The electricity grid is evolving as coal plants reach the end of their lives and the popularity of renewables grows. create spoke to power engineering specialists about the challenges ahead.
The coming months are likely to be hotter than average, and power engineering specialist Kate Summers is concerned about the safety and security of the grid – particularly in the eastern states.
“We face another summer with the eastern seaboard at risk again with inadequate control of active power,” she said.
Summers is an Engineers Australia Fellow and member of the Energy Advisory Panel, which supports the organisation’s public advocacy goals. She told create that the greatest threat to disruption of essential electricity services is not the rising share of renewable energy, but the way existing coal- and gas-fired power plants are controlled under the current market-driven system.
“Meeting the demands of the market has failed to protect the power system,” she explained, adding that the market was never intended to interfere with the control of the power system, but evidence shows it has.
“We can observe that the market rules have significantly altered the dynamic control of the system,” she said.
Renewables on the rise
According to the Department of Environment and Energy’s September update, coal plants provided 60 per cent of Australia’s electrical energy in 2018, down from over 80 per cent in 2000.
Renewables made up 19 per cent of generation last year, and rose faster than any nation in the world on a per capita basis. There is also more electricity being fed into the grid by households and industry – accounting for 13 per cent of generation in 2017-18.
At the end of August, Australia met its large-scale Renewable Energy Target (RET) of 33,000 additional GWh of renewable generation by 2020. Although investment slowed this year, an ANU study found that generation capacity has continued to rise due to the reduced cost of building renewable energy plants.
Summers pointed out that meeting the RET was a moot point, as wind generation, which made up 6 per cent of total generation last year, only runs at its rated capacity 10 per cent of the time. Depending on the location, she said it typically generates between a third to half of its installed capacity.
Challenges for the grid
The National Electricity Market connects Victoria, NSW, South Australia, the ACT, Queensland and Tasmania. According to Summers, it is a unique system that requires local experts to ensure that each region runs efficiently and effectively.
“People can make rules from an operational perspective, but if they don’t necessarily understand the system dynamics, there can be unintended consequences,” she said.
One essential principle for safe and secure operation is maintaining a stable grid frequency of 50 Hz. This has proved challenging, as the output of existing coal- and gas-fired turbines is not adjusted locally, but controlled according to the centralised dispatch system, which approximates demand.
“If you don’t know what the frequency is, you can’t predict what will happen with a large event,” Summers explained, adding that the central system updates every five minutes, while actual frequency changes each millisecond.
This has been a known technical issue since 2017, and the cost of services to rectify frequency variations have been passed on to consumers. The Australian Energy Market Operator and others have proposed rule changes to the Australian Energy Market Commission to address the problem, but these will take several months to go through the consultation process. A final decision is due in the first quarter of 2020.
While the grid will need to adapt to more distributed renewable power generation, Summers said that a lot of money is being spent on complex, ineffective solutions, which is also driving up power bills.
Engineering expertise essential for safety and security
Summers emphasised that the electrical power grid was an essential and complex piece of infrastructure, and should be subject to power system engineering scrutiny, as would be expected with infrastructure in any other field.
“If a civil engineer is building a wall, they need to make sure that the foundations and footings won’t let it fall over,” she said.
According to her, the foundations of a safe and secure power system were stable frequency and voltage, but there had been a loss of power control systems knowledge among the people making decisions about the future of the grid.
Summers added that this has implications for safety and security, as the complexity of the current market rules is making it harder for electrical engineers to do their jobs and ensure that protections are in place for workers and equipment.
Other issues are the loss of local knowledge, and that decisions about the grid tend to be skewed towards cost.
The Chair of the Engineers Australia Electrical College, Dr Peter Sokolowski, agreed that safety should outweigh all other considerations.
“People should not profit from safety and security – safety should be paramount,” he said.
Solar and wind have 2 insurmountable problems – they can, over wide areas go between full output and almost zero in seconds and, longer term, can go for days and possibly weeks at low output, necessitating investment in backup generation which is far less than fully utilised making it not cost-effective and, if the backup is gas, then making it uneconomic to invest in the much more efficient combined cycle. The only thing which works effectively with large amounts of solar and wind is hydro with very large (months at least) storage. Pumped storage can work for 24 hour variations and maybe even day to day, but not on a longer time frame. High proportions of solar and wind doom a network to a major and sustained load restriction at some time in its future.