Hi I've just spoken in considerable detail to a friend who works on a geophys boat in the oil survey industry.
It seems to me that the well-tested designs used in this industry are ideal for use in deploying/testing brightwater. Whilst Salter's ships are likely to be an appropriate low-carbon vessel for geoengineering use, the design of distribution technologies to be towed from these ships is likely to be best if based on existing technologies. Geophys offers one set of technology, and fishing offers another. The oil survey vessel on which my friend works tows a hydrophone array. The largest vessels can pull an array which is around 1km wide. The towing ship employs hydrodynamic surfaces called 'doors' on cables known as 'superwides' to stretch a cable over the 1km width. Rigid structures are not used. Attached to this 1km wide cable are the streamer cables, which are up to 8km long, and typically up to 20 in number. Along these streamer cables are the hydrophones, and also the 'birds', which are pods for depth control of the streamer cables. These birds use fins and a pressure sensor to set streamer cable depth. The designs in use for the birds can be towed down to 40m deep, which is almost at the bottom of the mixed layer. However, they are usually set to between 5-15m, which suggests a design for deeper use could easily be made if needed. Vessel speed is around 4 knots when in use, and 5.5 when towing the array but not taking measurements. Transit speed of the boat when not towing is 11knots. For geoengineering use, there would be no obvious benefit to using long streamer cables, unless bubble lifetimes were very short - which would render the technology impractical. My expectation is that pulling a mesh of bubblers through the mixed layer would be the best technique, leaving a deep layer of bright water which will not darken when mixed by winds and surface waves. Roughly 50m deep of water would need to be brightened to achieve this. Therefore a mesh 1km wide, 50m deep can be towed at a speed of at least 5.5 knots, and probably much higher. It's not difficult to take those basic numbers and calculate the number of vessels required to operate this technology globally, based on a range of different bubble lifetimes. I feel it's important not to reinvent the wheel. The existing technology just needs 'plugging in' to the bubble generators already available in order to do some credible tests on the technique. This isn't a cheap process, but nor is is especially expensive. After some initial trial in tanks and lab-scale field trials, we can quickly scale up to deployment-scale equipment without needing any special boats to run the trials. It may even be possible to arrange the BW trials alongside existing geophys - provided the bubblers don't interfere with the hydrophones. I'd welcome thoughts on this matter, particularly from Russell and Stephen. A -- 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.
