Rooftop solar slashes demand levels and emissions across main grid | RenewEconomy

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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  1. Craig Fryer 6 months ago

    Almost none of the new wind generation in QLD has actually been active even half way through the 3rd quarter.

    I wonder when the State Governments will realise it is time to reduce or remove any additional subsidies on residential solar. It is also time to start moving to residential FIT and rates that reflect the wholesale price.

  2. RobertO 6 months ago

    Hi All, So rooftop solar is reducing grid demand.

    I think we will see another drop starting (it has already started but it is so tiny today) to increase the drop in grid demand.

    We in Australia are going to have BEV’s increasing numbers and there are two factors which decrease the grid.

    Liquid FF need less pumping around the grid (every time you fill with fuel that a 2 kW electric motor running for about 3 minutes is one example, some trucks take 20 minutes to fill). A slow but sure reduction in ship to shore via a pipeline to Clyde, tank to tanker truck, and closing of oil pipelines where we pump it (Sydney to Newcastle is one example). We used to send petrol/diesel via the railway to say Parkes but now we use road transport. At Southwest Rocks there was a buoy off shore that a ship would tie up to, and pull up a hose connection and pump petrol/diesel into tanks. I am not sure if they still do this.

    Some of those BEV’s will fill up with behind the meter solar power (possibly 95 % today use the grid) and it mostly at nighttime but that will change to daytime and more will be from behind the meter.

    As we get more BEV’s with V2G or V2H (and it will only be a small amount say 10 kWhr our of your car battery fully controlled by your smart inverter attached to your solar panels talking to your car computer about the rules you set (2.4 kW per hr or equal to say 12.5 km per hr draw on the battery) between 6 pm and 10 pm or whatever time you set. It will also be readily reset if you know you need a full battery for tomorrows driving. It is using a standard power point connection.

    Some BEV’s will only charge daytime (part of your work terms and conditions and behind the meter) and only discharge at home.

    As for Hot Water Service how long before they move. All will move to daytime but some will also move to behind the meter.

    Household batteries will do the same on the grid numbers.

    The grid numbers will drop more than the rise in natural numbers.

    Only one issue will increase the grid numbers (note that my estimate of FF Grid numbers is about 6 GW and they all go).

    If we add exports of VRE the grid numbers will rise.

  3. Glenn 6 months ago

    Renewable’s got to 42.9% of generation nationally today, not sure what the record is?

  4. Maddogeco 6 months ago

    Hopefully we get a drought breaking spring that fills all the dams up, both water supply and hydro dams. That will kill gas. Meanwhile the wind and solar/ battery combo will kill off coal.

  5. Chris Drongers 6 months ago

    Changes in the timing of ‘off peak’ cheaper electricity use for hot water, pool pumps should be starting to happen now. I know that in Qld ‘off peak’ is ripple controlled and actually covers 11+ hours of the day; from experience that my hot water reheats during the day as well as overnight it is apparent that power is cheap in the suburbs between the morning and evening peaks, and during sleeping hours.
    Is there enough data available to do an article on how off peak power and other controllable demand is being adjusted to smooth generation profiles? Hopefully retailers aren’t adjusting off-peak hours to maximise profits rather than reduce costs.

  6. Ray Miller 6 months ago

    This increase in VRE is good news but should trigger a number of nuances in the implementation of distributed renewables. We need to find a way of increasing/encourage PV generation in the late afternoon, coupled with the battery storage to (from the grid perspective) to extend the PV generation into the late afternoon.

    Why are we still using electric storage hot water systems? The hot water systems should be at least heat pumps and run during the warmest part of the day.
    But the area requiring attention is the massive amount of energy being used in our buildings when we have extreme temperature events, for far too long improving the comfort of our buildings has been virtually ignored imposing massive costs to the overall price of energy. This year, yet again we failed to improve the minimum rating of our new buildings which directly impacts on our peak energy usage.

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