Solar panels and battery - any real world reccomendations?

[FirebarUK]

Very few batteries will discharge at above 3.5kW, unless you are using more than one or a Tesla PW2.

For your solar you can just use two arrays one that is feeding back the the grid at 3.68kW and then one isolated if you really want a full 10kWp system. Adds cost, but so does having a larger than normal array. It's always good having more generating capacity if it can be supported, but you need to weight that up with what the DNO is allowing you to do on your local circuit.

How much energy do you currently use overall, and how much of that is inside of sunshine hours?

The battery was either PW2 or SolarEdge 10kWh, the latter can provide continuous output at 5kW according to the datasheet. Our energy usage is fairly flat through the day, all things considered. So we'd be needing plenty of storage. The plan all along was to go big on generation and get multiple batteries but then if we have more than one, presumably only one could discharge at a time (and limited).

OK thought about it a little and realised you can probably generate more (have more panels) but have a limiter and battery setup so that the export is restricted?

As it has been in place for years I imagine it has to be so otherwise you would see less coverage on roofs and the installers would be plastering disclaimer limitations etc.

Right but limiting through the inverter would also limit power going into the home from the PV system, I think?

You can have a 10kW inverter if you wish, and just limit its abilty to export to the grid at no more then 3.68 etc. Anything generated that isn't used or stored in the battery above the 3.86 figure, would just be wasted if you had spare generation.

As above. So I think going back to Journey's post, we'd need to have an isolated system somehow?

 

[94JDH]

The battery was either PW2 or SolarEdge 10kWh, the latter can provide continuous output at 5kW according to the datasheet. Our energy usage is fairly flat through the day, all things considered. So we'd be needing plenty of storage. The plan all along was to go big on generation and get multiple batteries but then if we have more than one, presumably only one could discharge at a time (and limited).



Right but limiting through the inverter would also limit power going into the home from the PV system, I think?



As above. So I think going back to Journey's post, we'd need to have an isolated system somehow?

https://www.westernpower.co.uk/export-capping

 

[Ron-ski]

What we need is a crypto farm to use the excess generation that can't go to the grid, and therefore earn from it

 

[gpuerrilla]

Page not found on WP fast track.

From what I am reading, as its a single phase install below 16a which complies to the installers spec (Gx standards) the DNO accepts the certification by the installer within the 30 day period. If there were many issues arising from solar installations it should be more well known you would have thought?

Will also see what the installers say during the quotations, but others must have committed beyond this already or have experience.

What we need is a crypto farm to use the excess generation that can't go to the grid, and therefore earn from it

 

[94JDH]

Export Limiting
Customers who are seeking to increase the amount of generation or energy storage installed but have been advised an increase in export capacity will require costly or time bound upstream reinforcement, may choose to restrict the net export of their connection rather than wait for or contribute to the reinforcement.

An export limitation scheme measures the Apparent Power (kilowatts) at the exit point of the installation and then uses this information to either restrict generation/energy storage output or increase the customer demand in order to prevent the Agreed Export Capacity from being exceeded.

These schemes allow network operators to continue to maintain the supply security of existing customers whilst also enabling new generation/energy storage onto the network.

 

[BUDFORCE]

Export Limiting
Customers who are seeking to increase the amount of generation or energy storage installed but have been advised an increase in export capacity will require costly or time bound upstream reinforcement, may choose to restrict the net export of their connection rather than wait for or contribute to the reinforcement.

An export limitation scheme measures the Apparent Power (kilowatts) at the exit point of the installation and then uses this information to either restrict generation/energy storage output or increase the customer demand in order to prevent the Agreed Export Capacity from being exceeded.

These schemes allow network operators to continue to maintain the supply security of existing customers whilst also enabling new generation/energy storage onto the network.

Sounds like some capitalist pig shareholder don't want the average Joe to cut into their slice.

 

[FirebarUK]

Export Limiting
Customers who are seeking to increase the amount of generation or energy storage installed but have been advised an increase in export capacity will require costly or time bound upstream reinforcement, may choose to restrict the net export of their connection rather than wait for or contribute to the reinforcement.

An export limitation scheme measures the Apparent Power (kilowatts) at the exit point of the installation and then uses this information to either restrict generation/energy storage output or increase the customer demand in order to prevent the Agreed Export Capacity from being exceeded.

These schemes allow network operators to continue to maintain the supply security of existing customers whilst also enabling new generation/energy storage onto the network.

Yup, I spoke with the solar installer and DNO. Unfortunately there is nothing we can do as limiting through the inverter is possible but that in turn limits what we can consume in the house. We don't really want to contribute to upstream reinforcement and even then it would only take us to 8kW unless we did even more work on the network infrastructure (£80k? £100k?). So, solar is a no-go for us, we'd have to consider fully off-grid systems but tbh with a bit of reading the tech just doesn't seem to be there yet for a household our size.

Sounds like some capitalist pig shareholder don't want the average Joe to cut into their slice.

The network was never built with micro-generation in mind so it's quite understandable, although a company would have really no incentive to upgrade the network because they'd rather you buy energy vs. make it yourself. Chicken and egg. I'm probably more annoyed that we hit actual reality here vs. government and industry brochures

 

[keyser van someone]

Average payback on solar used to be between 11 and 13 years. Given the rising cost of energy, what is the current payback on Solar ?

My elec went up by 41% so 13 years minus 41% = 7.67 years

Standing charge doubled £90 to £180 but you will still be charged for that.

edit: actually I was over thinking that, when I was on a tariff I was paying half what I am now, so 6.5 years for solar to pay for itself at currently electric prices woop.

 

[gpuerrilla]

Yup, I spoke with the solar installer and DNO. Unfortunately there is nothing we can do as limiting through the inverter is possible but that in turn limits what we can consume in the house.

Are you not using enough yourself, or cannot store enough in batteries then?

 

[katie279]

Ok guys, had quotes - looking for final thoughts before committing!

Annual usage: 12,000kw (likely to rise next year if we go for high temp air sourced heat pump) - also have an EV
Daily usage: ~35kw

Quote:
Solar - 7.2kw
Battery - 9.5kwh
Inverter - 5kw

Estimate is that the solar should generate ~ 6,500kw per year.

I'd like to maximise the decoupling of high cost energy.

I'm guessing with Octopus Go, I'd be able to top up 4 hours of energy - not sure how I work out the limit per hour, but given my car tops up at around 8kwh, I'll assume that - meaning I could theoretically charge up 32Kwh of battery at cheap rate and use this throughout the day.

Questions:
- Should I go with 2 x 9.5kwh? It feels like this would help a lot with energy cost as it'd mean 50%+ of my energy could be at cheap energy rate.
- Should I add a second inverter? It feels a waste to clip solar energy at 5kw when I have 7.2kw potential, but not sure how often it'd actually reach this (in east scotland!)

Thanks in advance!

 

[94JDH]

Ok guys, had quotes - looking for final thoughts before committing!

Annual usage: 12,000kw (likely to rise next year if we go for high temp air sourced heat pump) - also have an EV
Daily usage: ~35kw

Quote:
Solar - 7.2kw
Battery - 9.5kwh
Inverter - 5kw

Estimate is that the solar should generate ~ 6,500kw per year.

I'd like to maximise the decoupling of high cost energy.

I'm guessing with Octopus Go, I'd be able to top up 4 hours of energy - not sure how I work out the limit per hour, but given my car tops up at around 8kwh, I'll assume that - meaning I could theoretically charge up 32Kwh of battery at cheap rate and use this throughout the day.

Questions:
- Should I go with 2 x 9.5kwh? It feels like this would help a lot with energy cost as it'd mean 50%+ of my energy could be at cheap energy rate.
- Should I add a second inverter? It feels a waste to clip solar energy at 5kw when I have 7.2kw potential, but not sure how often it'd actually reach this (in east scotland!)

Thanks in advance!

Hi,

Your usage is a similar range to mine. I've a similar 7.2kW on order, with two inverters and a battery of same size to each to maximize both solar and off peak from Octopus Go.
I also have an EV but will just charge this on the 4 hour window as necessary.
For me, maximizing the generation is essential as is the night rate. For two batteries of that size ( same as me) two inverters are necessary to achieve full charge if there is little solar generation in the depths of winter or poor days.

 

[GinG]

So just to update I've just signed the forms for the following:

4kwh Solar
5.2 GivEnergy battery plus 3.6 Inveter.

Got the fella to throw in bird protection and paying £7582.

We bought a new caravan so budget dwindled a bit so this is more inline with the budget than to a higher spec.

Plan will be to add another battery in a few years when things settle down.

I'm happy with the spec and compromise with the budget we had.

 

[TNA]

So just to update I've just signed the forms for the following:

4kwh Solar
5.2 GivEnergy battery plus 3.6 Inveter.

Got the fella to throw in bird protection and paying £7582.

We bought a new caravan so budget dwindled a bit so this is more inline with the budget than to a higher spec.

Plan will be to add another battery in a few years when things settle down.

I'm happy with the spec and compromise with the budget we had.

Nice price, but say you got the washing machine on or cooker and put on kettle you will be well over 3.6 no? Unless I have misunderstood how it all works, one would want no less than 5, ideally even more so you can draw more juice at once from the battery.

But yeah, good price as you say if you can work around it.

 

[katie279]

Hi,

Your usage is a similar range to mine. I've a similar 7.2kW on order, with two inverters and a battery of same size to each to maximize both solar and off peak from Octopus Go.
I also have an EV but will just charge this on the 4 hour window as necessary.
For me, maximizing the generation is essential as is the night rate. For two batteries of that size ( same as me) two inverters are necessary to achieve full charge if there is little solar generation in the depths of winter or poor days.

Ah, really useful - so to be clear, the inverters will also increase the amount you can draw from the grid (ie 2 x 5kw would let you draw 10kw per hour = 40kwh of battery charge potential? I thought from earlier post in this thread that it would only increase my max solar charge rate). If this is so, then definitely going for 2 x inverters and 2 x batteries for the winter months as you say!

 

[94JDH]

Ah, really useful - so to be clear, the inverters will also increase the amount you can draw from the grid (ie 2 x 5kw would let you draw 10kw per hour = 40kwh of battery charge potential? I thought from earlier post in this thread that it would only increase my max solar charge rate). If this is so, then definitely going for 2 x inverters and 2 x batteries for the winter months as you say!

Depending on which inverter they have quoted you, the following maximum is possible:
1st Generation 3.6kW inverter has max 2.6kW charge rate per battery, so two would give you a theoretical max of 20.8kW in the 4 hour window (10.4kW per inverter).
2nd Generation 3.6kW inverter ( expected June) has a max 3.6kW charge rate per battery, so two would give you a theoretical max charge of 28.8kW in the 4 hour window (14.4kW per inverter).
With two inverters you also benefit from the double the discharge rate if the house demands it so 1st Generation inverters ( 2 x 2.6kW) or 2nd generation ('2 x 3.6kW).

2 x 5kW inverter would be overkill for the 7.2kW solar array, and would be better with 2 x3.6kW if going that route. The 5kW inverter doesn't charge the batteries any faster than the 3.6kW version and wouldn't be as efficient in dual configuration in relation to your 7.2kW array.

 

[GinG]

Nice price, but say you got the washing machine on or cooker and put on kettle you will be well over 3.6 no? Unless I have misunderstood how it all works, one would want no less than 5, ideally even more so you can draw more juice at once from the battery.

But yeah, good price as you say if you can work around it.

If I was looking to go independent from the grid then yes...and even consider 2 X inverters to take the load however in our household it's very rare that we have everything running all at once.

Washing machines will be fine to run with the smaller inverter, same with cooker. The time it takes for the kettle to boil means pence from the grid anyway.

The main thing to look at the inverter is the charge rates so in the winter you can take advantage of the 4/5 HR window to charge battery. Even with the smaller inverter if be able to fill 12kwh battery no bother.

Everyone is different but this is how I've worked my usage out:

Car = always charging from grid overnight.

House base load = average 120w

10x 400w should still allow the house to tick over even in winter.

Washing machine and dishwasher can be put on timers so I can take advantage of sunny days in winter or still run overnight cheaply.

The battery will take the load from 5-6pm to 12.30am and then the house will tick over on cheap leccy until 4.30am, the battery will be charged and not discharging between this window, the battery will take the small load until we wake up around 6am.

If I had unlimited funds I'd love to go all out but you need to to sensible and having this and a battery is far better than just panels or nothing at all.

 

[FirebarUK]

Are you not using enough yourself, or cannot store enough in batteries then?

I'm told it's not the issue, apparently like it or not I simply cannot consume or draw from the batteries more than this 3.68kW because of potential of it going back to the grid.

 

[katie279]

Depending on which inverter they have quoted you, the following maximum is possible:
1st Generation 3.6kW inverter has max 2.6kW charge rate per battery, so two would give you a theoretical max of 20.8kW in the 4 hour window (10.4kW per inverter).
2nd Generation 3.6kW inverter ( expected June) has a max 3.6kW charge rate per battery, so two would give you a theoretical max charge of 28.8kW in the 4 hour window (14.4kW per inverter).
With two inverters you also benefit from the double the discharge rate if the house demands it so 1st Generation inverters ( 2 x 2.6kW) or 2nd generation ('2 x 3.6kW).

2 x 5kW inverter would be overkill for the 7.2kW solar array, and would be better with 2 x3.6kW if going that route. The 5kW inverter doesn't charge the batteries any faster than the 3.6kW version and wouldn't be as efficient in dual configuration in relation to your 7.2kW array.

Ah ok - really helpful, so think this is the inverter: https://www.givenergy.co.uk/pdf/Version 2.0/Hybrid Inverter Gen 2.pdf

So in summary (just to check I'm understanding):
- 2 x 5kW for solar - No - ie overkill (although not impossible I could install more panels in future, so might have a slight advantage)
- 2 x 5KW for overnight battery charging - Yes - increases the maximum amount I can store
- 2 x kw for discharge - Yes - we regularly use more than 4-5 kW so would allow the house to continue in a power cut (out of interest, what actually happens if I have, say a 3.6Kw discharge rate and house needs 5kW - does electricity trip?

 

[TNA]

If I was looking to go independent from the grid then yes...and even consider 2 X inverters to take the load however in our household it's very rare that we have everything running all at once.

Washing machines will be fine to run with the smaller inverter, same with cooker. The time it takes for the kettle to boil means pence from the grid anyway.

The main thing to look at the inverter is the charge rates so in the winter you can take advantage of the 4/5 HR window to charge battery. Even with the smaller inverter if be able to fill 12kwh battery no bother.

Everyone is different but this is how I've worked my usage out:

Car = always charging from grid overnight.

House base load = average 120w

10x 400w should still allow the house to tick over even in winter.

Washing machine and dishwasher can be put on timers so I can take advantage of sunny days in winter or still run overnight cheaply.

The battery will take the load from 5-6pm to 12.30am and then the house will tick over on cheap leccy until 4.30am, the battery will be charged and not discharging between this window, the battery will take the small load until we wake up around 6am.

If I had unlimited funds I'd love to go all out but you need to to sensible and having this and a battery is far better than just panels or nothing at all.

That’s fair enough

 

[gpuerrilla]

I'm told it's not the issue, apparently like it or not I simply cannot consume or draw from the batteries more than this 3.68kW because of potential of it going back to the grid.

Yes I see, its a pain as I think this applies to most connections now, but if your lucky to be near an industrial connection or plumbed in to meatier transformer you wouldnt know until you scope it out like this exercise.