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Solar PV Hints, Tips & Troubleshooting

DrPhilG

Well I've reached the point of driving everyone nuts on the PV quotes thread, and since I now have my system installed and running my endless questions no longer belong there.

So I figured I'd ask here, and also provide a home for others in the same boat, with general questions and advice on managing post-install.

My first question (of many) is how do people best manage their production in order to reduce grid export? Despite being overcast and miserable a fair bit of the day, I've produced 24kWh so far today, but ended up exporting 11.

Not too bad when we're home, as the wife did a few loads of washing and drying, put on the dishwasher etc.

But we're both at work tomorrow so other than a timed or remotely activated washer/dryer run we would end up exporting a lot more.

Extra battery capacity or a water diverter would help, but they don't tend to justify their costs in the long term.

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garo

unkel wrote: »

That's no problem as long as you install at least 40kWh of it :pac:

Pm me if you see a good UPS system going for cheap or free. :pac:

daughy

Just wondering has anyone had any input from companies in Ireland regarding vehicle to grid charging.
Potentially 30 to 60 kwh of battery sitting in your front garden if you have an electric vehicle.
I would only be interested in this if I can just power the home, not send back to the grid. Will do some research on it.

The losses would be staggering though, dc solar to ac, then ac to dc car charging, then dc car back to ac home.. My god

unkel

Most western countries have had trials of V2G / V2H at this stage. But not here afaik. It's pretty straight forward, you'd need a smart charge point and a car that can handle bi-directional charging / discharging

Losses and inefficiencies are not important. At times the value of electricity is zero (or negative) because we produce more renewables than we can consume or share with other countries at which point utility companies will pay you to please take the electricity off their hands. This already happens quite often, even in this country

[Deleted User]

I'm running a soft gridder-esque test at the moment and I'll post the results when they are in. Look folks everyone keeps refuting what I'm saying but nobody offers any data to back it up. There's too many associated losses with running batteries instead of utility to be viable. It's lemming central. As long as we have demand over supply for clean power the battery is a deadweight.

I've heard that one before; this and that are on trial. What are they testing? People arre willing to pay for it. Look the answer is in front of your faces measure the lifetime cost of the system in money and energy and then proclaim it's merits. All I'm hearing for all the evidence i offer is I disagree because someone with an invested interest says otherwise.

Asbestos was a great idea back in the day too.

antoinolachtnai

Sir Liamalot wrote: »

I'm running a soft gridder-esque test at the moment and I'll post the results when they are in. Look folks everyone keeps refuting what I'm saying but nobody offers any data to back it up. There's too many associated losses with running batteries instead of utility to be viable. It's lemming central. As long as we have demand over supply for clean power the battery is a deadweight.

I've heard that one before; this and that are on trial. What are they testing? People arre willing to pay for it. Look the answer is in front of your faces measure the lifetime cost of the system in money and energy and then proclaim it's merits. All I'm hearing for all the evidence i offer is I disagree because someone with an invested interest says otherwise.

Asbestos was a great idea back in the day too.

As long as demand is greater than supply then the battery is a deadweight, sure

How are you determining whether demand is greater than supply, on the grid as a whole as opposed to what is going on in one household?

How have you modeled for future growth in PV? With 200,000 6 kW sites in place, will demand continue to exceed supply?

Assuming a quarter of that 1.3GW is in a single 50km x 50km region how have you modeled for what happens at the grid level when is cloud bank blows in?

[Deleted User]

I am looking at the network not a household....because we're still burning coal and gas in the daytime to rotate steam turbines.
Future growth is every household ought to be rockin' solar.

Flow batteries are good more HVDC interconnectors would be promising.

^ Same cost as a battery.

The battery is a utility solution to a utility problem. Giving it to the end user serves the utility more than the user. Which is greener? 6kW PV and a battery or 12kW PV per houshold?

graememk

Sir Liamalot wrote: »

I am looking at the network not a household....because we're still burning coal and gas in the daytime to rotate steam turbines.
Future growth is every household ought to be rockin' solar.

Flow batteries are good more HVDC interconnectors would be promising.

^ Same cost as a battery.

The battery is a utility solution to a utility problem. Giving it to the end user serves the utility more than the user. Which is greener? 6kW PV and a battery or 12kW PV per houshold?

Out of interest.. how much could you oversize an array,

Ie 8.5kwp on a low slope roof with half facing NE (-130)and other half SW( +50), on a 6kw inverter?

[Deleted User]

It's a product of acceptable Voc and Imp. I put 200% on my last until I got a bigger one...then I got more PV...that's how it goes. I'm running 140% now.

I think a lottov people say 120%. The correct answer is in the manual.

antoinolachtnai

Sir Liamalot wrote: »

I am looking at the network not a household....because we're still burning coal and gas in the daytime to rotate steam turbines.

We are talking about the future network now with Gigawatts of PV.

A big proportion of turbine generation in the mix is required to provide inertia. You can’t reduce the turbine generation beyond a certain point. Household PV will never provide inertia.

Just because gas turbines are running does not in itself mean there is more demand than supply for PV electricity.

PV will never provide cover for intermittency.

Future growth is every household ought to be rockin' solar.

Flow batteries are good more HVDC interconnectors would be promising.

^ Same cost as a battery.

The battery is a utility solution to a utility problem. Giving it to the end user serves the utility more than the user. Which is greener? 6kW PV and a battery or 12kW PV per houshold?

What does it mean to say ‘greener’?

[Deleted User]

By greener I mean highest offset of hydrocarbon based fuel usage.
First of all there's triple the clean power on the network because double the solar and minus the associated battery losses and second hydrocarbons were not used to fabricate a battery to reduce the solar output in the first place.

[Deleted User]

What hard evidence has anyone to offer that a domestic battery is beneficial to the network or householder?

daughy

Sir Liamalot wrote: »

What hard evidence has anyone to offer that a domestic battery is beneficial to the network or householder?

Wild fires? Hurricanes? Earthquakes? If the grid is down a domestic battery is beneficial to the people?
Ireland doesn't suffer as much as others it's true.
But if you can offset the charges during the day by using solar and use your battery at night you'll really see a difference in your lecky bill.

[Deleted User]

daughy wrote: »

If the grid is down a domestic battery is beneficial to the people?

Two things there.
First due to anti-islanding protocols most on the market battery options will go offline and take the PV with it in the event of a powercut. The second is li-ion is too small and expensive to offer any considerable runtime in the event of a powercut for a gridder house.
I've 15kWh (usable) and it's a stretch to make it through one day

daughy wrote: »

But if you can offset the charges during the day by using solar and use your battery at night you'll really see a difference in your lecky bill.

Have you any hard evidence to support that there's any net gain after the system losses to make this viable?

I'm still running tests. The initial results are pretty damning but I have to change the parameters for a cleaner result. I'll have interesting data in a few days.

daughy

Sir Liamalot wrote: »

Two things there.
First due to anti-islanding protocols most on the market battery options will go offline and take the PV with it in the event of a powercut. The second is li-ion is too small and expensive to offer and considerable runtime in the event of a powercut for a gridder house.
I've 15kWh (usable) and it's a stretch to make it through one day

Have you any hard evidence to support that there's any net gain after the system losses to make this viable?

I'm still running tests. The initial results are pretty damning but I have to change the parameters for a cleaner result. I'll have interesting data in a few days.

For instance, my electricity meter readings since I installed my system are half of what they where last year, I only installed the system in the middle of August and I messed up doing an East array, for 1 string, South on the other, either way I'll change the east to west and add another 5 panels to it. So even though I messed up with my array, the meter readings are hard evidence that something is working?
Now add a battery to the mix and use it at night? And wollah.. We have lift off heuston..
Seriously though.. Its basic physics
Use the grid as a battery for the day and use your own battery at night. If the grid goes down entirely just cut back on your loads.

[Deleted User]

Basic physics? :rolleyes:
That's an opinion, there's no data to back up your claim.

Where's the quantifiable, measurable difference?
The Viability assessment?
Return of investment?
Cost of system versus cost of import?
Efficiency report.

Did you spend over the odds for a minor saving?
The lifetime cost of the system versus the savings made?

The comparable output to not have a battery in the middle?

daughy

daughy wrote: »

For instance, my electricity meter readings since I installed my system are half of what they where last year, I only installed the system in the middle of August and I messed up doing an East array, for 1 string, South on the other, either way I'll change the east to west and add another 5 panels to it. So even though I messed up with my array, the meter readings are hard evidence that something is working?
Now add a battery to the mix and use it at night? And wollah.. We have lift off heuston..
Seriously though.. Its basic physics
Use the grid as a battery for the day and use your own battery at night. If the grid goes down entirely just cut back on your loads.

You have 15kwh usable? So your using lead acid? You are only able to use 50 to 60% of the 30kwh battery. How much at the time did you spend on 30kwh of batteries? That's an expensive system to only be able to use 40% capacity to keep them batteries safe

[Deleted User]

It's a mixed LiFePO4 and lead acid on seperate hybrids that are synchronising and have AC coupled chargers. I'm less than €1k into the lead 10kWh (usable) 3.5kVA and about €6k into the LiFePO4 4kVA 3kWh (usable).
Lead I setup in two days, LifePO4 I built over some months.

I am running the test on LiFePO4 because no matter how much evidence I offer I expect that some clever clogs that read something off the internet will not accept that Lead can match Li-Ion in a sprint and outpace it in a marathon on a cost to cost comparison.
The efficiencies and utility are near identical.
The lead battery is almost a decade old and has rated capacity.
The LifePO4 is relatively new and has low hours.

The other 2kWh is compromising of other stand alone systems I can harmonise.

daughy

daughy wrote: »

You have 15kwh usable? So your using lead acid? You are only able to use 50 to 60% of the 30kwh battery. How much at the time did you spend on 30kwh of batteries? That's an expensive system to only be able to use 40% capacity to keep them batteries safe

Apologies my percentages are all over the place, usable to keep the batteries safe is approx 40%

[Deleted User]

Teaching yer grandma to suck eggs there pilgrim.
50% by the way.

daughy

Sir Liamalot wrote: »

It's a mixed LiFePO4 and lead acid on seperate hybrids that are synchronising and have AC coupled chargers. I'm less than €1k into the lead 10kWh (usable) 3.5kVA and about €6k into the LiFePO4 4kVA 3kWh (usable).
Lead I setup in two days, LifePO4 I built over some months.

I am running the test on LiFePO4 because no matter how much evidence I offer I expect that some clever clogs that read something off the internet will not accept that Lead can outpace Li-Ion in a marathon on a cost to cost comparison.
The efficiencies and utility are near identical.
The lead battery is almost a decade old and has rated capacity.
The LifePO4 is relatively new and has low hours.

The other 2kWh is compromising of other stand alone systems I can harmonise.

If your happy that's the main thing. Nobody wants to be wrong about an investment.
I do hope your lead acid lasts, truly I do as its 100 year old technology, and I do understand lithium is basically in its infancy stages compared to lead, it's just when you look at the first computer compared to ipad or new phone. It's night and day. And unkel mentioned he had no bms on his system, that's a very costly mistake for the sake of the price of a bms.. Not having a dig unkel, just not something I would do as lithium is too expensive to not have a bms on it.. My father has sealed lead acid running his off grid and he has no complaints, I was going to go lead as the cost for lithium is nuts, but knowing I can only discharge safely 40% of its capacity is a deal breaker for me.. Your tests are running for how long now?

antoinolachtnai

Sir Liamalot wrote: »

By greener I mean highest offset of hydrocarbon based fuel usage.
First of all there's triple the clean power on the network because double the solar and minus the associated battery losses and second hydrocarbons were not used to fabricate a battery to reduce the solar output in the first place.

And when the imbalance on the grid is such that there is more energy on the system than is needed?

There is no saving if the householder avoids having to buy a battery but the power companies end up buying a battery somewhere else, and has to build and operate low efficiency OCGT In order to match the PV when the sun is low or occluded.

There are wider public policy objectives related to battery storage. It’s not as simple as making more money in the short term.

[Deleted User]

daughy wrote: »

If your happy that's the main thing. Nobody wants to be wrong about an investment.

I'm not trying to make money powering my house with them. That's a side project because I am very tired of the misinfomation in the industry.

daughy wrote: »

I do hope your lead acid lasts, truly I do as its 100 year old technology,

Closer 150. I think that makes it a proven tech.

daughy wrote: »

it's just when you look at the first computer compared to ipad or new phone.

Sure that Ferrari is fast, but it's not €250 000 fast.

daughy wrote: »

unkel mentioned he had no bms on his system,

Penny to a pound Unkel is the BMS.

daughy wrote: »

knowing I can only discharge safely to 40% of its capacity is a deal breaker for me..

50% of 20kWh is a lot more than 70% of 4.3kWh and a fraction of the cost.

daughy wrote: »

Your tests are running for how long now?

I'd say about a decade now.

With regards to hybrid inverters about a fortnight.

daughy

Sir Liamalot wrote: »

Teaching yer grandma to suck eggs there pilgrim.
50% by the way.

Had to laugh at that one. Nice 1 Liam. Can't seem to find emojis on this site. Would be laughing..
Anyway 50%. Might keep the lights on for another hour

[Deleted User]

antoinolachtnai wrote: »

And when the imbalance on the grid is such that there is more energy on the system than is needed?

HVDC interconnector. Grid batteries are a great idea. Domestic batteries not so much.

antoinolachtnai wrote: »

There is no saving if the householder avoids having to buy a battery but the power companies end up buying a battery somewhere else, and has to build and operate low efficiency OCGT In order to match the PV when the sun is low or occluded.

Grid operators are a lot smarter/well-informed than you and I.

antoinolachtnai wrote: »

There are wider public policy objectives related to battery storage. It’s not as simple as making more money in the short term.

It's not about money, that's just an appraisal device. It's about lowering carbon dioxide production.

antoinolachtnai

You haven’t really presented your reasoning.

You are very concerned about round-trip efficiency when it comes to household batteries but you don’t seem to have accounted for the much larger losses for grid batteries.

Given that, and given that we want to maximize the CO2 saving per euro spent would it not make more sense to put the money being spent by householders on domestic PV into buying a share of a grid scale PV farm? You could get maybe double the kW for the same money that way.

It is heartening that you accept the wisdom of the system operators without qualification.

You haven’t answered my questions from the outset. As a result I just can’t understand your certainty that domestic batteries don’t and will never make sense.

I can’t see much point in discussing it further until you explain your grid level modeling.

[Deleted User]

antoinolachtnai wrote: »

You haven’t really presented your reasoning.

I'm currently waiting on data that nobody else wants to confront or offer. Everyone just seems to think x+y=z without any validation.

antoinolachtnai wrote: »

You are very concerned about round-trip efficiency when it comes to household batteries but you don’t seem to have accounted for the much larger losses for grid batteries.

Flow batteries, mechanical batteries and pumped hydro are dominating li-ion and none of them fit in a house.
The grid is a battery, unify and increase distribution internationally. How are the losses greater when there's a much vaster power on demand load profile? Any data on that?

antoinolachtnai wrote: »

Given that, and given that we want to maximize the CO2 saving per euro spent would it not make more sense to put the money being spent by householders on domestic PV into buying a share of a grid scale PV farm? You could get maybe double the kW for the same money that way.

Exactly, everyone seems concerned about storage when we haven't enough generators. The battery is the last piece of the puzzle.

antoinolachtnai wrote: »

It is heartening that you accept the wisdom of the system operators without qualification.

Clearly not the Irish as they're more concerned about defending their market than progressing the tech, at least they make an informed viability assessment before committing.

antoinolachtnai wrote: »

You haven’t answered my questions from the outset. As a result I just can’t understand your certainty that domestic batteries don’t and will never make sense.

Which question?
And in return why are you so convinced it is practical, have you based it on any evidence?

antoinolachtnai wrote: »

I can’t see much point in discussing it further until you explain your grid level modeling.

I can see a substantial amount of power being generated getting lost in transistor heatsinks when it could be going to our loads instead for a lower upfront cost.

So if we could take all the taxpayers' money SEAI are throwing in a hole and bribe the ESB to get off their holes and offer a fair market price for homegrown power then the battery would be out on it's ear without a second thought. Would you agree?

Or how about cultivating the West coast offshore with that money instead and exporting power instead of crying that our transformers are too old and few?
We've the best wind in Europe outside of Scotland and have you seen where we are on the generation charts? It's an embarrassment.

antoinolachtnai

Sir Liamalot wrote: »

I'm currently waiting on data that nobody else wants to confront or offer. Everyone just seems to think x+y=z without any validation.

The same is going on everywhere. The idea that just because PV is providing electricity, that it is therefore making a significant contribution to the grid is the same sort of thinking you describe. Not all energy sources are equal in value.

Flow batteries, mechanical batteries and pumped hydro are dominating li-ion and none of them fit in a house.
The grid is a battery, unify and increase distribution internationally. How are the losses greater when there's a much vaster power on demand load profile? Any data on that?

The grid isn't a battery. It's a distribution system. Unlike the food distribution network or the gas grid, it has basically no inherent storage capacity.

Grid connections to abroad are expensive to build. Where are all these grid connections supposed to connect to at either our end or the far end? Running a grid connection to GB won't do you much good if they don't have capacity to match it.

Clearly not the Irish as they're more concerned about defending their market than progressing the tech, at least they make an informed viability assessment before committing.

What grid in the world has more asynchronous renewable at peak than Ireland's?

Which question?

I asked you to provide your model at grid level.

And in return why are you so convinced it is practical, have you based it on any evidence?

I never said that it was practical at all. I just wanted to understand your detailed reasoning taking into account all the factors why you think it's not practical under any circumstances.

There are very compelling things about domestic batteries. They provide capacity, which PV does not. They can help support the distribution network at times of high demand. They can provide benefits at the times of year when electricity is most needed, unlike PV or PV alone.

I can see a substantial amount of power being generated getting lost in transistor heatsinks when it could be going to our loads instead for a lower upfront cost.

The nature of electricity generation, especially from sun and wind collectors is that there is going to be waste. There are going to be times when there is just too much. The whole difficulty with planning generation is that you need a mix of sources. There is no single strategy which will give you everything you need at anything like an optimal price.

So if we could take all the taxpayers' money SEAI are throwing in a hole and bribe the ESB to get off their holes and offer a fair market price for homegrown power then the battery would be out on it's ear without a second thought. Would you agree?

The SEAI has not really spent that much money. The amount is tiny in the context of the overall cost of electricity and the size of the PSO fund (hundreds of millions per year. Maybe you can tell us how much, but I think it is in the order of 5 to 10 million euros. This is a very small program in the overall scale of things. The level of funding required to pay a subsidy for home-PV electricity would be an awful lot more than that.

Sure, the metering is a mess, but that isn't SEAI's fault.

The ESB doesn't set the price for electricity and hasn't for years.

How would you calculate a fair price for homegrown power? How much would it be?

Or how about cultivating the West coast offshore with that money instead and exporting power instead of crying that our transformers are too old and few?
We've the best wind in Europe outside of Scotland and have you seen where we are on the generation charts? It's an embarrassment.

Offshore wind probably makes more sense near the population centres than off the western coast, certainly with the current technology.

It may well end up being a choice between funding offshore wind and funding domestic PV. In the end, all this has to be paid for by the bill payer.

unkel

daughy wrote: »

unkel mentioned he had no bms on his system, that's a very costly mistake for the sake of the price of a bms.. Not having a dig unkel, just not something I would do as lithium is too expensive to not have a bms on it.

It's all relative. You will learn once you start playing with this stuff. A good BMS that will protect my battery costs more than my battery cost. So investing in one would be a terrible waste of money. A half decent BMS doesn't cost much and will protect the battery from overvolt, undervolt, etc. and it will cut off the battery when the cell imbalance becomes too big. It will do a very poor job at balancing the cells though. And my inverter already has the job of overvolt, undervolt, etc. protection and my battery is fused for short circuits / over current, etc. I had a half decent BMS but I decided I would personally take over its function. Liam got it in one

[Deleted User]

antoinolachtnai wrote: »

The grid isn't a battery. It's a distribution system. Unlike the food distribution network or the gas grid, it has basically no inherent storage capacity.

For intents and purposes is can be. We could send wind to France and get sunlight in return later that day.

antoinolachtnai wrote: »

Grid connections to abroad are expensive to build. Where are all these grid connections supposed to connect to at either our end or the far end? Running a grid connection to GB won't do you much good if they don't have capacity to match it.

Think bigger send it to France cut out the middle man. We have to get over this islander mentality. Once it's on the mainland it can go to China on HVDC. Then it's way more interesting with differential daylight hours.

antoinolachtnai wrote: »

What grid in the world has more asynchronous renewable at peak than Ireland's?

Most of them.

Share_of_energy_from_renewable_sources_2018_infograph.jpg

antoinolachtnai wrote: »

I asked you to provide your model at grid level.

Haven't got one, the losses are lower sending power to the grid instead of semi-conductors.

antoinolachtnai wrote: »

I never said that it was practical at all. I just wanted to understand your detailed reasoning taking into account all the factors why you think it's not practical under any circumstances.

I can't beat pure solar on bang for buck with any alternative.
We do not build off-grid around a battery we build it around the generators with a battery. You are doing it right when you are not using the battery. This significance of the battery is misunderstood. What good is a cup without a water source?

antoinolachtnai wrote: »

There are very compelling things about domestic batteries.

Seems to be the cost outweighs them.

antoinolachtnai wrote: »

They provide capacity, which PV does not.

So does the grid but cheaper

antoinolachtnai wrote: »

They can help support the distribution network at times of high demand.

Why would I support the grid when they're short-changing me, increasing the wear and tear and have they not got their own storage?

antoinolachtnai wrote: »

They can provide benefits at the times of year when electricity is most needed, unlike PV or PV alone.

This does not fit an economic or ecological debate. As needs must when the Devil drives.

antoinolachtnai wrote: »

The nature of electricity generation, especially from sun and wind collectors is that there is going to be waste. There are going to be times when there is just too much. The whole difficulty with planning generation is that you need a mix of sources. There is no single strategy which will give you everything you need at anything like an optimal price.

Agreed but this is not a concern of the micro-generator and there is such a low uptake of renewables in this country, we have an awful lot of hydrocarbons to reduce use of before that's ever an issue.

I fit diesels then I reduce their runtime. Reliablity comes before hippy.

antoinolachtnai wrote: »

The SEAI has not really spent that much money. The amount is tiny in the context of the overall cost of electricity and the size of the PSO fund (hundreds of millions per year. Maybe you can tell us how much, but I think it is in the order of 5 to 10 million euros. This is a very small program in the overall scale of things.

Pardon me but there's an awful lot better ways to spend it, before we even get started with all the chancers hiking the install prices way above their value.

antoinolachtnai wrote: »

The level of funding required to pay a subsidy for home-PV electricity would be an awful lot more than that.

Power on the network is a sellable and more valuable commodity than what we're doing with it.

antoinolachtnai wrote: »

How would you calculate a fair price for homegrown power? How much would it be?

ESB import open market value.

antoinolachtnai wrote: »

Offshore wind probably makes more sense near the population centres than off the western coast, certainly with the current technology.

It may well end up being a choice between funding offshore wind and funding domestic PV. In the end, all this has to be paid for by the bill payer.

I don't mind paying for less coal burning. I mind paying for other peoples' green credentials that could perform better overall by throwing half of their hardware away.

[Deleted User]

unkel wrote: »

A good BMS that will protect my battery costs more than my battery cost.

Yurp. I've learned that one. The battery has to be really expensive to justify it.

I bought a loada posh balancers, never use them. The cells don't go outtov balance once they are balanced. I can't stand the noise of them. High frequency singing...nauseating!