Hi from France

[Crossy5]

Hi everyone.

Quick into about me and what I want to achieve.

We bought a large building which we converted into a house in rural France. All our water heating and cooking is electric and there are separate AC units in each room. Our power supply is three phase with a maximum supply of 24kW. I want to reduce our bills and have a little bit of autonomy if the grid should ever go down. I don't want to be totally off grid or be able to run the house entirely off batteries as power here is still reasonably priced so having grid is still a sensible option at the moment.

We should be able to install a 3 phase 9kW ground based system with one axis manual tracking in a field with no shading. I was thinking 3x8 strings of 375watt panels, just because it makes the rack a manageable size.

I've tried and I've tried but I can't seem to find much clear information on what I'd need to be buying. Every time I think "right, got it" the units seem to change or I read that another inverter has the ability to run a heat pump when I never realised running heat pumps was an issue! I am completely confused and just floundering in a sea of acronyms, ever changing units and connectivity issues.


Any kind soul fancy helping me out with some advice please.

Thanks a lot.

 

[Hedges]

Some commercial installation may still benefit from tracking, but I think it is better to have multiple strings of PV panels, of different orientations, paralleled onto MPPT inputs. Separate MPPT is OK, but you can over-panel more sharing MPPT.

Make sure your inverter can deliver the surge current needed for motor loads.

SMA makes Sunny Island + Sunny Boy for a powerful 3-phase system. They also have a smaller all-in-one (with less starting surge.)

I think Victron is another good brand that can do 3-phase. Also Outback.

Inverters can run heat pumps, etc. What matters most is starting surge (locked rotor amps). In Europe, you probably have "Power Factor Corrected" units available. In the U.S. our cheaper units do not have PFC, and the harmonics the produce may upset some inverters.

"Power Audit" - figure out how many kWh/day you need, how long you want to get by during cloudy weather running off batteries before starting a generator, how many peak kW you will consume for minutes/hours, and how many surge kW for a couple seconds.

 

[Crossy5]

Some commercial installation may still benefit from tracking, but I think it is better to have multiple strings of PV panels, of different orientations, paralleled onto MPPT inputs. Separate MPPT is OK, but you can over-panel more sharing MPPT.

Make sure your inverter can deliver the surge current needed for motor loads.

SMA makes Sunny Island + Sunny Boy for a powerful 3-phase system. They also have a smaller all-in-one (with less starting surge.)

I think Victron is another good brand that can do 3-phase. Also Outback.

Inverters can run heat pumps, etc. What matters most is starting surge (locked rotor amps). In Europe, you probably have "Power Factor Corrected" units available. In the U.S. our cheaper units do not have PFC, and the harmonics the produce may upset some inverters.

"Power Audit" - figure out how many kWh/day you need, how long you want to get by during cloudy weather running off batteries before starting a generator, how many peak kW you will consume for minutes/hours, and how many surge kW for a couple seconds.

Thanks a lot for taking the time to reply to my dumb newbee questions. I really do appreciate your reply. Unfortunately I've reached the point where I'm going to give up on the whole idea. I just can't get my head around any of it despiye spending weeks reading up on it and watching numerous videos. I think this might be partly due to all the language barriers.

PV and electrical terminologies. Usually explained (very kindly might I add) by Americans. Then trying to translate it to something I can understand then trying to figure out how it would apply to the French electrical system and bureaucracy.

Is there anyone out there that would like to design a 9kw grid tied system for me.

 

[Hedges]

Start with Dollars (or Euros, or Francs) and determine if photovoltaics make financial sense.

If you have "Net Metering" available (electric utility gives you credits for power fed back into the grid), then what you need is something like an SMA Sunny Boy grid-tie inverter. It doesn't have to be 3-phase, could just drive two wires of your utility connection.

The hardware (PV panels, inverter, electrical and mounting hardware) for a 5kW system should cost around US $5000. Assuming equivalent 6 hours full sun per day around the year, it will produce 30 kWh/day and over 20 years the cost works out to $0.025/kWh. (PV panels should last 25 to 40 years, and inverter is reasonably likely to last 20 years. If it needs replacement, power cost $0.03/kWh over 20 years and keeps working after that.)

Many of us DIY our systems, labor is free. If you pay someone else to install it, price is likely 3x or 4x as much. Each vendor will offer a package of equipment they sell. For some reason, in Australia, consumers are able to buy an installed grid-tie system (all labor included) for just $1/watt, not the $3 or $4/watt we pay in the U.S.

Here is Sunny Boy. Even what they show as "Basic System" is more complicated than necessary; no internet monitoring required (unless local laws require it). Just PV panels, inverter, connected to breaker panel.

https://files.sma.de/downloads/SB30-60-DS-en-52.pdf

Two such inverters for 9kW peak. But I would orient 4.5kW of PV panels South East, 4.5kW South West, and wire those to a single 6kW inverter. More hours of good output, lower peak wattage.


Up to 10kW 3-phase

https://files.sma.de/downloads/STP8-10-3AV-40-DS-en-32.pdf

Those are all grid-tie for net metering.
Battery systems cost much more, are only worth while if grid is unavailable, or unreliable and you are willing to pay a premium for backup when grid is down.

 

[Risky Rob]

Why not install a very small system as a learning experience? I started with one panel, a PWM controller, and an auto battery.

 

[Crossy5]

Start with Dollars (or Euros, or Francs) and determine if photovoltaics make financial sense.

If you have "Net Metering" available (electric utility gives you credits for power fed back into the grid), then what you need is something like an SMA Sunny Boy grid-tie inverter. It doesn't have to be 3-phase, could just drive two wires of your utility connection.

The hardware (PV panels, inverter, electrical and mounting hardware) for a 5kW system should cost around US $5000. Assuming equivalent 6 hours full sun per day around the year, it will produce 30 kWh/day and over 20 years the cost works out to $0.025/kWh. (PV panels should last 25 to 40 years, and inverter is reasonably likely to last 20 years. If it needs replacement, power cost $0.03/kWh over 20 years and keeps working after that.)

Many of us DIY our systems, labor is free. If you pay someone else to install it, price is likely 3x or 4x as much. Each vendor will offer a package of equipment they sell. For some reason, in Australia, consumers are able to buy an installed grid-tie system (all labor included) for just $1/watt, not the $3 or $4/watt we pay in the U.S.

Here is Sunny Boy. Even what they show as "Basic System" is more complicated than necessary; no internet monitoring required (unless local laws require it). Just PV panels, inverter, connected to breaker panel.

https://files.sma.de/downloads/SB30-60-DS-en-52.pdf

Two such inverters for 9kW peak. But I would orient 4.5kW of PV panels South East, 4.5kW South West, and wire those to a single 6kW inverter. More hours of good output, lower peak wattage.


Up to 10kW 3-phase

https://files.sma.de/downloads/STP8-10-3AV-40-DS-en-32.pdf

Those are all grid-tie for net metering.
Battery systems cost much more, are only worth while if grid is unavailable, or unreliable and you are willing to pay a premium for backup when grid is down.

Thanks for the reply.

Here feed in is really not a thing. I've spoken to a few people that have pv installs and the consensus seems to be the paperwork is an absolute nightmare then the feed in tariff is so small it's just not worth the trouble. The French bureaucracy is globally notorious for a reason ;-)

The thing that started me thinking about getting some PV's was a site online here that sells 3kw kits starting from ~2150€ for string inverter to 2355£ for micro inverters.

Kit solaire 3000W 230V autoconsommation - APS

Garantie produits DS3L- APSystems 10 ans ! Garantie panneaux solaires, 10ans sur le matériel, 25ans performance Kit APS entièrement PLUG AND PLAY

allo.solar

Kit solaire 3000W - 230V - autoconsommation - SOFAR

Panneaux solaire 375 Mono Onduleur réseau SOFAR 3000TL Garantie produits 10ans

allo.solar

And you know how things progress . So now I've gone from a quick easy 3kW inverter to run a heat pump and swimming pool to full on 9kW preppers paradise with bunker and back to nothing.

I get what you're saying about angling the arrays to reduce total output but over longer duration, bigger area under the curve and all that.

I have thought getting a micro inverter system as it should be far easier to install (I might be wrong).

The regulations here allow you to put 3kw system in with just a declaration to the local authorities, nothing more. I'm hoping this is 3kw/phase. If it is I think I've found my answer just finding out any information here is not as easy as you might think.

 

[Hedges]

Microinverter is probably easier. Efficiency is a bit lower and cost a bit higher. Lifespan no longer than quality string inverters. Biggest attraction of microinverter these days is no need for separate "Rapid Shut Down" hardware, a fireman safety requirement in the U.S. (drops voltage < 80V between any wires), also no need for arc-fault protection.

With string inverters, you can over-panel, including with multiple string orientations.
Panels get larger faster than inverters are updated, and most microinverters are undersized compared to larger (most cost effective) panels, so can't put two panels on one microinverter, even if of multiple orientations.

Low feed-in tariff is the nail in the coffin. Sometimes it is 10% of retail. In California we're looking at a future plan with 25% feed-in tariff, but also a "photon tax" every month on installed PV size that consumes 100% of the credit, so net zero credit.

What you may want is "zero export". A current transformer around grid feed is monitored so PV inverter only supplies up to 100% of household loads, nothing ever exported. We have "split phase" 120/240V in the US. If you have 230/400Y, hopefully the meter only tallies total on three phases, doesn't notice if you export on one while importing on the other.

If it makes financial sense to install a GT PV system and use-it-or-lose-it for kWh during the day, do that. Many of us are at work during weekdays, might charge an EV at night, so little opportunity to do so. Pool pump maybe. In that case I would suggest "guerilla grid-tie", put a standard GT PV inverter behind the pool pump switch so it only exports when pump consumes power, never net export.

I don't think Sunny Boys connect directly to a current transformer; for the US that takes extra hardware. If you want to do zero-export or the whole house, not just pool pump, look for a quality brand that supports zero-export natively.

Oh, 3kW no paper work? In that case you export surplus but get little or no credit, that is easier than zero-export. Go for it.
Probably 3kW total. Consider the Sunny TriPower, with multiple PV orientations. But better yet look for limited export. As you cover higher percentage of daytime loads, purchase of grid power is reduced but utilization of PV vs. curtailment increases, reducing savings.

Quality battery backed systems are expensive. If you want backup, look into cheaper offgrid solutions, which can have grid pass-through (work like a UPS.) Cheapest batteries, "server rack" or DIY lithium, may cost $0.05/kWh with daily cycling over 16 or 8 year cycle life. Add cost of inverter and PV. But for backup, you don't need the 1000's of cycles of lithium. I used AGM, "KISS".

 

[Crossy5]

Why not install a very small system as a learning experience? I started with one panel, a PWM controller, and an auto battery.

I've installed a small system on our camper, that was easy. It's more the risk/worry of wiring everything up, flicking the switch and watching a 3k€ inverter melt, or the wires set fire to the field .

 

[Risky Rob]

I've installed a small system on our camper, that was easy. It's more the risk/worry of wiring everything up, flicking the switch and watching a 3k€ inverter melt, or the wires set fire to the field .

I saw in an earlier comment that you can build an off-grid 3000W system with less hassle. I am on the grid, but in an emergency can run basic appliances in my house using 800W of panels and 4000 W of battery storage.

 

[Crossy5]

Low feed-in tariff is the nail in the coffin. Sometimes it is 10% of retail. In California we're looking at a future plan with 25% feed-in tariff, but also a "photon tax" every month on installed PV size that consumes 100% of the credit, so net zero credit.

Wow, that's rough. Similar to here as I believe, very little reward for lots of outlay to get the paperwork in place.

What you may want is "zero export". A current transformer around grid feed is monitored so PV inverter only supplies up to 100% of household loads, nothing ever exported. We have "split phase" 120/240V in the US. If you have 230/400Y, hopefully the meter only tallies total on three phases, doesn't notice if you export on one while importing on the other.

We have the new digital meter so I think they'll probably monitor both ways.

If it makes financial sense to install a GT PV system and use-it-or-lose-it for kWh during the day, do that. Many of us are at work during weekdays, might charge an EV at night, so little opportunity to do so. Pool pump maybe. In that case I would suggest "guerilla grid-tie", put a standard GT PV inverter behind the pool pump switch so it only exports when pump consumes power, never net export.

This was the original idea, we can use a lot of energy heating water during the day in the summer which will save us a bundle. In the winter we could run AC getting the house warm then top it off from the grid in the evening.

I don't think Sunny Boys connect directly to a current transformer; for the US that takes extra hardware. If you want to do zero-export or the whole house, not just pool pump, look for a quality brand that supports zero-export natively.

Oh, 3kW no paper work? In that case you export surplus but get little or no credit, that is easier than zero-export. Go for it.
Probably 3kW total. Consider the Sunny TriPower, with multiple PV orientations. But better yet look for limited export. As you cover higher percentage of daytime loads, purchase of grid power is reduced but utilization of PV vs. curtailment increases, reducing savings.

So, I'd have to find a system that's happy to throttle back output to suit usage then?

 

[Hedges]

I've installed a small system on our camper, that was easy. It's more the risk/worry of wiring everything up, flicking the switch and watching a 3k€ inverter melt, or the wires set fire to the field .

Check voltage between wires before each PV connection (do NOT touch meter leads with your fingers!), check polarity before connecting to inverter. Tighten wires properly. Use IR thermometer to check for temperature rise when carrying full current. Add a beefy surge arrestor to the grid side.

Grid tied PV is pretty simple. Touch-safe fuse holders and MC4 connectors make it easy to plug together hot PV wires, even if 600Voc. AC side, make sure things are off, confirmed with a meter. You do NOT want to cause a short especially with 3-phase; our safety training at work warns about "Arc flash".

With "notify only", you may be able to use old stock old specification equipment. Here in the U.S., new features obsolete old models, so I've bought SMA brand GT PV inverters new in the box for $0.10/W. Also look into used PV panels, taken down from commercial installations.

 

[Crossy5]

Now for the other stupid question.

Why can a grid tied PV system only produce power when connected to the grid? I know there's the SMA Tripower that can run a critical panel but that's not the same thing, is it?

I am assuming it's for safety. Would it not be possible to disconnect from the grid and connect a generator to fool the inverter into believing mains power was present?

 

[Crossy5]

400 volts gets very warm on the hands

 

[Hedges]

We have the new digital meter so I think they'll probably monitor both ways.

Not if all you have to do is notify them you've connected an inverter. That is, the meter will distinguish net backfeed from net consumption, but if you produce 8kW and consume 5kW, all they will see is 3kW net export. (Some systems have PV and loads metered separately.)

Now for the other stupid question.

Why can a grid tied PV system only produce power when connected to the grid? I know there's the SMA Tripower that can run a critical panel but that's not the same thing, is it?

I am assuming it's for safety. Would it not be possible to disconnect from the grid and connect a generator to fool the inverter into believing mains power was present?

If you succeed in fooling the inverter, you may get backfeed into the generator. Only if loads exceed PV, or if the generator runs a bit fast no-load and the inverter responds ("frequency-watts") by reducing output. There are battery inverters supporting AC coupling for this purpose, good for big systems but not economical small.

Here is SMA's 3-phase hybrid inverter. Might do all you want, but supported batteries may be more expensive than you like. Various other "Chinesium" brands may check other (but not all) boxes of [Good] [Pretty] [Cheap]. Some are even "batteries optional".

https://files.sma.de/downloads/STPxx-3SE-40-DS-en-11.pdf

 

[Crossy5]

Not if all you have to do is notify them you've connected an inverter. That is, the meter will distinguish net backfeed from net consumption, but if you produce 8kW and consume 5kW, all they will see is 3kW net export. (Some systems have PV and loads metered separately.)



If you succeed in fooling the inverter, you may get backfeed into the generator. Only if loads exceed PV, or if the generator runs a bit fast no-load and the inverter responds ("frequency-watts") by reducing output. There are battery inverters supporting AC coupling for this purpose, good for big systems but not economical small.

Here is SMA's 3-phase hybrid inverter. Might do all you want, but supported batteries may be more expensive than you like. Various other "Chinesium" brands may check other (but not all) boxes of [Good] [Pretty] [Cheap]. Some are even "batteries optional".

https://files.sma.de/downloads/STPxx-3SE-40-DS-en-11.pdf

Yeh, that was the SMA inverter I was looking at, then the site I linked to sells LG batteries for ~5.5-6k€ depending on voltage. This is where mission drift becomes a problem though. I might be open to spaffing double the amount on a system but most definately not unless I can be 100% certain it's not going to go up in smoke. Which brings me back to the original problem, this system is too complicated or requires a knowledge base way beyond my understanding.

Just some quick calculations brings the cost of just the main components, panels, inverter and battery up to over 13,000€. It was only supposed to be a cheap money saving project . This is how we get into trouble.

That company I linked to does a 3kw kit using Npower IQ7's for just under 2800€

 

[Hedges]

I got another zero on you ?

And I have enough background to at least understand how not to smoke the equipment or myself.
When I started, this was supposed to make financial sense, at least if my predictions of inflation came true.
Now I'm building 3-phase in addition to my 4-inverter split-phase. Just because.

 

[Carpo]

Thanks a lot for taking the time to reply to my dumb newbee questions. I really do appreciate your reply. Unfortunately I've reached the point where I'm going to give up on the whole idea. I just can't get my head around any of it despiye spending weeks reading up on it and watching numerous videos. I think this might be partly due to all the language barriers.

PV and electrical terminologies. Usually explained (very kindly might I add) by Americans. Then trying to translate it to something I can understand then trying to figure out how it would apply to the French electrical system and bureaucracy.

Is there anyone out there that would like to design a 9kw grid tied system for me.

Are you still with us? just caught your thread now. I'm also in France (Normandy) and just ordered a 3kW (no battery) kit from chocdiscount.fr Phone Laurent, he is very good and English fluent.