Solar Panels UK - is it worth it?

[Pete UK]

I get that the waste water can pre-heat the cold feed.

How does that reduce hot water consumption?

Basically, you’re saving heating up the stone cold tap input to the tepid temperature. So you need less hot tap flow.

Same as if you lived in the Sahara and your cold tap was already outputting 50c you’d be saving heating all of your hot water, cos you wouldn’t be using any of it !

 

[WannabeOwner]

you’re saving heating up the stone cold tap input to the tepid temperature.

So you have to route the "captured heat" from the bathroom back to the cold incoming main?

If so that makes sense, but I thought this was just local within the bathroom.

I have accumulator tank, heated from Solar Thermal, that pre-heats incoming main before it goes into hot water tank - so less heating required to bring that up to DHW temperature (and solar heats the DHW tank too, as a priority before Accumulator) just means that the make-up water from mains is at a tepid (or even "hot") temperature, so less stratification in the DHW tank.

 

[Mrklaw]

So you have to route the "captured heat" from the bathroom back to the cold incoming main?

If so that makes sense, but I thought this was just local within the bathroom.

I have accumulator tank, heated from Solar Thermal, that pre-heats incoming main before it goes into hot water tank - so less heating required to bring that up to DHW temperature (and solar heats the DHW tank too, as a priority before Accumulator) just means that the make-up water from mains is at a tepid (or even "hot") temperature, so less stratification in the DHW tank.

sounds like their install is local only for that shower. So the cold feed is warmed by it, so the thermostatic mixer on the shower would turn down the hot feed accordingly - reducing the demand on hot water and reducing energy use (either less to heat back up in the tank or pulling less from teh combi so its running lower)

 

[WannabeOwner]

so the thermostatic mixer on the shower would turn down the hot feed accordingly

Thanks, the penny has now dropped. I already described it above, just didn't spot the significance.

DHW supply is, say, 65C and I want to shower at 55C and I need X litres per minute.

If I use stone cold water to reduce 65C to 55C I need very little cold. So it doesn't contribute much to the flow - so most of the flow is from the hot supply

If I use tepid (from recovered heat) water to reduce 65C to 55C I need quite a lot. So the amount of actual hot water I use is significantly reduced.

Obvious now, and no doubt was to everyone else, but I've shown my working in case not. Q.E.D.

 

[Avendit]

Thanks, the penny has now dropped. I already described it above, just didn't spot the significance.

DHW supply is, say, 65C and I want to shower at 55C and I need X litres per minute.

If I use stone cold water to reduce 65C to 55C I need very little cold. So it doesn't contribute much to the flow - so most of the flow is from the hot supply

If I use tepid (from recovered heat) water to reduce 65C to 55C I need quite a lot. So the amount of actual hot water I use is significantly reduced.

Obvious now, and no doubt was to everyone else, but I've shown my working in case not. Q.E.D.

spot on. Except if you are showering in 55C water you may find you are cooking yourself. Normal is ~40.

If you are wondering where the magic extra energy is coming from - the water going into the drains from the out end of the reclaimer is now cold rather than ~30C. Grab as much of that energy as you can since you paid for it.

The more efficient installs, that need architecting into a build, are vertical between floors rather than horizontal, and plumb into the input of your hot tank (or combi). Much like your solar pre-heater.

 

[Pete UK]

so my house fuse tripped and I switched back on, but my old PV fuse in the CU has tripped. Tried turning it back on and it tripped the house again.

installers swear they havne’t turned anything on, not been near the old panels, nothing is wired in. Just the weirdest coincidence?

Not even sure how it gets maintained as its a leased system. Sods law if my old array breaks just as my new one gets put in

edit: possibly the installers may have nudged the old wire - the original installers (10 years ago) apparantly just slung it over the roof and then through a soffit somewhere to get down to the meter cupboard so I suppose I should be surprised its lasted this long!

How’d the install go?

Pleased with your new system?

 

[Mrklaw]

How’d the install go?

Pleased with your new system?

scaffolding still up (wife not pleased) but most seems done. Still some niggles with the setup of the battery but otherwise pretty good - the solar is nice to have that bit extra so instead of scraping 2kw I’m getting 3.5. Even better when its not high generation - where I might be only getting 200w I’ll now get 500w so easily covering base load.

4kw north is only about 50% more power than the 2.6kwh south so I expected slightly less output due to the aspetc. When the sun is bright that seems about right with generation. But when its overcast and generation is low, the north one seems pretty darned good and sometimes outperforming the south array - guess there is ‘global’ lllumination indirectly when its overcast that mitigates the direct angle being less good?

battery works ‘roughly - it handled the tumble dryer this morning and the house load last night too.

 

[WannabeOwner]

4kw north is only about 50% more power than the 2.6kwh south

I'd be interested, if you are able to get some numbers, for when the South stops generating in evening does the North go on for longer? how much longer?

And does the North start earlier, than the South, in the morning?

My working hypothesis, untested!, is that the North will be able to see the sun, particularly in mid-Summer, before the South can - and in evening will be able to see the sun longer. if this is the case it reduces the duration of the "solar night", and the time that the house would have to survive on batteries (to avoid grid-import). An East-West roof would be ideal, of course, but for something with South-North roof I think this may be an additional/potential benefit from the North

At 51.5 degrees north, on June 21st, sunrise is pretty much North East, and sunset is North West.

 

[Pete UK]

scaffolding still up (wife not pleased) but most seems done. Still some niggles with the setup of the battery but otherwise pretty good - the solar is nice to have that bit extra so instead of scraping 2kw I’m getting 3.5. Even better when its not high generation - where I might be only getting 200w I’ll now get 500w so easily covering base load.

4kw north is only about 50% more power than the 2.6kwh south so I expected slightly less output due to the aspetc. When the sun is bright that seems about right with generation. But when its overcast and generation is low, the north one seems pretty darned good and sometimes outperforming the south array - guess there is ‘global’ lllumination indirectly when its overcast that mitigates the direct angle being less good?

battery works ‘roughly - it handled the tumble dryer this morning and the house load last night too.

Ah-ha, that sounds like it’s working more or less as expected then and providing a very useful contribution

If you can cover the base load in non optimal sun that makes a big difference wrt holding the existing battery charge for longer. Pretty impressive.

What inverter/ battery/ size battery did you get again? - The thread is too long now to scroll back !

My S/N should be getting about 80-85% of what you’ve got there. Almost in the exact same ratio N:S. 8:5 N:S for me. I think I should be able to see the 4 individual string’s production, when installed, in the GivEnergy portal, which would be great. (N&S plus the 2 East strings)

Good luck ironing out the niggles with the battery.

 

[Mrklaw]

South is 2.6 array not sure on inverter

North is 4kw array 3kw inverter

Battery is ac coupled givenergy - ac-3.0 inverter and 9.5kwh battery (should be 9.5 usable)

 

[Aggs18]

Any recommendations for an installer, solar and battery in the Ashbourne area near to Derby?

 

[Rooster6655]

Any recommendations for an installer, solar and battery in the Ashbourne area near to Derby?

Can't recommend any but avoid First4Solar and daylight Energy recently featured on TV, many people paid and no install, F4S trust pilot went from one of the highest rated to 40/40 and now 6 pages of recent negative reviews, quite worrying that these companies can just go bad in a short space of time.

 

[ringi]

All it takes is a company losing a key member of staff while having to continue to pay the other staff.

 

[Mrklaw]

I'd be interested, if you are able to get some numbers, for when the South stops generating in evening does the North go on for longer? how much longer?

And does the North start earlier, than the South, in the morning?

My working hypothesis, untested!, is that the North will be able to see the sun, particularly in mid-Summer, before the South can - and in evening will be able to see the sun longer. if this is the case it reduces the duration of the "solar night", and the time that the house would have to survive on batteries (to avoid grid-import). An East-West roof would be ideal, of course, but for something with South-North roof I think this may be an additional/potential benefit from the North

At 51.5 degrees north, on June 21st, sunrise is pretty much North East, and sunset is North West.

still early and remind me in June/July to test a few days in a row - but yesterday the south did seem to ramp down sharper than the north. Both were still hanging on at 7pm - south doing 150w, north doing 215w. At 7:30 the north was still doing 110w but the south had stopped by then (just). the North finished at 8pm. So even in early May I’m getting that little extra stretch from north panels

 

[Chemist]

Any recommendations for an installer, solar and battery in the Ashbourne area near to Derby?

Solar Star Power. They are based in Uttoxeter.

 

[94jdh]

Can't recommend any but avoid First4Solar and daylight Energy recently featured on TV, many people paid and no install, F4S trust pilot went from one of the highest rated to 40/40 and now 6 pages of recent negative reviews, quite worrying that these companies can just go bad in a short space of time.

First4solar made a NOI1 application on 4th May to appoint an administrator.

 

[ringi]

At 7:30 the north was still doing 110w but the south had stopped by then (just). the North finished at 8pm. So even in early May I’m getting that little extra stretch from north panels

It also depends in how good the two different inverters are at coping with low input voltages.

 

[ACarneiro]

Solar Star Power. They are based in Uttoxeter.

They installed my system and two more Powerwalls about 2 years later.
Wholeheartedly recommend them as well if they’ll cover your area.

 

[Aggs18]

Solar Star Power. They are based in Uttoxeter.

They installed my system and two more Powerwalls about 2 years later.
Wholeheartedly recommend them as well if they’ll cover your area.

Thanks both for the recommendation.

 

[Mrklaw]

It also depends in how good the two different inverters are at coping with low input voltages.

interesting. My north obviously newer, is a fox ESS 3kw inverter. My south is a sunnyboy ancient thing