UC and Uv values

[Abhijeet Pande]

When we input Uc as 25 and Uv as 1.2 in PVSYST software, does PVSYST takes a default wind velocity of 3.3m/s, please advise,

 

One of the customers is asking us to take Uc as 25 and Uv as 1.2 and wind velocity as 3.4m/s, but PVSYST takes only Uc & Uv values as inputs, please suggest how to input wind velocity as per site.

 

We think, if we input Uv as 1.2 X 3.4 = 4.08, and Uc as 25, PVSYST is double including default wind velocity 3.3m/s.

[Michele Oliosi]

The wind velocity should be defined in the MET file, and will usually change hour by hour.

If you want to input a single "default" wind velocity you can simply set Uv = 0 and Uc = 25 + 1.2*3.4. This will be completely equivalent as having Uc = 25 and Uv = 1.2 with constant wind velocity 3.4 m/s.

[Abhijeet Pande]

Thanks Michele for your valuable support,

 

Much appreciated as we were stuck in this matter.

 

One more thing, one of the clients is asking us to keep Uc as ≥ 32, and Uv as 0, do you think, we should accept this, as we are getting 0.5% gain in energy with Uc =32 vs Uc =29,

 

But I have never seen any recommendation from PVSYST to go beyond Uc=32.

 

Please advise, this is for ground mounted solar system only, module installed in tracker.

 

Regards,

Abhijeet

[Michele Oliosi]

Uc > 32 seems to be very optimistic, although I do not have a strong basis for this argument. Since Uv = 0, this value depends on the particulars of the site (average wind speed) and of course the structure so it is difficult to say for sure. We do not know of any studies that recommend this value, but we may not be up to date. I would encourage you to discuss with your client the fact that this is well above the usual PVsyst defaults.