Farmers often pride themselves on their self-reliance. When you live far from the cities, it makes sense to do as much as possible yourself. Australia’s sheer size has meant many remote farms have long been off grid as it’s often simply too expensive to get a power connection. But for those still on the grid, there are now new options.
As solar gets cheaper, more and more farms are aiming to become self-reliant in power. But until now, getting fully off the grid has had a sticking point – solar intermittency. Solar power might be cheaper than ever, but if you don’t have storage or backup, you’re still reliant on the grid when the sun doesn’t shine.
Batteries are a compelling solution. But they might not offer a full day’s backup and come with concerns about fire risk and waste.
Generators offer reliable backup. But they too have downsides – they have to be resupplied and produce harmful emissions.
For farmers, there’s now another option: connect one of your dams to a river – or link two dams together – to create a small pumped hydro plant to store electricity from solar to use at night. The water in your dams could offer yet another form of self-reliance.
Our new research has identified over 30,000 rural sites where micro pumped hydro could work. A typical site could produce two kilowatts of power and store 30 kilowatt hours of energy – enough to run a typical home in South Australia for 40 hours.
Massive to micro? Yes, pumped hydro can work on farms
Pumped hydro is essentially turning hydroelectric power into a battery as well.
Take two reservoirs, where one is higher than the other. When you have extra solar power, you store it. How? By using the energy to pump water uphill to the top reservoir. When you need power later on, you release water down to the lower reservoir and produce electricity with a turbine.
At large scale, these plants are an established and efficient way to store energy, though they can suffer from cost blowouts, as in the Snowy 2.0 scheme. Queensland’s government is planning massive pumped hydro schemes to act as batteries.
Until recently, small-scale pumped hydro hasn’t made much economic sense.
But the steadily falling cost of solar means the numbers have changed. It’s now more cost effective to get larger arrays. And that opens up opportunities to find ways to store surplus electricity generated in daytime.
For farmers, another opportunity is the ability to use existing dams and reduce pumped hydro construction costs.
If it’s cheaper, it’s much more viable. Early research on solar-powered irrigation systems using pumped hydro suggests the payback period for this kind of energy storage could be up to four times shorter than for batteries.
What’s the catch? As you might have guessed, this solution depends on the size of existing farm dams and rivers, and topography of the land.
The steeper the slope between the two water bodies, the more useful the system will be as energy storage. To get the most out of these systems means finding the sites with the most potential value. And it’s likely the solution won’t work for farms on flat ground – you need a drop of at least 20 metres.
You’re probably wondering how this stacks up financially. We compared a micro pumped hydro system with 42.6kWh capacity and able to discharge 3.6kW to a commercial lithium-ion battery, the Tesla Powerwall, able to store 13.5kWh and discharge 5.0kW.
We found micro pumped hydro storage was 30% cheaper than a battery if locally generated solar was regularly needed overnight – such as to power a 24/7 irrigation system.