One family's solar story

[Sideways]

Just to give provide picture to help you visualise this

See the upper blue line on the screenshot, note the peaks during the night at a time when we are running off battery with around 62% charge - the yellow line - and consuming just a couple of Watts from the grid.

 

[Sideways]

When designing the distribution wiring, DNOs allow an average of just 2 to 3kW per household. Cables are sized and transformer tappings selected based on delivering this average power to many homes. If people turn off their appliances, voltages rise, and if enough of them all turn on the 7kW electric car charger at the same time, voltage will sag. Mains voltage has a permitted range to cope, but to minimise the voltage variation in the face of big changes in demand, resistance of the cables must be kept low. This costs £££ as copper for thicker wires with lower resistance is expensive !

There is a need for massive strengthening of the grid to support decarbonisation. This will cost at according to the last estimate I read, half a trillion pounds over the next 30 years, and we'll all pay towards this through the electricity unit price.

 

[gmgmgm]

We had very high voltage here, often clipping when it hit 253v. I have some wifi plugs in the house (which also tell you the voltage) and luckily bumped into the engineers when they were fiddling with our transformer. With the evidence I showed them of high voltage over many months, they were able to turn it down "a notch" on the transformer (I gather it has several settings inside) and now we're around 230v. Much better for solar inverters.

 

[Sideways]

Great result. Well done !

 

[Vulcan]

Very interesting thread. We’d like to install solar panels but roof condition, orientation and shading preclude us from doing so. The cost of an installation is of course important but we’d be looking at it from an energy security standpoint. The cost of home storage batteries seems to be going down as well which makes SP even more attractive.

 

[Sideways]

I have been meaning to post that as of about 5 days ago, for the first time in several months, our battery storage tapped out and we had to draw a few kWh from the grid. As the weather has turned miserable, our generation is down to between 3 and about 10kWh a day at this time of year. Given a few hours of strong sunshine we can quickly top out the battery and ride through a few poor days bit we are into the 4 months of the year when we pay attention to power use and adapt to the weather.

Here are the graphs of our last few months

I've set 15% capacity as my bottom cut off

 

[Vulcan]

This just popped up in my feed. Even if it's only half correct it must surely accelerate the end of ICE cars?

 

[worn thumbs]

Hardly! Given the price volatility in the electricity market I can understand the desire to ensure a steady supply and be independent.It isn't an option for everybody since we don't all live in properties that would allow us to install generating capacity.Additionally,not too many people have the cash available to get the hardware installed.I don't doubt that, given the space and the money,it will probably pay for itself in quite a short time for those who can make the move.For this area,not really an option ,is it?

 

[John Brown]

Very interesting thread. We’d like to install solar panels but roof condition, orientation and shading preclude us from doing so. The cost of an installation is of course important but we’d be looking at it from an energy security standpoint. The cost of home storage batteries seems to be going down as well which makes SP even more attractive.

Shading is a problem, but I was surprised by the viability of east or west facing panels. North are pretty useless at my latitude, but if you look at the tables available, east and west are around 80% of south.

 

[J-G]

Shading is a problem, but I was surprised by the viability of east or west facing panels. North are pretty useless at my latitude, but if you look at the tables available, east and west are around 80% of south.

My property is oriented with a 'corner' facing south (within a couple of degrees so I have panels on two roofs, one facing ~SE & the other ~SW. I also have a Silver Birch which has a 14% shading effect on the SE roof.

The bottom line is that with a 4k system I can expect ~3.35k - 83.75% - so the loss due to orientation amounts to some 2.25%

Well it would if the b****y inverter wasn't playing silly beggers at the moment !!

 

[Sideways]

We face southeast, near enough 45 degrees off the ideal due south.
The biggest impact is that it shifts our solar day earlier. We get an early start and have generally lost the sun by 4 to 5pm. Summertime, the battery can be full by 10.30am !
Shading is worse in the winter months as the low angle of the sun means a neighbours roof shades the lower third of our panels which don't turn on until 11am.

But for the year as a whole, shading and orientation have less impact than you might imagine unless there are trees, etc in just the wrong place.

 

[Sideways]

And just for interest as this has now been running for a while, compare the 2022 and 2023 graphs.
2022 didn't begin until April and 2023 hasn't quite ended yet so it's not an apples for apples comparison but comparing the same months show that 2022 was distinctly brighter than this year - by 100kWh a month

 

[Spectric]

Shading is worse in the winter months as the low angle of the sun means a neighbours roof shades the lower third of our panels which don't turn on until 11am.

Always going to be an issue with fixed panels, not easy in the rotation axis which would be ideal but why not hinge the panels and use a simple motorised system like with satelite dishes to keep the angle at it's optimum ?

The biggest issue with both EV's and renewables is that big old elephant in the room, storage of electrical energy which means some chemical process that for EV's has high density but for other uses size need not be the limiting factor .

 

[John Brown]

Not sure how a hinged motorised system would help with shading! As for optimum angles, I think the cost and complexity outweigh the advantages. Satellite dishes(if you're talking satellite TV)don't generally need to be moved, as the satellites are in geostationary orbits, but in the event that you want to focus on a different satellite, the motorised dishes tend to describe a polar arc(not talking about dishes on RVs, obviously). I don't think this would work for solar panels, as the height of the sun appears to vary with the seasons.

 

[deema]

I might have missed where you highlighted this, but what’s the difference between ‘consumption’ and ‘self consumption’?

 

[Sideways]

Consumption is what we consume - including power drawn from the grid. You see in 11 snd 12 2022, we consumed about twice what we were able to make ourselves. Jan 2023 we only made 2/3 of what we consumed. In these months, the blue bars are longest.
All last summer and since Feb this year, even until now except for just a few kWh in the last 10 days, we have made more than we consume, and the orange bars are highest.

Self consumption is the part of our generation that we use ourselves, with any excess being exported. The house takes what it needs first. The battery is then filled at anything upto 6.6kW and above that we can dump upto about 8kWh into the immersion heater at a rate of 3kW. Blue and yellow are little different most of the year showing that what we use, we get almost all of it from our own generation and storage.

The orange peaks across summmer are export. I'll be signing up for an Octopus export tarriff this winter so next year we should start earning upto £250 a year from our surplus. I haven't bothered so far. The Octopus flux tarriff that will make it worthwhile was only launched earlier this year. In fact, we could now be paid twice as much for export as it would cost to heat water using gas so our priorities may change between the solar diverter (hot water) and export.

The practical problem is that we have to limit what we export because the grid is such a high voltage locally that if we "pushed" several kW into it as our license allows, we'd drive the voltage well above the maximum allowed. The inverter will not permit this.
With a little careful management we may be able to export hard in the early morning while the grid is being sensible because we have a big array and it wakes up earlier than most local solar. Over the midday period when the grid voltage rises because other solar systems are feeding it we need to take care not to export at all or our system takes a pause. The downside of buying good kit that actually obeys the rules !
The best way to cope with these grid peaks which happen between 11 and 2 on bright days is to be soaking up all of our own energy at that time, which we can do as long as the battery and hot water tank have capacity left.

Some people might not bother but we've become much more aware of the weather than we were and to adapt to live with it. It's a little like getting back in touch with nature.

 

[Ollie78]

Interesting stuff, I am gathering quotes for solar at the moment. I see no point without a battery personally. Already had the smart meter fitted etc.

I have a roof with one face almost dead south and one east and one west, there is some confusion between different companies as to what is best, some are saying don`t bother with the south, put one east and one west. This, from what I can gather is because they only want to use a 2 string inverter. To my mind I say why not use all 3 for maximum gain, each roof is actually quite small and triangular so why not maximise capacity.
One company was saying I needed optimisers on each panel because of shading etc. but there are no trees or anything and the chimney barely shades as its on the north part, I was trying to get them to explain why they were necessary and wouldnt the bypass diodes already be enough in my case and they could not answer my question.
I have had 4 quotes and the plans and system designs have all been surprisingly different.

I do notice the industry has lets say, a "high profit margin". I looked into some of the kit they were quoting and I could buy it at "retail price " for about £8k,
scaffolding is probably £600 and even paying 2 top notch sparkies for a day is only going to be £800 you probably only need one plus a labourere they told me it would take less than a day to install it all.
Some of them want £14.5k or more and there is no way they are paying the retail price for parts. I know there is design to be done and paperwork etc but it looks like a good earner.

The grand designs project on channel 4 this week was interesting, they had a giant roof and had it completely covered in a Lithuanian made solar roof which was glass and metal panels fitted like standing seam zinc or copper roof. Looked really smart actually. They were making a passive house plus which is a new standard where you generate more than you can use yourself.
Anyway, they got it all working and everything but the local grid could not accept the full amount so quite a lot was being wasted instead of being used in the local town as it should have been.

Ollie

 

[Sideways]

Our install was pricey. I gave some numbers earlier. About £24k all up I think but for a system that is 2-3x the capacity of a typical 4kW system. There was about £18k of materials cost in that. I know as I chose or approved all the components that went into it. We bought premium parts with long warranties and top quality build then Covid supply shortages meant no chance of discounts on the parts.
24 panels on one single roof face plus the wiring up basically took 2 guys and an apprentice a solid week. A skilled sparky came in extra for a full day to swap the consumer unit and later half a man day to build and integrate the battery stack.

Re the optimisers, waste of money if the panels aren't shaded.
Re the two string inverter, this is pretty standard. Three very different roof faces would need 3 strings and that might push you to two inverters. 2 inverters together imposes some limitations compared to using just one but a good basic 3kW inverter isn't more than £1,000

Take a good look at the components proposed by your different bidders. That's where a lot of them will be cutting costs. They will use cheap brands and limited capacities.

 

[Ollie78]

Our install was pricey. I gave some numbers earlier. About £24k all up I think but for a system that is 2-3x the capacity of a typical 4kW system. There was about £18k of materials cost in that. I know as I chose or approved all the components that went into it. We bought premium parts with long warranties and top quality build then Covid supply shortages meant no chance of discounts on the parts.
24 panels on one single roof face plus the wiring up basically took 2 guys and an apprentice a solid week. A skilled sparky came in extra for a full day to swap the consumer unit and later half a man day to build and integrate the battery stack.

Re the optimisers, waste of money if the panels aren't shaded.
Re the two string inverter, this is pretty standard. Three very different roof faces would need 3 strings and that might push you to two inverters. 2 inverters together imposes some limitations compared to using just one but a good basic 3kW inverter isn't more than £1,000

Take a good look at the components proposed by your different bidders. That's where a lot of them will be cutting costs. They will use cheap brands and limited capacities.

Thanks for this information Sideways.

I thought the optimisers didn`t make sense and my thinking is that it is a more things on the roof that could fail and are hard to access, similar issue with the Solar edge system or the micro inverters like enphase.

Your point about the components is important, we have already thrown out a few of quotes for this very reason they did not specify the exact parts to be used, and when asked could not confirm. One lot advertised one companies stuff but then on the detailed sheet it was all different cheaper stuff.

Another company who shall remain nameless said that they had thier own panels made to a bespoke specification, a 5 minute part number search found this to be an absolute lie, they were a very high spec panel, made by a respected manufacturer but they were just standard off the shelf units. They even had the cheek to just use the manufacturers exact spec sheets and graphs etc. My problem there is just the lie, the panels were a great spec with long warranty. I think a lot of people don`t notice details or check stuff so they get away with it.
When I asked them about it they had no answer, like 5 year olds covered in chocolate saying they have certainly not eaten the kit kats.

It is a bit disconcerting that there are so many options being proposed. At this point I would almost rather get an independent expert to design the system with no connection to any installation outfit.

I think we can get 4 panels on each side for 12 total and with a largeish battery should be enough for for our fairly low usage except in the dead of winter and with the octopus flex tarrif we will buy at cheap rate to top up in winter. Long term it is certainly a wise move but we need to find the right system.

Ollie

 

[Dabop]

I had a east/west split for a while at the old house (due to the roof design) and it actually made almost identical daily totals as a neighbours all north facing system (same install company, same equipment, even the same installers a couple of days later) on sunny days the outputs were almost identical (sometimes his was a hundred watthours ahead, sometimes ours), what was really noticeable was the performance in 'cloudy weather' with all day 100% cloud cover, where we both lost output, but ours was always well ahead of his 'ideal' install- usually by several kwh more per day....
While his had a higher midday peak (by about a kw) our started much earlier, and ran much longer- our east bank started literally at dawn (with it hitting over a hundred watts with only half the suns disk visible) that east bank peaked about 10am, with the west bank starting on come online, the west bank peaked about 2pm and continued right up until sunset, where his started a couple of hours later than ours, hit it (higher) midday peak and then dropped off until it was stopped, well before our west bank finished...

Orientation isn't as critical as many believe, with a good high voltage east/west split being comparable to the equal amount of panels facing north (for Australia, obviously in the UK north = south there)- the most important thing is to have as high an array voltage as is possible 600v PV max inverters are good, but the 1000v ones are better, with you still exporting usable power in low light conditions... avoid any of the 400v ones (getting rare these days) as they really only work in 'bright, sunny' weather... (you need to be above the '360v DC' mark to even start exporting to the mains grid as that is the peak value of the '230vAC' RMS grid voltage- a higher array voltage (more series panels or higher voltage panels) makes this easier to do- as long as the inverters peak PV voltage is rated for it...