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January 2014 Issue

Using Surfactants to Counteract Coastal Impact of Hurricanes
Dr. Robert O'Brien

Hurricanes in the Gulf of Mexico hit drilling rigs and receiving platforms first, but if they make landfall in large cities (e.g., Hurricane Sandy), the resulting disaster increases by at least an order of magnitude, so anything that would eliminate or mitigate the effects should be welcome. There has been research done on the mechanism and thermodynamics of hurricanes and their genesis sites, and some laboratory experiments have confirmed mathematical approaches. The next stage should experiment beyond the lab, using all presently available knowledge and possible remedies to counteract the coastal effects of hurricanes.

In this vein, I conducted a commercial experiment in June 2007 to see if swimming pools with wave-making machinery can save heat by spreading a monolayer, even though a monolayer seemed unlikely to survive a wave of the usual height of 30 to 40 centimeters in a pool. Flexible Solutions International (FSI), based in Victoria, Canada, and maker of the WaterSavr (WS), an evaporation prevention monolayer, loaned me three employees to test the idea in a 2,400-square-foot pool in Victoria. We focused on a section of interest about 20 feet across. The wave machine was operated on command in the evening for one hour. One FSI employee took still photos of the meter I held about 60 centimeters above the still water, which measured time, temperature (in ° C) and relative humidity (RH), another operated a video camera focused on the climb-out ladder across the pool and another spread the monolayer.

The single trial began with pictures taken before the wave machine was turned on. Meter readings were photographed before the wave machine began working, as the monolayer passed the marker point and spread to the whole pool, and after it broke up. Video recording was continuous at all of these junctures.

A limited amount, 8 ounces, of WS dissolved in isopropanol (FSI's Heatsavr) was applied to the pool water, and although it is basically a long-chain fatty alcohol that forms a solid monolayer when spread, on an essentially open-ended water surface when the amount of fatty alcohol applied is restricted, and with the agitation of 30-to-40-centimeter waves, at some point the monolayer disperses.

The diffuseness of the light reflected from the pool surface changed, becoming less diffuse then more diffuse again; a change captured in the video recording, with two frames used for Moir' interferometry to show wave height change.

The handheld meter measured time, temperature and RH taken initially in calm water. Calm water readings were 63 percent RH and 27.5° C. When waves were generated by machine, the RH rose to 71 percent and the temperature rose to 27.8° C. As the WS spread, the RH dropped to 58 percent and the temperature to 27.5° C. After the WS spread from the application point to the data point (pool ladder) and the monolayer broke up, the RH rose to 62 percent and the temperature to 27.8° C.

MIT Professor Kerry Emanuel's team, which focuses on tropical circulation and climate and has done some research with WS, has shown in the lab that as little as a decrease of 2.5° C in water temperature could destroy a hurricane. Crude calculations suggest that a compact monolayer, which actually raises the surface temperature while lowering the vapor pressure (the desired result), has the same effect as lowering the water temperature by 2° to 3° C. This means that the monolayer produces an effect in the right temperature range to potentially destroy a hurricane.

The experiment in the pool using WS can then be considered applicable to real-world hurricanes, although it is probably too optimistic to consider this type of treatment as likely to destroy a hurricane, but a reduction from 5 to 4 in magnitude or a change in hurricane direction seems likely using this method.

Hurricanes are regularly monitored by aircraft as they come down the Southeast Trade Wind path. The cost range of these surveillance flights are about the same as the potential cost of dropping surfactant onto the ocean's surface by aircraft during a hurricane in the range of 2 by 10 miles, under the eye wall and up wind. The estimated total is $100,000 to $300,000 every three days for about two weeks to put a WS monolayer down. The WS powder, which can be packed in 1-ton, water-soluble bags on pallets, is already commercially available and is converted to water and carbon dioxide in about three days by sunlight.

Frames from the video taken with the wave machine on before and after the WS spread were made into transparencies and put on a light box, and the top one was rotated slightly to form Moir' fringes. The distance between fringes was measured, and the reduction in average water height was calculated as 0.015 millimeters due to ripple smoothing and reduction of the evaporation area. It seems likely that a much more rapid and efficient electronic means of applying this technique could be used to assess the increase or decrease in ocean turbulence for storm monitoring.

This experiment is a strong indication that modern surfactants properly formulated can reduce the height of ripples'but not waves'and so reduce the evaporation area available to fuel a hurricane, while doing no harm to the ocean environment. The next step should be a rigorous test in a larger wave pool with variable, larger waves and variable winds. Winds cause 'rafting,' or the monolayer being blown downwind, which may be desirable for translating results into real-world circumstances. If that experiment is a success, then a test on a potential or actual hurricane and close evaluation of the results should be attempted.

Dr. Robert O'Brien was born in Nanaimo, Canada, in June 1921. He was a pilot in the Royal Canadian Air Force and conducted a tour of operations in Burma during World War II. He has a bachelor's degree in chemical engineering, a master's degree in metallurgy and a Ph.D. He is a professor emeritus at the University of Victoria in Canada, serves as a consultant and has authored more than 150 papers.


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