Options for 8KwP Array with battery storage 60m away

elrao

Currently planning our solar install and have two main questions.

My situation is that I have a roof that can take 21 panels, so ~8KwP, located about 60m from the electricity meter.  We have two armoured cables running from the meter, one to the house and the other to the outbuilding.  I need a battery solution that can power both, which I believe means we need to install a "gateway" device near the meter that connects to the batteries to tell them when to charge, discharge etc.  If like 15KwH or more of storage.

Tesla and Huawei require a physical cable between their respective gateway and the battery.  This is problematic with the Huawei hybrid inverter system I've been quoted on, as the battery would be 60m from where the gateway needs to be.  With Tesla however the batteries can be located in the garage a few meters from the meter.

Are there any other options for AC coupled systems that would allow me to locate both thr gateway and the batteries near the meter and away from the solar array?  Or a hybrid system that uses a wireless connection, or communicates over the power cable?

Second up, I've been quoted for Enphase and an 8kw Solar Edge - but keen for recommendations for an 8Kw Inverter to see how much I could save over EP or SE.

ABrass

For DC batteries they need to be near the inverter and you would need a CT clamp at the meter to tell when to charge or discharge.

For AC batteries, just install them by the meter.

ispookie666

Why not run DC cable till your meter and have the inverter closer to the meter? The power loss will.be minimal for the DC vs AC system for 60m run. 

elrao

ispookie666 said:

Why not run DC cable till your meter and have the inverter closer to the meter? The power loss will.be minimal for the DC vs AC system for 60m run. 

You mean put a hybrid inverter in the garage, 60m away from the solar array, running DC over that distance?

Didn't realise that was an option!

ABrass

The DC from your panels would be in the region of 300V, if anything that's better than running AC over that distance. Although you're probably outside the specifications and might be better off using heavier gauge wires.

elrao

Will discuss with the installer, as there's obviously a cost to burying a high voltage cable across the garden.  

ispookie666

elrao said:

Will discuss with the installer, as there's obviously a cost to burying a high voltage cable across the garden.  

You can use SWA cable, which will be used anyway for your install. 

Heedtheadvice

Running either an AC or DC cable at high voltage ( relatively speaking  as electrically  mains is considered in engineering terms low voltage even 250v!) outside requires special consideration such as armoured cable,  buried (if it is to be ground 'level' ), at or below a specific depth and taped to be identified as  minimum.

For 'high' power (8kW or 15kWh storage that might supply  a similar amount of current I.e.  over 30 A) also requires heavier cable to avoid loss of voltage. That loss of voltage if not kept very small will affect generation power, battery power capability and battery charge. Certainly low voltage (48V) batteries are kept close to the charger inverter for that reason I.e. a metre or two is typical. Certainly not 60m. Higher voltage batteries can still be a problem at that distance but less so.

Now you might already have that cable of sufficient size for your house and outbuilding  mains supply but unless your generation/storage and inverter/charger is connected at AC to one of theose cables AND  that cable has sufficient extra required capacity you may need new or uprated cabling.

If the inverter/charger is distanced from the panels  the batteries or both then you would need similarly heavy and separate armoued cable to carry the DC currents.

It will need an electrically competent person to design to meet standards and performance criteria. Expensive(ish) cable and extra design cost plus probably trench installation. (6mm armoured about £300 per 100m drum alone) adds to system costs.

Suggestion:

Consider a rethink. Given you seem to have plenty of area think about having the panels and batteries both close(er) to your meter point/consumer unit such as with a ground mounted set of panels and batteries in a shed  with inverter/charger co-located?

Communication is much less of an issue normally and cheaper depending upon if it is proprietary or not...

... as one caveat.

elrao

Unfortunately there's no option to put the panels any closer, it is the only roof that sees sunshine.  Roof of the house is almost constantly in shade from some large trees.  

The only area they could be ground mounted is the other side of the same building, so further away.

elrao

Small update

Now have a price for 21 400w panels with Solar Edge optimisers and an 8kw Inverter and the same panels with an 8kw Solis.

The solar edge is about £1500 more (which looks about right based on additional cost of 22 optimisers and the difference in cost between the SE and Solis inverters.

Not sure how much more power the SE would generate, but even if it's 500Kw per year, at 40p (off peak rate) that's £200 a year, so 7.5 year pay back.

Also had a price of £10,200 for 15kwh Huawei AC coupled battery.  Making it £800 cheaper than the 13.5Kwh Tesla.  Waiting for confirmation on costs to double up the Huawei, it's £9k for a second Powerwall, but imagine the second Huawei is going to closer to £10k.

Any thoughts on those options (or alternatives)?

QrizB

elrao said:

Not sure how much more power the SE would generate, but even if it's 500Kw per year, at 40p (off peak rate) that's £200 a year, so 7.5 year pay back.

40p/kWh seems a rather high value to put on your own generation - especially if that's your off-peak rate.

10-20p/kWh would be more normal.