The Mechanical Battery

We are in the beginning stages of a massive paradigm shift and in the way we manage and use energy, the slow but steady push has begun to shift from fossil fuel consumption to renewable energy sources, and from power grids to transportation. This evolution largely depends. a fundamental group of technologies that store energy, although more commonly known by its electrochemical variant, a

battery

or accumulator is a device that stores energy, batteries fundamentally allow us to decouple energy supply from demand, they can store energy in many forms, as chemical, thermal or

mechanical

, and some can even be created on very large scales, for example, the water contained in a dam in a hydroelectric power plant forms a gravity

battery

that stores energy in the elevated mass of water, the stored energy and the Compressed or heated flutes can also be used as batteries, however, in terms of energy density, cost, and mass production capacity, none have been as prolific as the electrochemical battery found in virtually all consumer devices. portable, countless industrial applications and in most hybrid and fully electric vehicles.

Lithium-ion-based electrochemical batteries have been at the forefront of practical applications with high energy density. and easily mass-produced rechargeable battery technology for more than 20 years, but a much less well-known

mechanical

ly based rechargeable battery is showing a resurgence of interest and had its commercial start in the 1950s powering a peculiar Swiss bus developed by the Swiss oil company Caan in the 1950s. In the late 1940s, the Gyro was an electric bus designed to operate quietly along short-distance, low-traffic routes. We are installing new traditional trolley bus power lines. It was not feasible. What made the gyrobus so unique was that instead of traditional chemical batteries or internal combustion.

The engine was driven by a large 1,500-kilogram flywheel sealed in a low-resistance hydrogen-filled chamber that rotated at up to 3,000 rpm. Power was transferred to the flywheel by an induction motor driven by three arms mounted on the roof of the bus. It would contact elevated charging points along the route, such as at passenger stops, providing up to 500 volts to turn the steering wheel and propel the bus. The charging motor would be reconfigured as a generator, transforming the rotational energy of the flywheel into electricity that would later be used for driving. a traction motor the traction motor was also used as a regenerative brake converting the kinetic energy of the wheels back into electricity powering the steering wheel motor charging it further these early gyroscopic buses could travel up to six kilometers on flat terrain at a speed of up to 60 km/h with a three-minute recharge at idle, the steering wheel would continue to turn up to 10 hours later, the variants deployed in the Belgian Congo were some of the largest examples carrying up to 90 passengers, although they required recharging every two kilometres, in Ultimately, all of these early vehicles suffered from the inability to utilize much of the stored energy.

Excessive wear and tear and reliability issues made them unaffordable to keep in service. The concept of flywheel energy storage was one of man's first ways to store energy. Mechanical energy The potter's wheel, one of the earliest examples, uses the flywheel effect to maintain its energy under its own inertia. Flywheels were also used in water wheels, lathes, hand mills, and other rotating objects powered by both humans and animals. The energy storage characteristics of a flywheel provided a source of relatively smooth and uniform rotation due to the irregular force applied to it. The wheels of the Middle Ages eventually evolved in the 18th century, replacing their wooden construction with a huge piece of cast iron that was made for steam engines.

It was at the beginning of the Industrial Revolution that the term flywheel with a major moment was first coined. of inertia, these heavy flywheels converted the long, forceful reciprocating motion of a steam engine into smooth, usable rotational energy, literally powering the industrial revolution. The use of flywheels to convert reciprocating motion into rotational force would migrate from steam engines to the next evolution of the engine, the Internal Combustion Engine of the first three-wheeled vehicle built by Karl Benz in 1885: the technical marvels of modern engines . All internal combustion engines require some type of flywheel to operate beyond their purely mechanical use in reciprocating engines.

The main developments occurred at the beginning of the 20th century. When the rotor shapes and rotational stresses were thoroughly analyzed and the flywheel was now considered as a potential energy storage system known as FES or flywheel energy storage systems, much like the system used in the gyrobus, these They normally use electricity as work energy. The energy to a flywheel The energy storage system is drawn from an external electrical energy source, such as a power grid. The flywheel accelerates as it stores energy and decelerates as it discharges to deliver the stored energy. The rotating flywheel is coupled to an electric motor generator unit. which performs the exchange of electrical energy to mechanical energy and vice versa the energy storage capacity of a flywheel is mainly determined by its shape and material known as flywheel rotor in most flywheel energy storage systems its capacity is linearly proportional to the moment of inertia or the resistance to angular acceleration and the square of its angular velocity in effect increasing the rotating mass optimizing the shape or increasing the rotational speed of the rotor allows it to store more energy in practice these three properties are limited by Various design factors The usable rotational speed range of the system is limited by the voltage variation limits of the motor-generator system.

If the rotor speed falls below a minimum limit, it will produce two bars of voltage by unloading the rotor from the steering wheel, while turning it too fast during load can exceed those motor limits. Generator These limitations of the motor-generator system itself will always result in a region of inaccessible energy storage capacity within a flywheel energy storage system. The power output and electrical efficiency of flywheel energy storage systems are also implicitly limited by those of the permanent magnet synchronous motor generator. Motors tend to be the most commonly used electrical machines in flywheel energy storage systems due to their 95.5% efficiency, high power density, and low intrinsic losses beyond the limits of the motor generator.

The maximum speed limit at which the flywheel rotor can operate is also determined by the voltage. The strength of the material it is made of as rotor rpm increases and hoop stresses within the rotor exceed the tensile strength limits of the material, the rotor will begin to break. The cast iron flywheel is used in early steam engines and was too weak for high rpm. use better performing alloys made of titanium, magnesium, aluminum and steel. Compounds that offer up to 20 times more tensile strength were developed, such as fiberglass and carbon fiber reinforced polymers, further increasing the tensile strength of the steering wheel, easily doubling the capabilities of high-performance metals, although at higher cost because the shape of a flywheel rotor affects its moment of inertia and inherently its energy storage capacity, the efficiency with which the mass of the material used is utilized is determined by the form factor of its geometry.

Cylinder-based geometries tend to have lower form factors depending on their wall thicknesses, while solid discs use more mass of the material, new disc-shaped rotor geometries approach near-perfect form factors, but they are limited to low-speed metal constructions. In practice, the choice of steering wheel shape and material is determined by its application, requiring a balancing act between specific characteristics. energy or energy per mass and energy density or energy per flywheel volume, automotive applications, for example, might favor energy density as a goal due to packaging requirements, while network storage systems may focus more on the specific energy. Flywheel energy storage system designs generally fall into one. of two strategies: low-speed flywheel systems that operate below 10,000 rpm and high-speed variants that can approach 2,000 rpm.

Low-speed flywheels are usually made of heavier metal materials and are supported by load-bearing mechanical or even non-contact magnetic bearings. With magnetic levitation, high-speed flywheels typically use lighter, stronger composite materials and require magnetic bearings because flywheel energy storage systems typically enclose the flywheel within a vacuum to reduce friction. The main point of energy loss occurs in the bearings that support the flywheel. The bearing supports the flywheel but also resists the forces resulting from its change in orientation, especially the persistent rotation of the Earth, these changes being resisted by the gyroscopic forces exerted by the flywheels. The angular momentum that exerts a force against the bearing system.

Traditional mechanical bearings like those. used in gyroscopic bus and other simple low-speed flywheel energy storage systems suffer from high maintenance requirements and a dependence on high-performance lubricants to operate are particularly sensitive to gyroscopic forces and friction generated by mechanical bearings losing around In comparison, magnetic bearings have no friction losses and do not require any lubrication, but may require energy to energize them in some configurations. Magnetic bearings come in permanent magnets, active magnet variations, and superconducting. Pronet magnetic bearings are passive rigid. They are low cost and suffer low losses due to lack of current flow, but this comes at the cost of having limited stability.

Permanent magnetic bearings tend to be combined with active magnetic bearings as a backup auxiliary bearing in cases of overload or failure. The bearings produce their magnetic field from a current-carrying coil that controls the position of the rotor; positions the rotor through a feedback system by applying variable forces that are determined based on the deviation of the rotor position caused by external forces. Active magnetics are high-cost systems that require complicated control Mechanisms that consume energy to operate, increasing the overall losses of the bearing system. Magnetic bearing systems are capable of reducing parasitic losses to approximately 1% of the total flywheel storage capacity per hour.

Superconducting magnetic bearings provide the best solution for high speed flywheel power. storage systems that offer compact, durable and stable operation, without friction, stabilize the flywheel without electricity or positioning systems through the Meissner effect, expel their own magnetic field and create stable levitation. Superconducting magnetic bearings reduce losses to well below 0.1% of the flywheel's Stowell storage capacity. per hour, however, this incredible efficiency comes at a high cost as they require a cryogenic cooling system to maintain superconductivity beyond the flywheel rotor. The housing of a flywheel storage system those statics must be designed with containment in mind, They are generally designed to resist the forces of near-vacuum at low pressures within the device, as well as can contain the release of energy from catastrophic failure of the flywheel.

Considerations regarding the heat generated by the engine generator must also be taken into account in the design. Some experimental housings even employ a limited or even a full-motion gimbal mounting system to reduce losses caused by ground gyroscopic effects and even vehicle motion. One of the most attractive features of flywheel energy storage systems is their reliability; can reach life cycleshigh, easily reaching hundreds of thousands. of charge and discharge cycles without degrading, they also offer a long overall lifespan that easily lasts for decades and typically require little to no maintenance. The cargo discharge performance is also favorable. Offers a quick response.

High energy efficiency and high discharge rates. Its charging status is. They are also easily measured by rotation speed and, unlike chemical batteries, are not affected by lifetime temperature or depth of discharge, produce no emissions, and are easily manufactured from non-hazardous materials. For the enviroment. In theory, flywheel energy storage can reach energy densities far beyond chemical ones. batteries, but in practice the current state of materials science limits this, especially in portable use cases. Say we wanted to replace a 100 kilogram lithium-ion battery pack in a hybrid vehicle with a flywheel energy storage system to achieve the 26 kilowatt hour capacity of the Battery Pack with a hundred kilogram flywheel, you would need to measure a meter and spin it at over 37,000 rpm to achieve this.

At this speed, the outer edge of the steering wheel would be rotating at more than 11 times the speed of the sound package and would safely contain the steering wheel. The energetic mobile component would be cost prohibitive with current materials compared to chemical batteries for similar performance within the limits of current technology. Flywheel energy storage systems are most suitable when high bursts of energy are needed for a short period. Their power density far exceeds that of chemical batteries. Easily delivers hundreds of kilowatts in seconds with little to no degradation and low long-term operating costs. One of the most common uses of flywheel energy storage systems is as uninterruptible power supplies.

They excel at providing short-term search power for data centers, hospitals, and others. Critical infrastructure sites that cost significantly less than their battery equivalent. Flywheel energy storage systems are also used in a similar way at the power grid level, providing an energy storage buffer to balance sudden changes between energy supply and consumption. Several grid-level facilities offering 2 to 20 megawatts of storage capacity with 15-minute discharge durations have been built throughout the United States and Canada. Demonstration projects based on storm wind power have also been built in California on smaller scales. Flywheel energy storage systems have been used when short bursts of power are needed without overloading power supply systems.

Notable examples of this are installed in various physics laboratories around the world, including many fusion experiments where megawatt bursts of energy are needed to energize electromagnets for a few seconds. The joint European toroidal plasma physics experiment, for example, has two 775-ton flywheels that spin at 225 rpm and can deliver up to 400 megawatts of power in the span of a few seconds. Short bursts of power provided by flywheel energy storage systems have been used for propulsion. on roller coasters to avoid overloading the local power grid the electromagnetic aircraft launch system on the Jerell are Ford-class aircraft carriers also use this principle each flywheel energy storage system can charge up to 35 kilowatt hours of energy in 45 seconds from the ship's power system and unleash everything in less than three seconds by propelling the plane off its deck through a purely mechanical system.

The concept of the Flybird flywheel kinetic energy recovery system was originally developed by John Hilton and his team when he was technical director of the engine division at Renault F1. In 2006, the Flybird system, now commercial, uses a continuously variable transmission to recover energy from the powertrain during braking on a steering wheel. The stored energy is then used during acceleration by altering the CVT ratio, improving acceleration and potentially improving fuel economy. The steering wheel inside the flybridge. The system can store up to 0.16 kilowatt hours of energy at a speed of 60 to 4,500 rpm in a relatively small lightweight package.

NASA is also experimenting with lightweight flywheel energy storage systems for spacecraft with its g2f ESS module design designed to spin up to 60,000 rpm and weigh just 115 kilograms, the carbon fiber and titanium-based system is designed to store half a kilowatt hour of energy with a charge discharge rate of 1 kilowatt, although the flywheel is one of the first forms of energy storage. Flywheel energy storage systems that are compact, reliable and energy efficient. Maintenance has been only a recent development as materials science has evolved and more exotic materials manufacturing processes and analysis techniques to develop future flywheel energy storage remain very promising even at a time when The cost of lithium-ion battery technologies and other chemistries continue to decline over time.

There is no need for exotic minerals. Minimal environmental impact and unprecedented reliability and longevity. One of man's oldest energy storage systems may prove to be the key to our future energy storage.