Thermal response of energy foundations installed in unsaturated residual soils

Michael B. Reiter, Thaise Da S.O. Morais, Cristina De H.C. Tsuha, Tugce Baser

Research output: Contribution to journalConference articlepeer-review


This study focuses on the thermal response of energy foundations with different piping geometries installed in unsaturated soil. Energy foundations are an efficient alternative to traditional space heating and cooling approaches and can reduce energy demand for air conditioning in Brazil, where unsaturated residual soil deposits are abundant. A three-dimensional numerical model for heat transfer and subsurface flow is first validated against field data from a thermal response test at the University of São Paulo. The model is then used to compare the performance of triple and quadruple U-tube piping geometries and helical piping geometries of equivalent length. The helical geometries resulted in initial less uniformly heated foundations and lower heat flux at the foundation boundary compared with the U-tubes, but the differences between the U-tube geometries and their equivalent length helices were less than 1°C. All piping geometries exhibited increased heat output as the length of heat exchanger piping increased. The infinite line source solution was compared with the model results. The infinite line source solution underestimated the thermal response of the system during the first 25-30 days and overestimated it afterwards.

Original languageEnglish (US)
Article number05021
JournalE3S Web of Conferences
StatePublished - Nov 18 2020
Externally publishedYes
Event2nd International Conference on Energy Geotechnics, ICEGT 2020 - La Jolla, United States
Duration: Sep 20 2020Sep 23 2020

ASJC Scopus subject areas

  • General Environmental Science
  • General Energy
  • General Earth and Planetary Sciences


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