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goughy

Solar power, cost, installation etc etc

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1 minute ago, goughy said:

Had a chat to a friend nearby who seemed to have a fairly big system, to see if they're happy with it.  They have a 25kw system with 78 panels and fronius inverter! Holly snapping ducks.  Very happy, their bill had gone from 4k a year to 1.2k back.  22k system will have paid for itself in 4 years.

Seems to me that the fronius inverters are the way to go.  My friend said 7.5k for the 6.6kw system seemed a bit expensive, but change or the REC panels to the other type they install drops the price by 1k.  Still waiting to hear from others etc.  Not gonna rush it.

I've kept a record of our usage over the last week.  Taking a reading around 8am and 5pm.  Used a total of 193.85kw for the week, with 82.55 during the day and 111.3 at night.  But the aircon has been heating every night, and only once during the day for one afternoon.  So that's about a 43% to 55% day to night split.  I'd expect that to even up over summer with a lot more aircon use during the day.

This is how the dude suggested the panels would fit.  The left side is east facing.  The West  gets some shading from the next house at about 4pm mid year.  It gets no shading in summer.

The Mrs is still really keen, but it comes down to what we can get within a budget of $110 a fortnight for total electricity expenditure.  She also likes the REC panels, but changing brand drops the total cost 1k, up to probably 1.5k for the 8kw system.   That's a lot of bickies.

And we've still only got a price from one place that I would put into the event basket.  I'd like at least 3 more yet.

 

6D28B847-88B8-4A58-AE53-CF001265B445.png

FC510D5D-9F9A-4540-B609-A5966DF01EF2.png

 

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2 hours ago, goughy said:

Had a chat to a friend nearby who seemed to have a fairly big system, to see if they're happy with it.  They have a 25kw system with 78 panels and fronius inverter! Holly snapping ducks.  Very happy, their bill had gone from 4k a year to 1.2k back.  22k system will have paid for itself in 4 years.

Seems to me that the fronius inverters are the way to go.  My friend said 7.5k for the 6.6kw system seemed a bit expensive, but change or the REC panels to the other type they install drops the price by 1k.  Still waiting to hear from others etc.  Not gonna rush it.

I've kept a record of our usage over the last week.  Taking a reading around 8am and 5pm.  Used a total of 193.85kw for the week, with 82.55 during the day and 111.3 at night.  But the aircon has been hearing every night, and only once did the day for one afternoon.  So that's about a 43% to 55% day to night split.  It's expect that to even up over summer with a lot more aircon use during the day.

This is how the dude suggested the panels would fit.  The left side is east facing.  The West for starts get some sharing from the next house at about 4pm mid year.  It gets no shading in summer.

 

6D28B847-88B8-4A58-AE53-CF001265B445.png

FC510D5D-9F9A-4540-B609-A5966DF01EF2.png

If north is the direction of the arrowhead, how come all the shadows are on the north side of stuff? Seems a bit strange to me. Shadows should be either on the east, west or south side of objects.

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The arrow is pointing South.

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Oops!  Blonde moment sorry!  I blame using one of these fang dangled iPads instead of a Google tablet 

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OK, well that makes more sense now :)

Panel orientation and how the strings are connected to each MPPT (maximal power point tracker) of the inverter is actually a bit of an art and is one reason why quality installers are worth the money. Getting that right makes quite a difference to the performance of a system.

As a rule of thumb (in Sthn Hemisphere), North facing is best for overall kWh production, and then West is best for production later in the day (when air con is more likely to be on). West facing arrays tend to provide useful power about an hour later than North arrays.

A combination of East and West can work well. While overall production will be a little lower than a North facing array the energy production will be spread out over a longer time period, and have a lower peak. It also means the potential for the inverter needing to clip PV output is much lower. I would prioritise the slightly North West side over the slightly South East side. But it needs balance as there will be a minimum and maximum number of panels you can connect to each MPPT.

One other thing I would say is to be certain there really is the space to fit the panels they say they can. When I see panel rough-up designs showing them close to the roof ridge lines, the strong possibility exists that the guys actually do the instal will either:

i. say they can't fit the system and you'll then end up with something you hadn't contracted for, or

ii. fit them anyway with overhangs.

Having panels overhang roof lines is ugly, and can also mean a compromise in the proper fixing of the panels. Don't discount the aesthetics of the way they are installed. They should be very well aligned, not offset or angled differently (in any plane). It just looks crap otherwise. If they are happy with such a loose instal, it's also a sign they'll do a crappy job cabling as well. Cables should be very neat and tidy and be run as hidden cabling as much as possible. Ask beforehand exactly where and how they plan to cable it.

I would ask to see examples of their previous installations.

See this image:

67249246_10217478542609892_2049926880370

Here the end panel overhangs the ridge line, and because of that they could not run the supporting top brace under this panel and used just one end clamp. It's just not secure. And in order to have the one remaining brace to hold that panel close to its centre, it meant they placed the lower brace too close to the middle of the panel, leaving too much panel overhanging the lower brace position for the entire array.

This sort of stuff results in panel stress, which micro-cracks the PV wafers and ruins panels.

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Thanks again Alex!  Should have a few more quotes this week hopefully.  I've also asked that guy to confirm for me what the other panels are that they use, and to rework the figures on a 50/50 day night usage, as it was originally done on a 60/40 split but I'm finding I use less juice in my workshed than I thought.

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Ok, so let's see if I can get my head around this!  Just trying to work out our savings with a 5kwh system.  I found a chart somewhere that data's where I am has an average of 5.16hrs a day of daylight.  So do I use that to work out what a system can generate?  Doesn't seem a lot really, but I'm assuming it takes into account cloudy and rainy days?

We used 10230kwh of electricity over our Last 4 bills, for 28.73kwh per day.  Currently we seem to be using 9kwh during the day at its lowest, up to mid to high teens on heavier days.  So say with intelligent appliance usage (in the past I'd run dishwasher overnight and even washing machine and dryer etc) I could get that split to 50/50 day/night?  So I have the 10230 to 5115 and times that by our rate which is .25298; and get to $1328 in savings on electricity actually used.  Then I work out how much we export, which is the remainder of the 25.8 generated on average so 11.8kwh x .078 which equals another $335 a year.  So total saving of $1663.  Looking at the finance options through that solarquotes website, the 5kwh system with fronius and REC panels would cost us $1740 a year ($7500 upfront cost) or with cheaper but still good panels $1512 ($6500 upfront cost).

Is that on the right track?  Am I short changing how much electricity it can generate?    And then would I just follow the same methodology for an 8.2kwh system.  Ergon restricts the feed in to no more than 5kwh so I'd have to take that into account.  So basically the saving for electricity used would be the same, but the difference is the feed in?  So say it feeds in 25.8kw X .078 equals $734 a year.  The $1328 you get to $2062 saving a year.  The dearer system would be $2784 a year, the cheaper panels $2328.

So if we could stretch it further, the 8.2kwh system will give us a better return over its lifespan, but will cost us more than our current bill average for the next 5 years.  The 5kwh system would be doable for about what we pay now, but the return later would be less?

By all means, tell me if I'm on the won't track!  Math is not my strong suit!

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I had a chat to a family friend of my wife, who lives nearby and seemed to have a big system.  78 panels and a 25kw fronius system!  Pluck-a-duck!

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The 5.16 hours/day is the peak production equivalent for your location (and hopefully also adjusted for you panel tilt and orientation).

IOW 5.0kW of panels x 5.16 hours/day = 25.8kWh/day production (on average).

8.2kW * 5.16 hours/day = 41kWh/day

Now how much of you daytime consumption can you offset? 

Keep in mind that at 8am when you put the kettle on (~2kW demand), the PV system may not yet be producing enough power to wholly offset that usage.

But let's assume you can, on average, offset 12kWh/day.

Then the calculation is:

Replace grid imports (self consumption of solar PV):

12kWh @$0.253/kWh = $3.04/day

Export to the grid (production less self consumed):

For 5kW system: 25.8kWh - 12kWh = 13.8kWh @0.078/kWh = $1.08/day
For 8.2kW system: 41kWh - 12kWh = 29kWh @0.078 = $2.26/day, but let's assume you lose 5% due to export limitation, so say $2.15/day.

So the earnings and savings are:
5.0kW system: $3.04 + $1.08 = $4.11/day = $1,501/year
8.2kW system $3.04 + $2.15 = $5.19/day = $1,894/year

If we drop the grid replacement assumption down to 10kWh/day, then:

Total earnings & savings:
5.0kW system: $3.76/day = $1,373/year
8.2kW system: $4.82/day = $1,762/year

 

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Ok, so taking your worser case figures there... The only real difference between the two systems is the larger one will feed more into the grid.  The smaller one will still really cover or electricity usage while it's generating, since we don't hear our water or pools or anything.  So the larger will only save us about 400 a year, but will cost us an extra 5200 to get.  So that's 13 years to pay back is benefit?  Am I seeing that right?

It seems to me the 5kw is worthwhile, but the bigger less so.  At least not worth it until batteries become cheap enough.

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5 minutes ago, goughy said:

 

It seems to me the 5kw is worthwhile, but the bigger less so.  At least not worth it until batteries become cheap enough.

Agreed, unless you can move more of your night usage to daytime. I've done that in a small way trying to cut out night use of the washing machine, dishwasher & drier, but the other half just keeps using them whenever it's more convenient.

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Nah.  There's not another thing I could possibly move.

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I think you should seriously consider a 6.6kW system with the same inverter capacity of 5kW. I'm a little surprised that wasn't an option presented.

The extra panels are a very low additional cost on top of 5kW as the extra STC rebate you get covers most of the difference (the extra rebate for those 1.6kW of panels is worth about $900-$1,000).

The 133% oversizing makes *very* efficient use of inverter capacity and export clipping will be minimal (especially given your likely panel layout).

For sweet spot financial return on a single phase connection it's very hard to beat 6.6kW of panels + 5kW inverter.

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Yeah sorry, when I was talking system I was talking inverter size.  The 5kw ones mentioned so far have 6.6 of panels, or 6.51 with the guy today.  My wife is more about the larger system, but I can see we're not getting much for the extra cost.  And I can see what you mean about the oversizing capacity of the panels compared to the inverter.

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Well, the dudes keen.  Just messaged me that his boss will do the 10.7kw system (I'll start starting the system size properly now) for 10800 till the weekend, 1200 off.  Told him we're more keen on the 6.6 system, so will see what he says.  Still want a couple more quotes really to decide.  

Even though they cost a bit more, the Mrs is keen for the dearer REC panels.

Edit to add: and if you guys think you're sick of hearing from me about this, you should see the barnies me and the Mrs are having!  She's sick of the word solar, and I remind her that she started this by letting the door knocker in, so it's her fault.

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So that's 10.7kW PV panels with an 8.2kW Fronius inverter.

Just doing a quick check via PV Watts, assuming even distribution for east and west panels, then you'll see an average annual production of ~15,200kWh (which is an average of 41.6kWh/day), so in line with the 41kWh/day estimate you were given (and is based on better knowledge of exact array set up as I was making a few assumptions).

There's only a total of about 16kWh (i.e. bugger all) of annual production exceeding the inverter capacity of 8.2kW. The peak nominal output from the PV array for any hour is 8.3kW (because of the split E-W panel orientation you won't ever see output reaching 10.7kW).

This is what the output will look like for a good summer day. A 10.7kW system hitting a peak output of 8.3kW, and a total production of 70.8kWh for the day:
 

amw7wO8.png

So what about export limit? Well if you can only export 5kW and we assume that during the day you draw, on average, 1.5kW, then any production above 6.5kW will be lost.

This amounts to about 2,700kWh/year.

It may not be that high though, as it is during the hotter summer months when higher outputs occur and this will coincide with increased daytime consumption for air con. From May through July you'll rarely have a PV output > 5kW at any time. Hourly outputs above 6.5kW really only starts happening from September, and occurs more regularly in summer and declines until March.

So when doing the sums, you should do so on the basis that the nominal PV output will be reduced by this much due to export clipping. At 7.8c/kWh, that's about $200/year of FIT income and if you do run aircon during the day in summer months, then less of this  will be "lost".

Also keep in mind that panel output declines a little each year (varies but generally about 4-5% per decade).

Grid replacement: 12kWh/day @$0.253/kWh = $1,110/year

Export to the grid (production less self consumed):

(15,200 - 2,700) - (12 x 365) = 8,120kWh @$0.078 = $633/year

Total E&S: $1,743/year

Cost: $10,800 (assume this sticks, the sales pitch discount will apply later I'm pretty sure).

10,800 / 1,743 = 6.2 years simple payback, an ROI of ~16%

 

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If you ever get an electric vehicle, daytime charging will be a great way to avoid export clipping. This is one reason to consider a larger array now. It's not easy to expand a string array later on once it's installed.

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The reason I would consider the larger system is for future proofing.  These panels have 20 manufacturer warranty, increased to 25 if installed by an approved installer, which they say they are.  So that's up with lg type warranty.  So I'd be hoping to not have to replace them.  But in 10 to 15 years battery systems may become worthwhile, and hopefully the panels will still be going strong enough.  I expect at least 25 to 30+ years of still living here.  If we move, it's because we've gone bust and I really won't be caring about what's screwed on the roof.

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LG panels are definitely at the premium end and should perform very well over the long haul. REC are also up there. My panels are more at the more affordable end but they are still quality product and I have confidence in them. I ranked having a good quality installer more important than going for higher end panels.

As you note, batteries are just not financially viable option at present. For a location where the import and export tariffs are 8c/kWh and 25c/kWh respectively, then a battery would need to cost (installed) less than ~$360/kWh just to break even over its typically 10 year warranty life. For a payback of 7 years it would need to cost less than $250/kWh to install.

At the moment batteries cost >$1,000/kWh installed. Battery prices have a very long way to fall before they make financial sense. That's not to say there are not other good reasons why one might get a home battery, just that saving money isn't one of them.

Edited by Alex Simmons
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So I had a look at our gas bill, and it's day we're paying about 600 to 700 a year for LPG for our instant hot water system and cooktop.  The bbq is dead so it hasn't been used.

We've never ever had electric hot water before, have always had gas systems.  How does electric hot water function best with solar systems?  Do they only heat during the day etc?  Obviously it's something we would consider when it needs replacing.

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6 minutes ago, goughy said:

We've never ever had electric hot water before, have always had gas systems.  How does electric hot water function best with solar systems?  Do they only heat during the day etc?  Obviously it's something we would consider when it needs replacing.

Our previous home had electric, and we used off-peak controlled tariffs, so it heated at night but at a cheaper rate. At this house we have a solar HWS. Talking to a friend who is a plumber he said it's oversized for what we really need, but that means it heats up quickly and there's a lot of capacity. It has an electric boost, but we usually have that turned off so the thermostat doesn't even trigger it. It needs 3 or 4 overcast days in Winter before we bother to turn it on.

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Thought you guys might like this. Snapshot of pricing in the national electricity market in mid July - clear skies and wind. Good luck exporting your power and receiving income at a forecasted rate to pay it off. It’s great renewables are continuing to come into the market but I’d question the assumption you’ll be able to export it into the grid on a long term basis. I’d also ask whether or not you might be penalised for exporting when the grid becomes full and could be causing destabilisation issues - big (as in bigger than you need) isn’t always better. The lack of a clear and coherent energy policy Federally and on a state by state basis needs resolving sooner rather than later. 

3462508D-EF22-4D41-9815-CC66F98942B3.jpeg

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So with solar and electric hot water, are you able to keep the HWS on "off peak" and separate from your solar? 

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2 hours ago, truck said:

Thought you guys might like this. Snapshot of pricing in the national electricity market in mid July - clear skies and wind. Good luck exporting your power and receiving income at a forecasted rate to pay it off. It’s great renewables are continuing to come into the market but I’d question the assumption you’ll be able to export it into the grid on a long term basis. I’d also ask whether or not you might be penalised for exporting when the grid becomes full and could be causing destabilisation issues - big (as in bigger than you need) isn’t always better. The lack of a clear and coherent energy policy Federally and on a state by state basis needs resolving sooner rather than later. 

3462508D-EF22-4D41-9815-CC66F98942B3.jpeg

That represented one 5-min block of wholesale spot price. The actual half hour wholesale prices at that time were more like $6 - $7/MWh.

Also, consumers pay (and are paid) a retail rate, not a spot wholesale rate. The retail rates are based on overall supply and demand factors for an entire 12 months, not just based on one 5-min period. IOW that same argument could be used when there are super peak wholesale spot prices, yet consumers don't pay those either.

Keep in mind that as ageing coal plants are decommissioned (and a LOT of such capacity will disappear in the years ahead), renewables are required to make up the slack. It also means that storage solutions becomes more important, as well as more viable at the grid, regional, local and household level, and that changes to the grid network are required to enable greater flexibility in how energy is moved around.

Rooftop domestic solar will continue to be a useful and valuable resource in the NEM for many years.

I wholeheartedly agree that the lack of a coherent federal government policy on energy is setting us up for some serious problems. Angus Taylor is a complete disaster for this nation.

Fortunately the cost of domestic solar PV is continuing to fall such that it is viable anyway.

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3 hours ago, roxii said:

So with solar and electric hot water, are you able to keep the HWS on "off peak" and separate from your solar?

My HW is on a separate controlled load, and this circuit is separate to those which my solar PV supplies. The controlled load circuit also has a separate meter.

You cannot have hot water system able to be switched between a controlled load supply and a regular circuit supply (to which solar PV is connected).

Of course you don't have to have your hot water on a controlled load. You can choose for it to be powered via your regular circuits, and then you can arranged to have it supplied using your solar PV production.

Controlled load for HW makes more sense for us since the controlled load tariff is 11.4c/kWh, while I get 12.5c/kWh for exported energy. IOW it's cheaper for us to leave HW on a controlled load than to use our own solar PV. And that also means my excess solar PV is left free for offsetting future energy demand (such as the granny flat we will be building).

Which solution is best for hot water is individually variable and is actually a bit complex. It requires an assessment of the specific circumstances.

If for instance you don't have a controlled load available (common in Victoria where in many locations controlled load has been or is being phased out) and the rate you are paying is high, then it makes sense to look at ways to reduce the cost of heating water.

Two main methods:

i. reduce the price you pay to heat the water
ii. reduce the energy required to heat the water

and of course a combination of both. Of course you can also look at ways to use less hot water but I'll leave that aside.

For i., one way to is have your hot water system on only when prices are lower, which requires that you are on a time of use (TOU) tariff structure. So be on TOU and have the HW system use a timer that only allows it to heat during off-peak tariff periods. But the catch here is you are now on TOU tariffs and this may not work out to be better overall. It depends on your energy use patterns.

Another way is to use excess solar PV production. This can be done via a dumb method, i.e. a simple timer switch that turns on the HW circuit for a period during the middle of the day when it is most likely you'll have sufficient excess solar PV production. Of course you won't always have enough solar PV (e.g. cloudy day) and at times it will still draw some energy from the grid, but you might be able to say get 80% of the energy from the solar PV and so the cost is reduced significantly (you are in effect paying the same rate as your feed in tariff). To make this work for many can require a modest modification to their tank such as replacing the higher power (e.g. 3.6kW) resistance coil with a lower power coil (e.g. 1.2kW). It'll take longer to heat the water, but the power draw is lower meaning it's more likely your solar PV will have sufficient excess output to meet the power demand.

Or you can install a smart system that monitors your actual PV output and demand and switches on the HW circuit only when there is sufficient excess solar PV, with a fail safe logic to draw from the grid only if it really has to. This might jump the use of solar to heat water up to say 95% needing only to draw from the grid occasionally.

The cheap timer switch (~$50) is mostly likely to have the best ROI, as the smart switches are pretty expensive (think $800-1,000). That extra 15% less reliance on grid power will take quite a long time to recover.

Then there is ii., ways to reduce the electrical energy required to heat water.

One can look at solar HW systems, e.g. the tube systems fitted on the roof which heat water directly by collecting direct heat energy from the sun. There are various forms of this tech and there are thousands of such systems on the rooftops on homes. But they are quite expensive and require a deal of maintenance as they age such that pretty much their day is done. They still have their use case but it has diminished a lot. Using solar PV to heat water via an electrical system is far cheaper, more flexible and a lower maintenance solution. 

The more common way nowadays is to use a heat exchange pump to heat the water. These operate exactly the same as an aircon heat exchange unit but rather than warm (or cool) air, they heat the water by transferring heat from the air. A good heat pump can supply ~4kWh (more or less) of heat to water for only 1kWh of electrical energy input. As such it only needs to draw about 1/4 of the energy that a regular resistive unit hot water tank requires. Wow!

But there's a catch. Heat pump HW systems cost a whole lot more than resistive HW water tank units. e.g. you might pay $1k for a resistive unit tank, and $4k for a heat pump HW system. So can you save that $3k within the time such systems can reliably operate for?

In my case, the answer is no. Since I am on a controlled load at ~11c/kWh, and we use 5-6kWh/day to heat water, then HW heating costs us ~$200/year. So even if I drop that to 1/4, the saving is only $150/year, meaning it would take 20 years to make up for the price difference between a resistive heater tank and a heat pump system. That's too long for such tech.

But if your hot water energy tariff is much higher, and you use a lot more hot water than 2 people, then the equation changes such that a heat pump unit becomes much more viable.

e.g. say hot water is costing you $1k/year, then a combination of solar PV reducing the effective tariff, a timer and a heat pump can save $800/year. Now that $3k extra for a heat pump system starts to make a lot more sense.

Edited by Alex Simmons
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I should add that any HW system set up needs to also ensure the water gets heated high enough every few days (i.e. at least 60ᵒC) to ensure no legionella bacteria can survive/thrive. Normally this isn't a problem if power is made available for a minimum duration each day.

e.g. we have a 250l tank. Assume it is totally emptied of all hot water.

To increase the temperature of 250l of water from cold inlet temp, say 15ᵒC, to 60ᵒC requires:

250 litres x 1000 cal/litre/ᵒC x (60-15)ᵒC = 11,250,000 calories = 13.1kWh

So heating with a 3.6kW resistive element the tank would need to be on for 13.1kWh / 3.6kW = 3.6 hours. That's from being completely empty of hot water and pretty cold water input. Our cold water is probably more like 20ᵒC. If the tank has a lower power resistive element, then the heating time needs to be longer.

Of course if it was a heat pump unit, then the heat transfer rate will be similar to the 3.6kW element, but require only 3.3kWh of electrical energy for 3.6 hours, IOW power supply need only be ~900W. Easy for most solar modern PV systems to provide that sort of power for long enough even on dullish days.

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3 minutes ago, Alex Simmons said:

Easy for most solar modern PV systems to provide that sort of power for long enough even on dullish days.

It's phenomenal how hot the water gets from the roof panel, even on an overcast day. We actually had the tank on the ground replaced under warranty, and I was helping a plumber mate to do it. The first bit of water that went through it (a very dull Winter morning, and the panel faces west) came out as steam. Admittedly that quickly cooled the panel down, but it shows how hot it can get.

The plastic drain under the release valve outlet had to be replaced by a metal one, as the PVC pipe warped as did the drain cover on it due to the heat.

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4 minutes ago, Ex-Hasbeen said:

It's phenomenal how hot the water gets from the roof panel, even on an overcast day. We actually had the tank on the ground replaced under warranty, and I was helping a plumber mate to do it.

They sure can heat water really well, and work better at some latitudes than others. Definitely environmentally better.

They are considerably more expensive to install though, like twice the price of a heat pump system, and a whole stack more expensive than a simple resistive element tank (like 6-8 times the price). Heat pumps also have their reliability and maintenance issues.

What's changed is the dramatic fall in the cost of solar PV, while cost of traditional solar HW systems hasn't really changed.

This means a standard resistive element with solar PV and diverter to power it is pretty cost effective option now days and the lowest maintenance of the lot. If you have the roof capacity to spare.

This article is a pretty good summary of the options, although the space required for 2kW of solar PV is about half nowadays than is shown in this item, which means the roof space is now not all that much more than is required for solar HW system:

https://www.solarquotes.com.au/energy-efficiency/hot-water.html

Again much depends on how much you currently pay to heat water. For us using the least energy efficient method (electric resistive HW tank), it's still only ~$200/year, and so the incentive to install expensive systems just isn't there.

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2 hours ago, Alex Simmons said:

Keep in mind that as ageing coal plants are decommissioned (and a LOT of such capacity will disappear in the years ahead), renewables are required to make up the slack. It also means that storage solutions becomes more important, as well as more viable at the grid, regional, local and household level, and that changes to the grid network are required to enable greater flexibility in how energy is moved around.

Rooftop domestic solar will continue to be a useful and valuable resource in the NEM for many years.

I wholeheartedly agree that the lack of a coherent federal government policy on energy is setting us up for some serious problems. Angus Taylor is a complete disaster for this nation.

Fortunately the cost of domestic solar PV is continuing to fall such that it is viable anyway.

Just on this, renewables are forcing coal out and not the other way around (which I have no issue with btw) - it's why all this chatter about building a new SCC fired power station is just a waste of time.  Coal needs to operate in baseload to be efficient and it can't do that if large chunks of the market disappear through renewable generation at zero or close to zero short run marginal cost.  However, to ensure we as consumers have the 24/7 reliable cost effective power supply that we demand, there needs to be a bigger solution and, unfortunately, in the short to medium term  it's not batteries or pumped hydro backing up wind/solar.  The only viable solution right now is fast start gas generation to provide that back up which opens up another can of worms.  Ultimately on solar, it can be as cheap as you want but it will never be the full solution.

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1 hour ago, truck said:

Ultimately on solar, it can be as cheap as you want but it will never be the full solution.

Solar has never meant to be the full solution. To become 100% renewable requires wind and firming technologies. Wind is on track and continues to get better. Storage needs to follow. Storage seems slow to grow at present but we can certainly do it.

The current grid will cope up until we get to ~60% renewables (we are at ~20% at present). Beyond that firming technologies are required. That can be a mix of distributed time production (turning wind plants on/off) and distributing them to take advantage of different geographical wind supply, along with improved grid connection and capacity, and of course storage of which pumped hydro is the most logical option and for which there is more than ample potential capacity.

The LCOE continues to fall for these solutions. Batteries of course will be key for grid stabilisation services but not required as major storage capacity.

One thing is for sure, the LCOE for these firmed renewable solutions are a fraction of the nuclear energy option.

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On 21/06/2019 at 7:40 PM, Parkside said:

And I'm live. I believe it is connected and the spinning meter may in fact be spinning backwards during the middle of the day, but I'm not sure, they told me not to touch anything. 19kwH produced today.  Final meter read next week, then new meter installed ASAP by new retailer.

Highly recommend AG Solar for Shire/Illawarra instals. Trustworthy and seamless from first contact. Mention my name (PM for my Bruce Wayne) when you get an online quote and I get a kickback.

Matt, The guy from AG is a parent at Janene’s preschool. 

He is looking at trying to wrangle a grant of some sort to do the preschool and I’ve asked her to get him to swing by here and give us a quote for the house. 

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The admin of my old golfing forum told me to get in touch with one of the members there who's a solar installer up in Cairns.

He flat out said don't go bigger than 6.6, and that the prices I've been given so far are too high, even for rec and fronius.

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15 hours ago, roxii said:

Matt, The guy from AG is a parent at Janene’s preschool. 

He is looking at trying to wrangle a grant of some sort to do the preschool and I’ve asked her to get him to swing by here and give us a quote for the house. 

drop my name!! Trent and Daniel were very professional 

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On 06/08/2019 at 7:39 AM, Alex Simmons said:

If you ever get an electric vehicle, daytime charging will be a great way to avoid export clipping. This is one reason to consider a larger array now. It's not easy to expand a string array later on once it's installed.

Would the cost of electricity affect this? Reason I ask is I’m involved in two corporate energy projects at the moment.

This involves lengthy workshops with not only energy companies but regulatory advisors. One  takeaway is that energy companies can detect what you are using the energy for an EVs  could  attract a tariff of their own in the future.

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1 hour ago, FatPom said:

Would the cost of electricity affect this?

Cost of electricity has nothing to do with how an inverter will clip excess production which exceeds the export limit set by the local distribution company.

Perhaps you need to rephrase your question?

As to what they can detect - they cannot detect anything happening behind the meter, IOW they can't know how much power you are consuming, nor what you do with power behind the meter, nor can they detect how much power your solar PV system is producing.

All they can detect is how much power is coming from or going to the grid as that's what their meter registers.

e.g. 

Solar PV system is producing say 5kW (at any instant).

Your home is consuming (at that same instant) say 8kW. Hence you are importing 3kW from the grid.

All the power company knows is you are importing 3kW. They know nothing about your total production or consumption. They can infer this at night when of course production = zero, hence consumption = grid imports. Unless of course you have a battery, when they once again have no visibility on the power flows happened behind the meter.

For a power company (or anyone else) to know what's going on behind the meter, then the home power system (inverter and battery or EV battery charging system) would have to be networked with a link back to the power company.

The exception would be the case of a separate circuit which is not connected to solar PV or home battery system - which is the case for my hot water system. In this case the consumption is is fully known by the power company. Indeed they control when that circuit is on or off (which is why it is a low cost tariff since they only turn it on during periods of low demand and low wholesale prices - although they are required for that circuit to be on for a minimum agreed duration each day).

Edited by Alex Simmons

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On 07/08/2019 at 10:36 AM, truck said:

Snapshot of pricing in the national electricity market in mid July - clear skies and wind. Good luck exporting your power and receiving income at a forecasted rate to pay it off.

One thing I can see happening as the duck curve gets deeper is electricity distribution companies beginning to turn on controlled loads during the middle of the day. They already do in my area on weekends. It makes perfect sense when there is an abundance of cheap power, and it is in effect making direct use of some of my own solar PV production which means it never even gets past my local transformer, let alone to one of the neighbouring properties.

It has other benefits, one being the mix of power during middle of day has a higher proportion of renewables as the source compared with night time production, so it has environmental benefits, plus the issue of high grid voltages on local areas can be mitigated by putting extra demand on the system (which drops the grid voltage) to balance the rise in voltages occurring because of the high solar PV outputs.

I know when my HW tank turns on, the phase it is connected to drops by 10V. I have one phase in particular which suffers from high grid voltages, and my inverter has to manage these situations, occasionally limiting output because the voltages are >255V and sometimes >258V.

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53 minutes ago, Alex Simmons said:

Cost of electricity has nothing to do with how an inverter will clip excess production which exceeds the export limit set by the local distribution company.

Perhaps you need to rephrase your question?

As to what they can detect - they cannot detect anything happening behind the meter, IOW they can't know how much power you are consuming, nor what you do with power behind the meter, nor can they detect how much power your solar PV system is producing.

All they can detect is how much power is coming from or going to the grid as that's what their meter registers.

e.g. 

Solar PV system is producing say 5kW (at any instant).

Your home is consuming (at that same instant) say 8kW. Hence you are importing 3kW from the grid.

All the power company knows is you are importing 3kW. They know nothing about your total production or consumption. They can infer this at night when of course production = zero, hence consumption = grid imports. Unless of course you have a battery, when they once again have no visibility on the power flows happened behind the meter.

For a power company (or anyone else) to know what's going on behind the meter, then the home power system (inverter and battery or EV battery charging system) would have to be networked with a link back to the power company.

The exception would be the case of a separate circuit which is not connected to solar PV or home battery system - which is the case for my hot water system. In this case the consumption is is fully known by the power company. Indeed they control when that circuit is on or off (which is why it is a low cost tariff since they only turn it on during periods of low demand and low wholesale prices - although they are required for that circuit to be on for a minimum agreed duration each day).

They absolutely can tell what you are using the power for. I’ve seen a demo at the DNO NOC

Im not talking about solar, I’m talking the power profile. If you are using electricity to charge your car, the power company can absolutely 100% see that. In turn, that might ( almost certainly will) result in a different tariff, which could affect the import/export financial equation.

That assumes that Oz power companies are as astute as the UK ones.

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I'm sorry but how can they possibly know what the electrons are being used for?

And if a car is being charged while the solar PV array is producing, it never even registers on their meters.

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2 minutes ago, Alex Simmons said:

I'm sorry but how can they possibly know what the electrons are being used for?

And if a car is being charged while the solar PV array is producing, it never even registers on their meters.

The do it through a spike profile.  Read my post again, I’m not talking about the PV, I’m talking about how much a household might pay for electricity in the future. It’s pretty obvious.

But hey, I’ve only made my living out of these two projects for the last 18mtjs, so clearly I’m lying. Have at it.

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Say my car needs 5kWh today, and none tomorrow because I don't use it, and 20kWh the next day because I went for a longer drive, then none the next day, then 3kWh, 7kWh and so. On those same days I changed to pool pump usage, ran the air con for different periods, decided to use the oven/cooktop amongst other things that will vary from day to day and season to season. They can't possibly extract from my grid import data:

i. whether I charging an EV at all,

ii. how much of the grid import was used to charge an EV,

iii. what proportion of total energy consumption was used for the EV, nor

iv. what impact behind the meter production has on all of the above.

The only way they can do that is if the EV charging is data networked.

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2 minutes ago, FatPom said:

The do it through a spike profile.

But the spike profile they can see is only what happens in front of the meter.

What happens in front of the meter is affected by what happens behind the meter (due to solar PV and batteries) and what else is using energy at the time.

My EV might begin to charge but the amount of energy being drawn from the grid will be variable because my solar PV is supplying some of the power needed. Indeed as the clouds come and go the grid power draw will be quite variable.

Say my home battery decides to start charging in the evening because it detects a storm is coming and the software thinks it's a good idea to top up in case of outages? How will it detect the difference between that an an EV being charged?

In any case, what smart use of EVs will enable is for prices to be lowered as 2-way power flow to/from EV batteries enables virtual grid storage for grid stabilisation.

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41 minutes ago, FatPom said:

In turn, that might ( almost certainly will) result in a different tariff, which could affect the import/export financial equation.

Let's say they can know it (but I doubt it - keep in mind 20+% of homes here already have solar PV system) and they do charge a different tariff. All I will do is decide whether it's better to charge my vehicle from the grid, or from my solar PV. Just like I have chosen to have my hot water heated from the grid rather than my solar PV - because it's a better financial outcome.

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They can tell if you are charging a battery. Whether that is a power-wall or a Nissan Leaf, it doesn't really matter.

The power companies see this as either a threat to their monopoly in supplying power, or an opportunity to charge a tarrif.

 

Look at this scenario: 

Customer A was lucky enough to get in early & is now getting 44c/kWh for his feed-in. Because of this, he exports all his solar PV, and then every night (during peak usage time) he charges his power-wall using the grid at 21c/kWh, so he can use that tomorrow, and again export all his solar. 

Do you think the power companies like that?

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Keep in mind the cost of the electricity I produce with my solar PV is ~5.5c/kWh (over 15 years).

The lowest off peak controlled load tariffs in the nation are twice that, peak tariffs are an order of magnitude higher. Even the lousiest feed in tariffs are higher and I can access FITs that are 3-4 times that.

So at the moment, my cost of electricity production is so low that all charging me more for a specific electricity supply does is improve my ROI and cause my to divert more of my excess production to whatever is using the highest tariff.

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2 minutes ago, Ex-Hasbeen said:

Customer A was lucky enough to get in early & is now getting 44c/kWh for his feed-in. Because of this, he exports all his solar PV, and then every night (during peak usage time) he charges his power-wall using the grid at 21c/kWh, so he can use that tomorrow, and again export all his solar.

No one who has installed a Powerwall will be on a 44c FIT. Or the number is tiny. The high FITs all phased out several years ago and also coincided with a time when PV systems were pretty small (~1.5-2kW).

And as soon as you make a change to your home electricity system (e.g. you want to upgrade your panels or inverter to increase the size of the system, or add a battery) the old plan and FIT no longer applies and you move onto current FIT options.

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If the power companies hate solar PV and batteries so much, then why do all the major power companies sell domestic solar PV and battery solutions? Indeed some (e.g. AGL) offer integrated virtual power plant options with battery installation.

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3 minutes ago, Alex Simmons said:

No one who has installed a Powerwall will be on a 44c FIT. Or the number is tiny. The high FITs all phased out several years ago and also coincided with a time when PV systems were pretty small (~1.5-2kW).

And as soon as you make a change to your home electricity system (e.g. you want to upgrade your panels or inverter to increase the size of the system, or add a battery) the old plan and FIT no longer applies and you move onto current FIT options.

OK, replace powerwall with Nissan Leaf.

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Just now, Ex-Hasbeen said:

OK, replace powerwall with Nissan Leaf.

Same deal - a special high current charger for a battery system will require connection approval. If you are just using a regular powerpoint outlet with limited current draw, I very much doubt they could possibly know what you've plugged in.

Say it's the afternoon I come home and my solar PV has 2kW spare capacity and I plug the car in to a powerpoint and it draws 2.4kW (~10A max on the power point). How on earth is a power company going to know the 400W I'm importing is going to an EV battery?

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