Solar Panel quote

matelodave

Reed_Richards said:

I have an Air Source Heat Pump.  Yesterday it drew 6.85 kWh of energy, operating in the morning and then again in the evening.  This is the output from my solar panels and the state of charge of my 6.5 kWh battery.

Interesting to see how long it took the battery to get up to 100% and how quickly the battery capacity dropped in the evening. Probably due to the heatpump operating in the morning and evening before the sun got a chance to replenish it and pulling it down in the evening. I'm sure that the profile swould be a lot different for someone who didn't have "on demand" electric heating, like stsorage heaters or those with a fossile fuel system.

It would be useful to see what happens in the middle of say January and again on a nice sunny day in June. TBH I think this year the weather has been a bit awry, April was everso cold so many of us have had to keep heat on (ours was running this morning) and we dont seem to have had a great deal of sun over the past few weeks either. (your sun seems to have gone in for a couple of hours around peak generating time yesterday)

 I'm guessing that as the battery is down to around 10% overnight you dont take advantage of an off-peak tarrif to recharge it.   Although that said, I'm not convinced that off peak tariffs are suited to heat pump operation.

As you know I like graphs as they give you a much more visual representation of what is going on - it would be nice if you could superimpose your consumption profile over the top to see how well it matches your generation and storage.

[Deleted User]

Reed_Richards said:

Dolor said:
...Being self sufficient for energy from mid March until late September must add value to my property should we decide to sell.

You won't be self-sufficient in energy in the sense that you don't have to import any electricity.

• There will be times when it is cloudy for too many days in a stretch
• You battery won't respond fast enough to a sudden peak in demand like turning on an electric kettle and you'll have to import from the grid whilst it adjusts.  

We are self sufficient and have been since mid March because even on a poor day our solar generates enough for the Powerwall 2 to see us through two days of poor weather. Our daily power consumption is not that high and I can charge my EV when the sun is out. Our PW2 is capable of outputting 5kWs. I accept that a PV solar; Grid and battery system may take a few watts off the Grid as the system balances demand versus supplies. That said, my total Grid import this month so far is 112Whs out of a total Home Usage of 250kWhs. I would suggest that this is pretty close to being off Grid. 

Today is a miserable day with wind and rain but my array is outputting at 2kWs. The PW2 is at 95% SoC and there is enough time left in the day to heat the hot water cylinder. Yesterday, was a day of sun and showers, and the array generated 35kWhs.

matelodave

Dolor said:

Reed_Richards said:

Dolor said:
...Being self sufficient for energy from mid March until late September must add value to my property should we decide to sell.

You won't be self-sufficient in energy in the sense that you don't have to import any electricity.

• There will be times when it is cloudy for too many days in a stretch
• You battery won't respond fast enough to a sudden peak in demand like turning on an electric kettle and you'll have to import from the grid whilst it adjusts.  

We are self sufficient and have been since mid March because even on a poor day our solar generates enough for the Powerwall 2 to see us through two days of poor weather. Our daily power consumption is not that high and I can charge my EV when the sun is out. Our PW2 is capable of outputting 5kWs. I accept that a PV solar; Grid and battery system may take a few watts off the Grid as the system balances demand versus supplies. That said, my total Grid import this month so far is 112Whs out of a total Home Usage of 250kWhs. I would suggest that this is pretty close to being off Grid. 

Today is a miserable day with wind and rain but my array is outputting at 2kWs. The PW2 is at 95% SoC and there is enough time left in the day to heat the hot water cylinder. Yesterday, was a day of sun and showers, and the array generated 35kWhs.

You do have an unusually large set up. Your solar array is around twice the size of most  installations and at 13kwh, so is your battery  - I'd also guess that it all probably cost nearly twice as much as well.

Almost anyone who doesn't use leccy to heat their place could probably be self sufficient if they installed a large enough array and batteries with a capacity to keep you going for a reasonable amount of time but the cost would be prohibitive without the problem of finding the space for a large array and accomodation for a big enough battery. You dont need many days without sun before the batteries get depleted and then take an inordinate amount of time to fully charge them especially in the depths of winter when your consuption is probably the highest.

I should think that most people would hope that there's a reasonable chance of getting a payback during their tenure at a property (or even in their lifetime) so there's got to be a happy balance. I think you said you were hoping for twenty years - thats a realy long time for many and there's no guarantee that either you or the system will last that long.

Reed_Richards

matelodave said:

As you know I like graphs as they give you a much more visual representation of what is going on - it would be nice if you could superimpose your consumption profile over the top to see how well it matches your generation and storage.

Here you are.  First thing the panels and battery have nothing to give so the load is mirrored by a negative meter reading indication import.  Later in the morning the system handles most of the demand.  From 14:00 to 17:00 the battery is fully charged and there is quite a bit of export to the grid.  In the evening there are a few blips of export to the grid which will be caused by something switching off suddenly forcing the battery to export as it ramps its output down.  

matelodave

Thanks - it really helps you visualise what is going on and lets you see how the profiles interact. 

Looks like you could do with more battery capacity and possibly an overnight boost to cover your early morning consumption. Your solar has recharged the battery by just after lunch but it's run down by bedtime. With a bit more capacity it would probably assist for an hour or two in the morning. More solar would probably charge it up a bit quicker but there's no real advantage because you can't store anymore after 2pm

Once the heating goes off you should be pretty well set up for the rest of the summer into early autumn. I hope you have adjusted your hot waterheating times to maximise the use of solar during the day.
I guess that with fossil fuel heating (gas or oil) you'd be fully covered for a fair proportion of the year

As I said it would be good to see how it all fits together in the winter.

Interesting stuff, and there's not enough of it around to help people work out whether is all a good idea or not, so thanks for sharing it with us all.

Essex_Jim

Again, more interesting information / discussion. Once again thank you very much

Apart from the EV's, we heat the house and water via a gas boiler (There is an immersion). We cook with electric (Induction hob, twin fan ovens).

My thinking is maybe an smaller array (1560) (Presently planning 3120) that would feed a smaller battery (less than 6.4kW). This may be sufficient to run the house in the evening. Charging of the EV's would be via Octopus in the early hours. Reasonable approach or a long way out?

I doubt there would be much spare to feed back in. Putting a system in now, would I get any feedback payments?

Petriix

Essex_Jim said:

Again, more interesting information / discussion. Once again thank you very much

Apart from the EV's, we heat the house and water via a gas boiler (There is an immersion). We cook with electric (Induction hob, twin fan ovens).

My thinking is maybe an smaller array (1560) (Presently planning 3120) that would feed a smaller battery (less than 6.4kW). This may be sufficient to run the house in the evening. Charging of the EV's would be via Octopus in the early hours. Reasonable approach or a long way out?

I doubt there would be much spare to feed back in. Putting a system in now, would I get any feedback payments?

There's no FIT payments, but you would be able to get SEG payments for whatever you export. If you're on Go then you're limited to 3p for exports.

I would have thought that economies of scale would make it better value to go bigger rather than smaller. Obviously I have no idea about the limitations of your roof though.

When I do the sums to see if I could make a battery work, I look at my solar generation data and see that on roughly half of all days we generate less than our average house consumption and the average shortfall is around 5.5kWh. So we'd still need to import around 1000kWh even with a battery big enough to cover our overnight usage. I ignore the EV for this to avoid skewing the results.

At present we import under 2000kWh for the house anyway (out of around 3500kWh total consumption; we self-consume around 1500kWh). We divert around 1000kWh to the EV and export around 1500kWh. We also import around 800kWh for the EV.

So a battery would save us up to 1000kWh or about £120. For a 20 year ROI it would have to cost £2400. If your usage is double mine then you could maybe double the battery budget to £4800 but you'll need a bigger solar array to make it work.

Petriix

Oh, of course my figures are based on deemed export payments whereas your's would be metered so allow for another loss of 3p per kWh you self-consume.

xewecan

Vast majority of solar panels are retro fit, without issue.

google solar panels and pigeons, there are solutions on the market, wire/mesh/reflective tape. Depending on chosen bracket the panels can sit close enough to roof for it not to be an issue.

You may want to research solaredge optimisers, which is like an individual inverter per panel.
Solaredge also offer an inverter with built in ev charger in one unit.