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Forum Index : Solar : Oversize panels

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Haxby

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Joined: 07/07/2008
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Posted: 11:19pm 16 Sep 2020
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So the regulations say you can oversize your solar panels by 130% to your inverter but I wonder what practical limitations there are in the inverter that limits this figure....

Say you had a 5kw inverter and two X 5kw strings of solar facing east and west. Diode coupled. Would the inverter care?
 
Warpspeed
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Posted: 11:23pm 16 Sep 2020
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I have a 1.2Kw east, 1.2Kw west, virtual tracker system.
Never see more than 1Kw, but its there constant from sunrise to sunset.
Cheers,  Tony.
 
Solar Mike
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Posted: 01:48am 17 Sep 2020
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  Haxby said  So the regulations say you can oversize your solar panels by 130% to your inverter but I wonder what practical limitations there are in the inverter that limits this figure....


Where does it say that in the regs, I don't remember reading that anywhere, NZ regs are same as AU. If your PV controller device has current limiting management, then I cannot see any problem, as Warp says you just get a constantly higher average output.

However if its a cheap cloned device purchased on EBay, then you probably will have a problem increasing the input power capability; something will blow up, catch on fire and possibly burn your house down... 130% overload!! most of the Chinese stuff will self destruct at <100%.

Mike
 
Davo99
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Posted: 01:24pm 18 Sep 2020
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  Solar Mike said  
Where does it say that in the regs, I don't remember reading that anywhere,


It's pretty common basic knowledge here. Wouldn't have a clue what chapter and verse it is out of the solar rules and sing song book, but it's there somewhere in the current regs here at least.  They usually specify it as 33% over inverter capacity which is the same thing. This is why here the standard current system is 6.6 Kw of panels on a 5 Kw inverter. Pretty much what every Vulture is selling these days or multiples of the 33% allowance.



  Quote  So the regulations say you can oversize your solar panels by 130% to your inverter but I wonder what practical limitations there are in the inverter that limits this figure....


I am currently running 5 inverters on a number of arrays and strings and ALL of them are over clocked. Some of them were a tad over doubled, but that was when I had less inverters.
Never had a problem with it ever.

I am running OEM installed, previously certified GT inverters of Different Flavours, never touched any Fleabag type Chinese stuff so can't comment on that.
On the inverters I have used ( and that's a fair spread now) as long as you keep the VOLTS within limits, they just take the amps they want and ignore the rest.  Never seen one trip out on over input current yet. I did last summer get some of those "Y"  splitters and put about 16 Kw down a 5 Kw inverter and it didn't seem to care. Only experimented with that a couple of days when I was playing around but if that didn't kill it, I don't think anything would  as long as the VOLTAGE is within spec which I always try to keep at least 100V margin on.

Few months ago I sold a Guy a Kilo of panels to add to his existing array.  5 Kw on a 5 Kilo inverter. He'd noted the thing very rarely made full power and that the current installs were all 6.6 on a 5 Kw inverter.  He came back and bought another 5 Kw of panels and a 4 Kw inverter yesterday and he spoke at some length how adding the extra kilo of panels had a disproportionate effect on his total power generation. O)ne thing he'd noted was that the inverter was never kicked in when he walked past it to go to work. soon as he put the extra panels on he noted it had already made half a Kw at the same time . The rest of the ramp up was much faster as well and the daily totals of the same inverter went up significantly and over and above the multiplication of the KW he added.

Overclocking simply lets the inverter kick in earlier, make full power longer and trail off a lot more gradually. I came to the conclusion some time back, the real money isn't in the max power which is pretty peaky anyway, It's getting the earliest, fastest ramp  up and the longest, slowest wind down.  It's the non peak times you make the real money in solar.

My other axiom is there is no substitute for square inches and in the crappy weather where you will never get near peak power, having more panels simply makes more power from what is available.

Couple of Days ago my 5 KW inverter that's connected to 8.? Kw of panels  made 38.2 KWh.  I thought the summer multiplication factor was only 6x the inverter rating but this is a LOT more than that. I can only put it down to the over clocking which means the thing is making over 3Kw by 9am  and the fact that 3kw of panels feeding into it is west orientated with the other being north. I haven't even got those arrays split on the trackers either. The 3 Kw goes into the same tracker as one of the north arrays.  Supposedly a No No but if I had 20 bux for every solar " Rule" I have not only broken but in many occasions found a load of bunk, I wouldn't need to put panels on my roof!  :0)

I will say that I keep the Voltage of the arrays close even if the power is different. I don't know the principals involved but I have a few times now Connected dis similar arrays on the same tracker and that leads to a power REDUCTION.  Maybe the high voltage array is trying to drive the lower voltage one? I though the diodes would stop that but definitely something goes on.
Panels make full voltage in pretty poor light, they just make no amps.  If I have one array North that's making good power and another west which is making full volts but no relative power ( as I have a setup now) doesen't seem to worry. In the late afternoon when the west array is doing the grunt work, I can unplug the north array and the power only drops very slightly. Definitely not a drag on the output like uneven voltage arrays are.

Now, despite being a fan of overclocking, I have also discovered that there is a point of Diminishing returns and having the arrays matched over multiple inverters will at certain points make you more power for the day.  Going double inverter capacity is probably overkill and in effect somewhat wasteful and you would do better putting at least some of that load on another inverter that won't clip at any time.

There are provisos to that too of course.  Firstly, inverters are generally much more exy than panels, new or used. The more you can get out of each inverter the better the investment I think.
Secondly, there are limits to how much power you can push down a cable. I put in a HD circuit  just for my inverters and I maybe should have gone bigger than 6MM but then again, I'm just obsessed and there is no point as I make more than I use now ( and don't get any FIT). If I have say 6 Kw ea on 2x 4KW Inverters, I'm within the cables power capacity and they can pump that all day and I'm fine. They will ramp up faster and fall off slower and never exceed my cables power capacity or give me too much voltage rise.

If I put that same 12 Kw of panels on say 3 inverters of 4Kw each which would be rated capacity, I believe they would kick in slower in the morning as they would take longer to hit start up voltage, they would fall off earlier for the same reason and in the middle of the day I'd be blowing say 10 KW down my cable which would give voltage rise and capacity issues and at the end of the day, even if the inverters didn't trip out on high voltage, I still don't think i'd make much more power.
In reality, with the voltage rise knocking the inverters into a restart sequence as would certainly happen for peak hours, I guarantee Id make less total KWH with 3 Inverters at rated capacity than 2 Inverters over clocked.  

Of course not everyone is a lunatic like me, but bound to be someone else out there that this would apply to.  

Overclocking  the inverters means I can effectively get more out of that inverter while not over loading the circuit or getting too much voltage rise which seems much more predominant when using 2 Inverters  even doing the same output as one.  Don't ask me how that works but I have seen it in many of my muck around.

I'm re doing my setups now getting rid of all my sub 250W panels and upgrading with a load of new panels I bought very Cheap that have fallen off the CEC list and standardising with the heap of Inverters I also got that are off the BS registered list as well.

I reckon with the new setups I'll go for about 50% over clocking and vary that as I need to in panel numbers and layout. Some may be a little more, some a little less but that's the target number I'll aim for.

That will give me good efficiency in each inverter and still stay within the current limits of my main circuits.
 
Georgen
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Posted: 09:03am 21 Sep 2020
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There is probably another good reason to overclock the inverter.

Solar panels age gradually and loss is about 0.5 to 0.7 % per year.
Even if it is only 0.3 %, after some time panels set exactly to inverter size will not provide full power, so future proofing makes sense.
George
 
Davo99
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Posted: 10:10am 22 Sep 2020
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  Georgen said   so future proofing makes sense.


What you say makes sense on face value but I am always very suspect about the whole solar longevity thing.

In relation to panel warranties when purchased, many have 20 and 25 Yr warranties now.
I think that's far more a marketing Gimmick than any actual value to the customer.

Average home owner does not stay in a place near that long. Most warranties are not transferable to the new owner.

-I- won't be here in 20 years to worry about them and If I am, Damn sure I'll have better things to worry about.

If a panel or 3 does down, what are you going to do? Surely won't be able to get a replacement panel, Regs now state they must be exact match or they all have to be replaced. only solution is to give a refund on the price of the panels which will still leave you with a sub outputting system that may cost more in the longer term than the refund.  That's why you invest in the things in the first place, because you get more out long term than their cost and therefore make a saving.

And lastly, panels have been popular, what? 10 years on average now and look how many systems are being replaced already  A year ago I was getting 250W panels as the higher end output on the used market.  Last week I bought a load of new 275's, some used 285's and today I bought some new 400's and some used 360's. I bought a system off a guy a couple of weeks ago that was 2 Yo but due to having a tree drop on the roof that didn't touch the panels, The whole roof had to be replaced and taking the panels off and replacing them wasn't allowed because they were already off the CEC list and couldn't be refitted. Insurance covered the roof and the solar and the guy chipped in the difference and got a 10 Kw system.

Don't get me started on the wastage on that If I hadn't got them and how that eats into all the environmental BS of throwing away a perfectly good resource hungry product like that so early in it's life cycle.

I was planning to standardise on 250s but I still haven't got rid of all the sub 250s and I'm now looking at making at least 275's the benchmark.

To think people will still have 360's or whatever the standard is now on their roofs in even 15 years time I think is a real stretch.  They may have picked up another 10% in efficiency by then and the bigger issue is not the panels, it's the reason why most systems are replaced now and the weak link in the chain.... Inverters.

Good chance they will go another way with inverters, maybe higher voltage inputs for lower amps or who knows but there is a good chance they won't be physically compatible even if as now they aren't legally compatible.

I can see a LOT of systems being replaced far before their BS warranties run out that's for sure.  I have seen on forums MANY times where people pick a more expensive panel because it has 25 Yr warranty where the cheaper panels " Only" has 2.

I know which one i'd go for..... The ones I get which have NO warranty and in my considerable experience now, have a surprisingly low failure rate anyhow.
 
Georgen
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Posted: 10:09am 25 Sep 2020
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Davo99, I cannot argue with your points.

Part of the problem are regulations, sus warranties and still changing solar industry.
360W panels or possibly larger in the future sound scary to me.
I'd rather have 180 or 200 ones as easier to handle, probably stronger against hail storm, but I am probably wrong.

What we really need are inexpensive and long lasting batteries.
George
 
Davo99
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Posted: 11:25am 26 Sep 2020
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I have put up an array of 360's and 420's? I think they were. Thread on it with pretty pics here somewhere. I too was pretty wary of these 2M monsters but I have to say I didn't really have any trouble with them. I certainly thought I would and procrastinated for 6 Months on how I was going to put them up but in the end I Completely over thought the project and over estimated the difficulty.
you certainly need a lot less of them to get the total output.

The 14 400's I got this week add up to 5.6 Kw. That would have been 22+ panels in 250's. So many less connectors to hook up, panels to clamp down etc. They are also putting the leads oin the middle of the larger panels now instead of one end. I can see installation advantages in that for sure. Still not long enough to loop on the end and eliminate the return wire but anyway.

You may well be right about strength, they aren't that much heavier than the 250-280W panels which are around 17-19 Kg but then again,. they are only about 4-450mm longer and the same width.

The drawback I see with the longer panels is along roof ridgelines.  Where the roof comes down at an angle you have to go further back into the main part of the roof  to clear.  You could easily have put a shorter panel in the gap and be on your second panel across in the same space.

I think the idea of the bigger panels is like everything else, speed of and therefore cheaper Installation. The load of 400's I picked up the other day JUST fitted in the trailer on the pallet they were strapped on. For a minute I thought I was going to have to take them off and stand them up which wasn't an appealing thought given the distance I had to go. 250's I just stack in the back of the ute and all is good.
I can also stack them lengthways across the trailer and get 2 piles in.

Might have too look for an 8 ft trailer to be sure and one with brakes so I can carry a decent amount of the things. Standard pallet of 27 of these things was 630Kg. That's overweight for a non braked trailer here ( 750kg all up WITH The trailer)
and I just don't like towing unbraked heavy loads.  Last trailer I  built I put brakes on it even though it was a business trailer and well underweight but I NEVER regretted spending the extra and doing it. Car and trailer stopped on a dime and I never had to worry going down the hills in the mountains where I often went.


I have a really nice set of used 195W panels I picked up the other week and those things are LIGHT! I suspect they are a bit on the cheaper made side or very high tech because all the other 190 or so watt panels I have are much heavier. Every time I pick these other ones up I nearly throw them in the air.

I have some 225W " Solon" brand up there which are made in Germany... From Recycled panzer tanks I think.  They are 23kg, at least 5 Kg heavier than comparable chinese panels. They are 40 mm thick instead of the more common 35 and I think the extra depth is all armoured glass. I know I'm not getting any younger but I feel that extra 5 Kg when I pick them up. The others don't worry me but those ones... Quicker I sell the rest and get back to the lightweight ones the better!


Yeah, batteries are the holy grail of everything renewable, green and electronic / electric atm. I don't see them making any giant advances in the near future and I sure as hell don't see them getting cheaper as people talk about all the time, quite the opposite.

There are a lot of arguments they will but I base my prediction on simple market forces.  There is HUGE demand for batteries now, manufacturers are struggling to get adequate supply as it is. Demand will only continue to grow Quickly and constantly and nothing in high, increasing demand gets cheaper once the initial manufacturing cost has been sorted as it has now. If things kept getting cheaper the more the demand, then fuel would be given away.  Normal lead acid batteries Go up every time I go to buy one for my cars and they have been making tens of millions of those for decades.

To make batteries financially Viable even where we have the most exy power in the world, their price would have to fall by 80%. That's just not going to happen while I'm still on top of the ground or I doubt while my Daughter is either.

Of course batteries like everything else in the green/ renewable ideal are completely over blown. It's nothing in Sydney to get a week of overcast, dull weather and it's not practical at any time in the forseeable future to have enough batteries to go that long for either a home or a gird scale. In places like Melbourne... not even worth thinking about.

I have more panels than any sane person would have and not very many on average would have room for anyway.  I have seen how just in this month alone, I can go from making 85 Kwh a day one day to barely making 12 a day for the next 3 days in a row.

You still have to be able to charge batteries up. They are only storage not generation and when your generation isn't working for any length of time, batteries are useless.


I will say it will be extremely interesting to see how the grid and power prices evolve. Already Off peak at night is actually  the PEAK time for the generators.
Solar takes a lot of the weight off generators ( much to their dislike) through the day and the demand from generators actually ramps up at night. You can see that on the AEMO site that tells you what the demand is, the wholesale price and how it's being generated, coal, gas, solar etc.

There is a lot of talk by those whom are actually quite ignorant about charging electric cars with cheap off grid power at night. Boy, are these people going to be in for a surprise! The power cos are all spinning the BS that Renewable power is cheap and investing in primarily solar. When that generation source is inoperative at night and all the sudden every second house in every street goes from sucking down a max of 4 KW with their water heater to 20 Kw with their car charger, How cheap do that think that night time power is going to be?

I have seen some say that they will charge their home battery during the day and use that to recharge the Vehicle.  Again blind ignorance. Firstly, how big a battery do you have? Secondly, how big a roof you have to put how many panels to charge said battery with enough power to charge your vehicle.
All the new houses they are throwing up round here ( and it looks like someone threw up with their design) are squashed onto tiny little piss-ant blocks and are double story because the home floor space exceeds that of the block they are on. Obviously the roof space is limited as is the useful direction and area of the roof one could put panels on anyway.

I think battery are exactly like New revolutionary Car engines I have been reading about for the last 50 years since I was a kid.  Something the size and weight of a sewing machine, delivers 300Hp and uses 1l Of fuel per 100 KM. Yep, been " Just around the corner" for 50 years or more now and they haven't even come close. About all they have done is improve the engines going back to the '50s power and consumption a PERCENTAGE ( 10-20?% ) and the progression with batteries will be similar despite tech advances.

Comes back to Physics now and I don't expect to see anything making leaps and bounds in larger capacity and lower prices for at very least 20 years and that's about as far ahead as I expect to be around!  :0)
 
Georgen
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Posted: 12:18am 27 Sep 2020
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There is another storage proposition.
400 degrees C oil or something like that.
Oil that uses steam powered turbine to produce electricity.

Again, insane investment with no way to have it large enough to store enough energy for cloudy, miserable, or dusty days.

I know that coal, gas, oil are finite resources and we have to find an alternative sooner or later, but we should not blow up coal powered power station and then have all the trouble SA had.

Suppose price of battery might be always high, but life expectancy of power storage of 100 years or at least 50 would be a good start.
And nothing comes close except for low efficiency Edison battery.
George
 
Davo99
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Posted: 09:18am 27 Sep 2020
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Hadn't heard of the oil one but I can see problems with that just by the minimal description. Oil is only .8 roughly the density of water so although the temp could be much higher ( although oil would be at self ignition temps at 300 and 220 would be about as high as you'd want to go to prevent vapour problems) You would need a LOT of it and water so I can well see why it would be expensive.

That's the trouble with pretty much any storage system. The energy density is VERY low compared to that of Liquid Fuels especially.

As for finding an alternative, I agree but it seems so many of these ideas are touted and even put into use simply to meet an agenda, not because they offer any benefit over the current way of doing things.  I have seen MANY of these hair brained ideas ( Biodiesel being one of them)  That take more resources, more energy input and create more emissions than what they save.  And without exception, they are NEVER renewable because they can't exist or support their own production without Fossil fuels in their creation somewhere along the line.

If there is no viable alternative to FF atm, then we should just live with that and keep doing R&D until there is.  All this unreliable energy hoo haa is really just making things worse for the reasons I mentioned, that at the end of the day they  need more energy input and create more emissions than what they save and they are not a practical solution at all. Neither are so many other hair  brained ideas.

We just need to be content till we do find something practical and not squander the resources we have on things that are clearly better at conning people and gubbermints out of money that solving the actual problem at hand.


I have heard endless times laughable and ignorant BS where people say " We have to do first generation trials to improve future generations of the technology.

What a Crock!
Computer modelling and all sorts of Data will let you know if a Fighter jet is going to fly and what it's performance will be before you build the thing. You don't need to crash planes to make the next one better.
Power generation is a walk in the park compared to all sorts of everyday things that are made now.  The main reason these stupid ideas come to fruition are to attract Investment and Gubbermint grants.  Doesn't now matter if they actually achieve a net energy benefit, as long as they attract MONEY.


I Imagine there is Billions being poured into battery research right now.  Whoever comes up with the breakthrough on that will make money unseen or heard of before.
Unfortunately, like cancer research, all that money does not mean a breakthrough will be forth coming.
 
Murphy's friend

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Posted: 09:37am 27 Sep 2020
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  Davo99 said  


Computer modelling and all sorts of Data will let you know if a Fighter jet is going to fly and what it's performance will be before you build the thing. You don't need to crash planes to make the next one better.


I disagree, too many variables that computers cannot pick up.

Why do you think they use crash dummies and actually crash cars to see if the dummy had a chance to survive.
With fighter jets is a little different, usually its curtains for the pilot if the plane hits something or falls out of the sky. BUT they do test the ejection seats...
Planes (and ships) are also tested in wind tunnels (or test tanks) so at least a scale model needs to be built for that.

You might be willing to hop into a new car solely designed by computers & manufactured by robots - I don't. Much prefer to have a test driver sort out any problems first and  the car has passed all the crash tests as well.
 
solarwind

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  Davo99 said  
  Solar Mike said  
Where does it say that in the regs, I don't remember reading that anywhere,


It's pretty common basic knowledge here. Wouldn't have a clue what chapter and verse it is out of the solar rules and sing song book, but it's there somewhere in the current regs here at least.  They usually specify it as 33% over inverter capacity which is the same thing. This is why here the standard current system is 6.6 Kw of panels on a 5 Kw inverter. Pretty much what every Vulture is selling these days or multiples of the 33% allowance.



  Quote  So the regulations say you can oversize your solar panels by 130% to your inverter but I wonder what practical limitations there are in the inverter that limits this figure....


I am currently running 5 inverters on a number of arrays and strings and ALL of them are over clocked. Some of them were a tad over doubled, but that was when I had less inverters.
Never had a problem with it ever.

I am running OEM installed, previously certified GT inverters of Different Flavours, never touched any Fleabag type Chinese stuff so can't comment on that.
On the inverters I have used ( and that's a fair spread now) as long as you keep the VOLTS within limits, they just take the amps they want and ignore the rest.  Never seen one trip out on over input current yet. I did last summer get some of those "Y"  splitters and put about 16 Kw down a 5 Kw inverter and it didn't seem to care. Only experimented with that a couple of days when I was playing around but if that didn't kill it, I don't think anything would  as long as the VOLTAGE is within spec which I always try to keep at least 100V margin on.

Few months ago I sold a Guy a Kilo of panels to add to his existing array.  5 Kw on a 5 Kilo inverter. He'd noted the thing very rarely made full power and that the current installs were all 6.6 on a 5 Kw inverter.  He came back and bought another 5 Kw of panels and a 4 Kw inverter yesterday and he spoke at some length how adding the extra kilo of panels had a disproportionate effect on his total power generation. O)ne thing he'd noted was that the inverter was never kicked in when he walked past it to go to work. soon as he put the extra panels on he noted it had already made half a Kw at the same time . The rest of the ramp up was much faster as well and the daily totals of the same inverter went up significantly and over and above the multiplication of the KW he added.

Overclocking simply lets the inverter kick in earlier, make full power longer and trail off a lot more gradually. I came to the conclusion some time back, the real money isn't in the max power which is pretty peaky anyway, It's getting the earliest, fastest ramp  up and the longest, slowest wind down.  It's the non peak times you make the real money in solar.

My other axiom is there is no substitute for square inches and in the crappy weather where you will never get near peak power, having more panels simply makes more power from what is available.

Couple of Days ago my 5 KW inverter that's connected to 8.? Kw of panels  made 38.2 KWh.  I thought the summer multiplication factor was only 6x the inverter rating but this is a LOT more than that. I can only put it down to the over clocking which means the thing is making over 3Kw by 9am  and the fact that 3kw of panels feeding into it is west orientated with the other being north. I haven't even got those arrays split on the trackers either. The 3 Kw goes into the same tracker as one of the north arrays.  Supposedly a No No but if I had 20 bux for every solar " Rule" I have not only broken but in many occasions found a load of bunk, I wouldn't need to put panels on my roof!  :0)

I will say that I keep the Voltage of the arrays close even if the power is different. I don't know the principals involved but I have a few times now Connected dis similar arrays on the same tracker and that leads to a power REDUCTION.  Maybe the high voltage array is trying to drive the lower voltage one? I though the diodes would stop that but definitely something goes on.
Panels make full voltage in pretty poor light, they just make no amps.  If I have one array North that's making good power and another west which is making full volts but no relative power ( as I have a setup now) doesen't seem to worry. In the late afternoon when the west array is doing the grunt work, I can unplug the north array and the power only drops very slightly. Definitely not a drag on the output like uneven voltage arrays are.

Now, despite being a fan of overclocking, I have also discovered that there is a point of Diminishing returns and having the arrays matched over multiple inverters will at certain points make you more power for the day.  Going double inverter capacity is probably overkill and in effect somewhat wasteful and you would do better putting at least some of that load on another inverter that won't clip at any time.

There are provisos to that too of course.  Firstly, inverters are generally much more exy than panels, new or used. The more you can get out of each inverter the better the investment I think.
Secondly, there are limits to how much power you can push down a cable. I put in a HD circuit  just for my inverters and I maybe should have gone bigger than 6MM but then again, I'm just obsessed and there is no point as I make more than I use now ( and don't get any FIT). If I have say 6 Kw ea on 2x 4KW Inverters, I'm within the cables power capacity and they can pump that all day and I'm fine. They will ramp up faster and fall off slower and never exceed my cables power capacity or give me too much voltage rise.

If I put that same 12 Kw of panels on say 3 inverters of 4Kw each which would be rated capacity, I believe they would kick in slower in the morning as they would take longer to hit start up voltage, they would fall off earlier for the same reason and in the middle of the day I'd be blowing say 10 KW down my cable which would give voltage rise and capacity issues and at the end of the day, even if the inverters didn't trip out on high voltage, I still don't think i'd make much more power.
In reality, with the voltage rise knocking the inverters into a restart sequence as would certainly happen for peak hours, I guarantee Id make less total KWH with 3 Inverters at rated capacity than 2 Inverters over clocked.  

Of course not everyone is a lunatic like me, but bound to be someone else out there that this would apply to.  

Overclocking  the inverters means I can effectively get more out of that inverter while not over loading the circuit or getting too much voltage rise which seems much more predominant when using 2 Inverters  even doing the same output as one.  Don't ask me how that works but I have seen it in many of my muck around.

I'm re doing my setups now getting rid of all my sub 250W panels and upgrading with a load of new panels I bought very Cheap that have fallen off the CEC list and standardising with the heap of Inverters I also got that are off the BS registered list as well.

I reckon with the new setups I'll go for about 50% over clocking and vary that as I need to in panel numbers and layout. Some may be a little more, some a little less but that's the target number I'll aim for.

That will give me good efficiency in each inverter and still stay within the current limits of my main circuits.


It's like using a truck battery to start a motorcycle. As long as the VOLTAGE is within the safe maximum for the inverter, it will only take what it needs. The advantage is that you will have enough pv power from dusk till dawn, summer or winter. I've had, for example, 18 x PV modules on my Imeon 3.6 without any problems.( 9 facing North nd 9 facing West, so from midday on, both arrays produced power).
You don't have success until you've tried it!
 
Davo99
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  solarwind said  
It's like using a truck battery to start a motorcycle. As long as the VOLTAGE is within the safe maximum for the inverter, it will only take what it needs. The advantage is that you will have enough pv power from dusk till dawn, summer or winter.


Yep, exactly Right.

I have been experimenting with one of my inverters for a couple of weeks.
I had it (5kw inverter)  hooked up to a 6.2 Kw North array and a 2.5ish KW west array.  Couple of weeks back I was pulling 38-39 Kwh out of it which I thought was pretty much too good to be true.

I took the 2.5 Kw array off and put it on another inverter it's own.
The 5 Kw has dropped to around 32-33 Kwh a day. Even though it's still over clocked, having it even MORE overclocked did make what I would say is a respectable difference.

The inverter the 2.5 is now hooked to ( 4kw) is making on average about 10 Kwh a day.
That's not the same multiplication factor as what the overclocked inverter is getting But that is most likely due to the different orientations.

Yes, having them separate does make more total Power but not all that much.
The thing one would have to really consider I think would be what would the extra power/ difference, call it 4Kwh a day total, take to repay the cost of the additional Inverter? Not cost effective I'd say unless one has spare inverters lying around and the wiring capacity to hook them into that will take the increased Peak power.
I'd suggest my observations at this time are close to a best case scenario. I doubt the difference would even be that in the winter.  The 2.5 On the west array would probably take till 10 Am or later to kick in and then would be pretty lethargic most of the day where as putting it with the other inverter I think that array would kick in more over all than on it's own.

I'm sure with a little testing and tweaking one could find the sweet spot where the over clocking made the same power  or maybe even more than having the extra panels, whatever they worked out for that particular installation, producing the same power as having the extra inverter with them at rated input.

Even though I am a fan of over clocking, I was thinking a bit about my new setup and if I was wasting TOO much power.  This little experiment has been enlightening and looking back through my daily records, I see that in winter when I most need the power, even with significant overpaneling, The inverters don't often max out and if they do, it's not for long. seems there is Plenty of margin to over clock them in winter and loose very little power.

In summer I'm making stupid amounts of power I can't burn for trying so it's really irrelevant, as much as the inefficiency Niggles at me. I have plenty of spare inverters so the cost isn't the problem atm but the thing for me would be I am simply going to run out of wiring to back feed any more peak power I really don't need anyway.  Put in 6mm 3 phase and that's at it's limit now and I can't burn the 90 odd KWh i'm making right now anyway. For me it's better by far to be running max capacity for as long as possible than having to wire up for more Peak capacity which won't add a lot to the daily totals when I need it anyway.


When I change over to all the new/ larger panels I have, I think something around 50% over rating the inverters will be work pretty well for me. I will pay a bit more attention to the arrays not so much voltage as I'm aware of anyway ( and I will try to keep as even as possible to make configuration with different inverters easy as Possible) but to hit that target with the tracker capacity.

Kicking the inverters in early and having them drop off late is the key as I have discovered a while back.
 
Davo99
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Posted: 10:02am 04 Oct 2020
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  Murphy's friend said  
  Davo99 said  


Computer modelling and all sorts of Data will let you know if a Fighter jet is going to fly and what it's performance will be before you build the thing. You don't need to crash planes to make the next one better.


I disagree, too many variables that computers cannot pick up.
Planes (and ships) are also tested in wind tunnels (or test tanks) so at least a scale model needs to be built for that.

You might be willing to hop into a new car solely designed by computers & manufactured by robots - I don't. Much prefer to have a test driver sort out any problems first and  the car has passed all the crash tests as well.


I agree with what you are saying but I think the analogy is a bit off.
There is nothing like the complexity in solar or wind as there is in something like a vehicle.

In any case, they could easily build a scale model of a wind or solar farm and test that without having to build Dozens of the things in real life to test them and then they could build a single working test facility. That would tell them all the need to know before they build a whole bunch of the things that don't come near the promised performance.

I believe from what I have read many times, On average, Wind farms around the world produce only 13% of installed capacity.

I don't believe you even have to build a scale model to see that great a difference between touted generation and real output. In any case, these thing weren't all built and commissioned on the same day they must have bloody good idea with many of them what the real output is likely to be.

The RE industry has mountains of real world data and research on hundreds of facilities now that there is zero guesswork in anything existing and a lot of that would carry over to anything new.
 
Davo99
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saw something interesting today.

Couple of days back I hooked some more arrays into my 5 Kw inverter.  I believe it now has 10-12 Kw of panels going into it. Can't remember what each array is now but suffice to say it's significant.

Today I saw that 5 kilo inverter do a total output for the day of 42 Kwh.
My 4Kw inverter with I have no idea what is on it, today did 28 Kwh.

I thought 6X was the summer output calculation but both these are far above that. The 5Kw is 8x + and the 4 Kw is 7X. Maybe that rule of thumb is for inverters loaded to capacity, not double?

The 5 has north and west panels on it, the 4 west only.

I'm wishing I had an east array now. It would be very interesting to put say 3 lots of 6 Kw of panels  north, west and east and try and work out what the absolute max  one could get out of a single inverter would be.

I have 5.6Kw of 400 w panels to put up. I might try a ground setup for a few days with them and hook them in and see what happens. They might kick the average up for the first 2-3 hours of the day. Beyond that the inverter would max out and they would probably contribute nothing  but would be interesting to see the difference just the same.  Finding a clear unshaded spot in the yard for that direction before the north panels really kick in would be the trick here.

Going to add a lot of panels to the west roof so that should still be producing power well after sunset.
 
Georgen
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Posted: 09:54am 10 Oct 2020
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Sounds fantastic.

Sure, somebody might say that with more inverters you could have more power, but yours is rather almost scientific approach to put sh*tload of panels on inverter and see what happens.

When panels were very expensive trackers were better option.

Now with so many inexpensive panels available surely more panels are better option.

Appears that it doesn't matter if panels are perfectly matched and now with your experiments appears that you almost cannot kill overloaded inverter.

Interesting if it has to be inverter produced by super reputable company, or any inverter can be pushed well into forbidden territory?
George
 
Davo99
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Posted: 11:31pm 10 Oct 2020
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From what I have read, the inverters I have are no where near Reputable, more towards the " questionable" Side.

The 5 Kw is a Delta Solivia .  The 4 Kw is a JFY. A brand I have read lots of bad reports on.  I got them used like everything else although I did Buy a Bunch of New JFY's some months back and they seem a simple but decent enough inverter. I also have a 3.6 Kw Auroura on the shed which was definitely a questionable brand. I got a load of those years ago when they were dumped as brand new old model stock.

I have burned through about 4 of them already. They seem pretty weak BUT, the one in the shed has had about 5.5 Kw of north facing panels on it for about 3 years now and seems OK.  I also had a Bosch on the house and they also were supposed to be questionable and were pulled out the market and that was well over clocked and was fine. Just replaced it with the delta because it was bigger.

Just looked at the delta and at  8:15 am daylight savings time, It was only doing 315W. It's a beautiful sunny morning here but I doubt ANY of the panels it is connected to would be getting direct sun as yet.  They are north east and west facing and would still all be below the ridge line of the roof and only getting open shade.

Sitting here looking at the back at the bright sun hitting the yard, I'm Certain that having an east facing array would bump the output a good amount of KW. I can also see with the still low sun angle that my Biggest tree in the whole District as deemed by the council that is in the front yard is shading a good amount of the back yard still.

Getting 5 Kw of panels in the sun now would mean stacking them about 3 Wide in rows behind one another to avoid the shading. Pain in the butt to wire up just for testing.  Not to say I haven't got all sorts of pre made cables I have used for other temp setups. Looking at it though, If I had a 5 Kw array going east, I don't think it would be hard to get that inverter into the 50Kwh range for the day, 10X inverter capacity.

About 8:40 and I can see the sun has just started to clip the north array. It's hitting them at a directly sideways angle and the inverter has climbed to 1200W and Rising as you watch it. still a lot of shading going on the top string particularly  so output should rise quickly as soon as that clears.  I reckon a 5 Kw array due east would have to be pushing 2.5-3 Kw at least now being in direct in the sun.  That should easily give those extra KWh before the inverter maxes out on the north array  to hit 50. The west panels are still all covered in due and the other inverter is not even doing 250W yet.  A north array on that one would make a HUGE difference.

Gives rise to some thought.
The limits the power cos have is generally the 33% over paneling of an inverter and a 5 Kw inverter for single phase.  With the smart meters they can see if you hooked in another inverter and were making over the 5 KW.  If one had the opportunity with roof/ shed space, the idea I had of putting arrays of even say 5Kw in 3 Directions could produce a LOT more power than a single direction array but the beauty would be that the max output would never be above 5 KW. It would be the same as having 5 Kw on a tracker really but a lot more practical.

 One would also get the benefits of a more consistent generating throughout the day, the inverter would be maxxed out probably 80% of daylight hours certainly in summer and with more panels one would make a lot more power on the crappy days as well.  The fall off would be made up a lot for by the non directional lighting and the large array size even if it was doing very low efficiency.  If one could produce say 2.5 Kw and do it all day in overcast weather, that wouldn't be a bad result at all!

I think this is an interesting and valuable observation. I get people asking me about adding panels all the time and how onto it the power cos are.  Having a tri directional array seems a good way to maximise power without having to worry about overly high peaks, over loading the  wiring ( or putting in another circuit) or Questions from the power co as to why ones 5 Kw system was producing 10 at lunchtime?

If they were on the ball and monitored anything one might get asked why the system was maxxed out from 9am to 7:30 Pm in summer but you could tell them you had a tracker and nothing says you can't do that I have seen.  Might be a council  issue but can't see it being a power co infraction.  Like I'd care anyway.

For the off Gridders this would be a great way to go.  As said, panels now particularly Used are so cheap and getting the max constant generation over the max peak input is the trick.

9 am now and the inverter is pushing 2300W. Backyard is Mostly clear and I reckon that 5 Kw imaginary east array would be doing 4 Kw at least. That extra would definitely push the output to 50 Kwh for the day.  Maybe the idea would be to put it on wheels so once the inverter maxed out on the north input I could turn it west for the afternoon  fall off.
 
Georgen
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Davo99 how do you handle voltage of the strings?
Is it tricky issue?

Does it depend on temperature as well?
George
 
Davo99
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Hi George,

Not quite sure what you mean handle the voltage. If I miss the explanation, feel free to spell it out for the Dummy! :0)

If the strings of panels are within acceptable voltage individually, You can PARALLEL 2, 10 or 50 of them and they will still be Ok.
To that end I have those 4 into one connectors which parallels the strings.

I do try to keep all my strings the same number and size panels and where I have put different size panels, I try to keep the voltage as close as possibly to the other strings even if The panel numbers may be different. My Big 360 and 410 Panels  work out at the same voltage close enough and they are enough to full a tracker ea anyway.
All the others I have come in at around 380V open circuit. I have labeled the different strings with the voltage so I know which ones can go together.

The voltage between strings isn't  critical but it helps to keep the strings within about 10% I have found. Even when I have run strings of the same panel, there are small differences anyway. The panels have an open and a pulled down voltage so they tend to even out small differences anyway. Some strings will float a bit higher and some a bit lower and the inverter is moving them up and down all the time anyway. I can easy see my inverters moving 10V+ on the DC side as the trackers hunt around.  The difference's even out in the end even if some may not be at the most efficient output. Till now I have been using mostly Used panels so there is a bit of variation on all the numbers to start with.

I have seen much written about temperature but I can't say I have seen much effect on the panel voltage. Can drop the WATAGE a fair bit by myself, have not seen a great difference in Voltage although not saying it does not happen.

In any case, I try to have a bit of margin which isn't hard with the panels -I- Have got so far.  10 panels in a string is still only 380V on an average 250w panel open circuit and I have found many don't do that.  I haven't had occasion ( Or room) to string more than 10 panels together so far.

I do notice the bigger 350 and 400W panels tend to be up in the 45-50V margin but as a lot of inverters are 500 to 600V, one could either just limit the strings to 8 or 10 may not be a problem anyway.  Most inverters I have seen even going back have over voltage shut down so if there were some artificially Hive Voltage, they would likely self protect anyway.  

I would think -if- an array were to clime over 100V that was in the margin due to heat, the amperage at that over voltage would not be high and the inverter should be able to deal with it.

What I HAVE seen cause voltage rise Numerous times is Cloud edge effect.  That for whatever reason tends to turn everything nuts. I have no logical reason to explain why but in my observation it also tends to send the inverters a bit screwy as well.
I have seen Very high voltage output on the AC side when the input was fairly low as was the grid voltage before the inverter hooked up .

Cloud edge from what I have seen does weird things to panels and inverters which it should have no influence on really.

This summer I want to fry an egg on a Panel. I have NO doubt that will be possible.
 
Georgen
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Posted: 06:15am 18 Oct 2020
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Looking through internet I noticed information on solar panel that Voc is for example -0.30%/deg C

What is correct interpretation of this information?

(I got impression that temperature affects maximum voltage. Minus sign means that with temperature rise voltage decreases and increases with low ambient temperature)

As to cloud effect I read that if Sun comes past cloud edge there are times when Sun rays get reflected on cloud surface and solar panel gets energy from the Sun plus energy reflected.

Could probably play with mirror or sheet of shiny white plastic to see if this effect could be replicated without cloud.
Not having to use large size mirror, experiment can be done with 20W, 40W or other smaller size panel.

Will try to find if there is U-tube film that addresses this issue.
George
 
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