Solar Panels?

[Griffith4ever]

snowman99 said:

RemarkLima said:

Interesting thread...

Are the DIY kits any good?

https://www.roofgiant.com/flat-roofing-solar/plug-...

More for charging a car in the day for example, and the day time use... I have a flat roof garage some these could be placed on top without too much pain...

When they say DIY, how DIY is it really, it’s hardly going to be plugging the panels into a mains socket?

Seemingly, yes!

Well, they have you install mini inverters behind the panels, link them all up, then wire the resulting L,N & E into the back of a wall mounted isolator.

https://www.insulationsuperstore.co.uk/user/u/pimp...




Interesting. Done some more reading. These systems use grid tie inverters - they convert the DC to AC and they shut the output off if they detect a voltage drop (so they don't feed back into the grid - a safety requirement).

An article explaining them a bit better whilst trying to say "don't buy them" and at the same time managing mostly to only come up with trip hazard and ugly https://www.solarreviews.com/blog/dont-invest-in-p...

Edited by Griffith4ever on Friday 18th March 15:01

[RemarkLima]

Griffith4ever said:

snowman99 said:

RemarkLima said:

Interesting thread...

Are the DIY kits any good?

https://www.roofgiant.com/flat-roofing-solar/plug-...

More for charging a car in the day for example, and the day time use... I have a flat roof garage some these could be placed on top without too much pain...

When they say DIY, how DIY is it really, it’s hardly going to be plugging the panels into a mains socket?

Seemingly, yes!

Well, they have you install mini inverters behind the panels, link them all up, then wire the resulting L,N & E into the back of a wall socket of your choice - via an isolator.

https://www.insulationsuperstore.co.uk/user/u/pimp...

That's it, and I know a decent sparky who would charge half a days work to hook it all up... I guess what I do not understand, is how does your internal draw use this over the grid? Electronics are a bit of a dark art to my mind!

[Griffith4ever]

RemarkLima said:

That's it, and I know a decent sparky who would charge half a days work to hook it all up... I guess what I do not understand, is how does your internal draw use this over the grid? Electronics are a bit of a dark art to my mind!

I updated my post above.

They use inverters and simply pump the power into your existing ring main. When you use appliances, the draw comes from the path of least resistance which will be the solar at 1st.

https://www.pluginsolar.co.uk/?page_id=58

What I gleaned from reading another page (linked above) is: install the isolator on it's own circuit. Dead easy - add an RCD, run cable to the isolator, plug the solar in.

OFC it totally relies on you using power during the day time

Edited by Griffith4ever on Friday 18th March 15:05

[RemarkLima]

Griffith4ever said:

RemarkLima said:

That's it, and I know a decent sparky who would charge half a days work to hook it all up... I guess what I do not understand, is how does your internal draw use this over the grid? Electronics are a bit of a dark art to my mind!

I updated my post above.

They use inverters and simply pump the power into your existing ring main. When you use appliances, the draw comes from the path of least resistance which will be the solar at 1st.

https://www.pluginsolar.co.uk/?page_id=58

What I gleaned from reading another page (linked above) is: install the isolator on it's own circuit. Dead easy - add an RCD, run cable to the isolator, plug the solar in.

OFC it totally relies on you using power during the day time

Edited by Griffith4ever on Friday 18th March 15:05

Ah, I see - makes sense.

They do sell battery storage with those kits so assume it's the same principle?

[Traffic]

Traffic said:

Added some numbers to another thread a while back, no harm in adding some refreshed numbers here....

March 2022
Total Electricity Consumed = 868Kwh

• 71% from the grid = 620Kwh
• 29% from solar panels = 247Kwh

Electric costs for the 620Kwh consumption = 1,197 Swedish Krona

Surplus solar electricity sold to the grid 483Kwh = 714 Swedish Krona.

Not bad for chilly Sweden in March! :-)

64kWh in the bank today, my best day yet! :-)

[Sheets Tabuer]

Notice a few struggling with figures, this might help

https://www.pvfitcalculator.energysavingtrust.org....

[Gareth79]

RemarkLima said:

Ah, I see - makes sense.

They do sell battery storage with those kits so assume it's the same principle?

Learning this from scratch myself, yes pretty much, although for battery storage wired separately you'd need some sort of monitoring to ensure that the battery only charges when the panels are producing. You can get combined inverters and battery chargers which deal with that all in one, but I'd think a separate battery charger/controller would be better unless the combined unit has a comprehensive control system.

[ARHarh]

Gareth79 said:

Learning this from scratch myself, yes pretty much, although for battery storage wired separately you'd need some sort of monitoring to ensure that the battery only charges when the panels are producing. You can get combined inverters and battery chargers which deal with that all in one, but I'd think a separate battery charger/controller would be better unless the combined unit has a comprehensive control system.

Just checked out that site with my details and its 500kwh a year short of what I generate. About 15% short, that's quite a lot.

[gmaz]

Sheets Tabuer said:

Notice a few struggling with figures, this might help

https://www.pvfitcalculator.energysavingtrust.org....

I ran my system through that calculator and the total generation value seems to be low.

I had my install done in mid-May 2021 and last year it generated 2939kWh, But the calculator says I can expect 3532kWh for the whole year which is about 1000kWh lower than I expect.

Generation from mid-May 2021 to mid-March 2022 is already 3461kwh and the next couple of months are the best generating based on temp and roof/sun angle.

[Gareth79]

Griffith4ever said:

OFC it totally relies on you using power during the day time

Oh yes I meant to add - yes because it's not installed by an MCS installer it's basically impossible to get paid for export power back to the grid (it will happen, but you are giving it away ). It's not legally required, but AFAIK no power companies will set up SEG export without an MCS installation certificate.

[Condi]

If you knew a friendly MCS registered electrician could it not get signed off? Is there any technical reason why it has to be done by a qualified person?

[Gareth79]

Condi said:

If you knew a friendly MCS registered electrician could it not get signed off? Is there any technical reason why it has to be done by a qualified person?

From what I understand, MCS is end-to-end certification of the entire process right from approved manufacturers to customer service standards, warranties etc, a bit like FENSA for windows, rather than just signing off that the installation is done correctly. Therefore I don't think an MCS installer would want to "take ownership" of a DIY install unless it was somebody they knew very well.

[SDK]

Jambo85 said:

With a 3kW system (quite small really), if you have a hot water cylinder with immersion heater, then a diverter to put excess power there will probably use most of your surplus. And is a lot cheaper than a battery.

If your dishwasher and washing machine will accept hot feeds then you can effectively use your hot water cylinder as a battery for them.

Useful to know this - obviously that works during the summer months and wouldn't by great through Winter, where a battery charged overnight could support those.

[Jambo85]

SDK said:

Jambo85 said:

With a 3kW system (quite small really), if you have a hot water cylinder with immersion heater, then a diverter to put excess power there will probably use most of your surplus. And is a lot cheaper than a battery.

If your dishwasher and washing machine will accept hot feeds then you can effectively use your hot water cylinder as a battery for them.

Useful to know this - obviously that works during the summer months and wouldn't by great through Winter, where a battery charged overnight could support those.

The same principle applies - if I had a cheap overnight rate I could program my diverter to “charge” the hot water cylinder overnight (using mains power rather than solar obviously!).

As a rule of thumb my 250L cylinder will easily accept 7 kWh most days, and the diverter cost about £300 I think.

[AW10]

Assuming you have gas CH... 7 kWh of gas costs about 28p (at 4p per kWh). You would need 300/0.28 = 1071 of those days where you had 7 kWh surplus electricity to just break even. If you can get paid via the SEG for your surplus then diverting it into the hot water cylinder is probably not cost effective.

I'm not saying don't do it; just suggesting to crunch the numbers first.

[NMNeil]

AW10 said:

Assuming you have gas CH... 7 kWh of gas costs about 28p (at 4p per kWh). You would need 300/0.28 = 1071 of those days where you had 7 kWh surplus electricity to just break even. If you can get paid via the SEG for your surplus then diverting it into the hot water cylinder is probably not cost effective.

I'm not saying don't do it; just suggesting to crunch the numbers first.

Difficult because the price of gas is subject to wild fluctuations. But I'm in 100% agreement about crunching the numbers first.
I calculated my system by getting my highest electricity usage for a month from my power bills, about 433Kwh for July, or 14Kwh per day
Then got the lowest amount of usable sunlight hours per month, which was roughly 6 hours during winter. I then arbitrarily dropped that to 5 hours to allow for the odd overcast day. This is usable daylight when the sun is actually on the panels.
So for that 5 hours I needed to generate 2.8Kwh each hour to run the house in mid summer with the A/C running flat out, then some more to charge the batteries for overnight use.
To give some overhead I got 24, 250 watt panels, which under laboratory conditions will give 6 Kw, but in the real world about 50 - 60% of that, or 3.5 Kw with about 1Kw left over to charge the batteries.
This was a worse case scenario calculation, which seems to have worked because we have had dust storms, clouds and the smoke from the Texas and Colorado wildfires for four days now, and first thing this morning my 38Kwh battery banks were down to about a 65% capacity, but then we had a few hours of sunshine and they are back to around 90% capacity.
Simply put, it works for me.

[Griffith4ever]

AW10 said:

Assuming you have gas CH... 7 kWh of gas costs about 28p (at 4p per kWh). You would need 300/0.28 = 1071 of those days where you had 7 kWh surplus electricity to just break even. If you can get paid via the SEG for your surplus then diverting it into the hot water cylinder is probably not cost effective.

I'm not saying don't do it; just suggesting to crunch the numbers first.

And all those numbers assumes you use the hot tank of water, completely, or in the majority, every day, else it's simply wasted diverted energy.

No way would our household of two use a tank, but different for a family of course.

I'm currently looking at grid tie inverters and panels for my workshop roof. I'm in there all day every day so they'd get well used. I'm also a solar panel dealer so get them trade.

[Griffith4ever]

NMNeil said:

I got 24, 250 watt panels, which under laboratory conditions will give 6 Kw, but in the real world about 50 - 60% of that, or 3.5 Kw with about 1Kw left over to charge the batteries.

FYI - assuming your panels are pointing at the right angle, you should get around 80% of rated wattage, but that's at midday summer, so your numbers are probably more realistic overall.

[Jambo85]

AW10 said:

Assuming you have gas CH... 7 kWh of gas costs about 28p (at 4p per kWh). You would need 300/0.28 = 1071 of those days where you had 7 kWh surplus electricity to just break even. If you can get paid via the SEG for your surplus then diverting it into the hot water cylinder is probably not cost effective.

I'm not saying don't do it; just suggesting to crunch the numbers first.

If any of this was cost effective I wouldn’t still be gainfully employed in the oil and gas industry

ETA - I’m on oil and my Eddi on my 3.6kWp east/west array has put an average of 1100kWh per year into my tank. That’s about 100L of oil, say £60. So 5 year pay back. The quickest paying back component of any PV installation I guarantee!

Edited by Jambo85 on Monday 21st March 19:13

[Jambo85]

Griffith4ever said:

And all those numbers assumes you use the hot tank of water, completely, or in the majority, every day, else it's simply wasted diverted energy.

No way would our household of two use a tank, but different for a family of course.

I'm currently looking at grid tie inverters and panels for my workshop roof. I'm in there all day every day so they'd get well used. I'm also a solar panel dealer so get them trade.

How is it wasted? Hot water tanks are pretty well insulated. Do you not run your boiler daily for hot water? Worst case the heat is lost to your house and there’s only a few weeks a year that a bit of warmth is truly unwelcome in this part of the world. Admittedly it is also when excess generation is highest!

Also as I said you can increase your hot water consumption and by putting a hot feed on your dishwasher.

If you’d rather have the 5p/kWh SEG and burn gas for your hot water because it’s 4p/kWh then crack on and bank the 1p/kWh, but if you’re doing any of this for financial gain you’re going to be disappointed!