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Model Predictive Control and Innovative System Integration of GEOTABS;-) in Hybrid Low Grade Thermal Energy Systems - Hybrid MPC GEOTABS

Periodic Reporting for period 3 - MPC-. GT (Model Predictive Control and Innovative System Integration of GEOTABS;-) in Hybrid Low Grade Thermal Energy Systems - Hybrid MPC GEOTABS)

Reporting period: 2019-09-01 to 2021-02-28

Heating and cooling of buildings constitutes a significant part of the energy use in the EU, and is therefore an important sector in the transition to a 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 and thermally activated building systems (TABS). TABS is a type of radiant heating and cooling emission system, well-known for its thermal comfort. The heating/cooling pipes are embedded in the mass of the building elements, activating them as thermal storage. TABS operates at close-to-comfort temperatures, allowing to operate geothermal heat pumps at a high efficiency. Moreover, in buildings with moderate cooling demands, passive cooling is possible at negligible energy cost. The geothermal source acts as a seasonal storage, and combined with the storage in the TABS, this enables an enhanced use of RES.
GEOTABS becomes a hybrid system by combining it with secondary heating and cooling emission and/or production systems. Because of their high thermal inertia, TABS require flexible complementary heating/cooling emission systems to swiftly react to variations in heating or cooling setpoint, ensuring thermal comfort and efficient operation at all times. On the production side, investments can become more competitive when providing a cheaper secondary supply system. This flexibility on the secondary side allows to develop hybridGEOTABS buildings for the different climates in EU, for different building typologies, for a broad spectrum of building designs and for various building energy concepts (e.g. all-electric building, NZEB etc.).
To realise the potential of this hybrid concept in reality, it does require an adequate system integration and smart control. In the hybridGEOTABS concept, the vital role of controlling the system is taken up by a Model Predictive Controller (MPC), which optimises the operational efficiency of the system in terms of energy, environmental and/or cost performance while safeguarding the indoor environmental quality (IEQ) constraints.
To allow for a wider implementation of this environmentally friendly technology in the EU market, this project tackles the major bottlenecks of the hybridGEOTABS concept. A first challenge is how to design such a hybridGEOTABS building? In order to give a fair chance for the hybridGEOTABS concept to be selected by the energy concept designer, an easy-to-use design tool is developed, that integrates the key properties of the building, the HVAC-systems and the control. A second challenge is the development of a suitable control system with MPC, that improves the energy-efficiency of the system. A semi-automated MPC toolchain is developed and MPCs are demonstrated. This leads to the third objective, that is to demonstrate the hybridGEOTABS concept in simulations and real-life buildings, and to assess its performance in terms of energy use, environment, IEQ, health, productivity and costs. The fourth objective is the establishment of a knowledge centre for hybridGEOTABS, called enerCORE, that will promote the concept and establishes the best practices, while guiding further development of the concept. The solution will support the industry and SME’s to expand their activities and strengthen competitiveness, resulting in an increased market share of energy efficient buildings.
The hybridGEOTABS book explains to the broader public the hybridGEOTABS concept, history and state-of-the-art, the control and design challenges and solutions developed in this project, the main assets and exemplary hybridGEOTABS buildings in Europe.
The hybridGEOTABS design webtool allows the energy concept designer, HVAC-designer and architect to assess the feasibility of hybridGEOTABS for their building project from the earliest stages of the design onwards. This tool links to a database with almost 150,000 pre-simulated and pre-engineered buildings. It is found that when using traditional (steady-state) HVAC-design methods, the sizing of hybridGEOTABS components is significantly overestimated, leading to an increased investment costs. The design tool is accompanied by a manual, training curriculum, design decision trees and hydraulic schemes and generic specification documents. For the detailed design of the geothermal borefield, the project demonstrates investment cost reductions of 7-11% using EGRT. As an alternative to TABS in context of building renovations, ceiling panels with integrated PCM were developed.
The semi-automated toolchain for developing the MPC allows using MPC for both high- and low- level control, increasing the energy use, cost savings and thermal discomfort reductions. The MPC solution is able to connect to any building management system that supports open communication protocols. Improvements of grey-box MPC were investigated. The MPC controllers are Smart Grid ready, to optimise the building control towards grid flexibility by using the thermal storage in GEOTABS.
During the project, MPC was implemented in four hybridGEOTABS demonstration buildings in the EU. The buildings are introduced on the project website and video. The improved system operation thanks to the MPC causes HVAC energy use reductions up to 37% in the simulations and up to 24% in real-life. The IEQ in all the demonstration buildings is rated good. The life cycle costs of hybridGEOTABS scenarios with and without MPC are similar, and about 0.5% to 4.6% higher than non-renewable HVAC-concepts.
The feasibility of hybridGEOTABS and its potential environmental impact on the newly constructed building stock in the EU is assessed. Looking at the variety of building designs in the EU, it is found that in all climate zones for half of the buildings, more than 50% of the heating and cooling demands can be covered by GEOTABS. The CO2-emission reductions are estimated by comparing the performance of hybridGEOTABS to the traditional non-renewable HVAC-solution, based on simulations of the relevant section of the EU building stock, accounting for 40% of the newly-constructed multi-family residential building stock area, and 50% of the newly constructed non-residential building stock area in the EU. It is found that GEOTABS reduces the CO2-emissions related to heating and cooling of new buildings in the EU by about 40%. Note that these savings are attributed only to the GEOTABS part of the building. By optimising the building design or by combining the GEOTABS core with other RES, further CO2-emission reductions can easily be achieved. Moreover, the combination of hybridGEOTABS with PV is found an advantageous solution in all EU climate zones, reducing the global financial cost up to 2%.
These results indicate the large potential of hybridGEOTABS in the EU. The newly developed design strategies, component optimisations and model predictive controls, demonstrated in real-life hybridGEOTABS buildings and supported by the enerCORE knowledge centre for hybridGEOTABS… they all have the potential to contribute to a broader implementation of the hybridGEOTABS concept that can play an important role in reaching the European targets on increasing energy-efficiency and RES, and reducing GHG-emission, thereby safeguarding quality of life of building users and architects’ freedom to create buildings that make a real difference… where architectural design qualities and sustainability meet!
hybridGEOTABS illustration and brand
Demo building: Solarwind office building (Windhof, LU)
hybridGEOTABS book cover
Case building: Infrax office building (Dilbeek, BE)
Demo building: Libeznice school (Libeznice, CR)
Demo building: Ter Potterie elderly care home (Bruges, BE)
Case building: Haus M multi-family building (Zürich, CH)