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Going to resurrect this as I need some info.
Does anyone have any experience with self powered tracking arrays of PV panels? Maybe you @nta?
Obviously I want to get the most out of the panels and I have heaps of space so wondering if anyone has used them either commercially or residentially. I'm not sure what the pitch is on the new roof although it will be north facing, so might work O.K. but you can get large productivity increases with tracking.
More moving parts and maintenance, but at least it is ground level.
Dunno.
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@Snowy I don't have a lot of experience with this personally BUT I know that you've got 2 added levels of cost: ground mounting and panel tracking.
At commercial sizes - where you're ground mounting anyway, the extra cost of tracking isn't such a burden to IRR.
But for domestic users? Hmmmm... Depends on the situation.
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@Snowy trackers are very site specific. Solar in general is. Some sites you're better off cramming in fixed axis, others suit spacing them out with single or dual axis trackers. I wouldn't have thought that they'd make sense on a domestic north-facing roof though
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@voodoo said in Solar Power and Storage - a nerd's view:
@Snowy trackers are very site specific. Solar in general is. Some sites you're better off cramming in fixed axis, others suit spacing them out with single or dual axis trackers. I wouldn't have thought that they'd make sense on a domestic north-facing roof though
Not all of it is. 1930 bungalo with add ons and a complex roof structure where I could have east, north, and west facing panels which doesn't seem very efficient. I have done that one before and was looking for better solutions. I'll know more when the house is on site and I have pitch and orientation.
Maybe just fixed, but an array that isn't roof mounted? I can clean them easily too.
@NTA Is ground mounting really more expensive than roof?
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@Snowy said in Solar Power and Storage - a nerd's view:
@NTA Is ground mounting really more expensive than roof?
Typically, yes. First you probably need a geotech survey depending on local authorities. Posts and frames have to be standalone structural (maybe concrete footings etc), wind factor is different, channeling for power cable and then of course the extra cable itself. All adds up.
Of course in some cases it makes absolute sense depending on all the factors involved.
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I've seen estimates of an extra 20c per watt installed here - so AUD$8k for a 40kW system with no tracking.
But that assumes a certain size of array.
On a roof they're just battening on a couple of aluminium rails and dropping cable into the house, by contrast
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@NTA and then seeing how much work is needed to get the optimal pitch? But I guess the railing system would have scope for that to a certain extent. With the current situation we are keen to really look at solar etc, but we also desperately need to extend up and/or out. So we've kept putting it off.
Keen to hear how things progress @Snowy.
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@Paekakboyz pitch can be important - my roof for example is optimal for October/November which is great as it isn't too hot and there tends to be a lot of sun. My roof is probably around 30 degrees pitch where a lot of modern builds are 23ish.
NOTE: adjusting the pitch on the roof by adding extra framing = extra cost. If your roof isn't flat, generally go with what is there. If you're going to extend, then I'd suggest getting good passive design done at the same time including the right pitch on a north-facing roof.
Ground mounts without tracking have to determine their pitch at time of install. I've seen two general options in either single-post and rail frame like this, which looks to be about 3.0kW-3.6kW depending on panel size:
To the ground-frame ones which are an option if you have more space - the one in the picture is quoted at 28kW which would run about 4 households at peak:
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@NTA said in Solar Power and Storage - a nerd's view:
@Snowy said in Solar Power and Storage - a nerd's view:
@NTA Is ground mounting really more expensive than roof?
Typically, yes. First you probably need a geotech survey depending on local authorities. Posts and frames have to be standalone structural (maybe concrete footings etc), wind factor is different, channeling for power cable and then of course the extra cable itself. All adds up.
Of course in some cases it makes absolute sense depending on all the factors involved.
Yeah, we fit into the last sentence. None of that scares me too much, given that I have a geotech report in front of me and the engineer doing the foundations for the house will be able to design it. The guys doing the foundations will be putting in poles, so a few extras won't be too difficult. We have to get a trench dug to get cabling to the house so a few extra meters won't matter there either. Basically, we have everything to do what you describe happening anyway.
Pitch is an easy one - should be approx the same as lattitude for obvious reasons. SYD is about 33deg sth so you are nearly bang on Nick.
We are 36deg sth, so I guess the question is - typical 1930 bungalow in NZ has 15 - 25deg roof (I don't actually know what ours is yet) how much extra efficiency do I get from the optimal pitch with the extra 11 to 21deg? That seems significant to me.
If I do a ground array, do I do tracking or fixed? Two axis tracking or one?
Have to find some numbers on the efficiency gains somewhere I guess. I can probably save a bit by having fewer panels if it is optimised too, and I will be able to clean them easily on the ground.
How many KW is your system Nick? Is it enough?
I will probably go powerwall or some battery too. Had the panasonic in last house and it was good. They manufacture them for Tesla anyway I believe.
Going to need a heap out of the panels because going to buy my Dad's Audi etron too. He wants a smaller electric car so I'll buy his.
@Paekakboyz Spacecraft do indeed have solar panels for running the ship, as well as solar electric propulsion. So yes, with a little (well a lot really) more advanced tech, that is quite possible.
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@Snowy said in Solar Power and Storage - a nerd's view:
How many KW is your system Nick? Is it enough?
6.5kW of panels with a 5kW inverter - Powerwall version 1 coming up to its 5th birthday. I would consider it enough for about 75% of days, yes. Still useful to have the grid of course for rainy weeks and occasional heatwave days where the AC (an inefficient pig of a piece of shit) runs in a house with very few passive design features.
Note: make everything as energy efficient as possible (AC/heating) and you could get away with 5kW for the house. Is it just the 2 of you? If you add the eTron you're probably best off going for whatever the local authorities allow (e.g. there are 10kW limits in some parts of Australia for grid-connected systems).
Many options out there for batteries these days.
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@NTA That is what I put in at the last house. We don't get as much sun as you though and it wasn't quite enough. Also had to split the panels onto east and west facing aspects so wasn't ideal.
Yep, will still be grid connected. Yep, just two of us, but electric car, hot tub, might heat the pool a bit (probably use an evacuated tube solar hot water system for that as I have one already , so another story).
Didn't know about restrictions on output, don't think that we have that here. Will look into it, thanks.
Onto the energy efficiency. Did an eco design course a few years ago. House already has LED lighting throughout. Have organised injected wall insulation, blanket under floor, might even go up to R7 for the ceiling. New double glazed joinery throughout . Having a woodburning Rayburn or Aga with a wetback that will run radiators (suits the old house), it also has a heat pump / aircon and a ventilation system. We should have temps / humidity sorted I think.
Who else is doing batteries?
I have considered off grid, but I think we would still need to go lead acid if we did that and then I would need a generator, so went off the idea.
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@Snowy said in Solar Power and Storage - a nerd's view:
Who else is doing batteries?
So in this part of the world for lithium you have known brands like Tesla, LGChem, sonnenBatterie, Enphase, and I think Fronius do a hybrid unit. After that there is a whole heap of Chinese manufacturers entering the market.
Lead acid is always there, but the fact it is a well-known technology doesn't mean it is bulletproof. Control systems are the problem and it isn't actually a very common technology compared to Lithium, which is becoming plug n play at a rapid rate of knots.
e.g. My PW1 took the techie a few hours to wire in correctly, because the inverter hooked up to a Battery Management System which hooked up to the PW1 itself. Now they're coming as all-in-ones with an inbuilt inverter (Tesla PW2) or compatible plug tech for a wider range of inverters. Less piss-farting around.
There are also a couple of quirky options like Redflow (poorly named IMHO) ZCell - using a Zinc-Bromine (ZnBr) fluid solution for very stable operation. The issues are:
- 80% round trip efficiency (put in 10kWh, get 8kWh out) compared to lithium which is 90-94% depending on manufacturer.
- Cost per kWh - not much volume in the market keeps prices relatively high
https://redflow.com/products/redflow-zcell/
However I know that these ZnBr units are being used by telcos in NZ as part of the power setup for things like 4G towers - even in the Alps! Some of the mobile phone infrastructure has solar as the primary source with one of these ZCells in a shed next to it (they also have a diesel gen in there but usage is < 2% of the time I think).
I have considered off grid, but I think we would still need to go lead acid if we did that and then I would need a generator, so went off the idea.
The issue with off-grid is the entry cost - you need to account for about 4 days without sun, and not your most frugal estimate either; average usage + 50% for emergencies IMHO. Probably starting at NZD$50K ish.
If you had a "lifestyle block" and needed to pay the power company $150K to string in some power, it becomes well worth it.
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@NTA said in Solar Power and Storage - a nerd's view:
The issue with off-grid is the entry cost - you need to account for about 4 days without sun, and not your most frugal estimate either; average usage + 50% for emergencies IMHO. Probably starting at NZD$50K ish.
That's why I went of the idea - not the cost - the days without sun. If we get a Nor easter we can end up in cloud. Elevated section that looks out sea so it can blow straight into our place and not having grid backup could be a problem (hence the generator comment).
Thanks for the info on batteries will look into those.
We do have a "life sentence" block but I have grid power. Three phase to my new barn which is about 300 hundred meters from the house site. I did meet some people the other day who are off grid and you have exactly described their situation, 150k to get the power in, or 50k for off grid batteries, generator, etc. They actually really like it though.
Solar Power and Storage - a nerd's view