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KU Leuven will be presenting at the Intelligent Buildings Operation Workshop in Boulder Colorado, Aug 7-9 2019 'Development and impact of a borefield controller model for Model Predictive Control’ Iago Cupeiro Figueroa, Damien Picard, Lieve Helsen This paper is result of collaboration within IBPSA Project 1, also supported by the hybridGEOTABS project ‘The strength of white-box model predictive control in buildings’ Filip Jorissen, Damien Picard, Lieve Helsen   ‘State estimation of control-oriented white-box models for buildings’ Jan Drgona, Iago Cupeiro Figueroa, Lieve Helsen          

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Dear Practitioner, Part 1 - Intro The hybridGEOTABS project was born after a simple realisation that (hybrid)GEOTABS, although based on proven technology and one of the most energy efficient building solutions available on the market, was unfortunately seldom implemented in practice - and more specifically did not go very far in the race against other more traditional fossil fuel based technologies during early design. We believe that the main reason behind this is due to the high level of system integration required, which can be a significant challenge for HVAC designers and architects during the early design phases. After reviewing the existing methodologies available, it became clear that one major hurdle is the lack of available design sizing guidance and user-friendly tools that all HVAC designers usually rely on to get started with a design. For example, if you combine GEOTABS with a secondary heating and cooling system, what is then an optimal sizing for both systems? In answer to this, the hybridGEOTABS project team developed a reliable and user-friendly tool for the feasibility study and pre-design of hybridGEOTABS buildings.   Part 2 - On what is our hybridGEOTABS design method based? Research and development towards a new hybridGEOTABS design method.   The new sizing methodology is based on splitting the heating and cooling demand of a building into a baseload that is covered by GEOTABS, and a remainder load, covered by the secondary systems. The load splitting algorithm is capable of working out the best size for the primary system components for you. On the other hand, dynamic building energy simulations of a variety of buildings in the EU building stock are performed, allowing the identification of heating and cooling demand curves for a wide range of buildings and building properties. The resulting building stock database eliminates the need for time consuming dynamic simulations by the building designer that are usually required for hybridGEOTABS design. The sizing methodology is also validated by comparison with a more complex control-integrated sizing approach, that allows to quantify the effect of different control strategies on the key component sizing. Because, in the hybridGEOTABS project, a semi-automated new and innovative control technique for hybridGEOTABS buildings is further devleoped, using a white box model predictive controller (MPC) which will help to further optimise the building operation and reach its optimal performance, with an additional 15-30 % savings in practice compared to a rule based controlled (RBC) similar building.   Having such a controller implemented on a building will also enable the drastic cutting down of control design engineering costs as well as installation costs that are normally associated with this high level of system integration. The MPC controller will be installed and commiissioned in  less time than required in a conventional control design, therefore reducing further the commissioning time (and cost). Its outlook towards predictive maintenance and automated fault detection is within reach. During the last year of the project, the main focus of the project will be clearly on wrapping up the results and rolling out a user friendly design tool as well as a guidebook to translate and apply these results into practice.   Part 3 - How will this design tool benefit you?   During this last upcoming year of the project, the main focus will be on wrapping up the results and rolling out a user-friendly design tool as well as a guidebook to translate and apply these results into practice. The design tool will be equipped with a user-friendly interface for simple data input: only few basic building geometry, building physical and boundary condition parameters will be required. The ultimate objective of the tool is to show the feasibility of hybridGEOTABS by answering questions such as: Is comfort guaranteed in the building? What is the payback time? and calculate key component size and performance estimate (primary energy & CO2 savings).   It will display 3 main outputs (or results):   The early design size estimation of each system (primary vs. secondary components) and therefore the degree of hybridity of the building concept, based on the monthly heat balance of the building over one year. This will be complemented by an annual bore field heat balance to decide if or to what extent is regeneration of the ground heat storage necessary. A set of graphs showing the building load patterns for 3 representative weeks (winter, summer, and a transition seasons) helping the HVAC designer to gain further insight regarding the daily amplitude of the building peaks, based on the load duration curve generated for the building. This will define the level of hybridity required on the emission side (e.g. between 30-100 % TABS) and also what type of secondary emission systems is required (e.g. no need for a secondary emission system, or 2, 3, or 4-pipe fan coil units building ventilation only, etc.) A decision making table displaying the different design variations with a simple comparison of payback times, CO2 savings and comfort levels summary (and all other relevant information required during feasibility and pre-design stages that can be easily derived from the results).   With this streamlined sizing method and interface tool putting our research results into practice, we believe to have eliminated some major design hurdles like the need for costly and time consuming simulations. Any HVAC specialist should then be able to size and draft a hybridGEOTABS concept in the same way as he would perform any other conventional design calculation, thus creating a fair level playing field for the possible concept approaches. All these concurrent measures developed in our research project should ensure that hybridGEOTABS solution is no longer overwhelming for building practitioners and also become a standard option to investigate right from the start of a building project, clearly displaying its potential in terms of energy-efficiency, costs and sustainability.

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Towards optimised performance, design and comfort in hybridGEOTABS buildings hybridGEOTABS presented a 1.5hr workshop on Tuesday 28th May on the second day of CLIMA2019, concluding the REHVA-organised afternoon sessions. The workshop was chaired by Lieve Helsen (KU Leuven). The attendees had the possibility to learn the advantages of radiant heating and cooling systems from an energy and comfort perspective and how these are designed in the context of the overall optimisation of hybridGEOTABS systems, being introduced as well to innovative design procedures for these systems.   The CLIMA hybridGEOTABS workshop presentations:   Introduction to hybridGEOTABS - Eline Himpe, UGent Indoor Environment Quality benefits of Radiant Systems - Ongun B. Kazanci, DTU TABS in hybridGEOTABS - Qian Qang, Uponor PCM ceiling panels as a renovation solution in hybridGEOTABS buildings - Ongun B. Kazanci, DTU Innovative Procedures for the Optimised Design of hybridGEOTABS buildings - Wim Boydens, Boydens Engineering hybridGEOTABS Design Method - Jelle Laverge, UGent  

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How to design hybridGEOTABS buildings’ components This was the first training course provided by the hybridGEOTABS consortium partners.  The course was well-attended and feedback was positive on the training provided. The aim is to provide the Training material in the form of a Guidebook which will be available to buy from the REHVA eshop. hybridGEOTABS refers to the efficient integration of the combination of GEOTABS (GEOthermal heat pumps in combination with Thermally Activated Building Systems (TABS)) and secondary heating and cooling systems in a building. Teachers Lieve Helsen from KU Leuven, Qian Wang from UPONOR, Pieter Brepoels from Viessman and Hector Cano Esteban from GEOTER illustrated the key aspects of borehole design, heat pump requirements, distribution systems related to TABS and the potential of MPC in this new approach. The aim was to introduce to the attendees the design and optimization of the borefield from an economical and security of thermal supply point of view, the construction and system integration of TABS, the advantages of TABS and its suitable application in the respective building type and energy systems. And how a MPC approach works, which benefits it can create and why it has especially advantages when applied in hybridGEOTABS buildings.

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Professor Wouter van Marken Lichtenbelt and Dr. Rick Kramer, our partners from the University of Maastricht, introduce their involvement in the hybridGEOTABS project and research.   The research discipline of Indoor Environmental Quality links the indoor environment of buildings to people. IEQ involves many aspects such as Air, which is mainly studied in the context of health, and Sound, Light and Temperature, which are mainly studied in the context of comfort. So, when we read or hear about health effects of the indoor environment, chances are high that it relates to ventilation or other aspects of air quality control. However, the research group TherMU of Maastricht University centres its research around the health effects of Temperature on humans’ physiological processes including thermoregulation and energy metabolism. Main emphasis of the research of TherMU is on individual differences in whole body physiology and the underlying mechanisms on cellular level, and on applying the scientific knowledge into the built environment. The fundamental aspect of the research line is the effect of environmental temperatures as we encounter in daily life on physiology and (thermal) behaviour. Prof. Wouter van Marken Lichtenbelt was the first to put mild cold exposure and the physiological responses, such as non-shivering thermogenesis, on the international research agenda in the early 2000s. In follow-up studies his group was among the first that identified functional brown adipose tissue in adult humans. Brown fat is an important tissue to study that links to a healthy metabolic profile. Follow-up studies by TherMU showed that in adult humans brown fat is a flexible tissue that can be activated and recruited by regular mild cold exposure and weight loss. Moreover, the results show that such cold acclimation results in an improved glucose metabolism (increased insulin sensitivity in diabetes patients), a shift in comfort and increased thermal resilience. Interestingly, recent studies on mild heat exposure and acclimation have also shown beneficial effects on metabolic and cardiovascular health. Fig.1 - Office work in the climate/respiration chamber   All in all, these recent studies show that thermal variation can be healthy and that we should change our attitude from a tightly controlled indoor environmental temperature towards a more dynamic profile. Therefore, an important research line of TherMU is on how environmental conditions (indoor climate) relate to thermal comfort, long-term health and prevention of the metabolic syndrome (obesitas, type2 diabetes and cardiovascular diseases). This research bridges the gap between basic physiology and health in daily living environment (care centres, dwellings and offices). UM works together with DTU in Work Package 5 - People planet profit validation: researching the impact of GEOTABS on indoor environmental quality (IEQ) aspects, including comfort, health and productivity, and defining key performance indicators (KPIs) for their valuation. Therefore, demo buildings are used to conduct experiments. Out of an inventory of existing GEOTABS buildings, a selection of demonstration buildings was made: a school building in Libeznice (Czech Republic), ‘Ter Potterie’ elderly home in Brugges (Belgium), ‘Solarwind’ office building in Windhof (Luxembourg), and, recently added, Infrax office building in Dilbeek (Belgium). Currently, indoor climate measurements and questionnaires are conducted in the demo buildings. Ultimately, the demo buildings and their occupants will be monitored while running on conventional control and with MPC, enabling us to compare the KPIs in the MPC scenario to the KPIs using conventional control.

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"How to express hybridGEOTABS in the ALDREN Evaluation Scheme?" The joint workshop was held on March 27, 2019 at the Technical University of Denmark (DTU), Kongens Lyngby. During the morning, a working session was held between ALDREN and hybridGEOTABS to exchange experiences and knowledge amongst the partners in order to explore potential working practices between both projects. Discussions led to the potential of applying the ALDREN methodology in at least one of the pilots of the hybridGEOTABS' project. During the afternoon the workshop was open to the public attended by about 65 people (approximately 40 in person and 25 via webinar).   The full video of the workshop can be viewed here   Summary of the presentations and links   The ALDREN procedure presentations:   Introduction to ALDREN – Mathieu Rivallain, CSTB EVCS ratings - Jana Bendžalová, ENBEE Energy Performance Verification - Robert Cohen, Verco Indoor Environmental Quality (IEQ), Productivity and Health - Pawel Wargocki, DTU Financial Performance - Yona Kamelgarn, Certivea ALDREN Building Renovation Passport & Renovation Strategies - Marta Maria Sesana, PoliMI   hybridGEOTABS - Radiant Heating & Cooling, IEQ, Health Productivity and Comfort presentations:   The history of TABS and its worldwide applications - Bjarne W. Olesen, DTU How to design a hybridGEOTABS building? (state-of-the-art) - Wim Boydens & Jelle Laverge, UGent Innovative controls in hybridGEOTABS: MPC concept and first results - Jiri Cigler, Energoklastr Indoor Environmental Quality Productivity and Health – Pawel Wargocki, DTU Innovations in radiant heating and cooling systems: use of PCM - Ongun B. Kazanci, DTU   The session ended with a live poll among attendees from both research and industry. You can read the results from the polls here: ALDREN poll and hybridGEOTABS poll   A Questions and Answers session followed the end of the workshop, providing some more insight into both projects:   ALDREN Q&As   Is there a definition of the  Nearly or Net-Zero Energy Building  (NZEB) at the EU level or only at the National levels? Jana Bendžalová: ALDREN has its definition of Nearly Zero Energy building (NZEB) in class A. The value is not necessarily fully in line with the national definition commissioned by member states because of many differences in calculation methodologies, indicators (e.g. total or non-renewable primary energy), floor area, primary energy factors, export of produced energy from RES etc.  The definition is tested on model buildings with the national input values for thermal envelope and systems properties.  The definition of ALDREN NZEB for office buildings in term of non-renewable primary energy use is close to the Commission recommendation (EU) 2016/1318 on guidelines for the promotion of nearly zero-energy buildings and best practices. Robert Cohen: Just a quick comment that the European Green Building Councils are also defining zero-energy buildings for the World Green Building Council, so there are national definitions being developed at the moment.  The Dutch Green Building Council has come up with a definition called the Paris Proof concepts, which is really interesting.   Should the renovation passport use or integrate BIM? Marta Maria Sesana: For sure within the ALDREN procedure we are going to investigate this aspect.  One module of the ALDREN BuildLog is title and structured to collect Documentation and BIM.  It's definitely another big issue to investigate, and the desire of ALDREN is to go on that path.   It was presented that the building passport should be taken with the building for it's lifetime.  How do you envisage who will manage this - who are the actors during this process, and what are their roles? Marta Maria Sesana: When we started to structure the data model of the ALDREN Building Renovation Passport in detail, we were aware on the need to keep in mind that along the path there are different 'actors' and their knowledge, background and expertise are not the same. For that reason we have structured it with different Level of Information (LoI) or let’s say Level of Detail (LoD) to not lose data quality, but at the same time to reach different target people. People trained by the ALDREN approach should fill in the ALDREN BRP and for them we are preparing dedicated training material and the pilots will be the first real application of the approach. LoD will support a better comprehension for different actors. For that reason we are also looking at a lightversion, I mean a more friendly version, with few but comprehensible indicators or clear rating even for the building owner or user. Some building passport initiatives already exist, but they are focused on residential buildings, so ALDREN will be the reply for the non-residential ones. In all LoI, the different actors need to understand what exact data they are referring to; which indicators or which energy they should consider, which renovation strategy, and when they should apply it and so on.  The importance of a common language and the data quality will be the key to have a user friendly and comprehensible tool to trigger renovation. Along the ALDREN approach, users can give feedback for example, but they wouldn't be the person who updates the passport/logs. Mathieu Rivallain: We can also slightly reposition this question in line with what we do with EPCs. This passport is not the only item of building documentation that is supposed to be revised over time and performed, for example, every 10-years because it has a certain validity.  In line with EPCs, we could figure out that EPC assessors could be responsible for updating the building information and building documentation, at least with respect to some topics. Related to energy ratings, this is quite direct. The inclusion of health and wellbeing parameters, depending on how far we go, could also be introduced in this vision. The question of meeting the targets between predicted and actual performance is maybe to be dealt slightly differently, because this issue is to be considered when we renovate the building. If we just exploit the building without a renovation programme or plan, maybe the strategy could be slightly different. Some companies offer their services to perform this analysis along with the deep renovation process. Depending on the topic, perhaps the professionals to be involved can be different, but not yet totally conclusive. Robert Cohen: I was at a very large meeting of financial investors who are interested in the building passport, not really for understanding the energy situation in a building, but to understand the investment potential for the property.  If they have this data digitally they can play this financially, and that is also why there is a lot of interest in the building passport.   hybridGEOTABS Q&As   How do you deal with the fresh air and ventilation in hybridGEOTABS? (There is a system that uses the slab to condition fresh air, is that considered?) Bjarne W. Olesen: We don't use that, but there's always a ventilation system, and often when building with TABS this is used as a secondary system to provide some cooling or heating, and if you need dehumidification. In that case it works as the secondary heating/cooling system. In othercases there may be another secondary heating system, but often it's the air system, which you have for the ventilation that's being used. But to use air to heat or cool the slabs - we know it was first introduced in Sweden many years ago, and there is a company promoting it in the UK. The difference here is energy is still carried in the air, but we want to carry so much of the energy as possible in the water, because it is more energy efficient.  Plus, there has also been discussion about how clean the channels in the concrete are, and what are the risks for bad air quality and so on. Wim Boydens: Air activated TABS are used in practice here and there, e.g. in Luxembourg, but to our opinion are especially reserved for buildings where a balance between fresh air demand and thermal demand is found, as well as the installed volume flows needed for these purposes, taken in to account the time shift that can be integrated for the thermal demand. The outdoor temperature profiles ( day-night ), as well as the building envelope and the internal loads are determining the suitability as well. As such, this concept could find cases where the advantages of night cooling and free cooling could be strong deciding factors. For example, the concept has been elaborated and proposed by our boydens engineering office in a competition for a large technical school, with passive building envelope, high occupation density, and high glazing factor for daylight purposes. In this case, the air flow was continued and controlled at night time to cool down the concrete for the next day. During day time the radiant/convective effect of the slab added to the cooled down ventilation supply by the cool core of the slab. In winter period the core was preheating the ventilation air in daytime. The fast reacting secondary system provided the additional needed heat depending on the internal loads. The concept looked promising, however challenging for the control that should obviously be predictive. But, as in so many cases, the architecture was by far the determining factor of the jury, even if they had put forward a high weight to the sustainable energy concept. Maybe the concept, even if it was rather simple, was not very well understood. Sometimes human limitations are decisive, our should we say all times?   I was very interested by the phase-changing materials being connected to Photovoltaics, especially in the night? Ongun B. Kazanci: The main idea is that we have the PCM panels in the room, removing heat from the room, so you need to get rid of that heat somehow. The photovoltaic and thermal panels (PVT) are on the roof, and normally you would install for electricity, and if you have the 'T' (thermal) you can also get some heat out if it, but you can also use them for cooling if you circulate water through them, radiating heat to the sky. We have some storage tanks in between, so they are not connected directly to the PCM panels.   Are the phase-change material panels already commercialised or not? Ongun B. Kazanci: The ones we showed are the ones we are testing are the only panels that exist, and not commercialised. So we took what was existing, tried to combine them, but found they weren't optimal for our purposes, so took a lot of time and testing. Bjarne W. Olesen: There are some other panels on the market; the first one we used was a commercial product that was able to buffer humidity.   What about using gypsum panels? Bjarne W. Olesen: But, is there piping in them? We are only talking about those that you can activate with piping. The problem with PCM is that you can use them as passive, and maybe use night air cooling to generate or make them solid again, but the heat conductivity is so bad, you need to have a very good connection where you want to remove / supply heat.   The only point was that there are gypsum panels already available and whether it is simple to just integrate some pipes? Bjarne W. Olesen: We did look at that because we took one of those gypsum boards and just had a standard suspended metal radiant panel. We thought the easy way is to take existing products. So we took 1.5-2cm gypsum panels, and made a good contact with the metal surface of the radiant panel, but it didn't work that well because of the heat conductivity. So the best way is to have the pipes within the panel. Ongun B. Kazanci: We want something that we can control, within a panel as it's not just increasing thermal inertia/mass in the room, but have something that we can do more with. There have also been some ideas to increase conductivity by using graphite in the construction, but the prices just go up, and it becomes very expensive.   Who is going to sell the MPC solution that you are developing and how it will be packaged, and by which partner? How will you do this market uptake after the project? Jiri Cigler: Energoklastr or the new start-up company set up by KU Leuven - TACO are partners who intend to take this up. One possible business plan would be, in the case of new buildings, to design and build the building by one company who also develops the model that can also be used for the validation of the design. Then this model can be used directly for MPC.  This makes sense compared to current practice, there are big savings in this development in cost and commissioning, as it no longer takes 2 years to commission a TABS system, but 1-2 months to set up all communications and then it should work. Filip Jorissen: Another possible business plan is to have existing control companies implement MPC as a substitute for RBC. Eline Himpe: We are working on a business plan within the project and there will be more outcome during the coming year.   What do you know about the cost effectiveness of MPC and PCM, depending on the current state of the building, if it is already an energy efficient building? These savings are very well evaluated using heating degree base data and so on, but in this case there is no benefit of MPC for example on the heat pump efficiency.  With GEOTABS buildings, the lower the peak load, the better the COP, would increase the potential of MPC much higher than the 23% improvement.  There have been comparison between RBC and MPC in the case of hybridGEOTABS buildings and the savings have been higher than 50%. Bjarne W. Olesen: For some of the bigger markets, they would implement it. Also for the need for continuous maintenance of a system, which you can combine with MPC. So I certainly think there is a market for it. Filip Jorissen: Depending on the implementation, the cost effectiveness does not rely only on energy savings, i.e. we hope to show using the demonstrations that MPC has improved robustness and that MPC requires less implementation time and less commissioning. Furthermore, variable electricity prices and improved fault detection and fault handling can be integrated, and besides cost savings substantial sustainability gains can be realised by e.g. increasing the share of renewable and residual energy sources (R2ES), long-term sustainable use of the underground, use of low-exergy systems … if ‘the polluter pays principle’ is appropriately implemented, this evidently also results in cost savings. Wim Boydens: If you compare the MPC solution with continuous commissioning, it is clear who scores best in the whole investment and operation cost. Continuous commissioning is always present in a way, even if it is done in a non exemplary or only corrective way by just reacting when problems occur. The (loan) cost of these interventions are huge, but hidden in maintenance costs for bigger buildings.  

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