Solar - Where to start?

[Marvin]

2 minutes ago, SteamyTea said:

No, PVGIS assumes 14% losses on the PV side, probably similar on a DC side.

But I was making an Anti-Sales pitch.

Batteries are all the rage, and tomorrow there will be a 'game changer' i.e. V2G, Hydrogen, novel chemistries....

I see the way forward for thermal stabilisation to be individual home independence, probably using a sand thermal store below the floor slab. 

[Pocster]

1 minute ago, SteamyTea said:

No, PVGIS assumes 14% losses on the PV side, probably similar on a DC side.

But I was making an Anti-Sales pitch.

Batteries are all the rage, and tomorrow there will be a 'game changer' i.e. V2G, Hydrogen, novel chemistries....

Then we all wait for the next big thing and actually do nothing . The number of times I’ve been told my EV is no good as we will “ soon all have hydrogen fuelled cars “ - which clearly it isn’t possible to produce hydrogen in the quantity required .

Even if a home hydrogen battery ( or whatever ) technology came out tomorrow; so what ?

[Pocster]

3 minutes ago, Marvin said:

Hi @pocster

 

Impressed with your outlay to yearly repayment! How do you heat your home? We can't manage that!

I have added to my system since . Doubled pv , added SE battery .

Ufh of uvc and ASHP . We are ( as you can imagine ) very well insulated. I personally find the house too warm even in winter - SWMBO begs to differ . In essence I’d be happy with zero heating all year round - that would save a few more quid 😁

[SteamyTea]

53 minutes ago, pocster said:

Then we all wait for the next big thing and actually do nothing

I was being ironic.

[Dave Jones]

5 hours ago, SteamyTea said:

Not just the length of time, it is the power of each heating source.

If your kettle is about 2.8 kW and your gas boiler is 20 kW, then 

5 minutes for the kettle is 0.23 kWh, boiler 5 kWh.

So get some proper timings, the power ratings and we can see.

And outputs.

What size is your battery system and what is the utilisation like?

Finding the Goldilocks zone is the hard part.

 

There are 3 parts to having a battery system (4 if you include cost).

The actual usable storage, the kWh.

The charge rate, the input kW.

The discharge rate, the output kW.  It is this last one that is important as some system need a 200W+ load to start delivering and may top out at a 2 kW load, though I would hope most would be capable of 3 kW at least (enough for a kettle).

 

lol 5kwh to boil a kettle.

 

math is not strong here.

[SteamyTea]

5 minutes ago, Dave Jones said:

math is not strong here.

Nor are your reading skills.

 

[Simon R]

9 hours ago, SteamyTea said:

What size is your battery system and what is the utilisation like?

Finding the Goldilocks zone is the hard part.

I think I hit on the Goldilocks zone by good fortune and a bit of calculation. 

Daily consumption runs in the region of 15kWh (including EV)

Our battery is a 9.5 kWh GivEnergy unit coupled to a 3.6kW GivEnergy inverter and two PV strings of 6 panels each. The inverter will only deliver 2.4kW from the battery the remainder coming from solar. 

Octopus provide our electricity with a cheap overnight rate between 23:30 and 5:30.

In winter we run a 3.5kW A2A unit at 22C to heat i our living area on the cheap rate electricity and bring the battery to 60%.

In summer the battery is set to charge to 20% on the overnight rate but it's rare for this to happen as there is nearly always more charge left in them. The 3.5kW A2A keeps the house at 22C and runs from 7:00 until 21:00.

The result is that we run almost exclusively on the cheaper overnight rate in winter and in summer barely take from the grid at all. For June:

cheap rate 67.3 kWh £4.80

peak rate 31.4 kWh £11.88 (mainly due to charging the EV at 10amps during the day and using appliances while it's charging)

standing charge £12.32

For February:

cheap rate 339.5 kWh £24.24

peak rate 9.6 kWh £3.63

standing charge £11.50

 

 

 

 

[DazRave]

1 hour ago, Simon R said:

I think I hit on the Goldilocks zone by good fortune and a bit of calculation. 

Daily consumption runs in the region of 15kWh (including EV)

Our battery is a 9.5 kWh GivEnergy unit coupled to a 3.6kW GivEnergy inverter and two PV strings of 6 panels each. The inverter will only deliver 2.4kW from the battery the remainder coming from solar. 

Octopus provide our electricity with a cheap overnight rate between 23:30 and 5:30.

In winter we run a 3.5kW A2A unit at 22C to heat i our living area on the cheap rate electricity and bring the battery to 60%.

In summer the battery is set to charge to 20% on the overnight rate but it's rare for this to happen as there is nearly always more charge left in them. The 3.5kW A2A keeps the house at 22C and runs from 7:00 until 21:00.

The result is that we run almost exclusively on the cheaper overnight rate in winter and in summer barely take from the grid at all. For June:

cheap rate 67.3 kWh £4.80

peak rate 31.4 kWh £11.88 (mainly due to charging the EV at 10amps during the day and using appliances while it's charging)

standing charge £12.32

For February:

cheap rate 339.5 kWh £24.24

peak rate 9.6 kWh £3.63

standing charge £11.50

 

 

 

 

 

So, this is exactly our intentions. We're already on Octopus and have a cheaper rate at night which is Ideal as unlike the norm (well, from what I gathered reading everyone's posts) we use most of our energy at night. 

 

We're extending the house with the intention of staying in it to bring up a family. So the plan is 15 years or more and unless we both hit the jackpot or either of our businesses do extremely well I don't see that changing.

 

ROI isn't massively important. I think I can budget for somewhere between £8-10k for a solar system with battery but that's not to say i actually want to spend that much (I got the feeling a few people just thought I wanted to throw money at a problem).

 

Ideally, we want predictable, stable and low as possible monthly bills for the next 5 years at least while we start a family after our home is soon to be big enough.

 

I've a lot of electronics which also includes two high end PCs as well as a home server which are usually on in the evenings and sometimes in the daytime, but not often.

 

As a side note, we've been in the house for about 5 years now and we've had frequent power outages from a couple of minutes to half an hour at a time. Usually we get these in the summer months, a couple times a month. I know this because my server and network are knocked offline and records it's downtime accurately. A small UPS on the server helps shut it down safely but it would be a dream if it could just stay online without a hiccup instead! (Don't ask why we get them, the entire area is still trying to figure this out).

 

So, to jump back on topic about being new to all of this:

 

Am I right in thinking a battery can only output X amount at any one time, so switching on an electric induction hob or oven would more than likely trigger the switch to use grid energy again and the main reason for a battery is to power all the smaller constantly used devices around the home, such as for LEDs, TVs, modems, charging phones etc etc?

 

Edited July 4, 2023 by DazRave
Typo

[DazRave]

12 hours ago, Marvin said:

Hi @DazRave

 

In my humble opinion I would install as many panels as possible as long as the mains doesn't need to be upgraded.  You will produce too much energy in the summer and not enough in the winter. We also have battery back up. both are DIY installed - with DNO permission.

 

We have AIM and APE,

 

That is Airtightness, Insulation, Mechanical Ventilation with Heat Recovery, and an Air Source Heat Pump, Photovoltaics and an Electric Vehicle.

 

We installed our own PV system (not including batteries) and it cost about £4k for a 5.12kW system ( that is to say all things being perfect on the best sunny point of the best day the system would produce 5.12kW an hour - never seen it by the way) Inverters usually allow you to instal up to 20% more panels than its limit. Our inverter is a 6kW one but allows up to 7.8kW of panels.

 

We judge our PV system (not including batteries) would last about 7 years so the daily cost is about £1.60.

 

Batteries are a funny thing, and unless you are paying more for your day time electricity and less during the night on some scheme I would recommend thinking long and hard about your decisions.

 

In the winter you would have almost nothing spare from the PV to charge your batteries

In the summer you would have far too much to charge your batteries.

In the other times you would have power to charge your batteries.

 

If you charge your batteries using cheap rate night mains you waste the spare power from the PV for about 5 months of the year OR you charge the batteries using the cheap rate night mains and waste the PV power.

 

When you do all the maths, if you have PV, the most logical system I see is one that supplies enough over night power to run your night time low demand load. This system can support say about 3 days worth of night time energy, but go beyond that and the figures don't really work.

 

If you want to go through the iterations leading to the same conclusion PM me. This goes for anyone else as I would love to know of the exceptions. 

 

 

 

Good luck

 

Marvin

 

PS. Don't forget the significant losses converting AC to DC and back again.

 

 

 

 

 

 

 

 

 

 

 

I just wanted to quickly thank you for your post.

 

I'm not really interested in who's system is better and why because they are not me. I'd rather get a dummies guide on what things do and how they work together.

 

So yeah, thank you. Your post gave me plenty to think about!

 

[SteamyTea]

3 minutes ago, DazRave said:

we use most of our energy at night. 

Do you know how much, have you thought of doing some decent monitoring (better than a smart meter shows i.e. every few second or every Wh, zero draw times, minimum draw, maximum draw).

5 minutes ago, DazRave said:

I've a lot of electronics which also includes two high end PCs as well as a home server which are usually on in the evenings and sometimes in the daytime, but not often.

We all like power, but how much do they actually use?  Measure them.

6 minutes ago, DazRave said:

As a side note, we've been in the house for about 5 years now and we've had frequent power outages from a couple of minutes to half an hour at a time. Usually we get these in the summer months, a couple times a month

You will need an 'islanding' system, they generally cost more as they have to totally isolate the house from the grid when there is an outage.

As it is in the summer, is it trees, or too many local PV systems causing over-voltage shutdown.  You could ask your local DNO if they will allow you to fit PV over the usual 4kW/16A per phase.  They can, in exceptional circumstances, refuse a smaller system.

9 minutes ago, DazRave said:

Am I right in thinking a battery can only output X amount at any one time, so switching on an electric induction hob or oven would more than likely trigger the switch to use grid energy again

Not really a switch, the PV/Battery system delivers at a slightly higher voltage than the grid delivers, so power naturally flows to the nearest load.

10 minutes ago, DazRave said:

power all the smaller constantly used devices around the home, such as for LEDs, TVs, modems, charging phones etc etc?

It depends on what the minimum load the system needs to start.  As I mentioned earlier, some need to 'see' a 200W load before they do anything.  So worth looking into that.

 

Lots if monitoring is needed, it is cheap and easy enough to do.

You can make useful charts as well.

 

 

 

 

 

[DazRave]

@SteamyTea - In a past life I was a product designer and full stack engineer (I sort of sell kitchens now, but that's a long story 😂) so I've got a bit of an automated home and there's automation built into the design of the extension too. The majority of devices that consume the most are trackable, the only exceptions were the extremely old appliances in the kitchen (I say this in a past tense, as a digger cut my old kitchen in half last week and popped a hole in the side of the house!) so to track the kitchen appliances I used a couple of formulas to tell me when electricity spiked historically based on Octopus Energy half hour meter readings.

So we always found that we used the most amount of electricity from 8pm onwards (disregarding short term spikes such as half an hour with the oven/hob on) the long duration peaks come when I've got my high powered pc spinning and the missus is next to me using hers as we often catch up work at night. I guess this is also backed up by Octopus energy too, which claims our busiest time is between 7.30pm and 8pm most days (which is skewed slightly towards the time when we cook as bear in mind we did have extremely inefficient and old electrical appliances). It's interesting too, as Thursdays are the evenings we're most likely both in the home office. It's also the day Octopus says our peak is slightly later, at around 8.30pm and 9pm. A quick look and we're consuming quite a lot of energy from 8.30pm which drops slightly at midnight (when the missus usually retires) and drops down to middle of the day sort of levels when I've called it a night in the early hours. On top of this, we use the washing machine at night too since we're home anyway and the Octopus rates are cheaper, but this of course isn't every night.

 

1 hour ago, SteamyTea said:

You will need an 'islanding' system, they generally cost more as they have to totally isolate the house from the grid when there is an outage.

As it is in the summer, is it trees, or too many local PV systems causing over-voltage shutdown.  You could ask your local DNO if they will allow you to fit PV over the usual 4kW/16A per phase.  They can, in exceptional circumstances, refuse a smaller system

I've no idea. We've been told they are investigating the cuts on and off for the last few years. We'll go a while without them and they'll claim it's sorted, then they trigger again. Either way, what does an 'islanding' system consist of? Does a solar and battery system that's off grid not already achieve this? Additionally, if I'm not interested in selling back to the grid do I even need permission from my local DNO? I'm after a dummies guide on a lot of this stuff, remember.

 

1 hour ago, SteamyTea said:

It depends on what the minimum load the system needs to start.  As I mentioned earlier, some need to 'see' a 200W load before they do anything.  So worth looking into that.

Gotcha. I appreciate that insight. EDIT: A quick look at the PC and it consumes between 500-650w if I'm rendering some 3Ds for an hour or so. So between the server, two PCs, a few PC monitors and a TV on in the background, it's around 1.2 to 1.5kw and we'd sometimes be working for at least 4 hours in the evenings, especially on a Thursday.


For the record if anyone is interested:
I use a home server running dockerised Home Assistant and Node-RED containers for the dashboards and automation. I also run a mainly wireless zigbee and MQTT network for all the nodes and devices across the network to communicate. Thankfully everything within the extension will be mostly 'home-run' hard wired and for everything else I'll be moving over to Matter (once it's rolled out a little more over the coming months).
 

Edited July 4, 2023 by DazRave

[Crofter]

Interesting thread. I'm starting to realise how little I know about all of this.

 

In the spirit of being an absolute dummy, am I right to think that the most basic system would comprise panels, MPPTs, and a grid tie inverter, plus necessary isolators etc? Would there be any need to even tell the electricity supplier? Is the inverter clever enough to sort out how to share the loads around?

 

(I know a reasonable amount about off grid PV, because I'm currently living off grid on my boat, but I'm a total novice when it comes to grid tied systems).

[SteamyTea]

@DazRave

 

I am not ignoring your questions, just trying to write a a bit of a guide that will cover most of what you want.

One problem with forums is that the same questions get answered over and over again, usually by the same people.

I would quite like to avoid that, and now seems like a good time to start.  May take a few days, and hopefully I will have something for you.

[DazRave]

3 hours ago, SteamyTea said:

@DazRave

 

I am not ignoring your questions, just trying to write a a bit of a guide that will cover most of what you want.

One problem with forums is that the same questions get answered over and over again, usually by the same people.

I would quite like to avoid that, and now seems like a good time to start.  May take a few days, and hopefully I will have something for you.

 

Wow, well, thank you in advance if that's the case!

 

I had tried to find a bit of a glossary just to explain the acronyms and terminology first but couldn't really find anything that made sense and it just started to frustrate me, so I took to here. 

 

 

[SteamyTea]

51 minutes ago, DazRave said:

acronyms and terminology

We have our own on here. 

 

 

Edited July 5, 2023 by SteamyTea

[DazRave]

As a pre-warning... this will be long. So there's another TL:DR at the bottom to save time!

Let's get started
So I'm back and I'm now slightly more informed than a few weeks ago when I initially created this thread. I'm writing this because these posts can often be super helpful for someone like myself.

Feel free to read and share any helpful advice but please refrain from opinions which will quite clearly just trigger people. One thing I have learnt on this journey for definite is that everyone's requirements are extremely different. So please discuss the differences between options etc but let's keep it civil, informative and to be honest, fun!

To clarify my objectives here, I'm looking to reduce (or better, eliminate) my monthly bills by investing now while we have the capital. I'm not looking for an amazing ROI in the shortest time possible. We're building a large extension onto the house with the intention of staying here to raise a family for the next 15+ years, minimum.

So here's where I am at now:

I crunched an absolute ton of data (basically uploaded 2 years worth of half hourly meter readings into ChatGPT). I manged to work out loads of interesting habits such as common peak times, highest/lowest usage days and highlight other weird anomalies.

• I'm pretty certain approx. 10 to 12kwh of solar storage will do me justice
• I'm looking at around 8 to 12, 405w, solar panels
• In-roof systems look pretty straight forward
• I've had some quotes back and for the system I was looking at from an MCS qualified supplier/installer we're looking at £12k
• A DIY approach, which also includes a bonus 300L solar hot water cylinder, would be approx. £6k
  • Granted, this doesn't include fitting
  • But, some of which I'll do myself with my electrician. The roofers, who are installing sky lights too, have agreed to install the GSE in-roof frames for the solar panels while they are up there tiling
  • Finger in the air slightly, let's say unforeseen costs plus installation help from my on site trades is around £3k, then the final DIY route is now only a few grand less than the MCS approved route but still less than my initial £10k 'max budget'
• Since my original post, Octopus announced they were scraping the requirement for an MCS and I originally thought I'd struck gold on the timing!
  • However, news articles everywhere would lead you to believe this is a done and dusted decision by them.
  • However, after talking to them directly myself, it's actually just a trail on a very select number of customers. damn.
  • I'm hopeful they will still roll this out fully and I've signed up to be a guinea pig regardless. fingers crossed.
• G98, 99, 100 etc forms are kind of confusing.. it's still not clear which or what I need if I never ever intend to sell back to the grid but I'm assuming the worst in all my planning for now and I'll work backwards from there
• There's a requirement that I'm still yet to even bring into this and that's a UFH system. We've not decided on wet or electric yet and to be honest what I decide here might then have a knock on effect to this

 

 

What's next?

I'm not actually sure at this point! I do need to make a decision pretty quickly as we're getting close to needing the new roof, which, was the entire point of all of this.

• DIY route
  • CON: Prevents me from selling back to the grid and offsetting bills
  • CON: Potentially much shorter warranties on some of the cc when not installed by someone deemed 'approved'
  • CON: Dealing with more moving parts and more trades here, I've got to do more self learning and anything could go wrong at my expense
  • PRO: I can throw in a hot water cylinder to offset the gas usage (topped up by my gas boiler when there's not enough free energy)
    • This actually has another unexpected and positive side effect, which is better water pressure! To which we have extremely poor pressure in the area and it's always annoyed us
  • PRO: I mean, cheaper, but only slightly I guess
  • PRO: From what I can gather, all the components/materials are either equal in quality or superior in some way.
    • e.g 2 modular batteries total over 10kwh whereas I was quoted for a single battery at about 9kwh
• 'Approved' MCS route
  • CON: Easy one to start with. Cost.
    • It's about £4 to 5k more like-for-like
    • It's approx. £2k more when comparing to the DIY route that's got a hot water cylinder
  • CON: Although I'll have the MCS, if Octopus roll out 'no-MCS' fully then surely 'selling back' rates will only ever start to be less and less beneficial anyway?
    • Might be a long winded assumption of course but it would piss me off regardless
  • CON: The solution isn't quite as flexible and specific to my needs
    • Granted, this could be due to the installer preferring one brand over another or perhaps a lack of understanding of my requirements and could be changed. 
  • PRO: Easy peasy 
    • I wouldn't actually really have to do much as they'll take care of everything
  • PRO: I can sell back to the grid, bringing me closer to that low/zero bills desire
  • PRO: Longer warranties on some of the components used when installed by an approved installer
    • Worth pointing out I don't know what the standard warranties are on some of the parts, as it might only actually be a year longer etc so not that much of a positive!

 

And breath. Sorry about all that but thanks for reading!

Too Long, Didn't Read: 
I still want to reduce bills with solar panels and batteries long term. Even looking at hot water cylinders now. DIY route is cheaper but of course has cons like no grid selling. MCS-approved route costs more but offers convenience. Still deciding as Octopus's no-MCS plan is uncertain.

 

[Crofter]

Good summary, thanks for taking the time to share it.

Like you, I'm watching the Octopus situation closely. It would be a game changer if the trial became an option for everybody.

[Big Jimbo]

My plan so far is to fit 17, 435w solar panels on the roof using gse trays (only ones I can find) fit 17 optimisers. I would like to fit these in the loft, rather than under the panels, so they could be got at more easily in the future. Run however many cables I need from the loft, down through the house, and duct them under the block and beam floor and into the detached double garage about 4 meters away from the house. Run a fat wire back from the garage in a separate duct to under the stairs, for potentially powering an immersion on the unvented hot water cylinder. That's as far as I have thought so far. I haven't had a chance to think about inverters etc so far. The above should be achievable DIY for about 5k. Hope I'm not missing to much so far. 

[SteamyTea]

3 minutes ago, Big Jimbo said:

My plan so far is to fit 17, 435w solar panels on the roof using gse trays (only ones I can find) fit 17 optimisers

Can you realistically use 7.3 kW_p of PV?

Do you need optimisers?

 

[Big Jimbo]

Thinking further, I would need some ac/DC safety cut off switches, an inverter or two ? Some sort of diverter to send power to the immersion. Some sort of diverter to an electric car charger. Got to find some more time to get into it. My total budget is 12K so with what else I still have to get, I doubt a battery will be included.

[Big Jimbo]

1 minute ago, SteamyTea said:

Can you realistically use 7.3 kW_p of PV?

Do you need optimisers?

 

I'm sure it was you that told me to fit as much as I can while building the house. I would defo get bits of shading to each of the 3 elevations from some tall trees. I'm happy for any suggestions.

[DazRave]

3 minutes ago, SteamyTea said:

Can you realistically use 7.3 kW_p of PV?

Do you need optimisers?

 

 

I assume he's trying to heat the water even in the dullest of days? So it's less about the max output and more about bringing the min output up higher. Surely.

[Big Jimbo]

@DazRave to be honest, it was more about sticking as much as possible on the roof while it was being built.

[JohnMo]

24 minutes ago, SteamyTea said:

Can you realistically use 7.3 kW_p of PV?

Do you need optimisers?

 

Some info on our experience.

 

We started with 3.1kW of PV and could self consume that with ease, very little went to the grid, but we are home all the time.

 

Next we added a further 3.6kW, ran the ASHP in cooling mode, that consumed most of it, everything else went to an immersion. But on a sunny day electric still made its way to the grid. We had loads of 80 deg water that we didn't really need.

 

Our first array has optimisers, due to tree shadow, our second doesn't and doesn't need them. Optimisers only really worth it if you have known shadow issues.

 

We now have a battery 17kWh usable. This is a useful tool, better than water, yesterday from 11am to midnight we used no grid electric, battery charged by PV (not fully, but enough to back fill our usage). By midnight the usable energy was depleted. However due to heavy rain all weekend no battery charging was done and very little PV energy went to the house about 1kWh each day.

[SteamyTea]

1 hour ago, Big Jimbo said:

I'm sure it was you that told me to fit as much as I can while building the house

Quite possibly, and 7ish kW isn't an excessive amount in the he scheme of things.

 

It is difficult to find the optimum amount, and where that fits in with the finances.

Battery storage systems are skewing the formula somewhat as they make installed capacity seem cheap for every kWh delivered.

1 hour ago, DazRave said:

So it's less about the max output and more about bringing the min output up higher. Surely.

Yes, but optimal winter angles can do that, but you may end up with an odd looking house.