Hi Stephen I think your concerns about pumping energies are misplaced. The mass of air pumped would be pretty low as the bubbles are so small, so there won't be big displacements, frictional losses, etc. My guess is that the energy to overcome ship drag and the energy to form the bubbles will be much lower than the pumping energies. Perhaps you can run some calculations on this.
An alternative mixing strategy would be to create the bubbles on the surface, and then pump the water down (or guide it downwards with blades or pipes). The density differences will likely not impede this. One effect that is potentially overlooked in discussions to date is the tendency of the whitened water to sink by mass movement convection currents. This may reduce the efficacy of the bubbles, as they are dragged down in cold downwelling water to beneath the photic zone. It may be that bubble lifetimes change significantly with depth, as deeper waters have different properties as a result of vertical motion of plankton. My thinking is that, in general, dedicated ships will only be useful for testing. The idea of tethered bubblers with solar panels seems more realistic - relying on tides and currents to move the water, rather than relying on movement of the bubbler through the water, which is both logistically troublesome and energetically expensive. A variety of energy sources are available or tethered bubble generation, as you will know from you excellent and sadly largely overlooked work in the 70s on wave energy. Ship tracks may be part of the solution, but as with CCN, my suspicion is that the ship tracks will be too concentrated geographically, and generally in the wrong places. No matter how white the English Channel and Suez Canal, it wouldn't make much difference to global warming. Thanks A On 27 April 2011 18:21, Stephen Salter <[email protected]> wrote: > Andrew > > I did think about paravanes on a single ship as you suggest but thought > that we could avoid the drag of the paravane by making two systems as long > as the paravane that you would have chosen, joining them together and > throwing away the two paravanes. Two boats is OK if the wake is twice as > wide but I want bubbles coming from the full length. > > I think that the limitation on vessel separation might the the pumping > power so I was keen to pump for both ends. > > I would not like to have to pump down to 10 metres because of the extra > pumping energy. > > Michael Hayes > > The boats will sail best on a beam sea slightly on the quarter but may > sometimes need to get to windward. Flettner rotors can go directly into > reverse just by changing the direction of spin. Wing sails can go directly > into reverse by a pitch change. Thanks for the numbers on bubble size. > > Mike MacCracken > > I would prefer to start cloud modification field trials on soggy islands > like the Faeroes but would be happy to do experiments on conventional ships > provided that we can go to different sorts of places and do not mess up the > air with our exhaust. I understand that some research vessels have > specially clean fuel. > > I an not so happy about conventional ships for bubble release because the > wake will be rather narrow. However if the bubbles gave a drag reduction > everything would change. They would all want to use it. We would have to > develop short lived bubbles of face excessive cooling. Would this need a > higher coal use? > > Stephen > > > Emeritus Professor of Engineering Design > Institute for Energy Systems > School of Engineering > Mayfield Road > University of Edinburgh EH9 3JL > Scotland > Tel +44 131 650 5704 > Mobile 07795 203 195 > www.see.ed.ac.uk/~shs > > > On 27/04/2011 15:50, Mike MacCracken wrote: > > Another approach to the bubble generation effort, and one Russell has > suggested, is to take advantage of existing ships (of order 1000 to 10,000 > commercial ships at sea on a given day) and to put bubble generators on > them—perhaps doing so in a way that reduces their hull friction to make up > for power of bubble generation. Indeed, lifetime matters, but that depends a > good bit on bubble size, and extrapolating from big bubbles in a present > ship’s wake must be done cautiously. > > Using commercial ships is also an approach that could be used for CCN > generation as well, again depending on lifetime, etc. Indeed, there are > areas where no ships go very often, but commercial ships would seem a fine > starting approach. > > Mike > > > On 4/27/11 10:14 AM, "Michael Hayes" <[email protected]> wrote: > > Thank you both for the insight. > > Yes, I do now recall the dual boat tether concept and I have some working > back ground in towing a long array of gear. From a pilot's point of view, I > can see an advantage of the dual boat/tether over the towed array. In that, > turning would be easier as well as being able to "lay out" a broader path > than a towed array. > > The need for a sail boat to tack back and forth into the wind does > seem challenging with a tether between the 2 boats. But, I can see how a > spring line rigging could adjust for any lag between boats in that type > of maneuver. The symmetrical hull concept is interesting in that I have > never considered a sail boat being able to "immediately" reverse direction. > > I personally would like to play with the idea of modifying the bright water > injectors along the tether to act as a "bow truster" type of directional > control for the tether. That may help in overall control of the > configuration. > > The recommended bubble diameter is .002mm. I can only see ultrasound > providing that type size for a high throughput operation. I believe a table > top experiment can possibly be done using the parts from an off the self > ultrasonic humidifier and deep well pump. Measuring such small bubbles is > something I have not studied yet. > > I did read in the paper Dr. Caldeira offered of observations of long lived > bubbles through possible contamination of a natural surfactant film. Yet, I > don't think the nature of the surfactant was mentioned. I refer to the first > page 2nd section > https://docs.google.com/viewer?a=v&pid=forums&srcid=MDE0NTY3NTk0NzY2MTMxMzQ4MjEBMDA1OTY0NDQ3MDgzNzU0NTIwODkBQkFOTGtUaWtZQ0pLSmJ2UzFRdFAzbmFrTHZkUTl3ay1kd0FAbWFpbC5nbWFpbC5jb20BNAE&pli=1 > > > Well, again, thank you both for the feed back. I will spend more time > thinking about this. > > > On Wed, Apr 27, 2011 at 5:29 AM, Andrew Lockley <[email protected]> > wrote: > > Stephen, > > This technology is already used for towing hydrophone streamers in geophys, > but it doesn't work quite like you suggest. There's no need for two boats, > and instead there's a paid of towed hydrofoils behind one boat, with the > support line tensioned between them. The low mass of the hydrofoils means > that there's no real shock on the cable in rough seas. The bubble > generators would be strung out on streamers behind this towed line. > > The bubbles would be distributed by a number of 'birds' which are depth-set > from the control room - just like the hydrophones are currently. > > To get good saturation with bubbles, I suggest that they'd need to be > delivered at a variety of depths - but whether that's worth doing depends of > course on the lifetime. No use dropping them ten metres down if they don't > last long enough to mix or rise. > > A > > > On 27 April 2011 13:05, Stephen Salter <[email protected]> wrote: > > Hi All > > Michael Hayes asks about how bubbles could be deployed. > > One possibility would be for a pair of wind-driven vessels to sail side by > side at, say, a kilometre separation, attached to each other by a buoyant, > streamlined tether. > > The chord of the tether would be about 100 mm. In plan it would form a > catenary with a generous bulge to reduce the tensile load. The nose of > tether would contain a strong Kevlar or carbon tension member. Behind this > would be a number of high-pressure air-lines taking very well filtered air > from each vessel to a porous strip near the nose of the foil section and > running the full length. The drag of the tether would be reduced by the > bubble layer on the underside. > > The tether would have to be elastic enough to follow the curvature of the > wave slope. In most sea states this is surprisingly low but elasticity can > be increased by running the tensile member in a series of S shapes. > > The vessels need power but could generate this in the same way as suggested > for the cloud albedo project. Indeed it would not be difficult to design a > dual purpose vessel which would change mode according to cloud conditions. > It would be convenient if the vessels were symmetrical fore and aft so that > they could tack by going into reverse. > > The design does need information on bubble life and the best bubble > diameter and I would be most grateful for any advice on this matter. > > Michael mentions the Dracone project. I worked on this in a very junior > capacity in 1960 but a kilometre wide bubble wake would be cheaper if the > bubbles can last long enough and less of a risk than a Dracone that got > loose. > > Stephen > > Emeritus Professor of Engineering Design > Institute for Energy Systems > School of Engineering > Mayfield Road > University of Edinburgh EH9 3JL > Scotland > Tel +44 131 650 5704 <tel:%2B44%20131%20650%205704> > Mobile 07795 203 195 <tel:07795%20203%20195> > www.see.ed.ac.uk/~shs <http://www.see.ed.ac.uk/~shs> > > > > On 26/04/2011 23 <tel:26%2F04%2F2011%2023> :21, Michael Hayes wrote: > > Please help me understand the mechanics of Bright Water deployment. I have > spent many months living on the Bering Sea (in winter) and have piloted > 150ft fishing vessels in that area for countless hours. I have watched the > sea continually produce white caps for as far as I could see for days and > weeks at a time. How can a practical, cost effective and meaningful use of > bright water be deployed which comes even close to .0001 percent of the > natural production of white caps? The energy and equipment needed to cover > any meaningful amount of the sea is difficult for me to comprehend. > Outfitting fishing fleets with the needed equipment and paying the boat > owners to run the gear is possible. But, we are only talking about a bright > water wake which lasts for only a short distance...at best. > > Designing autonomous platforms specifically for the mission may be > possible, but, one storm could beach every single platform within a few > hours. Who and how will they be collected and sent back out? This, from a > seaman's point of view, is difficult to see as being practical. I have > studied the concept though what has been offered here and through other > links. The mechanical challenge of producing such small bubbles is > interesting and I have even spent time thinking through the possible use > high throughput ultrasonic injectors. But, I still come back to the > questions of; 1) how can bright water be practically deployed? 2) How can > the investment be justified when the wide area effect is so tenuous? 3) > Would not reflective large surface rafts provide a more cost effective long > term overall result? > > There is the option of a reflective form of the Dracone Barge as a useful > way to deploy large area ocean surface SRM. " > http://en.wikipedia.org/wiki/Dracone_barge. > > If such barges were deployed in large numbers a large area rafting system > could be secured in needed areas and moved as the season changes. With small > desalinization pods attached, we could have not just have low cost/long > term/flexible ocean surface SRM but a nice supply of needed fresh water. > Sell the fresh water and buy more bags!!!! > > I ask your help in understanding how bright water can be a competitive form > of SRM. > > > The University of Edinburgh is a charitable body, registered in > Scotland, with registration number SC005336. > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
