Rooftop PV appears in the AEMO record

On Friday Rooftop PV appeared on my favourite AEMO display for the first time, or the first time that I noticed it, and lately I have been checking all the boxes to find what each one contributes, all the way down to Waste Coal Mine Gas. As the level of demand and supply approached 36GW in the middle of the day Rooftop PV rose to 4GW and tapering off after 4 presumably due to north facing panels getting less of the western sun.

Can someone help to interpret these figures. How come it was listed for the first time, where could you find the rooftop figures before? I have read that it was up to 4GW but is that installed capacity, average, max, min etc. How much used in house and how much fed back into the grid.

Some other things, when wind is low hydro and gas ramp up, my question is how sustainable is it to ramp up gas and water for extended periods?

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43 Responses to Rooftop PV appears in the AEMO record

  1. Herodotus

    It’s like AEMO checking down the back of the couch for loose change.

  2. Singleton Engineer

    I will look around for hydro storage records. The operators in Tas and Snowy don’t use water levels or water volumes – they use stored energy figures, as in GWh or, otherwise, as percentages of maximum stored energy, but I’m rusty.

    Regarding the rooftop PV, in most cases behind-the meter PV has always only been able to be estimated not measured. I also noticed this week for the first time that some AEMO displays now include PV, but have no idea how reliable their figures are. I’ll keep a lookout for that, too, and report back what turns up.

  3. RobK

    I am not aware of monitoring of actual output of domestic PV by the authorities. It is possible but I’m not sure it is done. Ive always assumed the figures to be generated by BoM insolation figures, installed capacity and some efficiency factor. Rubbery at best. I too will ask around. Reneweconomy’s site has had a shaded area on it’s bar graph of consumption the AEMO doesn’t see (i.e.self consumption of behind the meter PV) for some time. I assume this figure is generated by algorithm and added to the production and consumption bars on the graph. My guess is the AEMO have followed suit.

  4. max

    More than 200,000 Victorian households had their power cut off yesterday in a bid to protect the state’s energy system from shutting down, as the Andrews government was forced to admit there was not enough power to keep up with soaring demand in sweltering summer heat.

    http://joannenova.com.au/2019/01/melbourne-200000-houses-blacked-out-10-companies-curtailed-as-1-in-5-year-hot-day-hits/

  5. More than 200,000 Victorian households had their power cut off yesterday

    No worries, a few beers today and it’ll all be forgotten by tomorrow. And anyway as we all know, the supply situation is fine, its demand that’s the problem.

  6. Cynic of Ayr

    I’m only applying practicality here, but say a house uses 16 kWh a day.
    Say, at a point during the day, the rate is 1 kWh per hour.
    Say, the panels deliver 1.1 kWh, so a miserable 0.1 goes to the grid.
    Say, the panels only deliver 0.9, so 0.1 comes from the grid.
    The meters, AFAIK, only measure the 0.1, in and out. The meters don’t know about the 1K being actually used by the house.
    This is unfortunate, as it gives the lying renewable energy hustlers a chance to lie through their teeth, and inflate the 1K usage to 2K. They can then claim that solar is supplying 2K. Who’s gunna know the diff?
    Of course, I could be wrong, but if the opportunity is there to fleece someone, the power companies will be right on it.

  7. Tel

    Say, at a point during the day, the rate is 1 kWh per hour.

    You are amongst friends here, just call it 1 kW.

  8. Bruce of Newcastle

    Rafe – AEMO publishes a big spreadsheet every 5 minutes with all the sources identified, and how much they are producing. Sites like Nemwatch grab that data and helpfully visualise it. Nemwatch always has had the small solar MW given for each state. The table below the bar graphs is especially helpful.

  9. hzhousewife

    More than 200,000 Victorian households had their power cut off yesterday

    It would be joyous if this could happen again on Mon Wed and Fri next week, just to ram home the point.

  10. Vagabond

    It’s more likely if there are hot days after Oz day. That’s when a lot of people go back to work and the schools start a week or so later. Hopefully those deluded brainwashed kids who were manipulated into demonstrating about gullible warming last year will experience the pleasure of no air conditioning in their classrooms.

  11. Dr Fred Lenin

    The appeasement to the globalist fascist gangrenes continues , anything to get gangrene preferences without which lots of comrades would lose their careers . Wonder how many comrades could face first past the post ekections ?

  12. MPH

    There’s no way rooftop solar produces that much power is there? And as mentioned above, if they come up with a dodgy correlation that adds an estimate of the household internal consumption to the overall demand they can tell any story they like.

  13. egg_

    It’s like AEMO checking down the back of the couch for loose change.

    +1

    The anemic AEMO.

  14. Rafe

    How much air conditoning can be supported by rooftop pv? I suppose the numbers are readily available but up to date i have not looked.
    My assumption is that the panels may be a break even investment long term and they put up the price for othets and destabilize the suburban grid.

  15. RobK

    Rafe,
    There are many variations possible (seehttps://en.m.wikipedia.org/wiki/Solar_air_conditioning
    Evaporative a/c uses little electricity and is effective in much of the dry Australian heat. (Not so good in humid conditions or in winter)
    I expect you may be refering to reverse cycle split systems (RC A/C) which are popular these days. (There is a model of this which isnt grid connect and only conditions air when the sun shines, i dont see this as really taking off).
    Little houses often have 3-5kW RC A/C, larger houses can be 7-15kW or more. The standard single phase suburban house tends to have a 63A connection, (about 15kW, depending on voltage and power factor, P.F.). Larger houses may have a 3 phase connection.
    The maxium demand of a load and its timing are central issues to your question. A household with a large PV installation to offset a large RC A/C load will possibly export power to the grid and run the A/c while the sun shines but this house becomes a load on the grid in both summer and winter when the sun is absent. The Feed-in-Tariffs may well still make it worth the comsumers while to oversize the PV system so it can “bank” FiT returns to improve payback time. This is a preposterous scheme from the point of view of grid stability as it encourages heavy maxium demand with the added swings of renewables while taxing the system with FiTs which are opportunistic and not worth what is paid.

  16. Anthony

    The question of how long hydro can go has puzzled me for a while because there doesnt seem to be much data that is easily found. I have inferred from news that the current Snowy Hydro can run full out (4.1GW) for 10-14 days. The upgrade should add another week amd 2GW generation.

    The rest of the country has another 4GW capacity of hydro. Unsure how long they can run flat out for.

  17. 2dogs

    Are these rooftop figures gross or net, i.e. do they include any consumption of PV by the home owner?

  18. RobK

     i.e. do they include any consumption of PV by the home owner?


    Yes, they do.
    Large and small scale RE certificates are paid out on gross production of electricity. Large scale (commercial, over 100kW) is paid on measured production. Small scale is paid on anticipated production over 15 years. Small scale certificates are about half the value per MWh because they are paid upfront and supposedly allow for inefficient installation and early demise.
    The figure reneweconomy uses, they term “demand that the AEMO can’t see”; that is, “self consumption”,that’s other term often used.

  19. Rohan

    2dogs
    #2918279, posted on January 26, 2019 at 6:08 pm
    Are these rooftop figures gross or net, i.e. do they include any consumption of PV by the home owner?

    Good point. Why do I smell a rat.

  20. yarpos

    “How much air conditoning can be supported by rooftop pv? I suppose the numbers are readily available but up to date i have not looked.”

    I can give you a practical example. We have a 3kW solar system, at peak times these days it generates about 2.5kW give or take (Latitude 37 above melbourne). At peak times on hot days say 11AM to 4PM we are still exporting to the grid while running a large split system (modern inertor style)in our living area. Of course as we transition past lunchtime power , or if we turn on more AC , we start to consume from the grid.

    Dont know how much is going out I would guess its minimal just doing rough numbers with the AC spec. We never registered for FIT so for billing purposes our panels dont exist.

    We can run the same split system, two ceiling fans and a large fridge on a 3.4kVA generator.

  21. John A

    yarpos #2918440, posted on January 26, 2019, at 8:39 pm

    We can run the same split system, two ceiling fans and a large fridge on a 3.4kVA generator.

    Yes, but what about anything else? Computers, telly, dishwasher (for Mr DiNatale’s benefit), lights, toaster, microwave, vacuum cleaner, freezer, clothes washing machine?

  22. yarpos

    “Yes, but what about anything else? Computers, telly, dishwasher (for Mr DiNatale’s benefit), lights, toaster, microwave, vacuum cleaner, freezer, clothes washing machine?”

    If the generator is running , its a black out. I am not interested in “everything else” at that stage, just the basics. In recent hot weather (pre this last really hot spell) we had a two hour black out in 35C. We sat inside quite comfortable, with the fridge on. Thats all we expect. People interested in running everything simply need to up the ante on generation and pay accordingly.

    The comment was really made for Rafe so he had some real world numbers for thinking about what power source supports what loads.

  23. Seza

    We have a 6 Kw (panels), 4.8 Kw (limited input to grid) that is sufficient to run one of our 5.5kw ducted air-cons during the daytime peak if it is sunny. Oversizing the panels brings benefits in keeping the inverters saurated, and also increases the solar rebate from the government as the STCs are paid on installed panel size, not output. If the are working back from the STC installed size, they know they are fiddling the books as this is nearly always larger than the inverter output. And they have no idea how much I am using internally, as it is netted out at the meter before it registers.

  24. Tel

    I should point out that the way they rate air conditioners is by the rate of heat transfer on the thermal side, not the electrical side… which makes them look a lot bigger than they are. If you check out some of the efficiency measurements, a unit rated at 2.5kW A/C actually consumes between 500W to 600W of electrical power depending on the make and model. The big units rated at 5kW consume proportionally more electricity according to the link below.

    http://www.currentforce.com.au/CompareAirConditioners.aspx

    The air conditioner is a heat pump, so the purpose is not to create heat but to move the heat you already have to a different place. That’s why they appear so powerful in the ratings.

  25. Mundi

    PV that reduces a houses load isn’t known.

    Even an exporting PV in a suburb will just be seen as a lower demand by the suburb.

    It would be possible one day to get proper measurements if you had smart meters etc, but at the present time no, it’s just reduced demand.

  26. egg_

    I should point out that the way they rate air conditioners is by the rate of heat transfer on the thermal side, not the electrical side…

    Yup, the Coefficient of Performance (COP) of the compressor is roughly 3:1, so a 3 kW A/C consumes roughly 1 kW of electrical power; however, its electrical motor requires roughly 3x the run power to start, so it’s best to dimension a generator based on the output kW value, so it doesn’t stall when the AC is turned on with everything else in the household running; inverter types can take 5x the motor run current to start but for a shorter period than DOL start motors of yore.

  27. RobK

    Egg,
    A fully inverter controlled A/c has a “soft start” compressor and has a lower start current than “direct on line” start. It also has variable frequency drive so it can run at any speed so it cycles less. Robustness of build is an issue with some makes.

  28. Dr Fred Lenin

    Dont worry comrades ,the andrew daniels guvmint is only a Hazelwood away from a solution yo the power problem . I mean most of the power cuts were in rusted on electorates of the pardee ,but we dont want to piss off the gangrene preferences do we ? On second thoughts ,who else are the watermelons going to preference ?

  29. Ve2

    Interest that PV works well around midnight, gotta get me some of those panels.

  30. yarpos

    “We have a 6 Kw (panels), 4.8 Kw (limited input to grid) that is sufficient to run one of our 5.5kw ducted air-cons during the daytime peak if it is sunny. ” Its actually way more than enough, you could run it with 3kw of panels and still export a little in steady state. You are comparing apples and oranges as other have said.

  31. egg_

    A fully inverter controlled A/c has a “soft start” compressor and has a lower start current than “direct on line” start.

    5x the run current for a longer duration than DOL (7x run current but shorter duration) – soft start actually has a greater area under the curve, so it’s a consideration in dimensioning a Gen-set so that the Gen-set doesn’t stall.

  32. RobK

    Egg,
    Variable frequency drives apply voltage proportional to frequency and can be limited to not exceed full load current.
    https://www.quantum-controls.co.uk/faq/drives/what-current-is-required-when-stating-a-motor-with-a-variable-speed-drive-inverter/

    What current is required when starting a motor with a Variable Speed Drive / Inverter?

    March 21, 2014

    When an AC motor is started “across the line,” it takes as much as seven to eight times the motor full-load current to start the motor and load.  This current flexes the motor windings and generates heat, which will, over time, reduce the longevity of the motor.  An adjustable speed AC Drive starts a motor at zero frequency and voltage. As the frequency and voltage “build,” it “magnetizes” the motor windings, which typically takes 50 to 70 % of the motor full-load current. Additional current above this level is dependent upon the connected load, the acceleration rate and the speed being accelerated, too. The substantially reduced starting current extends the life of the AC motor, when compared to starting across the line. The customer payback is less wear and tear on the motor (motor rewinds), and extended motor life.

    Starting an AC motor across the line, and the subsequent demand for seven to eight times the motor full-load current, places an enormous drain on the power distribution system connected to the motor. Typically, the supply voltage sags, with the amplitude of the sag being dependent on the size of the motor and the capacity of the distribution system. These voltage sags can cause sensitive equipment connected on the same distribution system to trip offline due to the low voltage. Items such as computers, sensors, proximity switches and contactors are voltage sensitive and, when subjected to a large AC motor line started nearby, can drop out. Using an adjustable speed AC Drive eliminates this voltage sag, since the motor is started at zero voltage and ramped up.

    Lower power demand on start: If power is proportional to current times voltage, then power needed to start an AC motor across the line is significantly higher than with an adjustable speed AC drive. This is true only at start, since the power to run the motor at load would be equal regardless if it were fixed speed or variable speed. The issue is that some distribution systems are at their limit, and demand factors are placed on industrial customers, which charges them for surges in power that could rob other customers or tax the distribution system during peak periods. These demand factors would not be an issue with an adjustable speed AC drive.

    This means that using a variable speed drives, given normal start conditions, then only full load current rating of AC Motor will be used.

  33. RobK

    soft start actually has a greater area under the curve,
    No. Especially not with variable frequency drive.

  34. egg_

    Mitsubishi HI Inverter 6.3kW
    Model SRK63ZEA-S1
    operational data
    Cool /Heat kW……….6.3/7.1
    Power Input Cool /Heat kW/h…… 1.84/1.86
    EER/COP ………3.4/3.8
    Energy Label Cool /Heat Stars ………..5/5
    Current Cool /Heat (max) Amp ………8.0/8.1 (12)

    I believe this is a brushless DC motor.

  35. RobK

    Current Cool /Heat (max) Amp ………8.0/8.1 (12)
    So it’s max A is 1.5 full load amps. This is much better than 6-8 times FLA. (The max amps may occur against excessive thermal gradient) In general VFD or inverter controlled motors have controlled low start current and speed is controlled so they run more constantly at lower power, cycling less. A better option for off grid (or on grid) use.

  36. RobK

    Egg,
    Your graph is of a current limited soft starter not a variable frequency drive. An auto-transformer starter has a curve like that. Not used much now, especially not in small motors. The thing with aircon is not only to save starting current but to achieve quiet operation. Varying the speed of the compressor and fan goes a long way to keeping the noise down. A side benefit is gentle runup current.

  37. RobK

    I believe this is a brushless DC motor.
    A brushless DC motor runs on inverted DC.
    https://en.m.wikipedia.org/wiki/Brushless_DC_electric_motor

  38. egg_

    A brushless DC motor runs on inverted DC.

    Hence, not having to build up a huge magnetic circuit* on starting per a squirrel cage AC motor.
    *The frequency slip from the magnetic circuit derives its high starting torque.

    I believe modern inverter compressors likely employ DC motors to keep starting currents down.
    Carrier? employs start/run mechanical loads on their compressor motors, essential two-speed mechanical devices (start mode is twice the speed of run mode).

  39. RobK

    I believe modern inverter compressors likely employ DC motors to keep starting currents down.
    That’s my point from the beginning. Both brushless DC inverter start and variable frequency drives have low starting currents for the same reasons.

  40. RobK

    Carrier? employs start/run mechanical loads on their compressor motors, essential two-speed mechanical devices (start mode is twice the speed of run mode).
    You are right in a sense, Carrier has been making split systems since before the late 70s, to my knowledge, so yes, that was before variable speed drives. I doubt there current lineup uses that technology unless it is made to a strict budget.

  41. egg_

    You are right in a sense, Carrier has been making split systems since before the late 70s, to my knowledge, so yes, that was before variable speed drives. I doubt there current lineup uses that technology unless it is made to a strict budget.

    I think it’s a carryover from their dual piston commercial a/c units pre-inverter technology.

  42. egg_

    I.e. mechanical DOD compressor plus inverter drive motor technology (Copeland compressor).

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