Metro tunnel trial shows sustainable future of heating and cooling

A first-of-its-kind trial in Melbourne’s Metro Tunnel station has demonstrated the efficiency of capturing geothermal energy in the foundations of buildings for heating and cooling buildings.

Over the four-year project, a team of researchers installed plastic pipes within concrete foundation piles 40 metres underground, along with geothermal heat pumps and associated technology, and then monitored the effectiveness of the geothermal system.

The project was led by a team from the University of Melbourne’s Faculty of Engineering and IT, in partnership with Rail Projects Victoria and its construction contractors John Holland and Cross Yarra Partnership D&C.

The trial showed that geothermal energy could meet all the heating and cooling needs of a train station such as State Library and even help warm and cool surrounding buildings. It could also potentially save thousands of kilograms in carbon emissions every year.

Using sensors, the researchers tested scenarios, such as varying the number of pipes, to find the most energy-efficient use of the system. Water pumped through the pipes absorbs heat from the ground in winter, and releases heat into the ground in summer. When it returns to the surface via a ground source heat pump, the change in temperature can be used to efficiently heat or cool the building.

The trial was heavily instrumented, making it one of the most comprehensively monitored energy geo-structures in the world. This instrumentation is not required for normal commercial roll-out, but was invaluable for testing and refinement of design techniques.

The State Library Station geothermal trial has the potential to be a “practice run” for installing this type of system in major projects in the future, both in Australia and overseas.

The project is a finalist in the 2022 Premier’s Sustainability Awards.