where next for me with energy storage and extra generation

[SafetyThird]

Hi all, this post might end up being a bit of a long one, so you might want to grab yourself a tasty beverage of choice.

Previously, on Jay moves to the countryside and starts a new life......

Over the past eight years we've renovated our old stone farmhouse and opened a glamping site. It's gone from being a cold damp house to warm-ish and dry, free of draughts and much more comfortable home. in 2015 we put 6kw of solar on the south facing roof along with a 300l thermal store with 2 immersions fed from an Immersun which was later replaced with an Eddi. A Dunsley Yorkshire boiler stove was also connected to the store and so our hot water was 100% free from those two sources.

Heating was provided by the Yorkshire stove along with a Woodwarm double sided stove between the other two downstairs rooms so again, that was free heating as I'm slowly returning 7 acres of old woodland to a more managed and healthy environment and have a large 3 bay wood store. The house originally had 7 storage heaters and, as the renovation progressed, we removed all bar two of them. They cost a great deal to run, even on economy 7 tariff. We work from home full time so having the fires became part of the life style but we didn't expect to stay here into retirement age originally.

As we've decided we're now staying here for the longer term, probably the next 20 years or so, we wanted to have proper central heating as, being an old stone cottage, it does get cold when there's no heating running and, when you get to mid afternoon and realise it's getting chilly, it takes a while to warm up. As we're not on the gas grid and certainly didn't want oil, we were left with heat pump options and, as we're on a little farm, we had ground source installed last autumn.

1000m of pipe went under the field behind the house and a Clausius heat pump. Sadly, the old system that had served us so well had to go as you can't get RHI if a wood stove is connected (unless you want to me metered which would mean less payback). So new hot water tank and radiators all round the house. Despite a few teething issues, it works brilliantly. I've put Tado TRV valves on all the radiators that aren't left open and we can control it all from our phones with each room individually set. Waking up to a warm house is fabulous. All in, the cost was about £41k and we'll get £32k back over the next 7 years, once the RHI payment is approved. This is why we did it now as RHI ends this month and we couldn't really afford it without knowing we had the payback option.

I've just done the figures for the first quarter compared to the same period last year.

In Q1 2021 we used 4650kwh of electricity at a total cost of £840
In Q1 2022 we used 4800kwh of electricity at a total cost of £1211

Our electricity cost went up 62% from Nov 1st. So, we're basically using the same amount of power but have a warm, centrally heated house which is exactly what I was hoping for. However, we've gone from using most of the power at night to most of it during the daytime, which also has cost implications.

The heat pump, according to it's built in monitoring, is using 9kwh/day, 520kwh/month. I'm assuming that's an average over the 5 months it's been running.

Our total energy import last year was 11,668kwh at a cost of £2109. Our solar panels generated 5800kwh, which is bang on what was expected and is doing that year in, year out.

We're also looking to replace one of the two vehicles with an electric car sometime this year, hopefully.

So, now I'm looking at the future and wondering where to go next. I'd like to generate more of our own power and find more efficient ways to store/use it so we're less reliant on grid import as that cost is only going to keep going up and, after the last few months, I think it's worth looking for alternatives to grid supply. Now, I'm not looking at going completely off grid, just to reduce my reliance on it and the cost implications going forward.

We're inverter limited to 3.8kw export by Western Power and, when our poles, cables and transformer had to be replaced by Western Power because of their age, we paid £2k to have the system upgraded from a 16kva supply to twin phase 50kva for some additional future proofing and moved the supply cable underground from the transformer. One phase runs the house and the other phase feeds out to the barns and the glamping site infrastructure.

The first seemingly obvious choice would be to invest in battery storage so that I can use more of the daytime generation into the evening. As we have the heat pump, we use less diverted energy as we generally have a tank full of hot water because the heat pump is running and that makes best use of the electricity as the heat pump has a COP of around . I've not followed battery technology, except for the occasional look at Tesla prices so that's first on the list. Though I'm not sure how cost effective battery storage is currently, I think it will become more cost effective as electricity prices continue to rise.

I can't add more solar for grid connection but I'm wondering about throwing more panels onto the barn roof and using them to charge additional battery storage to feed into the house. Not sure if that's something that can be done easily as the barn is on a separate phase to the house although the cable does feed up from the house to the barn. This is the second thing to investigate as I've seen insurance-replaced solar farm panels on sale occasionally and 10kw of panels would cost about £2500 plus install/fittings etc.

As we work from home and my wife has, due to changed brought about by the pandemic, returned to working full time, we need to ensure that the office continues to be functional. Currently all our computer/network/internet equipment is covered by small UPS units so that occasional short glitches don't throw everything out. We have a small Honda generator that we can hook up to those things easily enough with an extension lead for when work is done on the line elsewhere and we're without power for several hours at a time, this happens occasionally each year. I'm wondering about being able to have the battery system provide power to the house when the grid power it out but that's not the highest priority and I understand it requires different equipment.

Ok, so if you've made it this far, congratulations. What I'd love to hear is any suggestions for going forward or equipment/options to explore as I've not really been taking much notice of advances in this sort of equipment in the past few years and would appreciate any pointers from anyone who's more familiar with it so I can direct my research. Also, am I on the right lines or is it financially unreasonable for what I'm considering.

Many thanks.

[Countrypaul]

Couple of early comments:

You say you are grid limited to 3.68kW power export, that should be for each phase so could be twice the amount you have now if you put some PV on the barn.

I have been looking at batteries and associated hardware, PV, Inverters etc. If you have a battery, say 4 pylontechs 9.6kWh, and a hybrid inverter such as a ME3000SP this shoud be able to charge the batteries from PV, or mains (eg. set to charge overnight on cheaper electricity), also as it is (G99 or G100 - need to check) it shoud be able to put upto 3kW into your house from the batteries when you are importing power. I believe you could have more than one ME3000SP, but obviously there are other such inverters to choose from if you want more power (and can afford more batteries).
The ME3000SP also has an output for non-grid tied power so could provide for your IT systems during mains outage times, and if the sun was shining then without depleting the batteries.

There are many options, but if you can put up PV panels on the barn, and install some batteries you have plenty of flexibility.

You need to run some calculations, probably based on monthly figures as you may not need that much power in summer and won't have enough in winter from just PV.

[nowty]

Countrypaul, whilst I generally agree with your post, the Sofar ME3000SP is not a hybrid inverter, but an AC coupled battery inverter.

Hybrid inverters are capable of taking both PV and batteries and Sofar do have other models which are hybrid inverters.

[Countrypaul]

Countrypaul, whilst I generally agree with your post, the Sofar ME3000SP is not a hybrid inverter, but an AC coupled battery inverter.

Hybrid inverters are capable of taking both PV and batteries and Sofar do have other models which are hybrid inverters.

Whoops, should have read what I'd written properly, Nowty is entirely correct my mistake , the ME300SP would work with your existing setup - but if adding more PV you might want a hybrid inverter.

Since you have an Eddi, if you are adding an EV, the Zappi would be a good option.

[rogeriko]

Something like this. Many stores are selling them now. look around.

https://www.itstechnologies.shop/produc ... mlEALw_wcB

https://www.ginlong.com/rhi_inverter1/34629.html

https://midsummerwholesale.co.uk/buy/pylontech

You need 2 systems. One on each phase.

[SafetyThird]

Thanks every one for your replies. There appears to be a couple of favoured options with opportunities for upgrades.

1. The most obvious one is to get an AC charger and battery. This would just take excess generation from the PV and charge a battery pack and also give the option to charge from cheaper rate overnight grid power. I keep the same inverter (sunny boy) but I'm still limited to 3.8kw from my 6kw panels. I can always add extra batteries later. I could add a separate dc system with extra panels and inverter for battery charging later. No DNO dealings needed.

2. Hybrid inverter with battery pack. Replaces the current sunny boy inverter. If I bought a 6kw hybrid inverter, could I make better use of my panels for charging and would it still inverter limit my grid output. If I can, this looks to be a better option than 1 but this would need to be agreed with the DNO. If not, then I'd be back to a 3.8kw hybrid inverter and I don't see the advantage of replacing the inverter if it doesn't gain me anything in PV utilisation and I'm back to option 1 or is there an efficiency advantage in having a hybrid inverter rather than an AC inverter plus solar inverter? As with option 1, I can add additional batteries or DC system of batteries and panels later without dealing with further DNO setup.

Usage during power outage. Both of the above options allow me to have a separate circuit running if the power is out. My thoughts would be to simply move the house lighting circuits, which are all LED, and the house ring mains over to a separate small consumer unit and run those from the batteries.There's no large loads on the circuits regularly and they can be controlled manually during an outage. The electric stove and oven are on their own circuit and the heat pump is on it's own mini consumer unit.

The only concern is that several inverters only allow say 2.5-3kw max output from batteries. In that case, I couldn't use something like an iron which uses 3kw as the combined load with he rest of the house would be more than allowed to draw from the battery. Also, those circuits would be constantly draining the battery.

I guess the alternative then is to have The lighting circuits on the battery and a circuit with just say 4x13A sockets on the mudroom wall and, during an outage, run a couple of extension leads to the computers/servers and another round into the tv area. Doable and annoying but no less annoying than the current system of getting the little Honda generator from the barn and doing the same thing.

Batteries: Pylontech look great value for money and are well regarded but need racking. in our house they'd be in the mudroom and vertical wall mount would be preferable. My neighbour who's building a house next door is currently having a system installed which uses 6kw of panels and a 5.2 Givenergy batteriy and 3kw Givenergy hybrid inverter. A pair of those 5.2kwh batteries would fit neatly in the space below the current inverter even if a new battery inverter needed to be added.



For EV charging, I'd get a Zappi charger which would connect to, and be managed by, the Eddi diverter unit I already have.

I'll leave additional PV for another thread as that would require a 100m or so cable run from the barn down to the batteries in the house.

Changing tariff is separate thread to start as well.

[Countrypaul]

For your second option, I thought a G100 compliant inverter could limit grid export to 3.68kW and as such there should be no problem with the DNO. If you wanted to be able to export more than 3.68kW then I thought that DNO agreement was required. As such you could have an inverter that can produce 6kW but would only allow upto 3.68kW to be exported, so you could run 4kW of internal load plus export 2kW. One problem you might have is that if you switch inverter to a hybrid one with batteries, the total generation meter might start to record higher levels of generation as when the PV produces over 3.68kW you could still make use of it internally (or to charge batteries) as well as exporting and that might show up on your FITS as a significant increase - no idea what the implications would be.

I also thought you need to inform the DNO if you have a battery system grid tied, as you do if you have an EV charger or heat pump.

[nowty]

Whenever folk have got a FIT system, then any upgrades become awkward but not impossible. You could replace the current inverter for a hybrid system with batteries but if you wish to charge the batteries with off peak leccy, you need to replace your current generation meter with a bi-directional one. I.e. any imported leccy from the grid to charge the batteries is automatically subtracted from your generation meter. But I guarantee your domestic FIT provider wont have a clue what you are on about.

https://www.ofgem.gov.uk/sites/default/ ... idance.pdf

My advice would be leave the FIT system alone but add a AC coupled battery inverter on that phase with a light touch G99 DNO application.

Then you can add another system on the other phase at your leisure whenever and that could be a hybrid system if wanted.

[SafetyThird]

Thanks Paul/Nowty, that's making more sense. I don't want to export any more than 3.8kw, my understanding was that the inverter only allowed 3.8kw from the panels to be used, even if it's generating its max 6kw. For export that doesn't matter but if you wanted to be able to maximise charging potential, then it would.

For now, it looks like an AC coupled battery inverter and a stack of batteries is the way to go. The ME3000SP seems to be well regarded, along with the pylon tech setup. However, I'm liking the look of the Givenergy because there's a local installer who's a known quantity as he's done all the house electrics on my neighbours new build, including the solar and battery setup, and Givenergy is a UK company, so plenty of backup. Looking online I can get a 10.4kwh (2x5.2kwh) batteries with AC inverter and ancilliaries for £4350 or the same setup with a single 8.2kwh battery for £3200 which looks a pretty good deal and I could add more batteries in the future. Are other companies well thought of around these parts?

EDIT: apparently those are the old batteries and out of stock, new version would be new 5.2 or 9.5kwh apparently.

Add the lighting circuits and one of the upstairs ring mains that has the office and server cupboard to the battery output with a couple of 13A sockets in the mudroom and in case of an outage we can still see everywhere and keep working during the day. TV in the evening is just a case of running a single 13A extension into the snug.

Now, battery storage size......... any suggestions for how big I should go for, obviously bigger is better. Here's a few snaps from my Eddi data.










I'm thinking that 8.2 would be plenty for now with the option to go to 16.4 with an extra unit in the future, which would be handy if adding another set of panels on the barn. Any suggestions from knowledgeable folks on better ways to look at battery capacity?

[Countrypaul]

I have been looking at batteries for ourselves, and as a result have looked back over the last 12 months figures for PV production, amount imported and tried to calculate roughly what we might save with various sized batteries. In our case I have also looked at what we might save over winter by shfting some usage from daytime to battery using E7 charging. I am looking at an additional PV install and leaving the eisting system (FITS) untouched as Nowty has suggested. My understanding is that a hybrid inverter on the new PV array will be able to utilise any excess from the original as well as new PV system when the Eddi cannot divert it anymore (upto a limit).

We have an ASHP, and that mainly runs between 00:30 and 07:30, but in winter can run during the day if it is very cold. The heat pump is connected to a 430L thermal store, the whole house has UFH on the ground floor (Beam and Block, 120 PUR and 70mm screed with UFH). The TS does mean that the UFH can run for some time before triggering the ASHP. The Eddi is not yet setup to trigger the ASHP, but does trigger an immersion for DHW at the top of the TS.

As a result I suspect that battery size will vary from site to site and be very specific to each one. There would be no benefit in having a very large battery if you only ever used 10% of it, but likewise no point in having an undersized one if you fully cycled it and could use more.