[TRNSYS-users] type 94a question

[David Bradley]

Kostas,
   I can think of a few things that might account for the difference. First 
(and the simplest) is that Type94 does not account for any wiring losses 
between the PV modules or between the array and the inverters (where the 
actual power produced is usually measured). Those wiring losses can be 
significant, especially for high current (low voltage) applications 
(P=I^2*Rwire). Second, actual PV panels have a bit of variability in them. 
The specification sheet is usually an idealized average that was generated 
at a test facility. I have seen PV panels whose actual current-voltage 
characteristic was as much as 10% different from the spec sheet. When a 
number of PV panels are combined in series and in parallel to form an 
array, the weaker panels dictate the performance of array since the voltage 
drop over each parallel branch must be the same. Lastly, localized shading 
effects can have an important impact on array performance (again, not 
directly reflected in Type94). The problem is that the actual power output 
reduction of a shaded PV is not a linear function of the fraction of the PV 
that is shaded. I hope that helps to explain some of the potential 
differences between the simulated and expected results.
Kind regards
  David


At 09:14 3/29/2007, =?ISO-8859-7?B?yv7z9OHyIM/x5O/17PDv5tzt5/I=?= wrote:
>I noticed that the values of the output of the Type94a are much grater 
>than the real one. The efficiency coefficient of the current PV is 274 [W] 
>/(1000[W/m2]*2.24[m2])=0.122, while the Type94 gives 0.16 while the 
>radiation is near the reference conditions...
>
>The problem that I have noticed in practice is that I tried to simulate a 
>100 kW PV station. The price of the PV kW in Greece is 0.47 ¤/kW and the 
>mean gain (¤) of a 100 kW PV for a year is about 55.000 - 60.000 ¤. The 
>TRNSYS gives a value of 100.000¤ per year. So since the price is the same, 
>the problem is that it gives much more output (kW)
>
>Any Ideas ?
>
>
>Ordoumpozanis Kostas
>Kozani, 29/03/2007
>Greece
>Content-Type: application/zip; name="bathmos apodosis.zip"
>X-Attachment-Id: f_ezvae3hx
>Content-Disposition: attachment; filename="bathmos apodosis.zip"
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