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Although you may have heard that taking public transit can help reduce our reliance on fossil fuels, most buses today still run on either diesel or natural gas. Sure, there are some fascinating developments on the horizon, such as battery-powered EV buses, potentially hydrogen, and the hyperloop. But what if there was another world where public transit didn't require fuel or batteries? This urban commuter dream turned out to be a reality for a limited period of time.
The Gyro Bus:
The gyro bus was a milestone vehicle that, despite its short lifespan, addressed a modern problem with an ancient technology: the flywheel. So, how did the bus function? In the first place, what is a flywheel? Why did the gyrobus disappear from the face of the earth? Is it possible that the underlying technology will make a comeback? Let us try to answer this question and uncover a potential method of transport that would help humanity in this post.
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| Gyrobus G3, the only surviving gyrobus in the world (built in 1955) |
In the 1940s, Swiss engineers at Oerlikon began experimenting with new modes of public transit. They were specifically seeking for something that was quieter and cleaner than the normal gas-guzzling buses. While other high-density metro regions began building trolley systems, the Swiss cities discovered that integrating this new technology was difficult and costly. Trolleys need cables to move, which limits their movement to predetermined paths. It was expensive to install new overhead lines, and the batteries that powered the buses at the time were not as advanced as they are now. This bus appears simple from the exterior.
With no internal combustion engine and no chemical batteries, though, it's what's on the inside that makes it truly unique. The flywheel, one of the oldest devices in human history, was the source of this amazing spark of invention. So, what is a flywheel, exactly?
The Flywheel :
Flywheel isn't something you put on your car. A flywheel is essentially a giant mechanical battery that turns one kind of energy, such as electricity, chemical energy, or mechanical energy, into kinetic energy. An electric motor rotates a massive mass around an axis that accelerates to high rates of speed, storing rotational energy in the process. When the motor is shut off, it acts like a generator, sucking mechanical energy from the spinning mass and reversing the process to generate electricity. Regenerative braking and electric vehicles are examples of this. This property turns the mechanical flywheel into a rechargeable energy storage device.
The amount of energy in a flywheel can be described by the following equation:
E = ½ I ω^2.
where the rotational energy (E) is equal to one-half times the rotational inertia (I) times the rotational velocity squared (ω^2). Let's break this down a little bit to better understand.
‘I’ is the rotational inertia of how difficult or easy it is to get a body spinning. the equation for the rotational inertia is as follows,
I = m r^2
where M is the mass in kilograms and r is the distance of the mass from the center of rotation squared in meters. If we substitute this value for rotational inertia into our energy equation we get the amount of energy in the flywheel.
Modern flywheels require a few key components to attain their full potential. First, there's a massive rotating cylinder on top of the stator. Bearings, the fixed portion of a rotary system, support the rotor by helping it in resisting forces and allowing it to spin at high speeds. Flywheels' kryptonite is friction. To function correctly, early systems required high-performance lubricants. Modern systems have magnetic bearings that levitate, effectively eliminating the need for maintenance. Most current flywheels are contained inside a vacuum chamber to decrease drag and friction while reducing losses and enhancing efficiency.
While early versions were built of steel, modern flywheels have more exotic materials on the interior, such as carbon fiber, which allows for heavier loads to be placed further away from the center of gravity. Flywheels are attached to motor generators for obvious reasons, and they may then provide and receive electricity from the energy grid. Flywheels nowadays may spin at rates of up to 100,000 revolutions per minute (RPM), allowing them to store even more energy.
This is starting to sound a little scary. Remember that storing a high quantity of energy in a short space is always similar to storing a large barrel of gasoline, a large compressed tank of hydrogen, or a large battery pack. Engineering mitigations and safety concerns are the most important factors. The most astonishing thing about flywheels is that they're not new; in fact, they first emerged in potter's wheels before 2000 B.C.
Gyro Bus - Story :
Let us return to our magical vehicle. Flywheels were the ideal solution for Switzerland's rising transportation challenge because of their tremendous power and efficiency. Finally, there was an alternative for a zero-emission electric bus, and best of all, it didn't require any wires or strings to keep it in place. While the bus was stopped at stations, it had an electric engine that was powered by grid electricity. When the bus was completely charged, the engine revved up the flywheel to roughly 3000 rpm, storing all of that energy to keep the bus running. Depending on the bus load and travel conditions, these buses could travel up to six kilometers at speeds of 50 to 60 kilometers per hour. One bus installed in Verdun (Lebanese), reportedly traveled up to 10 kilometers on a single charge.
An Idea into Work:
The bus was charged as it travelled along the route from one charging point to the next. The bus was powered off the grid by three booms put on the roof. There could be four charging stations along a four-and-a-half-kilometer stretch. Charging from a standstill could take up to 40 minutes, but once the wheel was up and running, adding more power to the wheel required just two to five minutes, almost the same amount of time it took to drop off and pick up passengers.
This meant that running a regular bus route, where passengers are loaded and unloaded in a matter of minutes and most stops are only a few miles apart, was totally feasible. The wheel was located right within the bus's cabin, next to the passengers. To lower pressure and keep resistance low, the one-and-a-half-ton wheel was contained in an airtight enclosed chamber filled with hydrogen gas.
Limitations and Unavoidable Conditions :
But, having a giant spinning wheel inside a bus has some unexpected effects. Some are amazing, while others are not. On the one hand, riders claim that the flywheel provided a noticeably smoother ride. There are no clunky gear shifts, no gas engine vibrations. A gyroscopic effect, on the other hand, led a bus to resist changes in direction, making tasks like turning much more difficult at its peak.
From the 1940s until the 1960s, cities all around Switzerland began to embrace these innovative buses. They made it all the way to Belgium. Congo, which had the largest fleet of 12 vehicles travelling across four routes, was a hit at first because it was the quieter, cleaner unrestricted bus.
There are a few reasons why we don't see gyro buses on the road today. For one thing, the wheels frequently encountered a significant issue with wear and tear, particularly in Congo, where drivers would frequently take shortcuts across unpaved roads, causing the bearings to wear out and eventually destroy the system.
Sensible firms were also worried about putting a large steel wheel spinning at really high speeds so close to passengers. A three-ton flywheel was necessary for a bus carrying 20 passengers, but it was energy usage that put the last nail in the coffin. The bus operators determined that 3.4 kilowatt hours per kilometer for each bus on the road was simply too expensive. As a result, the gyro bus's wheels have stopped spinning, and just one vehicle survives totally intact in Antwerp's Flemish tram and bus museum.
Was that the final chapter of Flywheel Tech?
Was this the end of the line for flywheels as well? Not exactly, to be sure. While flywheels are unlikely to appear in buses or electric vehicles in the near future, they have made their way into other fields, particularly in grid energy storage. Flywheels continue to use significantly more environmentally friendly materials than many chemical batteries do today. They also have a high energy density and efficiency, reaching up to 90% in some cases. They're resistant to temperature changes and can survive for decades with little or no maintenance. The James Watt steam engine's flywheels have been spinning nonstop for nearly 200 years.
As a result, this ancient technology has been given new life in the form of uninterrupted power supplies that provide backup power to critical loads. They've been employed in planes, trains, and even NASA's G2 spacecraft and the International Space Station to maintain the station in a constant position relative to the earth's surface.
They excel at providing ancillary services for frequency regulation and power fluctuation support in grid applications. This is especially true for renewable energy sources such as solar and wind, whose production varies throughout the day. The world's largest flywheel energy system is located at the beacon power facility in Stevenson, New York. The 20 megawatt system is a significant milestone in the field of flywheel energy storage.
According to research, wind turbines featuring flywheel technology as an energy storage alternative produce more electricity during peak times. While flywheels are expected to be used inside electric vehicles, Israeli startup Chakra Tech is working on EV rapid charging stations that employ kinetic batteries based on flywheel technology.
While technology like lithium-ion batteries are making great strides and bringing renewables to the forefront, we can't rule out other technologies, even if it's from several thousand years ago.
And that is it about the flywheel and gyrobus.
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Sources,
Copex, J.P., Le gyrobus d'Yverdon fête ses 50 ans, Tram magazine, No76/12.2003-02.2004, pp34-46.
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