Rooftop PV is pushing down air-conditioning costs at a Queensland campus that runs a water tank like a giant battery.

Universities are brilliant testing grounds for clean energy technology simply because they are filled with brilliant people – but the students at the University of the Sunshine Coast, in Queensland, have some emissions-cutting technology the other tertiary institutions around Australia haven’t got: a water battery.

The project reduces the carbon footprint of the main campus by 42% by integrating 2.1MW of rooftop solar with a 4.5ML chilled water storage tank used for the air-conditioning process. An energy management system monitors the onsite PV system and decides whether to use it to chill water, reduce building energy use or export to the grid.

In a hot part of Australia, that makes a solar-powered chilled water tank effectively act as a thermal battery. If the sun’s behind a cloud, the thermal battery is charged in off peak and during the cooler night time.

The university has a carbon management plan with a target to achieve carbon neutrality by 2025, which isn’t far away. To ease the process USC partnered with Veolia on a project that would test an innovative concept and offer an opportunity for learning and research integration.

Air-conditioning accounted for more than half the load at the campus but following the upgrade of the cooling network the system is 37% more efficient.

The project took the Out of the Box prize at the 2019 Global District Energy Climate Awards in Iceland, which is supported by the United Nations Environment Programme.

Veolia will own, operate and maintain the infrastructure for 10 years, when ownership will transfer to USC. Under the agreement Veolia, which already operated the university energy facilities, sells electricity and chilled water to USC at an agreed price for 10 years.

If renewable energy sources are used to power cooling of the campus, emissions will fall by about 37%. Energy costs are expected to fall by $7.3 million over the first 10 years and $111 million over the 25-year design life of the project.

Living laboratory

This project provides a living laboratory on-campus, USC says, enabling students to gain first-hand knowledge and experience of sustainability, innovation and energy efficiency as part of their studies.

“USC recognises that our sustainability legacy will be realised primarily through the impact of our teaching and research, including the contribution of graduates as active, informed citizens and leaders who are knowledgeable about sustainability and its practices,” says USC vice-chancellor and president Professor Greg Hill.

The 8.2MW cooling network has a peak flow rate of 140L/s in summer, with 1.6km of piping serving 15 buildings. About 2.1MW of solar PV is spread across rooftop and car-park structures.

By 2050, energy use for cooling is projected to triple and global energy demand for cooling will be more than it is for heating. As part of its carbon management plan, the university aimed to achieve maximum in-house energy abatement on campus (rather than purchasing carbon off-sets). This meant focusing on both energy efficiency measures and the implementation of renewable energy-based solutions.

The upgrade reduces consumption of electricity from the grid for the university’s main campus by 42%. The owners also expect it will cut CO2 emissions by 100,634 tonnes and main water consumption by 802 million litres over the 25-year project life. Forty EV charging bays are also planned for the car park.

“The university practices what it preaches,” says USC deputy head, school of science and engineering Dr Graham Ashford. “In making these changes that we’ve been advocating in the wider world, it is proof that we are leading the way in sustainability initiatives.”