ITI 5MW Barge

Wind & Water Structural Analysis
1

If I were to change the payload of the ITI Barge, i.e. put photovoltaic panels instead of a wind turbine where can i refer to change the barge design dimensions and hence ultimate cost of the barge? My objective is to do an economic feasibility study between offshore wind turbines and photovoltaic panels … i.e. another valid question is can the 40 x 40 x 10 m barge size be optimized by changing the dimensions and will FAST indicate validity or otherwise?

2

Dear Peter,

Changing the ITI Energy barge design will require a redesign. The only reference where the design details of the ITI Energy barge are available is in the following document where the design originated:

Vijfhuizen, W. J. M. J, Design of a Wind and Wave Power Barge, M.S. Dissertation, Department of Naval Architecture and Mechanical Engineering, Universities of Glasgow and Strathclyde, Glasgow, Scotland, September 2006.
I do question why you want to use the ITI Energy barge as a starting point for your analysis. More likely than not, unless the barge is installed only at sheltered sites, modifi cations to the system design will be required to eliminate the vulnerability of the barge to extreme waves.

FAST is aero-hydro-servo-elastic simulation tool that models the coupled response of offshore wind turbines to wind and wave excitation. With proper application, you can determine the validity of a concept through the tool.

Best regards,

3

Dear Jason,

My objective is to first run a full simulation with the 5MW WT on the ITI Barge (as already done) so I can understand the full workings of FAST and then hope to modify some of the variables to simulate Mediterranean conditions for the same Barge-WT combination and also replace the WT load/s with loads coming from Photovoltaic arrays. Hence I should be in a position to come up with some financial calculations for an economic appraisal of both energy scenarios. Am I on the right track when using the Barge model in FAST for this purpose?

Thanks

4

Dear Peter,

Understanding the workings of FAST is certainly important for proper application of the tool, but I still question using the ITI Energy barge as a basis for design.

Best regards,

5

Dear Jason,

What would you suggest? I need a concept offshore platform on which I need to simulate a 5 MW HAWT and photovoltaic panels (& their respective wind loading) … so that I can then compare …

Thanks

6

Dear Peter,

We have public models of the ITI Energy barge, OC3-Hywind spar, and MIT/NREL TLP included with FAST v8 (we also have FAST v7 models of these available). Our next release of FAST v8 will also include a model of the OC4-DeepCwind semisubmersible. I guess it depends on what you want.

Best regards,

7

Hi Jason,

So really its the “semi-submersible” model which I would need. When will this model be launched for the public? Admittedly I am quite tight for time so in its stead is there a model which I could I use to simulate a the “floating WT platform” and respective “floating PV platform”?

Thanks,
Peter

8

Hi Jason,

Further to my previous posting earlier on I am having a look at the ver_8 file for the TLP platform. Can I modify the files to have “catenary mooring”? Is there a FAST_8 user guide so I can modify lines such as True CompMAP - Compute mooring line dynamics (flag)?

Thanks

9

Dear Peter,

The OC4-DeepCwind semi-submersible model will be included in our next release of FAST v8. We ran into a few snags that have prevented us from releasing this already, but the release is coming soon (no later than June 30).

A TLP is generally not stable if the tension legs are swapped with catenary lines (although the MIT/NREL TLP is stable in mild sea states without the tension legs). While I wouldn’t recommend changing the tension legs to catenary lines in the MIT/NREL TLP, the MAP User’s Guide explains how to use the software: wind.nrel.gov/designcodes/simula … 6a-mdm.pdf.

Best regards,

10

Hi Jason,

So for now I will use the Barge with a significant wave height of 2.5 m (Mediterranean conditions within 5 km of this Maltese shoreline) with an exceedance probability of 5 % (Malta Significant Wave Height Study: Malta Maritime Authority, December 2003) since I have a deadline for my draft of May.

Will see what the simulation comes up with.

Regards,
Peter

p.s.

How can I attach images in a reply?

11

Dear Peter,

You can upload an attachment or insert an image via url.

Best regards,

12

Dear Jason M. Jonkman,

Can you help me to find that Dissertation?
I am doing a Dissertation with a Barge of that type and i can’t find more informations for it to compare them properly.
Thank you for your time.

Best Regards,
Theodoros Christoforidis

13

Dear Theodoros,

I’ve send Vijfhuizen M.S. dissertation to you via e-mail (I’m not sure what the Unversity’s publishing policy, so, I didn’t post it here).

Best regards,

14

Dear Jason.

I am comparing hydrodynamic added mass and damping terms calculated with Nemoh to those provided for the ITI energy barge, which were calculated with WAMIT. I am wondering about the roll, pitch and yaw inertia about the centre of mass inertia about the CM, which in your report “Modal dynamics of large wind turbines with different support structures” are listed as 726,9e6 kg m^2 for pitch and roll and 1453,9e6 kg m^2 for yaw inertia. I get larger values with NEMOH (1130e6 kg m^2 for pitch and roll and 2246e6 kg m^2 for yaw). I am thinking that it must be due to the fact that NEMOH calculates the inertia terms based on the displaced volume (which I have entered as 40x40x4,0=6400 m^3), and some of the displacement is due to the vertical component of the mooring lines. It would be interesting to see the how these terms were calculated and would it therefore be possible for you to send the dissertation by Vijfhuizen about the barge?

15

Dear Jacob,

I don’t know a lot about NEMOH, but it is not possible to calculate the center of mass and inertias of a floating body based only on its external geometry (the mass of a floating body can be calculated based on the knowledge that it floats, but not the center of mass and inertias).

Send me an e-mail and I can reply with a copy of Vijfuizen’s MS thesis. However, as mentioned in Section 3.2 of my PhD thesis-turned NREL report: nrel.gov/docs/fy08osti/41958.pdf, the final ITI Energy barge design is a bit different than that developed by Vijfuizen, so, things like the center of mass and inertias will be a bit different.

Best regards,

16

Dear Dr. Jason Jonkman

I am trying to analyze the ITI 5MW Barge using FAST V8. I have few questions regarding the geometry of the platform and tower used. I would highyl appreciate your help.

  1. In some reports the dimensions of the Moon-Pool are given as 10 * 10 * 10 m while in one report given as 10103.99 m. I believe the later ones are correct dimensions?

  2. In Table 3-8 of your PhD dissertation the tower mass is given as 347,460 m, and tower height above ground is given as 87.60 m and its center of mass given as 38.234 m with respect to ground or MSL. In the ElastoDyn input file for ITI-Barge the distance from the MSL to the tower base is, TowerBsHt = 0. This made me confuse about the tower height and its center of mass. As the free-board of the platform is 6 m then the TowerBsHt from MSL should be 6 m. Thus the total height of the tower becomes 87.60 - 6 m. I would highly appreciate your help regarding the correct values of the tower height, tower base, and its center of mass from MSL.

Also i will be thankful if you can send me a copy of Vijfuizen’s MS thesis, i will email you.

Thank you

17

Dear Zahid,

Here are my answers to your questions regarding the ITI Energy barge:

  1. The actual dimensions of the moon pool are 10 x 10 x 10 m. The WAMIT model only needs to consider the wetted portion of the surface of the barge with moon pool in the undisplaced position i.e. the draft of 4 m. Because we did not attempt to model the energy extraction device in the moon pool, we simply covered the top of the moon pool in the WAMIT model with a flat plat located 0.01-m below the MSL, resulting in the WAMIT model having a moon pool of dimensions 10 x 10 x 3.99 m. See my PhD thesis-turned NREL report for more information: nrel.gov/docs/fy10osti/45891.pdf.

  2. The moon pool is located in the center of the barge and the details of how the tower–also located in the center of the barge–was connected to the barge were never flushed out in the design. So, we simply modeled the tower base at the MSL.

Best regards,

18

Dear Dr. Jason Jonkman

I am trying to analyze the ITI 5MW Barge by using openfast. I would like to know about the design condition of the platform.

I will be thankful if you can send me a copy of Vijfuizen’s MS thesis.

Thank you

19

Dear Matt,

I’ve sent Vijfuizen’s MS thesis to you via e-mail.

Best regards,

20

Dear Jason,

Could you please send the thesis of Mr. Vijfhuizen, ‘Design of a Wind and Wave Power Barge’ to me ? I hope it contains the hydrodynamic analysis details of the ITI Barge.

Regards,

Rahul.