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Hybrid storage inverters to seal the deal for solar

Matthew Wright
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rsz_solar_panels_side_310_213For many years at Intersolar – the premier trade event of the $100 billion+ solar industry – the excitement has been focussed around the latest panels, their efficiency and cost.
At this year’s trade fair, however, the hustle, bustle and noise was definitely in the three giant aircraft hanger sized halls devoted to a new type of inverter, the grid interactive battery hybrid inverter.
While some interesting panel technology was certainly on offer- including panels in various shapes (triangles, corrugations, ripples and more), some featuring integrated mounting systems, others being flexible, some hybridised with thermal collectors and still more integrated into roofing products, and not to mention the awesome party that Trina put on Wednesday evening – it was the inverters that stole the show.

Almost every company in the inverter space was show-casing a hybrid storage option of some sort and some of the new Chinese and Taiwanese companies had built a business from scratch or moved into this space exclusively to create a storage offering.  There were battery hybrid storage offerings from Czech Republic, China, India, Spain, Germany, USA and Australia to name a few.

Although companies like Germany’s SMA, with their Sunny backup solution, and Australian company Selectronics have been offering grid battery hybrids for many years, high costs have meant that their takeup has been modest mainly for niche applications.

Battery inverters into the mainstream…
This time, though, the Chinese  inverter manufacturers are trying to get ahead of the curve hitting the market with offerings that are around 60-80 per cent cheaper than what SMA or Selectronics have achieved.  The products are developing rapidly and they haven’t yet been properly tested in markets to get customer feedback.  If I was a Chinese inverter manufacturer I’d be looking at Selectronics product and trying to do that cheaper.  Some approaches are too cumbersome with separate battery charge controllers and inverters leading to non-simple solutions.  Across the board functionality is limited with some missing key features.

In all the following feature set seems to be where the hybrid inverters are going and you can expect convergence in this feature set within 12-24 months.

#1 Inverterc can operate synchronised to the grid or indpendent of the grid in Solar UPS (Uninterruptable Power Supply) mode

#2 Inverters have a web based inverface with a timetable that sets it to zero grid export or zero grid import during certain times.  This is especially useful for avoidig daytime peak energy prices.

#3 Inverters can import realtime Meteorological data from a countries Meteorological service and if there will be inadequate solar resource the following day then off peak night tariffs can be used (ie before 7AM in the morning) to fully or partially (depending on how much the solar resource is expected to be reduced) charged.

#4 The Inverter can pass through more power than its rating for normal operation.  This means the entire customers in home circuits can sit protected behind the inverter, which not only provides UPS but maximises self consumption in the simplest way possible. So if it is rated at 6kVA and the customer occassionaly goes over this limit, the inverter will feed the entire requirement from the grid during normal times when the grid is present. (of course if too much power is drawn during a grid outage the inverter will shut itself down to protect itself and will need to be turned on again).

#5 The export capability of the battery hybrid allows for setting a dynamic maximum grid limit.  i.e. Zero grid export (0kVA) means it will provide self consumption only and any deficit will be drawn from the grid.  The units can be fully configurable in 0.1kVA increments up to their rating. So, if an operator such as SP Ausnet in Victoria tries to restrict an inverter to feeding in just 3kVA, then a 6kVA inverter can be set to not export more than 3kVA. But if there is both a 3kVA load present and 6kVA of potential to generate (ie midday) then both the load will be satisfied and the full possible export to the grid.

Finally, the inverter might be IP66 so it can be installed in any weather/ almost any location.  It may be Extra Low Voltage (ELV) so that ticketed (licenced) labour is not required for the solar array DC side and DC optimisers are not required because that capability is inherint in the requirement for only 2 panels in parallel in lower voltage strings.
And the inverters will be setup for oversizing (and supersizing) and explicity warranted as such because with cheap panels it is still even with future reductions in battery cost likely to be cheaper to use the virtual battery of oversizing an array than to use batteries for morning and afternoon demands.  Note: 300% oversizing (inverter : solar ratio) gives 200% of the production so a 30cent a watt panel array in 2017 oversized will have an effective cost of 45cents a watt because one third of potential production will be discarded.
Battery hybrid inverters were the flavour of Intersolar and they’re not going to go away.  It is highly probably that the rooftop market will move exclusively to battery hybrids once the cost of batteries fall to about 50% of where they are today, which is about $400 a kWh (Lead acid) usable (20kWh rated is 10kWh usable to preserve life) and $600/kWh LiOn technologies.
Grid operators and fossil friendly governments may try and stymie solar, but with the new wave of battery hybrids hitting the market at ever lower prices, the horse has already bolted!

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21 responses to “Hybrid storage inverters to seal the deal for solar”

  1. Beat Odermatt Avatar
    Beat Odermatt

    If you travel across Australia, you
    will see a lot of solar installations in motor homes and caravans.
    Many “grey nomads” mange to travel for years and fully depend on
    solar energy and batteries for all their electricity needs. In many
    situations the set-ups are highly sophisticated and provide
    electricity not only for lights, but also for TV, microwave ovens,
    vacuum cleaners etc. Looking at what is already occurring in mobile
    homes and caravans, we may see a secondary 12v type system with
    battery back-up providing power for lights, computers, TV etc.

    1. nakedChimp Avatar
      nakedChimp

      won’t come for households, as to drive any decent load (washing machine, cooktop, etc..) with 12V will require big conductors.
      They either go for something around 48VDC or they up the ante and take the 360VDC (rectified 230VAC)..
      Personally I hope for the 360VDC as there are already big industries working on it (shared development costs):
      1) IT (see 380VDC/400VDC data server developments by several universities and google/etc)
      2) EV (as they currently fast-charge from 3-phase they get the 360VDC which is just 230VAC rectified)

      PS: all the inverters and hybrid inverters I’ve seen so far internally have a distribution bus that runs on 360VDC or more…

      So, yeah.. no 12VDC.

      Whatever voltage comes, it will be decided by the haggling/cuddling of the hybrid inverter and battery system manufacturers.. currently it looks like they go over 230VAC which is bonkers.
      Internally the HESS systems I’ve seen (2kWh+) usually run at 48VDC.

      1. Matthew Wright Avatar
        Matthew Wright

        Actually an ELV inverter still produces 240VAC it just runs at ELV <120VDC ripple free on the solar array side which reduces install costs and allows for DIY solar.

        1. nakedChimp Avatar
          nakedChimp

          DIY solar in AUS is not legal for >250Wp installed, no matter the voltage.

          Check out Richards-Stark Multi Grid.. it’s got 48VDC battery connection and internally (yes, I opened it) it distributes the energy between the several modules over a 360-400VDC bus, and it’s available in Australia (and cheaper than SMA or Selectronics) and just one box instead of 2 or 3.

          Next gen systems that come to market on a broad scale will omit the grid feed option (not the grid back up option though), but implement a parallel output load feature, where you can add hybrid inverters to your load circuits and use the total power..

          1. Matthew Wright Avatar
            Matthew Wright

            This is incorrect.

            http://www.esv.vic.gov.au/Portals/0/Electricity&20Professionals/Files/Guidance notes for electrical installations/Inwww.tstallation Requirments solar installations July 2011.pdf

            (Page 3)
            The following activities are considered to be prescribed electrical installation work;

            Adding panels to an existing solar grid connected PV where the open circuit voltage ( V oc Array) exceeds Extra Low Voltage.

          2. nakedChimp Avatar
            nakedChimp

            Mea culpa.. I remembered this bit wrong (AS-NZS 5033-2012 Installation of Photovoltaic (PV) Arrays) here, that I found again after some searching:
            “PV arrays of less than 240 W and less than 50 V open circuit voltage at Standard Test Condition are not covered by this Standard.”
            Sorry.

          3. Matthew Wright Avatar
            Matthew Wright

            Just because PV arrays above 50V open circuit are covered by the standard does not mean they need a licensed electrician to install. It just means that they require a competent person to install and that person must follow the standard. ELV is still ELV and you do not need to be a licensed electrician. However you do need a licensed electrician to hook up the inverter itself to the 240V in the house and that is proscribed work that needs an inspector.

  2. Neil_Copeland Avatar
    Neil_Copeland

    SA Power Networks has already included a paragraph in the net feed in tariff contract that says all non-retailer feed in will be forfeited if a battery system is added to an existing solar system.

    1. Zvyozdochka Avatar
      Zvyozdochka

      Is that available online anywhere?

      I think we can expect a lot more of this sort of trickery.

      1. nakedChimp Avatar
        nakedChimp

        trickery? all they do is alienate customers..

        1. Warwick Avatar
          Warwick

          It’s hardly trickery, they’re stopping people getting paid for solar energy exports when they could charge up the battery on coal fired electricity and get paid a premium for it. There’s no way to tell the difference between solar energy stored in a battery and coal fired energy.

          1. Matthew Wright Avatar
            Matthew Wright

            A seperate system with a zero feed in inverter should be able to be installed. It’s basically a Solar UPS – since when have UPS (Uninteruptable Power Supplies) been illegal.

          2. nakedChimp Avatar
            nakedChimp

            Ask your local energy distributor about that one.. I tried, with zero export legally binding in a contract thrown in for good measure.
            They let you go stand alone, yes.. that’s what I meant with ‘alienate’.

          3. Matthew Wright Avatar
            Matthew Wright

            An electrician has to do all the LV works which is the 240V part. That’s how it is regulated in Australia.

  3. Beat Odermatt Avatar
    Beat Odermatt

    A low voltage secondary system would not be connected to the grid. It works in many massive motor homes and I can assure you that these people to not give up their comfortable life style. If there is a will, there is a way. By the way, electric cooktops are a thing of the past and are rarely used these days.

    1. eject Avatar
      eject

      They are kind of a big thing in Europe though. But then we do have 240V multiphase electricity. I won’t give up my induction stove for anything. It is just as responsive as gas. Maybe even more so. It is easier to clean and you or children can’t burn themselves.

      1. Miles Harding Avatar
        Miles Harding

        7KW for the hotplate set! Where to put the battery?
        Maybe next to the kitchen so the cooktop an be fed more or less directly.
        Induction cookers are essentially switching power supplies, so it is likely possible to re-engineer them to work from low voltage (say 24 or 48V) so that the battery can supply this load directly. The DC to AC inverter has undergone a revolution with high performance MOSFETs, making the battery voltage largely irrelevant to the efficiency and performance, giving me some confidence that this is not very hard to do.

        1. nakedChimp Avatar
          nakedChimp

          And what do you do with other big loads?
          The voltage drop is not negligible.. so either you keep a high voltage or you install thicker conductors.

  4. jessica chen Avatar
    jessica chen

    We can use inverter Flexibility, now battery inverters become easy to our life, so it will be more and more welcomed by everyone.

  5. Guest Avatar
    Guest

    Any idea if anyone is offering an economic version of hybrid solar in Oz? All the systems I have seen are upwards of $20k

  6. Trevor Thomson Avatar
    Trevor Thomson

    Any idea if anyone is offering an economic version of hybrid solar in Oz? All the systems I have seen are upwards of $20k.

    I’d be interested in a system that was 3-5kW of panels plus 5-10kWh of battery backup. Enough to smooth out the daily load cycle.

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