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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - MPC-. GT (Model Predictive Control and Innovative System Integration of GEOTABS;-) in Hybrid Low Grade Thermal Energy Systems - Hybrid MPC GEOTABS)

Teaser

Summary

GEOTABS refers to the combination of a geothermal heat pump (GEO) with thermally activated building systems (TABS), and is applied in low temperature heating and high temperature cooling of buildings. TABS is a radiant system, beneficial in terms of thermal comfort and energy efficiency. Its high thermal inertia allows load buffering and peak load shaving. When combined with a heat pump, it allows to make very efficient use of low grade R2ES (renewable and residual energy sources). Therefore GEOTABS represents an eco-innovative technology that allows to substantially decrease energy use and greenhouse gas (GHG) emissions from buildings while improving indoor environmental quality (IEQ).
A number of bottlenecks currently prevent a real breakthrough of the GEOTABS concept. Current GEOTABS solutions are perceived too investment-expensive and they are often not operating at their full potential. Because of their high thermal inertia, TABS require flexible complementary heat emission systems to swiftly react to variations in heating or cooling setpoint, ensuring thermal comfort and efficient operation. On the production side, investments can be more competitive when providing a hybrid supply, and heat pump operation can be more efficient. The GEOTABS system is inherently hybrid when aiming at its application in a wide range of buildings, including those with highly variable loads. Challenges however need to be tackled. A first challenge is the lack of design guidelines on the sizing of the hybrid GEOTABS system to allow a proper tuning between heating and cooling originating from the GEOTABS and from the complementary system. Today case-by-case dynamic simulations are required in design phase, resulting in excessive engineering costs. Secondly, the resulting oversizing of the heat pump and borefield leads to higher investment costs. Thirdly, for the concept to work at its most efficient point, all components need to be engineered as a package, which is rarely the case since they are developed by different companies, leading to higher investments and lower efficiencies. Fourthly, traditional rule-based-control strategies are not able to harvest the full potential of the system and result in high commissioning costs and higher operational costs. Finally, previous studies have shown potential benefits of the system in terms of thermal comfort, health and productivity, yet those have not been fully validated yet.
The hybridGEOTABS project brought together a transdisciplinary team of SMEâ€™s, large industry and research institutes, experienced in research and application of design and control systems in the building and energy world. Their aim is to take away the bottlenecks to allow a wide implementation of the hybridGEOTABS concept. The overall solution consists of an optimal integration of GEOTABS with secondary systems and a white box approach for model predictive control of this integrated system. The main project objectives are to develop, demonstrate and validate the hybridGEOTABS system. Key objectives:
1. The hybridGEOTABS system will be developed and supported by a new holistic control-integrated design procedure, with the overall efficiency for heating and cooling improved by 25 % as compared to current best practice GEOTABS.
2. Development of a method of choosing the appropriate components for hybridGEOTABS, e.g. bore holes, heat pumps, TABS, control, and secondary supply and emission systems, in order to achieve optimal performance of the integrated system.
3. A suitable control system with the Model-based Predictive Controller (MPC) as the high-level controller and state-of-the-art low-level controllers, will be developed. A (semi-)automated MPC toolchain for the development of this controller will be developed as an open solution.
4. The groundwork for the establishment of a trade body to promote the concept and help to establish the best practices according to the project will be laid down.
5. A detailed business plan

Work performed

The project started with a definition of the hybridGEOTABS system concept and modules. The development of the holistic and control-integrated design procedure is under development. A white-box model predictive control is aimed at and so far the key components of a semi-automated toolchain that allows to set up this MPC have been developed.
Three GEOTABS demonstration buildings have been selected and measurements of the energy flows, system parameters and IEQ parameters as well as occupant surveys are ongoing. Moreover, 4 case-study buildings are modelled and evaluated using Modelica in a virtual test bed.
As an alternative for the use of TABS in building retrofit, the potential of using radiant ceiling panels with integrated Phase Change Materials is being investigated. Also the optimisation and design of other key hybridGEOTABS components is under investigation, e.g. heat pump performance, borefield and TABS design and an energy dashboard to involve and inform users.

Final results

The development of an integrated design approach for hybrid MPC GEOTABS systems covers 2 large blind spots in the relevant research: it will deliver a coherent strategy to provide feedback about the HVAC systems in the feasibility study/pre-design stage of the design process and it will reduce the implementation cost of MPC to competitive levels by eliminating the need for monitoring in the start-up phase and proposing an automated toolchain for MPC algorithm development.
Key results expected by the end of the project include a hybridGEOTABS design strategy, MPC toolchain, three hybridGEOTABS demonstration buildings, PPP validation and a business plan and trade body. They all will contribute to a broad implementation of the hybridGEOTABS concept that will 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 architectsâ€™ freedom to create buildings that make a real differenceâ€¦ where aesthetics and sustainability meet!