Renewables: "talking 'bout my generation"

sly_dog_jonah

Martyn1981 wrote: »

With an E/W split, I think my theoretical is about 6.5 O's, but requires cold air temp.

Anyone else jealous of 8.12 O's from a 3+yr old system?

http://www.navitron.org.uk/forum/index.php/topic,20278.0.html

Mart.

Not really jealous no, his roof angle (11deg) is optimal for this time of year but sub-optimal for the rest of the year. According to the table quoted in John_Pierpoint's post the optimal angle for annual generation is 30-40degrees.

legoman62

After seeing Tues forecast for wall to wall sunshine what did we get?
Great until 15.30 generating 3kWh+ then cold with low cloud and dropped to 1kWh for the rest of the day.
Ended the day with 5 O's:D

Forecast for today is cold and cloudy here...spot on up to now unfortunately:(

sly_dog_jonah

Wh05apk wrote: »

Best day so far (only had the system 4 weeks!) but got 27.54 or 7.48 "o's" very impressed, couldn't use enough power during the day though! must get aircon for my south facing office - seems an ideal way to use power, as only needed when hot and sunny, which will be when we are producing, looking good again today.

Are you using your inverter capacity or total installed panel capacity to calculate your O's? Based on the above figures it looks like you have a 3.68kW rated inverter, but another posting suggested you had 4kWp of panels installed? For better comparisons most posters of 'O's generally use the panel capacity to divide the generation. In our case it's a small difference - 3.7kWp versus 3.68kW inverter rating but for those with significantly undersized inverters the calculations will be skewed if you use the inverter capacity in the O's calculation.

EricMears

sly_dog_jonah wrote: »

his roof angle (11deg) is optimal for this time of year but sub-optimal for the rest of the year. According to the table quoted in John_Pierpoint's post the optimal angle for annual generation is 30-40degrees.

11 deg will always be 'sub-optimal'. Optimal on Summer Solstice day would be approx. 30 deg (your latitude minus latitude of Tropic of Cancer if you want a precise figure). On Winter Solstice day it's nearer 75deg.

A flatter roof gets a contribution from the hour or so each end of day when the Sun appears North of the East-West line so roof ridge might shade the panels - but this is a very small contribution (probably less than 100W)

Optimal angle for annual generation would be obtained from a very complex formula considering likely generation on every individual day and calculating a weighted average. But you can simplify that by saying generation is so much greater on SS Day that the optimum must be a lot closer to that than to the WS Day angle.

Wh05apk

sly_dog_jonah wrote: »

Are you using your inverter capacity or total installed panel capacity to calculate your O's? Based on the above figures it looks like you have a 3.68kW rated inverter, but another posting suggested you had 4kWp of panels installed? For better comparisons most posters of 'O's generally use the panel capacity to divide the generation. In our case it's a small difference - 3.7kWp versus 3.68kW inverter rating but for those with significantly undersized inverters the calculations will be skewed if you use the inverter capacity in the O's calculation.

Yes using the inverter capacity, so if using panel capacity "only" 6.9 "o's"

What is the "preferred" figure to use?

Oscargrouch

John_Pierpoint wrote: »

I note that the poster is quoting his inverter, which might have an inflated opinion of itself, not the generation meter, which is the acid test.

[It is a bit like cars and MPG figures ?]

I have noted on some occasions my Aurora sometimes adds yesterdays gen number to todays and or misrepresents by 3 or 4 kWh, so you are correct John in your remark, " Generation Meter is the Acid test".

Oscargrouch

Wh05apk wrote: »

Yes using the inverter capacity, so if using panel capacity "only" 6.9 "o's"

What is the "preferred" figure to use?

Total Panel Rate...:)

KevinG

Oscargrouch wrote: »

Total Panel Rate...:)

I'll second that, been discussed and agreed before. If I used the maximum rated output of my inverter, which is 1575W, my O's would be 27% higher and my all-time record would be 8.35!

sly_dog_jonah

Wh05apk wrote: »

Yes using the inverter capacity, so if using panel capacity "only" 6.9 "o's"

What is the "preferred" figure to use?

I've always quoted based on the 3.7kWp of the panels, rather than inverter rating.

I reckon Oscargrouch should include a one line definition of 'O's in his signature to avoid confusion.

Oscargrouch

KevinG wrote: »

I'll second that, been discussed and agreed before. If I used the maximum rated output of my inverter, which is 1575W, my O's would be 27% higher and my all-time record would be 8.35!

I would be in worse trouble; my inverter is rated 3.6 which would have given me 5.11 O's for yesterday, we can't have that !!!

Below shows how economical with the truth Inverters can be.....not bad from a 2.5kWp system. Taken 12:00 today, showing the highest peak todate with todays highest below it.....:rotfl:






Just checked the graph for yesterday in Holmes, highest panel output was between 15:15 - 15:30; lasted 15 mins and equalled 2.121kW, which makes sense from a 2.5 kWp system. So much for Inverter calculations.