Renewables: "talking 'bout my generation"

jackieblack

8kWh here (3.6kWh/kWp)

teachergirl

Looked back about 5 pages...no idea what an O is?:think:

tunnel

An "O" is that annoying little itch that you cant get rid of or just cant reach:rotfl: Sorrry oscar,only kidding..3.1 "O"s for me today,about the same as yesterday.

Martyn1981

teachergirl wrote: »

Looked back about 5 pages...no idea what an O is?:think:

O's stands for Oscar's, we're trying to make him famous!

3.2'O's for me (17.9kWh's/5.58kWp)

Mart.

InVestor_2

19.1 kWh today

Lots done for free

edwink

Martyn1981 wrote: »

O's stands for Oscar's, we're trying to make him famous!

3.2'O's for me (17.9kWh's/5.58kWp)

Mart.

Oscar is famous! Have you not seen him on Sesame Street?

We generated 7.69kWh today.

Edwink

legoman62

Weatherman was right today
Sun in the morning and cloudy afternoon
Made 2.5 '0's:D

Oscargrouch

teachergirl wrote: »

Looked back about 5 pages...no idea what an O is?:think:

An O is kWh/kWp simples.....;)

InVestor wrote: »

19.1 kWh today

Lots done for free

Ooo, what's happening, lost track of that; is that good or bad? Could you explain that in UK O's please....

Certainly glad I have a 2.5kWp system feeding an Inverter rated at 3.6kW...some time this year my Inverter shows an input of 3.257kW for an unknown period. I like toast in the morings, not for lunch.

edwink wrote: »

Oscar is famous! Have you not seen him on Sesame Street?

We generated 7.69kWh today.

Edwink

I would just like to quantify the above comment: A character in the above mentioned programme was perhaps modelled on me...

jackieblack

Oscargrouch wrote: »

Certainly glad I have a 2.5kWp system feeding an Inverter rated at 3.6kW...

Interesting
When I was getting quotes for my system, I had been quoted for a Fronius IG30 inverter, which the installer was then having problems getting hold of so, a few days before the installation was due, I was being offered various alternatives, one of which was a Fronius IG20. I didn't feel that I knew enough then to make a confident decision so I emailed Fronius, gave them all the details of the roof, location and panels, and this is the reply I received

"That array is perfect for an IG20. There are not enough panels to run an IG30 so this would be a very poor choice - I presume this was a simple mistake when they were quoting the job for you."

My understanding was/is that a smaller inverter will run more efficiently during periods of less than maximum generation, (which are likely to far exceed periods of maximum generation) thus compensating for the slight reduction in output during the (far fewer) periods of maximum generation.
Is this not correct?

Fronius tech data

Martyn1981

jackieblack wrote: »

Interesting
When I was getting quotes for my system, I had been quoted for a Fronius IG30 inverter, which the installer was then having problems getting hold of so, a few days before the installation was due, I was being offered various alternatives, one of which was a Fronius IG20. I didn't feel that I knew enough then to make a confident decision so I emailed Fronius, gave them all the details of the roof, location and panels, and this is the reply I received

"That array is perfect for an IG20. There are not enough panels to run an IG30 so this would be a very poor choice - I presume this was a simple mistake when they were quoting the job for you."

My understanding was/is that a smaller inverter will run more efficiently during periods of less than maximum generation, (which are likely to far exceed periods of maximum generation) thus compensating for the slight reduction in output during the (far fewer) periods of maximum generation.
Is this not correct?

Fronius tech data

It is correct. Please don't get worried by Graham's 'exploding inverters', this is very much a personal thing, in response to my mythbusting his many anti PV/FITs statements throughout 2012.

In fact, if you read his post here, you'll see he regurgitates most of the comments I, Don and Zeupater made in the link he provided yesterday, in fact his comments (now) seem quite supportive of slightly undersizing:

grahamc2003 wrote: »

There is a small gain at the low end to offset (or perhaps exceed) the loss at the high end. The small rated inverter will synchronise at a lower open circuit voltage than a higher rated one. So while you're generating, a higher rated inverter will still be waiting for a higher voltage (and this at both ends of the day). A small gain, except when the weather is marginal and the smaller one just synchronises while a larger one wouldn't.

The trick he used Feb 2012 in order to introduce the inverter failure paragraph, was to move the discussion from moderately undersizing, to over-voltage. The two aren't automatically linked, overvoltage would result from an installer fitting the wrong inverter and panel package, or from wiring up too few strings. For instance some 4KW inverters are designed to operate with two strings from a 4kWp array, so would be overvoltage with a single string, others are designed to operate at higher voltages with a single string. So overvoltage here would be the installers error, not the inverter to panel ratio.

I was so concerned at those posts that I sought clarification from SMA themselves, but the 'twist' Graham had used made it tricky for them to act, here is what they said to me:-

"I have read the various posts and decided its worth following up but as Graham states what is written in the manual is correct there seems we cannot do a lot about it, however if he wants to continue SMA may write him a nice legal letter."

As the matter had, by then, gone cold, I didn't want to raise it again, since that would have only caused further concerns. If anyone is still concerned, I'd suggest asking on the 'renewables installer thread' so that Energetic can explain in more detail.

Note: SMA recommend an inverter to panel kWp sizing of 85% to 120% depending on where (in the world) it is being located, and have made their design software 'Sunny Design' free to download, to help with this.

Mart.