How rooftop solar has dramatically shifted and reduced peak demand

How rooftop solar has dramatically shifted and reduced peak demand

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Fossil fuel lobbyists argue rooftop solar does not reduce peak demand. But new data shows that it cuts peaks dramatically, and pushes them into evening.

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One of the most common arguments “against” rooftop solar PV is that does nothing to reduce peak demand. It is one of the base arguments from regulators and fossil fuel companies against higher tariffs for solar. But a new report from the Australian Energy Market Operator shows it to be complete bunkum.

The detailed annual report into the West Australian electricity market by AEMO – the first since it took over operations of the WA grid from the Independent Market Operator – reveals that rooftop solar PV reduced the highest peak in WA this past year by 195MW.

wa peak feb 8

On February 8, the third of a four-day heat wave of temperatures above 40°C, the state’s 560MW of rooftop solar pushed the peak an hour later into the evening – to between 5.30pm and 6pm – and cut demand significantly.

Without solar PV, AEMO notes the peak would have occurred between 4.30pm and 5pm and would have reached total demand of 4,204MW.

With solar PV, that peak was pushed back an hour and cut to 4,013 – still a record in the WA grid by a considerable margin. (The previous record was 3,857MW in 2012). And that is despite the fact that the rooftop solar was only operating at around one-fifth of its capacity at the time due to the falling afternoon sun.

wa peak reduction forecast

And it is not a one-off. AEMO predicts that rooftop solar will proliferate in the west. In just the last two years, the price of a 5kW rooftop solar system has halved, and AEMO estimates that within a decade rooftop solar PV will triple and reduce peak demand by up to 650MW. In the last 9 years, solar PV has pushed the peak back by 2.5 hours on average.

Peak demand could be further reduced by the anticipated uptake of battery storage. Right now it has negligible impact, but within a decade it could be knocking a further 62MW off peak demand.

This has important ramifications – not just for the way that solar is treated, but the way the network is managed. Across Australia, networks have been given licence to spend billions preparing for peaks in demand that never materialised, passing on the costs of the infrastructure to consumers on the basis of “reliability.”

In WA, this has added significance. The market includes “capacity” mechanisms which have provided subsidies for more generators to be built to meet those assumed peaks. But many of these plants have never been switched on, because they are not needed. Yet they pocket up to $12 million each a year.

Indeed, another WA incentive, demand response mechanism, reduced peak by just 72MW on the day that rooftop solar cut it by nearly 200MW. Yet the demand response initiative has paid out $400 million and has been used on just eight occasions.

WA is not the only market to experience a reduction in peak demand from rooftop solar PV. South Australia has also experienced significant reductions in peak demand due to solar, and so have Queensland and NSW.

The WA report – like the national report also released today – shows that although consumers are using more electrical appliances, growth in energy delivered from the electricity network has softened, due to decreases in average consumption per connection. This is due to solar and more energy efficient appliances.

The adoption of energy management systems and battery storage is expected to continue this trend by enabling households to have greater control over when and how much electricity they consume.

WA pv system pricesAEMO expects the strong growth of rooftop PV capacity in the SWIS (The WA grid) to continue. It cites declining system costs – down half in less than four years for 5kW systems – rising grid tariffs, and changes to consumer attitudes and behaviour. Solar PV output is forecast to triple to more than 2,500GWh within a decade.

“Electricity consumers are becoming more aware of existing and emerging technologies such as rooftop PV and battery storage, and are considering ways to optimise their electricity consumption behaviour,” it says.

AEMO expects the demand peak to shift a further one hour back to between 6.30pm and 7pm, particularly as more west facing panels are installed. By 7pm, the average system is only producing around 4.7 per cent of its rated output due to the setting sun.

peak wa battery storageThe peak could be further delayed, and reduced, by the anticipated rapid uptake of battery storage, with AEMO predicting it could reduce peak demand by more than 60MW within a decade.

But as solar and storage increase their influence, the remaining fleet is posing headaches for the grid operators and policy makers. Nearly half of the peaking generation is less than 10 years old, but obviously not needed. Around 60 per cent of coal-fired capacity is more than 35 years old.

WA is now facing a significant surplus of capacity, which is one reason why energy minister Mike Nahan has ordered the closure of 380MW of capacity, which should lead to the closure of the state’s oldest coal generators.

He has also announced reforms designed to address the huge amounts of money given away in the capacity markets and demand response markets.

Indeed, Nahan has talked of a future dominated by solar and storage, and the state-owned network operator Western Power is also considering a future where its business model is fundamentally changed and it focuses more on micro-grids and “thin connections” rather than a one-sized-fits-all network.

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  1. Charles 4 years ago

    It makes you wonder when states are going offer better FIT rates for west facing panels. May be a moot point with the advent of home batteries, but (depending on the roof shape) it doesn’t cost any more to face the panels in a different direction.

    • Andrew Roydhouse 4 years ago

      Does not cost more to install.

      BUT does generate less electricity than a north facing array – so higher cost per total expected yearly kwh generation.

      Makes sense when not enough north facing roof space +/or when you are home to use the late afternoon solar power generated (assuming no batteries).

      If you have batteries then north is the way to go,

      • Charles 4 years ago

        Yes it generates less – hence the suggestion of a premium FIT (just enough to offset the lower total generation amount) for anyone who does so. More generation in the late afternoon/evening is better for the network as a whole.

      • Alan 4 years ago

        If you don’t have storage, then that extra energy produced in the middle of the day is practically wasted so you might as well face them west and use more of the energy you produce / further support the grid.

        • Andrew Roydhouse 4 years ago

          Well yes you can be a philanthropist but given how all State Govts have built up the fattened calves for privatisation – I am not keen to fatten certain investment banks’ wallets.

          The daily access fees have been so distorted that now for many ‘energy conserving’ or “low-income” or ‘frugal’ households the cost of connection is higher than the cost of the power itself.

          Look at AGL and retail gas in NSW – the more gas you use the cheaper the cost per megajoule.

          Our house has produced slightly more solar power than it has used in total over the last nearly 3 years. However, the excess that we generate that ‘helps out the grid’ does not benefit us but the investment banks and purchasers of the previously public assets.

          Once the economics come positive – batteries will be making an appearance for us. Daily tracking of consumption/usage since installation shows that we could go off-grid with only a small back-up generator required.

          Allowing for the inefficiencies (losses) with powering up the batteries etc – would have seen a small generator used for our 5 person household, for 22 hours over the last nearly 3 years as long as we had 18 kwh of storage.

          If 15 kwh storage then it would have been 38 hours of use.
          If 12 kwh storage then 65 hours of back-up generator.

          A bit like, very crude analogy, the two jerry cans we bought in a sale. Using them to fill up (storage) when we think the petrol price cycle has troughed and then use them to fill up our cars until the next trough is close/reached.

          The capital cost for the jerry cans was paid off in under 3 uses. Cars were approaching empty and petrol prices had not come down – so used the jerry cans.

          If only batteries for solar power were that keenly priced!

    • solarguy 4 years ago

      Hello Charles, no it’s not a moot point with batteries, having west facing panels. If a family that both mum and dad work and the kids are at school during the day, the most power consumption starts to occur about 4pm.
      On a hot summer arvo this is when the kids come home from school, on goes the air con, TV, Xbox, etc. Later on the stove for tea as well. So west panels are a great idea as you wouldn’t want to take valueable power out of the batteries at that time, best to use storage after the sun has gone.
      However you would still need panels facing north too, to not only charge the batteries but to supply power for the air con on the weekends.
      Houses must be designed to take advantage of this, including better passive solar design for energy efficiency. Government must introduce legislation to cater for this for new builds.

  2. JonathanMaddox 4 years ago

    If it looks like a duck…

  3. Brunel 4 years ago

    An UHVDC transmission line from WA to NSW would allow solar panels in SA and WA to power the east coast after the sun sets in Sydney.

    It would also allow solar panels in the east to power Perth in the morning.

    Also, if it is raining in Sydney, that does not mean it is raining in WA or SA.

    • solarguy 4 years ago

      Yeah that would work, but at an unacceptable cost for a few hours of power. And don’t forget the maintenance costs.

      • Brunel 4 years ago

        What maintenance cost?

        China now has a 3000km long 1100kV line.

        India is testing 1200kV!

        • solarguy 4 years ago

          In the first instance distance is MONEY. India hasn’t got that tyranny and mate there is always maintenance on anything, China has a very huge population, compare apples with apples, Australia has 24 million, China would have that amount of people over that distance.

    • Andrew Roydhouse 4 years ago

      Is it possible? Yes.
      Is it profitable? No.


      The transmission losses for crossing the extra couple of thousand kilometres would be around 1/4 the power transmitted (at the least).

      The demand for aircon etc in the West (as school children start coming home) would match into the early evening demand rise on the east coast.

      One of the major benefits of ‘distributed generation’ (roof top solar is one type) is the massive reduction in transmission losses.

      Compare with example of moving panels from north facing to west facing: you suffer a loss in amount generated for the benefit of slightly later generation window.

      That’s not the main game. If there was a true commercial benefit of generating during that time frame then the Snowy Mountain generators would be producing then. Some of their plants are just giant ‘batteries’. They let the water run from the high reservoir to the low one to generate power when they can sell at above a certain price. Then during the night, when the low rates are reached – they buy power to pump the water back up to the high storage.

      They can counteract ANY re-occurring high price periods.

      • Brunel 4 years ago

        The losses are 3.5% per 1000km for 800kV DC.

        In China they built 1100kV DC.

  4. john 4 years ago

    The very well documented change in the amount demand power which prior to solar was a bell curve and now is changed into a duck curve, where the peak is towards the evening will be the next hurdle to cross.
    This of course will be done by installation of battery backup linked to solar systems.
    In the domestic situation this means those 8 to 12 KWh of power usage from 5 to 9 pm will be drawn from the battery pack.
    The savings caused by this change will be beneficial to all users.

    • Andrew Roydhouse 4 years ago

      Am I too much of a cynic?
      Hydro-electric schemes can be (in most cases) just thought of as a combination of a power generator AND ‘battery storage’.

      They are very good at balancing out loads and have next to no delay in starting from idle – the sluice gates just get opened and the water powers the generators.

      Is it because there is next to no money in it for the private sector compared with selling (at retail margins) to the general population a high tech alternative?

      For example, in Qld the regular flooding around Brisbane (happens once developers get Councils to rescind the bans on building homes in flood plains), has seen frequent calls for increasing the size and number of dams to control flooding events.

      Not only would it save on average over $150m a year in property losses, significantly more in lost wages/production/business/productivity etc – it could also act as a major power generator and battery.

      Just like the Snowy scheme pumps the water back up to the top storage when the power prices plummet in the middle of the night and then generate power when the prices get many times higher – so could this be done.

      Perhaps as it would cut the overall cost to the community in power prices, and reduce the profits for the State owned fossil fuel generators as well as not make mega-profits for any donors to the political parties – IT WILL NEVER happen.

      When does community benefit ever seem to over-ride the un-named donors demands?

      • john 4 years ago

        Pumped storage does work, if as you mentioned being able to buy the power at low price periods to pump the water.
        As to the situation in Brisbane what happened is that the low level creeks were filled in to make playing fields which meant that the flood water had to go somewhere.
        The subsequent flooding of houses and business results in cost to community.
        Yes the Wivenhoe Dam was built as a flood mitigation measure to prevent Brisbane being flooded.

        The discussion is about power demand and solar has taken away the previous peak and shifted a lower peak to the evening and the next lower peak is in the morning.

        Both of which can be lessened by utilizing storage batteries, which I expect to be a logical solution at this time.

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