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capassadeeplanning

2 posts

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#310910 29-Nov-2023 20:49
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Solar seems pretty much a given for us. We have a bunch of roof space, a bunch of yard space, a clear Cantabrian sky, some darn sexy azimuths, and 3-phase from the grid just begging to be quarrelled with by the sun.

 

But what about batteries? What about early adoption of wind?

 

We've got a bunch of quotes from a bunch of reputable companies recommended by the good geeks on other threads here. I won't name them now but I'll follow up with our final opinions once we've made a decision.

 

The problem is they've each come at this from a wildly differing perspective, and their advice contradicts one another.

 

 

 

Going in we know this:

 

  • we're not concerned about power outages
  • we are currently home during the day, with a live-in elderly couple with their own living area and cooking facilities
  • we run air con all day to balance the temperature for our infant kids
  • our power usage is unsurprisingly high right now ($25 per day)
  • we use 2 of our 3 phases currently
  • wind average here is 5.79m/s
  • roof pitch 32deg, room for 23 panels facing NW, 11 facing NE
  • with Electric Kiwi, could shift to MoveMaster plan for best buyback and halved night rate, or Meridian (17c buyback)
  • all of these installers offer to divert juice to our hot water before sending it back to the grid
  • we don't have an EV and likely won't buy one for 3-6 years

 

 

 

Installer A:

 

They say: "There's no way you can get 38 panels there without some hanging over the edge or in a dumb place. There's no point having 15+kW of juice if your inverter totals 11 or less." 

 

We think: They may have forgotten we have more than one phase. They're able to install soonest which is tempting.

 

Installer B:

 

They say: "Our inverters each have an up to 3kW PV outlet which you can plug things into during the day in case of a power cut.

 

We think: They've suggested 4 panels on the SW face - this seems dumb except quite a bit of evening sun blazes from that direction and neighbours have panels on this face. They claim great quality inverters and panels but promoted this by repeatedly slagging the other products as "cheap, Chinese, fake 25 year warranty". It was a bit of a Sinophobic sales pitch.

 

Installer C:

 

They say: "We're confident in our panel layout and have never had to change things once we come on site. Batteries generally aren't worth it."

 

We think: Big diff between system capacity and inverter capacity. Only installer not to come for a site visit.

 

Installer D:

 

They say: "To get to this capacity we'd need to install as a ground array. We don't do systems without a battery as we recommend efficiency over a 24h cycle. We'd estimate 60kWh from wind in winter. Our wind turbines are silent."

 

We think: Ground array doesn't appeal. Wind does. Good capacity matching across the components. Bloody expensive.

 

 

 

Advice warmly appreciated because the contradictions are many.

 

  • Is it worth maxing out the system if it'll zero our power bills?
  • Is it a recommended thing to have inverter and battery capacity as >90% of system capacity?
  • Are batteries overkill unless worried about self-sufficiency?
  • Is wind still a foolish investment or is it worth taking seriously?
  • Are SW facing panels really a silly idea given evening sun?

 

 

Any insights/experiences appreciated.

 

Caff

 

 


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  #3166033 29-Nov-2023 21:22
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Are those battery figures kW (peak power rating) or kWh (total energy storage)? Either way, I probably wouldn't recommend a battery unless you're concerned about outages (you're not) or there was some other compelling reason or massive time-of-day cost difference. The lifetime cost of the battery doesn't usually justify the ~10c/kWh that you get charged for exporting at one time and importing at another.

 

Wind is not usually productive in residential settings. It's also the most visibly and audibly intrusive, and the most difficult to deal with if maintenance is necessary. IMHO avoid unless you were off-grid and needed the redundancy against a week of cloud - and even then, it's a toss-up between wind and just more PV.

 

 

 

Panels facing in different directions is reasonable. However, it's really important that all the panels on one MPPT input (maximum power-point tracking) are under the same conditions, as the performance for the whole MPPT input stage is equal to the worst performing panel. So at morning/midday, those four panels drag down a string or two on the north face, and in the evening the north face drags down your SW face.

 

Inverters in the capacity range you're looking at often have two MPPT inputs, maybe 3. So unless 1/4 to 1/6 of your panels are on that south face so you can devote a whole input to them, this is a bad idea. If you can put a substantial number of panels on that face, it might be reasonable. You get slightly less total kWh out of it, but you get a flatter curve rather than a really big midday peak, and more power in the evening when it's most valuable to you. 

 

 

 

Re inverter oversizing: what happens is when it's really bright full sun, you might 'clip'. The inverter tops out, but the panels could provide more. 

 

Under NZ conditions, unless you have a shortage of roof, I would argue for more panels and a smaller inverter. 95% of the time, more panels give you more power because you're not in perfect sunlight. The other 5% is when you have way more power than you can use anyway, and everyone else is injecting into the grid.

 

Facing groups of panels in slightly different directions also helps to avoid clipping because each group of panels peaks at a different time.


 
 
 

Trade NZ and US shares and funds with Sharesies (affiliate link).
2kadmin
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  #3166034 29-Nov-2023 21:22
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We have:-

 

20 315W Panels

 

5kW inverter

 

14.4kW Lead Carbon Batteries.

 

We use Electric Kiwi as we have two plug-in vehicles, charging the batteries from the grid during our free hour of power and during winter for a couple of hours from the grid when the cars are charging.

 

We heat using a gas fire, recently put in a wood fire, and heat pumps 1 x 14kW & 1 x 7 kW.

 

There are only two of us in rural Bay of Plenty, and that used to be enough to avoid all power bills before we got PHEVs.

 

My advice is, if your preferred method of heating is heat pumps, forget the batteries. On overcast days your heat pumps will drain your batteries in minutes, assuming they can even keep up in the first place. This is why now have a wood fire and use the ducted heat pumps on the fan only just to push the hot air around.

 

Also, You'll soon notice that co-current loads quickly add up, i.e. you have the washing machine, drier, and heat pumps all running, you'll exceed what the system will provide you. Batteries might even struggle to charge if you are using a lot of Solar, during the day.

 

I'd go with Option C.

 

Inverter capacity, it's only about three months a year where you can make use of 100% of the panels output, so possibly not worth going to 90% of the panels rating with the inverter.

 

Wind, the generators I looked at really would only top up the batteries. They would need a gale to get anything like their stated output, and came with a lot of caveats about clean airflow. So I didn't pursue wind.

 

SW Panels - Panels facing in different directions need to be wired with micro inverters, wired to different inputs on the inverter, or fitted with shade modules. Typically, a string of panels only performs as well as the lowest panel, so provided they are wired correctly, I would put them on. I don't think anyone has ever said. 'I have too many solar panels'

 

Power companies are the key here; for a while, we were with Trust Power and sold our excess solar to the in-laws for an amount agreed between us; it was called Solar Buddies or something like that. 
Contact might be another good option without batteries as they have 3 hours of free power between 9 pm and midnight.
You just need to find the right balance.

 

Hope this helps with your decision.


Talkiet
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  #3166042 29-Nov-2023 21:34
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I didn't have kids - makes anything else I do pale in comparison to the savings :-)

 

 

 

That said, I recently put 6.6kW of solar on the roof and moved to an EV for my daily, so I am basically a tree hugger now.

 

N.

 

 





Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.




tweake
1215 posts

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  #3166044 29-Nov-2023 21:38
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i would avoid wind turbines. i know of a couple, one removed theirs and the other is noisy and has maintenance issues.


Talkiet
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  #3166046 29-Nov-2023 21:40
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Also, I have a Huawei 6kW inverter, and while I know I have more panel than inverter, I was told this would be ok - HOWEVER the Huawei is unable to keep the grid voltage under control on sunny days so in bright sun the grid voltage goes to 251.2 and the inverter throttles back and I only get about 5.2kW from the panels.

 

If I am able to put a decent load on (dishwasher / car charger at 8 amps etc) then that brings the local grid voltage down enough to allow the inverter to get to and maintain 6Kw from the panels - but it's annoying to micromanage it.

 

I wouldn't go Huawei again, not because I don't trust the company, but because even the local good installers seem somewhat in the dark about how it works at a detailed enough level to troubleshoot issues like this.

 

Cheers - N

 

 





Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.


  #3166049 29-Nov-2023 21:47
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Grid voltage isn't something the inverter can control. It's a matter of the size of the transformer, the size of the cabling from the inverter to the transformer, the grid voltage (11kV ish), and how much power you and your neighbours are consuming/producing. 

 

If the voltage is outside 230V +- 6% at the point of supply - where the power lines cross your property boundary, you can make a complaint and they can potentially adjust the transformer tap or replace cabling or the transformer. You can also look at replacing the cabling from the inverter to the main switchboard if it's particularly long or thin. 

 

Reducing power when the voltage hits 230 +10% (253V) is I think part of the regulatory requirements for grid-tie inverters. 


Talkiet
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  #3166083 30-Nov-2023 00:55
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Interesting, my inverter is clearly reducing before that 253V limit - it's doing it from about 251V... As I say, if I put a big load on, That drags the reported voltage at the inverter down and it happily chugs along at 6kW. Given I can influence the behaviour just by turning something big on, it feels like a local (on property) issue rather than a network issue.

 

The cabling from the inverter to the switchboard is about 10 metres but it was specced at well above the calculated requirement - I think about 70% above but I can't remember the size of cable.

 

The voltage when the inverter turns off for the day was 236V.

 

I am apparently located near the end of the segment, and there are a good number of houses around me with large solar installs and I wonder if that has something to do with this high voltage during sunny conditions. (The voltage is related very clearly to sunny conditions - during cloudy days - even cloudy hours - it's below 248)

 

 

 

 

 





Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.




dzh

dzh
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  #3166211 30-Nov-2023 10:00
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Keep shopping around. I just got a quote for 10kw + 10kwh battery install for 30k (which I still think is overpriced by about 30-25%) from one of the Micromall's installers.


capassadeeplanning

2 posts

Wannabe Geek


  #3166309 30-Nov-2023 11:44
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Thanks for the universally phenomenal and insightful comments. Super huge helpful.

 

 

 

dzh:

 

Keep shopping around. I just got a quote for 10kw + 10kwh battery install for 30k (which I still think is overpriced by about 30-25%) from one of the Micromall's installers.

 

 

You're not wrong though dzh, I just priced the components for Option C (which does look like the clear winner now) and am seeing prices online of about $1100 per inverter and $15k for the panels. Adding another $3k for components that's $20k.

 

Even after freight, install of ~$15k seems very hefty.

 

Unfortunately they're the only installer not to have itemised their quote.

 

 

 

Although, thinking about it, $1100 does seem cheap for an inverter. Here's the one being recommended:

 

https://moorabbinbatteries.com.au/products/redback-technologies-si5000-inverter-5kw

 

price AUD975.26. Has plenty of good reviews but some shockers, which I guess goes with the turf.

 

 

 

Keen for opinions, but understand if y'all are tapped out:

 

  • is $15k a crazy install cost for 38 panels?
  • is the Redback SI5000 not worth it?
  • is it generally worth buying all this stuff online then just paying for an install?

 

 

Have a great day.

 

 


  #3166383 30-Nov-2023 12:44
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Talkiet:

Interesting, my inverter is clearly reducing before that 253V limit - it's doing it from about 251V... As I say, if I put a big load on, That drags the reported voltage at the inverter down and it happily chugs along at 6kW. Given I can influence the behaviour just by turning something big on, it feels like a local (on property) issue rather than a network issue.


The cabling from the inverter to the switchboard is about 10 metres but it was specced at well above the calculated requirement - I think about 70% above but I can't remember the size of cable.


The voltage when the inverter turns off for the day was 236V.


I am apparently located near the end of the segment, and there are a good number of houses around me with large solar installs and I wonder if that has something to do with this high voltage during sunny conditions. (The voltage is related very clearly to sunny conditions - during cloudy days - even cloudy hours - it's below 248)



 


 



Nope, that's textbook soft grid.

When current flows through a cable, you get voltage drop. When the current is flowing in the other direction, this appears as voltage rise. For example, if the cable between your mains and the point of supply has an impedance of 0.1 ohm (fairly low), for every 10A you draw the voltage drops 1V. Conversely, if you inject 10A into the grid, the voltage raises by 1V *just in your mains cable*.

There's then further voltage drop/rise in the cables along the street to the transformer, in the transformer itself, and even in the 11kV cables to the transformer, though you individually have less and less of an impact on these because you're only a small portion of the load. In most cases, the only active voltage regulation is an on-load tap changer in the transformer producing the 11kV.

If you're seeing significant voltage changes from applying/removing load, that's an indication that it's probably your mains cable having that impact, rather than the network as a whole being too high.

This is a good explanation of your inverter's behaviour: https://support.solarquotes.com.au/hc/en-us/articles/115001759153-My-Inverter-Keeps-Tripping-or-Reducing-Power-On-Over-voltage-What-can-I-do-

Note that Australia uses 230 +10% -6%. NZ legally uses 230 ±6%, and as such the setpoints are slightly different.

So your inverter is must start reducing power above 244V measured, reducing linearly to 20% of rated power at 255V measured.

It also is supposed to disconnect in one second at 260V, and when the 10-minute average exceeds a selectable voltage, defaulting to 248V in NZ. I'm not sure from the standard what the reconnection delay is supposed to be.

Many of these settings can be changed, but only with written authorisation from the lines company.

The standard does allow for inverters to feature a volt-var response mode, providing/sinking reactive current to attempt to raise/lower the voltage by interacting with the inductive reactance in longer mains cables. This mode is required to be disabled by default if present.

Not relevant to you, but there's also an allowance for 3 phase inverters to support a voltage balancing mode, where they produce uneven output currents to even out voltage imbalance. Again, must be disabled by default and requires lines company permission.

MikeAqua
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  #3166406 30-Nov-2023 13:55
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I don't have the specs to hand, however, we are in the final design stages for our rural property near Blenheim.

 

I've looked at: -

 

- Solar

 

- Wind

 

- Nano-pumped-hydro (we have two ponds, separate in altitude by about 2m)

 

I can't make the pumped hydro work on paper (my gut said that would be the case, but it was interesting).

 

Solar with batteries stacks up, as we will have a pool heating system, A2W, W2W or G2W heat pumps for hydronic heating and quite a lot of refrigeration (meat, wine cellar etc).  We have space with sheds etc for about 40kW capacity.  We'll start with 20kW. 

 

I've looked at wind turbines.  Nominally they pay for themselves but I'm on the fence as most of the wind is at the site is accompanied by sunshine.  The really dark days are still/misty.  I think I'll see how the solar goes and then consider wind when I have a couple of years site specific weather data during El Nino (I already have two years of La Nina).

 

Originally started out looking at off gird.  But the site already has 3-phase power so there is no capital cost to connect to the grid, and I'd like to run some three-phase workshop equipment.  





Mike


wellygary
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  #3166411 30-Nov-2023 14:01
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  • we're not concerned about power outages
  • we are currently home during the day, with a live-in elderly couple with their own living area and cooking facilities
  • we run air con all day to balance the temperature for our infant kids
  • our power usage is unsurprisingly high right now ($25 per day


    You've likely got enough day time load to warrant not having a battery in the system , 

    The only question you probably need to think about is what will your load be in 5 years, or 10 years,? 

    Infant Children don't stay that way and in 5 years time they will be at school during the day, your Solar system will still be chugging in 15-20 yrs

    You may need to look at a battery later down the track to make better of your now surplus generation rather than selling to the grid...

mrdrifter
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  #3166607 30-Nov-2023 22:41
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We have had our system up and running for 23 days now and just ticked over 1MWh of generation, export of 700KW. Obviously each area is different but we put 22x440W panels and 2x5KW Huawei inverters, total was just on 21K full installed etc... and they suggested if there was room additional panels worked out ~1K each installed, maybe would have saved a bit with another 14 though. I had quotes from 16-25k for variations, happy to share my spreadsheet if it helps.

No issues from our inverters at all, the app is a bit of a pain design wise and I wish I had admin access, but does what it needs to.

I would have gone slightly smaller inverters but wouldn't save any money and was sizing the system to export at near maximum when possible and still be running our base load, and aircon and/or car charger.

With someone typically home we are able to load shift the last few things to optimal times which has been good. Just moving to a day/night plan with lower daily charges while we can which should reduce our costs even more as until this we have definitely been in the standard/high user camp.

The system so far has been peaking out at 8.4KW on the best days usually because load at the time and export limits restrict things. We are limited right now to 5KW export as we are single phase which is clipping due to the following ...

We are still waiting for our 7.2KW car charger to be installed, so have been running the 8amp charger when needed to trickle charge. This is working ok. Longer term I'm pretty keen on the wallbox quasar 2 when it finally makes it here. That should pretty much remove our power bill.


(Don't forget panel ratings are peak lab conditions)

I asked about adding a set of 4-6 panels to our southwest side, but the cost vs payback wasn't viable for our exposure.

Talkiet
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  #3166609 30-Nov-2023 22:47
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If you are pinning your hopes on V2H to remove your power bill, think again... V2H only works with loads above 1kW... So many houses won't hit that overnight so the V2H doesn't come into play... It's a not very well known characteristic of V2H (or the Wallbox - not sure which)

 

Cheers - N





Please note all comments are from my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.


eonsim
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  #3166711 1-Dec-2023 08:28
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A few comments:

 

A few years ago when getting solar installed my self the estimate was a base cost +$500 for every extra kW of residential inverter capacity for a reasonable quality basic inverter. While decent Chinese panels where 500-600 each and the more premium brands like REC 20-30% more. Allow for some inflation and 20-30% of the cost being labour (for an install that size they're likely to have multiple electricians and some roofing people (4-6 all up) busy for 1-2 days) and you can potentially ball park a reasonable cost.

 

 

 

If your not worried about battery backup don't bother with a battery. 

 

I assume option B was a Harrisons branch, in which case you are talking premium gear Fronius Gen2 inverters (with the PV point backup) and likely European (Qcells panels). They are very good kit and will likely last with out defects but you pay extra for it.

 

With 2 inverters in most of these setups that will typically provide 4 MPPT to work with (occasionally six), effectively each MPPT allows a different orientation for the associated panels. So for a good design there should be enough MPPT or more than the number of orientations they've proposed for the panels (both direction and angle combined).

 

With regards to overpanelling (more panels than inverter) this is typically recommended as it's the cheapest way to increase the power available in winter/crappier weather and extending the solar day. Inverters have a minimal power level needed to function and adding extra panels allows you to reach or maintain that level quicker during the day meaning you generate more power for longer. Typically the recommendation for inverter manufacturers is 20-30% more panels than inverter capacity. Over paneling effectively means during summer your system will work slightly better than it's inverter capacity, but will limit it's self to the size of the inverters during the peak period. During winter and crappier weather though the system will work like it's panel size. For example if you have 13kW on a 10kW inverter, during summer it might be 5-10% extra power from the 30% more panels, autumn and spring may be 10-20% more power and then Winter will likely be the full 30% more power acting as though you had a full blown 13kW install. An inverter with the same amount of capacity has panels may only hit it's max output for 2-3 hours a day during summer and the rest of the time it's below that. With 30% more panels it may hit it's max power for 3-6hours during summer and continue to do so into spring and autumn.

 

Have you talked to Lightforce? Of the big players they're typically decently priced and tend towards good quality upper midrange gear (usually chinese) rather than the premium european stuff. 

 

 

 

Also as you have 3 phase you could potentially go with 3x Inverters to spread the load across all the phases (would need to rewire the power board to use all of them). Many lines providers have a limit on the amount of power that can be exported per phase so going 3 phase can maximize the amount of power you can export. Unless you have a power load you can evenly balance across all three phases I wouldn't recommend going with a 3 phase inverter as they typically don't support unbalance generation they need to push an equal amount of power down each phase regardless of your load (3 seperate inverters of mixed sizes can match your use better in that case).

 

 

 

I would suggest getting another quote or two maybe try some local sparkies that do solar, or asking one of the other installers how much it would cost to match one of the other quotes. I also highly recommend going with someone who has come out to look at the site...


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