Someone criticise my solar panel plan!!

davidivad

Hi,

I'm going to get solar panels installed in my house. My current electricity yearly usage is 7000kwh.

My plan is to install an 8kw ground mounted array, a 10kw battery with a 5kw inverter( or 6kw if i can get it).

I plan to use the energia night rate plan which costs circa 10c a unit when using electricity between 2am-5am.

The plan is to charge the battery on the cheaper night rate cost every night, use that to run the house for most of the day and then sell the electricity I make during the day back to the grid for circa 24c a unit. Obviously if this worked I would make a nice profit in the summer months and that might offset the cost of my electricity in the winter months.

So go for it, criticise my plan and tell me where I'm wrong and what won't work.

Is there something I am missing here, is there a limit to how many units you can return to the grid during the day?

Jonathan

At 7MWh a year, your 20 hour daily usage (Energia EV Tariff is 4 hours btw) is a bit high to expect it to fit into a 10kWh battery, particularly in the depths of winter. So once you factor buying some day rate units into your payback calculations, truck on.

Dr Turk Turkelton

Sh1t plane- can't even see any wings.

There you are criticised.

yankinlk

very similar usage to my setup. i have a smaller battery 5kwh and smaller array at 6.5kw plus im east west not south facing. You didnt say what your aspect was. You are fine with that plan imho. I dont think it makes sense financially to go for say a 20kwh battery just to try and use 100% night rate. A little day rate (cooking for example) is fine imho once you can try and offload some stuff (washing, drying, battery charging) to night rate.

Do i pay a little for electricity? Yes, only in winter though. But do i have a huge sunk cost in a battery? No. Your strategy is fine. If you have a higher day usage and refuse to move anything to nighttime then a bigger battery makes sense i guess.

davidivad

https://www.boards.ie/discussion/comment/121648378#Comment_121648378

My aspect is essentially whatever I want it to be as its a ground mounted system and I have a field beside the house, that actually slopes south.

I agree with what you say about not needing a huge battery, however I want my net yearly bill to be €0 essentially, and I plan on adding electric cars in time.

Does anyone here know if there's a limit with the amount of units you can export to the grid at peak heat in the summer? Does the inverter put a limit on it? Have the ESB a limit on it?

con747

https://www.boards.ie/discussion/comment/121649005#Comment_121649005

New regs came in about inverter size so you will be restricted.  https://www.esbnetworks.ie/new-connections/generator-connections-group/micro-generators- Unless you go for an NC7 which costs about €1000 with no guarantee of connection.

davidivad

https://www.boards.ie/discussion/comment/121649204#Comment_121649204

Hi, thanks for that, this seems to be the limit to what you can upload to the grid:

• 25 amperes (≈6kVA) at low voltage [230 volts] when the connection is single phase

However I do not understand it as its in terms of amps and volts instead of kilowatts.

Can you explain??

con747

https://www.boards.ie/discussion/comment/121649234#Comment_121649234

On the NC6 you are restricted to the 5kW inverter in that link so will only be able to export that amount to the grid afaik.

Edit, in case I got your question wrong there is no limit on the amount of units you can export just the inverter size which would export them.

davidivad

That makes sense, thanks for the replies. So with an 8kw system, if you were in a midsummers day and wanted to upload 8kw at one time, you are restricted to only 5kw? with the other 3kw wasted if the batter was already full.

Maybe a 5kw battery would suit me better so....

con747

https://www.boards.ie/discussion/comment/121649672#Comment_121649672

A bigger battery like some here have and fill it up either via solar or very low night rates and either use the power or sell it back to the grid for a profit and rinse and repeat. Have a look at some of the other threads like this one https://www.boards.ie/discussion/2058246061/10kwh-lifepo4-diy-battery-addition-here-is-my-write-up#latest and some here https://www.boards.ie/categories/renewable-energies

graememk

Battery capacity is in kWh (measure of energy)

Power is in kW

If you generate 1kW for 1hour you have 1kWh.

How fast the battery can charge or discharge also depend on the inverter!

slave1

Ditch the battery plan and go for 20kWh DIY job, few threads here on how to do it

davidivad

Is it possible to charge a 15kw battery fully from empty on a 3 hour night rate or does it need longer to charge, or is it dependant on the inverter?

10-10-20

Personally I'd go for a slightly larger battery, 15kWh, and use forecast based overnight charging to take on a minimal charge based on the expected solar generation for the next day. That might be the best strategy as there's every chance of demand-based export limits in the future years.

davidivad

Thanks for the comment guys. From all my research and quotes, installers with the huawei system seem to be swearing by them. Are they much better than the solis/dyness system or is it all the same really. I see you can get up to 10.44kw array with the huawei system but not as much with any other system. Huawei are expensive though.

Anyone fill me in on the best option?

con747

https://www.boards.ie/discussion/comment/121692476#Comment_121692476

@HotSwap is your best bet there.

JVince

Don't expect 24c for your electricity.

Current wholesale rates are 12c.

Business "market rate" electricity was 13.5c in January (plus transmission charges of about 10c)

Redo calculations on 10c-12c a unit feed in price.

HotSwap

https://www.boards.ie/discussion/comment/121692491#Comment_121692491

Huawei 5kW inverter - 850 (ironically the 6kWh unit is less now) 100 euro less.

5kwh battery module - 1900 each

battery bms (need 1 per 3 battery modules) - 750

Dunno where your getting your Dyness / pylon prices from; but I bet they aren’t significantly less than this.

i guess you might save a bit as you don’t need the BMS as the low voltage battery’s connect directly to the hybrid inverter.

for me it’s all about the peak discharge rate of the huawei battery. I’m never pulling from grid at peak times.

davidivad

https://www.boards.ie/discussion/comment/121692568#Comment_121692568

Thanks for those prices @HotSwap .Optimiser needed with Huawei that wasn't priced with my solis quotes. Planning a 24 panel array so optimisers also add over €1,000 and with solis can only get 9.57 array so 2 less panels also. I suppose, I'm not exactly comparing like with like.

Is the huawei 6kw inverter a better bet? should I mention this to my installer?

HotSwap

https://www.boards.ie/discussion/comment/121692666#Comment_121692666

It’s better but technically not allowed under current regs.

only reason for the optimisers is to allow more to be connected? No shading?

slave1

It's allowed, just not under the free NC6 submission, would require a NC7 + Cash

davidivad

https://www.boards.ie/discussion/comment/121692720#Comment_121692720

Yes optimiser allow more to be added, I think I have it in a place with no shading so maybe the optimisers are costing me too much. Am I correct in thinking the allow me to go from 20 panel to 24 panel system?