By Phil Kreveld
To whom the renewable energy transition is of great concern: energy ministers and advisers, either wake up to the problems you are causing with your favourite but conflicting ideas, or for the good of the nation, get out of the way and hand the planning job to a national engineering design authority.
Politically palatable policies and wishful thinking will surely steer Australia towards an unnecessarily expensive transition and duping of the public with subsidised policies for solar, and more batteries. Meanwhile solar installers steer customers to more powerful installations. High electricity tariffs confirm to householders that investment in solar seems smart and wishful thinking, on the part of state and commonwealth governments, encourages ‘no transition without transmission’ projects.
Related article: Politics and engineering—a dangerous mix
Well over 90% of all electricity generated is consumed in distribution networks. If between the hours of around 11am and 4pm, on the south-east coast, distribution networks generate sufficient energy to satisfy consumer demand-plus more (hence the growth of batteries), who needs more transmission to carry unwanted energy?
In fact, there can be no generation of unwanted energy—rather, no energy would flow in the transmission lines connecting distribution networks to distant generators. More about ‘unloaded’ transmission lines later. So, the solution we have come up with is to store excess energy from rooftop solar in batteries, therefore extending the period following sundown, that distribution networks can operate without need for importing energy.
The more batteries that are installed, the less externally supplied electricity is required. The purchase of increasingly powerful solar would make larger and larger capacity batteries a sensible purchase—but only to the extent that the stored energy could be used at a sufficient discharge rate so that they would be able to store more excess energy the next day. And if that cannot be achieved, what then? Store it in other batteries? Have a repeat of Callide C—and force synchronous generators to run as motors, blowing up their turbines?
Politically the nation is being misled in being asked to believe that more household solar means cheaper and cheaper energy. Were that the case tariffs should have been much lower already but we all know that it is not so. To add fuel to the fire, the Commonwealth Government is crowing about its Capacity Investment Scheme. Companies tender for solar and wind generation capacity, and they are reimbursed for losses if the contracted energy prices are not reached! The government wins if prices rise above contracted prices but with more and more self-sufficiency in distribution networks, chances are that the taxpayers will be going for their wallets in the end.
So, let’s get a little technical: household and business solar require a stable voltage and frequency. Increasing power ratings of rooftop solar causes power to flow in the reverse direction. The resulting voltage becomes heavily influenced by reverse power flow, and a phenomenon termed ‘harmonics’ (distortion of the voltage sinewave form). That causes instability in the solar inverters. To overcome this, distribution networks restrain power output from inverters, either switching off inverters remotely or reducing their power output. They’re figuring on solar system owners not noticing!
There’s more; the basically uncontrolled installation of solar inverters in the three-phase network causes dangerous earth and neutral voltages to build up. Distribution networks are aware of all this but—what are they doing about it? Another technical matter; when distribution networks take very little power from a transmission line, its voltage rises and becomes difficult to control—or expensive measures need be taken, for example the installation of thyristor-switched inductors.
Meanwhile the media soak up the press announcements; ‘renewables are very low-cost energy’; ‘there is no transition without transmission’; ‘nuclear is needed when the sun doesn’t shine or the wind doesn’t blow’; ‘community batteries will help mums and dads reduce their power bills’. None of it is, sadly enough, of any consequence because Australia has an uncoordinated, siloed, meandering path to its renewable targets!
Related article: Fibs about the renewables transition—and the cost of energy
Summing up the above, there are two policy trains hurtling towards each other—one of shoving more and more solar into distribution networks, and at the same time encouraging all that large scale generation and battery storage! There is what really seems a wilful blindness. At the recently concluded Australian Clean Energy Summit, the panel discussions gave the impression that all is hunky dory—it’s almost as if large-scale generation-transmission and distribution inhabit separate universes.
Who ends up paying for all these conflicting policies? It is a Hobson’s choice—either the citizen as consumer, or as taxpayer coughs up.
