Rooftop solar: Australia's greatest opportunity – and its greatest risk | RenewEconomy

Rooftop solar: Australia’s greatest opportunity – and its greatest risk

Why rooftop solar could be one of the grid’s greatest assets but also one of its greatest threats if not properly managed. Here’s what AEMO thinks needs to be done.



The rooftop solar PV systems being installed by Australian homes and businesses could become one of the grid’s greatest assets, making it greener, smarter, cheaper and engaging prosumers in the process.

But as the distributed solar market grows – currently at a record-breaking rate – the reality is dawning on the powers that be that tens of gigawatts of rooftop PV could also represent one of the biggest risks to the grid, if it is not properly integrated and managed.

And according to Dr Jenny Riesz – a principal at the Australian Energy Market Operator, and before that a UNSW research associate whose work focused on focused on high penetration renewable power systems – the time to address this risk is Right Now.

That’s because a failure to act could see AEMO lose its grip on grid control, starting within just five years.

“We are seeing enormous growth in distributed energy resources in our grid,” Riesz told this week’s APVI Asia Pacific Solar Research conference in Melbourne.

And that growth is showing no signs of slowing down. Riesz cites AEMO’s own “quite moderate estimate” projections that rooftop PV, which is at about 6GW now, is headed to around 20GW by 2030. realistically, it will quite probably more, as households and businesses race to hedge against rising power prices and as the technology gets cheaper.

“This is on a system that has a peak demand of only 35GW, so enormous quantities of rooftop PV, and potentially around 5GW of energy storage systems on our grid by 2035,” she told the conference on Thursday.

As AEMO chief Audrey Zibelman has repeatedly asserted, this behind the meter energy generation and storage resource has enormous potential to be harnessed by the market operator, in any number of ways, to help provide crucial grid balancing and particularly peak shaving services.

And extensive modelling by Energy Networks Australia has supported this view.

It showed that by orchestrating the nation’s distributed energy resource (DER), and coordinating the dispatch of it in a sensible way, network charges could be reduced by 30 per cent, annual savings delivered to households, and up to $1.4 billion in network investment avoided.

“So, really important that we pursue these opportunities,” Riesz said. “However, I want to emphasise that this (research) applied to well coordinated DER.

“If we have poorly coordinated DER, you can have quite the opposite effect. Instead of being our biggest opportunity, DER can be our biggest risk and our biggest problem on the grid.

“If we start seeing aggregated action from these systems that is not coordinated in a way that helps system security, it could have a severely detrimental effect, and increase the need for centralised investment. So, really important that we get this right.”

Riesz says that one of the major concerns around unfettered quantities of rooftop photovoltaics on the network is the excess energy that can’t be controlled.

“At the moment there is no framework for moderating the feed into the grid from rooftop PV systems,” she said. “We can turn down the large-scale wind and PV if we have to, but there is no way at the moment to control rooftop PV systems.

And AEMO’s most pressing concern, on this front, is South Australia, where the grid is already, at times, getting half of its energy from rooftop PV systems, and is rapidly heading to a scenario where 100 per cent of demand will occasionally be provided by distributed solar.

Riesz used the below “duck curve” chart to demonstrate why this could cause serious problems.


“You can see, in the blue is where we are at the moment. As we go forward in time, in the dotted lines you can see that demand going strongly negative in the middle of the day,” she told the conference.

“If no action is taken, this will severely affect AEMO’s ability to operate the system in a secure way at these times. So this is a risk to system security that needs to be managed.”

Riesz stresses that, in the early days, the risk posed by this would only really arise during “very, very rare” emergency events, such as extreme weather events and natural disasters, that occurred less than one per cent of the time.

And even then, such emergencies would only pose a risk if they coincided with periods of rooftop solar insolation being very high.

Another major concern for AEMO is the response of the rooftop solar resource to network disturbances.

“To understand that if you have a system that is 100 per cent running on rooftop PV and you have a disturbance like a severe frequency event, or a voltage dip, the response of those PV units is going to entirely dominate the dynamic response of that system,” Riesz said.

“Furthermore we don’t actually really even understand certain components of how these systems will respond, and neither do the manufacturers. When we’ve asked them about some of the less straightforward ways that they’ll respond, the manufacturers themselves don’t know, because it simply hasn’t been tested.”


For example, Riesz points to a voltage disturbance that affected the Adelaide area on March 3 this year, that briefly took out nearly half of the state’s rooftop solar generation.

“There was a severe voltage disturbance in the Adelaide area, and we estimate that something like 40 per cent of rooftop PV systems in South Australia ceased operation, and they were offline for what seems to be several minutes from the poor data that have available on those systems.

“What this means …if you project this forward is that if that happened in the middle of the day … we could be looking at losing a GW of generation in a region that only has 1-3GW of demand, and losing it for several minutes.

“And we simply don’t carry adequate reserves to manage that in SA, nor would that be cost effective to do so.”

So what’s the timeline for addressing these problems? According to Riesz, it’s actually frighteningly short: “Within the next five years or so, we enter the realm where AEMO no longer has the ability to ramp down interconnector flows to SA to zero, if we need to, for some sort of a system security reason.

“And that can happen, for example, if there were bushfires in the realm of those interconnectors, we typically ramp them down to very low levels such that if interconnector is lost, the system remains stable.

“We will no longer be able to do that within a very short timeframe, within the next five years or so. at these times, if we have those events coincident with these times when we have very high rooftop PV.”

Several years after that, Riesz says, around 2025-2030, AEMO would lose the ability to apply its standard measures to manage a forced outage on the network.

“So this is where there’s a fault on some sort of interconnector component, that means that one of the circuits is lost, we then ramp down the flows on the remaining circuit to lower levels such that if it was a credible loss of that circuit, we can then manage that without load shedding to customers.

“We lose that ability around 2025 to 2030. And then by 2035 to 2037, we actually reach the point where even under system normal conditions, we can no longer run the grid within secure limits. We will be overloading network components in these periods with no ability to turn down that rooftop PV.”

But the good news is that there are plenty of solutions. Most of them imminently achievable, using current technology, load shifting methods and software platforms. But they also rely on consumer participation. AEMOchartsolutions

“There is a huge amount that we can do about this,” Riesz told the conference on Thursday. “It’s just that we have to get on and do it. Now. Now is the time.

Key among the possible solutions is increasing daytime demand. This can be done a number of ways, such as shifting hot water clocks from night into the daytime; coordinating the distributed storage “that’s coming in at a rate of notts”; or using electric vehicle charging to mop up excess generation.

“Electric vehicles coming in could enormously help, And we could have other sorts of flexible loads like water pumping, and so on; if we provide the right tariffs and incentives, a lot more of that can be done during the day, to suck up this energy,” Riesz said.

AEMO is also looking at new interconnectors out of South Australia, Riesz says, which “for a whole suite of reasons” are likely to go ahead.

“That would enormously help, because it would give us capacity to export more of this energy from SA,” she said, although adding that this solution was somewhat time limited, in light of the fact that other regions of the NEM are also installing rooftop PV at an enormous rate.

Big batteries were another solution, although Riesz notes that utility-scale storage could be fighting a losing battle against distributed generation.

“I would point out that the Tesla battery that’s gone into SA, 100MW, will only buy us about one year, maybe even only six months at the current installation rates of PV that we’re seeing. And that is the biggest battery in the world right now, so we’re looking at an enormous amount of battery capacity to solve this problem, so it’s probably only a partial solution.”

A further fix would include network assets, such as increased voltage control, synchronous condensers, and potentially even resistor banks to soak up excess energy at times when AEMO doesn’t need it, particularly in parts of the distribution network.

And finally, Riesz says PV feed-in management is going to become “really important.”

“For that rare point in time when we need to moderate that feed into the grid, to keep it within secure limits, we will need the capability to be able to control those systems in some way,” she said.

And this chart below helps illustrate why.


“This chart is showing you the amount of demand response that we might be able to get from a range of different sectors, if we’re really aggressive and ambitious about it,” Riesz told the conference.

“You can see in this yellow brick here, the amount of demand that we would need on the most challenging day in 2035 to soak up the total excess of PV that we’re looking at and keep the system within secure limits. And you can see that, even adding up all of these extra demands sources, we’re still falling short.

“So this is something where we should definitely pursue all of these demand response options, but we cannot rely upon them to be adequate to solve this problem.

“We will need to curtail down some of these systems at these very rare times, to keep the system secure. And we think that it’s probably going to have to involve something like 90 per cent of all PV installed from around 2017 to make this work.

“So this is something where it probably is going to not be an opt in kind of scheme, to make it work get those sorts of participation rates.”

This is interesting to note for the nearly 2 million rooftop solar owners currently out there, and the many more to come.

But making sure it is a win-win for AEMO and consumers will need to be a key part of anything the grid operator comes up with, to avoid the sort of mass grid defection that will be much more doable in the not-too distant future, as battery storage prices continue to fall, and home energy management systems get smarter and easier to use.

As Risez puts it: “Customers want rooftop PV, they are choosing to install it, and we have a responsibility to enable that choice.

“And if we do manage these controllability challenges, potentially starting with understanding how we manage rooftop PV in a more orchestrated way, that can then unlock the orchestration of distributed energy resources more broadly. And that has huge potential for a more efficient and cost effective grid, engaging prosumers in the process.”

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  1. trackdaze 3 years ago

    Batteries and other storage can kill the duck.

    Also up to entrepreneurs to harness the zero cost energy in the middle of the day. Whether that be to produce hydrogen that is typically energy intensive and subject to efficiency losses or other energy intensive processes that arent quite profitable at current and future prices.

    • itdoesntaddup 3 years ago

      Can it? 4 hours of 20GW surplus requires 80GWh of new storage. Where is that going to be, at what cost?

      • trackdaze 3 years ago

        20GW? Thats not a duck its a giraffe.

      • Random Internet Dude 3 years ago

        There are around 1.35 million cars in SA. The Tesla Model X uses a 100kHh battery. So if petrol cars were replaced with electric that would create 135GWh of storage.

        I don’t think we will see that many EVs any time soon. But encouraging EVs and charging them in the middle of the day using solar power would go a long way towards dealing with this issue. As well as the other well advertised benefits of EVs.

        • itdoesntaddup 3 years ago

          Just so long as no-one wants to drive home during rush hour.

          • Random Internet Dude 3 years ago

            Your comment is stupid, and you should feel bad.

          • itdoesntaddup 3 years ago

            Please explain how you support the grid’s rush hour demand while driving home. Your stupidity is fully exposed.

          • Random Internet Dude 3 years ago

            Just as long as no-one wants to charge batteries during periods of high solar production, and discharge the batteries during periods of high fossil fuel demand.

            Most people (or at least those with functioning brains) actually think this would be a good thing.

          • itdoesntaddup 3 years ago

            I guess it hasn’t occurred to you that the battery discharge is to drive cars, not to power the grid, when you drive home. It may substitute for petrol or diesel, but it does NOTHING to power the grid. Idiot.

          • Giles 3 years ago

            The new Nissan Leaf will offer vehicle to grid capabilities, meaning it can and will offer power back into the grid. The world is changing. Please hang on.

          • itdoesntaddup 3 years ago

            While you are driving? And then when they’ve discharged your battery, you’re stuck until you can get a recharge again. It’s marketing, not a serious energy supply option.

          • Random Internet Dude 3 years ago

            The issue identified was what to do when solar generation exceeds demand. Storing electricity in batteries to use later isn’t stupid. It actually addresses the problem nicely.

            Also people driving cars on the road aren’t using a lot of grid power at the same time. Home usage increases when people get home (I seriously have to tell you that?), and the EV is plugged in again. So your grid comment is complete nonsense.

          • itdoesntaddup 3 years ago

            You do not seem to understand the basic concept of peak demand for electricity. So your comment is mostly complete nonsense.

  2. Mark Fowler 3 years ago

    I expect that sooner rather than later there will be a rule along the lines of “in order to connect to the grid there must be battery storage and energy management in place to control the delivery of power to the network”.

    • mick 3 years ago

      you know what happens then

    • MaxG 3 years ago

      See my post above; why would anyone even consider this idea for a second?
      I am sure there are enough people to buy a system paid out of their pocket, to then enrich the leeches. Absolute insanity. But then, people install malware Windows, use their mobiles as always on tracking devices, use FitBits to allow deciphering their movements (yes, you can tell what kind of activity you’re doing). If this is all acceptable, maybe the consumer, buys stuff to enrich the leeches… yes, I know, what happens every day and is called consumerism 🙂

      • Mark Fowler 3 years ago

        There is nothing to stop anyone going off grid but if you want to connect to the grid and sell electricity then the buyer has some rights and a responsibility to ensure the grid remains stable.

        • MaxG 3 years ago

          Agree… no doubts…
          However, I am not installing something for the benefit and control of others. The issue will be that my battery does something for a few Cents, while the other guy makes dollars off it … something I paid for and maintain. Think leasing, never pans out for non-business.

      • Chris Fraser 3 years ago

        If a rooftop solar Owner agreed, the DNSP could provide a meter, hardware and exclusive battery for their own FCAS usage, at their own cost. That utility would then pay for ‘rent’, maintenance, depreciation, and we dare suggest a ‘competitive’ feed-in tariff. I probably wouldn’t care but the DNSP would have to make a clear and transparent business case for it.

        • Hettie 3 years ago

          Isn’t that what Sonnen are doing?
          Sort of…..

          • Chris Fraser 3 years ago

            It might be good if they can. I foresee DNSP-Sonnen partnerships giving away batteries with caveats attached.

        • MaxG 3 years ago

          The issue will be that from a risk and cost perspective, you’ll get the short end of the stick.
          E.g. there are some maximising their export; I rather run my system on 60-80% and forgo any measly payment, but replace my e.g. inverters earlier (than otherwise under reduced load).

          • solarguy 3 years ago

            Exporting my excess power is quickening my ROI and loving it.
            Inverters, MPPT’s, will go tits up anyway, nothing lasts forever. Just keep the bloody things as cool as possible, when under high load, they will last longer. That way you can have your cake and it too.

            Happy days!

    • neroden 3 years ago

      Of course, if you already have solar and batteries, why would you connect to the grid? The grid would have to *pay you* to connect…

    • wmh 3 years ago

      Turn some panels around to face east or west and spread solar generation into the time when the sun is in the southern part of the sky. Panels facing west would be an advantage to net-metered customers on time-of-day tariff as it coincide with power at its most expensive.

  3. Chris Drongers 3 years ago

    If the 100MW Tesla battery will put off problems for 6 months as stated, then would a 300 MW pumped hydro put off problems for 18 months? Three pumped hydro schemes for 4 years? Would there be enough ‘spare’ energy available at low prices to run opportunistic desalination/hydrogen electrolysis/ice storage? Seems there is plenty of fruit around for a decade of picking.

  4. Patrick Comerford 3 years ago

    If you make the price of electric power affordable then the rules of supply and demand have a god chance of being effective. If you allow vested interest rent seeking interests to gouge the consumer then you have a problem. Any attempt to penalize the consumer and protect the vested interest generators and networks will not stand. We will simply with help from technology leave the grid.

  5. Chris Fraser 3 years ago

    I wish AEMO had talked to the DNSPs. The utility wariness of rooftop solar limits me to 10 kW, then 30 kW. What should it be ?Where was this rational thinking while Selectronic, Fronius and others bent over backwards to accommodate network export limiting devices in their inverter chargers ? Now perhaps, they wish to change this around to allowing network control of rooftop exports.It appears, almost embarrassingly, that rooftop solar could have lent some stability to the system while AEMO was paying through the nose for utility scale fossil and hydro FCAS. Good luck incentivising this use of rooftops for the greater good.

  6. MaxG 3 years ago

    Call this band-aiding — rule around rules to regulate the regulators; the root cause is a completely different one: privatisation!
    Generation, distribution and retail has to go back into public hands — only then and only then can sensible policy be enabled; can cost-savings passed on to the consumer. As long as there is profit-taking going on in these systems, the incumbent will do what capitalist firms do: profit-maximisation and lobby for rule changes in their favour. Another proof not to vote for stupid politicians.
    Since when does the public have to accommodate commercial interests? Why do I have to comply with any system that derives profits? (Other than to serve the public good; then I am in.) This system has turned upside down and people do not realise it. Absolute insanity. Why I have to say again: the only way to protect yourself from the corporate money grab is by not buying their product! In this case electricity… why I am self-reliant.

  7. Andrew Deme 3 years ago
  8. howardpatr 3 years ago

    The internet of things/blockchain type technology might see more localised large scale ESSs that can take electricity from many rooftop PV systems and also direct such surplus electricity directly to neighbours and back to the generators when required?

    Interesting times ahead but thankfully the AEMO is headed by forward thinker, (Zibelman), as opposed to the Chairman of the AEMC, (Pierce), who seemingly is a close ally of the gentailers and the Coalition.

    • Cooma Doug 3 years ago

      Spontaneous grid scale analysis and demand management.
      Combined with localised
      Fcas response in milli seconds.

    • Greg Hudson 3 years ago

      ”direct such surplus electricity directly to neighbours”
      A nice idea, but trying to find out ‘how’ to monetize this is turning out to be a big black hole (called Melbourne). I would love to be able to sell my excess power to my neighbors for say 15c/kwh during the middle of the day (or maybe even later if I had a big enough PowerWall2). As it is, they (my neighbors) get the power from me anyway because I’m exporting it to the grid, (I’m paid 11.7c) but they are paying full whack RRP for what I’m currently supplying them with.
      What we need is a decent blockchain system connecting PV exporters directly to neighborhood consumers IMO.

  9. Rod 3 years ago

    The low hanging fruit in SA is the water heating. Unfortunately we still have a lot of old “dumb” meters that would require a manual change from 11:30pm.
    Maybe AEMO needs to give SAPN and the retailers (who I understand are about to become responsible for meters) a rocket!

  10. AndrewATA 3 years ago

    We need a long-term plan for the grid, so our short-term actions are compatible with it.

    If we’re heading for 100% renewables (sure looks like it) then we need a LOT of energy storage. Mostly pumped hydro. That will also soak up the extra solar and fix these potential grid stability issues. So we need to get started building that storage ASAP!

    • solarguy 3 years ago

      Agreed, 450GWh in fact, that’s if Blaker’s was accounting for EV’s too!

  11. juxx0r 3 years ago

    I love it how future duck still has midnight hotwater. Also love it how price incentives isn’t a possible solution.

  12. Robert Westinghouse 3 years ago

    Some good points…BUT. This could be a veiled attempt to take control of people’s PV who have spent their own money in the name of “safety” – to continue to shackle the common person to the power companies. …. Call me cynical, but if the government can corporatise it (making money for themselves and their mates) they will…Instead of democratising PV the government will control it…Say NO, micro-grids, regional-grids and get batteries. “Power” to the people NOT the power companies.

  13. Cooma Doug 3 years ago

    The way the market deals with too much energy is a negative price. If we were exposed to this price signal we would not deliver energy at minus 10 dollars a KWhr.
    From my view, if working for Origin or AGL, I would go into the lab for a few days and come up with a solution to the problem, cheap and effective.
    I believe we can eliminate power swings on the grid and control the system frequency by taking action on the load side of every meter. We can measure the frequency at each load centre and adjust feed in and battery function in milli second time.
    This action will eliminate system power swings and effectively split the system into what is a whole array of small grids.
    This will empower the retailers to manage and sell these products and retain the grid.
    That is all good until 2040, we look further down the track, with the addition of 100KWhr cars into this cluster of abundant energy, the poles and wires and the bill we get every three months are going to look really ugly.

    When I look at my situation, the sun hits my house with at least 20 times the energy I need. The tools to capture it and manage it will soon be too cheap to ignore.

    • hydrophilia 3 years ago

      Amen! Give us some good solid price signals! PV and behind-meter storage can react very fast to these.

      • hydrophilia 3 years ago

        Of course, hackers might be able to crash the grid by sending signals and creating interesting effects… but I would think “reasonableness” might be a fairly simple thing to program: perhaps “stay within certain voltage levels and frequency”?

  14. Greenfanatic 3 years ago

    Its just a fare mongering. She is only highlighting the problem domain. What will be the total hours in a year in which distributed PV will exceed demand ? What will be load characteristics including electric vehicle ? Will the generator configuration will be the same ? What about the projection of home battery installation? The research has been going on to keep all the generator behind a converter . Does AEMO has any defined policy to increase the system strength of the grid ? How does it work : more condenser or pump hydro ? Micro-grid application is one of the possible solution to such rooftop PV integration and a lot of research is going on to provide tailored solution. A DC micro-grid in parts of the network could be a potential solution.We still do not know how the electricity grid will look like in a coming decade.

  15. Ian 3 years ago

    Their answer is staring them in the face: incentivise behind the meter storage. With a $1.4 billion war chest this should go a long way to clearing their duck curve problem. The behaviour of distributed generators with storage is this: they will store their excess solar output for the evening load- no fancy grid juggling needed.

    As a little illustration of the subsidy spend:

    Dividing the $ 1.4 billion over 5 years and expecting battery price reductions of 10% over this period . Spend 40% in the first year 30% in the second 20% in the third and 10% in the fourth. Likewise subsidise 40% of the cost in the first , 30% in the second, 20% in the third, 10% in the fourth,
    nothing in the fifth:

    Year of scheme. Unsubsidised cost. Subsidised cost. Max installs from subsidy
    $/KWH $/KWH. GWH
    1. 1000. .600. 1.4
    2. 900. 630. 1.55
    3. 810. 648. 1.7
    4. 730. 657. 1.9
    5. 657. 657. Self supporting industry!

    Come up with your own variables and see how they pan out!

    Here’s another: $1.4 billion over 5 years evenly divided spend, battery price reductions $100 a year. Subsidised cost $500/KWH every year of the scheme:$280 million to spend each year:

    1. 1000. 500 0.56
    2. 900. 500. 0.70
    3. 800. 500. 0.97
    4. 700. 500. 1.4
    5. 600. 500. 2.8
    6. Self supporting

    • Mark Roest 3 years ago

      Or, start in 2020 at US$100/kWh battery price. My visual approximation of squaring the curve in the Rooftop Solar chart at the top is 2.5 GWh of storage potential, or 2,500 MWh. Or, 2,500,000 kWh x $100 = US$250,000,000 — only 14.64% of $1.4 billion! Put up US$100M now and we’ll not only complete battery development in a hurry, we’ll put up a factory in Australia to first saturate the nation for stationary, and then power the cars that can be made if you come up with another few hundred million dollars, and will run probably 300 miles on a battery charge, and sell for US$15k to US$18k in volume production. A friend has the tooling in a warehouse. And you still have a big chunk of $1.4 billion to subsidize the cars for low-income communities and individuals getting together to share a car for carpooling (it seats 9 thin people or 6 overweight ones).
      It also has long-travel suspension for traveling bad to non-existent roads, and lots of protection in crashes. Oh, and no need for lithium, cobalt, nickel or rare earth minerals; don’t use them. Just cheap forms of dirt.

      • Ian 3 years ago

        That’s it Mark, get the installed cost of reliable and safe batteries down to those sorts of levels and a small subsidy will help to get the market moving. Currently LG resu and Tesla powerwall lead the brands available , That’s where the Au$1000/KWH figure is guesstimated from. The actual installation cost figure that will trigger mass adoption of home battery storage in this country is probably less than $500/KWH. But, as you say , provide a market by using a subsidy and very quickly the positive supply/demand dynamics should occur. If you have a good battery product suitable for our needs then you need to convince our government structure. The way to do that is either introduce a finished product into our market like the major players are trying to do, or meet with our authorities with a sizeable sample for a decent trial. We have some nice universities that would love a 1MWH battery sample that you could give them to test out for themselves

        • dhm60 3 years ago

          DER + DESS = obvious solution.
          The only things holding it back are the politics of vested interest and the lobbying power of the big generators. Paying a subsidy to renewables will amp up political opposition from the ideologues and the shock jocks and the whole idiotic energy war will carry on.

    • solarguy 3 years ago

      Behind the meter storage will help the duck curve problem for sure and that makes sense. However, after being in the solar industry myself for the last ten years, rebates have been a good and a bad thing. In the industry we call it the solar coaster, booming business one minute, bust the next. Rebates have brought out a lot of fly by night start up companies in the past, leaving disasters in their wake, customers ripped off bigtime, companies going broke, which gives rise to warranties becoming useless…………………and the list goes on and I could go on for hours about doggy installs, because subbies getting paid peanuts, so not giving a damn.

      Installation of batteries has to be done correctly or it becomes a very big problem. That’s my concern with subsidies!

  16. Ian 3 years ago

    Looking at the duck curve for South Australia by 2023 there seems to be a daytime dip of 400MW compared with current demand curve, taking the hours of power generation as about 6 and the area of the bell curve representing 2/3 maximum dip. In the next 5 years SA will need about 400 x 2/3 x 6 = 1.6GWH of behind the meter storage. That is 1.6/5 = 320MWH per year current cost of storage is about $1000/KWH, so to really encourage uptake of home battery storage provide a subsidy to reduce the cost of batteries to $500/KWH: $160 million for the first year. The cost reduction would probably be around $100/year for home battery systems so the subsidy would cost less by $32 million every year. Not a very expensive scheme to ward off this duck curve thing now is it.

  17. Farmer Dave 3 years ago

    I understand the concern. If a grid was mainly running on rooftop PV and there was a power dip, the way back would be difficult, as all the inverters in the area where the dip occurred would go offline and not come back online until the grid was stable. Getting the grid stable when most of its generation had just dropped out could be challenging. Basically, grid interactive inverters have no black start capability.

    However, some grid interactive inverters do have controllable output. My SMA SMC6000 does. I have an AC coupled all SMA grid backup system, and such a system needs to be able to turn itself down if the grid is not available, the sun is shining, and my demand is less than what the PV system is generating. The SMA gear does this without a separate control signal to the SMC6000, which instead responds to a frequency increase by turning down the power it accepts from the panels. In the grid backup system running in islanded mode, the battery inverted/charger sets the frequency and thus controls the SMC6000 so that it follows the load. At the time I installed the system (2009) I understood that all SMA inverters had this load following feature. Could it be a mandatory feature on grid interactive inverters?

  18. Stewart Rogers 3 years ago

    SAPN will be left with stranded assets. Good game.

  19. Barry Alternative Fact Covfefe 3 years ago

    You get what you give.
    Politicians and the electricity industry gouges customers and avoids new technology and even argues it raises prices. Customers with brains took it upon themselves to reduce their bills in the face of the lies. If the electricity industry embraced solar and didn’t gouge then there would already be far more big solar then small solar and there would not have been the huge incentive and drive that there is toward small solar today.
    Actions, meet consequences.

  20. George Darroch 3 years ago

    If our political and economic masters can’t work out a response to a well-signaled solar trend, then they and we deserve to have our (lack of a) system fall over.

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