By Phil Kreveld
What is left of the nuclear debate after the politics are strained out? Answer: several unanswered questions. What is happening to system strength as we transition towards more inverter-based renewable energy sources and are we signalling confusion to the renewable investment community with our political bickering?
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System strength is in decline as more renewable energy resources crowd out the remaining synchronous sources, chiefly coal and gas. Investors are likely to look at opportunities elsewhere because it is difficult if not impossible to assess risk factors associated with changes in government renewable energy policies notwithstanding the current government’s capacity investment scheme, designed to underpin investment.
The necessity to replace coal-fired generators with nuclear ones, described by some commentators as a ‘no-brainer’, is based on rather facile reasoning: it’s ‘clean energy’ and always available, unlike wind and solar.
As far as the 2030 renewable target is concerned, the time scale is too short for the nuclear option. AEMO’s 2024 integrated systems plan indicates a plentiful supply of generation capacity, which would deliver the 2050 yearly energy target of 400TWh, utilising only 15% of by then available capacity.
This appears to remove the worry of shortfalls when the sun doesn’t shine or the wind doesn’t blow. However, system strength is another matter because the inverters of wind and solar sources have about a quarter the reactive power for system strength support that synchronous generators have, be they coal, gas or nuclear.
A more sophisticated argument for nuclear energy might be that with sufficient capacity, system strength would be less of a worry because conventional synchronous generators would be employed. That, however, given the forecast over-capacity by 2050, is not an argument for a nuclear option since over-capacity could be in part employed for reactive rather than real power support.
Rather, the discussions should focus on other means of retaining synchronous capacity. These include synchronous condensers, low temperature differential organic fluid Rankine cycle turbines and sensible heat storage in graphite for conversion to steam to drive conventional turbine-generators. The latter technology is being trialled in Queensland and offers a reliable heat storage alternative to excess renewable electrical energy storage in batteries.
The nuclear debate appears to be born as much out of exasperation as a reluctance for analytical examination of Australia’s short and long-term electrical energy needs. Technologically, inverter-based generation for solar sources or type 3 and 4 wind generators is now well-established.
Questions remain on the voltage stability of transmission systems solely relying on these sources but the solutions are there to be availed of, for example synchronous condensers, static synchronous compensators, var compensators and voltage-forming inverters associated with large-scale battery storage.
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The wisest course of action, therefore, appears to be an intensive engineering and procurement effort to ensure the security and stability of electrical energy as the transition to renewable sources continues rather than restarting unhelpful and investment-confusing political debates.
