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Thread: Solar panels linked to 3 phase ducted AC

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    Default Solar panels linked to 3 phase ducted AC

    Ok, i own a 3 phase ducted air conditioner on my home which draws alot of jiuce in summer and winter, my bill are usually around 1800 Kwh per quarter but can jump over 4000 in summer and winter. i've decided to get 3.5 to 5 kwh solar system to feed my hungry AC, that is link it through a 3 phase inverter ( Fronius 55-V3 ). I work from home so I'll be using the AC in summer during peak periods during the day, I understand during winter I'll only be able to use the AC heater on days with sunshine. As i'm in NSW, i will only get 8c per Kwh feed to the grid so i want to use it ALL while the sun shines

    Just wondering will my 14 - 16 panel - 4 kwh~ system be powerful enough for my AC (6.5 kw cooling) used on and off, and will the panels need to be divide by 3, to feed each phase ?

    My main goal is reduce my electricty bill, not to be green or feed my neighbours fridge.

    Thank you.

    DA.



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    wow you really are confused !

    Firstly the inverter is a poor choice with only 95.9% maximum efficiency , that's maximum so in reality it will be much lower and with only 3.5~4.0kw you won't even see 90% efficiency.
    Let's work on having 4kw of panels , less at least 10% so 3.6Kw system.
    You can bank on 4kwh hrs of production per 1kw of panels =14.4Kwh per day when averaged over the whole year if you have no shade and panels are facing North. , in summer production is higher at about 7kwh per 1Kw of panels so on a perfect day you will see about 25.2Kwh
    You usage is of 4000kwh per quarter = 44.5kwh per day so in reality the solar system you are considering is about half the size you need to cover the costs.

    Heating costs even more to run than Cooling but your production will be much lower at about 2.8kwh per 1kw of panels so your system will only make about 10Kwh per day , on full cloudy day you won't even see that. , so to cover your heating in winter your would need a solar system around 16kw .

    You don't need a 3 phase inverter , the inverter will never directly power your air con , everything being generated will be recorded by your meter , whether you send 10Kwh back into single or 3 phase it's still the same 10kwh .
    Solar panels are DC not any phase , the inverter if 3 phase will convert the output to 3 phase even if all panels are on one single input.

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    Thanks joey,

    i never really expected my system to totally wipeout my bills, just reduce them by half if possible. MY roof isn't that big, i could probably only squeeze 20 Panels on (4 rows of 5 panels) at the most.

    My aircond says 6.5 kw cooling and 5.5 heating so it's actually cheaper to heat, although i don't expect good weather (sunny) when you want the heater.

    Why do you say my inverter will never supply my AC ? that's why i'm getting it. A rep adviced me attaching your solar panels to one phase only means the other 2 phases will draw power from the grid - costing money. He said you should always attach your panels to the line that you use the most, for me, that's my AC & washing machine (during the day)

    Thanks again.

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    Salient points are overlooked.
    The peak hours for the A/C would be 3 PM to 10 PM,
    Heating, 5 AM to Noon.
    Hot water service.
    Cooking.
    Refrigeration.

    You really do need to do a specific case study.



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    Thanks beer4life, i suspect I'd be turning on my AC around 11AM in summer with a westerly blowing, Winter heating probably 7PM - 11PM, Hot water is offpeak solar, Cooking 5 PM, 2 fridges - both large, one new and the other very old (bar fridge)

    All of my lights are either old fluro or new green light bulbs, bathroom has fan that is used after every shower, 2 computers in the house, used from 10 AM - 11 PM, 2 TV's only 1 used - LED with surround sound system. Shed with electric door opener, used about 2-4 times twice a week.

    No pool - no spa - etc, not sure where the power is going. With solar I'd change my habits - only wash clothes during 10 AM - 3 PM, cook maybe at lunch time ? i still think the ducted 3ph AC is the killer, even though i've blocked off rooms etc. If I could get my Solar system to provide during the 10 AM to 3 PM time slot, that would be huge boost .. I hope.

    .

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    Dont forget that with the solar panels you will also be getting a new SMART meter and that itself is another story.
    I am sorry to say I feel that at some future time, they will use those SMART meters to ensure what you generate doesnt benefit you one cent.
    Also I think you may find that your proposed operating times wont help you reduce power usage either.
    Many years ago I had an Oil Heater and at first only turned in on as late in the day as possible and off at night but I found it drank oil like you wouldnt believe to get up to a comfortable temperature and I eventually found it was cheaper to run it basically continuously on Low overnight and then depending on how cold the day was, turn it up accordingly.
    By doing this the house kept an ambient temperature without cooling off as much when the heater was turned off.
    My thoughts are if the house can be cooled before the heat of the day begins, it shouldnt take much to keep it at that level and the same with the Heating.
    Mid winter here in the Central Tablelands it can drop to Minus 10C (25F) and when we get those Sou Westerly's from Antarctica, it feels like minus 100.
    Even after eventually reaching 40C a couple of times this Summer, A/C is still not for me a high priority but what I would be interested in would be to have the ceiling fans run off solar panels directly so the hotter that day, the faster they spin but the panels would NOT be connected to the Grid.
    Last edited by gordon_s1942; 26-01-13 at 11:45 PM.
    I stand unequivicably behind everything I say , I just dont ever remember saying it !!

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    Quote Originally Posted by darkarchon View Post
    Thanks joey,
    Why do you say my inverter will never supply my AC ? that's why i'm getting it. A rep adviced me attaching your solar panels to one phase only means the other 2 phases will draw power from the grid - costing money. He said you should always attach your panels to the line that you use the most, for me, that's my AC & washing machine (during the day)

    Thanks again.
    You will get a new meter when you install solar , it will record imports and exports regardless of how many phases you have . , EG: if your are drawing 4kw and your panels are making 4kw there will be zero import or export recorded regardless of which phase is getting the feed or which phase the loads are on.
    Grid feed inverters are just that , they are designed to feed into the grid not to supply variable loads which is why when the grid goes off ( a blackout ) your PV system also shuts down , they physically need the grid and need to be able to export everything they are making or they shut down , nothing is your house is connected directly to the inverter.
    The grid enables your PV system to work at all, think of the grid as a regulator of power sources , your PV system is a very unreliable and unpredictable one while the grid remains constant.
    Good design of a PV system is where you can use as close to it's production as possible while it's producing during the day ,basically anything you export should be considered waste or power surplus to your needs , but with the system you propose I cant see you will be exported much at all but getting the full benefit of your production as a reduction in what you need to import.

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    So what your saying joey, is that there is no advantage of getting a 3ph inverter ? might as well go quality single phase? (SMA)

    Gordon, sounds mighty chilly on those tablelands .. .. i'm on the coast, different weather, more humidity - heat, coldish winters. Like your idea of a fan, I might install a ceiling fan in the loungeroom, might cut down my AC time.

    .

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    Cool Cooling alternative.

    Quote Originally Posted by darkarchon View Post
    So what your saying joey, is that there is no advantage of getting a 3ph inverter ? might as well go quality single phase? (SMA)

    Gordon, sounds mighty chilly on those tablelands .. .. i'm on the coast, different weather, more humidity - heat, coldish winters. Like your idea of a fan, I might install a ceiling fan in the loungeroom, might cut down my AC time.

    .
    If you're in an isolated location or have a tolerant Council and the roof cannot be seen from the road, paint it WHITE.
    You would be pleasantly ecstatic with how much cooler your house is in the Summer with little change in Winter.



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    Quote Originally Posted by beer4life View Post
    If you're in an isolated location or have a tolerant Council and the roof cannot be seen from the road, paint it WHITE.
    You would be pleasantly ecstatic with how much cooler your house is in the Summer with little change in Winter.


    Sounds wise council but my roof is already cream in colour, isn't that close enough to white ?

    .

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    Quote Originally Posted by darkarchon View Post
    So what your saying joey, is that there is no advantage of getting a 3ph inverter ? might as well go quality single phase? (SMA)

    .
    That's correct mate , any supplier trying to sell you on an old type 3 phase inverter is trying to clear obsolete stock.

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    Quote Originally Posted by darkarchon View Post
    Sounds wise council but my roof is already cream in colour, isn't that close enough to white ?

    .
    Sorry, missed your post. Quite some time ago I had a link comparing colours, including cream. Will try and find it.

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    Seems all the pastels exceed 70% reflectivity, but there is a difference between normal and the special roof paints.










    Last edited by beer4life; 28-01-13 at 12:51 PM.

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    I've just had a brain storm - attach a diesel generator to the 3 hp AC.

    Can get cheap chinese diesel generators for about $4,000. Diesel runs on renewable oils but only runs when AC is on.

    Thus I can run my AC off the grid summer or winter without Electricity Bill Shocks! cheap foreign sun flower / olive oil shouldn't be that expensive ?

    .

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