Public defence in Civil Engineering, MSc Jevgeni Fadejev

Title of the thesis: Geothermal energy piles design, sizing and modelling

Thesis defender: Jevgeni Fadejev
Opponents: Prof. Alireza Afshari, Aalborg University, Denmark, and prof. Enrico Fabrizio, Politecnico di Torino, Italy
Custos: Prof. Heidi Salonen, Aalto University School of Engineering

Geothermal energy piles (GEPs) offer significant potential for renewable energy use in nearly zero-energy buildings (NZEBs). However, their modeling remains challenging due to the limited availability of validated methods. In buildings with pile foundations, U-pipes can be pre-installed during casting to activate a heat-exchange function. Once equipped, the piles function as ground heat exchangers that can be coupled with a ground-source heat pump (GSHP) for heating and cooling.

The building foundation layout dictates the placement of geothermal energy piles, leading to thermal interactions between adjacent piles and complicating system sizing without validated modeling tools. This work focused on developing and validating a reliable GEP modeling method. The approach involved performing measurements, simulating pile behavior under various conditions through a parametric study, and comparing results with measured data. IDA ICE and COMSOL were used for modeling and validation.

The validated method was applied to the design of an NZEB commercial hall in Finland. Following construction, one year of operational data was used for model calibration, conclusively demonstrating the method’s accuracy. Calibration revealed unexpected plant behavior due to improper control algorithms, highlighting the importance of monitoring and logging systems in buildings with unconventional plant designs to ensure proper operation and long-term efficiency.

Parametric study results showed that seasonal thermal storage can significantly improve energy efficiency and reduce the required pile length by over 50% in specific cases. As an outcome of this work, a tabulated GEP sizing guide was developed to support early-stage design, enabling engineers to estimate system configurations effectively without relying on complex simulation tools. The method presented here is adaptable to any climate region and building type.

Keywords: Activated pile foundations; Seasonal Thermal Storage; GSHP; GEP sizing guide

Thesis available for public display 7 days prior to the defence at Aaltodoc. 

Contact information: jevgeni.fadejev@taltech.ee