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Author Topic: My PowerVault - small milestone  (Read 3546 times)
RIT
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« Reply #30 on: September 22, 2017, 05:43:57 PM »

I am having issues with domestic batts and i have come to the conclusion that they can only work if we have time of use tariffs otherwise,

Once one has used the self generated leccy then it cannot be used twice obviously.  So when the load is greater than supply then batts have no function. This naturally occurs in winter but can occur at other times if you increase the loads.
So if all one is doing is charging a batt instead of supplying one of these loads then nothing is achieved in fact worse with the batt losses.

So if we have enough load there is nothing for batts to do and so we need to use the loads sequentially and have enough of them.

The cost of the batts installed and replaced every x yrs make it very questionable.

The losses of the batts 20% ?  means that one is no worse off energy wise than if they had not bothered to capture that 20%  

Due to charge and discharge rates of the batts means that significant amounts of leccy must get exported to the grid and high demand loads cannot be supplied without the grid.

This is like off grid living whilst connected to the grid and that does not work either in my opinion.

I just dont get it.

Ken

A future possible question as and when time of use tariffs become mainstream is going to be why install the PV. In all likelihood, things like the PowerWall will drop quite a bit over the next few years and if we see time of use tariffs with over night rates down at 4p per kWh it may make more sense to just install a battery that charges itself up overnight and discharges during the high cost hours.

If FiTs ever gets withdrawn there maybe little value in installing any PV+battery solution.
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2.4kW PV system, output can be seen at  - https://pvoutput.org/list.jsp?userid=49083

Why bother? - well, there is no planet B
dan_b
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« Reply #31 on: December 09, 2017, 02:11:23 PM »

Today marks exactly a year since my PowerVault experiment began.
In those 12 months, it's discharged 867kWh back into my house.
Best month was June, where I did 103.94kWh
Worst month was January, where it did just 30kWh.

So far it's been charged purely by spare SolarPV, which is obviously biased to the sunny months where I'm still generating more than I can use in the house or in the battery. In the darker months, there's often barely been enough SolarPV to cover house demand let alone charge the battery (last December it went 5 days with 0 discharge), and those of course are the months where my demand is going to be highest due to long dark nights.

So, I've decided to try switching to an Economy7-type tariff in order to re-charge the battery at night on low-rate juice and feed that back into the house during the daytime to see if that makes any difference to my electricity bills.  It will make the battery work harder during the winter months at least.

The one I'm going with is with Tonik Energy - they're running a trial with people with batteries to test smart meters and time-of-use tariffs, but to start with it's just a straightforward E7-type package.

Let's see how it goes!
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3.06kWp SolarEdge system with a split array:
2.18kWp 10x South facing, plus 4x West facing 880W

Mk1 ImmerSUN DHW diverter
4kW PowerVault Battery
morrisok
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« Reply #32 on: January 11, 2018, 01:17:29 PM »

Hi Dan,

I would do the maths before switching to Economy 7.  With a 4KW battery unless you are a very low use house you will probably pay more during the day than you will save with the 4KW you buy cheaply over night.  If you had a 10KW or 20KW system I imagine it would make a lot more economic sense to be on Economy 7.
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« Reply #33 on: January 11, 2018, 04:39:05 PM »

dan_b,

I've just run my figures through Tonik and they are, at best, 113 a year more expensive than Bulb (who I'm currently with).

At 35% night time usage Economy 7 still makes sense for us but whenever I do comparisons I still run a check on quotes with and without Economy 7.

It will be interesting to hear how you go with the smart meter and TOU tariffs.

Regards

Richard
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16off BP380 on a Lorentz tracker/ SMA SB2500, 16off Chinese 80W/ SMA SB1700, 16off BP380/ SMA SB2500. CTC GSi12 heat pump/ Gledhill ASL0085 300litre EHS/ 3off Navitron 4720AL solar ET panels and an Immersun T1060/ T1070/ T1090 (+ planned 7off 235W panels).
marshman
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« Reply #34 on: January 11, 2018, 05:39:48 PM »


At 35% night time usage Economy 7 still makes sense for us but whenever I do comparisons I still run a check on quotes with and without Economy 7.


Agree with Richard there. You need to get quotes for both with and without E7. The comparison sites will not do it for you. I found this out a couple of years ago when I did a search on several sites , ticking the E7 box. Then did another without E7.  Without E7 it was about 10% cheaper.  This year it is the other way round as I have changed our usage pattern.

Roger
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3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
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« Reply #35 on: January 11, 2018, 10:30:00 PM »

Ok well I've done it now anyway - got my smart meters fitted 2 days ago and they've put me on their trial tariff which is the following

daytime - 14.4p /kWh
Midnight - 7am - 8.8p /kWh

So last night for the first time, the battery charged up overnight from the grid giving me a full battery at 7am this morning.  Combination of battery discharge and a tiny tiny bit of solar generation around noon meant I didn't import anything until 4.25pm.

I also ran the dishwasher at 1am last night rather than during the day, and will run the washing machine tonight at 1am as well.

At this time of year my solar production is really poor anyway (today was just 401Wh, the day before was 122Wh!) so the battery would be going days without getting any charge at all - so that's kind of money wasted as far as that's concerned.  I thought it was worth trying this as at least I'll get more use from the PowerVault if nothing else!

I'm happy to still be treating this as all as a bit of an experiment.  Year 1 was just to see what the battery did and the impact it had with the solarPV in place- which was 865kWh of battery discharge (ie avoided import), and a drop in the work the ImmerSUN does by about 300kWh  (in 2017 the ImmerSUN took 369kWh vs 630kWh in 2016).

So year two is to see if I can make the battery work a bit harder for me - particularly in the months of Jan-Mar, and Oct-Dec where battery diversion was low (e.g. Jan 2016 was just 30kWh, so 1kWh/day average, vs June 2016 which was 103kWh, 3.3kWh average).

I imagine what I might have to do is reduce or stop the E7 charging from between June-Sept as in those months I'll be generating, and therefore storing, plenty of solarPV, so no point paying to import and fill up the battery first!

Let's find out though  angel




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3.06kWp SolarEdge system with a split array:
2.18kWp 10x South facing, plus 4x West facing 880W

Mk1 ImmerSUN DHW diverter
4kW PowerVault Battery
TheFairway
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« Reply #36 on: January 12, 2018, 09:24:09 AM »

Whats the standing charge on that tarrif?

I almost went for a Smart meter recently but as it was SMET 1 I declined. Apparently SMET 2 meters should be available latter part of this year. I was only after them to fit an isolation switch which would have been free if I had Smart meter fitted at the time. As im not paying for the isolation switch anyway, it wasn't a big thing to sway me.

My thinking is whats the point of a Smart meter now if its not so smart if/when I change supplier.

My supplier (Octopus Energy) said that there was no penalty for taking the "smart" meter but they do plan on introducing various tarrifs like Electric Car friendly ones - not sure how different that would be to E7/10.

For anyone in the know, is there an automated way of knowing what Tarrif a "smart" meter is on? ie does it publicise its tarrif on network - even better, can you know what the up coming tarrifs are? Im not talking about looking it up on a website, im talking about automated triggering devices to charge/switch on/off etc based on the tarrif.
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3.995kWp SE PV. 5kW Burley Hollywell woodburner. Vent-Axia Sentinel Kinetic Plus MVHR

All posts are my own personal thoughts and opinions and do not represent those of my employer, clients or partners.

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