Why scientists want to float solar panels on our farmers’ dams

A new $13m research project could offer farmers a win-win solution to the problem of water loss through evaporation, while at the same time generating renewable energy.

A Japanese worker checking solar panels at a floating solar farm. Picture: AFP

Solar panels are a familiar – and often controversial – sight in the Australian bush, as farmers question the loss of land in the name of renewable energy. Now a group of scientists and economists are offering a win-win for farmers in a $13m project using solar panels to capture – and simultaneously block – the sun.

The landmark research will see floating solar panels installed on farm dams in Queensland to reduce evaporation, in a country where about 40 per cent of stored water is lost to evaporation.

At the same time, the panels will generate massive amounts of renewable power.

Floating solar panels are already used to generate power in countries such as Spain, South Korea, Japan and Singapore, in high population areas where land is limited.

Now Australian irrigators, who have tried for years to minimise evaporation by covering the surface of farm dams, could have a solution, one that mitigates water loss while producing renewable energy.

Jon Welsh, a partner in Ag Econ Australia, the research consultancy leading the project with the Cotton Research and Development Corporation, says cotton farmers have tried everything to limit evaporation.

From left: Ag Econ principal climate analyst and economist Jon Welsh, CRDC executive Allan Williams and Michael Scob.

“They’ve used plastic balls dumped off the back of a semi-trailer to float on the top of the dam,” Mr Welsh said. “They’ve tried polymers, they’ve tried plastic coating. They’ve tried everything, because you lose a lot of water in the course of the summer season. In some areas it’s uneconomical to store water on a farm.”

His company, based at Burren Junction in northern NSW, and the CRDC are part of a consortium, including the University of Southern Queensland and Macquarie University, which will use a recent $6m federal government grant to investigate the use of solar panels. A key element of the project is working out what to do with the by-product – a large amount of renewable energy- at a time when there’s already so much solar power in the system.

The aim is to find the “sweet spot” for farmers – minimising the number of panels needed for maximum impact on evaporation without generating massive amounts of power that energy companies don’t want.

“The evaporative loss isn’t a one-to-one ratio of the dam cover because even installing panels in one section of a dam interrupts the evaporative fluid dynamics and has a bigger impact,” Mr Welsh said. “The researchers at USQ will try different row, mooring and tilt configurations to measure how few solar panels are needed, because one of the challenges is, what on earth do we do with all these kilowatt hours and all these electrons so far away from population centres?”

Ag Econ’s role is see whether “we can get the economics to stack up by using energy elsewhere in the agricultural supply chain, or local schools or hospitals in irrigation areas”.

The good news is that while it’s almost impossible for a remote farm to sell its renewable energy into a nearby solar farm or retailer, for example, there are markets further afield thanks to the development of virtual net metering and virtual power plants that combine batteries with solar. These developments allow a renewable energy producer to deliver energy as an “offset” to a user hundreds of kilometres away.

For several years, USQ has led research on the use of the panels to counter evaporation but the project will move to another level with the $6m federal grant and in-kind investment totalling another $7m from another 18 consortium members, including irrigation groups, agriculture research agencies, and farmers.

Floating solar panels on an Australian farm.

“Ag Econ has access to other useful desktop modelling but the grant allows us have demonstration equipment in the harsh Australian climate, which is very expensive, and do some actual readings and look at actual configurations,” Mr Welsh said. “We also need to see what happens when the dams go dry in a severe drought, and the solar panels then sit on land, for example. Instead of using proxy data from overseas sources, we’re going to be able to actually do it and generate Australian data in an irrigation setting.”

The experimental work will be done at a the Tosari Crop Research Centre on the Darling Downs and at other sites at USQ in Toowoomba. The research will look at a number of agricultural industries in key locations in eastern Australia beyond cotton, including grains, sugarcane, pecans and rice.

Mr Welsh says it is difficult at this stage to estimate how much water could be saved, but one calculation is that if about half of the land-based solar farms were relocated to dams and water storage areas, we could save water equivalent to 60 per cent of the volume of Sydney Harbour, or about 118,000 Olympic swimming pools annually. That’s about the size of the giant Glenlyon Dam in Queensland near the NSW border, which holds about 253,000 megalitres of water.

While the Australian cotton industry has improved its water use efficiency by almost 50 per cent since 1997, the most significant loss of on-farm water is the evaporation from on-farm storages, according to the CRDC.

Senior innovation broker Susan Maas said: “The Australian cotton industry has made huge gains in water-use efficiency over the past 30 years, driven by research, development and extension. Mitigating evaporation losses is a huge unrealised opportunity for the industry and the environment.”