Talk:Wave power

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[edit] Talk Page Archive

Archive 1 has been created with a link at above right. It is an exact copy of the talk page as it was before this edit. Archive 2, when needed in the future, should be a new subpage (same as creating an article) titled "Talk:Wave power/Archive 2" and the link added to the template on this page's code. For further information on archiving see Wikipedia:How to archive a talk page. See also User:5Q5 for the used archiving procedure. Thank you. Crowsnest (talk) 12:58, 28 March 2008 (UTC)

[edit] This is starting to become a linkfarm

Unless anyone truly objects with a valid reason all those companies should be at the bottom of the page, I am going to do a bit of spring cleaning on this article. The external links are a mess in my opinion. spryde | talk 12:25, 19 December 2007 (UTC)

Strong Support - Looking at the scroll bar, the Article is 2/3rds links out. Let's start a new list of external links here, put in an excerpt for justification, and then transplant. As a newcomer, these are the sites I found useful, either through WP or googling:
  • Archimedes Wave Swing (AWS) http://www.awsocean.com/technology.html - Extracts energy from vertical motion from submerged gas-filled buoys. These buoys are actually pistons filled with gas that undergo a compression cycle based on the height of the water column that applies a downward force, F = mgh, where h and m, height and mass, respectively, fluctuate under gravitation (constant, g) as tides and waves pass over these fully submersed pistons.
  • Permanent Magnet Linear Generator Buoy - http://web.engr.oregonstate.edu/~prudell/index_files/WE_Brochure.pdf - Oregon State University has developed three direct-drive prototype buoys designed to be anchored 1-2 miles offshore, in typical water depths of greater than 100 feet, where the buoys will experience gradual, repetitive ocean swells. Wave motion causes electrical coils to move through a magnetic field, inducing voltages and generating electricity.
  • US Patent 6,194,815 - A piezoelectric generator comprises one or more inner hubs, an outer, stationary support, and a plurality of strap-like piezoelectric power generating elements mounted between the hubs and the outer support. The hubs are mounted for relative rotation on a first shaft mounted eccentrically on a second shaft having an axis of rotation coincident with central axis of the outer support. Rotation of the eccentric first shaft causes the hubs to follow a circular path around the outer support axis but without rotation of the hub around its own axis. The movements of the hubs cause alternate straining and destraining of the piezoelectric elements for generating electrical energy. For obtaining high energy conversion efficiency, the elements are arranged in groups of three or more substantially identical elements which are identically strained but symmetrically out-of-phase with one another.
  • US Patent Application 20040217597 - An elongated cylinder is fully submerged, in vertical orientation, just below the mean water level of, e.g., and ocean, and of a length, dependent upon surface waves of preselected wavelength, such that the top of the cylinder experiences relatively large pressure variations in response to over passing waves while the bottom of the cylinder experiences an almost steady pressure substantially independent of the over passing waves. The pressure differential over the length of the cylinder is used for causing relative movements between the cylinder and adjoining water, and such relative movements are used for driving a piston of an energy converter. The cylinder can be hollow and in fixed location for causing water movements through the cylinder, or the cylinder can move through the water relative to a fixed transducer. In one version of the movable cylinder, the transducer is fixedly mounted on a fixed in place float disposed within the movable cylinder. In a second version, the transducer is fixedly mounted beneath the movable cylinder on the ocean floor, and the cylinder is coupled to the transducer.

(We also need something easier to find than Tester et alia for Wave Power Equations, with a clear definition of whether KE, PE, both, experimental value, etc. is the criterion for what is being called energy.) —Preceding unsigned comment added by Nukeh (talk • contribs) 02:31, 25 March 2008 (UTC) 100TWdoug (talk) 02:34, 25 March 2008 (UTC) User:Crowsnest has fixed. 100TWdoug (talk) 15:41, 28 March 2008 (UTC)

Recent deletions in Company and institutional links (with technology descriptions): Deleted all 404's and advertisements. Please don't undo the 404's. If I hit something useful, please aim hyperlink at a page with more information on it, one by one. This should also serve to remove dead companies. 50MWdoug (talk) 00:02, 29 March 2008 (UTC)

Recent deletions in Sources and external articles:Deleted all 404's. Please don't undo the 404's. If I hit something useful, redo one-by-one, else the link farm will resprout.50MWdoug (talk) 01:38, 29 March 2008 (UTC)

[edit] the technology

The descriptions of the technology are deficient, IMO. A good description of a piece of technology ought to supply enough information to mentally picture the basic workings of the device. From the description of the buoy method, for example, I can envision three different ways the device could be generating power -- four, if I pair buoys. The information provided ought to discuss the options and make clear what is actually being done.Dismalscholar (talk) 03:26, 7 February 2008 (UTC)

[edit] Archiving?

If these discussions (above) are complete, we could archive them; does anyone know where things are up to? Moonraker12 (talk) 10:19, 28 March 2008 (UTC)

I think that everything can be archived. Relevant to leave here or copy back: #This is starting to become a linkfarm. Crowsnest (talk) 10:27, 28 March 2008 (UTC)
I archived to /Archive 1 on March 28, see top of this page. Crowsnest (talk) 00:52, 29 March 2008 (UTC)

[edit] Edit & Improve, Don't Remove Good Content

  • "Power (in kW/m) = k H² T ~ 0.5 H² T" is correct. See "Technology White Paper on Wave Energy Potential on the U.S. Outer Continental Shelf" & other government produced papers. To wit:

P=(1,025kg/m3)((9.8m/s2)^2)((32pi)^-1)TH2; where T is time in seconds, H is height in meters (this is height above sea level or amplitude) and P is watts per meter (of coastline). So, (1025*(9.8^2))/(32*pi)=979.210735, in watts, which is about 1 kilowattt. Therefore, use crest-to-crest wave height, which is easier for the average person the visualize (since it's the apparent height to a swimmer), and we get "Power (in kW/m) = k H² T ~ 0.5 H² T". It's fine to add more math, but don't take away the simple equation that most people could understand.

  • The "technology descriptions" subsection is a fun & informative part of Wikipedia that I put a lot of effort into. The subsection was ruthlessly pruned. It is more than a list and more than links: therefore it passes the test of such standards as are discussed in The Economist's recent article "The battle for Wikipedia's soul". In the battle between “inclusionists” and “deletionists”, deletionists must be held to a higher standard -- because their indulgences deprive the reader of knowledge; whereas a little extra (correct) information hurts nobody.Anthony717 (talk) 20:57, 8 April 2008 (UTC)
There are however, regarding the restored section on wave power, quite some comments regarding the "good content", which is why it was replaced and improved upon in the first place:
  1. The simple power equation as given, is original research, in contradiction with WP:NOR. None of the mentioned references, including the White Paper referenced above, gives this formula. It is also in error, since the constant computed by you is in error, see below. Neither are limitations of this formula stated, e.g. deep water waves.
  2. The first reference, http://www.engin.umich.edu/dept/name/research/projects/wave_device/wave_device.html, is erroneous in its interpretation and calculation of wave power, multiplying the wave energy with wavelength and dividing by wave period. This is effectively saying that wave power is energy density times phase velocity, instead of energy density times group velocity (which is known since the 19th century: e.g. Stokes, Rayleigh, etc.). This results in an overestimation of wave power by a factor of two. Then this reference goes on with calculating "power density" per unit horizontal area, suggesting a totally erroneous view of wave power, lacking the insight that wave power or wave energy flux is the horizontal transport rate of wave energy.
  3. The other reference, http://www.esru.strath.ac.uk/EandE/Web_sites/01-02/RE_info/wave%20power.htm, the above mentioned White Paper, and the text (including references therein) as it was before your edits of April 8, 2008, just contain effectively the same formula's for the deep-water case, not containing your misinterpretations and errors in calculating the wave power "constant".
  4. Using these formula's, you correctly calculate (apart from the units) above that the wave energy flux (wave power) for T=1 second and H=1 meter is about P≈1000 watt per meter width perpendicular to the wave direction. Then you assume the White Paper is talking not about wave height (while it clearly states is does), but wave amplitude. Thereafter you make another error, since the power is proportional to wave height squared, so if it would have been wave amplitude (but it is not) it should have been divided by 2 squared (equals 4), instead of by 2 as you did. This makes also the wave power estimate for the 15 second, 15 meter high wave erroneous in the text restored by you. You did not make the effort to look into the same section below the new formulas, where the same example is calculated giving a different answer.
  5. It says: "The potential energy of a set of waves is proportional to wave height squared times wave period", which is pure nonsense. Potential energy density, integrated over depth, is per unit horizontal area, and proportional to the wave height squared. And the potential energy of a certain area that has to be multiplied by that area. Something proportional to wave height squared times period has certainly nothing to do with potential energy.
  6. Also the sentence "wave energy is also present as pressure waves in deeper water" has been restored by you. In progressive waves, as commonly found at sea, the pressure fluctuations reduces exponentially with depth, in the same way as the velocities, see e.g. Phillips (1977), Goda (2000) or any other good book on water waves. Only in standing waves there are pressure oscillations not attenuating with depth, creating microseisms, but too small to be interesting from the point of view of wave energy devices.
I removed the offending part from the "Physical concepts" section, and added a simple formula for the wave power in the deep water case (which is not OR, since I just take the formula from the White Paper, and use standard gravity and mass density of sea water to compute it).
I did not look at the other sections where you restored "good content", and leave that to others. Crowsnest (talk) 00:48, 9 April 2008 (UTC)
  • I'm sorry that my formula was wrong. I could have sworn I got the k=0.5 from a good source in the past. Anthony717 (talk) 02:19, 9 April 2008 (UTC)

[edit] Factor two in wave energy and power

  • Hello I'm new to this wikipedia thing, but I did see an error in the maths/physics at this page. The total energy for a regular wave is indeed 1/8 \rho g H^2 (standard linear theory), but it changes for a real-life irregular wave field. If you fill in the definition of the statistical parameter H_{m0} = 4 sqrt{m_0}, where m_0 is the variance of the surface elevation, which is 1/2 a^2 = 1/8 H^2, for a regular (sine) wave (a is amplitude = H/2, but H - as normal in wave theory - is total wave height, crest to trough), the definition becomes E = 1/16 \rho g H_{m0}^2. This gives an estimate of 0.5 H_{m0}^2 T kW, and 64 in the denominator of the first equation, instead of 32. (Bas Hofland). —Preceding unsigned comment added by 145.9.225.170 (talk) 08:54, 10 June 2008 (UTC)
  • Thanks for pointing this out. This has been corrected. -- Crowsnest (talk) 12:06, 10 June 2008 (UTC)

[edit] New source article in The Economist

New article in The Economist, "The coming wave," in the 7 Jun 2008 edition (pp. 22 of Technology Quarterly in the US print edition). Would be useful to mine for additional info for the WP article. Online reference is [1]. N2e (talk) 21:24, 11 June 2008 (UTC)