Behind-the-meter solar storage

[DamonHD]

I'm not especially interested in financial aspects of this (I know that it'll never pay back in any straightforward sense) - just to see and share how well or otherwise it works technically.

The issue is: is the load (ie grid flow) shifting by 4x batteries significantly better than 2x or 1x batteries, especially compared to the increased vampire load of those extra betteries in mid-winter when energy is scarece?

Rgds

Damon

[MattM]

I was thinking more or less for general metrics.  I'd think investment cost and recurring cost schedules would be a good indicator of feasibility.  Also having enough storage on hand for the worst possible times for the grid to go down would be plausible justifications for any cost above grid tied homes.

I'd much rather see solar on homes than diesel backups.  But diesel have on  demand functionality in most cases.  Solar is use it or lose it.

[DamonHD]

My grid-tied storage won't work if the grid is down, and mid-winter when we'd need it most we only generate enough to cover about 25% of our electricity consumption.  And that's ignoring heat.  But the grid has only been down here for a couple of half-hour chunks in a couple of decades...

(The off-grid would give us a bit of lighting for days if we wanted it.)

I should sit down and do the analysis that you bring up, eg the last battery bank lasted 10 years, so what was the yearly cost in storage alone of the 'free' electricity that it stored?  I have the numbers.

A related point came up here:

https://twitter.com/Zapaman/status/1455297527364964363

Rgds

Damon

[MattM]

I was assuming your deficit was midsummer, but you make a lot more sense with that answer.

[Scruff]

I'm interested in an impartial appraisal of such a system's net return.

I think I might be biased, or cynical, or honest...not sure which?...a second opinion would be great. Please don't csv data...I prefer pictures. I can't make sense of spreadsheets.

I've my LFP 2.5kWh hybrid in hibernation now until April/May because it's not worth the liability, quiescent and round trip inefficiency.
Spendy yolk that was.




I managed a humble 13.5kWh to the diverter over the last week. Clearly, I have no surplus to worry about from a 5kW array.

What I like about my hybrid is it's honest about it's quiescent.



Most aren't. They just report their output to look more innocent.
My SB1700 turns off when it can't meet it's quiescent.
My ApprenticeVolt Saladin uses 30W but says it's generating 1W when it manages -29W.

Enter the beauty of BS detector meters. Third party with traceablity to My Fluke 87V.

 

These are great at detecting fibbers and solar freakin' battery heaters bro....

[DamonHD]

So it turns out that my PV inverters for my ~5kWp only absorb a couple of watts when it is actually dark, but in twilight can use 10x that.  So there are odd things like that that pop out of the woodwork.

The Enphase batteries?  I need to watch a bit longer, but I think I'm getting 8W to 10W quiescent when empty across all 4, so maybe 250Wh/day for the 5kWh/1kW.  (That's not including the Envoy controller, but I haven't seen evidence of that being more than say 2W.)

Rgds

Damon

[Scruff]

I'm running 79% RTE on that machine at ideal load.



C1 100%-0%-100%. That's pretty excellent. Every other system I have is 60%.

C1 discharge, C10 Charge + standby the way it normally functionally operates comes with a 24hr quiescent instead of one so the RTE is effectively 71% for the application of daily injection offset.

Then there's the minimum spill to grid threshold. I'd say the diverter spills 50W before firing. The hybrid ~100W before charging (goes to diverter anyways in my setup). That's about 8 outtov 18 panels feeding the system losses all told...

[DamonHD]

Updated page for the last round of Enphase storage install, including the modified load profile:

https://www.earth.org.uk/Enphase-AC-Battery-3-4.html

Rgds

Damon

[DamonHD]

Hi,

I have a rather grander immersion heater now wired in: my Sunamp Thermino heat battery finally went in yesterday after years of talk and then a couple more of pandemic delay!

https://www.earth.org.uk/note-on-solar-DHW-for-16WW-UniQ-and-PV-diversion.html#2022-03-09

https://www.earth.org.uk/_heat-battery-target.html

I'll be adding some installation pics this evening, but for those of you who like data, an interesting feature is that with diversion, some of the consumption and import flows will now be directly controlled, eg the boost mode limits how much is pulled from the grid whatever other loads (and PV generation) there are.

Rgds

Damon

[Mary B]

Nice but YIKES that price!

[DamonHD]

Just in case this is of interest: trying to pick the best fixed export (spill-to-grid) margin for my solar PV diversion to a heat battery:

https://www.earth.org.uk/eddi-diverter-export-margin-analysis.html

Rgds

Damon