, should follow this study.  

Our consortium partner Massimo Cimmino will be presenting a meet the jury,  “Simulation of borefield heat transfer in ground-source heat pump systems: Recent developments and future perspectives” on Tues 16 March at 16.00 CET. Register here: bit.ly/3vim3pq     Massimo's abstract: Ground-source heat pumps, coupled to vertical geothermal boreholes, are an energy-efficient method to meet the heating and cooling loads of buildings. In cold climates, ground-source heat pumps will gradually exhaust the ground thermal energy stores, resulting in lower returning fluid temperatures from the boreholes. A colder returning fluid temperature will typically cause a drop in heat pump efficiency. If the fluid temperature drops too low, the heat pump will no longer be able to operate safely or efficiently. A similar effect is seen in cooling-dominated buildings, where returning fluid temperatures gradually rise. The simulation of ground-source heat pump systems aims at predicting the returning fluid temperatures from geothermal boreholes and the ground temperatures in the bore field. The accurate prediction of these temperatures is critical to the evaluation of the ground-source heat pump performance and to the proper design of the system, i.e. the evaluation of the required borehole length and bore field layout to satisfy the building thermal demand.   The heat transfer process in bore fields evolves over several time and spatial scales. At short time scales (i.e. from minutes to hours), the effects of the transit of the fluid through the boreholes and transient heat conduction through the grouting material dominate the heat transfer process. At medium time scales (i.e. from weeks to months), thermal interference between the boreholes becomes significant. At long time scales (i.e. after several years), heat conduction in the ground becomes three-dimensional and boreholes see significant axial temperature variations. This seminar presents recent developments in simulation techniques for ground-source heat pump systems and demonstrates how these techniques are deployed to create accurate and computationally efficient simulation models.