Ground mounted solar PV installation project

[Gareth J]

I found some second hand unistrut, its 6m long, which I wanted, but double the width at 41 x 82 but it will do. It was cheap and delivered. 7 x 6m lengths in total, so good enough to cover most of the install.
View attachment 360074
I got chatting to a mate who installed my biomass boiler. He's MCS registered on the heating side and confirmed what I had discovered from chatting to others as follows.

You don't need the installation to be MCS registered to connect to the grid. Just by a competent person, i.e. a spark.

But the installation will need to comply with the relevant grid connection standards. In my case this is G98, so 16A max or 3.68kW, but there are others.

For G98 you can connect and notify the DNO, but for others like G99 you have to notify first.

If you want to get SEG, today's equivalent of the old FIT, i.e paying to export for the measly 5 to 7.5p per unit, then you need the install to be completed by MCS registered installers.

Same goes if you want the Tesla deal where you can get symmetric tariffs i.e. same price for import or export. The Tesla battery deal is something like 25p per unit in or out, there are deals if you have Tesla car too, I think you have to via Octopus, I'm still looking into this.

If you want to get 0% on the installation , then if has to be via an MCS registered company. The Sunak budget basically extended the existing 5% on renewables to 0% for a couple of years.

The 8 to 10 week lead time on the hybrid inverter I ordered turned out to be 2 weeks so should be arriving this week.

This accelerates things as I was betting on being able to cancel the order if I decided to go via the MCS route as I have a few enquiries in process.

Basically, unless the Tesla route proves compelling, the MCS path doesn't offer me much. As one of my major costs is heating hot water in summer via biomass then using solar to do this would compete with charging the 12.5kWh Tesla battery. Plus my intended 4 to 4.5kWp solar install is a bit small.

So, for me, a smaller battery plus a diverter to power the immersion heater would probably be the sweet spot, avoiding export to the grid, other than a last resort.

But I'll keep my mind open until the last decision point.

I couldn't justify an MCS install for either of our non FiT arrays either. Might come back to bite me if ever they pay fairly for exported units but not currently.

I currently have a few solar diverter widgets, it's quite easy to get one to cascade charging from one hot water immersion, to another or a night storage heater. Send me a message and I'll draw a schematic if that's of interest. Am also trying to figuring out/price up assembling some bits and pieces to create a customisable plug socket that works on the principal of;

IF; measured current (export/generation/whatever) exceeds a preset threshold, close a relay for Xminutes.

Such off the shelf things kind of exist but I'd like it all to work wirelessly, so I can move an enclosure, with a plug on one end and a socket the other around, within WiFi (or otherwise) range.

Should let me somewhat intelligently control things other than dumb immersions. Like a dehumidifier, a beer fridge, or, potentially, an AC unit, or a heat pump.

 

[brewdexta]

I couldn't justify an MCS install for either of our non FiT arrays either. Might come back to bite me if ever they pay fairly for exported units but not currently.

I currently have a few solar diverter widgets, it's quite easy to get one to cascade charging from one hot water immersion, to another or a night storage heater. Send me a message and I'll draw a schematic if that's of interest. Am also trying to figuring out/price up assembling some bits and pieces to create a customisable plug socket that works on the principal of;

IF; measured current (export/generation/whatever) exceeds a preset threshold, close a relay for Xminutes.

Such off the shelf things kind of exist but I'd like it all to work wirelessly, so I can move an enclosure, with a plug on one end and a socket the other around, within WiFi (or otherwise) range.

Should let me somewhat intelligently control things other than dumb immersions. Like a dehumidifier, a beer fridge, or, potentially, an AC unit, or a heat pump.

Schematics would be good

 

[brewdexta]

Try tracking your hourly usage for a few weeks / months to see just when you use the most power & energy.

I have for the last 6 months

All the data from the meter is in an InfluxDB time series database, I can then manipulate the data with Grafana to show what I need

Here's the last 30 days

and the last 2 days, the wife topped up the EV when she got home around 11pm last night

A day's usage without EV charging is around 16 to 20kWh

With EV charging, it depends how deep the batteries are discharged. We rarely take it down to empty so usually adds about 40kWh on that day, from memory its a 59kWh battery on the current Leaf that we have.

There are loads of strategies I could use

1.) Slow down the EV charging and do it during the day, not always practical if she's working during the day and needs to get there by car
2.) Get an energy tariff with cheaper night rate to charge the EV and use the Solar PV and battery to heat hot water and extend none grid electricity usage when the grid isn't cheap

etc. etc.

I can tinker with that once the system is in and running.

 

[Gareth J]

Schematics would be good

"Schematic" might be pushing it a bit but hopefully you get the gist. You need a thermostat for the first resistive load that has both "call" and "satisfied" positions. Most immersions don't have that so I've used separate tank strapped ones that do.

Once the top of tank, or first tank is satisfied, diversion flips to the second resistive load, which is wired as normal....unless you have another load to heat first, in which case repeat the wiring for the first.

There is a flaw with this design though - those diverters heat wiring/switches quite a lot. That means that the external thermostat I've used, in practice, gets too hot and thinks the tank is hot when in reality, just the thermostat itself is hot. Easily solved by extending the wiring to a sturdy relay. But a pain.

 

[Mick Annick]

I looked at building a panel controller ages ago and it really didn't look difficult or expensive to make it move to follow the sun every ten minutes, and the difference in output was significant. I think I still have some photosensitive resistors and an Arduino somewhere in a box of old project stuff to get round to one day!

I have a friend here who is very keen on solar, he has a small array but they all tilt and swivel to track the sun throughout the day, though no idea how it works.

 

[brewdexta]

View attachment 360160
"Schematic" might be pushing it a bit but hopefully you get the gist. You need a thermostat for the first resistive load that has both "call" and "satisfied" positions. Most immersions don't have that so I've used separate tank strapped ones that do.

Once the top of tank, or first tank is satisfied, diversion flips to the second resistive load, which is wired as normal....unless you have another load to heat first, in which case repeat the wiring for the first.

There is a flaw with this design though - those diverters heat wiring/switches quite a lot. That means that the external thermostat I've used, in practice, gets too hot and thinks the tank is hot when in reality, just the thermostat itself is hot. Easily solved by extending the wiring to a sturdy relay. But a pain.

Thanks for this, most immersion heaters are near the top of the cylinder, so a bit of a recirculation pumping is sometimes in order too.

I've been looking at 2 different power diverters
One the Apollo, which was British made, is unfortunately no longer made due to problems getting hold of components https://www.apollosolarelectric.co.uk/ My heating engineer highly rated them and they had a recirc feature either built in or was being built in.
The second is this one https://www.powerdiverter.com/products, an Aussie product.

I believe there are a few more so going to look at them and their features/cost.

The inverter arrived, its a big bit of kit and I've nearly settled on the make and model of panel, I'm going to put an order in for the panels, batteries, isolators etc.

Looks like I'm going non-MCS and only export as a very last resource.

 

[dobbslc]

View attachment 360160
"Schematic" might be pushing it a bit but hopefully you get the gist. You need a thermostat for the first resistive load that has both "call" and "satisfied" positions. Most immersions don't have that so I've used separate tank strapped ones that do.

Once the top of tank, or first tank is satisfied, diversion flips to the second resistive load, which is wired as normal....unless you have another load to heat first, in which case repeat the wiring for the first.

There is a flaw with this design though - those diverters heat wiring/switches quite a lot. That means that the external thermostat I've used, in practice, gets too hot and thinks the tank is hot when in reality, just the thermostat itself is hot. Easily solved by extending the wiring to a sturdy relay. But a pain.

When you say diverter are you talking about the thermostat in your drawing?
I'm thinking of using your idea to heat a second hot water cylinder instead of replacing the almost new one I already have. It'll save a fair bit of plumbing!

 

[Gareth J]

Thanks for this, most immersion heaters are near the top of the cylinder, so a bit of a recirculation pumping is sometimes in order too.

I've been looking at 2 different power diverters
One the Apollo, which was British made, is unfortunately no longer made due to problems getting hold of components https://www.apollosolarelectric.co.uk/ My heating engineer highly rated them and they had a recirc feature either built in or was being built in.
The second is this one https://www.powerdiverter.com/products, an Aussie product.

I believe there are a few more so going to look at them and their features/cost.

The inverter arrived, its a big bit of kit and I've nearly settled on the make and model of panel, I'm going to put an order in for the panels, batteries, isolators etc.

Looks like I'm going non-MCS and only export as a very last resource.

I think these are worth considering;

Mk2PVRouter - Introduction

A DIY Constructor’s project to build a Mk2 PV Router system for surplus energy diversion.

mk2pvrouter.co.uk

A bit DIY and I've not got one personally but a significant saving on off the shelf ones which are currently way more expensive than they were a year or three ago

 

[Gareth J]

When you say diverter are you talking about the thermostat in your drawing?
I'm thinking of using your idea to heat a second hot water cylinder instead of replacing the almost new one I already have. It'll save a fair bit of plumbing!

Sorry, I don't understand what bit you're referring to. Apologies, it's a rubbish, quick drawing. I ought to draw out a better version anyway so I can log what I've done in my own cupboard. If I get round to it, I'll post it here.

But yes, set up like that it'll cascade from one dump load to the next as they fill.

The iBoost+ and some other diverters do this automatically. At a price.

 

[addjunkie]

This is the one I have. Someuseful info in the manual.

https://myenergi.com/wp-content/uploads/2022/06/Eddi-Manual-.pdf

 

[dobbslc]

Sorry, I don't understand what bit you're referring to. Apologies, it's a rubbish, quick drawing. I ought to draw out a better version anyway so I can log what I've done in my own cupboard. If I get round to it, I'll post it here.

But yes, set up like that it'll cascade from one dump load to the next as they fill.

The iBoost+ and some other diverters do this automatically. At a price.

I was trying to work out what was getting hot, the stat or the diverter ( is the diverter the iBoost thing?).
If 2 or 3 kw is running through the stat that might be why it's hot as I think they are only meant to control the boiler pcb normally.

 

[brewdexta]

This is the one I have. Someuseful info in the manual.

https://myenergi.com/wp-content/uploads/2022/06/Eddi-Manual-.pdf

Nice, on page 50 it shows how to use it with a destratification pump

So looks like I have 3 to look at and compare so far, the Eddi (about £390) iboost (about £370) and the Aussie power diverter (£350)

 

[addjunkie]

Nice, on page 50 it shows how to use it with a destratification pump

So looks like I have 3 to look at and compare so far, the Eddi (about £390) iboost (about £370) and the Aussie power diverter (£350)

The bit which might work for you, may be the ability to tie in their intelligent car charger too, but dont know enough about it. Though there is another widget that allows you to use the juice in the car battery at night too.

Im trying to line up a roofer to do integrated panels in one of my holiday cottages with a view to having the sewage treatment plant and ch pump a constant demand covered during day light hours but also throwing in a car charger too. Regret not just putting the panels in when we did the roof and not connecting it at the time, but money was tight and the budget was my money!

 

[Gareth J]

I was trying to work out what was getting hot, the stat or the diverter ( is the diverter the iBoost thing?).
If 2 or 3 kw is running through the stat that might be why it's hot as I think they are only meant to control the boiler pcb normally.

Ah right. The thermostat. Supposed to be 16A rated, I've used Horstmann HCT2 ones. But, especially burried in tank foam, they get quite warm.

 

[dobbslc]

Thanks. The MK 13A spur I used on a 3kw heater was getting so hot I had to turn it off, poor quality!
Ended up with a 20A double pole switch that takes the current better.

 

[Gareth J]

Nice, on page 50 it shows how to use it with a destratification pump

So looks like I have 3 to look at and compare so far, the Eddi (about £390) iboost (about £370) and the Aussie power diverter (£350)

If you don't need timed boosting, the Solic200 is great. Cheaper than the others, robust and UK built with apparently a 10yr warranty. I've got two, they work well with a zero W threshold too.

But like I said before, am tempted by the DIY version I linked to

 

[Gareth J]

Thanks. The MK 13A spur I used on a 3kw heater was getting so hot I had to turn it off, poor quality!
Ended up with a 20A double pole switch that takes the current better.

Yes, I've gone 20A for all components now. With 2.5mm cable. Pay particular attention to wire connectors, have melted a box connector that came a bit loose. I think the PWM flavour of diverted electric is particularly hard on stuff.

 

[minimutly]

The bit which might work for you, may be the ability to tie in their intelligent car charger too, but dont know enough about it. Though there is another widget that allows you to use the juice in the car battery at night too.

Im trying to line up a roofer to do integrated panels in one of my holiday cottages with a view to having the sewage treatment plant and ch pump a constant demand covered during day light hours but also throwing in a car charger too. Regret not just putting the panels in when we did the roof and not connecting it at the time, but money was tight and the budget was my money!

Integrated panels, supposedly the best way - hardly seen though. Is it worth the hassle?

 

[brewdexta]

I'm just totting up the costs and including setting aside £500 for cables, isolators and fuses that I haven't completely itemised yet, its coming out at £5285.

This includes, the hybrid inverter, 4.68kWp of panels (the inverter max is 4.79 kWp), estimating 450 for the diverter as I'm still looking at spec;, 2.4k of lithium battery (the battery is compatible with the inverter BMS), and ironwork for mounting the panels.

My spark is on holiday at the moment, so I don't know his costs yet, but if I get all the cables installed ready for termination then I think he will charge a couple of hundred,

I'll be happy to get it all under £6k as there are always the odd problem to solve. I've deliberately gone light on the battery, I can always add more once I see how the dynamic between the immersion inverter and the battery works in reality.

 

[knighty]

I'd miss the battery out until later on... wait and see how much power you're actually exporting first

£2400 buys you a lot of import... especially if you're diverting excess power into your hot water tank