The Solar Thread

The s/w and s/e array are each meant to be on separate input to the inverter

I take it they are?  As I said before, it’s tricky troubleshooting when the weather is not optimal – much easier when it’s sunny and you know roughly what should be happening.

My money is still on crappy weather.

Managed a measly 1.4kw so far today.

Luxury – 0.35 here!

Was very murky all day, bar about one hour when we generated 0.2 kW.

@Footflaps where are you and how big is your array and what orientation?

The weather has been very patchy the last few days. We’ve been down in London; some times it’s been glorious weather there while our panels back in Telford have been doing nothing, but at other times murky, damp weather there while our panels back home have been doing 5kw!

I can easily believe that the last day or so luck could be the difference between a couple of great solar days and a couple of terrible ones.

I put a 4.2kw array into a shop/flat I own (rented out) around 4 years ago. S/W facing roof. The whole building is electric only so I did it to help lower the tenants bills. I get the FIT which is somewhere around £130/year.
I’ve no remote access and have never bothered tracking how it’s doing apart from submitting quarterly meter readings to the FIT provider.

I recently put the figures I have from the FIT rebate remittances into a spreadsheet, looks like it’s performing reasonably well?

Just to bang on again about the PGVIS model. If you are thinking of solar it gives you a very good estimate of your possible gain. I have been surprised so far as to its accuracy.

Planning? A flat roof would require a ground mount style frame to mount the panels – that’s going to stand out somewhat!

Dug around on the Edinburgh planning portal last night. Neighbours with panels who did apply were told it did not need consent as it was not visible from ground level. So seems ok to crack on from that perspective.

Just out of interest how are the installers going to hold the frames down?

Just out of interest how are the installers going to hold the frames down?

Preferred (and likely) method is to drill through the roof to attach them, but they can use a ballast system if that is deemed not possible.

Preferred (and likely) method is to drill through the roof to attach them

As the son of an architect who’s mantra was to never drill into a flat roof, that worries me.  What do you think the chances are of all those holes remaining watertight over a period of 10 years?

(See also balustrades fitted onto flat roofs rather than onto the fascia)

Lovely day for generation, but to illustrate the difference between S facing arrays and E/W facing arrays this is the current state of play of my two setups:

4kW E/W Array:

Date – Time – [Total] Energy – Efficiency – [Current] Power

23/02/23 – 11:30AM – 3.200kWh – 0.801kWh/kW – 1,335W

3kW S Array:

Date – Time – [Total] Energy – Efficiency – [Current] Power

23/02/23 – 11:30AM – 6.713kWh – 2.238kWh/kW – 2,325W

!!

What do you think the chances are of all those holes remaining watertight over a period of 10 years?

Not an architect or engineer so to be honest, I’ve no idea.

Thus far just putting my trust in…
1. Both methods seemingly being established methods for fitting to flat roof.

2. Putting trust in a reputable company to guide me. Many cowboys out there but this one come well reviewed and personal recommendation from people I know.

But still not committed to anything so open to other opinions.

What do you think the chances are of all those holes remaining watertight over a period of 10 years?

If it’s done properly with proper seals and cowls then quite high.

A quick google suggest most flat roof system just sit on top and use ballast, which is a lot simpler…

https://www.valksolarsystems.com/en/solar-mounting-systems/kits/flat-roofs/solar-ramp/valktriple

We’ve always used ballast when installing antennas on flat roofs, but they have blown over in exceptionally windy conditions. Not sure how happy I’d be with a load of sails (solar panels) waiting to be lifted off the roof in the next gale….

@Sharkbait – what’s a lovely day for generation- blue sky and sunshine?

We’ve always used ballast when installing antennas on flat roofs, but they have blown over in exceptionally windy conditions. Not sure how happy I’d be with a load of sails (solar panels) waiting to be lifted off the roof in the next gale….

Yeah, we are quite exposed, basically it’s downhill for miles until it hits the Forth, and a single story property next door which means we have lovely clear views for miles from 2nd floor, but also really bloody exposed to the elements. I’m not sure I would be 100% on the use of ballast, but again I’d put trust in them. They did say that the ballast option is likely to be more expensive due to the amount that would be needed, it would be harder to get up and weight on the roof may be too much.

I was thinking that if we ever do a roof conversion we’d end up moving the solar panels to a flat roof, so I was thinking of making a frame which bolted into the walls at either end, had feet sat on the roof mid span and then bolt the solar panels to that, so they can lift off without ripping bolts out the walls….

Obvs be a bespoke frame, but fairly easy to make out of galvanised steel.

Not sure how happy I’d be with a load of sails (solar panels) waiting to be lifted off the roof in the next gale….

a wind load survey would quickly force you to use solar ballast buckets such as the renusol console

These enclose the back of the panel from the wind reducing sail effect

As Doug points out though cost and weight quickly mount

so I was thinking of making a frame which bolted into the walls at either end, had feet sat on the roof mid span and then bolt the solar panels to that, so they can lift off without ripping bolts out the walls….

quite sure Doug will want an mcs certificate which a home brew mounting system won’t get

quite sure Doug will want an mcs certificate which a home brew mounting system won’t get

It’s not any different to how the installer we used mounts panels on gable ends etc, they just knock up bespoke frames out of square section steel tubing on site to mount the panels as required…

Plus in our case, which is what I was talking about, we already have all the certificates….

quite sure Doug will want an mcs certificate which a home brew mounting system won’t get

Yup and got to be supplied and installed by them to get the Home Energy Scotland grant and loan. Plus I hate heights so no chance I’m going up on the roof.

We’ve got a flat garage roof in Glasgow (approx 5.5m x 4m / 23m2) that gets sun most of the day, effectively our only potential for south facing. The house is E/W and North facing and is Victorian semi so wouldn’t be appreciated by neighbours… Looking at option of putting 10/12 panels on the garage and rear extension, or 9 on garage and 3 on a frame next to the garage out of sight…

Would be going over a 2 year old sika liquid plastic roof – looking at the plastic trays for ballasting or else knock up a frame with pads to spread the load. There is a small ~300mm parapet upstand around the roof so shouldn’t be “too” exposed to wind…

Is there a go to DIY package on the web, or a go to panel type that is considered the best value for money for this type of setup? There seem to be loads to choose from.

My facebook feed is now full of firm after firm offering 12 panels + inverter + battery deals from £5k to 13k… Plenty of DIY kits come up in google but it would be good to have a real recommendation from someone who has done something similar.

Electric company car coming in May will change our usage / might be looking at car charging point and a house battery setup too? Hard to know which way to go.

Sale of our existing car may provide some of the funds for this project. Looking for a bit of energy future proofing but will only do it if numbers work. I appreciate Glasgow and flat roof aren’t perfect.

We consumed 7783kWh last year, = 21kWh per day. Expecting this to go up next year with car charging.

Any help would be greatly appreciated, thanks.

Any help would be greatly appreciated, thanks.

Run the numbers first to see what you could generate from the available area.

https://re.jrc.ec.europa.eu/pvg_tools/en/

Looking at option of putting 10/12 panels on the garage and rear extension

Again, check that you don’t need planning as a panel on the garahe roof is going to add probably 1m to the height .

ideal thanks

If putting panels on a single storey building check they won’t be shaded.

A home battery will pay for itself quite quickly if you make use of the Octopus Go tariff which you should consider anyway when the EV arrives.

Although using 21 kWh a day, that’s going to be a large & expensive battery!

Although using 21 kWh a day, that’s going to be a large & expensive battery!

Unless he uses 21kWh at night it doesn’t have to be that large. Its not good economics to size a battery to cover you in December as it will take an age to get payback. Most of the year solar will cover 20-100% of your requirements so size the battery accordingly.

Although using 21 kWh a day, that’s going to be a large & expensive battery!

Logical thinking would be to think of a battery as a capacitor.

Remove the export since rates are derisory (without being able to control when it’s exported)

Going “off grid ” is expensive ….how ever removing a large chunk of your import is reasonably cheap by comparison

We consumed 7783kWh last year, = 21kWh per day. Expecting this to go up next year with car charging.

If it helps with your working out, we produced 4000kwH in Glasgow last year (feb-feb). From all accounts that was a good year. We were quoted to expect approx 2500-3000kwh based on location/aspect. That’s a south facing roof with 4.6kw panels tied in to the standard 3.65kw inverter. No battery.
Be advised though, 70% of the production occurred feb-august. August-Feb sporadic at best in Glasgow. Our biggest saving comes from the iboost to heat the water.

I finished installing the second battery today along with all of the associated wiring and ducting – just in time too. Even given the power off time whilst I wired it up, it was a 17kWh day! Saw a new peak power from the array of 4.89kW, but only briefly as it’s intermittently cloudy.

There’s now ~19kWh of storage on the side of the house, which should do us even on very busy days.

I wish there was more information from
The BMS about how it’s doing its job between the packs as they’re quite different in size to one another, but I can’t find anything through the inverter. I’ll try to ask LG.

New peak for us …from a 4.14kWh array plugged into a 3.6 inverter.

Never saw that in the last 18 months. Peaked at 3.8kWh last April with the last 3.6 inverter. Summer sun never gets close to that with the excess heat.

Remove the export since rates are derisory (without being able to control when it’s exported)

I buy at circa 18p a kW on Eco7 then if I do export any I get circa 15p per kW. I dont buy any at the expensive rate since early Feb so the export works ok for us.

Trailrat what app is that? 😁

Solis numberjumbler app

Remove the export since rates are derisory (without being able to control when it’s exported)

We’ve just signed up to Octopus’ dynamic export rate, although not yet seen the prices they offer.

Not sure if it’s the same as their “Agile” tariff, where the unit price varies every 30 mins.

If doing a smart plug immersion solution to excess generation, can I stick a dimmer switch rather than an on off after the fuse spur
to scale down consumption? Problem is the inverter can only push 5kw so if i boil the kettle then I’m drawing power from the grid.

Will that shorten its life?

I buy at circa 18p a kW on Eco7 then if I do export any I get circa 15p per kW. I dont buy any at the expensive rate since early Feb so the export works ok for us.

hence the my brackets in your original part quote – what you are doing would not be possible without the ability to control when the export happens ( IE batteries)

f doing a smart plug immersion solution to excess generation, can I stick a dimmer switch rather than an on off after the fuse spur
to scale down consumption?

that sounds like a really shonky and quite probably dangerous way to solve something where an off the shelf qualified product exists already to perform that function.

worth noting that few smart plugs are rated to an immersions draw on continuous current. most will do it peak but not continuous.

Problem is the inverter can only push 5kw so if i boil the kettle then I’m drawing power from the grid.

The immersion shunt unit should sense that you’re pulling current from the grid and back off the current to the immersion whilst the kettle is boiling…..

Plus, how long do you boil a kettle for? 1 minute tops?

Yes having done a quick google, lighting doesn’t run at 13 amp so a high current rheostat is needed and it needs a heat sink too.

If there’s a dimmer will the smart plug need to do 13a – theoretical question. I’ve discounted as not a very practical idea.

Footflaps- I don’t have an I boost or similar so immersion just runs at full tilt when on