A panel discussion hosted by renewables business mentoring program EnergyLab looked at ways clean energy technologies could help to control voltage instability, frequency volatility and inertia in the grid.
Panel participants (from left)
Chris McLean, general manager, Energetics
Dani Alexander, research principal, Institute of Sustainable Futures, UTS
Leesa Blazley, co-founder and director, Solafast
Iain MacGill, associate professor, UNSW
Chaired by James Tilbury, acceleration program and operations, EnergyLab
Can clean energy technologies provide the grid with all the services it needs? It’s a good question, especially when you consider that renewables are often targeted by detractors as the cause of many problems with frequency control and voltage stability. If clean energy technology can solve some of these problems, the transition to greater reliance on solar and wind generation should happen at a faster pace.
Well, that’s what you’d hope to happen. But could it be?
EnergyLab hosted a discussion where experts from the industry were asked which services should be priorities for the grid and where they predicted solutions should come from.
Chris McLean of Energetics picked on voltage regulation, for a start. “In terms of renewables it’s the ability to have almost instantaneous demand response,” he said. “We don’t have great incentives to do that at the moment, but … better communication networks and better IT systems will allow us to have demand response signalling, market signalling and almost instantaneous demand response.” When data is released into the grid, the variability of renewables and associated voltage fluctuations will become an optimisation problem for a distributed network of smart energy management systems. Where there’s a solvable problem, there’s a solution.
The integration of decentralised generation into the grid is a major field of study at the Institute of Sustainable Futures, said research principal Dani Alexander. In an expanding distributed generation scenario, “which the traditional grid was not built for,” she said, the key to success is in allowing voltage and frequency regulation services to be provided by new technology “that exists and will exist into the future”.
Leesa Blazley recalled recent work in her former role at AEMO which looked at auxiliary services with a focus of integrating renewables into the network. “Particularly we need to think more about diversity of technology in the systems and really broaden our minds as to what else can contribute to auxiliary services,” she said, suggesting demand management, deferent types of generators that might reduce inertia and fast frequency response. “We’re looking at diversity of technology and diversity in location as well.”
Services is in our national electricity objective, said Iain MacGill of UNSW, “and it’s always worth keeping in mind the grid’s job is to serve us, not us to serve the grid. That then raises the issue: who needs those grid services?” The fact it is consumers who rely on grid services has important implications about who should pay for delivery, he said.
As solar PV has become more ubiquitous on suburban rooftops networks have noticed hotspots of voltage irregularity as systems export energy into the grid. Can this problem be ironed out before regulators see it as an excuse to limit solar expansion?
Alexander’s colleagues at ISF has been researching the problem, looking at how inverters along branches of networks with plenty of installed solar can be orchestrated to minimise ups and downs in voltage (where it often drops approaching the end of a line). “Keeping voltage within stable limits is very important for the grid,” she said. “If it’s too high, it may damage electronic equipment; if it’s too low, the lights may dim.”
ISF’s research seeks solutions to voltage irregularity through calibration of residential solar systems that have storage and energy management systems. “Traditionally these voltages have been regulated through other pieces of equipment, with the cost passed on to the consumer,” she said. As voltage issues rise, there are two options: limit the amount of solar installed, or; the network could invest in additional components and pass the cost to consumers.
ISF is working with networks in Victoria and NSW to find a way they can access solar households’ data and co-ordinate their energy exports to minimise voltage irregularities while rewarding the customer and the networks. One of the hurdles she describes is deciding what is the true value of a voltage regulation service from each site. “We’re still at an early stage,” she said. “These services are there to be had; the trick is in monetising these services.”
Solar ‘cares about voltage’
Things have changed since the old days, says MacGill from UNSW, when the networks paid little attention to voltage. “It used to be, OK, if people’s lightbulbs burn out too quickly the voltage is too high; if the fridge won’t start the voltage is too low,” he said, poking a bit of fun at the past. But solar has changed all that by showing itself as a technology that “looks at voltage and cares about voltage”.
The benefit to installing solar and batteries is lower energy bills, said McLean of Energetics, “but there really isn’t a financial incentive to install the command control system you need to [reduce network voltage irregularity] at a large scale.”
It’s easy enough for a single household with solar and batteries to load-shift or perform instant demand response, but for a network of such households to relinquish some control of their systems to a central command mechanism is going a bit far – unless there is a reward. “You need a financial reason for them to want to do that.”
At the moment, he said, there is no financial incentive for the gentailers to enter this market “unless they are forced to”.
The balance of electricity supply and demand is what makes the world go around. What is glibly referred to as “frequency response” is largely set by large synchronous generators spinning between 1,500 and 3,000rpm and effectively setting frequency on the grid, MacGill said. “If the amount of power being pushed in from generation is exactly the same as that being taken out by loads, plus losses, frequency is stable.” Frequency changes, or course, when there is an imbalance between supply and demand. If it’s a case of a fall in load, the power has to go somewhere – and that when the rotating machines (and frequency) start to speed up, MacGill said.
“Electricity industry operation is this complex, delicate and continuous task of basically trying as much as possible to balance energy being pushed in and energy being taken out,” he said. “If you are not doing that successfully then frequency starts to move.”
It can happen very quickly, and the rate of change of frequency, or RoCoF, is a major concern for generators and network operators because of the inertia in a system made up of heavy objects spinning at enormous speed. “The harder the frequency tries to change, the more the inertia tries to fight back.”
How can renewables help? With dispatch times measured in seconds, yes, they can, but part of the challenge is what to do about the very, very fast frequency control when deviations first start to take off. “That is the question,” he said.
Alexander at IFS won’t commit to predicting an end to the problems of frequency response and inertia – which can never be overcome completely – but batteries, she said, will be a part of the solution to containing them. The amount of storage required to satisfy “system adequacy” is relatively low until the day renewables make up about 40-50% of supply, she said. But storage can be relied on as a tool to settle frequency at unexpected times where there are big fluctuations which really throw out the frequency, such as storms. “That’s where we talk about inertia, and the need really comes from in a high renewables future,” she said. “That’s the biggest need we identify.”
Faster and faster
If dispatch can be shortened to hundreds of milliseconds, “you need less inertia,” MacGill at UNSW said. He sees hope in solar-and-storage systems he’s visited where there is no synchronous spinning generation. Sure, a 1MW solar system with 6MWh of storage in Western Samoa is much smaller than the NEM, but it works without any synchronous generation, as do the 10,000 off-the-grid households around Australia.
“In a very strange way it sort of suggests the problem’s not 100% renewables, it’s transition,” he said. “How is the existing stuff going to behave as we push renewables up?”
The answer will be revealed. In time.