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By Kate Cranney Chris Fell Gregory Wilson 30 March 2020 7 min read

Thick smoke covers Sydney after fires in 2013 (Image: Andrea Schaffer)

This summer, smoke from bushfires blanketed towns and cities across Australia. At the same time, dust storms descended on western New South Wales, with dust clouds "so thick they blocked out the sun". And in Canberra, hailstorms lashed the city, damaging cars, infrastructure and solar panels.

What does this smoke, dust and hail mean for Australia's solar power plants, and the two million homes fitted with solar panels? How much energy will residential solar panels produce when you can barely see the sun?

Conventional energy and extreme weather

Before we look at renewable energy, it’s worthwhile noting that extreme weather events also affect conventional energy generators.

Summer is a challenging time for the reliability and security of coal power generating units.

A 2019 report[Link will open in a new window] by The Energy Security Board stated that "... weather events are now more severe, especially over summer, and the thermal generator fleet is ageing and increasingly less dependable." For instance, in early 2019, during a heatwave in Victoria, a substantial portion of the state’s coal generation was offline, with faults at a coal plant in the Latrobe Valley.

Add to this the damage to infrastructure. Recent bushfires destroyed or damaged electricity infrastructure, including power poles, lines and substations, this includes interstate links. Early this year, thousands of homes and businesses were without power when fires destroyed poles and wires in New South Wales and Victoria. ‘Mega-fires’ also narrowly missed[Link will open in a new window] the Mount Piper Power Station and the Springvale Coal mine.

With this in mind, let’s look at the respective impacts that smoke, dust and hail have on solar energy production.

Bushfire smoke and solar power

Since widespread bushfires began in October 2019, parts of Australia have been blanketed with smoke.

Bushfire smoke causes elevated particle levels in the atmosphere. Smoke from bushfires is made up of gases, water vapour and particles so small they're not visible to the human eye (the NSW Health Department and EPA estimates some particles are smaller than 2.5 microns in size, which is about three per cent the diameter of a human hair).

These extreme aerosol events can significantly reduce the power generated by solar photovoltaic (PV) plants.

"Simply put, anything that blocks out the sun will reduce the amount of energy that your panels will produce," explains Principal Research Scientist Dr Gregory Wilson (Head of Solar Technologies). Solar energy production can also be affected by the ash, which can leave a thin layer of grime on the surface of panels.

What reduction in solar photovoltaic (PV) capacity do you see on a hazy day?

Solar monitoring company Solar Analytics found that rooftop PV system output in Sydney and Canberra dropped by 15–45% on heavy smoke haze days. "On New Year's Day, when Canberra choked under highly hazardous smoke haze with an air quality index more than 3400, solar PV output in the capital plummeted by a costly 45%. Analysis of solar PV sites in Sydney on December 10 showed a 15% drop in production, and on December 21 this rose to a hefty 27% drop."

In 2014, CSIRO researchers calculated the impact of the smoke aerosols produced by controlled burns outside of Canberra on solar PV power production at one of CSIRO's solar monitoring stations. While this was a relatively minor local council-controlled burn, the researchers still found it measured a peak reduction of 27% when the smoke plume obscured the sun.

In 2019, Dr Wilson monitored the solar production at CSIRO's Newcastle Energy Centre; the image of the Energy Dashboard below shows three peaks over three days. The smoke haze drifts across on midday on one (December 4) and remains, reducing the peak solar power output by about 25%. With over 300kW of solar PV panels installed Newcastle on-site, the haze impacted our renewable generation.

"At our Energy Centre, where there's a nice ocean breeze, on the hazy days we still saw a significant loss in the energy production from our solar panels: it was down 10 to 30%, compared to last year."

Energy Dashboard for the CSIRO Newcastle site, for photovoltaic power generation over three days in December 2019. Smoke haze drifts in around midday on the second day, reducing the output from our PV generation by ~25%.

Dust storms and solar power

"When a thick layer of dust accumulates on a solar PV system it can have a significant impact on output," explains Principal Research Scientist, Dr Chris Fell (PV Performance Laboratory).

"Like smoke, dust storms fill the air with particles that scatter sunlight away from the ground, meaning less solar energy where it's needed. Unlike smoke though, dust storms contain larger particles that typically fall out and cover everything in sight." See image below.

This photo shows the dust that has settled, with rain, on a solar panel, following a dust storm (Image: Jesse Wagstaff)

The severity of the dust fallout problem depends on many factors; in particular the composition of the dust, proximity to the ocean, and the weather conditions at the time. Sandy dust is less likely to adhere, whereas clay-like dust is more of a problem. Wind tends to remove some freshly deposited dust, whereas still conditions, particularly if concurrent with high humidity and salt air, can enhance dust adhesion. When light rain occurs at the same time (e.g. the 'mud rain' that has recently been seen in Melbourne) the result can be the rapid formation of heavy 'soiling', as it is known in the industry.

"Perhaps the most important impact of bushfires and dust storms on Australia's energy grid relates to their unpredictability," explains Dr Fell.

"As the penetration of utility-scale solar systems (solar PV farms) on the grid increases, the stability of our electricity supply is becoming more and more dependent on operators of these facilities providing accurate forecasting of the power they will inject (into Australia’s electrical grid)."

A recent survey of solar PV farms by the Australian Renewable Energy Agency (ARENA) saw several farms report that the recent conditions had adversely impacted either their energy output or their ability to forecast energy generation.

Hail storms and solar power

Modern solar PV panels are highly stable in the outdoor environment, but one of their weaknesses is large hail – normally anything above 25mm in diameter. Large hail contains much more destructive energy than small hail (less than 25mm) since larger stones are both heavier and reach a higher terminal velocity before reaching ground level.

Although the surface of the solar PV panel is a thick layer of toughened glass, the high-impulse (short and sharp) impacts generated by high-velocity hailstones are very challenging to withstand – without making the panel both heavy and expensive.

The hailstones that hit Canberra’s CSIRO site, in January 2020, were golf ball-sized, weighing about 20 grams each. As this weather becomes more frequent with climate change, product performance will need to reflect this, and it may be worthwhile re-visiting Australian’s Standards for solar PV panel construction.

In January 2020, hail damaged solar PV panels in Canberra. (Image: Capital Solar Maintenance).

Solar power in Australia’s energy mix

Over 2.2 million Australian homes and businesses now have a rooftop solar PV system—over 220,000 of which were added in 2019. This can be higher than 70 per cent in some urban areas, on free-standing residential homes, according to the Australian PV Institute's latest report to the International Energy Agency. Australian Energy Market Operator (AEMO) forecasts that, by 2040, rooftop solar PV systems on households and businesses will supply a quarter of the country's energy needs.

The scale and number of medium-scale[Link will open in a new window] and large-scale solar PV plants also continues to grow. "Not only did 2018 produce a record number of projects being completed, but it also delivered the six largest solar farms in the country…. The amount of large-scale solar installed around the country more than quadrupled in 2018, increasing from 382 MW in 2017 to 1824 MW in 2018," reports the Clean Energy Council.

The full impact of extreme weather events on solar farms is uncertain. Looking to the future, the amount and type of aerosols will need to be considered in the analysis of solar PV power, to obtain accurate forecast scenarios and improve the grid integration, especially during extreme weather events.

The solar farm outside Broken Hill (Image: Jeremy Buckingham)

Extreme weather and Australia's energy grid

In the face of climate change, extreme weather events will continue to cause damage to energy infrastructure. Renewable solar PV infrastructure is just as susceptible to extreme bushfires and wild storms as fossil fuel and nuclear power infrastructure.

But this summer has been a reminder of the benefits of decentralised energy production and improved energy storage. By having distributed renewable energy at home, like solar PV panels and battery storage, homeowners can minimise power outages (like blackouts) that happen after wild weather and catastrophic bushfire events.

There's also an opportunity to revisit Standards for solar PV panels to withstand more extreme hail, and to explore new, tougher designs.

CSIRO researchers are ensuring that solar energy continues to be a reliable power source and one that we can harness to transition to a lower emissions future.

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