Solar Power - Definitely Green but is it affordable

MWT

[Deleted User] said:

The DNO will take at least a couple of months to review the submission and technical documents and it may - depending on your local electrical infrastructure - impose a max export limit. I was lucky and my export is not limited but there are reports of some people not being so fortunate. It just means that even if your array is capable of producing say 7 kWs max, your export may be limited to 5kWs. 

Just as a counter-point, my DNO approval took 3 weeks roughly from sending the letter to the DNO to receiving their approval.

A lot depends on which DNO I suspect, mine was UK Power Networks.

007apm

Thanks for all the responses.  My guess is that at some point in the next 5 years we will end up with an EV.  At present a 4x4 diesel estate can be bought for sub 35k.  A similar EV is 46k+ but as EVs become the norm, prices will merge.   The point on electric showers is well made.  The battery max to house is 5kw and i guess the solar gen runs in parallel but i will quiz the surveyor during their visit.  As I said earlier, even if all i did was to save 1 tonne of c02 in a year we have a winner, which seems to be the only 'guarantee...' 

QrizB

On another thread the OP wrote:

007apm said:

I am concerned by the relative increase in the standing charge.  I await an installation of solar panels/battery which might cut our electricity usage from 4000kwh to 500kwh pa from the grid but the increase in standing charge has a disproportionate impact  on low usage customers costs.  To encourage the green agenda, usage charges are more appropriate than fixed charges.  The need for help for fuel poverty however is independent of how bill is calculated.

Several of us have expressed doubts over your (laudable) goal of 80% self-consumption. Let's look at your system again:

007apm said:

Our Solar plan

In our case we have opted for a First 4 Solar system with a 6KW solar with a 7.6KWh battery.  We hope to generate 5,200 KWh per year and USE 80% of the energy produced which we hope will generate a £900 saving at current rates and take 12 years to pay for itself.  Clearly if the price of electric rises a further 50% then whilst costs actually rise, savings are greater and may pay for itself in 8 years.

If we assume the system is installled in the south-east of England, generating 5200kWh/yr should be possible. If I use PVGIS to model a 6kWp system just north of Brighton, with optimisation of slope and azimuth, I get a potential generation of around 5900kWh/yr. But the devil is in the detail; in July I'm generating 855kWh, in December only 46kWh.

Looking at your consumption of 4000kWh/yr, that's a flat average of 11kWh/day. Most people in the UK use more electricity in the winter than in the summer but let's imagine you don't.

• Over the 31 days of July you'll use 322kWh; if you generate 855kWh you will export 533kWh.
• Over the 31 days of December you'll use 322kWh; if you generate 46kWh you will import 187kWh.

In practice your average generation will be less than 11kWh/day during October, November, December, January and February.

PVGIS also has an off-grid modelling tool. Using your panel and battery sizes, plus a daily demand of 11kWh, the model suggests shortfalls in March and September too. As a rough estimate I think you'll be self-consuming 2800kWh, exporting around 2400kWh and importing around 1200kWh/yr.

That's 54% self-consumption and 70% grid-independence. Not too shabby but quite a lot less than the 80% / 87.5% you seem to be expecting.

007apm

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Generation estimate	200	300	440	580	700	680	680	620	500	340	200	160	5400
Use / month flat	330	330	330	330	330	330	330	330	330	330	330	330	3960
Surplus	-130	-30	110	250	370	350	350	290	170	10	-130	-170
From grid	130	30									130	170	460

From the provider's generation estimate we expect to generate 5400KWh on the profile above. we do actually have a relatively flat profile for usage because all the heating & water are gas at present.  It seems likely that we can use all the energy generated in the winter via the battery (in theory) however the real world often disappoints!

007apm

The solar panel and battery industry are in a difficult place, delays in obtaining panels and batteries mean that after much encouragement and a minor change to spec (410 W panels replaced 400W panels due to availability) we are now cooking on 'gas'. The panels look great and the little app on the phone showing real time generation / consumption is addictive! 

The weather unfortunately has yet to read the script and has been overcast since the system went live, so far we've peaked at 4KW generation and usually been nearer 2KW. I've been pleasantly surprised that generation goes  on well in to the evening and even at that has covered our daily usage.  10-11 KWh / day.  What has surprised me is that the battery has never dropped below 40% and yet we have imported ~2.5KWh per day from the grid.  The explanation given was that the response time of the grid is instant whereas the response time (deliberately) of the batteries is somewhat slower.  The explanation continued to say that this offers some protection to the batteries and extends their lives.  Based on the data from 2 days, it looks like 75% self consumption might be achieved in brighter months, but that will be as good as it gets. 

The next challenge will be to get Scottish Power to connect us up for SEG.  Looks like we have exported 3KWh/day to the grid but SP suggest a 3-4 week wait for a response to our application.  If the sun comes out... it could be a fair bit more :-)

Is a blog for this over then first couple of months useful to MSE readers?

MWT

007apm said:

What has surprised me is that the battery has never dropped below 40% and yet we have imported ~2.5KWh per day from the grid.  The explanation given was that the response time of the grid is instant whereas the response time (deliberately) of the batteries is somewhat slower.

Usually that level of import has more to do with peak demand exceeding the ability of the battery + solar (if in the daytime), so take a look at the data, if you have it, to review peak demand periods when perhaps someone turned on an electric oven while using a vacuum cleaner etc.

Do you know what the limits are on the battery in regard to the peak power demand it can support?

Edit: I see earlier you said 5kW was the limit on the battery supply, is that continuous or peak?

Magnitio

007apm said:

The next challenge will be to get Scottish Power to connect us up for SEG.  Looks like we have exported 3KWh/day to the grid but SP suggest a 3-4 week wait for a response to our application.  If the sun comes out... it could be a fair bit more :-)

Is a blog for this over then first couple of months useful to MSE readers?

It would be useful to know the full details of what equipment was installed and how it is configured if you have access to the parameters that control the charge/discharge of the battery.

I had to wait several weeks for SEG with Octopus to be set up during Feb/March when I exported 50kWh. I suspect you will export more than this over the next 3-4 weeks, but at least you know that a bit less gas/coal is being burnt somewhere.

MWT

Magnitio said:

I had to wait several weeks for SEG with Octopus to be set up during Feb/March when I exported 50kWh. I suspect you will export more than this over the next 3-4 weeks, but at least you know that a bit less gas/coal is being burnt somewhere.

I was in a similar position with Octopus, but when they did get the export MPAN set up, I got full credit for the export from a 0 initial reading, so nothing was lost.

007apm

Thankyou...
The inverter is a Fox ESS H1-5.0-E with 3x HV2600 Fox batteries.

The grid energy usage is in frequent almost random spikes to 0.03KWh overnight which add up to 1 KWh when we are sleeping.  Oddly there is battery power available.  Other spikes have been using the washing machine at 10am when the system charged the battery in preference and used grid energy for the washing machine.

Week to 4th May we:

• Used 10.46KWh / Day 
• Downloaded 2.73KWh / Day from the grid
• Generated 121KWh (min  10.8, max 38.8, average 17.34)
• SEG donation 66.8KWh (min 2.1, max 28, average 9.54)

Given that there was only one sunny day, we are still net contributors to the grid :-)

Reed_Richards

007apm said:

...What has surprised me is that the battery has never dropped below 40% and yet we have imported ~2.5KWh per day from the grid.  The explanation given was that the response time of the grid is instant whereas the response time (deliberately) of the batteries is somewhat slower.  

This is certainly true of my solar/battery system (and I have mentioned it often enough elsewhere on this forum).  There is also the converse where the battery is discharging, the demand switches off (suddenly) and the battery exports unnecessarily to the grid in order to ramp down its output.