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Network limits on solar, storage could accelerate “death spiral”

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Newly introduced limits on rooftop solar and battery storage capacities for households are likely to spark innovative solutions that will effectively accelerate the so-called “network death spiral”, according to one of the leading lights in the Australian solar and storage business.

Glen Morris, from SolarQuip and a director of the Australian Storage Council, says the new standards will likely encourage households to “hide” multiple circuits from the grid.

That’s because it will be cheaper to take many appliances and circuits “off the grid” rather than pay extra money to meet network requirements, which limit total solar and storage and inverter sizes to 5kW.

The new standard is a guidance and may or may not be enforced by individual networks, and the solar industry is seeking clarification of exactly where each network sits.

But where it is imposed, says Morris, it will likely encourage households to install UPS systems that take at least part of the house off-grid. And it seems that some networks, such as Ergon and Energex in Queensland, are happy for that partial grid desertion to occur.

 

ups morris

This diagram above roughly explains what is proposed. The area to the right – surrounded by the dotted line – is effectively off grid and operates as a UPS (uninterruptible power supply) system.

Morris says it is an attractive option for those people who think that the only choice is to go off the grid altogether, or who think they have no choice but to pay extra charges to upgrade to a three-phase system.

The pitfalls of going off-grid, and choosing the right equipment and configuration, was highlighted in our story on Wednesday about the problems faced by “off-grid guy” Michael Mobbs with his inner-city system, a story that has sparked vigorous debate about how people should look at off-grid options.

And RenewEconomy contributor and ITK analyst David Leitch also wrote about how the new solar standard would affect homes such as his, and why he faced significant extra costs because of his wish to expand his rooftop solar system from 4kW to more than 6kW.

Morris says there is a middle path.

He suggests installing a separate switchboard which runs much of the appliances in the home, and has its own solar panel, inverter and storage. Some appliances, and the house is still connected to the grid, and when the solar and battery storage on the new switchboard runs out of power, it can still draw from the grid.

Households will pay for the privilege of using the grid as a back-up, with fixed grid costs at around $1.50 a day (more than $500 per annum) in regional NSW, for instance.

The advantage for existing solar households, particularly those still on premium tariffs, is that they can add more solar and storage on a new switchboard and continue to receive those tariffs from the original system.

For those, like Leitch, who want to add solar and storage to an existing system, it means they are not obligated to pay thousands more for an upgrade to a three-phase system.

“I think these new rules will force people towards it, and these systems are not very expensive,” Morris says. The price for UPS inverters are around $1,000 to $2,000 – and for not much outlay people can take part of their houses off grid, he says.

And then, further down the track, if network charges continue to rise and solar and storage costs continue to fall, they can take their whole house off grid.

“This is an engineering decision,” Morris says of the network ruling. “I don’t think they have an agenda here. They are engineers …. but the implications are that it could cause people to slide off the network, a little bit at a time.”

Note: In another development, Morris also warns that the Clean Energy Regulator has made is “very clear” that if households are creating STC’s (renewable energy certificates for rooftop solarby upgrading any solar PV system (even replacing faulty panels) then the whole system needs to be brought up to current standards.

“Even though distribution businesses and state energy safety regulators may not require this, if creating STC’s then you have signed a form stating, “the whole of the system complies with Australian Standards and local regulations”.

That has implications, he says, because some older systems may not have conformed to more recent fire regulations and other standards, and may have to be upgraded to meet those new requirements.

  

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  • Tim Forcey

    I think plenty more people leaving or working toward leaving the gas grid than the electricity grid. Have a look here at “My Efficient Electric Home”, nearing 1,100 members. https://www.facebook.com/groups/996387660405677/

    • Kevan Daly

      I agree; AGL supply my gas and it’s just for hot water and oven/cooktop. The connection charges are higher than the value of the gas I use!

  • Greenradagast

    As a designer, I would never recommend anyone living in suburbia to go off grid. Yet. To be off grid means having a system that wont run out of electricity in the middle of winter. And as most residential houses are nothing like an off grid house (and raley fit anything bigger than 5 kW of PV) because they consume big power, you will need a pretty big system. You also don’t really want a deisel genset to be cutting in in the middle of the night. I would say the best idea is to run essential circuits from solar/battery i.e. fridge and lights etc, and use grid for the rest. Maybe in about 5 years me may be able to get off the grid, but not yet. And I would always want the stability of having a grid.

    • Andrew

      With a bit of planning (eg solar hot water and running heavy draw appliances eg dishwasher, pool filter during the day) not sure why you would need diesel gen cutting in at night, although I don’t use electricity for overnight heating.

      • Greenradagast

        It would if your battery went flat. Winter solar output can be very low, and can be so for a few days at a time. To have a battery big enough to last at 3 days of autonomy (even at 90% DOD), you need a pretty big battery bank, and an even bigger PV array to charge it. Unlikely to be able to install a system that size in metro areas. A 10 kW PV system will give you an average of about 20 kWh in winter in SA. That’s average BTW, and assuming North at 30 degrees pitch (we use 40 for off grid).

        • Andrew

          I accept that, but if you have half way decent management software you should be up to speed on your power status and run the genset at a time that wouldn’t disrupt your sleep.

        • solarguy

          Gee, I wouldn’t think you guys in SA would only get 2 PSH in winter average.

        • Matthew Wright

          40 degrees is not necessarily ideal as 50% of contribution in winter is from diffuse light which is best on a horizontal plane.

      • TweedCAN

        For the past 7 years I have been running a system with Frig, lights, and communications on a battery/invertor system and the other circuits on the grid. The load per day is very predictable and the storage required is manageable. The big advantage is in storms or in the future, during load shedding. I think this will become more of an issue in urban areas at least over the next few years.

    • Kevan Daly

      It’s hard to quantify just how convenient the grid is when you live in inner suburbia.

    • nakedChimp

      Especially with the roof designs that are still being put up on houses.
      It’s insane to waste all this space in such a dumb way.

  • MaxG

    There will come a time when it will be very economical to go off-grid (I believe if you own a house this is already the case).
    I have the grid as back-up for my battery PV system; the minute I do not get a FiT of <=6 Cents I will disconnect. The 6kVA diesel gen set will be less than $2k, presenting an ROI of 4 years… given the bastards they are, I am somewhat disappointed with myself that I give them kWhs to sell to my neighbours for 4-5 times the cost.
    However, on the topic: people are well advised to plan ahead and get the right sized system in the first place. Another alternative is an export-limited inverter/charge like the Selectronic SP PRO GO series, thus avoiding the 3-phase costs, which is better invested in a proper system.

    • solarguy

      Ok if you already have one installed, won’t be allowed for new players, unless the network agrees. That’s what this capper is all about Max.

      • humanitarian solar

        Even though you said they don’t allow the adjustable export control models of hybrid inverters, surely just purchasing the 5kW model overcomes their paranoia about exporting more. So all this is really just a 5kW inverter export limit.

        • solarguy

          Exactly!

      • MaxG

        Had the problem with the disti; after showing a diagram, and the hard-coded of 5kW/h they approved — irrespective of what I had behind the meter (on the load side), as in 12kWp in panels and 2 x 6 kWp inverters… the key issue was no matter what I have in PV, no more than 5kW/h can be exported and no export from the battery either.

        • 5kW/h ? You have an accelerating rate of energy use?

          • MaxG

            ??

          • A Watt is a Joule per second. A kW is 1000 Joules/second. A kW/h is 1000 Joules/second/hour = an accelerating use of energy.

          • OnionMan77

            Finn’s having a lend…. 6kWh/h maybe?

  • trackdaze

    And how would a 12kwhr mits outlander phev or 70+kwhr tesla patch into an invisible switchboard? Could it act as the ups?

    the 5kw rating suggested for storage is peak kw and not kwhr? If so thats ok?

    • humanitarian solar

      See solarguy’s comments for DC coupling. I’m guessing it’s only a 5kW maximum that can be exported at any given time into the grid, so my understanding is it’s merely a 5kW inverter limit. Because people are thinking in terms of their old grid-tie inverters, people seem implicitly concerned that we can therefore only have 5kW of PV because that was approximately all the grid-tie inverter was designed to handle. So there’s perhaps an error, that it’s merely an inverter export limit, so we can have a million MW of PV behind the meter as long as its put into a battery (or an EV) and no more than 5kW is exported into the grid at any time. To do this, we DC couple the PV into the battery. I think there’s two primary methods. With the gear I use the DC path is PV then Solar Controller (has the maximum power point tracker) then battery. The advantage of this method is there’s no limit on the number of MPPT’s that can be used, hence if we have multiple rooftops with different orientation and slope, this is a good method because we need a different MPPT for each. However solarguy also mentions there’s also battery inverters (also called inverter/chargers or hybrid inverters) that have MPPT ports for the PV to connect to without buying the extra Solar Controllers, so all the kit is integrated in one box. Either way, getting the DC into a battery saves a grid-tie inverter putting it straight into the grid and scaring the network. Long description. Here’s a diagram of the method with seperate Solar Controllers. This example also highlights a wind generator can also be fed into the battery in this way. https://uploads.disquscdn.com/images/507b0ef26b35ec31e26b8099a8a013c849732cdb2eadc681a2ca2e05efa6a8cd.jpg

      • nakedChimp

        The only problem I have with this system (besides ridiculous price due to low volume of manufacture, same as Seletronics) is the low DC voltage for the bus between the units..
        Make it 400Vdc and we’re good to go.

        • humanitarian solar

          Their models have a 3000VA that comes in 12V, 24V and 48V and the 5000VA comes in 24V and 48V, probably pretty much the same as Selectronic. The “ridiculous price” is also for a stack of features in there, which appears to be becoming more important with the rules changing as the grid changes.
          They also have a model called a Quattro which manages 2x external AC sources and it comes in 48V for 10,000VA and 15,000VA. The majority of medium to large houses use 48V these days, so there is the greatest choice of solar controllers for battery banks of that size.
          If your thinking of the Powerwall, a problem they may be facing now is Powerwall 2 is AC coupled, so the PV may not be able to be sized above 5kW? Otherwise wouldn’t the 5kW export limit be exceeded? With sun cranking, battery full, load taken care of, I imagine that 5kW of AC coupled panels is going to crank it’s output into the grid maxing out the export limit, so I’m guessing no more than that could be added. I’m guessing this is what grids are trying to combat and put a lid on. The advantage with DC coupling is I reckon no limit on PV or battery size. I guess there will be no more stacking of Powerwalls unless three can be put in three phase and then export 5kW on each phase.

          • Justin

            The MultiGrid 3000VA/35/50 is only $2,200 inc GST. I just bought one. Very cost effective and ALOT cheaper than the Selectronic. The MultiPlus/Quattro are not AS approved.

          • humanitarian solar

            Do you happen to know if the MultiGrid is replacing the MultiPlus because last I heard they were going to make the necessary modifications to the MultiPlus to meet the new compliance rules in Australia?

          • Justin

            No. The multigrid is just an as4777 approved version of the multiplus (with some additional hardware to achieve compliance such as drm hardwire required by the standard). The multiplus will continue to be available for off grid systems typically associated with marine or campers.

          • humanitarian solar

            The great thing about a company who has been designing gear for boat engine rooms (heat) and motorhomes ( vibration) since 1973, is the gear has a tough track record. Why I bought it. It’s also fairly modular so customs designs are the go. Now you’ve given me this info, I’ll put a MUltiGrid 5000VA on the entry to the property and the other buildings I might just put MultiPlus. Can’t have more than one exporting to the grid anyway, so the other two buildings will have to be MultiPlus with charging facility.

          • Justin

            How is this for an idea (see attached)? The Inverter on the Grid side is a standard grid-connect inverter. The Inverter on the UPS side must be a Fronius inverter and the Victron will throttles it up and down to keep to prevent the Victron system from exporting. This way only 5kW will ever be exported.

            https://uploads.disquscdn.com/images/5640a47cf38bffd900772147d18fda520f6fe3c71f6e4ab2cb0809aa8841da5e.jpg

          • humanitarian solar

            I haven’t read up on AC coupling the Victron with the different “self consumption hubs” on the Victron site. I take it you have a 5kW legacy grid-tie inverter your trying to work around? Why not just ditch the grid-tie inverter and feed the 5kW of solar directly into a solar controller? Advantage of that is if the grid goes down, the solar controller will still be powered up and supplying the battery, otherwise your uptime in a grid outage could be reduced without extensive generator run times. Or maybe just upgrade to the solar controller when the grid-tie inverter dies or when you need to upgrade the PV beyond the 5kW limit.

          • Justin

            The self consumption hubs have all been deprecated in favour of ESS. In the unlikely event I lose grid I will still have a 5kw solar inverter + a 5kw inverter from the battery and another 2kw from my Honda EU20i (everything downstream of the Victron)… More than enough to run these loads!!!

            When grid is connected this configuration allows me to have 10kw of solar generating capacity + 5kw of battery (total 15kw!!!) and the grid will only ever see 5kw.

            I’m not trying to work around anything… DC coupling can be a pain in the arse because the string voltages are always lower and therefore higher currents requiring more cabling, fusing, etc etc. It doesn’t suit my goals but it is an expansion path given Victron’s 1.0 Factor rule.

          • humanitarian solar

            Ok thanks will need to read up on ESS. Oh I see, it’s harder getting a solar controller to handle 5KW. My MPPT 150/70 only handles up to 4kW on 48V and the currents would be high.

          • humanitarian solar

            Do you happen to know if the MultiPlus can be upgraded with this new ESS firmware?

          • Justin

            Depends on which Multiplus generation you have and the microprocessor. You also need the Colour Control GX

          • humanitarian solar

            I’ve got one 18 months old so will check the chip number required. Have the color control. With ESS is it possible to set the threshold the battery stays charged at? In the old self consumption hub 1 it was fixed at 50%. I just have lead acid and don’t want it going below 70% unless there is a grid outage. Hub 1 called this 50% threshold “sustain mode”.

          • Justin

            Yes; you can set to different discharge levels (eg set it down to 20% while on grid); but let it go down to say 50% if you you have lost grid. All covered in the ESS Manual 😉

          • humanitarian solar

            Awesome! Thanks!

          • humanitarian solar

            Mate looking back through my email, I notice you’ve said something about giving advice and doing my research. This is a discussion group. I was merely discussing not giving you advice. Giving you advice would be me taking a consultative role and charging you, which would involve you giving me prior consent. I never claimed to be a solar installer and so I only do comprehensive research on what I need to know. With my comments on your property, you asked and I was responding out of kindness, interest and a spirit of learning. I trained as an electronics technician almost three decades ago and retrained with another three degrees so no longer work in the electronics field nor do I engage in significant research in electronics. I’m on this site because I have some interest in renewable energy.

          • Justin

            Lols… Do as much research about Victron products, ESS, relevant Standards, design configurations and my requirements and then you might be in a better position to provide proper advice.

            By reconfiguring one of the 5kw grid ties to a solar DC charge as you suggest reduces the total AC capacity of the system (as you are now relying on the Victron Multi to provide the AC capacity). Not to mention that reconfiguring a grid connect solar string to a DC solar charger is a lot of work due to the much lower string voltages and higher current.

            If the grid does go down, I have the 5kw inverter + 5kw battery inverter + 2kw Honda EU20i = plenty for the house loads! When grid is up there is 10kw of solar AC + 5kw of battery with the grid only ever seeing 5kw export.

  • John Goss

    For those who are wanting to charge their electric car at home, is it necessary and/or helpful for those households to install a 3 phase system?

    • Tim Forcey

      Hi John, if you can access Facebook, we discuss this sort of thing at My Efficient Electric Home. https://www.facebook.com/groups/996387660405677/

    • Nah

    • Justin

      No. 15A single phase power outlet will fill most EVs overnight… A Tesla has a huge battery and will get about 300kms of charge per 12 hr night.

  • Jason Van Der Velden

    Who is responsible for this (bribery) decision?

  • solarguy

    Glen’s idea is a good one, it’s cheap and effective. The hard part will be choosing which loads to hide and of course there won’t be any extra FIT to help lower the SAC charges further.
    Look there are more than one way to skin a cat and if you loads don’t exceed 5kw or can be managed so it doesn’t go over 5kw, just add more PV to a DC coupled hybrid inverter.

  • Joe

    Hi Max. Regarding FiT have a look at Diamond Energy if available in your area. If just become aware that they have a base rate of 8.0 cents and a scheme called WattBank25 where they pay 15.0 cents for the first 1300kWh exported each year for 3 years.

    • solarguy

      What are SAC charges?

      • Joe

        104.48cents per day inclusive of GST. A carrot of 3% discount is dangled if you pay by direct debit

      • solarguy

        Service and availability.

    • MaxG

      I am with Energy Locals at 11 Cents per kWh exported 🙂
      Supply charge $1.10/day and 27Cents per kWh imported — since I need less than 200kWh per year this is no issue.

  • Ken Dyer

    I am in the enviable position (some might say unenviable) of about to build a house. My solar PV and battery setup will be a greenfield investment. I also have three phase power giving me unlimited access to solar PV. I am also exploring the Sonnen battery and community battery power arrangement.

    https://www.sonnen.com.au/en-au/

    The Sonnen community provides independence and power sharing. It has been a success in Germany. Australia has now reached approximately 400 Sonnen installations, and at it present rate of growth, will reach the 2000 mark shortly, which will then trigger the start of the Sonnen battery power sharing community.

    No doubt, there are similar systems being developed that will quickly overcome limitations. I for one am looking forward to the Sonnen system really taking off in Australia.

  • Yasea

    Would keeping the heavy loads on the grid, like the kitchen and laundry for example, that often run in the peak hours, make the duck curve just worse and the grid less stable? People would mostly move appliances that mostly need base load on a separate (off grid) system I assume.

  • Rod

    I set up my own microgrid today!
    Refreshing a rental for a Month or so. I need a bit of power for tools and lights and a cuppa. Was going to cost $38 each to connect and disconnect power plus daily charge plus power.
    So, I threw a cable next door with a Power Usage Monitor (very accurate) and offered him 60c kWh (He’s on PFiT too). Sorted.
    But seriously this could be an option for efficient households during low solar times.

    • Mike Shackleton

      Our recently completed 12 unit apartment block has solar panels (1.25 kW per unit) plus a set of panels for the common area/stacker. We all run our own meters and connections to the grid. If we pooled our panels, invested in some storage, we could reduce our electricity costs right down by only having 1 grid connection for the whole block. That would be a saving of about $4000 a year shared across all the units. Of course, such a system relies on everyone being a little conscious of their consumption.

      • humanitarian solar

        I think it would also rely on the body corporate or whatever the legal structure is, to recover the individually metered costs from each unit + the share of the fixed charges, each 3 months it gets a bill. But I’m planning something like that with a project I’m doing. One connection with between 3 and 5 dwellings. I’m definitely not paying for any additional consumer mains. Can’t see why I should be made to.

      • Rod

        Makes sense to me.
        Just don’t all use your toasters at the same time!

  • Michael Dufty

    I think the limit for single phase inverter on a 3 phase system is 3kW in WA. Maybe they will increase it to 5 now? I’m guessing garden bores are not so popular in other parts of Australia, there are lots of 3 phase households in Perth due to the bore pumps.

    • it’s already 5kW, Mike
      Plus you could oversize, or lobby for a larger system with grid limiting!

      • humanitarian solar

        Solarguy is saying the grid limiting features of some inverters will be unacceptable. Need clear rules documented.

        • who tf is Solarguy?

          • humanitarian solar

            Person commenting in the discussion. Installer. I think we all need to work together to work this out. These network fuckers are attacking the solar industry.

          • yes! they’re definitely not helping any of us

          • humanitarian solar

            I agree with solarguy’s analysis of the problem and he “appears” to be familiar with the proposed rule changes. If you have a different rationale for a system configuration, then critique others and table yours..

          • can solarguy (aka humanitarian solar) please provide some links to these ‘proposed’ rule changes… (you say proposed, yet you have been claiming they are already in place, and new???)

          • humanitarian solar

            I don’t know which is why I’m calling them “mysterious”. I’m merely responding to the article here by Giles, the discussion and another article by David Leitch, which hasn’t much more information than this one.
            http://reneweconomy.com.au/how-the-new-solar-standard-will-affect-households-like-mine-58494/

          • Justin

            What’s your email address; i can send you the relevant australian standard with highlighted sections including the publishing date and effect date (which is 1/4/17)

          • Hi Justin. No please, post the highlighted sections here and share with everyone. What standard is it?

          • Justin
          • humanitarian solar

            Sense of humour.

        • Many inverters are approved by the DNSPs for grid limiting

          • humanitarian solar

            I’ve already said many times, solarguy is saying the new changes tabled are more serious about limiting inverters to 5kW, including not allowing features such as adjustable export control. The problem is, we don’t have these mysterious new rules in front of us.

      • Michael Dufty

        I’ve had two systems installed, 2kW and 5kw, in both cases I was told I needed to have a 3 phase inverter. Bad advice from installer, or have they changed the rules, or is it actually a good idea regardless of rules? A different topic to the main discussion really though, as I already had 3 phase power.

        • If you have 3 phase power connected to your home, then a 3 phase inverter is ideal. While you could technically install a single phase inverter, it would only cater for 1/3 of your load (assuming it is balanced across all three phases)

          so you have 2 x 3 phase inverters currently? the WA DNSP limit is 5kW per phase.. so for a three phase system you could install as much as 15kW

          • Oops, sorry, I originally misread your first comment, and my first reply was incorrect. Definitely 5kW per phase for Western Power

        • Alan

          Western Power will typically allow up to a 3kW single phase inverter on a 3 phase connection so a single phase inverter is fine for 2kW but a 3 phase inverter is needed for 5kW. Meters measure the total net power (not per phase) so a single phase inverter will contribute to loads across all 3 phases.

  • humanitarian solar

    I haven’t read the new rules, though I imagine we can have a million megawatts of PV and not break the rules, as long as we put it in a battery or an EV and don’t go exporting it and scaring the grid with it. So I think it’s only a 5KW export limit and nothing more, because it’s no one else’s business what I do behind the meter.

  • humanitarian solar

    This equipment diagram might be easier for us to work from. If we cross out the word “generator” and substitute “grid” this equipment diagram suits our purposes. The “Multiplus” is a hybrid inverter. Notice in this diagram, there’s DC coupling, where the DC from the solar panels go into a solar controller (solar regulator) then into the battery. The battery also connects to the hybrid inverter because the inverter sources DC from our battery. That’s the DC part of this diagram. In contrast to the diagram above, if we look at this hybrid inverter, it has two horizontal lines connected to other equipment. The LHS line connects to the diesel generator or grid. This is called the “external AC input” where the hybrid inverter sources additional AC if our property doesn’t have enough. The RHS line from the hybrid inverter is here called the “AC out” and this goes to all the circuit breakers for our house lights, power, hot water booster, air con etc. In terms of the new rules, the important thing I think, is the hybrid inverter must now be a maximum rating of 5kW, so network operators feel comfortable no more than 5kW will ever be exported out of the LHS of the hybrid inverter, back through the connection called the “external AC input”. So it doesn’t matter how much PV we add to our system when we use “DC coupling”, the grid doesn’t get scared because our hybrid inverter now has a 5kW export limit. https://uploads.disquscdn.com/images/685f934b91c01e50c1998c90a12db1bae042be1af6fa8e2a8a04a290fc871dd1.jpg

    • Justin

      Except the Multiplus is not AS4777 approved. You will need the MultiGrid and it is currently only available in 3kva but 5kva model won’t be far away. I’ve just purchased a Multigrid 3000 and about to AC-Couple it to a Fronius. I will be wiring it up as per this article (and I have no intention of asking the DNSP for permission as it is load only and zero export as far as the grid is concerned)….

      • humanitarian solar

        What’s the purpose for doing an AC couple configuration rather than DC couple? I’m concerned AC coupling will limit the solar system to 5kW of inverters. e.g. with the new rules (exceptions in some states) we could no longer AC couple 5kW now then when another roof becomes available, AC couple another 5kW later. That’s my understanding. Though DC coupling doesn’t appear to have this limit.

        • Justin

          Read my other replies to comments where I have attached some as4777 excerpts.

  • Ian

    There is definitely a deficiency in current solar plus storage designs as this article and Michael Mobbs article imply. Solar plus storage is expensive, needs a lot of tweaking and is not very effective in going off grid. People have done the grid tie solar thing with a 5 KW maximum feed in and now want more. We want to maximise our roof space, use solar for heating of pools, hot water and living spaces and for air conditioning, pool filtration pumping and many other functions. We want to be able to island our system as an UPS when the grid does a ‘South Australia’ on us. At this stage, we like being connected to the grid, to export excess energy generation and to have that grid back-up function.

    If the regulations and grid retailers cannot match this trend, then the option of installing a second but off-grid circuit is a good one.

    Here is a possible configuration: 5 to 7KW of solar panels with microinvertors, 2 to 4 KWH of AC battery storage , a system controller of some sort possibly with grid power input, and large loads such as pool filtration, air conditioning, water heating attached to this. The primary function of the battery is for circuit stabilisation, and the “storage function” is largely removed by managing the loads, ie using the energy when it is generated, heating water in the day , pool filtration in the day etc. There are systems where DC pool pumps are attached directly to a MPPV and then solar panels, but an AC circuit with a bit more operational flexibility is desired.

    The Enphase idea of microinvertors, and modular AC batteries has merit as more capacity can be added later on. The question is what sort of system controller can orchestrate panels , battery and loads plus add some grid electricity very occasionally? This system would have very few pretentions of taking the house off-grid but just designed to take the big household loads out of the grid electricity bill, it would, however need to have enough storage to supply just refrigeration and essential medical equipment when there is a grid power failure.

    • humanitarian solar

      The control function is what the hybrid inverter does. And more. Can also see solarguys description of DC coupled systems. The hybrid inverter is the “smarts” in the solar system. If you wish to have the equivalent of micro-inverters because you have trees or are laissez-faire with pruning, you can use DC optimisers instead. If you still want to go with micro-inverters, I don’t know how your going to get around the new rules. Hybrid inverter technology has been around since the mid seventies.

      • Ian

        Thankyou, will look at hybrid inverters. I was talking about a situation where the house already has say 5KW of solar installed in a fully grid-tied situation, all working fine, and perhaps getting a legacy premium FiT, but the household now is wanting to do more , plenty of roof space left, a few large loads , and wanting to maximise the use of the roof space. The rules are no more solar to be exported beyond 5KW, so a second new solar plus storage must be separate from the grid. After all people do this all the time in a very minuscule and limited way. Solar garden lights for instance are a type of second off grid system, noone’s going to ban that sort of set up I hope.

        • humanitarian solar

          solarguy has been describing how to fix this type of situation. The problem with the 5kW of PV grid-tied is that it isn’t on any kind of leash, so there will be times when there’s no load, so the 5kW will go straight into the grid, which is why the grid is now limiting this type of PV. So a solution is take the wires out of the MPPT ports on the grid-tie inverter, throw out the grid-tie inverter, then rewire the PV strings into either a hybrid inverter with integrated MPPT ports or wire them into seperate MPPT solar regulators, then into a battery. I prefer the later option because the number of PV strings can then be unlimited, whereas in the other option hybrid inverters with MPPT ports built into them only have x2. So now there is no longer any PV going into the grid as it’s going into a battery. So now say you want to add another 10kW of PV, wire it the same way, into a solar regulator, into the same battery. Or add another 1000 PV strings if you wish, if the battery you buy is big enough. So now we purchase the 5kW inverter, so the grid is happy no more than 5kW can be inverted and sent down the grid. We connect the positive and negative leads of the inverter to a PV and battery system that is essentially an off grid DC system. So this DC system could be the same power South Australia has if you can fit it on your property, as long as it’s on a leash with the 5kW inverter that functions as your gateway for the power onto the grid. This will reassure the grid and make it happy. You’ll have plenty of PV/battery power to invert into an EV and a 5kW inverter x 10 hours = 50kWhrs into the EV. Though if your running allot of high power AC applications, I get a good quality 5kW inverter and possibly with load management features, so the load can be staggered throughout the solar day. So all this is called “DC coupling” the PV, because the PV is going on the DC side of the 5kW inverter.

        • humanitarian solar

          In contrast, if we look at this circuit diagram, this shows how the Powerwall 2 which is AC coupled, is going to be problematic for doing what you wish to do. Notice how the output of the PV inverter is pointing straight at the grid, and if the battery is full there is nothing to soak up the power, so it will fly out into the grid. Naturally we can’t connect 100kW of PV in this way, because it will be unleashed upon the grid pretty much all the time, because there’s no where else for it to go and I’m not aware the Powerwall is going to turn it off. Not so with DC coupled PV, because if the solar regulator senses a full battery voltage, its going to throttle back the power from the solar panels, so the solar panels will sit there as an open circuit. Thats the worst that can happen. However once we connect the hybrid inverter, if the hybrid inverter senses the battery is full, it will invert up to 5kW and export because that’s the most that it can ever do.
          https://uploads.disquscdn.com/images/6c1d40a12f79a3f16c4c0505603fae00f857bfcb1b9bbc5092212ed53bbe9416.jpg

          • Matthew Wright

            You’re obviously not aware of the grid limiting capability available with modern inverters. Fronius, SolarEdge and Enphase all offer grid limiting capability so if your distributor supports its such as SAPN will, Citipower, Powercor, Ausnet, Essential and the WA grid operators then you can have a bigger rating at home to charge your battery and your electric car while still maximising your 5kW access to the grid.

          • Justin

            That is the crux of the issue. The new Australian Standard does not restrict “limiting export to 5kw”. It is not worded like that. It is worded in a way that says the maximum installed size is 5kw and that 5kw is made up all inverter energy systems. That is why people are suggesting using DC coupling as it isn’t technically an inverter…

          • humanitarian solar

            Legend. Well said.

          • humanitarian solar

            No I am aware of it and promoted the feature 18 months ago in forums on one step off the grid and on this website. The new national rules of the 5kW limit on inverters don’t make exceptions for larger inverters with an adjustable export control feature. So from what others are saying, it’s necessary to get special permission for larger inverters.

    • humanitarian solar

      There’s no major problem with Michael Mobbs system apart from it being earlier generation panels and batteries, in a suburban property, with limited space for panels, while having high ideals of being off grid – with no backup for the battery. Normally the less idealistic would use diesel, gas, wood or if rural put up a wind turbine or a proper shed of solar panels.

    • Don’t waste your roof space on solar thermal for your pool and hot water heating…. that’s where your panels should go! Solar thermal systems often require a gas or electric boost to continue operating throughout the colder months, which are usually very inefficient! Please have a look at heat pumps for these applications. The Sanden in particular is very efficient, and good quality. I’ve done my research.

      Before you commit to a ~7kW system, make sure that it’s enough. Too many people are undersizing there systems and not accounting for the power required to charge their future battery modules. 2 – 4kWh of battery storage would only be suitable for a below average energy user.

      Micro-inverters or DC optimisers are great options for tricky rooftops (with pertial shading issues and with multiple orientations and angles). Most of the time however, a string inverter will do the job!

      • humanitarian solar

        Solar thermal is simpler, no mechanical parts, longer warranty and doesn’t eat into the kW output of the inverter, which appears to be becoming more important.

        • That doesn’t make sense… you generating the energy from the sun either way. Heat pumps are a proven technology and like solar thermal they are also eligible for STCs. Please take more time with your responses – words like ‘eat’ and ‘appears’ do not inspire much confidence in your knowledge!

          • humanitarian solar

            A heat pump runs off AC produced by the inverter, so it’s going to reduce the available AC output of the inverter. I have chosen my words accurately to reflect the fact I too have not seen official documentation of these new rules that have been tabled.

          • Just replace the roof top real-estate used by the solar thermal pipes or plates with solar modules, and generate enough electricity and more to run the heat pump – which in many cases can be timed to operate during peak solar producing times = near zero run costs.

            Roof surface area is a valuable commodity, and shouldn’t be dedicated to performing only one function, such as hot water heating…

            I’ve heard of cases where the hot water thermal system gets too hot, and has to dump the excess hot water into the gutters on the roof.. what a waste! why not produce a few thousand electrons instead, that can be used for any purpose?

            some heat pumps are also extremely efficient – the Sanden heat pump has a COP of 4.5 – which means only 1kW of electrical input is required to produce 4.5kW of heat energy

          • humanitarian solar

            Heat pumps do sound good for some uses. There’s been vigorous debate, in which I’m not terribly invested, about their merits versus solar thermal. Just saying, my electrician (also does solar installs) reckons heat pumps are especially not good for coastal areas because the salt air corrodes the mechanical components, which only often have a 5 year warranty compared to solar thermal I think having longer. Just adding perspectives of others.

          • solarguy

            No that’s COP of 4. I did my research!

          • hmm, not sure where you’re getting that. The product specs definitely say COP of 4.5 https://uploads.disquscdn.com/images/7cfd42fbc01afbbf880406d92fc4130d984e8dc0759f5e5d46fad5efe91e130a.png

          • solarguy

            Full of yourself aren’t you, ya snipe.

      • solarguy

        “Don’t waste your roof with solar thermal” what a joke, so you propose to waste 9.75sqm on powering a heat pump (dedicated 1.5 kw) over other loads, when 4sqm of Evac Tube solar thermal will give plenty of hot water even on cloudy days when PV dips down to a level that can’t run the 1 kw compressor on it’s own.

        You will need plenty of sunny days in winter for that idea to come close to being acceptable. My ET SHW system only had to be boosted 8 days the whole of 2016, using less than 40kwh. Where is your HP would draw shit loads from the grid over the year genius
        .
        Right at this moment at 2.50pm my SHW tank temp is 77 c at the top and 69 c at the bottom after 4 showers last night and we have had only 2hrs of full sun.

        You would also be the kind of genius who would design an off grid system with a heat pump.

        Last point, NO BODY LOVES A SMART ARSE!

        • Alastair Leith

          Interesting numbers, but BZE Buildings Plan was recommending the same for most locations around Australia. Confined roof area to full sun being one obvious edge case where evacuated tubes take the lead over PV only + HP. Heat Pumps don’t operate at full power for long periods of time, they do go to full power to get compression up from ‘off’ and then tend to sit back and pump it around.

  • Macabre

    Fascinating article and BTL discussion. Thanks Giles and commenters.

  • nakedChimp

    Run the network into an inverter and create a isolated house grid afterwards should be the answer, not splitting up your house-hold-grid.

    The quality of the power from the grid is bad anyway – if you ever had a look at it with all those PFC loads attached, which essentially ‘cut off the top and bottoms of the sinus mountains’.

    Treat the grid like any other source of power (pv, battery, generator, etc.) and even convert it a little..

    The problem with that approach?!

    No off-the-shelf devices yet that can do this.
    5-10kW continuous, 15kW peak, 230Vac 50Hz, grid independent, fed by whatever source you have (mains, solar, battery, etc.) with your very own local merit order to power you local house grid.

    No need to install costly switchovers or additional local-power-boards or what have you.
    That device would just sit between your switchboard and the meter and also have connections to solar, the battery, etc..
    End of story.

    Why is no one offering such a device yet?
    It’s not rocket science.

    • humanitarian solar

      What’s wrong with a normal hybrid inverter? They can be purchased with a variety of grid interaction features, load management and load shedding. Solarguy has said the new rules mean no more than a 5kW hybrid inverter, because he reckons the rules prohibit higher KW hybrid inverters with the feature Electronic call “adjustable export control”. Seems to be a trust issue, that we might install a higher kW output inverter and set it at 5kW exports, then later reprogram it for a higher amount above 5kW exports. If this is all a correct interpretation of the rules, I think this is a human rights violation, because the network is being prescriptive with equipment behind the meter, when some people genuinely need a hybrid inverter to produce greater than 5kW onsite. This is the usefulness of say purchasing say Selectronics 7.5kW model for onsite use – house and EV and using the “adjustable export control” feature to limit exports to 5kW. In summary then, if we have all interpreted the rules correctly, it appears the best solution is:
      1) buy a 5kW hybrid inverter (maximum allowable),
      2) look for a range of features creating options for grid interaction and onsite load management and load shedding – to cope with rule changes as the grid evolves,
      3) DC coupling has increased in importance (getting the DC from the PV straight into a battery). In theory, as far as I can see, this enables us to have unlimited storage and PV filling it behind the meter, as long as it only connects to the grid with a hybrid inverter capable of a maximum of 5kW of exports,
      4) I personally favour hybrid inverters where we need to buy seperate solar controllers (solar regulators, MPPT’s) as this means there’s no limit to the number of PV strings that can be fed to a battery. Though if people are confident they have a maximum of two rooftops with different tilt or orientation, they could potentially buy a cheaper device, that integrates the hybrid inverter with 2x MPPT ports on it. Although the other problem with this approach, is the MPPT ports are likely to have a maximum of PV kWatts that can be fed into each MPPT port, though buying seperate solar controllers enable us to purchase exactly what we need for each PV string,
      5) I think a 5kW limit on exports, and therefore also limiting AC coupling configurations, swings us increasingly towards DC coupled solar systems and perhaps also DC applications. A grid can’t control how much DC we use, though our hybrid inverter apparently now has a 5kW limit on producing AC. I wonder how this will effect charging EV’s with AC. I think Tesla has a problem because the Powerwall 2 is AC coupled and with a 5kW export limit, I assume the device can no longer be stacked to double and triple output power,
      6) I think solar systems on different buildings can be connected together on a single property by using hybrid inverters that can manage 2x external AC outputs like Victron’s Quattro model. This feature has historically been used for managing: grid + diesel generator (weak grids), grid + wind, wind + diesel etc,
      7) With rules changing constantly, I also favour a hybrid inverter that is purchase separately to the battery storage (sorry Tesla) so we can evaluate new battery chemistries as new products come to market.

    • Pedro

      Have you had a look at some of the Hybrid inverters on offer. Selectronic comes pretty close to doing what you want followed by Sunny island.

  • Here are the current Distribution Network Service Provider (NDSP) limitations:
    VIC Ausnet Services – 4.6kW limit on modules
    VIC CitiPower – 5kW limit on inverter
    VIC Jemena – 10kW limit on inverter
    VIC Powercor – 5kW limit on inverter
    VIC United Energy – 10kW limit on inverter
    SA SAPN – 10kW limit on the modules
    NSW Ausgrid – not sure!
    NSW Endeaour Energy – 5kW limit on inverter
    NSW Essential Energy – not sure!
    ACT ActewAGL – 10kW limit on inverter (to be confirmed)
    QLD Energex – not sure!
    QLD Ergon Energy – not sure!
    WA Western Power – 5kW limit on inverter

    Where possible, you can also oversize your inverter – which is an extremely good idea! So long as you do not exceed a 1:1.333 inverter:module ration (to retain STC subsidty eligible). This means you can install more than 5kW modules on a 5kW inverter limit. For example:
    5kW inverter with 6.48kW of modules
    8.2kW inverter with 10.8kW of modules

    We have also been successful in installing systems greater than the DNSP limitation, through the use of grid limiting, and approved smart meters. for example, Powercor have approved the Fronius Smart Meter as a grid limiting meter, allowing the installation of much larger systems, so long as exports are limited to 5kW – which is what the smart meter does.

    In short, while you are paying a premium for your grid connection as a backup power source, you are still able to install large systems for the purposes of primarily – offsetting your usage, secondly – allowing for future battery storage charging, and thirdly – exporting back to the grid.

    I’m really not sure why a UPS is required at all? Feels like alot of unnecessary hardware. Why complicate things? If you really want to go off-grid, look at something like a smart inverter like this –
    Selectronics: http://www.selectronic.com.au/sppro/. The Tesla battery packs should also come with islanding mode in the future which means they can operate without the grid anyway

    People need to be patient for battery prices to drop (and they will!) While the Tesla PowerWall 2 (with in-built AC inverter) has a decent capacity of 13.2kWh, it is still very expensive and not economical ~$13,000. We highly recommend installing a large Solar PV system now, while the subsidy’s are around, and adding batteries later when prices reduce!

    • humanitarian solar

      The limits with PV were probably set for grid-tie inverters and couldn’t possibly apply to PV being fed into batteries. One point of the discussion is the authors are pointing to a new universal 5kW limit on inverter exports and solarguy has claimed the new rules prohibit using a larger hybrid inverter with an “adjustable export control” feature (possibly network paranoia it might be changed later). So to solarguy and myself at least, that means DC coupled systems are the way to go, because in my mind that means unlimited PV and unlimited battery storage. So yes I agree, a Selectronic hybrid inverter is a good option, although if what solarguy is saying is right about not allowing larger inverters with like what Selectronic calls the “adjustable export control”, then that brings it back to purchasing the 5kW model. It’s pretty hard working it all out, because the exact technical detail about the rule changes hasn’t been provided and solarguy seems to have read it and I haven’t seen it. Though I’d like to. With your suggestion about Tesla Powerwall, its currently an AC coupled system so I reckon that might give limits on PV size that can be connected.

      • Yes, you and solarguy appear to be good mates. I’ve been reading your comments.. Lots of ‘probablys’ and ‘guessings’ and ‘perhaps’ and ‘pretty hard working it all out’. I think I’ll wait for something more official before discounting what I know to be true

        • humanitarian solar

          Fair enough.

        • solarguy

          No guessing on my part Bassi. 4777.1 states that from 1/4/17 no grid connected inverter, over 5kw can be installed on a single phase. Over 5kw it must be a 3 phase inverter. Simple.
          What you knew is no longer. Perhaps you think David Leitch, Giles and Glen Morris have also got things wrong too..
          The

          • That’s sad news. Could you please point me to the clause number of AS 4777.1 that states this

          • solarguy

            clause 2.3

          • You said “4777.1 states that from 1/4/17…” Where did you get this date from?

            “Unless specifically stated by the electricity distributor, the rating limit for a single-phase
            IES in an individual installation shall be equal to 5 kVA, and a multi-phase IES shall have a
            balanced output with respect to its rating with a tolerance of no greater than 5 kVA
            unbalance between any phases.”

            I think the key thing there is “stated by the electricity distributor” in which case, the limits are as I first posted. Please correct me if I’m wrong!

          • solarguy

            Your not wrong for the most part, but here is the kicker,” unless specifically stated by the distributor”.
            First you have to apply to the distributor to go over 5kva and in areas were there is a high penetration of solar the chances of getting the ok are remote aren’t they!

          • humanitarian solar

            With my military background, I betted you’d get it right because with you mentioning in the past your father was a sergeant major, I knew the consequences of getting things wrong would be too great!!!

  • solarguy

    APOLOGY!
    I stated yesterday that STC’s are claimable up to the oversize limit of +33% and that if you oversize PV above that amount you just won’t get paid the extra. THIS was a misunderstanding on my part and I’m sorry for giving everyone the wrong information.
    The fact is, as has come to my attention, that if you oversize past +33% NO STC’s for the system will be claimable at all.

    • humanitarian solar

      Ha that turned out to be overly optimistic.

      • solarguy

        When I was talking to a colleague months ago about this matter I misunderstood what he said or so he says now, perhaps I did? Anyway, I own the cock up simple as that. I’m not the first to make a cock up and I’m certain I won’t be the last to do so.

        I felt compelled to make an apology as it is the right thing to do and that’s what I’m about anyway. As I have said before, the truth matters!

        • humanitarian solar

          We’re all working it out. Interpreting rules. This diagram above is quite artistic. Should try being part of groupwork in social welfare. That’s really working it out on the go. Cathartic emotions even participants attacking each other on occasions.

          • solarguy

            Well that’s why they invented shot guns, isn’t it LOL

    • Glen Morris

      The “Silly” CEC oversizing rule only applies to GC system WITHOUT batteries. No limit if batteries included.

      • solarguy

        Wow man that’s confusing. I contacted the CER about this before I posted the apology and they told me I was wrong about oversizing over +33% even for an off grid system.
        So Glen are your saying that I was correct in the first place being able to claim STC’s even if an off grid or GC hybrid system is over +33%?

        • Glen Morris

          The CER often give variable advice. What really matters is that your STC aggregator is happy with your system configuration and sizing.

          • solarguy

            And I thought I was confused before, No need to mention any names, but have you known any one who installed a GC Hybrid system or off grid system, gone over + 33%, say 100% and claimed and were paid full STC’s on that basis? e.g 5kw inverter with 10kw PV?

  • humanitarian solar

    HOW TO HAVE 100kW SOLAR SYSTEM AND 100kW OF STORAGE:
    Buy 100kW of PV and wire it through the appropriate sized solar regulators then into the 100kW of battery. This is an off grid DC solar system. If the battery happened to be 24V we could power a 24V fridge with it or whatever we wanted to. So it’s sitting there on our property by itself and no one can complain about it.

    Meanwhile the grid has complained and now it only ever wants a maximum of 5kW of AC exported to it. To make the grid happy, we buy a 5kW hybrid inverter because we know it will only ever produce a maximum of the 5kW and if we’re using some of that 5kW, then there’s even less to export to the grid. So as far as the grid is concerned, all it ever sees is somewhere between zero and 5kW of exports flying out of our property and it can live with that.

    So now we wish to setup our AC, so we connect the positive and negative leads of the 5kW hybrid inverter to our 100kW battery being fed by our 100kW of PV. With this kind of power, there’s plenty to run our property, plenty to charge an EV and apart from when we’re using the inverter ourselves, it will probably be exporting all day. We’ve now setup our solar system so the grid only ever sees a maximum of 5kW of exports, and it’s happy, and we’re happy, we have plenty of onsite power.