Renewables: "talking 'bout my generation"

EricMears

Oscargrouch wrote: »

Is it possible that a 2.5 kW system can peak higher than 2.5?

If you mean 2.6, maybe even 2.8 then eminently possible - though unlikely you'd keep it up for long. If you were hoping for 3.0 or more then highly unlikely.

EricMears

A much better generation day here. 21.24 Kwh so far and system still pushing out 4 watts.

As usual, looking at the generation curve I can dream of better days. Reached several peaks of over 3Kw between 10 & 4 and a couple around 3.8 just after (proper) Noon. Alas, many dips too - e.g. dropped right down to 450w at 13:45

Collected no rainwater at all today - just as well really as all storage tanks full.

WestonDave

Bit better day today - 15.6 and drifting to a close now. Did see a 3.75 spike just before mid day, which won't show on the data log as it was only momentary, but with us theoretically being split aspect, that's pretty close to all panels giving their all at once!

Had some good conversations with neighbours over the weekend at the jubilee festival in our "village" - the perception that it costs £15k for a system is going to take some hard work to beat out of people's mindsets!

Oscargrouch

Martyn1981 wrote: »

What did you see?

Mart.

This has me baffled; doesn't take much; today my inverter shows a peak of 3.001kW today - highest peak todate 3.203kW. I never take readings from the monitor, as they are always higher than the actual Gen Meter. The installed system is a 2.5kW; Inverter is the Power-One Aurora Outdoor Max 4kW. Perhaps I am misinterpreting the reading from the inverter. I know Power-One are having problems with the Aurora Monitor as mine is currently being replaced under warranty, it lost track & could not cope with February the 29th! Generation today was 10.6kWh:eek:

Martyn1981

Oscargrouch wrote: »

This has me baffled; doesn't take much; today my inverter shows a peak of 3.001kW today - highest peak todate 3.203kW.

That's pretty impressive Oscar, I wasn't expecting numbers that high.

Similar chat here, when I was taking the mick out of RoxyK

Martyn1981 wrote: »

Sorry, can I just re-cap. You've seen 4.457 from a 3.84 system, with an under-reading inverter - and you're looking forward to an interesting April!!!!!

Some people want the Moon on a stick!

M.

Roxy was over by a similar amount to you, but on a bigger system.

Maybe it is over-reading a bit, but you will see some strange numbers at times when the panels get to cool down a bit (this only only takes a few minutes when a cloud passes over).

Did you manage to put the kettle on in time to use it?

Mart.

Oscargrouch

Martyn1981 wrote: »

That's pretty impressive Oscar, I wasn't expecting numbers that high.

Did you manage to put the kettle on in time to use it?

Mart.

Unfortunately not, I do not have a stand alone monitor at the mo, so I have to look at the inverter in a hall cupboard. Bye the time I do that, I keep missing the high peak.:rotfl:

It does make sense now though, the inverter is telling ‘porkies’, hence the reason it gives a total generation figure, greater than the export meter. Which is why I always use the meter to log my readings; it would appear that some monitors are merely there as a rough guide. :beer:

Kernel_Sanders

Martyn1981 wrote: »

So, fitting panels on both E&W roofs doubles the potential size, but for a lot, lot less than double the cost.

I must disagree as to the extent of the savings due to fixed overheads. Scaffolding costs should (almost) double, plus the inverter will have to be uprated not only in terms of kWp but also in needing two strings.

EricMears

Kernel_Sanders wrote: »

I must disagree as to the extent of the savings due to fixed overheads. Scaffolding costs should (almost) double, plus the inverter will have to be uprated not only in terms of kWp but also in needing two strings.

Certainly increase but not double - or even almost double.

e.g. one 4Kw inverter will be cheaper than two 2Kw models. Much of the cost of scaffolding is in overheads and the gang shouldn't need to make twice as many journeys as usual to erect or dismantle.

Martyn1981

Kernel_Sanders wrote: »

I must disagree as to the extent of the savings due to fixed overheads. Scaffolding costs should (almost) double, plus the inverter will have to be uprated not only in terms of kWp but also in needing two strings.

Hiya Kernel.

It’s still going to be a lot less than double the cost, in fact just the examples you gave show big savings.

Researching scaffolding, (for wall tie replacement for a friend), was roughly £400 for one face, then £200 for each additional face, so that’s a 50% increase, for 100% more roof access.

Re-checking the voltage limits on the SMA inverters, and I found that the string voltages for the SB TL range 3600, 4000 and 5000 are all the same. In the example I gave of 3.2kWp and 2.1kWp on each roof that was based on strings of 12 and 8 YingLi Panda 265W panels. All three inverters can cope with 2 strings of 12, though Sunny Design warns that the 3600 is at the bottom of suitability (it doesn’t know I’m considering 2 opposite aspects).

I haven’t priced them properly since I don’t have access to trade prices, but one site has the inverters at £1,071, £1,122 and £1,297 respectively. A 4kWp south system may already use the 3600 or 4000 model so no increase. Upping it to the 5000 for a little headroom (though all 3 would have 3,680W caps for DNO approval) would therefore only add 10 to 20% to costs. For the example I gave of 3.2 + 2.1 I can’t see any reason to go above the 4000 model. Additionally, by 3kW most inverters will have dual MPPT’s, and I believe all (nearly all?) will have, or be operating on 2 strings.

Roofing labour, rails, fixings, panels etc would be double. But electrical work inside the house would still only be one inverter and mirror identically a 4kWp south system.

Quotes I’ve been looking at ‘only’ go up by approx. £1 per watt installed after 3kWp. Very rough estimation, but looking at the extreme example of 24 panels, approx. costs would be £5k for 3kWp and £8.5k for 6.36kWp.

So that’s a 112% increase in kWp, with a 70% increase in costs. To go back to my original argument that this could help to re-dress the balance between south and non- south systems. The E/W split would be approx. 15% less efficient, making the 6.36kWp system equivalent to a 5.4kWp south system. 5.4kWp is an 80% increase over the 3kWp system for 70% increase in costs. Also remember that few roofs could cope with a South system of that size, and that running off of one aspect would cause it to bump against the 3.68kW cap on a regular basis.

Obviously Fit rates are also affected, but I’m thinking long term.

Just trying a few mental exercises to see where PV could go in the future, and I’m more and more convinced that not having a true south aspect is not necessarily a handicap. Also remember that panel prices are dropping, but most of the other costs aren’t, so the benefits of a larger system cost wise and through a wider generation period should grow larger with time.

Hope this makes sense, and isn’t too long. Also, all my own numbers, bouncing around in my busy little brain, so not necessarily correct.

Mart.

mpn226

EricMears wrote: »

Certainly increase but not double - or even almost double.

e.g. one 4Kw inverter will be cheaper than two 2Kw models. Much of the cost of scaffolding is in overheads and the gang shouldn't need to make twice as many journeys as usual to erect or dismantle.

just looked at my readings for today 5/6/12 15.8kw and 25.8kw from my 2 systems great day in the highlands LONG may the sun shine:beer: