Renewables: "talking 'bout my generation"

EricMears

A FIT 'quarter-day for me today.

Definitely the worst ever quarter - though of course that's really only saying "worse than same quarter last year" as all the other quarters include longer days so would be better.

260 kWh this quarter compared with 318 last year.

Earnings of £122 still comfortably pass my £1 a day ISA interest test (which incidentally has just dropped to 90p per day :mad: ) and are (just) greater than 3 monthly DDs to ScotsPower though alas fall well short of the cost of electricity we've actually bought this quarter.

It's also a good time to review Februaty as we've had 14 days of it with 14 left to come. Generation this half-month has been 52.7kWh compared to a PVGIS forecast of 150 for the full month.

Main problem has of course been snow where we've had several days of near-zero output followed by another couple where snow has been slow to fall completely off the shallow panels. It would have been relatively easy to climb a ladder and flood area from a hosepipe but really not worth it for the sake of earning a couple of pounds a day. I would do that if it snows in June

tunnel

Dave_Fowler wrote: »

System 2 is monitored on-line where the output of the inverter and each of the panels is shown.

First observations show that System 1 starts up earlier in the morning than system 2 and produces a few Watt hours before system 2 starts. Checking on-line I find that not all the power optimisers start up in low light. The specifications say that there must be 8 optimisers in a string before there is an output.


The effects of snow has been interesting. When the snow started to slide off the top string of system 1 (about 20% of the top 8 panels was visible), system 1 'woke up'. The power optimisers of system 2 did not wake up until most of the snow was off the panels.

System 2 has 2 panels in landscape format and the other 10 are in portrait. As the snow slid off, the optimisers on the landscape panels woke when there was about 80% of each panel uncovered (there was a 20% coverage along the lower long edge). The portrait panels needed virtually all the snow cleared from their lower ends before the optimisers worked. I suspect this is something to do with the internal connections of the solar cells.

One experiment I was able to do on system 2 was to remove the snow from individual panels (I can easily gain access to system 2 panels) and watch the effects on-line. When I removed the snow from 6 panels, the inverter was able to start up and produced an output of about half of what I would expect from the total 12 panel array. When the eight panels in the top half of system 1 were free of snow I was still only getting a few hundred Watts - the other eight snow-covered panels were 'shorting out' the working panels.

.

Dave F

Thats quite interesting Dave,My SW panels are currently 1 string on a SB inverter,i've been looking at swapping and changing to a solar edge with the individual PO's but from what your saying they still have to fire up together to get the inverter going.

Mine become gradually shaded from 1 end to the other late afternoon,if what your saying is right then i'd have no advantage in swapping over,presuming once the first couple have gone dark then the others would follow suit. Am i grasping this right?

Tunnel

Martyn1981

tunnel wrote: »

Thats quite interesting Dave,My SW panels are currently 1 string on a SB inverter,i've been looking at swapping and changing to a solar edge with the individual PO's but from what your saying they still have to fire up together to get the inverter going.

Mine become gradually shaded from 1 end to the other late afternoon,if what your saying is right then i'd have no advantage in swapping over,presuming once the first couple have gone dark then the others would follow suit. Am i grasping this right?

Tunnel

Hiya Tunnel, I think the issue is enough daylight to fire up. Even panels in the shade will still be running, but at low levels that drag down their teammates, so the SE PO's allow the remaining panels to run at max (well, whatever good sun they have) unaffected by those panels only generating a few watts - As long as enough shaded panels are generating 'a few watts'.

So in your example, as panels go into the shade, they will still be generating a little, unlike panels trying to operate at their very minimum sun levels early and late in the day.

Another way of thinking about it, in the morning my WNW get no direct sunlight, in the late afternoon the ESE gets none, but they all generate all day (with a little daylight) once they've reached minimum start up levels.

Phew .... does that make any sense?

Mart.

Dave_Fowler

Hi Tunnel, Mart is absolutely right. It is only at very low light levels where the POs do not start up. I probably lose around 5 or 6 Wh a day because of the later start-up of some POs. However, as soon as there is some more light - where my system 1 may be producing 50 or 60 Watts - system 2 fires up on sufficient panels to soon overtake the output of the other system.

At this time of the year, system 2 suffers from a lot of shade in the afternoon from the house. Currently over half of the panels are in complete shade. None of the POs are anywhere near shutting down. The advantage of the POs is that those that are producing much less power still contribute to the overall output and their panels do not reduce the output from the other fully lit panels as would be the case in a conventional system.

Dave F

tunnel

Dave_Fowler wrote: »

Hi Tunnel, Mart is absolutely right. It is only at very low light levels where the POs do not start up. I probably lose around 5 or 6 Wh a day because of the later start-up of some POs. However, as soon as there is some more light - where my system 1 may be producing 50 or 60 Watts - system 2 fires up on sufficient panels to soon overtake the output of the other system.

At this time of the year, system 2 suffers from a lot of shade in the afternoon from the house. Currently over half of the panels are in complete shade. None of the POs are anywhere near shutting down. The advantage of the POs is that those that are producing much less power still contribute to the overall output and their panels do not reduce the output from the other fully lit panels as would be the case in a conventional system.

Dave F

So with half the panels in shade your producing roughly 50% than if all were in sun. Don't have a problem with start-up,just shading late afternoon. Me thinks i'll have to price it up.Plus, does anyone know if you have to inform MCS as the original inverter is registered as is with my FITS provider?

I'll get my generation in too,5.95 ESE and 5.4 SSW. Reckon the SSW even at this time of year could have been another 1-2kWh with a different set up. The mind ponders:(

Tunnel

InVestor_2

11 kWh today

Had the Immersion on for about 90 minutes, and halogen heater warming the house for the rest of the day. Also, 2 wash loads.

All free

legoman62

6.21kWh today
System kicked in at 07.40 on 12W.. still going at 1705 with 3W:D
Well it all helps!
Peaked at 14.15 on 2.6kW
Not that I'm checking:rotfl:

Martyn1981

tunnel wrote: »

Plus, does anyone know if you have to inform MCS as the original inverter is registered as is with my FITS provider?

Tunnel

Don't know, but very interested to find out if anyone does know.

For FITs it's the kWp of the panels that's important.

For the DNO's it's the max possible kW output of the inverter (taking the panels into account). They were more relaxed at the start, but have gotten pretty serious now about the rules.

So less than 3,680Wp of panels, no problem, and a 3.68kW limited inverter with any amount of panels, no problem. But an unlimited inverter ....hmmm. WPD (my DNO) want you to multiply the panels by the inverter efficiency, so 4kWp ok if inverter (unlimited) is 92% (or less) efficient. So possibly if you replaced such an inverter with one more efficient then you may need prior approval.

However, in reality, most inverters of approx 4kW will now be capped to 3.68kW, so probably irrelevant.

Logic makes me think swapping one inverter for another of the same size should be ok, but after my experiences with OFGEM (EPC extension rules!) I wouldn't trust to logic.

As I had to provide WPD with PDF's of the G83/1 certificates for all of my inverters to get my extension, it has crossed my mind that changing models in the future may require their approval!!!!

Got 10.4 today, my first day this year over 10. Tidy!

Mart.

shafeeq

7.53 kwh today. .. Oh well Oscar you will have a great laugh today A
again. ....

Oscargrouch

Nice little 6.0 kWh here........:T Tidy.:D