Hurricane Moderation By Stephen Salter The formation of a hurricane depends on many factors, including atmospheric water vapour, distance from the equator and the recent history of wind patterns. But an essential requirement is a high sea surface temperature. To get from a tropical storm to the lowest category of hurricane requires a temperature of 26.5°C. We can moderate hurricanes, or even prevent them, by reducing water temperature. A useful start to any engineering project is the estimation of all the energy flows. One cubic metre of air at a temperature of 30°C can hold about 30 grams of water vapour. The energy to evaporate this is about the same as in 13 grams of TNT, enough for a nasty anti-personnel mine. A cubic kilometre of such air contains the same energy as the Hiroshima bomb. Hurricanes can be hundreds of kilometres in diameter and so contain tens of thousands of Hiroshimas. If you have read this far you will know about the billions of lost dollars and thousands of deaths from this amount of energy. Most of the hurricanes that reach America (with the exception of Harvey), start on the African side of the Atlantic near Cape Verde and grow as they move west. We can use Google Earth to measure the hurricane breeding area. The US National Weather Service gives a warm water depth of 45 metres. To cool this volume by 2°C in 200 days needs more than 600 times the mean US electricity power generation. If you want to moderate a hurricane tomorrow, today is much too late. You should have started last November. All this heat has come from the sun. Some could be reflected back out to space by clouds. The reflectivity of clouds was studied by Sean Twomey. He flew over many clouds, scooped samples and measured the solar energy reflected from their tops. He showed that reflectivity depends on the size distribution of drops. Lots of small drops reflect more than the same amount of liquid water in fewer, larger ones. In typical conditions, doubling the cloud drop number increases reflectivity by a bit over 0.05. Making cloud drops needs a high humidity but also some kind of ‘seed’ called a condensation nucleus on which to start growth. There are thousands of condensation nuclei per cubic centimetre of air over land but fewer in air over mid ocean, often less than 50. John Latham suggested that the salt residues left from the evaporation of a spray of sub-micron drops of sea water would be excellent condensation nuclei. They would be moved from the sea surface by turbulence to produce a fairly even distribution upwards through the marine boundary layer to where clouds form. The condensation nuclei could be produced by wind-driven sailing vessels cruising along the hurricane breeding areas getting energy from their motion through the water. We can make spray by pumping water through very small nozzles etched in the silicon wafers used for making microchips. The main technical problem is that sea water is full of plankton much larger than nozzles. This can be filtered using ultra-filtration technology with back-flushing, originally developed for removing polio viruses from drinking water. Each vessel would produce 0.8 micron diameter drops at 1017 a second. [ part-image from larger Wikipedia map ] Spray operations would depend on the pattern of sea surface temperatures as measured by satellites. We want the trajectory of temperature rises through the year from November to the following July to be those that an international panel of meteorologists think will give a desirable rainfall pattern from ‘gentle’ tropical storms. Most ships are made in quite small numbers. An exception was the Flower class corvettes built for the Royal Navy during World War II. If we index-link the 1940 cost to today we can predict that in mass production each spray vessel would cost $4 million. With assumptions which have not yet been rejected by hurricane experts, we think that controlling the Atlantic hurricane breeding paths would need about 100 vessels. With typical ship lifetime the annual ownership and maintenance cost would be about $40 million. If these figures and recent estimates of the cost of hurricane damage are correct the benefit-to-cost ratio is quite attractive. Because of official UK Government policy updated in May 2018 the project is privately funded.

Rising temperatures are increasing the amount of water vapor in the atmosphere at a rate of 7% more water vapor for every 1°C warming. This is further speeding up warming, since water vapor is a potent greenhouse gas. Over the coming years, a huge amount of additional water vapor threatens to enter the atmosphere, due to the warming caused by albedo changes in the Arctic, methane releases from the seafloor, etc., as described at this page.

The situation is dire and calls for comprehensive and effective action, as described at the Climate Plan.

Added below is a box from an earlier post with hurricane damage mitigation proposals.

Hurricane Damage Mitigation A 2014 study by scientists led by Mark Jacobson calculates that large turbine arrays (300+ GW installed capacity) could diminish peak near-surface hurricane wind speeds by 25–41 m/s−1 (56–92 mph) and storm surge by 6–79% AND provide year-round clean and renewable electricity. How many electric cars will be ready to move into Miami to provide emergency support in the wake of Hurricane Irma? Storms can cause power outages, electricity poles can get damaged. Electricity poles can also be a traffic hazard (i.e. collisions can occur even if the pole hasn't fallen down, especially when streetlights fail). When damaged, power lines hanging off poles constitute electrical shock hazards and they can cause fires to ignite and wildfires to start. Storms can also cause damage to backup generators and to fuel storage tanks, making it hard for emergency services to give the necessary support. Electric cars can supply electricity where needed, e.g. to power necessary air conditioning, autoclave and emergency equipment, such as in hospitals. After a tsunami hit Japan in 2011, electric cars moved in to provide electricity from their batteries, as described in many articles such as this one. Wind turbines and solar panels are pretty robust. Hurricane Harvey hit the Papalote Creek Wind Farm near Corpus Christi, Texas. The wind farm had little or no damage, there was just a short delay in restarting, mostly due to damage to power lines. The Tesla roof that doubles as solar panels is much stronger than standard roofs. Have a look at this video. Join the Renewables group at facebook! Clean and renewable energy can provide more stable, robust and safe electricity in many ways. Centralized power plants are vulnerable, in that all eggs are in one basket, while there can be long supply and delivery lines. Many of the benefits of clean and renewable energy are mentioned on above image. Furthermore, there are ways to lower sea surface temperatures. The image on the right shows the very high sea surface temperature anomalies on August 28, 2017. Note the colder area (blue) in the Gulf of Mexico. Hurricane Harvey cooled the sea surface as water evaporated and warm moisture was added to the atmosphere. The cyclonic force also mixed colder water below the surface with warmer water at the surface, resulting in colder water at the surface. The combination image below shows the difference between August 20, 2017, and August 30, 2017. [ click on images to enlarge ] A number of geoengineering methods can be used to reduce sea surface temperatures and thus reduce the intensity of hurricanes. Methods include upwelling associated with ocean fertilization and with ocean tunnels, marine cloud brightening and increasing and brightening bubbles in the wake of vessels, as discussed at the geoengineering group at facebook. Besides cooling the sea surface, there's also the upwelling of nutrients that can help combat ocean stratification. Warm water holds less oxygen than cold water. As the water warms, it also tends to form a layer at the surface that does not mix well with cooler, nutrient-rich water below, depriving phytoplankton of some of the nutrients needed in order for phytoplankton to grow (and take up carbon). Some of these methods are also discussed at this 2011 page, which also mentions that more research is needed into the impact of such methods. Of course, possible application should go hand in hand with dramatic reductions in emissions including a rapid shift to 100% clean and renewable energy. thesolutionsproject.org Similarly, the necessary shift to clean and renewable energy in itself will not be enough to avoid catastrophic warming, and it should go hand in hand with further lines of action to remove pollution and to cool the Arctic Ocean, as described at the Climate Plan.

Links

• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html

• How much warming did and could people cause?
https://arctic-news.blogspot.com/p/how-much-warming-did.html

• AccuWeather predicts economic cost of Harvey, Irma to be $290 billion
https://www.accuweather.com/en/weather-news/accuweather-predicts-economic-cost-of-harvey-irma-to-be-290-billion/70002686

• After Disaster Hit Japan, Electric Cars Stepped Up
http://www.nytimes.com/2011/05/08/automobiles/08JAPAN.html

• In Big Test of Wind Farm Durability, Texas Facility Quickly Restarts After Harvey
https://www.wsj.com/articles/texas-wind-farm-back-online-1504294083

• Tesla Unveils Powerwall 2 & Solar Roof
https://www.youtube.com/watch?time_continue=802&v=4sfwDyiPTdU&fref=gc&dti=2372679678

• Taming hurricanes with arrays of offshore wind turbines, by Mark Z. Jacobson et al. (2014)
https://www.nature.com/nclimate/journal/v4/n3/full/nclimate2120.html

• The Solutions Project
http://thesolutionsproject.org

• Weakening of hurricanes via marine cloud brightening (MCB), by John Latham, Ben Parkes, Alan Gadian, Stephen Salter (2012)
https://onlinelibrary.wiley.com/doi/10.1002/asl.402/abstract

• Engineering Ideas for Brighter Clouds, by Stephen H. Salter, Thomas Stevenson and Andreas Tsiamis  (2014)
https://pubs.rsc.org/en/Content/Chapter/9781782621225-00131/978-1-78262-122-5

• Multiple Benefits Of Ocean Tunnels
https://arctic-news.blogspot.com/2015/02/multiple-benefits-of-ocean-tunnels.html

• Oxygenating the Arctic
https://arctic-news.blogspot.com/p/oxygenating-arctic.html

• Reducing hurricane intensity using arrays of Atmocean Inc.'s wave-driven upwelling pumps
https://www.youtube.com/watch?v=xlnR_GMNIGA

• Could bright, foamy wakes from ocean ships combat global warming?
https://www.sciencemag.org/news/2016/01/could-bright-foamy-wakes-ocean-ships-combat-global-warming

Some of the world's most preeminent climate scientists, all experts with many decades of experience in their respective field, are warning that effective action must be taken now to avoid catastrophe.

These scientists, and many others, have made valuable and much-appreciated contributions to the Arctic-news blog over the years [note: contributors each express their own views in posts and may or may not endorse other content of this blog].

Sam Carana, editor of this blog, has for years supported the calls of these scientists, also discussing and sharing their calls at facebook groups such as Arctic-News, Electric Transport, Renewables and Climate Alert.

Furthermore, Sam Carana has called for specific action for years, including support for biochar, preferably through feebates. More specifically, Sam Carana recommends that revenues raised from fees imposed on sales of livestock products, nitrogen fertilizers and Portland cement are used to fund support for soil supplements, as illustrated by above image. For more on biochar, see this blog and this facebook group.

For years, Sam Carana has also called for more R&D in specific areas of geo-engineering. For more on this, see this blog and this facebook group.

More generally, Sam Carana advocates the Climate Plan, which calls for a global commitment to parallel lines of action while seeking to delegate implementation to local communities, preferably through effective policies such as local feebates.

This blog has had some success in spreading this message. To date, Sam Carana has received 82,327,368 views at Google plus (see screenshot on the right), while this blog has received 3,255,445 views (see update of views in the panel further on the right).

Your continued support is needed to share this message, so please join one or more of the above-mentioned groups, and share and like the images of this post in emails, on facebook and other social media.

Regarding the urgency to act, the images below give an update on the terrifying situation in the Arctic, where the sea ice is disappearing fast.

The decline of the snow and ice cover in the Arctic goes hand in hand with rising sea surface temperatures that contribute to sea ice getting ever thinner.

The image on the right show Arctic sea ice on September 1, 2016, with thickness in meters.

The warming of the oceans is illustrated by the images below.

The image directly below shows sea surface temperature (left) and anomalies compared to 1981-2011 (right).

The image below also shows sea surface temperature anomalies, this time compared to 1971-2000.

Global warming has hit the Arctic particularly hard over the past 365 days, with anomalies exceeding the top end of the scale over most of the Arctic Ocean, as illustrated by the image below.

The situation is dire and calls for comprehensive and effective action as described at the Climate Plan.

Can we Design Hydrogen-Fuelled Aircraft?

S H Salter, Engineering and Electronics, University of Edinburgh.EH9 3JL.

The collection of temperature measurements by David Travis following the 3-day grounding of all US civilian flights after 9/11 showed the astonishing effect of jet exhaust on the environment. If burning hydrocarbon fuel in the stratosphere ever becomes a criminal offence, the aviation industry will have an interesting problem. A possible solution is the use of hydrogen as a fuel. Is this technically possible?

The Airbus 380 carries 250 tonnes of fuel with a total calorific value of about 1013 joules. Fuel is stowed in wing tanks but this would be a volume of about one eighth of the fuselage. The calorific value per unit mass of hydrogen is about 3.5 times that of jet fuel and so the weight of hydrogen for the same range would be only about 70 tonnes. Unfortunately the ratio of density of jet fuel to un-pressurized hydrogen is about 9000, so the design problem is how to reduce the volume ratio by about 2500. If we compress hydrogen to reduce its volume by a factor of, say, 100 we still have a fuel volume of 25 times the liquid fuel one or 3.2 times the fuselage volume. The cube root of 3.2 is 1.47 so by increasing all three fuselage dimensions by this factor we could have an aircraft with enough volume for all fuel in the fuselage but no passenger space. An increase by a factor of about 1.6 in both diameter and fuselage length would give enough volume for passengers provided they did not feel unhappy about being close to so much hydrogen.

The immediate reaction against the proposal will be triggered by embedded folk memories of the Hindenburg. Any use of hydrogen will need careful public relations. The Hindenburg survival rate was 64%, much better than crashes of modern conventional aircraft. Deaths were caused by jumping not burning. People who stayed aboard until the wreck reached the ground were unharmed. It is likely that the fire started in the fabric dope rather than the hydrogen. Because spilt hydrogen moves rapidly upwards there is much less risk than from a liquid fuel or heavier-than-air gases like butane or propane which regularly cause devastating explosions in boats and buildings. Furthermore the heat radiated by the invisible hydrogen flame is much lower than that from carbon particles in hydrocarbon flames. We can argue that hydrogen is actually safer than jet fuel, petrol and hydrocarbon gases.

We can spend the 180 tonne fuel weight-saving on gas storage bottles in the form of a low-permeability skin surrounded by wound carbon fibres. A helical winding of aluminium sheet with a low diffusion coefficient for hydrogen looks good. It can be made with the linear equivalent of spot welding. The axial stress in a thin-wall tube under pressure is only half the hoop stress, so we can use the gas tubes as fuselage strength-members. Once the fuselage bending moments are known, we can choose the wrap angle of the windings to give the right balance of directional strength. One structure might be a bundle of nine tubes in a hexagonal array with six full of hydrogen and three containing passengers. A cross section is sketched in the figure. Other configurations are being studied.

The smooth stress paths of the gas bottles would be badly disrupted by the conventional design of landing gear. Can we get rid of it? The requirements for processing the variable energy flows from renewable-energy sources have led to the development of new high-pressure oil machines using digital rather than analogue control of machine displacement. These machines have very high conversion efficiencies and very easy interfaces to computers (see http://www.artemisip.com/ ) . The extremely accurate control of very large energy flows allows many new applications. One of these involves replacing the landing gear of large passenger aircraft with a ground vehicle. Please suspend disbelief until you have considered the following facts:

1. The landing gear of the A380 weighs 20 tonnes, say, 200 passengers. This weight is carried round the world for many hours and then used for only a few minutes on each flight.
2. The landing gear occupies a substantial volume of the internal space. The volume restriction limits the travel of the landing gear and so increases acceleration forces.
3. The requirement for openings compromises the structural integrity of the fuselage and adds weight, even more passengers.
4. Landing gear must perform with very high reliability despite the weight penalty and extreme temperature cycling.
5. The full weight of the aircraft must be passed to the ground through highly stressed points.
6. Gas turbines are very inefficient for moving aircraft on the ground at slow speeds.
7. On the A380 the shape of the landing gear doors and opening spoils the aerodynamic fairness. 
8. There is a severe design conflict between tyre weight, tyre life and braking performance.

An alternative might be to provide the function of the landing gear by a special-purpose ground vehicle. It would of course have to have VERY reliable links to the aircraft ground approach electronics so as to be in exactly the right place and moving with the right velocity underneath an aircraft on final approach. However there would be no weight, volume or temperature compromises.

The contact between the landing vehicle and the aircraft would be provided by a nest of large air-filled tubes like very large, very soft V-block, running the full length of the fuselage. This would spread the weight evenly into the aircraft skin. The tube surfaces could have vacuum suckers, like an octopus, which could apply shear forces evenly to the aircraft skin. The bags could be on a frame which could have hydraulic actuators to give a much longer travel than the legs of the landing gear. Tilting this frame would remove the need for the angling of the rear underside of the fuselage required to prevent ground contact at V-Rotate. This would further reduce drag during flight. The absence of fuselage penetrations could allow safe water landings for emergency. Runways can have parallel lakes presenting a much lower fire hazard if fuel is spilt. The impact loading on the runway would be much reduced and it might even be possible to revert to grass runways with several parallel operations from any wind direction.

The ground vehicles could use Diesel engines with much higher efficiency at taxi speed than gas turbines. They could have higher acceleration during take off and higher deceleration during landing. The hydraulic transmission would also allow regenerative braking, so the kinetic energy from one landing could be used for the next take-off. All-wheel steering and the option of direct side movement would allow much better use of ground space. The ground vehicle could have many more tyres, which need have no weight or volume compromise to achieve high braking. It could have an air-knife to dry runway surfaces and remove snow. There would be plenty of time to inspect and exchange landing vehicles and they would be in use for a much higher fraction of the time. The landing vehicles could gently lower aircraft on to passive supports at each loading pier and be used for other movements while aircraft were being boarded or serviced.

Images by S H Salter, University of Edinburgh.

The volume of most aircraft wings is much below that of the fuselage and so there is not a strong reason to use gas tubes as structural wing members. However they would offer a way to offset the extra drag of the larger frontal cross-section. From the original work by Prandtl, it has long been known that sucking air from the upper surface of an aerofoil section will reduce the drag by an amount which far offsets the power needed for a suction pump. Schlichting in figure 14.9 of Boundary Layer Theory gives a graph showing a factor of more than two. An objection to suction on wings, where the outer skin is a structural member, is that perforations and slits cause stress concentrations. This should not apply to wing spars made as gas tubes supporting an unstressed skin.

It is important that using fuel does not move the centre of gravity of the aircraft. This happens automatically with fuel stowed in wing tanks. If large quantities of fuel are to be stored in the fuselage it will be necessary to have the centre of pressure of the wings close to the centre of gravity of the fuselage-engine combination. The choice of a ground-based landing vehicle suggests high wings and engine placement above the wing. In theory at least, this will give some advantage from higher air-velocity over the upper wing surface and lower noise transmission to ground level. It is much easier to service and inspect equipment if you do not have to reach above your head. Cranes lifting an engine upwards are much more convenient than forklift trucks working from below. While some change in the architecture of maintenance hangers would be required, high engines accessed from above would by no means be unwelcome to ground crew.

Gas tubes may not be ideal for connections to a low-chord wing and so the longer attachment line of a delta wing, such as used in the Vulcan and Concord and many fighter designs, should be investigated. A flat underside will relax the requirement for precision in yaw during landing. Suction may be able to offset some of the disadvantages of the delta wing as applied to civilian aircraft provided always that they can land safely after a failure of the suction system. A delta wing with a deep thickness and a leading edge made from very strong but transparent material, perhaps poly carbonate, might even allow passengers to sit in the wing enjoying a splendid view if their vertigo allows.

The range of the A 380 is 15,000 kilometres. While this may have been chosen for passenger convenience with the properties of present fuels, it is larger than necessary for trans-Atlantic flights and could allow a further volume reduction. The San Francisco to Sydney distance is only 12000 km and stops in mid Pacific could be very attractive.

Before we waste time on radical new aircraft designs and ground-based landing systems, it is necessary to confirm that burning hydrogen in gas turbines at high altitudes will be a chemically appropriate solution. If we burn hydrogen in ambient air there will be no release of carbon dioxide but there will still be the formation of nitrogen–oxygen compounds collectively known as NOXes. If these are cooled very rapidly, as in the adiabatic expansion of an internal combustion engine, they can be ‘frozen’ at the high-temperature equilibrium state with lots of very nasty acids. The lower combustion pressure and slightly slower cooling of a jet exhaust should be less severe but we want to quantify the severity of the problem. There may even be problems from ice crystals formed from the exhaust. I have asked colleagues at the National Centre for Atmospheric Research at Boulder Colorado for an opinion.

There is one engine design in which the combustion products cool slowly enough for almost all the NOX production to revert to ambient values. This is the Stirling engine originating from 1815 but abandoned because of the absence of materials with good thermal conductivity and high hot strength. Much better materials are now available. By an extraordinary coincidence, the digital hydraulic systems needed for the speed and accuracy of the ground-based landing gear can also radically change the design of Stirling engines by using hydraulics to replace the crank and connecting rods of the conventional Stirling engine. A Stirling-engined aircraft would probably have to use a ducted fan or propeller propulsion but these could still allow civilian aviation to continue in a NOX-sensitive world.

The best way to do experiments on high-altitude engine-chemistry might be from a balloon. Do we know anyone with an interest in this area?