Solar Panels UK - is it worth it?

[simmotech]

Somewhere on the internet will be a figure for annual production of kWh from Solar Thermal vs. PV and that might be significantly in Solar Thermal favour ... except for what happens when it is over producing in Summer.

A quick search found this quote on homebuilding.co.uk:-

"A solar thermal panel is around 80% efficient, compared to approximately 20% for solar PV"

And I saw the Viessman boiler thing in the garage - it was enormous and I think it had two expansion tanks hanging off it.
homebuilding.co.uk also mentioned that the storage cylinder is typically 200-350l.

So assuming its all working fine, its not worth changing just to fit 1 or 2 PV panels more on the roof.

With regard to over producing in Summary, well my wife & daughter both like baths - a lot - so I'll leave it to them to make sure the hot water doesn't get wasted.

 

[WannabeOwner]

quick search found this quote

"A solar thermal panel is around 80% efficient, compared to approximately 20% for solar PV"

Ah, sorry, I expressed myself badly. I meant the kWh generate per sq.m. of roof space - I think you might get more "return" from Solar Thermal than PV, assuming you can use the hot water ("my wife & daughter both like baths - a lot" - looks you are good to go on that one!)

First link from Google, so no idea if Good Data: solarthermalworld.org/news/solar-thermal-shows-highest-energy-yield-square-metre

Looks promising!

"The annual energy yield per square metre is much higher for solar collectors than for other renewable technologies, as the figure shows. Compared to PV, solar collectors produce, on average, three times as many kilowatt-hours. ... The chart shows end energy production and compares directly thermal and electric kilowatt-hours. The grey part of each bar marks the deviation in yield based on different estimates. The absolute values can be found in a table at the bottom of this article."

assuming its all working fine, its not worth changing just to fit 1 or 2 PV panels more on the roof.

I agree. May be a sweeping statement, but I reckon that for most people PV is "Produce X kWh of PV a year" and "reduce electricity bill by Y%". Every year. So that "saving" is locked in for the lifetime of the PV panels, provided that the household can use the PV (e.g. everyone not out at work Mon-Fri). If instead you generate "lots" of PV then you need the ability to store it - an EV which is at home Mon-Fri and/or PowerWall type static battery. A lot more cost ... corresponding more saving, over the lifetime of the kit, especially if electricity prices keep on rising

So could well be that the extra couple of PV panels just increases the overall percentage electricity saving - and getting hot water instead is same-same type of saving, or (from graph above) better. You also don't have to "Use" the Solar Thermal, unlike PV, because it is "stored".

And I saw the Viessman boiler thing in the garage - it was enormous and I think it had two expansion tanks hanging off it.

Yeah, I've got all that stuff too ... but mostly because I have a Biomass boiler. The boiler burns logs, not pellets, and has to burn a batch, start to finish, flat out, so has to have somewhere to store the excess heat. I have a 5,000L "Accumulator" tank (a pair of 2,500L) and large expansion vessels. That burn lasts 6 hours or so, the central heating is on during that time, and it also heats the tank from about 40C to 90C. Then if the house needs any heat it draws from the accumulator ... and when that starts to fall towards 40C (at which point its not really warm enough for radiators), I need to light the boiler again - maybe once a week Autumn/Spring and 2 or 3 times a week in Winter. The Solar thermal heats the domestic hot water tank first (dunno Litres, but its 6 or 7 feet tall and relatively thin, to stratify the water). It has a solar coil bottom to top, and also a coil for boiler (in Winter), and two immersions - top and bottom - we have the top one on timer for an hour before end of Off Peak in case the water is not hot for any reason so we have enough for "getting up", and the bottom immersion if we have a house full of people, or could be used to dump PV in summer.

After hot water tank heats up (a couple of hours in summer) the Solar Thermal then heats one of the accumulators. In Summer that gets up 60C, and the feed for hot water tank is pre-heated through that. The Accumulator has take-offs for the original house central heating (radiators), UFH in the new Passive House extension (which barely needs any heat, but given we already had a boiler that enables us to have it at a comfortable constant 21C all winter), and the pool. So I can use the boiler to heat the pool in early Spring / late Autumn (via Accumulator), and during Summer any excess Solar that raises the accumulator towards 60C I can "dump" into the pool.

probably should have always been this way.....efficient houses, and use less energy to start off with

Passive House consultant told me they had recently worked on a Thatched Cottage and got a 95% heating reduction ... but by comparison a bog standard Barrett Taylor Wimpey Thrown-Up new-build, could be improved by 75% :... and still that's all that Building Regs requires. Disappointing.

My advice, for anyone that can, go New Build and build a Passive House. Passive House spec adds less than 7% increase in build cost for a new-build, whereas retrofit is really really difficult. Then enjoy the fabulous comfort, air quality and huge benefit for respiratory diseases / infections (my wife and I haven't had a single winter cough / cold in the half dozen years we've had it, despite my wife working in an open plan office with people dying! around her all winter)

 

[ACarneiro]

Taylor Wimpey wouldn’t let me touch the house or make any changes during the build (even though I bought it off plan) so it will always have to be a retrofit even though it’s a new home.
Very frustrating.

 

[Avendit]

Taylor Wimpey wouldn’t let me touch the house or make any changes during the build (even though I bought it off plan) so it will always have to be a retrofit even though it’s a new home.
Very frustrating.

That's sad :-(. The only time I bought new was 20 years ago, and handing the builders a reel of cat5 and a crate of beer had the desired effect . Went through slightly more formal routes to delete some built in wardrobes to get a bigger second bedroom. But that was asking not to put some walls up, not fundamentally change their build process.

The big companies won't move till it's made a legal requirement unfortunately. It's coming but I bet the industry fights it all the way, it will need a Tesla of the building world to show it can be done better in every way before they all wither and die.

Have you seen Energiesprong explained – Energiesprong Blew my mind.

 

[WannabeOwner]

it will need a Tesla of the building world to show it can be done

I'd be up for that. Not sure at what point one becomes a High Nett Worth individual, but I'm not there yet - sorry!

Have you seen Energiesprong explained – Energiesprong Blew my mind.

Not come across that, and only had a quick look, but my (very Passive Haus jaundiced) view is that Net Zero energy in itself is not the answer but needs the whole PHPP calculation to get a good balance in the building.

For me Passive House is about both negligible heat input (i.e. good insulation) but also comfort - no overheating in Summer, and no convection-draughts in winter.

For example, the inside surface of the window glass should [be designed to] not be more than 4C colder than room temperature - because if the difference is greater the air will "fall" under convection, and that will create a draught (even if the house is hermetically sealed), and you lose the comfort aspect and/or turn the thermostat up because you feel "cold" (which exacerbates the problem of course )

Same with roof glass - e.g. Velux. That can be done, definitely, but in general terms Passive Haus shades South facing windows with roof overhangs - so high-sun-angle in Summer misses the windows, but low Sun in winter comes straight through. Roof glass is likely a heating element in Summer and a cooling one in Winter. - and the falling air is uncomfortable.

Passive House consultant talked us out of roof glass (Architect said room would be plenty light enough without - he was right, we were sat on the fence). Glad he did. Also a complicated Hips / Dormer thingie which Architect said was his best feature! Passive Haus bloke said the insulation impact was diabolical ... we ditched that, probably saved us a fortune on the construction! - we put a stone triangular pediment up there instead - has exactly the same "impact" that the architect wanted with his triangular dormer window

The air tightness is the other important thing. My understanding is that housing estates from the likes of Barrett Taylor Wimpey only have to air-test one house. In our test one bedroom had a massive leak - builder foreman took a look and said "Twits [or something like that!] have missed the seal". I doubt we would have ever known ... just been uncomfortable.

If the house is totally (so to speak) air tight all the exhaust air goes out through the ventilation system, and is used for "heat recovery", so maximum efficiency of heat preservation. And any air leakage implies draughts (and thus reduction of "comfort"). Plus the benefit of pollen filters in the ventilation, no flies / dust coming in through open windows and so on. We do open windows it we want to, but not when baking hot outside (lets the heat in, Natch) nor if freezing cold (let's the cold in Natch)

So glad we did it

 

[Avendit]

I'd be up for that. Not sure at what point one becomes a High Nett Worth individual, but I'm not there yet - sorry!



Not come across that, and only had a quick look, but my (very Passive Haus jaundiced) view is that Net Zero energy in itself is not the answer but needs the whole PHPP calculation to get a good balance in the building.

For me Passive House is about both negligible heat input (i.e. good insulation) but also comfort - no overheating in Summer, and no convection-draughts in winter.

For example, the inside surface of the window glass should [be designed to] not be more than 4C colder than room temperature - because if the difference is greater the air will "fall" under convection, and that will create a draught (even if the house is hermetically sealed), and you lose the comfort aspect and/or turn the thermostat up because you feel "cold" (which exacerbates the problem of course )

Same with roof glass - e.g. Velux. That can be done, definitely, but in general terms Passive Haus shades South facing windows with roof overhangs - so high-sun-angle in Summer misses the windows, but low Sun in winter comes straight through. Roof glass is likely a heating element in Summer and a cooling one in Winter. - and the falling air is uncomfortable.

Passive House consultant talked us out of roof glass (Architect said room would be plenty light enough without - he was right, we were sat on the fence). Glad he did. Also a complicated Hips / Dormer thingie which Architect said was his best feature! Passive Haus bloke said the insulation impact was diabolical ... we ditched that, probably saved us a fortune on the construction! - we put a stone triangular pediment up there instead - has exactly the same "impact" that the architect wanted with his triangular dormer window

The air tightness is the other important thing. My understanding is that housing estates from the likes of Barrett Taylor Wimpey only have to air-test one house. In our test one bedroom had a massive leak - builder foreman took a look and said "Twits [or something like that!] have missed the seal". I doubt we would have ever known ... just been uncomfortable.

If the house is totally (so to speak) air tight all the exhaust air goes out through the ventilation system, and is used for "heat recovery", so maximum efficiency of heat preservation. And any air leakage implies draughts (and thus reduction of "comfort"). Plus the benefit of pollen filters in the ventilation, no flies / dust coming in through open windows and so on. We do open windows it we want to, but not when baking hot outside (lets the heat in, Natch) nor if freezing cold (let's the cold in Natch)

So glad we did it

It's more in the industrialization of retrofit that I was impressed with, the thinking at scale and optimisation of the overall system. Proper passive is always the aim, but lacking that opportunity for most of the housing stock just wrapping the whole house in a tea cosy seems a great idea, and I like that residents can pay for it out of the savings from doing it.

I also dream that there is a similar opportunity for a solar installer - don't mess around with a single house, do an entire street of similarly designed houses at once with teams of installers working the street for a week or 2. Guessing the DNO may poopoo that for anything other than the smallest install per property tho .

 

[RedMod3]

Am surprised more people on here aren't the same. Its only this month our gas bill is less than our electricity bill, the price cap increase is really noticeable.

Come this winter our gas bill is going to be as high as £28 PER day.

Going to a heat pump etc wouldn't help either, as we know how useless solar PV is in winter. We already have a 4KW solar PV panel, and a PW that charges off peak. But on days in the winter when we use alot of electricity, the cost is very noticeable. If we had no gas heating, our total electricity bill would £20+ per day quite easily.

Unless you are on the 15p/5p Octopus traiff and have no gas heating, this winter we are all in the same situation......though in an desperate attempt to distract the government looks like they finally might do the right thing and give some meaningful help to house holds!

With no PW at that time, we spent £7.16 on electricity (no gas here) on Christmas day, but by this coming Christmas with 3 PWs, our cost, will be £3.10 assuming the same usage. I'm curious, why is the cost so high>

 

[WannabeOwner]

just wrapping the whole house in a tea cosy seems a great idea

I agree (and so long as the brick isn't "precious", that's much easier than insulating internally - plus you get the benefit of having the thermal mass inside the insulation, so rarely any fluctuation on temperature, and it would take a week, or more, for a heatwave to have a significant impact.

similar opportunity for a solar installer - don't mess around with a single house, do an entire street of similarly designed houses at once with teams of installers working the street for a week or 2. Guessing the DNO may poopoo that

Maybe the answer would be to link them all into a local grid, connected to a centralised mega-battery, and then connect that to the grid? Pretty sure I've read of some communities that have done that

 

[WannabeOwner]

Found one, but its behind PayWall ... but I can't find other media info. about it

How to turn your street into a solar power station

The villages around Stroud, scattered across the west Gloucestershire landscape of deep green valleys and hump-back hills, have long attracted city dwellers ye

www.thetimes.co.uk

 

[Peter 224]

This is a bright sunny day Monday 23rd.
We have a Intelligent Octopus tarif, PV panel since November 2011 a rather pointless 3kWh Pythontech battery and a Tesla M3 Dual Motor.
The graph shows the car charging, then a blip from the toaster, followed by no Electricity used from the grid, then at about 7 when SWMBO prepares supper and the little battery is exhausted we buy power again...

What I need is about 20kw battery storage to take us almost off grid during the peak hours, buying at 7.5p/kWh and harvesting the sun.

 

[Mrklaw]

Maybe the answer would be to link them all into a local grid, connected to a centralised mega-battery, and then connect that to the grid? Pretty sure I've read of some communities that have done that

I was wondering about this when looking at EV Puzzle having such large export he can’t use it even with battery and car charging. Small community setups might work well

 

[PITA]

This is a bright sunny day Monday 23rd.
We have a Intelligent Octopus tarif, PV panel since November 2011 a rather pointless 3kWh Pythontech battery and a Tesla M3 Dual Motor.
The graph shows the car charging, then a blip from the toaster, followed by no Electricity used from the grid, then at about 7 when SWMBO prepares supper and the little battery is exhausted we buy power again...

View attachment 809747

What I need is about 20kw battery storage to take us almost off grid during the peak hours, buying at 7.5p/kWh and harvesting the sun.

2 x Powerwalls... that'll give you 27 kWh storage (and an ideal buffer for Winter Blackouts)

 

[RedMod3]

2 x Powerwalls... that'll give you 27 kWh storage (and an ideal buffer for Winter Blackouts)

Or 3 x Powerwalls as you'll use more electricity in winter, and you'll need greater protection from winter blackouts.

 

[PITA]

Or 3 x Powerwalls as you'll use more electricity in winter, and you'll need greater protection from winter blackouts.

Haha... indeed, perfect for the Gold Level Standard

1 x Bronze 13 kWh
2 x Silver 27 kWh
3 x Gold 40 kWh
4 x Platinum 54 kWh
5+ Diamond

 

[exlatccatsa]

This is a bright sunny day Monday 23rd.
We have a Intelligent Octopus tarif, PV panel since November 2011 a rather pointless 3kWh Pythontech battery and a Tesla M3 Dual Motor.
The graph shows the car charging, then a blip from the toaster, followed by no Electricity used from the grid, then at about 7 when SWMBO prepares supper and the little battery is exhausted we buy power again...

View attachment 809747

What I need is about 20kw battery storage to take us almost off grid during the peak hours, buying at 7.5p/kWh and harvesting the sun.

If you already have a Pylontech battery it should be easy to add to as all the US series are compatible. 3 x 4.8 about £3900 or 4 x3.5 kWh £4800 from ITStechnologies and you can follow the youtube videos to add the new batteries yourself or get an electrician to add and save the VAT.
And of course you don't have to buy them all at once.

 

[Peter 224]

If you already have a Pylontech battery it should be easy to add to as all the US series are compatible. 3 x 4.8 about £3900 or 4 x3.5 kWh £4800 from ITStechnologies and you can follow the youtube videos to add the new batteries yourself or get an electrician to add and save the VAT.
And of course you don't have to buy them all at once.

Thanks for the advice, I think that the addition of additional batteries should make sense.

 

[RedMod3]

Haha... indeed, perfect for the Gold Level Standard

1 x Bronze 13 kWh
2 x Silver 27 kWh
3 x Gold 40 kWh
4 x Platinum 54 kWh
5+ Diamond

With the threat of power cuts this winter, achieving the Silver or Gold standard makes sense if we are to avoid loss of power.

Energy crisis deepens as six million UK households now face BLACKOUTS

THE UK has been sent a dire warning as Russia's invasion of Ukraine could plunge six million households in Britain into blackout this winter.

www.express.co.uk

 

[PITA]

With the threat of power cuts this winter, achieving the Silver or Gold standard makes sense if we are to avoid loss of power.

Energy crisis deepens as six million UK households now face BLACKOUTS

THE UK has been sent a dire warning as Russia's invasion of Ukraine could plunge six million households in Britain into blackout this winter.

www.express.co.uk

Yeah, get some blackout blinds fitted as well, or you'll become your street's 'most hated'

 

[Avendit]

Talking of needing blinds, Puredrive have updated the specs on their batteries and now include "Protects against power cuts – seamless change over within 20ms". What is lacking is any detail about how this works. I've tried registering as a supplier to get installation notes etc, but they are all the same old version So.energy sent me a few months ago about setting up a manual switchover for a few circuits.

NEW - PURESTORAGE AC BATTERY - Puredrive Energy

Any ideas for where/how to get more info?

 

[simmotech]

Has anyone used the designer at SunnyDesignWeb?

I found it useful to prove that rather than use the 8 x 390W panels I was quoted for, I could, in theory, bump up the max kWp for my roof by ~20% by squeezing in 4 x 545W and 4 x 405W panels.

It let me create 2 zones and identify the obstacles - roof windows and the dormer in 2D or 3D and with/without the map behind.
This is a lot easier than printing out the 2D roof map from the quote and then manually using a ruler to see what bigger panels would fit!
It also seems to take into account the shading for the obstacles so that should help calculate a more accurate yield.

The rest of the designer does have some limitations for amateur tinkering about with:
- only has their own inverters etc. included (which is fair enough)
- has EUR for the costs (this can be changed but not to GBP!) but I don't suppose it matters

But it does try to help with Design Suggestions such as for the inverter(s):-

Though I'm too thick to understand fully what it is suggesting yet - still working on it.