Considering a Tesla Powerwall

thommcg

Anyone any experience with these? Intended use would be charging during night-rate metering; discharging thereafter - outdoor install. Prior billing suggests <20 units of electricity daily (and so I'd presume a full charge / discharge occuring). Got an EV last year, which requires a similar amount each day in addition to that (hence the switch to a night-rate meter).
Adding solar to the mix is a possibility, though dependent on other work so disregarding that in the short-term.

KCross

It will work but how many years for payback? Did you run the numbers?

Aren't they like €6k to buy? You'll burn a lot of electricity before it pays for itself.

thommcg

KCross wrote: »

It will work but how many years for payback? Did you run the numbers?

Aren't they like €6k to buy? You'll burn a lot of electricity before it pays for itself.

Looks like €70+ per billing period, so 10-15 years of I calculated right... at current day-time rates anyway.

unkel

You use 20kWh during peak hours? Without charging your EV? That's an awful lot, more than twice the national average for 24/7 usage. Are you sure?

If you are, your sums are fine. You'd save 16c minus 7c per unit of nightrate that you store in the Powerwall at night and consume during the day. That's 7c times 20 units times 365 days, so about €650 per year. Payback a bit over 10 years for the Powerwall.

air

Surely a PV system would have a much better ROI assuming you have the space for it?
Will the powerwall even work like this out of the box?
I would have thought it would require an external charger at least if you have no PV input.

murphaph

Don't think a powerwall sill work in this configuration at all, certainly not out of the box as it needs some interface external to the battery itself.

It's designed for DC-DC (high voltage) coupling. The idea is the PV can more or less send its high voltage DC straight to the battery (hence why only 2 inverters that I know of are certified for use with the Powerwall, the Fronius Symo Hybrids and the Solaredge units with the extra interface unit).

Why a Powerwall?

There's more cost effective batteries that are compatible with off the shelf equipment on the market.

rolion

@Sir liam a lot

What about a standard 2000w or 2500W APC SmartUPS !?
Setup in fully charge / floating mode at day time and use it ONLY for lighting at night time !? (assuming that the fuse board panel will be modified at the fuse circuit level )
Set in pass-trough / true-online mode,when batteries goes under a percentage disconnect and /or reconnect back to grid.

They're not very efficient, have a very high self-consumption and their low voltage disconnect is too low. The UPS will probably use more power than the lights.

Also arguably not worth the investment for a negligible load.
A 400VA inverter with sleep mode, would be ample for most lighting requirements and have a lower self-consumption.

rolion

I am seriously considering a battery system for my PV system.
The amount of extra/additional electricity generated looks like a lost to me.

So,to get it right:
Battery charger / controller will have the input from PVs.
X Battery bank will be kept charged and / or in float by PVs and c/ller.

24/48V output of the batteries will be connected in to an inverter,24/48V DC "lifted" up to 220V AC.
That output of the inverter will be connected ... where !??

Most of the ABB inverters needs 90-120 start-up voltage.
Then, 2 strings of 8+8 panels,giving a 240V DC will exceed any of the setup by Midnight and Outback battery chargers.
Irish grid accepts mostly ABB devices.

Tough...whats the RoI and TCO ?


LE

Becasue is FRIDAY:

rolion

Found LG Chem.
80% capacity retention over 10years !?
Price,around £4,500

air

Look at the GroWatt units, they sit between the battery and any existing inverter so there's no change in terms of your grid interface. They boost the battery voltage up and maintain a high voltage DC input to your inverter during the night.

Outback and Midnight are mediocre controllers.

High voltage is >30kV

<1kVAC / 1.5kVDC is within the realms of low voltage.

air

By high voltage I was referring in relative terms to PV string voltage (generally 100-550V or so), merely to differentiate from the battery voltage which is 48V in the case of the GroWatt units.

murphaph

I figured as much air.

murphaph wrote: »

It's designed for DC-DC (high voltage) coupling.

rolion

Powervault 4kwh LithiumIon.
More info on the solution HERE.

I have put my wallet on a similar with this one HERE.
Trouble is that not compatible with Irish grid... so forget it.
Also, issue with "approved installer" only in UK I guess.

Reviews :

General "how-to" PV storage
https://www.renewableenergyhub.co.uk/solar-panels/batteries-for-solar-panels.html

The Guardian:
https://www.theguardian.com/business/2015/jul/05/smaller-batteries-more-power-uk-solar-households-innovators

SolarPowerPortal
http://www.solarpowerportal.co.uk/news/powervault_targets_uk_lead_in_energy_storage_with_700000_investment_7818

TechWorld
http://www.techworld.com/startups/how-powervaults-smart-home-battery-is-transforming-energy-storage-3655494/

TheTelegraph
http://www.telegraph.co.uk/finance/personalfinance/energy-bills/11567977/Can-a-2500-solar-box-power-your-house-at-night.html