A world-first trial at the Metro Tunnel’s State Library Station site demonstrated how renewable energy can be captured inside a building’s foundations – with potential emissions savings equivalent to taking hundreds of cars off the road each year.

The trial involved burying plastic pipes inside concrete foundation piles, installed 40m underground in a retaining wall during the early months of station construction.

With the ground temperature remaining stable throughout the year, the geothermal system works by heating or cooling water pumped through the pipes, depending on the time of year.

Graphic showing how ground heat is exchanged in a geothermal process.

In summer, warm water pumped into the ground releases heat and then returns to the surface cooler, to cool the building above ground. In winter, cold water pumped through the pipes absorbs heat from the ground and returns to the surface warmer, to heat the building.

The trial found a train station such as State Library could use this efficient and cost-effective system for all its heating and cooling needs – and even help heat and cool surrounding buildings.

The 4-year trial was led by the University of Melbourne in partnership with Metro Tunnel Project, CYP Design & Construction and John Holland.

The project was a finalist in the 2022 Premier’s Sustainability Awards, recognising its potential to dramatically change the way we heat and cool buildings in Australia with a simple and cost-effective clean energy solution.