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  • FIRST POST
    • Martyn1981
    • By Martyn1981 5th Dec 16, 3:57 PM
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    Martyn1981
    On-grid domestic battery storage
    • #1
    • 5th Dec 16, 3:57 PM
    On-grid domestic battery storage 5th Dec 16 at 3:57 PM
    Hello!

    Right, as discussed elsewhere, battery storage for self generation (typically PV) is interesting (to some), and gathering momentum in the UK. So here's a thread to discuss it, and watch it develop.

    I've called it on-grid, as off-grid is so much more specialised. And domestic as commercial scale storage, or grid scale can be chatted about on the Green & Ethical energy issues thread.

    So, where are, well this article lists about 20 systems that are available or should be available soon:-

    Introducing CleanTechnica’s New Home Battery Overview Page

    Jumping straight in with personal opinions:-

    Economical - Not yet. Prices are falling fast, the range of products is expanding fast, and large numbers are being deployed in some countries, either because the price of leccy is high (Australia & Hawaii) or because subsidy schemes exist (Sweden & Germany).

    Where are we today. My needs are a 4kWh system. That's 4kWh of useable capacity, which would mean about 8kWh of lead acid (LA), or about 5kWh of lithium ion (Li-ion). My research has found batts in the high £2k and up range. I need the price to be nearer to £1.5k.

    The Tesla Powerwall II, installed is approx £6.5k, which works out at about £2.2k for 5kWh, but of course, it doesn't work quite like that, as smaller systems will cost proportionately more.

    Environmental - Tricky one this (to say the least). Until storage is needed, it's not environmental. Renewable energy (RE) generation currently displaces gas generation, which is a demand follower. Once gas generation is pushed down to zero (at times) we need storage, but we aren't there yet.

    However, to push gas generation down to zero, we need more RE, and to ensure it is viable/economic/profitable, we will need storage - chicken and egg situation.

    The advantage of storage to the environment, is to take peaks of RE and timeshift them to peaks in electricity demand. On a domestic level, this works quite well as PV generates during the day into the afternoon (or evening) depending on the month, so any stored leccy is available for the evening peak 5pm to 7pm.

    That's the background, and now here's a thread to discuss options, prices, economics, and watch things unfold. Enjoy.
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
Page 3
    • Martyn1981
    • By Martyn1981 13th Feb 17, 5:00 PM
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    Martyn1981
    It is of course quite true that in the - very rare - circumstances where a Li-ion battery does catch fire the result is extremely nasty. But let's not take it out of proportion : are there similar proposals to ban highly volatile liquid fuels (e.g. petrol of course) or vehicles containing them from being stored within a garage ?
    Originally posted by EricMears
    Actually you've mentioned, what I forgot too. Could this proposal grow to exclude EV's from being garaged?

    Perhaps modern technology could come to the rescue, and your car rings you with a 'booty call' - "I'm feeling really hot, get here quick".
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • Alan_Brown
    • By Alan_Brown 14th Feb 17, 11:04 AM
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    Alan_Brown
    I've just been skimming the thread and saw a few posts about the tidal lagoons and energy storage. I'm not sure about using batteries for storage (their ecological impact and short life-cycle puts me off) but I can see a use for compressed air energy storage.

    As these lagoons are obviously on the coast, large bags can be fixed to the sea bed and filled with compressed air using excess energy from the barrage. When the energy is required, the air is released to drive turbines and generate electricity. This technology is used in Germany, where they use former salt caverns for the compressed air. However, there is an issue with pressure loss as the caverns empty. With bags under the sea, the weight of the sea on top will keep the pressure constant, right up until the bag is completely empty of air.
    • zeupater
    • By zeupater 14th Feb 17, 3:00 PM
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    zeupater
    I've just been skimming the thread and saw a few posts about the tidal lagoons and energy storage. I'm not sure about using batteries for storage (their ecological impact and short life-cycle puts me off) but I can see a use for compressed air energy storage.

    As these lagoons are obviously on the coast, large bags can be fixed to the sea bed and filled with compressed air using excess energy from the barrage. When the energy is required, the air is released to drive turbines and generate electricity. This technology is used in Germany, where they use former salt caverns for the compressed air. However, there is an issue with pressure loss as the caverns empty. With bags under the sea, the weight of the sea on top will keep the pressure constant, right up until the bag is completely empty of air.
    Originally posted by Alan_Brown
    Hi

    The issue you'd come across is the necessary water depth ... the seas around the UK are mainly very shallow and to get anywhere near the level of compression mentioned for the schemes/technology used above you'd need around ~2000 feet of water, which is only available as the continental shelf starts to slope away to the west of the UK, so normally somewhere between 100-300miles from the coast depending on location .... possibly not the best place to site compressors and turbines or run HV cables to ....

    HTH
    Z
    Last edited by zeupater; 14-02-2017 at 3:05 PM.
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    • Martyn1981
    • By Martyn1981 14th Feb 17, 5:32 PM
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    Martyn1981
    For coastal and inland areas I think LAES rather than CAES is probably best, like the Highview scheme in Slough, which can be scaled up to 200MW/1,200MWh plants.

    But, lagoons can provide some balancing/storage for a brief time, as they can be emptied slightly early or late to better match peaks, though this will reduce the maximum amount of energy in that cycle. Basically, they supply leccy for 3.5hrs on each in tide and out tide, so 14hrs per day, and you wait for the optimum time (and head of water differential) to let the water flow from one side to the other, but this can be varied as mentioned.

    I've also wondered if they themselves could be used for pumped storage during the brief window when the lagoon is full and the tide is high. At that point you are pumping in at very low head, say from 5m tide outside, to 5m + 'a bit' inside. But that pumped water energy input of 'a bit of a metre' then 'magically' becomes 5 and a bit metres high when the tide goes out giving a multiplayer on the pumped energy.

    I suspect my idea is relatively stupid as the opportunity window is quite small, and the cost of the extra kit and complexity, not worth it ...... just a thought.
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • Martyn1981
    • By Martyn1981 14th Feb 17, 5:38 PM
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    Martyn1981
    This article is about EV's but is relevant in that it talks about the cost of battery cells falling faster than expected.

    As always my optimistic thoughts on batts (like PV) seem to be wrong, and I'm more than pleased.

    Electric Vehicle Battery Prices Are Falling Faster Than Expected
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • Martyn1981
    • By Martyn1981 15th Feb 17, 3:23 PM
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    Martyn1981
    Ffu 6
    I think this one is important, well it is to me:

    So yesterday was the first really good day in Feb with 7.6kWh of generation - and I managed to get 5.33kWh in and out of the battery as a result
    I'm really quite impressed - especially as it's nominally "only" 4kWh of battery capacity - just shows that it'll contribute during the day and if there's enough hours of generation, can still re-charge and catch up again for later on.
    I've provisionally estimated that I need 4kWh of useable storage based on:
    Summer months useage capped by average 2.5kWh import.
    Winter months useage capped by average 1-3kWh of export.
    Spring/Autumn months import less than export and around 4-5kWh.

    The issue here is that 5kWh is more than 4kWh, but I've always assumed that some of that import will be from variable weather and generation in those months, particularly from clouds, and that storage would allow for lots of small battery cycles as demand and supply vary through the day. My friends e-mail seems to confirm this, which helps guide me on the capacity of battery needed.


    Also, thought I'd add this thread on from Navitron, for anyone interested. It's far more complicated and I'd suggest reading nowty's autosig first to get an idea of what he's been up to, and where his experiments are taking him.

    Growatt SP2000 Storage System
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • Martyn1981
    • By Martyn1981 19th Feb 17, 3:46 PM
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    Martyn1981
    I found this interesting background reading, but otherwise not too important, except for this bit:

    The analysis assumes an average selling price of battery storage starting at $US250/KWh, deflating 5 per cent per year to $US150/KWh by 2027.
    -5% pa is very promising, and hopefully understated.

    Tesla & LG Chem Set To Dominate Massive US Battery Storage Market
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • Martyn1981
    • By Martyn1981 23rd Feb 17, 9:28 AM
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    Martyn1981
    Staggering savings from the first Powerwall in Australia after 1yr. This is the smaller 7kWh model, not the new 13.5kWh model.

    He also has a system that can sell battery leccy to the grid (at a premium) when demand is very high.

    Rather jealous!

    Living with the Tesla Powerwall for a year: the first Australian case study

    Powering the home with electricity in 2015 cost him $2289. But just over a year ago, he invested in a solar power system that has since significantly cut costs.

    Nick, a self-confessed Tesla fanboy, was the first person in Australia to buy the company's Powerwall. He bought a 7kW battery, a 5kWp solar array, a SolarEdge inverter and a Reposit monitoring system for $16,790 in January 2015.

    A year on and Nick's annual electricity bill has dropped to $178.71 – that's a 92% saving of $2110.
    "The aim is to try and export about three times of what I import because my electricity cost is about three times [as much]."

    The going rate is 8 cents per kilowatt-hour, but Nick installed a Reposit monitoring system – an $800 extra – that'll push the price up to $1 per kilowatt-hour at certain times.

    "So when we had that really hot weather last week, what happened is, there's a peak event on the network and [electricity companies] asked batteries to start dispatching power, so it's kind of like a little power station if you like."
    Obviously UK PV generation and seasonality mean we are unlikely to see such savings, but the better these systems do in Australia (and elsewhere) the faster they'll be deployed, and the faster we'll see prices drop. At least that's what I tell myself, with my fingers crossed!
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • Cardew
    • By Cardew 23rd Feb 17, 9:49 AM
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    Cardew
    Selling electricity back to to the grid at up to $1 per kWh helps the figures!!
    • Martyn1981
    • By Martyn1981 23rd Feb 17, 9:52 AM
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    Martyn1981
    Selling electricity back to to the grid at up to $1 per kWh helps the figures!!
    Originally posted by Cardew
    Absolutely and helps to bring down the wholesale price during these peak times. Perfect.
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • NigeWick
    • By NigeWick 23rd Feb 17, 9:55 AM
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    NigeWick
    Obviously UK PV generation and seasonality mean we are unlikely to see such savings, but the better these systems do in Australia (and elsewhere) the faster they'll be deployed, and the faster we'll see prices drop. At least that's what I tell myself, with my fingers crossed!
    Originally posted by Martyn1981
    I think it's just a matter of time before enough people get on at the government and they start favouring renewables with storage and ditching fossil and nuclear.

    I have started e-mailing (bombarding) my MP with renewables and EV stuff. John Hayes MP is Minister at the Department of Transport. Before the election he was canvassing in my road. He looked tired so I dragged him in for a single malt and put the world to rights for half an hour. In private he's actually quite sensible and he does work hard for his constituency (well his researchers do).
    The mind of the bigot is like the pupil of the eye; the more light you pour upon it, the more it will contract.
    Oliver Wendell Holmes
    • Martyn1981
    • By Martyn1981 2nd Mar 17, 12:19 PM
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    Martyn1981
    Ffu 7
    Latest battery news. Immersun yet to wake up, but monthly stored leccy growing with generation. Note the small warning on data.

    Firstly - these data now come with a health warning - February has seen a few outages in the PowerVault data portal, and in exploring that, the tech guys have also noticed some inconsistencies in the data that has been logged to date, so I'm not 100% confident of the numbers in terms of kWh "saved" - they could be too high, or too low, so we'll just have to take it as it is for now.

    Anyway - Feb

    Imported 210kWh
    Generated 83.43kWh (2nd worst Feb since install!!)
    Battery discharge - (warning!) - 53kWh
    ImmerSUN diversion - 3kWh (in Feb 2016 this was 22kWh - so the greedy battery has stolen all of that!)

    So, the Battery has probably saved at least £7 this month in imported electricity avoided, quite a gain over January (if true!).

    Either way, gotta love batteries!
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • shavy65
    • By shavy65 2nd Mar 17, 1:06 PM
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    shavy65
    [QUOTE=Imported 210kWh
    Generated 83.43kWh (2nd worst Feb since install!!)
    Battery discharge - (warning!) - 53kWh
    ImmerSUN diversion - 3kWh (in Feb 2016 this was 22kWh - so the greedy battery has stolen all of that!)[/QUOTE]

    Would you happen to know his Import figure for Feb 2016? The comparison between 16`/17` may be of interest.

    Cheers.
    3.975 kWp System, South facing, 21 degree pitch, 15 x Canadian Solar Elps, Samil Inverter, location NE Scotland (Fraserburgh) Bring on the Sun
    • Martyn1981
    • By Martyn1981 2nd Mar 17, 6:39 PM
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    Martyn1981
    Would you happen to know his Import figure for Feb 2016? The comparison between 16`/17` may be of interest.

    Cheers.
    Originally posted by shavy65
    Hiya Shavy. It was 220kWh in Feb 2016, so he said:-

    Imported 220kWh. Difficult to compare directly of course - but with less generation (Generated 119kWh in Feb 2016 vs 83kWh this Feb), we imported 10kWh less juice.
    Too tight I suppose to draw any conclusions, but appears(?) to be going in the right direction, especially given the big generation difference.

    I suspect March will start to show significant differences, and see more action from the Immersun too.

    Edit: Actually, perhaps we can draw some conclusions. Assuming the batts had spare capacity, which seems reasonable looking at the months generation, then had the PV generated that 'missing' 36kWh, the batts probably would have caught most of it, leading to a 40kWh reduction, which would have been about a 20% reduction. Gut feeling is that 20% is significant enough to call successful and unlikely to be a normal fluctuation. But I'm showing impatience, Mch onwards will be more clear I'm sure. M.
    Last edited by Martyn1981; 02-03-2017 at 6:47 PM. Reason: Added an edit
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • Alan_Brown
    • By Alan_Brown 10th Mar 17, 7:07 PM
    • 172 Posts
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    Alan_Brown
    I'm interested in the idea of going off grid during the summer months (June, July, august) by adding a further 3 kw to our existing 4kw of solar and obviously a battery array. I just can't see how you calculate how big the batteries should be for the size of solar you have installed. I saw that Mart mentioned 5kw of storage for his 4kw array and wondered how he arrived at that figure?
    • Martyn1981
    • By Martyn1981 10th Mar 17, 8:13 PM
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    Martyn1981
    I'm interested in the idea of going off grid during the summer months (June, July, august) by adding a further 3 kw to our existing 4kw of solar and obviously a battery array. I just can't see how you calculate how big the batteries should be for the size of solar you have installed. I saw that Mart mentioned 5kw of storage for his 4kw array and wondered how he arrived at that figure?
    Originally posted by Alan_Brown
    Hello Alan. If you have a look at an earlier post you'll find some of the information:

    Hiya.
    Originally posted by Martyn1981
    But basically, you need to think through your import and available export for the year. I broke mine down into summer, winter and spring/autumn. Then looked for where the limit is.

    Summer was import limited.
    Winter was export limited.
    Spring/Autumn was 'goldilocks' with import covered by export.

    So that gave me an economical on-drid battery figure of 4kWh useable.

    Lots of important caveats in that last paragraph. That's not off-grid, that's the sensible amount of storage based on the ability to use grid leccy at any time, so simply not rational to build in any additional capacity, due to diminishing returns as you go bigger.

    Have a think and a play, and then chat, as those figures for myself, are just a working theory. Also note FFU 6 post #46 which explains how 4kWh of useable storage, can supply 5kWh of leccy across the day (micro cycles of charge and discharge, particularly during cloudy weather).

    What do you think?
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • Martyn1981
    • By Martyn1981 13th Mar 17, 10:11 PM
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    Martyn1981
    Over 50,000 solar storage systems are now installed in Germany

    The increase in new installations was mainly due to a 40% drop in prices over the past three years. German solar association Bundesverbands Solarwirtschaft expects their number will double to 100,000 in 2018.
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
    • nobby1963
    • By nobby1963 14th Mar 17, 9:36 AM
    • 281 Posts
    • 332 Thanks
    nobby1963
    Morning all,
    Just noticed an email from EDF this morning....


    Sunplug - get smarter with solar storage

    Install the latest li-ion home battery for £3,999 (inc VAT) and start saving on your energy bills.

    Haven't got time to digest it at the moment but seems to be promoting a new LG battery storage system.

    Cheers
    Nobby.
    SMA 4000TL Inverter, 17 REC 235PE Panels, South facing, roof angle \ `ish, 3995 watt system.Installed Nov 2011.
    • Exiled Tyke
    • By Exiled Tyke 14th Mar 17, 1:22 PM
    • 199 Posts
    • 757 Thanks
    Exiled Tyke
    Morning all,
    Just noticed an email from EDF this morning....


    Sunplug - get smarter with solar storage

    Install the latest li-ion home battery for £3,999 (inc VAT) and start saving on your energy bills.

    Haven't got time to digest it at the moment but seems to be promoting a new LG battery storage system.

    Cheers
    Nobby.
    Originally posted by nobby1963
    The price appears to be for a 3.3Kwh battery (which can discharge at 2.5Kw) together with an inverter (does this make is less efficient than systems which link into the existing inverter Marty?). Unfortunately I cannot find anything else out about the battery itself - crucially expected cycles. Still it looks like a step in the right direction.
    Install 28th Nov 15, 3.3kW, (11x300LG), SolarEdge, SW. W Yorks.
    • Martyn1981
    • By Martyn1981 14th Mar 17, 4:29 PM
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    • 9,156 Thanks
    Martyn1981
    The price appears to be for a 3.3Kwh battery (which can discharge at 2.5Kw) together with an inverter (does this make is less efficient than systems which link into the existing inverter Marty?). Unfortunately I cannot find anything else out about the battery itself - crucially expected cycles. Still it looks like a step in the right direction.
    Originally posted by Exiled Tyke
    I did try to register an interest (as I'm an EDF customer) but failed to pass the 'can you enter your details correctly' stage, as they didn't like my phone number. I'm 'showing an interest' in most offerings just in case a DNO trial pops up, though I'm not holding my breath as WPD (my DNO) are concentrating on commercial trials. Doh! Just realised I probably shouldn't have left a space ..... but I digress.

    Yep, noticed that they replace the inverter. So, here are the issues. To add a battery directly to the PV/inverter, the inverter needs to be battery friendly, some these days are, so folk can plan ahead for a retro-fit.

    This is what's known as a DC system, as the inverter directs excess generation directly to the batts from the PV, so no inverter losses. It only changes it from DC to AC when you need it / discharge it.

    A battery system that's not linked to the PV, is known as an AC system, as it takes the excess after the inverter has changed it from DC to AC (with losses), then changes it back to DC (losses), and stores it till you need it, then changes it back (losses).

    The Tesla PowerWall II DC model is rated at 92% efficient, whereas the DC model is 'only' rated at 89%. [Edit: Tesla are dropping the DC model from their Aussie launch as the market seems more interested in retro-fit, plus the AC model has a built in inverter so makes a nice package, M.]

    But an AC system gives you more choice and importantly for early FiTers, means all losses are after the TGM, not before. EG, a 90% efficient DC system that redirects 11kWh, then discharges 10kWh, will 'cost' you 1kWh at the TGM. Not significant for the latest installs, but worth considering for higher FiT rates as you'll be losing about 100kWh for every 1,000kWh that goes through the battery.

    The battery is the LG Chem model, and you can find some info in the CleanTechnica list (post #1) or in their comparison they now do, here look for the RESU model.

    Here's a shop link, but not a recommendation, just for ideas on prices and spec sheets.

    Frustrating to see these prices when Elon's offering Australia batts at $250/kWh ..... before packs, inverters, install etc etc, but still!
    Last edited by Martyn1981; 14-03-2017 at 4:33 PM. Reason: Added an edit
    Just 'call me Mart'. Cardiff. 5.58 kWp PV systems (2.4 ESE & 1.18 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
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