Solar Panels

QrizB

scarletjim said:

Thanks for the little tutorial and link - I've certainly learned a lot more than I normally would on a Friday afternoon, that's for certain!

What you can also do is look on PVOutput for a system near you.

The UI on that site isn't the greatest so I've just found an example of an (almost) 6kWp system in the Midlands with records going back several years: Sid's Pipe

This will give you examples of day-by-day generation in the UK.

scarletjim

QrizB said:

scarletjim said:

Thanks for the little tutorial and link - I've certainly learned a lot more than I normally would on a Friday afternoon, that's for certain!

What you can also do is look on PVOutput for a system near you.

The UI on that site isn't the greatest so I've just found an example of an (almost) 6kWp system in the Midlands with records going back several years: Sid's Pipe

This will give you examples of day-by-day generation in the UK.

This is fascinating... So here is what I've done now:

I've input the details of a typical system at my location and direction etc into the JRC site that you linked earlier, then I've taken the stats from 4 systems in my county with same direction, elevation etc, adjusted their data for different system size where appropriate, and compared to the figures from the JRC site. All in all, they are pretty comparable, though the 'actuals' from the 4 local examples suggest lower production in Oct-Jan than my estimates had suggested, and higher production in June-July. Of course this is a very small sample of just 4 systems, and with data from just 3 or 4 years for each. In any case I've adjusted my own estimates for the average difference compared to those 4 systems, and that gives more conservative numbers for my estimate. I then calculated my surplus / deficit based on known usage from the last few years of data for our house, based on having a battery to enable night use (will cost that shortly). The results surprised me:

• I would use 82% of what I generate - 100% Oct to Feb, over 90% Aug, Sep and Mar, then about 60-75% Apr to Jul. Does that surprise you?
• I would save about £1,500 on electricity bills as a result.
• I would only make about £50 from what I sell back - but that's ok, that's not where the real benefit is.

All of that sounds very positive, until I consider the battery size and cost. If one of the key components of my plan is to use all the electricity I produce in the summer months, then presumably I will need a sizeable battery to achieve that. In July / August we often exceed 20kwh per day, and given that the air-con is on at night, looking at my energy provider data, I reckon half of that is between (say) 10pm and 5am. Does that mean I'd need a 10kwh battery? If so, those look extremely expensive, and may well cause the whole idea to fall down.

This would take me back to considering it without the battery - this is more difficult to estimate, as the energy provider data is unclear (their hourly breakdown comes to almost twice the daily total kwh for any given day!), plus I don't know how which hours I can assume will use the generated electricity versus those that won't and will need to take it from the grid.

How can I estimate which HOURS in which months will generate electricity for me to use?

Alnat1

Very difficult because of the British weather. For example on the 9th July my panels produced 32.9kWh, today they've made a miserable 3kWh.

When you have no way of knowing how much you'll produce on any given day, it's even harder to say by the hour.

scarletjim

Alnat1 said:

Very difficult because of the British weather. For example on the 9th July my panels produced 32.9kWh, today they've made a miserable 3kWh.

When you have no way of knowing how much you'll produce on any given day, it's even harder to say by the hour.

Yes I suppose it's relatively predictable over the space of a whole year, but totally unpredictable and indeed inconsistent on a day-to-day basis, thereby making it impossible to make best use of the energy produced every day. Oh well, I'll keep looking / thinking, maybe battery prices will come down in due course.

Alnat1

I only had my system fitted this March and prices have seen a huge rise in just those few months.

The installers are so busy they are booked up for months now and people are even finding it difficult to get companies out to quote.

Evan3020

Had my solar panels nearly 7 years, cost £6000 (4Kw) and paid me back £4500 so far in FIT payments and produced 27 MWH.
When then the 65% increase kicks in i will be saving £1000 per year on top of my £800 a year FIT payments.
I generate around 4150 kwh a year and use around 2400.
As the price of electricity increases the economics get better.
Would love a wind turbine as well but they don't seem to work well on a small scale.

QrizB

Evan3020 said:

Would love a wind turbine as well but they don't seem to work well on a small scale.

The best way to take advantage of wind is via investment in a commercial wind farm. You can do this directly eg. With Ripple or you can buy shares in eg. Green coat UK Wind.

Sorry no links, posting from my phone.

Disclosure: I have a small stake in both named schemes.

Evan3020

I have heard of ripple and will have to read up a bit more on it.

markin

With solar you would want to run the AC all day anyway so come night it hardly has to work, if you let heat build up it stores in the bricks and will release over night, But i really don't believe the best way to run AC is hard at full wack just before bed, Vs light duty keeping the temp steady all day. They modulate down the power as needed, They don't use the full rating every hr they are on.

I'd guess your ac usage 24/7 for 60 days would be 480kwh, At 8kwh a day

scarletjim

markin said:

With solar you would want to run the AC all day anyway so come night it hardly has to work, if you let heat build up it stores in the bricks and will release over night, But i really don't believe the best way to run AC is hard at full wack just before bed, Vs light duty keeping the temp steady all day. They modulate down the power as needed, They don't use the full rating every hr they are on.

I'd guess your ac usage 24/7 for 60 days would be 480kwh, At 8kwh a day

Hmmm that's a good idea. Question related to that though: Will I know definitively when I switch each evening from using my generated electricity to grid electricity? Can you get it to notify you daily etc, or does it not work like that?