Rooftop solar slashes demand levels and emissions across main grid

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Australian Energy Market Operator data shows rooftop solar pushing down demand in daytime hours and reducing emissions.

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The growth of rooftop solar continues to have a major impact on Australia’s electricity grids, with the Australian Energy Market Operator reporting significant declines in operational demand in the latest quarter.

The market operator also credits solar for having a major impact on the emissions intensity of the main grid.

“The largest decrease (in emissions intensity) occurred at midday due to increased penetration of solar PV,” it said in its latest Quarterly Energy Dynamics report. (See top graph).

AEMO noted that average operational demand reduced by 362MW in the three months to June, compared to the same period a year earlier. The biggest falls were in NSW ( minus 130 MW) and Victoria (minus 111 MW), which it said was driven by additional rooftop solar PV output and mild peak-time temperatures which reduced heating requirements.

“Reduced demand in Queensland (minus 75 MW) and South Australia (minus 22 MW) was a function of continued growth in rooftop PV output over the middle of the day,” it noted in its latest Quarterly Energy Dynamics report.

The increase in rooftop solar, along with the big growth in large scale solar and wind energy, is changing the dynamics of the market, usually pushing down demand in the middle of the day, when traditional coal and gas generators expected to make pots of money.

AEMO says that overnight generally remains the time with the lowest demand in most of the National Electricity Market, but this is now being challenged by the impact of rooftop solar.

In South Australia, the minimum demand is now almost exclusively in the middle of the day, or late morning. It used to be between 3am and 6am.

A new record low for minimum demand in South Australian was set at 1.30pm on April 27, when operational demand dropped to 749MW. This was 44MW lower than the previous second quarter record last year.

At this time, rooftop PV provided approximately 600MW of output.

AEMO noted that minimum demand levels in South Australia have been declining for almost a decade, largely driven by increasing uptake of rooftop PV in the region.

The state now was more than 1GW of rooftop PV installed. with a penetration rate of more than 30 per cent. The state government now has schemes that encourage the installation of battery storage on new and existing solar households.

The AEMO report also noted that average large-scale wind and solar generation across the NEM increased by 47 per cent from 1,551MW to 2,275MW, increasing its share of supply to 10 per cent from 7 per cent a year earlier.

Some 1,500MW of new capacity began generating in the three month period, with 1,020MW from wind and 427MW from solar, and almost half of this coming in Queensland, where the majority of large scale solar projects are being built. (See tables above).

All this has an impact on the profile of the main grid, with this graph below showing the changes over the last 12 months, with solar additions focused on the day-time hours, wind across the board.

Meanwhile, brown coal fell across the day due to various outages, while black coal (the darkest colour in graph below) had a mixed outcome, pushed out of the market by solar during the day, and sneaking back in at night-time. Gas and hydro also lost out, but hydro stores are also at low levels.

See also out story: AEMO seeks emergency reserves as coal outages increase across NEM.

Wind generation increased by an average of 406MW, due to new capacity which has commenced generation since the same period last year. The NEM-wide average wind capacity factor was 31% compared to 32%.

Large-scale solar generation was up 281 per cent to 318MW as additional capacity was brought online. Most of the increase in large-scale solar output was in Queensland (up 61 per cent to 195MW,). Average Q2 2019 rooftop PV generation increased 19 per cent from 669MW to 827MW compared to the same period last year.


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