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Cut-in wind speed VAWT
Dear all
I performed several turbine simulations for a helical Vertical Axis Wind Turbine (see Helix 120°.png). I based myself on the design of the Sea Twirl S2X turbine (but with helical blades) and therefore also used some specs (cut-out windspeed = 25 m/s, rated wind speed = 12.7 m/s). At this rated wind speed I performed some simulations for several Tip Speed Ratios with a relative difference of 0.5 and concluded that a TSR of 2.8 corresponds to the highest power coefficient (see Power coefficient vs TSR.png). So I used this optimal TSR and performed simulations at different wind speed (from 1 m/s to 24 m/s) for the helical VAWT (see Power output vs wind speed.png). The aerodynamical (available) power output is however not the output power that the VAWT generates. This is indeed the electrical power output. Until now I choose a cut-in wind speed of 5 m/s (corresponds to a power output of 70 kW) by reasoning that this amount of power should be sufficient to overcome the inertia of the gear box and generator. This choice is however not justified.
My question is therefore: How can I know the cut-in wind speed of this helical VAWT? Can I use information of other simulation results in the QBlade software? Or do I have to base myself on information from other research (if so, does someone know where I can find it)?
Thanks in advance!
Kind regards,
Brecht
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Hi Brecht,
I am assuming that the simulation that you have carried out so far have been aerodynamic only?
If you include a structural model you could include the generator inertia and model the startup process of the turbine explicitly.
Typically, the cut-in wind speed is chosen to be the windspeed at which the turbine already captures a meaningful amount of energy at the lowest rpm (defined by the generator and gearbox) at which it can be operated.
Best,
David
Dear Dr. David,
Thanks for the fast response! I already added a structural file, but I now realize I did not fill in these values in a correct/rationalised way (see Structural file.png) …
I am currently quite close to the deadline of my Master’s Thesis and am not very much able to overdo all these simulations again … Can you give me some advice in choosing a ‘correct’ cut-in wind speed for this VAWT? (as I want to compute the yearly power output of this VAWT at various locations around Europe (by their Weibull distribution) by the Swiss power calculator (https://wind-data.ch/tools/powercalc.php?lng=en))
Thanks!
Kind regards,
Brecht
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Dear Dr. David
Oke, thanks! I will do this. And where can I find information about the startup capabilities of the VAWT (i.e. which output graphs in QBlade)?
Kind regards,
Brecht
Oke, thanks!
Quote from Brecht T on 7. May 2023, 22:31Dear Dr. David,
Thanks for the fast response! I already added a structural file, but I now realize I did not fill in these values in a correct/rationalised way (see Structural file.png) …
I am currently quite close to the deadline of my Master’s Thesis and am not very much able to overdo all these simulations again … Can you give me some advice in choosing a ‘correct’ cut-in wind speed for this VAWT? (as I want to compute the yearly power output of this VAWT at various locations around Europe (by their Weibull distribution) by the Swiss power calculator (https://wind-data.ch/tools/powercalc.php?lng=en))
Thanks!
Kind regards,
Brecht
Hi Brecht,
the cut-in, as mentioned before depends on a few things such as generator/drivetrain desgn and also startup capabilities of the VAWT, so I cant give you any good advice not knowing all the details of your design. You could just choose a cut-in of 3m/s or 4m/s for the sake of AEP calculation and assume that your design can operate at low rpm’s and has good startup capabilities. Depending on the site this also wont affect the overall AEP too much since the power produced at the low windspeeds, maybe do some tests on a spreadsheet and check the sensitivity of AEP towards the cut in to get a feeling for this.
Best,
David
Quote from Brecht T on 8. May 2023, 14:30Dear Dr. David
Oke, thanks! I will do this. And where can I find information about the startup capabilities of the VAWT (i.e. which output graphs in QBlade)?
Kind regards,
Brecht
Hi Brecht,
you can get information about the change in rpm and power output over time in the normal aerodynamic and structural time-domain graphs.
Best regards,
David
