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  1. #1
    Join Date
    Feb 2006
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    Perth
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    Default Solar PV system experience

    A few weeks back we had a 6.3/4.8 kW PV system installed. My 4 brothers and 5 sisters all have solar and most have had it for some time. One of the reasons we put off doing it was the awkward shape of our roof with none of it at optimised angles plus some occasionally shaded areas of roof. However one of my BILs is a solar engineer and explained how using panel optimisers or micro inverters would improve the efficiency and make it worthwhile. Anyway we went with 20 panels each with a micro inverter on 4 different roof segments. There is still 2 another roof segments with space for about 15 more panels in the future if we want to upgrade. Using micro inverters means we won't have to upgrade a large inverter.

    With my broken ankle I have not had much to do except faff about on the forums and watch the solar PV output on the supplied App. It's very interesting for a nerd like me to watch things like the output of the individual panels and power consumption during the day. The highest output I've seen is 4.88kWhr and remember none of the roof segments are at an optimal angle so I'm pretty happy about that. It's also pretty clear when various appliances like the coffee machine (2kW) and the 3 house rev cycle inverter ACs kick in and remember to turn them off if they are not needed. It's also interesting to see how the ACs chew more power as the temperature climbs.

    During the middle part of the day, provided there's no clouds, even when it's 40degC outside the solar provides the power to cover the 3 house ACs, plus 3 fridges, the smaller AC in the shed, plus an odd appliances like a washing machine or dishwasher. Even then we're still exporting some power.

    On on cooler sunny days we're generating about the same amount of kWhrs as we use for the whole day and night, of course the excess produced during the day is exported and so we're still importing power at night. It will be interesting to see what happens in other seasons.

    In two weeks there has been just 1, 15 min period where the power draw went over the 4.8kW output of the solar. Of course after about 4:30 pm there's a cross over period where output drops below use. That's a good time to remember to turn shed AC and coffee machine off. In the evening when it's been hot during the day we keep the house ACs running and power use depends on temp. Typically the power uses gets down to 1kWhr by midnight which is when 2 of the 3 house ACs go off just leaving just the bedroom AC on.

    The worst case scenario is hot but cloudy, when power generation drops to as low as about 1/3 of use. Fortunately not that many days like that in Perth.

    The evenings would be a good time have a battery but they're not quite there in terms of price but they don't need to come down much more to make worth considering.

    The other thing I've done is checked out on Google earth how many dwellings in our St (inner city suburb) have Solar and it turns out only 3 out of ~100 have this. My son's st in the outer burbs has 44% with solar. Perth average is supposed to be 25% with some Streets over 50%. OK many of these are small systems but why so few in inner burbs? I guess they don't care much about high power prices?

    Anyway so far so good and looking forward to see what it does to our power bills.

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  3. #2
    Join Date
    Feb 2006
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    Perth
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    Default

    Here's a typical power in/out profile for a good clear 40ºC day
    The previous day was hot so all 3 House ACs were left on the whole night.
    Orange is power consumed, pale blue is solar PV power, Dark blue is power exported back into grid.
    1 is when the coffee is tuned on.
    2 is when the 40ºC max was reached
    3 is max power output for that day (each time slice is 15 minutes so)
    SSOlarPV2020-02-14 at 8.02.45 pm.jpg

  4. #3
    Join Date
    Sep 2009
    Location
    Newcastle
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    549

    Default

    Bob, shouldn't the Y axis units be watts not watt hours?

    Are the produced and consumed figures for the full 24 hours? To my eye looks like you've consumed more than produced over the 24 hours.
    Edit: realised the figures at the top are just for the moment in time (12.15pm).

  5. #4
    Join Date
    Feb 2009
    Location
    moonbi nsw Aus
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    69
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    2,065

    Default

    In my situation (on a disability pension) I would have to borrow monies to install the panels so I reckoned that going solar would actually cost me more than just buying power as we need it. Is my thinking correct?
    Just do it!

    Kind regards Rod

  6. #5
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    Feb 2006
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    Perth
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    Quote Originally Posted by pippin88
    Are the produced and consumed figures for the full 24 hours? To my eye looks like you've consumed more than produced over the 24 hours.P).
    Yeah this was a 40C day and 28C night so we had the ACs on all night so solar was only able to provide half the total daily power needs. On a cooler clear day with no ACs running the solar should on average generate more than we use BUT During the day the immediate excess generated power over the immediate use power is exported so we will have to draw power from the grid and as our grid power costs 28c per unit and we only get 7c back for exported power we still have to pay but it will be much less than otherwise

  7. #6
    Join Date
    Feb 2006
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    Perth
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    Quote Originally Posted by chambezio View Post
    In my situation (on a disability pension) I would have to borrow monies to install the panels so I reckoned that going solar would actually cost me more than just buying power as we need it. Is my thinking correct?
    given the low cost of interest theses days and typical payback time of between 2.5 and 4 years, from what I can see it's a no brainer. Payback time depends on things like, usage patterns, roof layout and type of system. High use, large area of roof facing north and a basic/budget system will pay back quickest. Of course a low end system is then not going to last as long so total lifetime payback should be less.

    Complex roof layout with limited areas facing N, NE and NW, low use, and fancier system have longer pay back.

    Like anything, there are dodgy installers out there so you need to do your homework. Some of the salespeople are slicker than rubbish tip rat.
    To get started so you can reduce the impact of sales BS this website is one of the best out there in terms of easy to use and accuracy. The guy that runs it knows his stuff and I agree with pretty well everything he says.
    SolarQuotes | Get 3 Solar Quotes From Your Best Local Installers

  8. #7
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    Feb 2003
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    back in Alberta for a while
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    68
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    Quote Originally Posted by BobL View Post
    why so few [solar PV systems] in inner burbs? I guess they don't care much about high power prices?
    Don't know all that much about the inner 'burbs of Perth, but in Sydney, most of the inner 'burbs -- more than 90% in North Sydney Council area -- are rentals.
    When you're a renter the payback period on a non-portable solar system is infinite.
    regards from Alberta, Canada

    ian

  9. #8
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    Feb 2003
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    back in Alberta for a while
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    Further to the above, more than 50% of residents in Central Perth are renters.
    regards from Alberta, Canada

    ian

  10. #9
    Join Date
    Oct 2013
    Location
    Perth, Australia
    Posts
    1,813

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    Yeah my parents have had solar on their property for about a decade, I would LOVE to have a system but renting so it's a no go. Hoping to bite the bullet and get my own place in a year or two, just trying to save a bigger deposit because I don't want a huge mortgage.

  11. #10
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    Perth
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    Quote Originally Posted by ian View Post
    Further to the above, more than 50% of residents in Central Perth are renters.
    Of the 2.1 million people living in Perth, Central Perth only has ~27,000 residents so they're not even worth worrying about.

    Our almost exclusively residential suburb is only 2.5km from Central Perth and as we have lived in our st for >40 years we know the greater majority of the residents and estimate ~90% own their own dwelling. Of the 100+ dwellings in the St we are only the 3rd to get solar.

    Interestingly the largest solar producer in the suburb is the Zoo (250kW), plus there are several retirement villages (many of these have rental or short term accomodation) that generate 192kW each.

    In the new outer suburbs many schools have become major producers using 192 kW systems. The schools treat it as an investment as they are only open during the school day and no one is there for many days of the year including half of summer. The payback time is relatively short and after that they are making money. I have seen the odd new apartment block going up with large amounts of solar on the roof. Apparently the corporate body owns these systems and they sell the power to renters and do pretty well out of it especially once they have paid it back.

    I'm surprised more shopping centres aren't getting into the act as many have rooftop parking and raised solar panels could shade vehicles and generate power.
    The recently upgraded Westfield Carousel shopping Centre south of Perth has a 2MW system on its roof.

  12. #11
    Join Date
    Oct 2004
    Location
    Melbourne, Australia.
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    Default

    Looks good there Bob. Your Enphase system (going on the look of the graph) is an excellent micro inverter set-up. We had an Aurora micro inverter system on three different rooftops for our first solar panel system. It paid back inside 5 years, which was around 2.5 years quicker than our calculations.

    Last year we added more solar panels on our remaining East and West hipped roof sections, for this we went Enphase and think it is currently the best out there with regard to systems. The difference as far as I can ascertain, is that an east or west facing system is approximately 5% less than the optimal, which is north facing. Also our panels are on flat roof and hipped roof locations.

    We added batteries last year, really made a huge difference, really changed things. Batteries are however, expensive. We will not see a payback in the form of a positive Return On Investment (ROI). To us, purchasing a battery or batteries and trying to justify the ROI, wasn't what it was all about. Convenience and stability of the power supply was our first reason, running air conditioners into the night was secondary, but important for health reasons.

    Our system is 7.7kW in total and consists of two differently manufactured micro inverters all chanelled through a couple of inverters; one for each battery. We can, dependent upon temperature, draw a constant 5500W with a possible 10000W draw for short periods. However the higher the batteries temperature, the lower the maximum and constant draw will be. Super fascinating stuff.

    We purchased enough battery capacity and electronic though put, to run anything we have through the system. With the batteries hovering around a 5% State of Charge (SoC) immediately after firing them up and waiting approximately 20 minutes, we started testing them. Two air conditioners, electric kettle, oven and microwave were switched on, we started to draw around 7250W from the batteries. Things were looking good, then suddenly the draw upped to somewhere around 8500 + Watts. Worried looks, then we noticed that someone had turned on a vacuum cleaner.

    We have Z Cell flow batteries.

    Mick.

  13. #12
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    Feb 2006
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    Perth
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    Default

    Quote Originally Posted by Optimark View Post
    Looks good there Bob. Your Enphase system (going on the look of the graph) is an excellent micro inverter set-up. We had an Aurora micro inverter system on three different rooftops for our first solar panel system. It paid back inside 5 years, which was around 2.5 years quicker than our calculations.
    Yep its an Enphase system.

    Last year we added more solar panels on our remaining East and West hipped roof sections, for this we went Enphase and think it is currently the best out there with regard to systems. The difference as far as I can ascertain, is that an east or west facing system is approximately 5% less than the optimal, which is north facing. Also our panels are on flat roof and hipped roof locations.
    Sounds familiar.
    We have no directly facing north (or south) roof spaces, its all NE or NW (or SE or SW). Fortunately the biggest is NW so it catches the afternoon sun which is when our ACs are most likely to be running.
    The house roof has many different angles. Those facing NE and NW with enough unshaded space are at 12, 18, 25 and there is a small one that is about 30º. We have room for up to another 15 or so panels with NE or NW direction if we need it. The shed has enough room for more than a dozen NW facing panels but almost all would be in deep shade by midday and all through the afternoon.

    Thanks for the battery info - we are looking at all this closely but we'll wait for at least 12 months before we do this.
    One of my sisters has a 17kW! system and is looking at batteries. It will be interesting to see what she decides as as she is also seriously looking at an EV. One of my Bros is moving to a place with a massive north facing roof so he will be installing a large solar with batteries, plus he's getting a Tesla3 in about a week.

  14. #13
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    Jun 2005
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    Townsville. Tropical Nth Qld.
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    I just thought I would throw this in. I have a standard 5kW North facing system, paid itself off quicker than estimated. Only issue I have had is I have to turn it off to use the plasma cutter in the shed, but the inverter drive on the Laguna wood lathe is not affected, one of those electrotrickery things I guess.
    Rgds,
    Crocy.

  15. #14
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    Perth
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    Quote Originally Posted by Old Croc View Post
    I just thought I would throw this in. I have a standard 5kW North facing system, paid itself off quicker than estimated. Only issue I have had is I have to turn it off to use the plasma cutter in the shed, but the inverter drive on the Laguna wood lathe is not affected, one of those electrotrickery things I guess.
    Rgds,
    Crocy.

    What happens if you don't turn it off?

  16. #15
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    Jun 2005
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    Quote Originally Posted by BobL View Post
    What happens if you don't turn it off?
    It keeps on triggering the over temperature cutout. I got the installers and the local energy supplier to have a look and as I am very close to the supply transformer, which is set at 251 volts, on the upper limit, the inverter is wound up higher to pump the solar output into the system. So it appears that the plasma sees that, plus some strange 5th, 7th and 13th harmonics as an issue.
    Rgds,
    Crocy.

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