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Tesla may drop DC Powerwall 2 option in Australia

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CleanTechnica

According to Ronald Brakels, a longtime CleanTechnica reader and blogger in Adelaide, Australia, the DC version of the Tesla Powerwall 2 will not be offered Down Under. Only the AC version with a built-in inverter will be available and even that will not be offered until sometime later this year, possibly in June.

tesla_powerwall_2

Originally, Tesla’s plan for Australia was to offer an AC Powerwall and a DC Powerwall. Both variants would cost $8,000 and be identical in size, the only difference being that the AC Powerwall would included a built-in inverter, offering customers the greatest flexibility for retrofits, standalone, back-up, or new solar without the need for an external, compatible inverter.

The DC Powerwall was intended for customers who already had an existing compatible inverter and therefore didn’t need an one integrated in their battery pack.

But it seems the company has since decided that the AC Powerwall offers customers the greatest value, flexibility, and ease of installation, regardless of whether or not they already have solar, or what they intend to use the battery for.

Thus, only the AC version of the Powerwall 2 will be offered in Australia, Asia, and Europe. While both the AC and the DC versions will be offered in the North American market — although, that information does not appear to be written in stone.

What’s the big deal? Solar panels generate direct current. The electrical grid runs on alternating current for reasons that date back to the days when Thomas Edison and George Westinghouse were still inventing how electricity would be harnessed to power the world.

Edison was a proponent of DC because at the time there were no AC electric motors. Edison envisioned zero-emissions subways running deep underground, which meant DC motors were the only choice. But DC requires thicker, heavier cables to move electricity over long distances. Under Edison’s plan, generating plants needed to be in the middle of the cities they served.

Westinghouse favored AC because it could be sent over longer distances using thinner wires. Ultimately, Edison won the subway battle but Westinghouse won the distribution war and AC became the standard for electrical grids everywhere.

Now more than a century later, the echoes of those early battles between the two pioneers are still reverberating. Solar systems make DC. Homes run on AC. Inverters are what convert one to the other and back again. Unfortunately, no inverter is 100% efficient, so a tiny bit of electricity is lost every time the conversion is made.

That’s what has modern-day DC fans upset. If DC is coming down from the rooftop solar system and is being converted first to AC for use in the home, and then back to DC to be stored in a battery, and then back to AC later when the stored electricity is used to power the house after the sun goes down, that adds up to a lot of conversions and a lot of tiny losses that soon add up to some pretty significant losses.

The beauty of having both versions of the Powerwall 2 available was that electrical engineers were free to design different systems with different performance characteristics depending on the needs of the individual customer. Now that flexibility will not be available (in Australia, Asia, and Europe), at least not using Tesla equipment.

Why the DC version will still be available in the North American market was not made clear. Nor were we able to confirm the June release date. We will keep you updated as new information comes available.

Source: CleanTechnica. Reproduced with permission.  

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  • solarguy

    For any punters out there considering purchasing a home battery system here are some facts to keep in mind:
    There is no such thing as an AC battery. All batteries are DC! Enphase call their battery an AC battery, but that’s marketing bullshit!
    Each Enphase battery uses a 270w micro inverter, that turns 230v AC into DC voltage to charge the battery and then when it is discharged, the DC voltage is converted back into AC 230v to supply the load. Although Enphase’s battery has a useable capacity of 1.1kwh, it can only supply 270wh. If the grid goes down, so does the battery and PV. NO JOY THERE! There is more that I could say about Enphase’s short comings here, but another time.

    Tesla’s PW2 AC model battery does have an inverter, but it does not have any external DC connections that will allow a PV system to connect directly to it. It can only be connected by way of a string inverter, that the PV system is connected to first and also needs a gateway to manage when it is charged and discharged. Although it has a higher and more useful power delivery than the Enphase battery. It works similar to Enphase’s system, with the exception that it could work to supply power in a blackout, “but not the PV perhaps”, if extra hardware is installed that is compatible. Naturally at extra cost. Round trip efficiency about 85%. And when the battery is exhausted and the grid doesn’t come back on to save the hour, or hours, well bad luck. The eventual price of the Tesla PW2 could turn out to be shock, as the first version did. $8k is only for the battery itself ( but could be more) not including other needed hardware or installation.

    In conclusion, there are systems out there that are DC coupled and will keep the battery charged and allow your PV to be consumed as well if the grid does go down and do it automatically, for an indefinite period, at less cost than the above systems, including installation. NOW THAT’S HAPPY DAYS!

    • Agreed, but it could be done with a compatible inverter and managed AC coupling?

      • solarguy

        Finn, yep correct by the frequency shift method, but there is no guarantee it will not over charge say a GEL LA battery. Although Li-Ion batteries have a BMS, which with a compatible inverter should be no problem. Just adds more complexity and cost. And I don’t think it would work with Enphase.

      • Chris Fraser

        It seems to me, (or for anyone considering a hybrid system) the following services would be a reasonable ask ;-
        a) Grid on. Available PV generation powers household loads, excess charges battery. Excess loads draw some energy from grid. Grid charges battery by 2pm ready for afternoon peak. Battery reduces grid energy for household loads during afternoon peak.
        b) Grid fails. Available PV generation powers household loads, excess PV charges battery. Battery powers essential household loads during evening grid blackout. External generator may be added.Actually this might be a huge list. But can anyone do them ? Could a Selectronic controller do them ?

        • MaxG

          YES, the Selectronic boxes can do that…

          My 20kWh battery is full before 11:00 after a 50% discharge; dangling off 2 x 6kW panels with a 6kW inverter each.
          Feds the battery first, then excess to the grid; power fails or not, we life on the battery 🙂

          And, yes, I have got a SP PRO GO 7.5kWh inverter charger from Selectronic.

          http://www.max.grenkowitz.net/tmp/SharedImages/_MG_0410_00.jpg

      • humanitarian solar

        The AC powerwall 2 is perfect for people like yourself with a previous grid-connect solar system. It enables your solar panels which have been wired in a string suitable for a grid-connect inverter, to be connected directly to the tesla storage solution. The old grid-connect inverter can be thrown away, as Tesla now include a new integrated inverter for “free”. Tesla always designed their system this way, forming a road purpose built to steer customers like yourself into their universe of components. However, it would be unethical to refer new customers without existing grid-connect solar systems to the Tesla universe, as systems become unnecessarily complex and exclusively geared to AC applications. Solar systems designed for the battery to be accessed for wiring DC applications have additional flexibility, simplicity and therefore, better reliability and cost effectiveness. Rural people especially, are best to power things like communications and refrigeration from DC and I’m certain once people get over the game Tesla has played with the market, a mass scale DC appliance industry will evolve to compliment the existing yacht, motorhome and cabin applications. This will enable the second biggest cost component of the solar system, the inverter/charger, to be reduced in size and cost or eliminated for specific applications which can be done exclusively with DC. Simplicity is king in reliability and ultimate best practice and design.

        • Wrong. No solar inverter in the AC PW2. Only a battery inverter.

          • humanitarian solar

            The point stands, its a battery inverter and battery not designed to have its DC accessible, nor does it care for simple DC applications… an unnecessarily complex system.

    • Richard

      Could you name a few systems that you would recommend . I like
      the idea of being as independent as I can from the grid but still keep the umbilical cord. Live in Victoria
      Sounds like the pw2 system has
      a few issues and expensive.

      • Redback Technologies have a good all-in-on hybrid inverter solution. Integrated lithium battery option also available.

      • 小杜 (xiao du)

        Check the energymatters com au forum for suitable hybrid inverters.

      • Jon

        A company called ‘Solar Connected’.

  • wmh

    The other big reason for using AC is that the current in an AC arc goes to zero every half cycle which greatly eases circuit breaker, thermostat and other mechanical switch designs.

    • humanitarian solar

      The disadvantage of using AC solar systems is this means an inverter is needed to convert from DC batteries to AC house wiring and then to convert back to DC with a transformer wall socket or internal device transformer, as most house appliances like TV’s, computers, phones, all run on DC. Yacht and motorhome applications, DC solar systems like those in developing countries, and small solar systems in developed countries, can be extremely simple and cheap, easy to install and find faults. The more complex solar systems are, especially having solar installers assemble gear that wasn’t originally designed to be added, creates extra installation and maintenance costs, as well as reducing reliability with additional gear that can fail. Personally, I like solar systems as they are configured in developing countries, often using simple 12V, 24V and 48V battery banks because an inverter can be a third of the solar system cost and isn’t necessary for the majority of applications. As far as I can see, the ideal battery voltage is a balance between being high enough to route relatively small diameter wire to DC applications like water pumps etc and not too high so arcing is a problem. The brand noark makes DC circuit breakers for DC applications that are run directly off the battery terminals or controlled by inverter load management software.

    • Andy Saunders

      Well, it eases electronic (SCR) switches.

      But the main reason for ACs dominance is that transformers are possible (which then allows efficient long-distance transmission).

      Now, of course, AC motors/drives are available, so there are virtually no solely DC-motor applications left in the power universe.

      • humanitarian solar

        The reason for AC dominance is to facilitate rollout of a grid. This is especially efficient for centralised fossil fuel generators. However solar power can be installed locally, with energy harvest much closer to the point of use. Steering system design towards complexity instead of simplicity, is merely an issue of selfishness, materialism and economic imperialism. There’s also the comfort of what existing tradesman are trained in. The humanitarian orientation looks at what can be done in a way that is accessible for all with the lease environmental waste and doesn’t factor in the gross indulgence of the materialistically inclined.

  • humanitarian solar

    Found the below thread on One Step Off the Grid. Link provided. The issue appears to be the battery voltage locks us into a particular world, whether that is Tesla 400V battery world, 48V battery world, 24V battery world etc, with compatible inverters operating at that specific battery voltage. The PV string voltage also needs to be compatible with the operating range of how the solar system architecture is wired (eg. PV wired to a solar controller or wired into a string inverter). All in all, engineers and their technology and marketing platforms attempt to lock us into their system architecture, like a kind of imperial conquest for world domination of markets. Our first steps taken, determine whose technology universe we have entered.
    https://onestepoffthegrid.com.au/forums/topic/battle-of-the-batteries-and-jailbreaking-the-powerwall/

  • humanitarian solar

    Here is an article demonstrating how the majority of solar power companies in the world use horizontally oriented company approaches to system design, with different manufactures of inverters and batteries cooperating, so the solar installer can mix and match products, tailoring system design specifically to the customers’ needs. Unless households or businesses are certain in anticipating a “standard” install, households and businesses should think carefully before being locked into a system. Different battery chemistries are better in different situations and different inverters are better in different situations.

    http://reneweconomy.com.au/redflow-applauds-grid-approval-victron-inverter-32877/

  • Jon

    Tesla is way too expensive. There are cheaper companies around. I got my battery backup system for $7,100 all up. Tesla’s cheapest is over $10,000.