Joint use of quasi-3D response model and spectral method to simulate borehole heat exchanger

• An efficient approach to model borehole heat exchangers is presented.
• The method uses a response model and convolution in the spectral domain.
• Synthetic, laboratory and field measurements are used to validate the approach.
• The method provides, in a few seconds, accurate and reliable solution.

A quasi-3D model is used as a response model to generate normalized transfer functions of a borehole heat exchanger model. A solution is achieved by convolving in the spectral domain the transfer function of a given node with an input function describing the temperature change of the fluid over time. To demonstrate the accuracy and validity of the method, three comparison scenarios are studied. These scenarios compare the temperatures of a reference numerical model, the temperatures measured in the scope of a laboratory experiment, and during a field thermal response test. It is shown that the combined use of a spectral method and response model provides, in a few seconds, a temperature solution whose error is below or comparable to the measurement's uncertainty.