Flat roof installation in Netherlands - considering glass-glass, bifacial, manufacturer, dimensions

[NeoX]

I am planning a flat rooftop installation of 14-16 panels with microinverters for my home. I have done research and considered sun elevation, azimuth angle, and run simulations in PVsyst. The best option for my roof is a 20° tilt.

I live in the Netherlands, and I am considering various quotes from different suppliers, and the cost range is surprisingly wide. Some are nearly double the cost of others for the same number of panels and microinverters.

So, I am now at the point where I'm considering the following three main things:

Glass-glass panels
Are glass-glass panels worth the extra expense as I have read here for example that the benefits in practice may not match the theory due to manufacturing quality. One of my quotes is the Trina Solar Vertex S+ dual glass monofacial module (TSM-NEG9R.28), and this manufacturer is considered Tier-1 on many sources such as here.

Bifacial panels
Are bifacial panels worth the extra expense as I see mixed opinions from the community here? However, I've also read here that they are useful if installed on a flat roof. Mine is flat, but will the benefit outweigh the cost with a 20° tilt? I could in theory increase the tilt to 25°, but then I will lose some efficiency due to mutual shading. Note that my rooftop is made from bitumen and is dark grey in colour, so I would be counting on some reflection and ambient light. I know that it's an extremely difficult metric to consider given the variety of factors for the energy generation of the backside of a bifacial panel, which is why manufacturers tend to only include energy generation data for the frontside of bifacial panels.

Manufacturer
I've had quotes from various suppliers in the Netherlands, and the most popular panel they offer seems to be Jinko JKM425-54HL4R-B which is glass-foil monofacial. Jinko is Tier-1, and from what I've seen, not a bad brand/model to choose. But I've also seen these other brands offered by Dutch suppliers: JA Solar, Trina Solar, AEG, Hyundai, Phono Solar, DMEGC, and (lesser known Dutch brand) Denim.

Dimensions
I've seen some panels available that are much wider than the standard size that the Dutch suppliers seem to want to sell, such as the LONGi 545 Wp and the JA Solar 560 Wp. However, the availability of these wider bifacial glass-glass panels seems sparse, and their product guarantee tends to be 12 years. This is opposed to the more standard size which I can find more readily available such as the Denim 430 Wp and the Hero 430 Wp (lesser known brands) whose product guarantees are 30+ years. What attracts me about the wider panels is that I can have less panels and therefore less microinverters to buy.

What I would like to understand from repliers on this forum are opinions on the above based on my location (Netherlands) and a flat roof installation. My minimum criteria are:

• 14-16 panels depending on panel width.
• 20° tilt or more (more will increase mutual shading as I'm already utilising the full roof space).
• 25-35 years product and power guarantees. This seems to be becoming the norm, and seems to be standard for glass-glass panels anyway.

Appreciate any help anyone can give me.

 

[SeaGal]

Welcome!

My thoughts...

a) panels are panels - they either work or don't.
b) elevation, tilt, azimuth are overrated - Nerds will ponder over the precise degree of tilt, but one more or less panel will be more significant and, if it's sh1tty weather you're stuffed anyway!
c) look at panel efficiency - bigger panels will produce more Watts, but only due to their physical size.
d) what use is a 30 year guarantee with a company that may not be trading in 2053?
e) you mention microinverters... what is the maximum power per microinverter? No use having 550W panels if your microinverter can only generate 375W each panel = string inverter may be better / cheaper.

 

[NeoX]

Welcome!

My thoughts...

a) panels are panels - they either work or don't.
b) elevation, tilt, azimuth are overrated - Nerds will ponder over the precise degree of tilt, but one more or less panel will be more significant and, if it's sh1tty weather you're stuffed anyway!
c) look at panel efficiency - bigger panels will produce more Watts, but only due to their physical size.
d) what use is a 30 year guarantee with a company that may not be trading in 2053?
e) you mention microinverters... what is the maximum power per microinverter? No use having 550W panels if your microinverter can only generate 375W each panel = string inverter may be better / cheaper.

Thanks for your reply, and the warm welcome.

b) I agree that an extra panel will provide more power than getting the tilt exactly right, but my configuration is such that the number of rows I can get is the same regardless of tilt (20° ±10°) as the distance between them is maximised for my roof based on a SSW orientation.
c) The efficiency is something I'm checking on all the panels, but they're all in the region of 21-22%, so not much difference.
d) The product guarantee applies to the manufacturer. So, I can go to them directly if they still exist as opposed to the supplier. Also, many of the Dutch suppliers offer guarantee insurance such that if they no longer exist, the guarantee is taken over by the insurance company. This is certified.
e) I was considering Enphase IQ8MC microinverters for the Jinko 425 Wp panels, but I will check if I need a different one if I go for the larger panels. I would prefer microinverters as I want to be able to monitor them individually, and for the efficiency of all the panels not to be brought down by one being inefficient. I also want to have the option to extend the system or replace individual panels later if necessary.

Any thoughts on glass-glass and bifacial?

 

[Hedges]

If you will want battery backup, tentatively design and price it before committing to anything.
Some inverters are best paired with same brand battery inverter, some work well with other brands.
Some hybrid inverters can work without batteries but you can add them later. Battery costs vary, typically 48V has cheap options available, high voltage does not.

I'm planning to use an SMA hybrid "Sunny Boy Smart Energy" when it is available in the US next January.
In Europe, they have similar single and 3-phase hybrid already on the market.

Hybrid-Wechselrichter | SMA Solar

Hybrid-Wechselrichter vereinen Solar-Wechselrichter und Batterie-Wechselrichter in einem Gerät.

www.sma.de

 

[OffGridForGood]

Welcome to the Forum,
I recall another member posting from NL with a flat roof, they determined the best design was to install the panels in double panel rows angled about 20-degrees East and West. ( Apparently snow is not a concern).
I can't seem to find that thread: but from memory, his pictures showed the panels set in pairs angled east and west, the ridge between the panels ran due north-south. He left a bit of space between the double rows for access.

 

[houseofancients]

I have a flat roof, use 21 degrees, located near breda.
Have 2 rows of 16 545 w jinko's on that roof, another 16 on my garage , again 21 degrees.

<Dutch mode>
Pas op met de btw vrije aanschaf, dit verplicht je om je als kleine ondernemer te registreren, en btw en omzet belasting te betalen bij meer dan 10kw op het dak.
Verder heb ik gekozen voor een string inverter + battarijen.
Op die manier heb je minder transport kosten, en ook minder terug levering die belast kan worden.
Uiteraard ook minder tot geen gebruik van het net wat ook weer belast kan en zal worden
</End dutch mode>

 

[NeoX]

Thanks for the replies once again, and the warm welcome.

Yes, I am definitely going to buy a battery to go with my installation, as @Hedges and @houseofancients mentioned you opted for. I'm quite set on microinverters for the reasons mentioned in my previous post, but Enphase IQ8MC seems to be the microinverter of choice in the Netherlands, and Enphase also do a compatible battery. I spoke to a supplier yesterday about this, and he suggested two batteries if I have a bigger system. Not sure how valid that is, though - will need to do more research.

Welcome to the Forum,
I recall another member posting from NL with a flat roof, they determined the best design was to install the panels in double panel rows angled about 20-degrees East and West. ( Apparently snow is not a concern).
I can't seem to find that thread: but from memory, his pictures showed the panels set in pairs angled east and west, the ridge between the panels ran due north-south. He left a bit of space between the double rows for access.

If I use a zigzag arrangement, then because of the orientation of my house, half of my panels would be facing northwest or northeast, which isn't ideal. And arranged them obliquely on my roof would be an inefficient use of the space. So, I think rows with them all facing the same direction is better. I've run some simulations on PVsyst, and this seems to indicate the same.

I have a flat roof, use 21 degrees, located near breda.
Have 2 rows of 16 545 w jinko's on that roof, another 16 on my garage , again 21 degrees.

<Dutch mode>
Pas op met de btw vrije aanschaf, dit verplicht je om je als kleine ondernemer te registreren, en btw en omzet belasting te betalen bij meer dan 10kw op het dak.
Verder heb ik gekozen voor een string inverter + battarijen.
Op die manier heb je minder transport kosten, en ook minder terug levering die belast kan worden.
Uiteraard ook minder tot geen gebruik van het net wat ook weer belast kan en zal worden
</End dutch mode>

Noted regarding the VAT. But this is all arranged by the supplier now. I think it's all changed. This no longer needs to be done by the customer AFAIK.

But good points regarding the battery and saving tax on the return delivery. It seems being as off-grid as possible is the way forward!

 

[Hedges]

Enphase ecosystem should work fine. Single vendor solution is the best way to go.
Just know the price and performance, since they are likely your only option.

I think their "battery" is a quantity of microinverters. Not sure if each has a dedicated battery of if they share.

Enphase will harvest power from each PV panel independent of how others perform. Depending on wattage sizing, it may miss some peak power from its panel.

Optimizers in a string of panels supposedly offers the same, but have some issues. They do offer per-panel monitoring.

Simple bypass diode works in theory for shaded panels, and in practice at least some of the time, but requires string inverter MPPT smart enough to move past local maxima to find a higher wattage one at lower voltage.

I think Enphase has a pretty good track record. Some of the optimizers, not so good. Microinverters are popular with installers in the US because any roof configuration can be fit, no worry about sufficient or matched string lengths.

 

[NeoX]

Enphase ecosystem should work fine. Single vendor solution is the best way to go.
Just know the price and performance, since they are likely your only option.

I think their "battery" is a quantity of microinverters. Not sure if each has a dedicated battery of if they share.

Enphase will harvest power from each PV panel independent of how others perform. Depending on wattage sizing, it may miss some peak power from its panel.

Optimizers in a string of panels supposedly offers the same, but have some issues. They do offer per-panel monitoring.

Simple bypass diode works in theory for shaded panels, and in practice at least some of the time, but requires string inverter MPPT smart enough to move past local maxima to find a higher wattage one at lower voltage.

I think Enphase has a pretty good track record. Some of the optimizers, not so good. Microinverters are popular with installers in the US because any roof configuration can be fit, no worry about sufficient or matched string lengths.

From what I can see here, it looks like it's just one battery for multiple microinverters. However, a supplier told me that batteries are a waste of money at present because of net metering in the Netherlands. For at least the next two years, residents get full credit for returned power to the grid, no taxation. Yes, I guess there is some loss, but I'm not sure that would outweigh the depreciation of the battery value and life in the same period. It was suggested to only get a battery once the Netherlands starts to reduce the net metering return which would not be for at least two years apparently.

 

[zanydroid]

Why not get monitoring only MLPE? Much cheaper per panel than any microinverter.

There are also reports right now of IQ8 only playing nice within the same ecosystem. I’m not a huge fan of vendor lock-in nor buying something that out of the box has caused interop problems. I use Hoymiles microinverters which are cheaper (especially in 4 port configuration, I use the 4 port 2 MPPT one a lot) and higher power than Enphase because I have extreme shading issues such that I shouldn’t even install solar panels (they barely break even on DIY with such cheap equipment). This also gives per port monitoring. They also allow me to use the relaxed wiring rules you can do in the US for AC string as compared to DC strings

I guess with EU electricity prices the Enphase premium might not be a big deal

Batteries, especially from ones with even higher markup, are highly questionable investment when net metering is available. Here in California batteries are mostly for resilience (kind of a luxury nice to have) and for folks that don’t have net metering.

 

[Hedges]

Perhaps that model is one battery (many cells in series) with one inverter in the box, making an "AC battery".

I thought the Enphase battery, maybe a different model, was one box with a bunch of Enphase microinverters each connected to a relatively low voltage battery. That AC couples to your Enphase PV inverters.

Most other brands of powerwall are a high voltage series string of cells, maybe 400V worth, and a single inverter. LG RESU-U was something like 48V or so of cells, with DC/DC boost converter to 400V.

Your supplier is correct regarding economics; if utility net metering acts like a 100% efficient battery, that is cheaper. Batteries cost you a premium for the convenience of backup during power failures. If you have time of use rates, time shifting with batteries might be beneficial.


Even if only 50% or 33% efficient (give back to you 1 kWh for every 2kWh or 3kWh you give them), that could be cheaper than batteries, depending on what your cost per kWh is amortized over life of PV system, and amortized over life of battery system.

The rock bottom DIY costs I come up with are $0.025/kWh for GT PV, and $0.05/kWh for battery, over their useful life. It depends heavily on assumptions of cell cycle life. For turn-key install ratio of costs may vary. Most batteries are much more expensive than the cheap cells or server-rack batteries I was looking at.

Enphase GT PV is competitive. I think Enphase batteries cost more than a number of alternatives.

Is SMA an available brand in your market?
That can be installed as PV only initially, battery added later.
I think the 3-phase model provides backup today, while the single-phase is supposed to when an external transfer switch product comes available.

Hybrid Inverters | SMA Solar

Hybrid inverters combine solar inverters and battery inverters in one device.

www.sma.de

 

[zanydroid]

I thought the Enphase battery, maybe a different model, was one box with a bunch of Enphase microinverters each connected to a relatively low voltage battery. That AC couples to your Enphase PV inverters.

Yes they parallel in a number of “IQBAT” microinverters within the Encharge battery. I am not sure what the voltage is. It’s not super important from a user facing angle though what the architecture is. I guess other than the fact that surge is probably unavoidably terrible

EDIT: IOW I don’t see a clear technical advantage that buying into Enphase ecosystem would provide for storage. It will derisk the interop issues with their micros, and they use PLC for micros which is probably more robust when dialed in, but I don’t really grok a reason why their storage per se would have a leg up. And the interop issues are only relevant for extended grid down situation

 

[Hedges]

Surge as Zany mentioned is important for whatever motor loads you have.
The SMA Hybrids I suggested don't have much surge, looks like the 3-phase one has 20% to 50% depending on model. The single phase similarly modest.

If you've got something like a heat pump or well pump, you need to determine the surge requirements.
If it exceeds what these high-frequency inverters can do, there are some expensive low-frequency inverters, and some high frequency inverters, with better surge capability.

Just know what you want and what it costs before painting yourself into a corner.

 

[zanydroid]

I didn’t see backup power as a requirement in OP, I mentioned surge mostly because i was free styling on my vibes about Enphase approach

the LONGi 545 Wp and the JA Solar 560 Wp.

FWIW HMS-2000 microinverters are designed for these “monster” (or I guess Utility scale) solar panels. 2000W across 4 panels and generously wide input voltage and current range

 

[houseofancients]

From what I can see here, it looks like it's just one battery for multiple microinverters. However, a supplier told me that batteries are a waste of money at present because of net metering in the Netherlands. For at least the next two years, residents get full credit for returned power to the grid, no taxation. Yes, I guess there is some loss, but I'm not sure that would outweigh the depreciation of the battery value and life in the same period. It was suggested to only get a battery once the Netherlands starts to reduce the net metering return which would not be for at least two years apparently.

I beg to differ with your supplier..
Reason, next to net metering being build off, powerco's are about to play their own game in charging for kw's delivered to the grid ( Vandebron is already doing that).

Expect all powerco's to do the same..

Next I would find a different supplier..
This one seems to care what is easy for him and not what might be good for you

 

[zanydroid]

IMO if the future proofing (ie battery compatible design) is done upfront I’m not sure what the downside is to defer the battery purchase. Those prices generally go down/more equipment available at a competitive price. The battery market is not mature in the US (esp with equipment regulations — UL9540 — still difficult to comply with) so without a compelling reason to buy now (IE no net metering available or not living in a high power shutoff / power outage location) it’s better to sit and wait.

Now if you can explain in more detail how EU market is different that would definitely be helpful.

 

[CJM]

I am planning a flat rooftop installation of 14-16 panels with microinverters for my home. I have done research and considered sun elevation, azimuth angle, and run simulations in PVsyst. The best option for my roof is a 20° tilt.

I live in the Netherlands, and I am considering various quotes from different suppliers, and the cost range is surprisingly wide. Some are nearly double the cost of others for the same number of panels and microinverters.

So, I am now at the point where I'm considering the following three main things:

Glass-glass panels
Are glass-glass panels worth the extra expense as I have read here for example that the benefits in practice may not match the theory due to manufacturing quality. One of my quotes is the Trina Solar Vertex S+ dual glass monofacial module (TSM-NEG9R.28), and this manufacturer is considered Tier-1 on many sources such as here.

Bifacial panels
Are bifacial panels worth the extra expense as I see mixed opinions from the community here? However, I've also read here that they are useful if installed on a flat roof. Mine is flat, but will the benefit outweigh the cost with a 20° tilt? I could in theory increase the tilt to 25°, but then I will lose some efficiency due to mutual shading. Note that my rooftop is made from bitumen and is dark grey in colour, so I would be counting on some reflection and ambient light. I know that it's an extremely difficult metric to consider given the variety of factors for the energy generation of the backside of a bifacial panel, which is why manufacturers tend to only include energy generation data for the frontside of bifacial panels.

Manufacturer
I've had quotes from various suppliers in the Netherlands, and the most popular panel they offer seems to be Jinko JKM425-54HL4R-B which is glass-foil monofacial. Jinko is Tier-1, and from what I've seen, not a bad brand/model to choose. But I've also seen these other brands offered by Dutch suppliers: JA Solar, Trina Solar, AEG, Hyundai, Phono Solar, DMEGC, and (lesser known Dutch brand) Denim.

Dimensions
I've seen some panels available that are much wider than the standard size that the Dutch suppliers seem to want to sell, such as the LONGi 545 Wp and the JA Solar 560 Wp. However, the availability of these wider bifacial glass-glass panels seems sparse, and their product guarantee tends to be 12 years. This is opposed to the more standard size which I can find more readily available such as the Denim 430 Wp and the Hero 430 Wp (lesser known brands) whose product guarantees are 30+ years. What attracts me about the wider panels is that I can have less panels and therefore less microinverters to buy.

What I would like to understand from repliers on this forum are opinions on the above based on my location (Netherlands) and a flat roof installation. My minimum criteria are:

• 14-16 panels depending on panel width.
• 20° tilt or more (more will increase mutual shading as I'm already utilising the full roof space).
• 25-35 years product and power guarantees. This seems to be becoming the norm, and seems to be standard for glass-glass panels anyway.

Appreciate any help anyone can give me.

Offgridcentrum? Complete diy manual Included. I’ve installed wirh JA panels, pylontech battery, goodwe inverter (warmteservice). But then you are alone. Nobody is your friend

 

[CJM]

IMO if the future proofing (ie battery compatible design) is done upfront I’m not sure what the downside is to defer the battery purchase. Those prices generally go down/more equipment available at a competitive price. The battery market is not mature in the US (esp with equipment regulations — UL9540 — still difficult to comply with) so without a compelling reason to buy now (IE no net metering available or not living in a high power shutoff / power outage location) it’s better to sit and wait.

Now if you can explain in more detail how EU market is different that would definitely be helpful.

EU market is the same as US. There is ‘chinese’ and there is Victron. One is the hard way.

 

[zanydroid]

EU market is the same as US. There is ‘chinese’ and there is Victron. One is the hard way.

That sounds incomplete and reductive. What about SMA, Fronius, etc?

There’s multiple tiers of Chinese vendors. Several tiers within code compliant tier even

 

[NeoX]

Why not get monitoring only MLPE? Much cheaper per panel than any microinverter.

There are also reports right now of IQ8 only playing nice within the same ecosystem. I’m not a huge fan of vendor lock-in nor buying something that out of the box has caused interop problems. I use Hoymiles microinverters which are cheaper (especially in 4 port configuration, I use the 4 port 2 MPPT one a lot) and higher power than Enphase because I have extreme shading issues such that I shouldn’t even install solar panels (they barely break even on DIY with such cheap equipment). This also gives per port monitoring. They also allow me to use the relaxed wiring rules you can do in the US for AC string as compared to DC strings

I guess with EU electricity prices the Enphase premium might not be a big deal

Batteries, especially from ones with even higher markup, are highly questionable investment when net metering is available. Here in California batteries are mostly for resilience (kind of a luxury nice to have) and for folks that don’t have net metering.

I've recently been getting sold SolarEdge string inverters a lot more by some suppliers which enticed me to have another look at them based on the MPPT and MLPE concepts which mitigate shading and allow per-panel monitoring.

---

Perhaps that model is one battery (many cells in series) with one inverter in the box, making an "AC battery".

I thought the Enphase battery, maybe a different model, was one box with a bunch of Enphase microinverters each connected to a relatively low voltage battery. That AC couples to your Enphase PV inverters.

Most other brands of powerwall are a high voltage series string of cells, maybe 400V worth, and a single inverter. LG RESU-U was something like 48V or so of cells, with DC/DC boost converter to 400V.

Your supplier is correct regarding economics; if utility net metering acts like a 100% efficient battery, that is cheaper. Batteries cost you a premium for the convenience of backup during power failures. If you have time of use rates, time shifting with batteries might be beneficial.


Even if only 50% or 33% efficient (give back to you 1 kWh for every 2kWh or 3kWh you give them), that could be cheaper than batteries, depending on what your cost per kWh is amortized over life of PV system, and amortized over life of battery system.

The rock bottom DIY costs I come up with are $0.025/kWh for GT PV, and $0.05/kWh for battery, over their useful life. It depends heavily on assumptions of cell cycle life. For turn-key install ratio of costs may vary. Most batteries are much more expensive than the cheap cells or server-rack batteries I was looking at.

Enphase GT PV is competitive. I think Enphase batteries cost more than a number of alternatives.

Is SMA an available brand in your market?
That can be installed as PV only initially, battery added later.
I think the 3-phase model provides backup today, while the single-phase is supposed to when an external transfer switch product comes available.

Hybrid Inverters | SMA Solar

Hybrid inverters combine solar inverters and battery inverters in one device.

www.sma.de

I've updated the link to this in my earlier message as the original one was dead. The diagram at the link relates to microinverters, but seems to a "combiner" to allow all the power from the microinverters to be channelled into one or more batteries. I think the reference to "IQ8 series microinverters" just means they're from the IQ8 series, not that anything is in series as opposed to parallel.

SMA doesn't seem to be a sold brand in the Netherlands (never seen it offered), but the SolarEdge Home Hub is offered, and this is a hybrid inverter. In fact, one supplier I'm speaking to spoke to SolarEdge on my behalf today, and this is what they recommend to futureproof my system.

---

I beg to differ with your supplier..
Reason, next to net metering being build off, powerco's are about to play their own game in charging for kw's delivered to the grid ( Vandebron is already doing that).

Expect all powerco's to do the same..

Next I would find a different supplier..
This one seems to care what is easy for him and not what might be good for you

Tbf, a few suppliers are saying similar - I'm working with 18 suppliers at the moment (a lot, I know, but I'm trying to get a good overall picture). The supplier in question would make more money by selling me a battery, but he assured me he'd rather sell me an economical system right now than one that maximises his revenue. Similarly, I find many suppliers in the Netherlands are resistant when I ask for more panels to squeeze on every bit of space on the roof. They'd rather sell me less panels to minimise shading from the roof edging and the chimney. I guess they're not as hard-selling as in other countries (the Dutch are known for spending as little money as possible, but that also seems to be the case with companies selling to customers in a lot of cases ? - it seems to be an ingrained cultural thing, which means it's annoying for me when I'm trying to spend more money!).

Noted on the energy companies. I'm aware of Vandebron doing it, but I'll see how it goes. I'd rather just get a battery the moment it becomes economical for reasons such as this, but note what @Hedges said here:

Even if only 50% or 33% efficient (give back to you 1 kWh for every 2kWh or 3kWh you give them), that could be cheaper than batteries, depending on what your cost per kWh is amortized over life of PV system, and amortized over life of battery system.

---

IMO if the future proofing (ie battery compatible design) is done upfront I’m not sure what the downside is to defer the battery purchase. Those prices generally go down/more equipment available at a competitive price. The battery market is not mature in the US (esp with equipment regulations — UL9540 — still difficult to comply with) so without a compelling reason to buy now (IE no net metering available or not living in a high power shutoff / power outage location) it’s better to sit and wait.

Now if you can explain in more detail how EU market is different that would definitely be helpful.

Not different. Completely agree. Doesn't seem to be a downside in deferring if I get a futureproof system such as the SolarEdge Home Hub mentioned above. There is certainly no issue with power cuts in the Netherlands (the infrastructure is second-to-none), but being independent of the grid given the constantly changing government policies around energy and taxation might be a useful peace of mind to have. My house is powered by the battery, and nothing goes through the smart meter unless the battery is depleted.