Domestic solar PV quotes 2018

air

KCross wrote: »

You dont suffer from cynicism do you @air!!

I wish I had cause for a different point of view!
I applaud the existence of SEAI but like very many other government departments and quangos it exists first and foremost to serve its staff at great cost to the nation (and the environment in this case).

Northumberland

Winterman1234 wrote: »

Yes after grant, bunaglow with tiled roof and all panels on the same side. Location Donegal and company are northern ireland based and on SEAI register.

I wonder if you went forward with that NI based company? From my reading of the SEAI register there was only one company from NI included, and I used that company, with a very bad experience, still waiting for remedial work to be completed in order to get the SEAI grant. PM me for more details.

This contrived problem of not being able to use the power we produce being arguably and controversially solved by storing a lesser percentage of it in a high tech battery with complex electronics rather than offsetting gas and coal-fired utility power plant load...

Can we not solve the issue by optimising our array according to load demand instead of pointing everything due South?
It'd be simpler, cheaper, a better investment (faster return) and more efficient I think.

unkel

Sir Liamalot wrote: »

Can we not solve the issue by optimising our array according to load demand instead of pointing everything due South?
It'd be simpler, cheaper, a better investment (faster return) and more efficient I think.

I'd say most people can't. People just work with the roof they have. For a lot of people that means south facing, like for myself. Putting in an expensive ground mounted east west facing system using up the very little I have left of my back garden is not an option. If I ever will put in a garden room / large shed, it will be east west facing and plastered with PV for the very reason you mention

I don't mind sending electricity back to the grid for free. My system is only in since earlier this year and I have sent at least 2,000kWh to the grid. I don't mind either to build a large battery pack with re-used second hand batteries to store some of it and use it myself in the evening - and I would have gone for the subsidised battery system this year if I hadn't had PV already. I don't mind charging my car with PV. That's my next project after the battery.

Northumberland

Hello, I wonder if anyone on this forum has had any experience/success with running a solar/battery system completely off grid - at least for a short time?

I have about 4.7kW of panels, hooked up to a Solis RHI-3.6K-48ES hybrid inverter and 2 Pylontech US2000 Plus Li batteries. They system is all working rather well, so long as it is 'grid linked'. But I live in an area where the ESB main power cables run through a forestry plantation, and, in spite of appeals to ESB, every time there is a winter storm I am without power for several hours. It seems a real pity to be 'lighting candles' when I have 5kW of power stored in batteries and a hybrid inverter that according to it's specs can work 'off grid'.

My installer, who unfortunately has much bigger projects to chase than following up on his commitment to me, did eventually install a change over switch and a connector to the "off grid" outlet on the Solis, but they system will still not power the house (any of it) when the main grid switch is turned off. The Solis manual is a classic example of presumably clear Chinese being translated in to semi-meaningless english, there are several different places where settings for 'off grid use' are mentioned, but far from clear what exactly should be done. I have been on to the Solis expert in the UK who tried to be helpful, but so far, I have not succeeded.

reklamos

Northumberland wrote: »

Hello, I wonder if anyone on this forum has had any experience/success with running a solar/battery system completely off grid - at least for a short time?

I have about 4.7kW of panels, hooked up to a Solis RHI-3.6K-48ES hybrid inverter and 2 Pylontech US2000 Plus Li batteries. They system is all working rather well, so long as it is 'grid linked'. But I live in an area where the ESB main power cables run through a forestry plantation, and, in spite of appeals to ESB, every time there is a winter storm I am without power for several hours. It seems a real pity to be 'lighting candles' when I have 5kW of power stored in batteries and a hybrid inverter that according to it's specs can work 'off grid'.

My installer, who unfortunately has much bigger projects to chase than following up on his commitment to me, did eventually install a change over switch and a connector to the "off grid" outlet on the Solis, but they system will still not power the house (any of it) when the main grid switch is turned off. The Solis manual is a classic example of presumably clear Chinese being translated in to semi-meaningless english, there are several different places where settings for 'off grid use' are mentioned, but far from clear what exactly should be done. I have been on to the Solis expert in the UK who tried to be helpful, but so far, I have not succeeded.

The inverter that you have is not capable of running completely off grid. I have same one just 5kWh. I asked the same question my installer and this is the answrr I got from him. He said there good amount of inverters that do support that capability but none of them were SEAI approved, hence no grant would be available.

Northumberland

The sales material and the instruction manual, such as it is, for my Solis Hybrid says that it DOES support 'off grid', and the technical person working for Solis in the UK (an english guy who did really seem to know the inverter inside out) who I got through to on the phone said that it could be easily switched to 'off grid' mode - just that he never got round yet to telling me exactly how to do it. I do understand that SEAI and or ESB do not really want off grid use for some reason or other, but that should not prevent a user having the option I feel. There is another potential problem with the 'firefighter shunts' that SEAI require to be installed in the roof space under the panels which will isolate the DC power as soon as the AC power is turned off at the meter box, by, for example, the fire brigade when tackling a fire. But that is not my problem at the moment, since my installer 'forgot' to install such a shunt!

Northumberland

From the manual available online -
Page 3 - "Product description - The Solis RHI series is designed for residential hybrid systems, which can work with batteries to optimize self-consumption. The unit can operate in both off-grid and on-grid modes[/COLOR]. [/B]The Solis RHI series has 4 different models: RHI-3.6K-48ES, ... RHI-5K-48ES etc". The unit itself, as shown in Fig 1.2 Bottom side view on the same page of the manual (page 3) has two output sockets, one labelled AC-GRID, which is where the 'normal' connection back to the grid is made, and the second socket is labelled 'AC-BACKUP' and this is presumably to supply AC from the batteries when their is no grid. Page 41, under 'storage mode select' states that there are three items in the Storage Mode Select: Time charging, Off-grid and Auto ON/OFF modes. "In installations where no grid is present it is recommeded to use Off-Grid mode."

unkel

reklamos wrote: »

The inverter that you have is not capable of running completely off grid.

Of course it is. It has a separate emergency AC circuit that you can power your house with when the grid is down, provided of course there's enough juice in your battery and subject to the max discharge rate of your battery. In the case of 2 * Pylontech US2000, that should be 2 * 25A or 2.5kW

Plenty to power the base of your house with plus about one heavy appliance at a time like a washing machine or microwave. You can't use kettle / shower / oven / EV charger and the like though

My own AC side inverter (Sofar ME3000) is the same. I'm connecting the emergency AC output to a waterproof outside socket. If the grid should go down, I'll connect up a 25m extension reel into my house and connect the essentials onto it

People are getting shockingly bad information from what are supposed to be reputable (because SEAI approved) installers

Northumberland

Thanks Unkel for confirming that. The only thing now then is to find out exactly how the settings should be configured to run off grid! As I said before, user manual rather opaque.

reklamos

unkel wrote: »

Of course it is. It has a separate emergency AC circuit that you can power your house with when the grid is down, provided of course there's enough juice in your battery and subject to the max discharge rate of your battery. In the case of 2 * Pylontech US2000, that should be 2 * 25A or 2.5kW

Plenty to power the base of your house with plus about one heavy appliance at a time like a washing machine or microwave. You can't use kettle / shower / oven / EV charger and the like though

My own AC side inverter (Sofar ME3000) is the same. I'm connecting the emergency AC output to a waterproof outside socket. If the grid should go down, I'll connect up a 25m extension reel into my house and connect the essentials onto it

People are getting shockingly bad information from what are supposed to be reputable (because SEAI approved) installers

Ok, but for this you need to wire your all house onto backup output and have automatic switch when the power is cut. In other inverters all that stuff is done internally by the inverter.

Northumberland

reklamos wrote: »

Ok, but for this you need to wire your all house onto backup output and have automatic switch when the power is cut. In other inverters all that stuff is done internally by the inverter.

I dont think so. As Unkel has already suggested.

I already have a manual switch already installed to switch to the 'backup' output from the inverter to connect with my whole house in the event of a grid supply failure. So long as we are careful not to use the electric kettle etc etc, this should be fine to keep the lights and TV going on a dark winters night during a power cut, and we would just have to remember to turn the switch back to 'grid' when the mains came back.

reklamos

Northumberland wrote: »

I dont think so. As Unkel has already suggested.

I already have a manual switch already installed to switch to the 'backup' output from the inverter to connect with my whole house in the event of a grid supply failure. So long as we are careful not to use the electric kettle etc etc, this should be fine to keep the lights and TV going on a dark winters night during a power cut, and we would just have to remember to turn the switch back to 'grid' when the mains came back.

This is what I meant you need to do it manually. I have nothing connected to backup. Have tried how it work when you flick the switch to backup when you have grid power?

garo

AFAIK most inverters allow you to operate in either mode but not both. So you either have wires connected to the EPS output or AC-GRID output. Does your switch physically move the connection over from AC-GRID to AC-BACKUP in your case?
This separate connection is essential as you need to have is something that isolates your inverter and the backup circuits it powers from the grid. You don’t want to accidentally electrocute an ESB worker repairing lines that they thought were without power. Hence unkel’s device of having a physically separate outlet. You cannot have your entire house connected to the backup without isolating it from the grid. Maybe the switch you talk of does that already by you need to be sure.

Have you rooted around in your inverter confit settings? There must be something to switch modes.

garo

Sir Liamalot wrote: »

This contrived problem of not being able to use the power we produce being arguably and controversially solved by storing a lesser percentage of it in a high tech battery with complex electronics rather than offsetting gas and coal-fired utility power plant load...

Can we not solve the issue by optimising our array according to load demand instead of pointing everything due South?
It'd be simpler, cheaper, a better investment (faster return) and more efficient I think.

I agree and the solution is net metering which makes it uneconomical to store anything in a battery. It does have a negative impact on the long-term grid health though as net demand drops midday while the evening peak remains the same. So peak generation capacity has to remain the same and since thermal generators have a cost for every stop and start they are keep running during the day even when not needed. See California having problems with so much solar the midday wholesale power prices are zero in the summer.
Ireland is nowhere near that so the only things stopping us is the powers that be not doing anything to give us net metering or a FIT.

unkel

garo wrote: »

I agree and the solution is net metering which makes it uneconomical to store anything in a battery. It does have a negative impact on the long-term grid health though as net demand drops midday while the evening peak remains the same. So peak generation capacity has to remain the same and since thermal generators have a cost for every stop and start they are keep running during the day even when not needed. See California having problems with so much solar the midday wholesale power prices are zero in the summer.
Ireland is nowhere near that so the only things stopping us is the powers that be not doing anything to give us net metering or a FIT.

We'll have V2G and hundreds of thousands EVs before there is substantial PV generation in Ireland

garo

We live in hope. But Ireland is already far behind the rest of Western Europe in terms of grid digitalisation and smart metering. V2H has a few years to go. Net metering can be implemented now.

Peak power at midday is a side effect of FIT. Aim the panels 15° or East-west, it doesn't look as productive on paper but it's king of import offset and that's where the best payback is.

V2G has all the same problems of battery. Your battery gets smaller with usage and you have to invest more energy at higher cost than you can extract at reduced sell-back rates. The kWh extracted from your car costs far more to put there than from a cable.

garo

I disagree on the first point. I have an E/W system and I get peak power from 12-3 right now. It’s just physics! There is no orientation that can get you more at 5pm than at 1pm. Even a pure West orientation won’t do that.
I have a relatively small battery - to keep costs down - but I find it is quite useful for covering sudden increases in demand during the day or if a cloud covers the sun while the oven is on.
Of course I still think that for Ireland right now the best step is to get net metering. Look at the daily demand graphs here: http://smartgriddashboard.eirgrid.com/
Solar PV helps with the morning and day load and batteries help with the evening peak.

More power is not the same as more usable power.
The idea is to synchronise our generators to our loads. Not to produce as much as possible while we are at work.

rolion

unkel wrote: »

We'll have V2G and hundreds of thousands EVs before there is substantial PV generation in Ireland

Forget V2G... V2H is the new king !


Published on Jan 17, 2019
Can you go off-grid in the middle of Brisbane and power your home just from solar, a Tesla Powerwall and... the Outlander PHEV?

I have visited Ralph who has disconnected his house from the energy grid beginning of December 2018 and lives completely from solar power and a Tesla Powerwall 2. If the sun does not shine and the Powerwall is depleted, he uses the PHEV as a back generator to power his house from the traction battery.
We also did a test and fully charged my car from his car battery. It worked!
Great guy, great day, great technology!

V2G or V2H, what is better?

garo

Sir Liamalot wrote: »

More power is not the same as more usable power.
The idea is to synchronise our generators to our loads. Not to produce as much as possible while we are at work.

And my point is that it is impossible to do that with solar PV. An E/W orientation like mine helps but you still need a way to store or export the excess midday energy. In Ireland solar PV is small enough that net metering would encourage more installs. In Australia on the other hand where 25% of homes have solar, the midday dip requires more creative solutions.1

garo

Here’s an example of how even a small battery comes in handy. With a 4.8kWp system the cloud cover has brought current output down under 1kW. I have the washing machine on so as it draws 2.2kW the battery kicks in reducing I’m port from the grid.

Which is more expensive the kWh extracted from the battery or the kWh imported from utility?

garo

Utility hands down during the day. I showed my math on this site recently. 1500€ for a 3.5kWh battery with 10k cycles and 80% DoD gives you 5.3c in and out. Daytime tariff is 15-18c.

murphaph

air wrote: »

The government is directed by civil servants and various commercial interest groups and as such it should be no surprise that all policy is shaped to benefit one party or the other (or themselves obviously!)

The SEAI stands to maintain or increase it's workforce by continuing with needlessly bureaucracratic grant schemes. This benefits the head of SEAI as he or she is now more secure and head of a bigger organisation, more wage and pension potential.

A FIT will potentially reduce profits for energy suppliers and so they will lobby against it.

I'm not in the least surprised that no FIT was announced.

I seem to recall an EU court case which mandated us to introduce one recently though?

Not a court case but a directive. It was published around the end of 2018 but member states have 18 months to implement it in national legislation.

That's if it's the same directive I have in mind. In Germany we have FIT but we also have a penalty for installations > 10kWp whereby you must pay a proportion of your own self consumed (!) energy to the network operators for network upkeep. This has been outlawed in the EU with this new directive and PV operators here can't wait for this penalty payment to be killed off. It's really unpopular and has created a psychological 10kWp barrier in people's heads. In fact it still makes sense to "cover your roof" if you can get over about 13kWp on it but if you can't it's typically better to stop just short of the 10 to avoid being subject to this self consumption penalty.

I think the same directive mandates FIT in the first place if it doesn't already exist.

Edit: here's a link. It's in German but sections of the actual directive are in English if you scroll down.

https://www.energie-experten.org/experte/meldung-anzeigen/news/eu-verbietet-eeg-umlage-auf-photovoltaik-eigenverbrauch-4738.html

10k cycles, Wow! That really is a lot by standards.
What kind of battery is it? Is it 100% efficient?
Have they cycled any for 20, 000 hours? 2.5years continuous charge & discharge testing @ C1. When was the battery designed?
What chemistry is it?

Each cycle will return less and cost more input as it ages. Effectively getting more expensive per kWh with time.
Has the outlay cost of supporting hardware and installation been factored?

What about the cost of the solar array attached that actually made the power? Has that been deducted from the figure as the battery is a collector not an energy generator? Did you derate the PV payback to accommodate the efficiency reduction stored energy will have, having lost some via the hybrid charger and back out the inverter in a quadruple conversion? Solar DC -> Inverter AC -> Battery Charger DC -> Inverter AC?

garo

Oh come on. This is suspiciously close to trolling. Do all of that and you are still nowhere near 15c. Plus the battery + hybrid inverter outlay is subsidised by the SEAI grant. I bet that €1000 covers all your derating and PV inefficiency and all that.

Hybrid inverters shouldn’t be doing a quadruple conversion. That’s what an AC coupled battery system would do. Regardless any losses there are irrelevant as you would have been exporting that excess to the grid for free anyway. So I don’t see why I need to derate the panel payback.

LiFePO4. Manufactured May 2019. 10k cycles is the optimistic scenario and I use 6k for pessimistic scenario. Battery has a warranty for those many cycles.

Trolling for someone to actually measure their system performance objectively or do a scientific calculation. All this advice on what's best and zero data.
Batteries aren't green is the long and short of it they are facilitators for green technology and the Irish implementation is reducing national domestic green tech.

The SEAI grant doesn't make the energy cheaper it means someone else has paid for it.
In all my days I have not seen a battery compete with utility on cost and I measure systems instead of supposing..
I also build them and I can't make it make sense with free equipment and labour.

If you use the power your panels are producing as they are producing this is the best payback you will get.
If overproduction is a problem then load priority and generator runtime optimisation are the most direct steps to investment return.
After this we have system sizing. Can solar run evenly all day instead of peaking some of the day and in accordance with load demand.
So much less expense because so much less hardware.

What does a battery do? Economically or scientifically? Help separate your electrons (minus losses) from our electrons?

If arrays were designed to send all their power to the grid it would get used by the grid. This is greener than keeping 80% for nighttime. Coal, peat, gas and garbage are filling the 20% hole.

garo

There’s a lot in your post so let me try and address a few points.

1) I am talking about the economic benefit to me and not society as a whole when I compare battery vs. Utility cost of power. We are at a point where the marginal cost of battery storage is less for the end consumer than utility supplies power. For the end user any power exported to the grid in Ireland is wasted so charging a battery with that power is free.

2) The answer is different when you are looking to optimise the grid. Though it is absolutely not possible to get level power or even a power curve approaching the national usage profile. Simply cannot be done. So you need to supplement with other sources or think of storage. Battery storage has a high environmental cost. My preference would be something like pumped hydro. But it’s hard to find appropriate sites for it.

3) Battery costs have come down drastically in the last 5 years so prior assumptions may not hold.

4) I have an engineering degree and design systems too so no need to talk down to me. Happy to have a discussion based on science.

Battery costs have not come down they have shot up for lightweight high energy density. I'm not sure why lightweight chemistry is competing in static traction. I guess marketing helps a lot and being new is higher regarded than ruling the roost 150 years.
Aren't telecoms and UPS still using lead acid?
I can get 10's of kWh lead acid for less than kWhs of li-ion.

I am mistaken about hybrid topology, as you say I was describing an AC coupled system.

Optimising generation; If you mount panels flat or fanned with a bias on east & west to compensate for less irradiance at exposed periods we get a nice flat generation curve all day long instead of pointing them all south and getting large amounts of power for short periods when nobody is home to use it.
If you have diversion loads in place this uses abundance when available offsetting import.



Most installations won't have an isolation transformer. This is a safety device to eliminate the risk of malfunctioning electrocution prevention circuit breakers.
I have not seen an SEAI Approved Installer fit one.
The alternative is to fit a €400 more capable electrocution prevention circuit breaker instead that is tolerant of injected high-frequency switching DC.
I have not seen an SEAI Approved Installer fit one of these either.

The cost of energy extracted from a battery is: A realistic projection of it's energy delivery over it's expected lifetime including deratings for temperature and ageing divided by the cost of the battery including it's supporting hardware and installation + system losses and battery inefficiency + replacement system hardware costs incurred during operation.

Can you quantify the cost of your battery storage round trip after system losses?
Does this make extracting power from it more or less expensive than importing as a standard grid-tied system operates?

You have counted the energy twice, you are saying that solar power which hasn't paid for itself yet is reducing the cost of the battery. The battery only pays for itself after solar. Can it do it within 10 years? Is 10 years a realistic projection? Is there any data to support this?
6k cycles from LiFePO4 is not conservative 2k > 3k seems to be the results from labs...You can play with this like a lot of manufacturers do; say used at 30% rated capacity depletion instead of industry recognised 20%. Limit discharge and charge 20% through the BMS but not derate the capacity because it's still there it just never gets used.

What is a warranty except a liability margin built into the price of the product?

garo

I will just focus on two points.

1) Why have I counted energy twice? I am generating 2kW right now and the consumption is only 300W. The remaining 1700W would go to the grid. Instead it goes into the battery for use in the evening. Where is the double counting?
2) I have a E/W system. Trust me when I say that you get way more solar between 12 and 3 than at any other time. E/W is better than S. But it still does not align with usage. Attached is the PV output for last Sunday. You can see that the E panels peak at around 12 and the W around 3:30pm. There is far more output between 12 and 4 than outside of those hours. With an E/W system. Tilted 30 to the horizontal. You seem to be claiming that somehow with the right orientation you can magically get a flat generation curve. Ain’t gonna happen. It’s basic physics. The shallower the angle of the sun the more the rays have to travel through the atmosphere and the more they attenuate. Show me a single example of a flat generation curve from solar anywhere in the world.

Your cost analysis for the battery is based on the power you put into to it being free and not having a debt to pay to the solar array.

I'm saying if you mount the array to give you an even distribution of power all day as much as is feasible then you stand a better chance of reducing overall import. Which is the highest rate the system can get for its production.

Storing it to use later means there is less available from the system.
I can't make any money by having a battery.
It's embodied energy neutral.
It seems like a stagnant investment.

I could give power away for free to my neighbours ( even though the ESB will charge them for it) for the same return.
If I allow it out my incomer it's better for the environment.

Batteries on utility fed installations are a nil sum game.

garo

I would be giving away the power for free if I didn’t have a battery. That power is free for all intents and purposes. I have already paid for the array and would have paid the same amount if I didn’t have a battery.

Most of us don’t have the freedom to orient our array to optimise production for our usage. So you are arguing for something we cannot do.

And still waiting for any evidence of that level power production you spoke of earlier. I don’t think you have much experience with how power output changes with orientation. Go do some googling and you will find free software to do that. And you will see how wrong your assumptions are.

Same with LFP batteries. Have a read of this paper https://www.sciencedirect.com/science/article/pii/S0306261918310225
Your assumptions are so off the mark.

garo

I don’t like having a battery. I would much rather get net metering. But in its absence a battery will save me money. Especially with the SEAI pilot grant that allows me to claim €2400 more than if I didn’t have a battery.

garo

I really don’t know how you can seriously claim that battery costs have not come down. See this figure from a Bloomberg annual price survey.

Northumberland

garo wrote: »

I really don’t know how you can seriously claim that battery costs have not come down. See this figure from a Bloomberg annual price survey.

Fair, u enjoyed reading your last 3 or 4 posts, they agree with my thinking and understanding. I have a 4.5 kW of panels here in Ireland and 2 Pylontech 2000 US batteries, installed in March this year, still waiting for SEAI grant because an SEAI inspector visited finally 3 weeks ago and required firefighter shunts to be fitted etc etc, my installer too busy fitting panels to Lidl stores in Cork to f8nish my job and help me get my gran5. Anyway, apart from that, my SERP up is working well and saving me money I am sure, I have a NIBE heat pump, so that is thirsty for power day and night. I am about to install at least 2 additional Li batteries, my observations are that would help me get close to the magical hour of 11pm (winte4 time) when Electric Ireland night rate kicks in. I have two objectives, 1) use as much solar power as I can when it is generated and store the rest. And 2) use as little grid power during peak daytime rates. Doubling my battery capacity to charge at night tariff for use during following day must make sense, even if that following day is sun-less.

I also have 4kW of panels on a house in England, fitted in time to benefit from the FIT before they stopped it. The FIT is now very low, I am not getting much back, and getting it is a major hassle, although I had a smart meter installed (before the panels), the compan6 that I sell my power to can not read the other companies smart meter, how smart is that? My perception is, although I do not have figures to hand to be sure, that my Irish system is better econ9mucally, bu5 that will of course depend on actual life of the batteries.

Cortina74

Hi there,

I’m new here, but I’ve been following this (and other) PV related threads with interest, very informative.
I think I’ve gone from knowing nothing to at least knowing that I know nothing about PV installs ;-P
Anyway, I think I’m convinced to go with a DIY install with no battery for the moment as follows:

- Flat roof with good southerly aspect.
- Max 8 panels (2.4kW) will fit on the roof.
- Possible hot water diverter (for psychological rather than logical reasons!). The Apollo Gem Compact unit seems about 100 quid or so cheaper than the Eddie unit.

However, as the house is empty during the working week I think I would like to face 3/4 panels due slightly west to try prolong production during the longer days.
So, I would imagine I would require a dual MPPT inverter (such as the Solis Dual 3.6kW). Would anyone know if this can take as little as 3/4 panels to a single input? The data sheet says the start up voltage is 120V. Would this be to each input? Would the inverter start/stop a lot during the day with clouds passing etc.?

Also, if anyone knows of an electrician willing to wire into the fuse board and generally check over in the Dublin South City area I’d appreciate a PM.

Thanks!

unkel

Cortina74 wrote: »

So, I would imagine I would require a dual MPPT inverter (such as the Solis Dual 3.6kW).

Yes you would. I have that very inverter. I have a string of 10 panels S and a string of 3 panels W

Cortina74 wrote: »

Would anyone know if this can take as little as 3/4 panels to a single input? The data sheet says the start up voltage is 120V. Would this be to each input?

Yes it can. The startup voltage of a minimum of 120V is for all strings combined. It does have a minimum of 100V per MPPT string, but mine is mostly well under that for my W string and still producing amps although ideally I would have had a 4th panel on that string. Spec sheets are usually a bit conservative. The inverter is rated 3.6kW but I have actually seen 3.7kW coming from it

Cortina74 wrote: »

Would the inverter start/stop a lot during the day with clouds passing etc.?

No, it just keeps working. It only switches off when it is dark. Until then the inverter always produces at least some electricity, even during a thunderstorm

garo

@ Northumberland How much are you getting the Pylontechs for? Be prepared for not getting your money back for 8-10 years. Also charging at night is marginal at best. You save maybe 1-2c at most. Given winter is approaching if I were you I would wait till March. Batteries could likely be another 10% cheaper by then. Lithium wholesale prices have come down a lot in the last couple of years.

Cortina74

Thanks for the quick reply unkel.
If it works for you then I guess I should definitely sleep easy with my proposed install as they would all be generally facing the same (southerly) direction with maybe a 20-25 degree difference.

air

If you split it 4 and 4 you could wire the two strings in parallel to a single string inverter, might make it a bit cheaper.

One of around 2kW capacity would be plenty.
Keep an eye on the maximum input current it can absorb as it could be a limitation.

If you could find a supplier of some higher voltage panels (eg Panasonics) it would make things easier as 4 in series would be near 200V.

However they may not be easy to locate here.

Cost of enerergy extracted from battery + cost of night rate electricity ≠ profit compared to day rate electricity.

We can measure this & all I have said.

listermint

Northumberland wrote: »

Fair, u enjoyed reading your last 3 or 4 posts, they agree with my thinking and understanding. I have a 4.5 kW of panels here in Ireland and 2 Pylontech 2000 US batteries, installed in March this year, still waiting for SEAI grant because an SEAI inspector visited finally 3 weeks ago and required firefighter shunts to be fitted etc etc, my installer too busy fitting panels to Lidl stores in Cork to f8nish my job and help me get my gran5. Anyway, apart from that, my SERP up is working well and saving me money I am sure, I have a NIBE heat pump, so that is thirsty for power day and night. I am about to install at least 2 additional Li batteries, my observations are that would help me get close to the magical hour of 11pm (winte4 time) when Electric Ireland night rate kicks in. I have two objectives, 1) use as much solar power as I can when it is generated and store the rest. And 2) use as little grid power during peak daytime rates. Doubling my battery capacity to charge at night tariff for use during following day must make sense, even if that following day is sun-less.

I also have 4kW of panels on a house in England, fitted in time to benefit from the FIT before they stopped it. The FIT is now very low, I am not getting much back, and getting it is a major hassle, although I had a smart meter installed (before the panels), the compan6 that I sell my power to can not read the other companies smart meter, how smart is that? My perception is, although I do not have figures to hand to be sure, that my Irish system is better econ9mucally, bu5 that will of course depend on actual life of the batteries.

What's a firefighter shunt

Cortina74

Hi air,

air wrote: »

If you split it 4 and 4 you could wire the two strings in parallel to a single string inverter, might make it a bit cheaper.

I understood that combining the strings would cause the system to operate at the performance of the lowest producing panel? so for example in the evening the SW orientated panels would operate at the performance of the now less efficient SE panels?

air wrote: »

If you could find a supplier of some higher voltage panels (eg Panasonics) it would make things easier as 4 in series would be near 200V.

Unfortunately budget will largely dictate panel choice, hence the assumption of 300Wp (x 8) and the DIY with no battery install.

air

Cortina74 wrote: »

Hi air,

I understood that combining the strings would cause the system to operate at the performance of the lowest producing panel? so for example in the evening the SW orientated panels would operate at the performance of the now less efficient SE panels?

No, that would apply only if you put all 8 in series.
With two groups of 4you will get the combined output of both halves.

Cortina74 wrote: »

Unfortunately budget will largely dictate panel choice, hence the assumption of 300Wp (x 8) and the DIY with no battery install.

That's fair enough.
You should be able to find a Solis inverter around 2kW that should do the job.
Just check the input current, you'll want it to be able to handle around 15A.
Might be easier find a dual MPPT one in practice.

Cortina74

air wrote: »

No, that would apply only if you put all 8 in series.
With two groups of 4you will get the combined output of both halves.

Thanks air.... something tells me I should have guessed that!!
How would the two strings be connected together? Is there a special connector required?

air

Cortina74 wrote: »

How would the two strings be connected together? Is there a special connector required?

If you're using a single string inverter he easiest thing would be to buy 2 pre made MC4 Y harnesses and use those.

You could also put an MC4 fuse (likely 15A check the panel data sheet) and an MC4 diode in series with each string for a best practice installation that would be plug and play and fully waterproof.

Cortina74

The panel I'm looking at has the following rated Amp output:

ELECTRICAL CHARACTERISTICS AT NOCT
Current at Nominal Power (Imp): 7.50A

So using panels in series would result in 7.50A into the inverter whereas using two strings in parallel would result in 15A into the inverter ???
The Solis inverter range seem to be 11A.

air

Cortina74 wrote: »

The panel I'm looking at has the following rated Amp output:

ELECTRICAL CHARACTERISTICS AT NOCT
Current at Nominal Power (Imp): 7.50A

So using panels in series would result in 7.50A into the inverter whereas using two strings in parallel would result in 15A into the inverter ???
The Solis inverter range seem to be 11A.

Yes, 15A max in theory. Given the fact that you will be orienting both strings only slightly differently their peaks will overlap somewhat.
Your peak output power would be clipped at 1760W ( assuming panels are 40V maximum power voltage)
Now the impact on your total annual energy harvest would be fairly minimal in practice and it means that you can use a fairly small / cheap inverter.
You wouldn't see any clipping at all worth talking about for 8 months of the year.