Solar-Powered ‘Water Battery’ Slashes University’s Electricity Bills – and Ecological Footprint

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It’s not always easy keeping cool. Air conditioning currently makes up almost 9% of global energy use – and as living standards rise across warmer parts of the world, that’s billed to grow significantly. Global energy demand for air conditioning is predicted to triple by 2050, making it one of the top likely drivers of demand over the coming decades. 

But could the abundant sunshine in warmer places actually help to bring buildings to more comfortable temperatures, without the outsize carbon footprint of conventional air conditioning systems? In Queensland, Australia, the University of the Sunshine Coast (USC)’s flagship Sippy Downs campus – which devotes a whopping 60% of its energy usage to air conditioning – has put in place an effective, low-impact system for harnessing the sun’s rays to keep its buildings cool. 

In 2019, the institution installed and began operating a giant ‘water battery’ on the campus. It works like this: solar energy is captured by over 6,500 solar panels, which are spread across campus rooftops and car park structures. The panels produce enough energy to cool 4.5 megalitres of water – almost two Olympic-sized swimming pools’ worth – in a specially-designed ‘cooling tower’, which effectively acts as an eight-megawatt battery. The cooled water is then used for air conditioning.

USC’s ‘water battery’

“It’s remarkably straightforward,” said Queensland’s chief scientist, Professor Hugh Possingham, upon visiting the campus in December 2019. “One wonders why more universities, more industries, more campuses of all kinds, don’t use this sort of system.”

The water is drawn from an on-campus lake and recycled, providing savings of about 21,264 kilo-litres of water annually. The tank uses environmentally-friendly refrigerant gas. There are considerable maintenance and life-cycle advantages for the water battery over conventional solar batteries: while the latter need replacing every five to fifteen years, are difficult to dispose of in environmentally-sound ways, and can be the size of a shipping container, the cooling tank will likely only need its lining replaced once over the project’s lifespan. 

A low-waste, environmentally-friendly approach was mainstreamed through multiple elements of the project, said USC energy and infrastructure manager Dennis Frost. When a boardwalk was removed to make way for the thermal tank, the timber was recycled and used to make the workbench in the control room; meanwhile, a pond that was created to catch sediment during the building process has been turned into a permanent ongoing feature to attract wildlife onto the site.  

The system reacts in real time to changing conditions, such as weather and occupancy level, by shifting energy between the solar panels, mains electricity and thermal energy storage tank depending on what is most efficient at that moment. The most productive month for the system was December 2019, while February 2020 was the least productive due to large amounts of heavy rain and cloud cover, which reduced the amount of solar energy that could be generated during that time. 

Over the past twelve months, the system has generated 3,426,545 kilowatt hours of electricity; met over 34 percent of the campus’ energy consumption; and fed around two million kilowatt hours of electricity back into Queensland’s energy grid. In doing so, it’s saved 4,232 tonnes of carbon dioxide emissions – equivalent to planting 69,977 tree seedlings and growing them for 10 years. The system is expected to save a hundred thousand tonnes of carbon dioxide emissions over 25 years. 

The project’s success so far represents a major step towards the university’s goal of becoming carbon neutral by 2025, said USC’s vice-chancellor and president, Professor Helen Bartlett. It’s also highlighted the value of regional innovation: “USC is the first university in Australia to install a water battery powered by renewables, which is further proof that you don’t need to be in the big cities to do big things,” she said in a press release on December 16 of 2020. 

The project was developed in partnership with French transnational environmental solutions company Veolia, which shouldered the entire cost of building the system and is now selling the energy it generates back to the university at a rate cheaper than electricity from the grid. After ten years, ownership of the system will be transferred to USC; it’s estimated that the project will lead to around $100 million in electricity cost savings for the institution over the life of the project. 

The public-private partnership that Veolia and USC have developed to put the plan into action is particularly inspiring to witness, said USC senior lecturer Retha de Villiers Scheepers, who specializes in entrepreneurship and innovation management.

“Less than 30% of private businesses innovate together, and now we’re talking about a university as a public institution, and a private institution like Veolia, working together to put in place something like this,” she said. “So it’s pretty amazing what we are getting to experience here.”

Veolia now hopes to help apply the approach elsewhere. “There is a huge amount of excitement that this can be achieved, and that it can be replicable through other universities and other organizations,” said the company’s regional energy services manager, Andrew Darr. 

The system is also being used as a teaching tool for students on campus, particularly those specializing in topics such as business, science, engineering and sustainability. “[W]e are tracking our energy savings in real-time and using that information to teach our engineers, designers and leaders of the future about the enormous and cost-effective possibilities in renewable technologies,” said Bartlett. 

Veolia staff also deliver guest lectures for students, and there are a number of opportunities for them to do paid work on the project. “I think it’s really nice to be studying at a university that really cares about innovation and trying to be at the forefront of these types of projects, because I think it allows us as students to learn more about these things as well and to get that kind of mindset from an early point on,” said engineering student Denise Schiemann. 

Helen Fairweather, USC’s discipline leader in engineering, was also appreciative of the resource-conscious mindset that is being mainstreamed on campus through the presence  of the water battery. “It’s becoming the norm for the engineering students that this is what you do when you do a construction project – you look for ways to bring in renewable technology, renewable energy and construction techniques that are more efficient, use less materials and have a sustainable life,” she said. 

The project won the ‘Out of the Box’ category in the prestigious 2019 Global District Energy Climate Awards, and also recently received the Denis Joseph Award for Innovative Use of Solar Energy in HVAC&R from the Australian Institute of Refrigeration, Air Conditioning and Heating.

Possingham praised the university for its innovation and leadership. “We’re heading into a climate crisis – we could be facing three or four degrees Celsius [of warming], and there’s probably no state in Australia that wants that less than Queensland,” he said. “So everybody is going to need to make a contribution, and the sooner that university campuses can lead the way, show leadership and go carbon neutral, the better.”

Eco-Warriors Around the World