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<ul><li><p>9</p><p>Chapter 2</p><p>Ocean Water and Its Wonderful Potential</p><p>Gold from Ocean Water!</p><p>In the First World War (1914-18), Germany was defeated. The countrywas ruined, and on top of that, the victorious nations demanded hugereparations. It was soon recognized that the only way out of this state ofpoverty was recovery through technological progress. An Association wasfounded to promote this.</p><p>The Association took the initiative in many fields of research, butamong one that attracted the nation was an oceanic survey. Its purpose wasto extract the gold dissolved in sea-water, and use it to settle Germanys warreparations. Using the warship Meteor, the project was to determine theconcentration of gold at various locations, and to study the structure andmechanisms of the ocean.</p><p>The Meteor carried out its survey, mostly in the South Atlantic, betweenMarch, 1925 and July, 1927 (Figure 4). The results showed that gold wasdissolved in a far lower concentration than had been expected: only 0.003micrograms (0.0000003 grams) per liter of sea-water. Extracting enough tomake a gold coin would cost far more than the value of the coin. This project,therefore, was not put into practice, but what is noteworthy about it is theepoch-making idea of extracting a metal from sea-water, which no one hadthought of before.</p><p>What is more, the results were obtained with the latest instruments andaccording to a meticulous plan, which made them extremely useful as datafor academic research. For example, the Meteor was the first to measure thedepth of the ocean with sonar waves, rather than the traditional method of aweighted rope lowered to the sea bottom. The depth sounder measures waterdepth by measuring the time taken for a sound it emits to echo back from thebottom of the sea. With this new equipment, continuous depth measurementbecame possible as the ship moved along, and the terrain of the sea bottomcould be studied in detail. Sounding techniques are now applied for a widevariety of purposes, including for instance tracing shoals of fish.</p><p>The Meteors oceanographic expedition aroused peoples interest inthe ocean, in much the same way as interest was aroused in the Apollo</p></li><li><p>10 Chapter 2</p><p>expeditions and the first man to step on to the moon.One after another, resources on land are being overmined to the extent</p><p>that the minerals we need have become hard to obtain on land. Table 1 showsthe concentrations of a selection of metals in the oceans, and compares totalresources on land and in the sea. As you will see, the amounts of somemetallic minerals are actually greater in the oceans than on land: they includenickel, zinc, gold and silver.</p><p>As more and more of the earths land resources are extracted, it goeswithout saying that the supply is going to run out; the oceans will be the</p><p>Figure 4. The Meteor made observations of water mass movement, water temperature, salinityand plankton at 310 observing stations, as well as obtaining 14 bottom profiles and making anumber of balloon observations.</p><p>Rio de Janeiro</p><p>Buenos Aires</p><p>Walvis Bay</p><p>Observing stationCurrent measurement</p></li><li><p>Ocean Water and Its Wonderful Potential 11</p><p>Earths greatest reservoir of metals. The German attempt to extract goldfrom sea-water in the 1920s may have ended in failure, but we are now at astage where the whole world must reconsider the oceans as a storehouse notonly of gold, but of other minerals as well.</p><p>It is easy to pump up sea-water in coastal areas. In this sense, extractingmetals from sea-water might seem easier than mining deep down into theearth for ores whose refining process involves extremely high temperaturesand large amounts of polluting waste. No such problems would arise in theprocess of extracting metals from sea-water as long as large quantities ofchemicals were not used. And so much sea-water is so easily available.</p><p>In that case, why not start right away? The problem is that we do not yethave the technology to extract such low concentrations of metals efficiently.Some chemists have claimed that, in their expert opinion, it would beimpossible, and have given up the attempt even before starting. But I canthelp feeling that there must be a method that has not yet been discovered. Forexample, there are marine creatures that do effectively concentrate outmetals such as mercury, lead or vanadium (Figure 5). But this process is stillonly vaguely known, and has yet to be explained.</p><p>To solve this problem, an entire set of new principles, and the epoch-making technology to put them into practice, are required. Mankind hasnever tired in the search for new horizons, and surely one great dream for thefuture must be how to extract metals from the worlds oceans.</p><p>Unveiled Energy in the Ocean</p><p>The ocean is a reservoir not only of metals but also of energy. Dr. J. A.</p><p>Table 1. Concentrations of metals in sea-water, estimates of land reserves, and annualproduction</p><p>All amounts in megatons; concentration in micrograms per liter</p><p>Total amount Concentration Estimated land Annual production</p><p>Iron</p><p>Aluminum</p><p>Nickel</p><p>Tin</p><p>Copper</p><p>Zinc</p><p>Lead</p><p>Gold</p><p>Silver</p><p>Mercury</p><p>reserves</p></li><li><p>12 Chapter 2</p><p>dArsonval, a French physicist, was the first person to think of exploiting theoceans energy.</p><p>It is well known that the waters in deep seas and lakes are warmed uponly near the surface in summer, while their deeper parts remain cool.Unfortunate accidents sometimes happen when someone dives into a lake inthe mountains: deceived by the temperature at the surface into believing thewater is warm, they are shocked by the cold deeper down, and die of a heartattack. Generally sea-waters in tropical zones also have a significanttemperature difference between their surface and their depths; there, it isconstant throughout the year because of the high atmospheric temperature allyear round.</p><p>In 1881, Dr. dArsonval proposed generating electricity using thetemperature difference between the sea surface and its lower depths which,in tropical zones, is about 30 degrees Celsius. This was a unique idea, andat first it drew some public attention; but 1881 happened to be the year thefirst thermal power plant started operation in the United States. No onebelieved that a temperature difference of only thirty degrees could generateelectricity like the high temperatures that were used, by burning coal, toproduce the steam to drive the turbines in a power station. No one evenattempted to experiment with this idea.</p><p>It would probably be best to explain here how electricity can begenerated by exploiting the oceans temperature difference. It is actuallyquite a simple principle.</p><p>Figure 5. Some marine organisms accumulate metals: tunicates concentrate out vanadium.</p><p>Tunicates</p><p>Metal Refinery</p></li><li><p>Ocean Water and Its Wonderful Potential 13</p><p>Generally water boils at 100 degrees Celsius, but this happens onlywhen the atmospheric pressure is exactly 1, on land near sea level. At thesummit of a high mountain like Mt. Fuji (3,776m), the rarity of the atmospheremeans that the atmospheric pressure is only 0.62, and water boils at only 86degrees. Therefore, because the water temperature does not go high enough,rice cannot be cooked well at the top of Mt. Fuji.</p><p>This means that water could boil and turn to steam at, say, 30 degreesCelsius if atmospheric pressure was sufficiently low. Electricity would begenerated if that steam was sent to a turbine to turn a generator. On land nearsea level, the air in a chamber could be reduced to create low pressure, andthen water in the chamber would boil. But the steam made in this way wouldturn the turbine only once. The turbine would turn continuously only if sucha condition could be repeatedly produced.</p><p>For this purpose, the steam must be turned into water again after turningthe turbine, so that it can be boiled over again. It is easy turning steam intowater. In winter, the water vapor in a warm room is condensed by contactwith the cold glass of a window, and water drops drip down the window.This is the same principle: air containing water vapor should be cooleddown.</p><p>Dr. dArsonval thought that generation of electricity would be possibleby utilizing warm sea-water for boiling water, and cool deep ocean water(DOW) for cooling it down. In other words, the solar energy stored up in sea-water could be exploited in the form of electricity.</p><p>It is a common misconception that water boils at 100 degrees Celsiuseverywhere, since we live normally under conditions of one atmosphericpressure. The idea of generating electricity by temperature difference seemsstrange, because we often do not consider the effects of pressure differences.It is another misconception that every liquid boils at 100 degrees Celsius. Atone atmospheric pressure, ethyl-alcohol, for example, boils at 78 degrees</p><p>Figure 6. Dr. J.A. dArsonval</p></li><li><p>14 Chapter 2</p><p>Celsius, ammonia at 33.5 degrees Celsius below zero, and propane at 42.1degrees Celsius below zero.</p><p>Dr. dArsonvals idea received attention again in the twentieth century.In one Italian journal a scientific paper entitled Utilization of Solar Heatappeared: it discussed the utilization of the temperature difference in lakewater. In a deep lake in northern Italy, there is a 16-degree temperaturedifference in summer, since its surface temperature rises to 24 degreesCelsius, while the temperature at the bottom remains at 8 degrees Celsius. Acost estimation was made for operating an electric generator of 14,000kilowatts, utilizing such a temperature difference. This would be the firstattempt to estimate the cost of thermal difference generation.</p><p>Another paper was published by an American engineer in the journalEngineering News. In this paper, he discussed the problem of the insufficientdensity of the steam produced by sea-water in order to turn a generator. Itis certainly true that steam produced under low pressure is poor, just like airat high altitudes. Thus, compared with steam produced at a pressure of oneatmosphere, such steam would require an enormous turbine for generatingthe same amount of power.</p><p>Therefore, in this paper he proposed using some other high vapordensity liquid rather than water in a low pressure chamber. Since high vapordensity liquid turns into a heavy gas, he proposed using propane or ammonia.Water turns into only 0.337 grams of vapor when it boils at 32 degreesCelsius under low pressure in a one-liter flask, while on the other hand, therespective figures for methane, ammonia, propane, and fluorine (i.e.,chlorofluorocarbon) are 0.64 grams, 0.69 grams, 1.81 grams, and 4.55 gramsunder the same conditions. Even air turns into 1.16 grams.</p><p>In other words, such liquids are boiled with warm sea-water to producevapors heavier than steam, and once these vapors have done their job ofturning a turbine, they are condensed back into liquid form by cold sea-water. This cycle of boiling, condensing and then boiling again uses sea-water indirectly on some other substance. It is known as a closed cycle,and has been successfully developed. A cycle that actually turns water intosteam is called an open cycle.</p><p>Professor Claude, the Pioneer and His Challenge</p><p>The proposals so far reviewed were no more than proposals, which werenot actually subjected to experiment at the time. It was two French professors:G. Claude and P. Boucherat, President of the French Electric Society, whofirst carried out experiments on electric power generation utilizing thermaldifference (Figure 7). Using the small apparatus shown in Figure 8, theyperformed a public experiment at the French Academy of Sciences onNovember 15, 1926. The experiment was reported in detail by a leading</p></li><li><p>Ocean Water and Its Wonderful Potential 15</p><p>French newspaper: Paris Presse. With the press in other countries takingup the story, the worlds attention was attracted.</p><p>The British journal The Engineer reported on November 20, 1926:The wheel of an ordinary Laval turbine, 15cm. diameter, wasmounted with its spindle vertical inside a glass flask and arrangedto drive a tiny dynamo. The bottom of the glass contained lumpsof ice, and air could be exhausted from it by a vacuum pumpconnected to the upper portion. Another flask, containing 25 litresof water at a temperature of 28 degree Celsius, was provided withan outlet in the form of a pipe which entered the first flask andterminated in a nozzle just above the blading of the turbine wheel.When the system was exhausted of air the water in the second flaskboiled, its vapour passing away through the pipe and driving theturbine wheel. After leaving the wheel the vapour was condensedby the ice in the bottom of the flask. It is said that the turbine wheelwas driven by this means at a speed of 5000 revolutions per minute,and enough power was obtained from the dynamo to light threelittle electric lamps for eight to ten minutes, after which the waterhad been cooled to 20 degree Celsius or so by its evaporation andapparently refused to boil any longer.This was the first successful experiment to produce electricity from a</p><p>small thermal difference. Although it was really a primitive one, it arousedpublic interest in thermal difference power generation, which came to becalled in English Ocean Thermal Energy Conversion, or OTEC. Generationceased soon after the experiment was stopped, but it could have continued if</p><p>Figure 7. Professor G. Claude, the pioneer</p></li><li><p>16 Chapter 2</p><p>the warm water had kept its temperature and cooling had been donecontinuously with cold water. This is the principle of the open-cycle model:supplying warm water continuously to produce steam (the vaporizer) andcold water to condense the steam back to water (the condenser) (Figure 9).</p><p>At a press conference after his experiment, Professor Claude providedthe following figures: The surface temperature of tropical seas is generally</p><p>Figure 8. Generating electricity by temperature difference</p><p>Vacuum pump</p><p>Generator Nozzle</p><p>Lamps Turbine</p><p>Steam</p><p>Ice</p><p>20l warm water(28C)</p><p>Figure 9. An open-cycle</p><p>Water vapor</p><p>Evaporator</p><p>Mist of surface water</p><p>Warm surface water</p><p>Discharge</p></li><li><p>Ocean Water and Its Wonderful Potential 17</p><p>between 26 and 30 degrees Celsius, varying within a range of 3 degreesCelsius throughout the year. On the other hand, at a depth of 1,000 metersit is 4 to 5 degrees Celsius all year round. If 1,000 tons each of surface sea-water and DOW were used per second for OTEC, even using a steam turbineof 75% efficiency (i.e. a turbine that converted 75% of the energy itconsumed into electricity), it would be possible to generate 100,000 kilowattsof electricity. Moreover, the cost of construction would be lower than forthe most economically constructed hydropower generation plant.</p><p>The American and British press criticized him as too optimistic, butProfessor Claude was not discouraged by such criticisms and attempted withhis own assets a large-scale experiment to collect the necessary data forputting his theory into practice. First, he experimented with a 60-kilowattturbine using warm waste water from a Belgian steel works and cold seasurface water. Thr...</p></li></ul>

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