Behavioral modeling of the thermal dynamics of borefields for geothermal applications

Research output: Chapter in Book/Report/Conference proceedingMeeting abstract (Book)

Abstract

This work is related to geothermal heat pumps. This central heating and/or cooling system pumps heat from or to the ground. It is one of the most recommendable methods for heating buildings via so called green energy. Current controllers don't explicitly take the dynamic behavior of the source-side into account. The object of this work is to model the thermal dynamic behavior of the surrounding geology. This model can then be used to develop an optimal control strategy that also prevents the exhaustion of the heat from the soil on short and long term. It is important that the slow dynamic behavior of the soil is well modeled. The system dynamics of a ground coupled heat pump is characterized by very diverse time constants. The conductive heat transport between the soil and the fluid is characterized by small time constants (with an order of magnitude of several minutes). On the other hand, the thermal diffusion in the soil is characterized by large time constants (with an order of magnitude of years). An additional problem is that diffusion phenomena can only be approximately described by a rational form in the s-domain (with s the Laplace variable). In order to get more accurate results rational models in the s-domain have to be used. There are more challenges to be faced. Only a limited amount of measured quantities are easily accessible for the user. The measurement time is limited as well as the possible excitations. Several other identification problems have to be considered, for example, MIMO identification of the thermal diffusion in multiple borefield installations, dealing with missing data, the model will be validated by use of simulations as well as measurements on an operational thermal installation.
Original languageEnglish
Title of host publicationDYSCO study day at KU Leuven-Heverlee, Thermotechnisch Instituut
Publication statusPublished - 27 Nov 2009

Keywords

  • geothermal heat pumps
  • rational models
  • borefield installations

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