Stochastic approach to ground heat exchanger sizing accounting for weather and ground property variability

Sizing ground heat exchangers (GHE) is typically based on building loads and ground properties, with conventional methods relying on a typical meteorological year and fixed ground and borehole parameters. This study explores how uncertainty in four weather variables and four parameters of the GHE affects the estimation of borehole length. Using 11 scenarios with 5000 coupled building and GHE simulations each, it is shown that borehole length uncertainty can reach 40 m for a borehole length averaging a depth of 165 m. When all eight parameters vary simultaneously, the standard deviation in borehole length is 11.4 m, with 11.2 m attributable to weather variables and only 1.9 m to the parameters of the GHE. The most influential variable is the exterior dry bulb temperature, which presents a borehole length standard deviation of 11.1 m. These findings highlight that accounting for weather uncertainty is critical when selecting borehole lengths to reliably meet thermal loads, thereby ensuring more robust GHE designs.

Mots clés

• Monte Carlo
• BES
• GHE
• Optimisation
• Sizing