The shift to renewables is happening faster than anybody imagined. As that transformation continues to accelerate, one obvious question arises – what about energy storage?
One of Engineers Australia‘s recommendations for the government is to supercharge support for households and companies to purchase energy efficient products. This requires well considered policies to more deeply encourage and better inform investment decisions in such technologies.
Greater demand for energy efficient products, and renewable energy production, will continue to create true scale for renewables by strongly complementing existing policies and programs. But what about energy storage? A predominantly renewable grid cannot operate without storage due to stability issues. Storage can help enhance grid stability by coping with intermittent supply, frequency changes, voltage support, supply and demand fluctuations and more.
“The ongoing question for energy regulators and the Federal government is around balancing transmission with dispatchable capacity,” said Engineers Australia Senior Policy Advisor Grant Watt.
“Transmission allows us to move energy around in a flexible, reliable way. If we’ve got good transmission then we’re networked across the country. When the sun’s not shining or the wind’s not blowing in one place, somewhere else can provide that energy.”
However, that must be balanced with dispatchable capacity that comes mainly from pumped hydro for medium to long-term storage, he said.
“When you’re talking medium to long term, pumped hydro is the most obvious solution. There’s no doubt there will be others — we could have concentrated solar. People talk about underground storage of hydrogen. There’s biofuels, gravity and more. But at the moment, the solutions are predominantly around batteries and hydro.”
Can we do this? Can we have affordable 100 per cent renewables and a stable centralised grid? We absolutely can, Watt said. The solutions already exist. But it won’t be easy. It requires a perfect match of policy and technology.
“That’s why I call it a balancing act,” Watt said. “There’s no silver bullet. It’s complex and it’s fast moving. Anyone who tells you it’s all easy, I’m not buying that. We’re going to need a geographically diverse mix of technologies. If we can use existing infrastructure for pumped hydro as a synchronous power source, that’s also an advantage.”
Research from 2017 led by Professor Andrew Blakers from the Australian National University Research School of Engineering, identified 22,000 potential sites across Australia for pumped hydro energy storage. These included derelict mines and other sites that don’t involve damming a river.
Combined, the sites had a potential storage capacity of 67,000 GWh, immensely more than what is required for a zero-emissions grid.
“Australia needs only a tiny fraction of these sites for pumped hydro storage, about 450 GWh of storage, to support a 100 per cent renewable electricity system,” Blakers said.
“We found so many good potential sites that only the best 0.1 per cent will be needed. We can afford to be choosy.”
Success starts with policy
The most challenging issue facing the integration of more renewables into the network is one known as “system strength”, said Steve Wilson MIEAust, a Technical Director in Aurecon’s Energy business.
“System strength is about voltage waveform stability,” Wilson said. “When you have too many renewables that are inverter based and that go into a weak part of a network, it can introduce instability. Their control systems hunt each other. So there are limits to how much solar can go into a renewable energy zone if it’s in a weaker part of the grid.”
Australian Energy Market Operator (AEMO) and the various network service providers have been focusing on the system strength problem. The plan is to tackle the problem from several angles, including from the policy side, Wilson said. Policy offers the confidence to invest, to build infrastructure and to set regulations and guidelines.
A new system strength rule change by the AEMC, in conjunction with AEMO’s biannual Integrated System Plans, will provide a framework.
“That plan underpins development,” Wilson said. “Then the network service providers have an obligation to provide system strength to certain parts of the network. This is where the opportunities for batteries and other technologies come in.”
From a solar perspective, there will be requirements for system strength that the new solar plants must adhere to, he explained.
These requirements will also cover consumption, ensuring each plant is not using more than its fair share.
There will be mechanisms in place for new solar or wind farms to remediate any residual system strength issues locally, which could involve battery technology. Or, they might choose to pay for the network to manage such issues.
“The way batteries come into it is around grid-forming inverters,” he said. “The resulting grid-forming battery systems have the potential to provide system strength and inertia to the network in a way that supports renewables.”
Advanced battery systems
When the Hornsdale Big Battery proved to be a great success, as outlined in a report from Aurecon called Hornsdale Power Reserve Impact Study, batteries finally appeared on the radar of those in the energy space.
“When it was originally put in as 100MW, the initial functionality was to store energy as the wind blew and dispatch that energy when it didn’t. At the same time, the envisaged capability of system security services under a contract with the South Australian Government, including frequency control and support for South Australia’s interconnector with Victoria to help manage the event of its unexpected loss, was being configured, tested and brought online,” said Conan Jones, engineer and Business Development Manager with FIMER Australia.
“That was a milestone, a peg in the ground in terms of proving what battery technology could do, and be scaled up to achieve.
Since then, battery inverters have advanced dramatically, to a stage where they can enable batteries to perform numerous vital functions within a network.
Intelligent programs control and configure, chop and change the power being drawn from batteries to shape it according to what’s required.
“If it’s frequency support, the inverter can increase or decrease the frequency,” Jones said. “If it’s voltage support, it can push more and it can absorb or dispatch what is known as reactive power. There are a whole lot of things the technology can do.”
The three key functions grid-forming inverters can achieve, ones that grid-following inverters cannot, are inertia, system restart and system strength.
“System restart is a black start, required in the rare and unfortunate event that a region goes black, as happened in South Australia in 2016,” Wilson said.
“In that case you need resources on the network that can actually restart by themselves, to re-energise other parts of the network and get everything restarted.”
Where the original Hornsdale 100MW battery was once considered a giant, that size is now considered average, Jones said. New mega-batteries are now at 300MW.
“Traditional power stations generate in the gigawatts,” Jones said. “But they tend to do that by using multiple units. Coal-fired power stations are built using 300MW or 600MW units to add up to perhaps 1.2GW of total capacity. Battery storage is getting to the fringes of that unit size.”
It’s happening faster than anyone expected
With various global challenges such as COVID, Russia and Ukraine, supply chain issues and more, the price of the fuel that we buy to enable the running of our car engines fluctuates wildly, says Professor Alistair Sproul, Head of School of the School of Photovoltaic and Renewable Energy Engineering at UNSW Sydney.
These challenges are helping to drive the previously unimagined pace of the transition to renewables in Australia.
“The renewable energy transition is happening very quickly, probably more quickly than most people anticipated,” Sproul says.
Building more gas plants shouldn’t be an option, especially without a capacity to add carbon capture and storage technologies to manage their emissions.
“With oil and gas under pressure and such fluctuations in the price of fossil fuels, do we want to deal with potential global catastrophe? Or do we want variable wind and solar and some storage?”
“We simply mustn’t build more gas plants unless it’s absolutely necessary. With oil and gas under pressure and such fluctuations in the price of fossil fuels, do we want to deal with potential global catastrophe? Or do we want variable wind and solar and some storage?”
“The short answer is pumped hydro and batteries. We used to think gas turbines on standby should be fired up quickly to stabilise the grid, pumping more power in. But by the time those old units switch on, as we have seen with the Hornsdale system, batteries have already dealt with any issues.”
Data from Australia’s past energy performance and consumption levels show transformative changes in energy production and usage are very much connected to policy changes.
“The long term trend is clear,” Sproul says. “Coal and gas are declining, solar and wind are growing at about 30 per cent per annum and energy efficiency has kept demand pretty constant – unprecedented before 2008. The transition to 100 per cent renewable energy is happening apace.”
The right mix of technology and policy, therefore, will be the essential ingredients in the recipe for energy market success. Technology is already driving the transition. The right policy will make that transition smoother.