Ground mounted solar PV installation project

[brewdexta]

Is that sheet metal roof your barn? What direction does that face? I wonder if my live stock building is strong enough for panels one side is about 5 degrees off due south!

AmI correct in thinking that if I have batteries and dont export any more juice than my existing 4kw system I could have as much as I wanted.

The roof is east west facing and is made of 80mm kingspan insulated panels. There are various mounting systems available, I paid for a detailed quote/study for solar and batteries about 3 years ago. I can look at what they proposed however the guy who fitted the roof came up with a cheaper option. That roof is another option but the east side is covered in trees.

In terms of how much solar you can have, if you go G98 then you can only export 16A per phase max. So, subject to planning, knock yourself out with solar panels as long as your inverter can handle it and meet G98 and max export of 16A per phase. Some inverters support more panel over subscription than others so you could have more panels and dump some energy into batteries and your hot water tank and still export some if weather permits.

 

[brewdexta]

I've ordered the remaining bits of ironwork, surprisingly expensive even after buying some second hand. Most of it was delivered this morning, I found that a local supplier of unistrut and bracketry was cheapest and delivered next day using their own transport. They specialised in sprinkler systems so didn't have all the brackets I needed but the lions share.

Next is the cables, isolators, DC MCBs, fuses etc. I want to do it all to the MCS spec, and they use IET guides.

I had a look for the IET Solar guide, its £69 as I'm not a member. I used to be a member of the IEEE many years ago, and there was a deal in terms of access to papers between them. I stopped membership when I stopped doing the lecture circuit.

Here's the guide

https://shop.theiet.org/e-book-code-of-practice-for-grid-connected-solar-photovoltaic-systems

But this looks like the first edition, and there's a second edition pending

Updates to IET Code of Practice for Grid-connected Solar PV Systems

The IET are accepting comments now on the draft 2nd Edition of their Code of Practice for Grid-connected Solar Photovoltaic Systems.

mcscertified.com

And there is also a separate code of practice for electrical energy storage systems, that's £72

The IET Shop - Code of Practice for Electrical Energy Storage Systems, 2nd Edition

The purpose of this Code of Practice is to provide a reference to practitioners on the safe, effective and competent application of electrical energy storage systems.

shop.theiet.org

If they were sensible cash I would buy both, ok for an installer but a bit steep for one off home use. I bet you don't get discount on the second edition

I have the design docs for the detailed quote I got back in 2018 for an East/West barn roof 11.8kWh system, but unfortunately it doesn't go down to isolator/fuse details. It covers cable sizes based on distance.

Its interesting looking at pricing then. There was 44 x 270W panels and 4 sunny boy inverters. It was a G59 DNO application as above 3.58kW. The solar quote was £19.4K, there was a couple of battery options, the 20.48kWh options was £17.5k. The study recommended more panels. My intended 4.68kW system pales into insignificance

On the DC side, my initial thoughts are that DC MCBs are not double pole isolators so I'll probably have one of those per PV string. There is a DC switch" built into the inverter however I haven't found out if this is PV, or battery or both yet and if it is double pole or single. If it is all, you may want to isolate the PV and battery separately so I'll probably go with separate isolators anyway.

I hate those plastic bayonet fitting in-line fuse holders so will probably use a couple of 20A megafuses and holders on each PV string. Cable wise, the PV will all be 4mm2. The max current is 12A and this can take 30A. Runs are pretty short as the equipment shed is next to the array, using 20m as a total single string run length, 200v as the nominal voltage and 12A max current, I get about 1.1% voltage drop which is fine.

On the battery side, the max discharge current of the inverter is 70A, so fuses need to be bigger than that but lower than the cable rating. The battery comes with cables, but I'll have an isolator & fuse on the battery too so will need some cable. The Inverter manual recommends AW6 so some 16mm2 cable will be needed. The cable run for this is about a metre so I'm not worried about voltage drop calcs.

The CT sensor also needs to be factored in. This tells the inverter what is being going on with the grid connection. The meter/CU is in the house and the inverter is about 30m away cable wise. I was thinking that the CT would need to be near the inverter, but the manual says up to 200m of AWG24 which meant I was able to site the inverter near the PV not the CU/meter.

The default package comes with WLAN, I can move an AP to get close enough for a decent signal, but I will also put a couple of CAT5e or 6 in between the inverter cabinet and the patch panel under the stairs, just in case.

On the AC side, my spark will deal with that, he's just back from holiday and is coming around on Friday to discuss. So he'll extend the inverter to the CU and install the Solar diverter and help fill in the G98 documents. I have the G98 engineering document for him to peruse to make sure the installation is up to scratch.

 

[m_c]

I ordered a Sofar inverter on Friday, as I figured the 8-10 weeks lead time would give me a chance to plan things, but the 8-10 weeks passed very quickly and it got delivered today :/7
It's quite a bit bigger than I thought it would be. I should really learn to look at dimensions before ordering things.

I was wondering why there seems to be a lack of information about installation requirements, but if you need to pay for the guides, that'll be why. I do know an electrician who used to specialise in renewables, but sods law dictates now that I want to ask his advise, I won't see him for months.

 

[brewdexta]

Same happened to me with my inverter, it is a big lump. I got a message that the battery is being dispatched, that was on 8 to 10 week lead time and has taken 2 weeks.

I'm getting a neighbour around to see if he can get onto this bit of land with his digger to level it a bit, it may help drop the profile of the panels a couple of inches and make a better job of it. I had assumed that I would have to take the wall down but another neighbour reckons he may be able to get it past the narrow bit with the aid of the bucket.

While that happens I'm going to crack on putting the roof and door on the little stone shed as the Inverter and soon, battery, will be getting in the way.

I stole this diagram from a facebook group for the G98 notification. Some DNO ask for a diagram, some don't but this is as detailed as you need.

 

[Maker]

Do you ground the negative side of the panels? Just wondering why there's no protective earth on the DC side of the inverter.

 

[brewdexta]

Generally no, you earth the solar panel frame but not the negative (assuming a negative earth system). Both solar chargers I have stipulate that, and the negative of the battery should be earthed. The victron has a chassis earth which is isolated from the panel/battery negatine. I presume the Sofar will too but haven't checked yet. I haven't been through the Pylontech lithium battery manual yet.

So generally no but best to check the inverter and battery manual to be sure.

 

[Robotstar5]

Same happened to me with my inverter, it is a big lump. I got a message that the battery is being dispatched, that was on 8 to 10 week lead time and has taken 2 weeks.

I'm getting a neighbour around to see if he can get onto this bit of land with his digger to level it a bit, it may help drop the profile of the panels a couple of inches and make a better job of it. I had assumed that I would have to take the wall down but another neighbour reckons he may be able to get it past the narrow bit with the aid of the bucket.

While that happens I'm going to crack on putting the roof and door on the little stone shed as the Inverter and soon, battery, will be getting in the way.

I stole this diagram from a facebook group for the G98 notification. Some DNO ask for a diagram, some don't but this is as detailed as you need.

View attachment 362070

How do you stop the PV backfeeding the grid in the event of a power outage?

 

[knighty]

How do you stop the PV backfeeding the grid in the event of a power outage?

the inverter does that, it's part of the whole G59 thing

 

[m_c]

How do you stop the PV backfeeding the grid in the event of a power outage?

As knighty says, it's part of the G98/99 regulations (which have superseded G59).
The official term is anti-islanding, whereby the inverter has to shut down in the event grid connection is lost.

 

[Robotstar5]

As knighty says, it's part of the G98/99 regulations (which have superseded G59).
The official term is anti-islanding, whereby the inverter has to shut down in the event grid connection is lost.

So does that mean it won't power the CU to keep the house running during a power outage?

 

[m_c]

So does that mean it won't power the CU to keep the house running during a power outage?

Correct.
Some inverters do have an islanding function, but I'm not sure any pure solar inverters will have it, certainly any G98/99 certified ones shouldn't, but it would immediately shut down due to overload if it was still connected to the grid.

However some hybrid inverters (like the Sofar ones brewdexta and I have bought), have an Emergency Power Output (EPS), which isn't grid-tied as such, and will provide power from the batteries in the event of grid failure. It's essentially a glorified UPS, in that the EPS output is grid powered, until the grid fails, at which point the inverter takes over powering that circuit.

 

[brewdexta]

Beat me to it

I haven't worked out how best to reconfigure my CU to take advantage of this second output yet. The barn is where the freezer and techie stuff is, but also the EV charger hangs off of that, which i think will be too big a load for this. So I'll probably dig in some more SWA to the charger from the house so I can hang the barn, bore hole pump and boiler room off this output.

That's definitely stage 2. I'm discussing this with the spark on Friday. I'm focused on getting the PV up an earning its keep first.

 

[fizzy]

What are you doing for storage? Missed this thread but when I looked into it for my place in Portugal forklift batteries are far cheaper than the equivalent lithium ion. And obviously weight doesn't really matter for a static install.
My forklift is 48v DC input and outputs 3 phase, Battery is around 1200 amp/h. Cost about £3,000 but probably more now.. In theory that is a 57kw battery but in practice probably about 45kw/h.

 

[minimutly]

Correct.
Some inverters do have an islanding function, but I'm not sure any pure solar inverters will have it, certainly any G98/99 certified ones shouldn't, but it would immediately shut down due to overload if it was still connected to the grid.

However some hybrid inverters (like the Sofar ones brewdexta and I have bought), have an Emergency Power Output (EPS), which isn't grid-tied as such, and will provide power from the batteries in the event of grid failure. It's essentially a glorified UPS, in that the EPS output is grid powered, until the grid fails, at which point the inverter takes over powering that circuit.

Type tested domestic is G83 from memory, unless it was updated to newer regs. Just a name to the regs, doesn't change anything...

 

[brewdexta]

What are you doing for storage? Missed this thread but when I looked into it for my place in Portugal forklift batteries are far cheaper than the equivalent lithium ion. And obviously weight doesn't really matter for a static install.
My forklift is 48v DC input and outputs 3 phase, Battery is around 1200 amp/h. Cost about £3,000 but probably more now.. In theory that is a 57kw battery but in practice probably about 45kw/h.

I've bought a 2.5kWh lithium battery for starters. Depth of discharge is up to 95% so mostly usable.

I've gone light on the battery for now. During the summer I'll be putting as much as I can into the hot water cylinder so I can turn the big log/pellet boiler off as its costing me lots just for HW.

In winter I'll not bother with the hot water diverter as the boiler will be on for CH anyway. But the sun will be weaker so may not need a big battery with a 4kw max PV array.

But, if I export more than very occasionally, I'll plug in more batteries. As my installation will not be MCS registered, I won't get SEG payments, and they are a pittance anyway so export is a last resort.

 

[fizzy]

I've bought a 2.5kWh lithium battery for starters. Depth of discharge is up to 95% so mostly usable.

I've gone light on the battery for now. During the summer I'll be putting as much as I can into the hot water cylinder so I can turn the big log/pellet boiler off as its costing me lots just for HW.

In winter I'll not bother with the hot water diverter as the boiler will be on for CH anyway. But the sun will be weaker so may not need a big battery with a 4kw max PV array.

But, if I export more than very occasionally, I'll plug in more batteries. As my installation will not be MCS registered, I won't get SEG payments, and they are a pittance anyway so export is a last resort.

A bit different in Portugal.
A 4KW array will give me that most of the year. House gets so hot I will put aircon in each room so they will definitely suck up most of it. Going to let the place out as an AIRBNB hopefully. Guests won't be around much in the day but aircon will help a lot at night.
Plenty of land there so no problem with siting the panels.
It's a lovely place and a stunning house but far too hot for me.
Serious drought now though. Wells have almost run dry - water table is probably 40 feet lower than when my Dad bought the place back in the 1980s.

 

[sako243]

45kw/h

Being a pedant that's kWh not kw/h.

James Watt was a person hence why it's capitalised, Watts are a measure of how quickly work is being done, i.e. energy consumed per second where 1 Watt = 1 Joule (another person) per second. So you're saying your battery can "accelerate" 45kJ/s²

 

[Maker]

Being a pedant that's kWh not kw/h.

James Watt was a person hence why it's capitalised, Watts are a measure of how quickly work is being done, i.e. energy consumed per second where 1 Watt = 1 Joule (another person) per second. So you're saying your battery can "accelerate" 45kJ/s²

The manual that came with our router gives the power consumption in watts/second:


Got it back in March, so it must be up to about 200MW by now, no wonder the leccy bill is so high!

 

[daleyd]

The manual that came with our router gives the power consumption in watts/second:
View attachment 362092

Got it back in March, so it must be up to about 200MW by now, no wonder the leccy bill is so high!

I think units like watts are only capitalised when written as a symbol (W,V…), when written in a sentence it’s simply watt, volt etc and uncapitalised unless at the start of the sentence.

 

[brewdexta]

I always capitalise watts if I remember.

Also, its not KW, its kW for kilowatt

Pedantry over. My mum is coming over today, then I'm heading over to Whitby at the weekend to drop her off home so mum stops play

I've got a couple of things to order then I'll resume next week, I really want to get this in an working soonest, not just as it needs to be earning its keep, it was a last minute decision due to energy prices so its pushing other DIY projects back,. This means my Fordson Dexta renovation project that I vowed to restart next year is likely to get pushed back again, its only been in bits for 15 years.......