Solar Panels?

Author
Discussion

loskie

5,144 posts

119 months

Saturday 24th September 2022
quotequote all
Tobermory.
Not sure where you are in the country.
Mull maybe?

I'm in SW Scotland have a 3.6kw array facing sse.
Installed in 2010 so not the latest tech but decent components and inverter. Array split into two lines going into the inverter.

Peak output I've seen 26 kw in a day. Depths of winter on a miserable day as little as 1kw/day.

I think on average I've had 3100 units per year since installation.

Arnold Cunningham

3,758 posts

252 months

Saturday 24th September 2022
quotequote all
TDK-C60 said:
Have you looked at your expected usage on an hour by hour basis and how a battery supports that? It is worth doing.

I think our optimal set up will be an approach with 8-10kW solar, using the low tariffs for ~4hours in winter and assigning some high demand activities to that period also, as well as topping up the battery.

If you look at big uses like washers and possibly immersion - this can be done during that 4 hour period - in winter there is no point charging the battery from grid and back out of the battery (remember 5-10% conversion losses) for those uses - just take it direct. Overall you might conclude the battery size you need is not as big as expected. I was originally wondering if 20kW of batteries might be useful, but now thinking 10kW is plenty - at least until I might decide to fully bin gas and go all electric with heat pump - then more batteries might be a consideration. But lots of other house changes needed before then.

This balance also applies to EV charge periods. In winter - use cheap grid, in summer let the PV do what it can. I'd expect PV to easily cover 3/7 days commute in summer. The batteries can really help in some circumstances, but the more you model it the more it seems maybe 6-8kW of battery is plenty "bridging" needed for a typical house.

I'm still doing the sums but breaking use down hourly for winter and summer scenarios is definitely worth plotting out as it changed my view - and look at moving your high energy demands around.

Also worth looking at things like smart immersion when considering overall energy - cut power to only heat to 40deg 15 days only use 60deg for legionella twice a month. The energy savings from this alone could be considerable - cut from e.g. 5300kW per year to 2800kW - and if tank / pipes well insulated much of that power can be taken during 7p rate. (This is going from a 7kW day demand to 3.6kW of 14 days lower demand).

Elec - water heating (annual)
35p - 5300kW is £2800 - baseline - no point - stick to gas
35p - 2800kW is £930 - ignoring >50% could be PV via battery
7p - 2800kW is £261 - ignoring >50% could be PV via battery

The daily amount of3.6kW for low heat days (7kW for kill legionella day) - PV can cover much of that for much of the year - hence reducing grid use/costs
Thank you for the well thought out post.

Have looked at the numbers properly. Since 26th August (last time I turned the pool on), we average 10.3 kWh per day. If we shift the washing machine and dishwasher to run off peak (washing machine is daily, dishwasher is probably every other day), then we're just about under the capacity of the 9.5 battery. So looks like a single 9.5 may be just about OK through the winter. And in the summer, just fine.



Edited by Arnold Cunningham on Saturday 24th September 21:14

cavey76

419 posts

145 months

Saturday 24th September 2022
quotequote all
Off of the back of a conversation with some friends who live in the @rse end of nowhere and the figures and rational posted here(thanks all) I am now giving this serious consideration.

Question is:

My house is almost directly south facing which is good. What are local authorities like if you cover the front of your roof in solar panels to save the dolphins?

Am I likely to face resistance?

NMNeil

5,860 posts

49 months

Saturday 24th September 2022
quotequote all
cavey76 said:
Off of the back of a conversation with some friends who live in the @rse end of nowhere and the figures and rational posted here(thanks all) I am now giving this serious consideration.

Question is:

My house is almost directly south facing which is good. What are local authorities like if you cover the front of your roof in solar panels to save the dolphins?

Am I likely to face resistance?
Looks like they won't be a problem, but best check first as it's an oldish article and things change.
https://www.agendani.com/attwood-ends-planning-res...

AW10

4,422 posts

248 months

Sunday 25th September 2022
quotequote all
cavey76 said:
Off of the back of a conversation with some friends who live in the @rse end of nowhere and the figures and rational posted here(thanks all) I am now giving this serious consideration.

Question is:

My house is almost directly south facing which is good. What are local authorities like if you cover the front of your roof in solar panels to save the dolphins?

Am I likely to face resistance?
Unless you live in a conservation area, listed building or national park the answer is pretty much no.

Evanivitch

19,807 posts

121 months

Sunday 25th September 2022
quotequote all
cavey76 said:
Off of the back of a conversation with some friends who live in the @rse end of nowhere and the figures and rational posted here(thanks all) I am now giving this serious consideration.

Question is:

My house is almost directly south facing which is good. What are local authorities like if you cover the front of your roof in solar panels to save the dolphins?

Am I likely to face resistance?
https://www.legislation.gov.uk/uksi/2015/596/schedule/2/part/14/made

anonymous-user

53 months

Monday 26th September 2022
quotequote all
I got my quotes where are £12,115 for a 5.53kW system with a 5.2kWh battery or £14,615 with a 10.4 kWh battery.

The prediction based on the direction of my roof and shading calculations etc are to generate 4300kWh of useable energy per year and break even in 7 years based on the 36p price (obviously longer if prices fall, but I suspect they will remain capped for a while until he Government gets their subsidy back?)

In summer at least this should cover pretty much our entire electricity usage, while obviously not in winter where I would expect it to provide maybe 25%.
The larger battery might not be necessary, especially as I am getting an EV soon that could use some of the daytime juice, but I'm inclined to go for it anyway to provide a bigger buffer.

That's pretty attractive to me, as I said it't not just the economics, I would like the idea that the 'waste' sunlight falling on our roof is being used instead of burning dinosaurs.

There's the option of a solar iBoost to divert excess electricity to the immersion heater, but that's another £500. My gut feeling is that with the bigger battery this won't actually add anything. Does anyone have experience of using these?

Thank you


Arnold Cunningham

3,758 posts

252 months

Monday 26th September 2022
quotequote all
I'm still procastinating about that 2nd battery, having now worked out that when I spend a day in the garage, we go from 10 to over 16 kWh. Or I can spend the money on a roamerdrive for the landy.

Anyway - on immersion heaters - I was also wondering if a normal wifi switch such as this could be used : https://www.screwfix.com/p/tcp-1-gang-1-way-smart-...

It's a 3kW heater and the switch is rated to 13A.

Edited by Arnold Cunningham on Monday 26th September 15:20


Edited by Arnold Cunningham on Monday 26th September 16:02

anonymous-user

53 months

Monday 26th September 2022
quotequote all
Arnold Cunningham said:
I'm still procastinating about that 2nd battery, having now worked out that when I spend a day in the garage, we go from 10 to over 16 kWh.

Anyway - on immersion heaters - I was also wondering if a normal wifi switch such as this could be used : https://www.screwfix.com/p/tcp-1-gang-1-way-smart-...

It's a 3kW heater and the switch is rated to 13A.

Edited by Arnold Cunningham on Monday 26th September 15:20
Yes, I wondered that, the problem is that you want it on when and only when you are making excess electricity, i.e. during the day. If it turns on while it is cloudy you could end up importing electricity which is the opposite of what you want. I suppose you could fit a smart switch to it and use some sort of home kit automation based on a sunlight sensor (or even a ITTT routine based on the weather forecast?) to turn it on and off, that might work, but a bit complicated.

My wifi plugs are 13A, but is that enough for a 3kW immersion heater?

Edited by anonymous-user on Monday 26th September 15:37

OutInTheShed

7,369 posts

25 months

Monday 26th September 2022
quotequote all
Tobermory said:
I got my quotes where are £12,115 for a 5.53kW system with a 5.2kWh battery or £14,615 with a 10.4 kWh battery.

The prediction based on the direction of my roof and shading calculations etc are to generate 4300kWh of useable energy per year and break even in 7 years based on the 36p price (obviously longer if prices fall, but I suspect they will remain capped for a while until he Government gets their subsidy back?)

In summer at least this should cover pretty much our entire electricity usage, while obviously not in winter where I would expect it to provide maybe 25%.
The larger battery might not be necessary, especially as I am getting an EV soon that could use some of the daytime juice, but I'm inclined to go for it anyway to provide a bigger buffer.

That's pretty attractive to me, as I said it't not just the economics, I would like the idea that the 'waste' sunlight falling on our roof is being used instead of burning dinosaurs.

There's the option of a solar iBoost to divert excess electricity to the immersion heater, but that's another £500. My gut feeling is that with the bigger battery this won't actually add anything. Does anyone have experience of using these?

Thank you
I know several people who've got iBoost type devices, not aware of anyone with a battery as well though.
I would imagine the battery would reduce the gain of the iBoost quite a lot, how much does your hot water cost you per day, and how many days would the iBoost make a big dent in that? How would it be controlled? I imagine you'd prioritise charging the battery.

Your seven year payback is based on zero export?

Coincidentally, my mate's system generates about 4300kWh in a typical year (albeit from a small system in a sunnier place).
His good days are over 20kWh.
So in Summer, you will be exporting a big chunk every good day, unless you have some big daytime load (a still presumably?)
Obviously a car could use some of that, if your car use is a regular 40 miles a day (night!) or something?

Or is your 'useful' generation after exporting half of what you produce in the good months?

Arnold Cunningham

3,758 posts

252 months

Monday 26th September 2022
quotequote all
Tobermory said:
Yes, I wondered that, the problem is that you want it on when and only when you are making excess electricity, i.e. during the day. If it turns on while it is cloudy you could end up importing electricity which is the opposite of what you want. I suppose you could fit a smart switch to it and use some sort of home kit automation based on a sunlight sensor (or even a ITTT routine based on the weather forecast?) to turn it on and off, that might work, but a bit complicated.

My wifi plugs are 13A, but is that enough for a 3kW immersion heater?
The plug I linked to has a rest API (IIRC) and integrates with various other products - so the thinking was that it it then switches on via your home automation when you're generating excess energy via the panels.

13A is just enough to run a 3kW resistive load like a heater, I think. P=IV etc.
Otherwise I've spotted a wifi robo button presser - so it can turn a conventional switch on an off.

anonymous-user

53 months

Monday 26th September 2022
quotequote all
Arnold Cunningham said:
Tobermory said:
13A is just enough to run a 3kW resistive load like a heater, I think. P=IV etc.
Otherwise I've spotted a wifi robo button presser - so it can turn a conventional switch on an off.
I’d love the link for that, it appeals to the Wallace and Grommit in me smile

anonymous-user

53 months

Monday 26th September 2022
quotequote all
OutInTheShed said:
I know several people who've got iBoost type devices, not aware of anyone with a battery as well though.
I would imagine the battery would reduce the gain of the iBoost quite a lot, how much does your hot water cost you per day, and how many days would the iBoost make a big dent in that? How would it be controlled? I imagine you'd prioritise charging the battery.

Your seven year payback is based on zero export?

Coincidentally, my mate's system generates about 4300kWh in a typical year (albeit from a small system in a sunnier place).
His good days are over 20kWh.
So in Summer, you will be exporting a big chunk every good day, unless you have some big daytime load (a still presumably?)
Obviously a car could use some of that, if your car use is a regular 40 miles a day (night!) or something?

Or is your 'useful' generation after exporting half of what you produce in the good months?
Yes that’s without allowing for exporting anything

We currently use gas for water heating so the plan would be to use electricity (probably mostly from the battery) to heat water in the summer and not use the boiler at all.

Otherwise the batteries would charge during day and provide the power for cooking and the washing machine which goes on pretty much every school day in the evening plus lights TV etc at night.

Also on other days I guess you would check the battery charge before turning on the boiler in the evening and if you have more charge than you normally need for lights etc turn on the immersion instead of the boiler. It would be really nice to have a sort of NEST style learning device that could automate those parts of decisions, I imagine that will come in time.

Again in the summer it would probably make sense to plug an EV in on days when I’m home during the day as it is clearly better to use electricity directly rather than storing it first if you can.

There’s so many variables you can tie yourself in knots but I’m sure overall it makes sense.

Arnold Cunningham

3,758 posts

252 months

Monday 26th September 2022
quotequote all
Tobermory said:
I’d love the link for that, it appeals to the Wallace and Grommit in me smile

Arnold Cunningham

3,758 posts

252 months

Monday 26th September 2022
quotequote all
Tobermory said:
It would be really nice to have a sort of NEST style learning device that could automate those parts of decisions, I imagine that will come in time.
Is there one already? I have lots of ideas and have already taken a look at the interfaces many of the products offer. I've written some pretty decent commercially available process engines before (if I do say so myself) and this isn't much of a stretch beyond that.

I was also thinking you want it to learnt to correlate the weather forecast with how much energy you generate, vs how much you have in store and how much you need. So it'll automatically charge more from the grid cheap period if it knows tomorrow's weather it poor and you'r unlikely to generate enough power to see you through.

anonymous-user

53 months

Monday 26th September 2022
quotequote all
Arnold Cunningham said:
Tobermory said:
It would be really nice to have a sort of NEST style learning device that could automate those parts of decisions, I imagine that will come in time.
Is there one already? I have lots of ideas and have already taken a look at the interfaces many of the products offer. I've written some pretty decent commercially available process engines before (if I do say so myself) and this isn't much of a stretch beyond that.

I was also thinking you want it to learnt to correlate the weather forecast with how much energy you generate, vs how much you have in store and how much you need. So it'll automatically charge more from the grid cheap period if it knows tomorrow's weather it poor and you'r unlikely to generate enough power to see you through.
Yes that sort of thing.

Inputs would be your predicted (and historical) electricity use during the day and night, the weather forecast, elec and gas unit prices, the current charge in your battery, and outputs would be control of your immersion, export to the grid and ‘export’ to your own battery and possibly also EV together with the EV charge and your historical mileage use of the EV.

All of this could then decide on the best options for yo ur system.

The key is it would have to be as close as possible to being invisible to the user (unless you wanted to delve in to a settings app).

I’ve learned from my forays into smart switches etc that almost no level of added complexity is acceptable to the non tech savvy members of the household wink

Arnold Cunningham

3,758 posts

252 months

Monday 26th September 2022
quotequote all
I hear you.

AW10

4,422 posts

248 months

Monday 26th September 2022
quotequote all
Tobermory said:
I got my quotes where are £12,115 for a 5.53kW system with a 5.2kWh battery or £14,615 with a 10.4 kWh battery.

The prediction based on the direction of my roof and shading calculations etc are to generate 4300kWh of useable energy per year and break even in 7 years based on the 36p price (obviously longer if prices fall, but I suspect they will remain capped for a while until he Government gets their subsidy back?)

In summer at least this should cover pretty much our entire electricity usage, while obviously not in winter where I would expect it to provide maybe 25%.
The larger battery might not be necessary, especially as I am getting an EV soon that could use some of the daytime juice, but I'm inclined to go for it anyway to provide a bigger buffer.

That's pretty attractive to me, as I said it't not just the economics, I would like the idea that the 'waste' sunlight falling on our roof is being used instead of burning dinosaurs.

There's the option of a solar iBoost to divert excess electricity to the immersion heater, but that's another £500. My gut feeling is that with the bigger battery this won't actually add anything. Does anyone have experience of using these?

Thank you
What is your current annual electricity use?
How much are they predicting you can use directly from the panels?
How much are they predicting you will divert to the battery and then use later?

I suspect your payback estimate is unrealistically optimistic.

PCoulson

62 posts

85 months

Monday 26th September 2022
quotequote all
No being a powerfully built company director (overweight local government officer) I don't have the funds for a proper system but what are peoples thoughts on https://www.pluginsolar.co.uk/?product_cat=plug-in...

Reading up it seems there much contradictory info on how diy-able they are. I'd be capable of doing the work but I don't want something that causes problems such as invalidating my house insurance.

dmsims

6,452 posts

266 months

Monday 26th September 2022
quotequote all
PCoulson said:
No being a powerfully built company director (overweight local government officer) I don't have the funds for a proper system but what are peoples thoughts on https://www.pluginsolar.co.uk/?product_cat=plug-in...

Reading up it seems there much contradictory info on how diy-able they are. I'd be capable of doing the work but I don't want something that causes problems such as invalidating my house insurance.
Expensive and Enphase is not DIYable anymore