Inverter Temperature Derating

[FB.]

so the answer is yes? -the cooler you can make run the inverter, the more efficient it is.
Has anyone got this graph please?

The Power One Aurora family of inverters are roughly as follows:

Air temperature / output

35-40'C: no loss of output (cooling fan gradually increases its speed to cool the internals).
40-45'C: 5-10% loss of output
45-50'C: 15-20% loss of output
50-55'C: 30-40% loss of output
>55'C: major power reduction and risk of shutdown due to overheating

It is also recommended to avoid mounting in direct sunlight as the inverter casing will absorb sun/heat and get hotter than if the inverter is in shade or in a loft/garage/utility room etc.

 

[FB.]

so the answer is yes? -the cooler you can make run the inverter, the more efficient it is.
Has anyone got this graph please?

And the SMA/SB family of inverters state an operating range up to 60'C, so probably fairly similar to the Power One family.
Unfortunately I couldn't find more specific temperature-derating data.

 

[mdovey]

And the SMA/SB family of inverters state an operating range up to 60'C, so probably fairly similar to the Power One family.
Unfortunately I couldn't find more specific temperature-derating data.

Err, you could look at the link I posted a few posts back!

 

[sambotc]

I've seen the cooling fans running in January when the sun was out, but still cold in the loft (2.4-2.7kw production). It's the process itself rather than the ambient temp in the inverter location (although this will no doubt have an effect)

Presumably the fans will use a small amount running full whack as well, so there will also be a slight loss because of this?

 

[Gavin A]

You can find the temperature derating graphs for the various SMA inverters here - http://files.sma.de/dl/1348/Wirkungsgr_Derat-TEN112110.pdf

In general below an ambient temperature of 40 degrees the inverter will be running at its maximum efficiency for the input of the panels. Above 40 degrees ambient temperature you may see derating (exactly how much above depends on the inverter model) but you should get a warning (on the inverter display, on a sunny beam etc) when this happens. If you aren't getting this warning there isn't much point cooling the inverter from a performance perspective. Cooling may help lengthen the life of the inverter, however.

So HF and TL inverters generally shouldn't derate even in warm UK lofts (as long as the temperature stays below about 50), but the SB series aren't so good, with some derating from as low as 30 degrees.

I think somewhere in the mists of time I'd seen those graphs before and reached the same conclusion, which is partly why we've mostly been installing HF and TL inverters, but I'd then no found the document again so I couldn't remember the specifics.

 

[Gavin A]

The Power One Aurora family of inverters are roughly as follows:

Air temperature / output

35-40'C: no loss of output (cooling fan gradually increases its speed to cool the internals).
40-45'C: 5-10% loss of output
45-50'C: 15-20% loss of output
50-55'C: 30-40% loss of output
>55'C: major power reduction and risk of shutdown due to overheating

It is also recommended to avoid mounting in direct sunlight as the inverter casing will absorb sun/heat and get hotter than if the inverter is in shade or in a loft/garage/utility room etc.

do you know if that's true for both the indoor and outdoor versions?

useful to know that they start derating 10 degrees lower than the TL series sunny boy inverters, and so aren't as good for loft mounting.

 

[rgf1]

Gavin, can you tell me more about the Power One Aurora family of inverters. I am also finding the maximum power is far less than I expected. I now have learned from the forum that this is inevitable in very how ambient temperatures.

I can find nothing on the 3.6 Kw Aurora about cooling fans - I have also found an advert by them saying there is not fan. Who is right?

 

[FB.]

do you know if that's true for both the indoor and outdoor versions?

useful to know that they start derating 10 degrees lower than the TL series sunny boy inverters, and so aren't as good for loft mounting.

Yes, the indoor (fan cooled) and outdoor (heat-sink/fin-cooled) versions may see a reduction in output from 40'C air temperature.

But I suspect that it would be somewhat modified by the amount of DC power being processed at any given time, since that is also heat-generative within the inverter.

Knowing the manufacturers and the need to put a positive sales spin on their products, I would suspect that the >40'C temperature-induced power derating occurs at relatively low power throughput, and probably the inverter could de-rate at 35'C ambient temperature if it was running close to full capacity and therefore generating a lot of heat within itself.

 

[FB.]

Gavin, can you tell me more about the Power One Aurora family of inverters. I am also finding the maximum power is far less than I expected. I now have learned from the forum that this is inevitable in very how ambient temperatures.

I can find nothing on the 3.6 Kw Aurora about cooling fans - I have also found an advert by them saying there is not fan. Who is right?

The PVI-3600 and PVI-2000 indoor models use a cooling fan.

The PVI-3600-OUTD (outdoor) models use cooling fins/heat sinks; more suitable for dusty places like lofts, or, apparently, mounting in shady locations on the exterior of a building, since without a cooling fan they don't get clogged-up with dust (although the cooling fins may need occasional wipe with a duster).

 

[FB.]

do you know if that's true for both the indoor and outdoor versions?

useful to know that they start derating 10 degrees lower than the TL series sunny boy inverters, and so aren't as good for loft mounting.

For info, though, my PVI-3600 indoor model had the following performance efficiency at different ambient temperatures:

Indoor utility room temperature about 15'C (early April, mid-morning at peak generation)
Power in: 3.90kW
Power out: 3.66kW
Efficiency: 93.8%

Indoor utility room temperature about 25'C (in recent days, early afternoon, after peak generation but as temperatures are rising after mid-day)
Power coming into inverter: 2.90kW
Power going out of inverter: 2.71kW
Inverter efficiency: 93.4%

So no noticeable de-rating at 25'C air temperature (in the room where the inverter is located) when running at 80% capacity.

The 0.4% difference is probably merely down to inverters tending to run more efficiently the closer they get to their maximum rating.

 

[rgf1]

Thanks to FB for his quick and cogent reply.

My Aurora 3.6 OUTD is clearly is an outdoor model, installed in a completely dry, fairly dustproof stables - in the tackroom where the saddles, horse tack is installed. There is little evidence of any of the fins being clogged be contaminated by dust. My question is, how do I clean the finned heatsink if it needs it. Can I remove the outer case? or is there a simple method using a nozzle on a vacuum cleaner. (Has anyone fitted the fan off the indoor model and, can it actually be fitted, or has anyone fitted a simple external fan - like a computer fan and does this work enough to compensate its losses?)

The temperature of the heatsink does run about 60 degrees C - this is the temperature displayed on the screen. Is this the temperature used to measure and therefore control the derating or is the derating temperature at the measured at the internals of the unit?. In my manual it says - page 83 - full power is guaranteed up to ambient temperature of 55 degrees C.

Also, another question for the gurus of the forum to get their teeth into. Maybe this is another thread, or there already is a thread on this - please redirect me if so.

Page 81 of my manual - which is PVI-3.0/3.6/4.2-OUTD-UK Rev 1.0 states that the maximum recommended output is 4150 W - the absolute maximum I have ever recorded is a consistent 3984 W - this must be a clipped output as in the winter I get this value every sunny cold day.

Questions:

1. Why can I not get 4150 W
2. Is the inverter clipped to this to meet the UK regs.
3. If so how can the clipping be removed.

Many thanks to all replies

rgf1

 

[FB.]

Curious.

On the copy of the manual I'm looking at, page 83 has no temperature data.

But on page 90, the OUTD manual says:

"....

AURORA ensures top power up to 40°C ambient temperature, as faras it is not directly exposed to the sun......"

But on page 25 it says:

Temperatures exceeding 45°C for the PVI-4.2, 55°C for PVI-3.6
and 55°C per PVI-3.0, may result in power derating.
Output power derating is more likely to occur in case of high output
power and high ambient temperature.

 

[FB.]

Thanks to FB for his quick and cogent reply.

My Aurora 3.6 OUTD is clearly is an outdoor model, installed in a completely dry, fairly dustproof stables - in the tackroom where the saddles, horse tack is installed. There is little evidence of any of the fins being clogged be contaminated by dust. My question is, how do I clean the finned heatsink if it needs it. Can I remove the outer case? or is there a simple method using a nozzle on a vacuum cleaner. (Has anyone fitted the fan off the indoor model and, can it actually be fitted, or has anyone fitted a simple external fan - like a computer fan and does this work enough to compensate its losses?)

The temperature of the heatsink does run about 60 degrees C - this is the temperature displayed on the screen. Is this the temperature used to measure and therefore control the derating or is the derating temperature at the measured at the internals of the unit?. In my manual it says - page 83 - full power is guaranteed up to ambient temperature of 55 degrees C.

Also, another question for the gurus of the forum to get their teeth into. Maybe this is another thread, or there already is a thread on this - please redirect me if so.

Page 81 of my manual - which is PVI-3.0/3.6/4.2-OUTD-UK Rev 1.0 states that the maximum recommended output is 4150 W - the absolute maximum I have ever recorded is a consistent 3984 W - this must be a clipped output as in the winter I get this value every sunny cold day.

Questions:

1. Why can I not get 4150 W
2. Is the inverter clipped to this to meet the UK regs.
3. If so how can the clipping be removed.

Many thanks to all replies

rgf1

My 3.6kW Aurora indoor model is reporting internal temperature of 45'C with the air temperature around the inverter at 25'C and with 3kW of power going through it.
It is not de-rating at those temperatures and outputs - proven by the efficiency remaining in the 93-94% range just as it was a couple of months ago with the air around the inverter at about 15'C.

 

[moggy1968]

both the SB series and power one indoor inverter are less efficient than the TL, HF or outdoor versions.
They are older designs of inverter, some might say obsolete

 

[Gary K]

both the SB series and power one indoor inverter are less efficient than the TL, HF or outdoor versions.
They are older designs of inverter, some might say obsolete

I wish I had specced a 4000tl rather than the 3800 I have got, When I checked the info linked above ,I was surprised to see not only is it more efficient in general as to be expected but the 3800 drops off even more approaching max output and is most efficient at 30-50% of max knowing what I know now, and after checking the max outputs on PVoutput,I now believe the inverter could be equally if not more important than the panel choice