The Worst Power-Generating Scheme in the World
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Consider a little-known feature of the diesel-electric locomotives that we see pulling freight trains hither and yon on our railroads-- dynamic braking. The locomotive uses a diesel engine to drive an electric generator and uses the generated electricity to run electric motors built into the wheel-sets, which motors exert the torque that generates the thrust to move the train. That design enables an elegant solution to the problem of slowing and halting a massive freight train: instead of applying the mechanical brakes, the typical brake shoes pressed against brake drums, the engineer moves a lever that reconfigures the electric motors in the locomotive's wheel-sets into electric generators. Those generators convert the kinetic energy of the train's motion into electricity that heat metallic grids on top of the locomotive and drives fans that blow air over the grids to prevent them from melting. In that way the dynamic braking slows the train down or reduces its acceleration when it moves down a mountain grade.
Can we use that mechanism to devise a method of generating electricity that has a worse effect on the environment than does the burning of coal? Oh, yes, indeed we can. In fact, we can do so with such ease that it raises the question of whether we humans are actually stupid enough to use it. Just consider the process of converting gravitational potential energy, like that used in hydroelectric power but using a resource vastly less renewable than river water, into usable energy.
In concept the method follows an amazingly simple plan. Build electric railroads from sea level to mountain tops, then load rock blasted off the mountains onto electric cars and run them as generators as they descend the track. Finally dump the rock into an oceanic trench, using a floating wharf similar to the Hood Canal floating bridge in Washington State, and then send the cars back up the mountains to repeat the process.
Consider a simple example of this system, which we hope no one will ever build. We want to survey a track from the little Peruvian coastal village of Barranca, north of Lima, to Nevado Yerupaja, which looms 6634 meters above sea level roughly fifty kilometers inland. The builders then lay a double-tracked line across the coastal plain and into the mountains. At the same time they begin building the concrete boxes that make up the floating wharf, towing them to the wharf site near Barranca, then assembling and anchoring them in position.
As they lay the track, the builders put down the standard-gauge running rails and then lay a conductor rail (the infamous"third rail") on ceramic insulator blocks between them. The conductor rail provides the electric traction power necessary to propel 20-tonne hoppers along the track and up into the mountains and also takes the electric power that the hoppers generate as they descend back to sea level. To protect the conductor rail from rain and snow and to protect anyone who might stumble and fall onto the conductor rail, the builders erect a wood or plastic "parasol" over the rail with its supports on one side of the rail so that the contact shoe can come onto the rail from the other side. This would look familiar to anyone who has ridden the New York City subway system, especially where the trains run above ground, although in New York the conductor rails run on the outside of the track, attached to the ends of the sleepers.
When the builders take their construction project into the mountains they can begin to generate electricity with the system. As the double-tracked line ascends through valleys and on ledges cut into the rock, twenty-tonne hoppers go up and down the line, generating electricity while removing the rubble produced in the construction. The combination of the torque in the motors and the grade at which the track ascends into the mountains allow the empty hoppers to go up the track, but when filled with seventy tonnes of rock each hopper becomes too heavy for the grade and goes down the track backward, its motors running as generators that feed their output into the third rail. At the end of the line the two tracks merge through a switch and the line ends at a short spur where a conveyor belt loads each empty hopper as it comes into position.
Ultimately descending 6000 meters to sea level, the system yields almost 4.2 trillion joules per hopper of net output per load. If a hopper takes three hours to traverse the system (both coming and going), then we get an average of 420 megawatts from each hopper. At roughly 2.3 billion tonnes, one cubic kilometer of rock descending from 6000 meters to sea level would generate that 420 megawatts for 98.6 million hours or 11,248 years. But, of course, that cubic kilometer will get used up much faster than that calculation implies, and then the next cubic kilometer, and then the next.
When the loaded hoppers come out of the mountains and the grade of the track diminishes, the third rail ends. Unable to move any electric current, the motors turn freely and the hoppers coast to the floating wharf. At that time the wharf already extends to its maximum length, its last segment floating above the oceanic trench where the Pacific Ocean plate gets subducted under the South American plate. Each hopper comes to the end of the line, which sits over an opening in the concrete box supporting the track and doors on the car's bottom swing open, allowing the hopper's cargo of blasted rock to fall into the trench. Then the hopper moves through a switch onto the ascending track, its contact shoes touch the third rail again, and the hopper goes charging back up the wharf, across the coastal plain, and up into the mountains for another load of rock.
Eventually the builders bring the line to the highest point in the mountains and the main production phase can begin. At the upper end of the line the scene will resemble a giant open-pit mine, where rock gets blasted out and loaded onto rail cars. A continuous stream of hoppers comes up the track onto what looks like a vast marshaling yard. Automated systems direct the hoppers through switches to the ends of the various spurs, where conveyors will load them with rubble. Once filled, the hoppers will go back through the switches and onto the descending track, generating electricity as they go back down the mountain.
And how much power, in theory, could this system generate? With an average altitude of 4000 meters, a width of about 200 kilometers, and a length (in Peru, as our example) of roughly 1600 kilometers (320,000 square kilometers), the Andes provide 1,280,000 cubic kilometers of rock falling an average of 4000 meters. That would enable Peru to generate 100 kilowatts for each and every member of the human race (currently approaching seven billion) for 5,760 years.
But such a system would exact a terrible cost. Year by year, century by century, the mountains come down. Pristine landscapes get ripped up. Whole ecosystems die. History evaporates as sites like Machu Picchu and Cuzco get torn down and dumped into the oceanic trench like so much trash. And this system doesn't destroy only mountains: without the vast rain catchment of the Andes to fill its rivers, the eastern part of South America becomes drier, less hospitable to the great forest of Amazonia.
Technically this system uses a renewable resource. The process of subduction pulls the broken rock down into Earth's mantle, where the seawater mixed with it acts as a flux, allowing the rock to melt and flow up into the roots of the Andes. Like water rising into a plant, the molten rock rises into the volcanoes that continue to create the Andes. Unfortunately, the process takes millions of years to take a certain load of rock and return it to the tops of the mountains. Thus, even though in takes millenia, the process results in the leveling of one of the world's great mountain ranges.
This is the real shoot-n-shove and every bit as despicable as what goes on in West Virginia. If anyone ever uses this method of generating electricity, then we can reasonably consider modern civilization a total failure. So why do I describe a system that I hope no one ever builds? I hope that reading this description brings your blood to a boil and inspires someone to conceive a better way to generate electricity.
And what hope do I have that no one will actually attempt to use this plan, that no one or no group will be so short-sighted (i.e. stupid) as to put self-interest ahead of the broader and deeper interests of Humanity? Let me repeat what I have said before: the phrase Homo sapiens is the funniest joke in taxonomy. We humans are not inherently intelligent. Over a span of many millenia we have developed intelligence more as a cultural trait than as a natural endowment. If properly trained and conditioned in childhood, we can fake intelligence, but, like the dancing bear, we don't do it often and we don't do it well. Bummer!
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