The solar farm that winds down at dusk, charges up for dinner and is still generating at midnight

It’s been fascinating to watch the progress of Australia’s first large scale solar-hybrid power plant at Cunderdin in Western Australia. This sort of facility may be new to the Australian grid, but the technology could form a large part of its future generation mix.

The Cunderdin plant, owned by the Spanish company Global Power Generation, part of the Naturgy Group, combines 128 megawatts of solar with a 55 MW, 220 MWh battery. They are not just co-located, they share the same connection point, making them a true hybrid.

The facility runs pretty much on the same principal as a household with rooftop solar and battery storage. In the case of the home, solar power is consumed on site or stored in the battery for later use.

Some households now have retailer deals that allow them to control when they send power to the grid, avoiding the tuppence halfpenny paid for the average solar export tariff, and earning serious money when the price is high.

That’s roughly the plan at Cunderdin. It sends power to the grid in the middle of the day, but if the wholesale price on offer is not attractive it will store as much of its output as it can in the batteries, and keep it there before sending it back to the grid in the evening demand peaks, when prices are generally higher.

Renew Economy wrote an earlier story noting how the Cunderdin facility had developed a pattern of sending a reasonably constant output of solar back into the grid in the evening – around 45 MW for several hours.

The pattern has since changed. As this graph above illustrates, taken from three days of production late last week – courtesy of OpenNEM – the solar farm is now often still injecting power into the grid after midnight local time.

The battery can’t store all the solar produced in one day, so decisions are taken on sending power to the grid when it is most profitable. One pattern that is clear is the pause in output later in the day as the sun goes down, and then a burst of activity after the sun sets and grid demand – and usually prices – start to increase.

It is no accident that the only new generation projects that reached financial close in the first half of this year were solar farms paired with battery projects, including Fulham, which is combining 80 MW of solar and 128 MWh of battery storage in Victoria’s Latrobe Valley.

Solar and batteries are the only technologies falling in price – battery cell prices are plunging as quickly as solar PV did last decade. They are modular, scaleable, quicker to build and generally attract less community opposition, although batteries have become a new focus of transition opponents.

And with wind projects facing increasing community opposition, and transmission projects also facing a blowout in costs, there are many who suggest that solar and battery hybrids could deliver much more of Australia’s energy needs than previously forecast. Time will tell.