Energy Matters Forums

[Tracker]

Has anyone else questioned the actual power generated by their "System" ?

Have you looked at the output of that meter and wondered on what day of the year, it WILL deliver what you actually paid for? Even if for just 10 minutes !

I think that the INDUSTRY hides behind the smoke-and-mirrors of "Season-of-the year", "Dust on panels" , "Sun not bright enough", "resistive loss in cables" , ("Temperature De-Rating"), "Inverter Efficiency" etc. , "but HOW do you know the sun was bright enough?" etc. to justify why that 1Kw system only generated 800W , and the 2Kw system delivers 1.6Kw at midday..

Are you getting what you paid for, and if so, tell us what your system is.
Especially the Panel Manufacturer.
Do you think that you are actually getting what they paid for..
Is there any system delivering the specified output, even if only at Midday...

If not - Why not?
Would Fair-Trading accept that 1Ltr of petrol could be 800Ml except when it's -15DegC and it's less than 3 days old and at night and you live in Antarctica....

If the reality is, that the 1Kw figure is a theoretical figure that will never be achieved, then why are suppliers not legally required to supply a system that WILL generate the specified output IF it's installation is absolutely optimal, and normal losses taken into consideration..
Then - they could say - well it would cost you more to have adjustable panels, to optimise the output...and we can use thicker cables to reduce the loss... Do that and you WILL get the PEAK you paid for..
IF - an inverter is capable of delivering 1Kw OUTPUT, then why are there not sufficient PANELS supplied to achieve that output?

It's interesting that the Federal Govt. is cracking down on Insulation Installers who failed to deliver value for money. Should there be an inquest into "Value-for-money" in PV installations?

PS -- I have never heard a Seller/Installer declare "by the way - this 1Kw system you are installing , will only EVER give you a maximum of 800W"..... Has anyone?

[franks]

The Peak rating of a PV system is quoted are based on standard test (STC) contidions:
PV cell temputre 25`c
solar Irradiance 1000w/m*2
ASTM Standard Spectrum (artificial test lighting to simulate sunlight)

the test is done in a labtest setup

In the real world the solar radiation will heat up the PV panel beyond 25`c (typically up to 60`c on a very hot full sun day)
this will derate the output of a PV typical a derate of 0.3-0.5% of peak power per Dergee C above STC (can derate up to 10-12% of STC figures)

also allow the inverter will typical have total DC to AC conversion efficency of 90%

a overall 80% conversion efficency PV peak power to AC watts is at best in a real world situation

[Tracker]

a overall 80% conversion efficiency PV peak power to AC watts is at best in a real world situation

That is the whole point and is closely mimicked in the real world of PV installations..

So - how do System-installers get away with it..

Would anyone accept a car manufacturer saying you just bought a new car with a fuel economy of 100Km/Ltr, but you will only get 80 because it can't possibly give 100 -- Trust me - that's it

You cannot get an irradiance of 1000W/M^2 without HEAT, so why is the industry allowed to accept this de-rating? (Unless the PV panel is in a refrigerator with a bright light -- and that is not a real installation)

As I finished off previously "Cat amongst the pigeons ???"

[Lyngarin]

Sory Tracker, you used a bad example mentioning car manufacturer. A car has all the similar effects which affects its performance also. Like trye wear and pressures, day or night driving, speed and accelerator levels, wind velocity, carrying weights and the list goes on. Cheers gary.

[Tracker]

Sorry Tracker, you used a bad example mentioning car manufacturer.

Did I ? ..... Don't think so ! .... That car must be capable of doing the 100 on a test track, in the least.

A Solar PV system should be capable of delivering the rated power on the equivalent Solar-Test-Track !

Were I fully part of the Solar Industry, (and preferring to be honest with people,) I would have to offer a 1Kw system, that was theoretically capable of delivering 1Kw, under ideal conditions. IN THE LEAST !
If I did that, and my opposition does not, then how will my price compare? ( My sales skills would have to convince buyers of the benefit )

A 1Kw system MUST be capable of delivering 1Kw at 25cDegC, or it is either incorrectly designed or fraudulent ! ... Just take your pick !
( Whilst we have an Irradiance of more than 1000W/M2, and panels are perpendicular to the noon sun, and there is no dirt, etc. etc. )

Not that it matters much - The "Industry" is stuffed with a REC of $25.. None but the rich will be able to afford the luxury of PV, and most of them could not care, or rather would know any better !
At least, a gross FIT of 60c will make it possible to eventually recover costs.

We need the Gov't to pass the "Carbon-Tax" legislation, so that all of our living costs will increase, and our children will be burdened with pointless taxes and expense, for the rest of their lives, all so that the REC price will increase and we can recover Installation costs......

God, I feel so good about being GREEN ?????
.
EDIT -- Fact - In Sydney, the Solar Irradiance DOES reach 1000W/M2 in mid-winter.
In summer, the Irradiance will reach at least 1300 and will be above 1000 for perhaps 4 to 5 hours a day.
( Under optimum solar/weather conditions)
An honest system would thus produce Design Power (thermally adjusted) for that period of time.
.
http://forums.energymatters.com.au/solar-wind-gear/topic366.html

Reports from users in this thread above, clearly show that some owners regularly achieve Design Power.
They have purchased systems correctly designed , or they have been lucky in getting above-spec panels..
The only remaining question is 'at what expense' ?

http://forums.energymatters.com.au/solar-wind-gear/topic587.html

In this thread, we started to look at the real effects of Temperature, on the PV system output, and the reality of how much you pay for Better-Performance.

[SR76]

Fair point, sort of...

I agree with the idea of having a single standard to rate everything against but the standard for solar panels (25 degC) certainly doesn't resemble real field conditions. Not here, anyway. I bet in Germany the field conditions are generally closer to standard test conditions.

People have to beware of simplistic calculators that multiply peak sun hours * array nameplate rating and make no correction for system efficiency (usually 75-80%).

PVWATTS is a good online calculator that does take all of the possible efficiency factors into account and uses realistic, measured hourly data (picking "typical" months from many years of actual measurements) rather than monthly PSH averages.

http://www.nrel.gov/rredc/pvwatts/version1.html

Getting back to the point, though - you'd be setting a new benchmark in honesty to sell a 1000W system as "probably about 800W on a good day". Good luck with that.

(just for interest, I've seen my 1800W array max out my 1700W inverter for VERY brief periods when the weather is cool and the clouds are just right - but this probably totals 10 minutes a year...?)

[Tracker]

Getting back to the point, though - you'd be setting a new benchmark in honesty to sell a 1000W system as "probably about 800W on a good day". Good luck with that.

Is it not interesting , that in most industries, there is a code of practice that includes "Honest Reporting - Disclosure. etc." and yet here is an industry, largely sponsored by Govt. Rebates, that thrives on treating customers like mushrooms, and the biggest joke - it's approved of by the Govt. Here is an industry where when you get quotes, EVERY seller, lies to you because it's the industry practice. Why, this industry does not even have a PDS, ( Product Disclosure Statement ) to cover all contingencies.

Sure there are calculators that will give an estimated annual PV output, but I defy you all, to find a customer who does not equate a 1Kw PV system as generating the same power needed to heat a 1Kw radiator, and where the sun is bright for one hour, that they would not have generated 1KWh of power.

[sprout]

We have a 2kW Fronius inverter and only 6 x 170w panels, in theory max 1020w. On days with scattered cloud we have exceeded this in little energy "peaks" lasting a few seconds in the bright sun between clouds. Today we had a peak of 1098. A few days ago we had a peak of 1164w, however on a clear day we may only reach around 875w. For a 1 kW system I think that's pretty good. Our inverter record the day's peak. It is very interesting watching the w spike and decline as a cloud comes and goes.

[SR76]

OK, but is it truly a lie or less-than-total disclosure (and is there a difference?).

I don't think anyone is deliberately acting unscrupulously or believes that they are deliberately lying.

However it's often a case of "reading the fine print", and this is where the difference between salespeople might creep in. Some sellers make the fine print finer than others and some don't print the fine print at all. You could certainly argue that the seller SHOULD or MUST make the customer understand what they are buying (or what the difference between 1000W and 1000Wp means).

I think there should be a standard for disclosure just as there is a standard for measurement.

[Gordon-Loomberah]

(just for interest, I've seen my 1800W array max out my 1700W inverter for VERY brief periods when the weather is cool and the clouds are just right - but this probably totals 10 minutes a year...?)

My 1830W array, which contains a mix of brands, but all have a similar peak power voltage, puts out high power peaks more than the rated power fairly often. Best I have seen so far is 2130W, on a cool day with good bright cloud edge effect. However, typical output this time of year on a mild day with a bit of breeze is about 14-1500W. On cool days with a few clouds around I often see peaks over 1900W though. 1.99kW yesterday, 1.93kW the day before.

Gordon