South Australia transmission company ElectraNet says it has found a cheaper solution that using the state’s gas plants to provide system strength to the local grid, which is now dominated by wind and solar.
ElectraNet says it proposes to install three “synchronous condensers” in key areas of the state – at a cost of around $80 million – to ensure that gas-fired generators will no longer need to be switched on just to ensure the grid remains stable.
The proposal is yet another sign of the rapid change in South Australia’s grid, which is now beyond 50 per cent of wind and solar in local generation, and is also leading the way in the adoption of battery storage.
It is probably just as well, because the state’s biggest gas units at Pelican Point – also dubbed the state’s most modern and efficient fossil fuel plant – have been out of action for more than a month due to unspecified faults.
This has meant that the Australian Energy Market Operator has had to call on older and more expensive generators to satisfy its new equations for guaranteeing “system strength”.
This in turn has resulted in higher prices over the last month, and has coincided with a near doubling in AEMO directions to the market – to an extraordinary 73 per cent of trading intervals in the last four weeks.
The equations for system strength, which now number more than 20 different combinations of gas and diesel generators, were introduced last July as part of the AEMO response to the previous blackouts and load-shedding.
Some in the market think AEMO is being highly conservative on system strength – which seeks to stabilize voltage levels (inertia is generally required to maintain frequency).
As ElectraNet and AEMO have pointed out, South Australia has the highest penetration of wind, compared to the size of its grid, than anywhere else in the world, and wind can provide more than 120 per cent of demand at certain times.
But according to ElectraNet, those directions or interventions may not be necessary in the future if its proposed use of synchronous condensers is approved.
At the instigation of AEMO, EectraNet conducted a tender of gas generators for the provision of system strength, but the offers were too expensive.
ElectraNet found that by placing three condensers at strategic parts of the grid, then
This is significant.
The Tesla big battery near the Hornsdale wind farm has already changed the way operators and owners are thinking about the management of the grid, now that they have at hand technology which is faster and more accurate than conventional plant, and is slashing prices.
Now, ElectaNet has found that using synchronous generators is cheaper than contracting with existing generators which currently also provide inertia and system strength essentially for free.
“It suggests that the cost of providing these services is quite manageable, and cheaper compared to the current practice of issuing directions to gas generators in South Australia,” says Dylan McConnell, from the Climate and Energy College in Melbourne.
The use of synchronous condensers and its ability to reduce the need to rely on conventional generation is an important consideration as South Australia heads towards a market share of 75 per cent wind and solar by 2025.
Even though the new Liberal state government does not share the previous Labor government’s target of 75 per cent renewables by 2025, the target is likely to be met before that anyway, given the current construction and the intentions of Whyalla steel owner Sanjeev Gupta to power that facility with up to 1GW of solar and storage.
“South Australia has become a world leader in renewable energy generation,” an ElectraNet document says on its website.
Its tender and subsequent analysis concluded that contracts with gas generators would not be economic based on generator costs, and installing synchronous condensers on the network is the least cost solution.
“No other realistic options are available to meet the need in the required timeframe.
Installing network synchronous condensers is a no regrets measure to meet an immediate need. Any future sources of system strength available will help address wider constraints on the power system.
ElectraNet says installing synchronous condensers will avoid the need for costly generator direction by AEMO, and this is expected to result in a net cost saving equivalent to $3 to $5 per year on a typical South Australian residential electricity bill.
“Directing generators is an interim operational solution only, and is unlikely to remain a viable option,” it notes.
An ElectraNet spokesperson said in an emailed statement that the final costs will be known once detailed specification and design work is finalised in coming months, but around $80 million had been allowed.
“The savings are the expected net impact of the cost to implement the solution and it is expected that this solution will largely eliminate the need for special system strength directions by AEMO. “
A synchronous condenser operates in a similar way to large electric motors and generators.
It contains a synchronous motor whose shaft is not directly connected to anything, but spins freely and is able to adjust technical conditions on the power system.
Electranet says the synchronous condensers are expected to be operational within 18-24 months.
It says detailed technical analysis is being undertaken in consultation with AEMO and manufacturers to determine the number, size, specification and design of the synchronous condensers required to meet the system strength gap.