As the global temperature increases, world cities grow, and populations boom, there is an intense desire and need for our buildings to be climate controlled. Most new building developments have a climate control feature by default, and this has intensified research into renewable and sustainable ways of generating energy.
“The global impact of air conditioning is significant, and only going to rise,” says Associate Professor Hossam Abuel-Naga of La Trobe University’s Department of Engineering. “In China in particular the heating and cooling of buildings is a big industry, and sales of air conditioners have almost doubled over the last five years.”
Collaborating with Professor Han-Long Liu of Chongqing University in China, Dr Abuel-Naga has been exploring methods of heating and cooling buildings by exchanging heat with the ground through deep building foundations (piles).
“These new piles could be called ‘energy piles’ and can be described as dual-purpose structure elements,” says Dr Abuel-Naga. “Buildings require a ground-concrete element as structural support, and this can also be used as a heat exchange unit.”
At 5 metres depth below the ground surface level the temperatures are relatively stable regardless of the ambient air temperature, and the energy piles can effectively serve as a heat sink for the heat pump (HP) system.
“In the heating mode, the HP extracts heat from the ground through energy piles and pumps it via a refrigeration cycle into the building,” says Dr Abuel Naga. “In the cooling mode, the reverse occurs, with heat extracted from the interior of the building and rejected into the earth through the energy piles. The design of energy pile differs from the conventional pile as it is subjected to mechanical and cyclic thermal loads, so more research is needed in this field.”
Several full-scale field tests of energy piles have now been installed by Professor Liu’s research group in China, and the results of these tests can further develop and refine the engineering behaviour of the energy piles and heat exchange process. So far the successful collaboration has resulted in two published journal papers, and Dr Abuel-Naga has been named an Adjunct Professor of Chongqing University.
Dr Abuel-Naga and Professor Liu have also been granted a patent for a method for injecting a bacteria into the soil which causes a calcite precipitation and provides a strengthened foundation for building.
They hope that their success will contribute to energy solutions in Australia and China as well as encourage future collaborations between both institutions.