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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.  

Our partner Wim Boydens is talking on 9 Feb 2021 10.30am CET about our hybridGEOTABS project at this EHPA online seminar bit.ly/3hS6pei: Technology Demonstrators: Heat Pump technology and processes of the future. The aim of the event is to present 4 Demo Sites of innovative Horizon 2020 and Interreg projects that use Heat Pumps. More in details: Introduction by Serena Scotton (EHPA) hybridGEOTABS - Wim Boydens (Boydens Engineering) REWARDHeat presentation Heat4Cool - Antonio Mingo (Solintel) GeoAtlantic - Lynda Mitchell (ALIenergy)

  Designing hybridGEOTABS Comfort supplied in a sustainable way! 17th December 10.00 - 12.45 CET Webinar description 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 introduces the hybridGEOTABS concept and its main benefits and challenges, providing insights into the technical principles underlying the concept and the design. The performance and feasibility of hybridGEOTABS are influenced by the design of the building, and the optimal sizing of the hybrid systems is an interesting design question. To support designers in the earliest stages of the design, a new design method is developed and its outcomes are made available via tools. The training provides general design guidelines, and an introduction to the tools and their background. Finally, the control of hybridGEOTABS buildings using model predictive controls is introduced, and what are important aspects to consider during the HVAC-design. Audience The training is targeting building and/or HVAC-designers (architects, HVAC-engineers), architecture and engineering students.  Modules The hybridGEOTABS concept unravelled (30 mins) hybridGEOTABS design principles (50 mins) Tools for feasibility study and pre-design (40 mins) MPC for HVAC-engineers (20 mins) Conclusions / Q&A (25 mins) Speakers Prof. Wim Boydens, Boydens Engineering Prof. Jelle Laverge, Ghent University Dr. Eline Himpe, Ghent University Dr. Damien Picard, KU Leuven Duration 2 hours 45 mins Register and find out more here: https://bit.ly/35pjF5j

Introducing hybridGEOTABS: Comfort supplied in a sustainable way!   25th November 10am-12noon CET Register and find out more here: https://bit.ly/35m6guX   Webinar description 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. This training introduces the hybridGEOTABS concept and its key assets and is accessible for everyone fascinated by sustainable building. Audience Ideal for everyone interested in sustainable and comfortable buildings, targeting stakeholders in the wide building and energy sector: building owners and managers, building and energy professionals (e.g. architects, HVAC- and control-engineers, contractors), policy-makers, researchers, architecture and engineering students... Modules What is hybridGEOTABS? - Wim Boydens, Boydens Engineering (20 mins) hybridGEOTABS - Comfort & Health - Ongun Berk Kazanci, Danish Technical University and Rick Kramer, Maastricht University (20 mins) hybridGEOTABS & Sustainability - Eline Himpe / Jelle Laverge, Ghent University (20 mins) What you need to know about MPC! - Damien Picard, University of Leuven (20 mins) Cost and Benefits: People-Planet-Profit - Lukas Ferkl, Czech Technical University & UCEEB (25 mins) Conclusions/Q&A - Wim Boydens (15 mins) Duration 2 hours Register and find out more here: https://bit.ly/35m6guX

Register for our Training Webinars this Nov and Dec! Introducing hybridGEOTABS: Comfort supplied in a sustainable way! 25th Nov - 10:00-12:00 CET Register and find out more here: https://bit.ly/35m6guX Ideal for everyone interested in sustainable and comfortable buildings, targeting stakeholders in the wider building and energy sector: building owners and managers, building and energy professionals (e.g. architects, HVAC- and control-engineers, contractors), policy-makers, researchers, architecture and engineering students… and, if this webinar whets your appetite, and you want to go into more depth, design a hybridGEOTABS system in your building…   Designing hybridGEOTABS: Comfort supplied in a sustainable way! 17th Dec - 10:00-12:45 CET Register and find out more here: https://bit.ly/35pjF5j Targeting building and/or HVAC-designers (architects, HVAC-engineers), architecture and engineering students.