Mechanical energy storage equipment

Abstract

The device is suitable for mechanically storing renewable electrical energy with the aid of a dual- function electric machine and, when required, for feeding it back into the grid using the same machine. Energy storage is achieved through a heavy rolling weight (4) located inside the device, which moves vertically up and down while simultaneously performing a rotary motion, thereby changing its potential energy through gravity. For high mechanical efficiency, the moving components are mounted on rolling bearings. The position locking and motion initiation of the rolling weight (4) are carried out by the brake (8). Any rapid movement during uncontrolled downward travel, which could damage the structure, is reduced by a rubber block (6) and a damping spring (3).

Description

[0001] Description

[0002] Mechanical energy storage equipment

[0003] With the rapid spread of renewable energy sources, it has become increasingly necessary to store electrical energy produced by 'green,' environmentally friendly processes, which mostly depend on weather conditions and are often poorly aligned with user demand. At present, most available solutions rely on battery storage. Although battery-based storage systems have several advantages, they also have disadvantages. According to professional assessments, the availability of raw materials required for manufacturing batteries designed for this purpose is limited on our planet. The production process is comparable to that of a chemical plant and therefore cannot be considered truly environmentally friendly. The recycling and reprocessing of batteries that have reached the end of their service life is still in their early stages. It is therefore a realistic and environmentally important objective, regarded as a primary task, to develop alternative mechanical energy storage solutions made from environmentally friendly materials that can be manufactured economically in large quantities without the need for special technical means. High efficiency, minimal maintenance requirements and a long, reliable service life are essential criteria. One of the simplest ways to store energy is to increase the potential energy of a given mass during storage by mechanical means, that is, by lifting it vertically. During discharge, that is, during energy use, the potential energy is reduced by lowering the weight. Pumped-storage hydropower plants operate on a similar principle. By reducing potential energy, the mechanical energy storage device, with the help of an electric machine and a dedicated control unit, generates electrical energy that can be fed back into the grid or operated in island mode. According to the current state of technology, there is no mechanical energy storage device available on the market. Publications on innovations and records held by intellectual property offices mention spring-based energy storage systems, but their storage capacity does not approach the daily output of 15 to 35 kWh achieved by a small household power plant. The typical characteristic of a spring is linear and uniformly decreasing, which makes it difficult to match the optimal operating point of an electric machine during energy discharge. The mechanical energy storage device described in this application is shown in cross-section in Drawing 1 Its main components are as follows:

[0004] 1 base body

[0005] 2 base bearing

[0006] 3 damping spring

[0007] 4 rolling weight

[0008] 5 rotor

[0009] 6 rubber block

[0010] 7 support bearing

[0011] 8 brake

[0012] 9 weight filling

[0013] 10 drive shaft stub

[0014] 11 guide plate

[0015] 12 roller

[0016] Energy charging and energy recovery are carried out through the drive shaft stub 10 in the form of torque by means of a dual-function DC or AC motor / generator electric machine connected to the shaft stub; this machine may be a custom-built unit or a commercially available model with mechanical speed-reduction gearing. It can be mounted on top of the device, attached to the drive shaft stub 10. The drive shaft stub 10 may be designed not only as the illustrated splined shaft but also in a coupling configuration. When the rolling weight 4 is in its lowest position, the device does not store energy. As soon as torque from the electric machine driven by the renewable energy source appears on the drive shaft stub 10, the rolling weight 4 begins to move upward along a curved, low-inclination path formed on the inner surface of the base body 1, similar to a screw thread or a serpentine road. As potential energy increases, the energy storage process begins. The rolling weight 4 is forced into rotation and steady ascent by the rotor 5 so that the rollers exert pressure on the vertical guide plates 11 inside the rolling weight 4. The rolling weight 4 rotates and, due to the inclined path, rises at the same time. In the opposite direction of movement, during energy discharge, the rolling weight 4 rolls downward along its curved path under its own mass with the aid of gravity, while through its vertical guide plates 11 it forces the rotor 5 and therefore the electric machine operating in generator mode into rotation. To reduce mechanical losses, both the rollers 12 mounted on the rolling weight 4 and those on the rotor 5 are equipped with rolling bearings. The base bearing 2 and the support bearing 7 on the rotor 5 also serve to reduce friction losses. Sliding plates may be used instead of rollers 12 on the rolling weight 4 and on the rotor 5, but in that case forced lubrication must be provided due to higher friction. Despite the lower mechanical efficiency, this alternative may be cost-effective in regions close to the Equator where sunshine hours are abundant. When the rolling weight 4 reaches its upper limit position, the mechanical energy storage device is in a state of maximum charge, and the brake 8 locks the rotor 5 and the rolling weight 4. In this state, energy can be stored without loss, regardless of temperature or time. To extract the stored energy, the brake 8 must first be released. The rolling weight 4 begins to move downward along its path under the effect of gravity, while the rollers of the rotor 5 brake it and rotate the drive shaft stub 10, thereby driving the electric machine. By controlling the excitation of the electric machine, both the descent speed and the amount of discharged electrical energy can be regulated. Energy discharge can be stopped by applying the brake 8. The brake 8 may be a band brake commonly used in mechanical engineering, or an electric parking disc brake used in vehicle technology may be applied. The latter offers the advantage of a self-locking mechanism that maintains the braked state even during a power outage. The brake (8) also prevents uncontrolled, rapid downward motion of the rolling weight (4) and its high-speed impact in the lower position. In large-scale, high-power devices, an additional second or third disc brake may be used for greater operational safety. If uncontrolled descent occurs due to a brake or control fault, the rubber blocks (6) and damping spring (3) absorb the resulting high kinetic energy, protecting the device from mechanical damage. The energy-storage capacity of the device primarily depends on the density of the material used for the weight filling (9) and on the lifting height of the rolling weight (4), that is, the length of its vertical movement. The height of the mechanical energy storage device, or the amount of potential energy stored relative to its footprint, is limited only by the manufacturable lengths of the base body (1) and the rotor (5). The taller the device, the greater the potential energy that can be stored relative to its footprint. Consequently, large energy-storage capacity can be installed on a relatively small surface area, even outdoors.

[0017] The following table shows, compared with water, how much more potential energy denser materials with higher specific gravity can store for the same volume:

[0018] It can be seen that for a unit volume, considering the sufficient availability of raw materials, concrete is the most economical option. Cast iron can also be considered, as its potential energy storage capacity is nearly three times that of concrete. Several heavy metals could serve as dense materials for this purpose, but their high price prevents widespread use. Due to its high density, uranium may also be suitable for storing potential energy. However, only so-called depleted uranium, that is, the U-238 isotope, is appropriate for this purpose, as its low-level alpha radiation can be blocked even by a sheet of paper. This material is a by-product of the nuclear industry. For reasons of safety and practicality, the weight filling (9) should not consist of bulk material but should be arranged circumferentially in steel cassettes similar to cake slices inside the rolling weight (4). Another advantage of this design is that the rolling weight (4) only needs to be filled with the cassettes after, during assembly, the rolling weight (4) and the rollers have already been placed on the spiral path within the base body (1) and are secured in a fixed position. In the event of maintenance or refurbishment, the rolling weight (4) can be removed using a hoist with a relatively low lifting capacity. The materials of the mechanical energy storage device are well-known, proven, and widely used in mechanical engineering. These include rolled and flat carbon-steel sheets, cast- iron and cast-steel components, rolling bearings and sliding elements, and the material of the weight filling (9) selected according to user requirements. According to current knowledge, all these materials are commercially available in sufficient quantities.

[0019] A similar device operating on the principle of gravity is described in patent application DE 102011 107200 Al dated 21.02.2013, which raises the energy-storing weight using a lead screw. The single lifting screw shown in the drawing must have a high lead angle so that during downward movement it does not become self-locking and can rotate the generator. Since the entire storage weight loads the screw, the threads are subjected to high surface pressure. A single column guiding the storage weight is likely insufficient to ensure stability. All sliding elements require careful lubrication to reduce friction losses, which increases maintenance costs. The gear drive and the two separate electric machines, each performing a different function, represent a good solution, as they offer several advantages in terms of control and operational reliability compared to a universal machine. As the height of the device increases, the risk of buckling of the lifting screw also increases, which may cause jamming.

[0020] In contrast, in the present application, the load of the rolling weight (4), which runs and rotates on bearing-mounted rollers along the curved ascending path, is distributed among the rollers, while the components responsible for lifting and the electric drive motor are loaded according to the 'sin a' function, depending on the magnitude of the curved path's inclination angle 'a'. In practice, this solution can be regarded as a kind of transmission, meaning that the rolling weight (4) moves upward during energy storage as if it were climbing a gently inclined slope. To ensure uniform energy output during discharge, the angle 'a' must be chosen so that the downward force component K = G sina, where G represents the combined weight of the rolling weight (4) and its rollers, exceeds the initial rolling resistance of the rolling bearings of the rotating components, namely the rollers (12), the base bearing (2), the support bearing (7), and the electric drive motor. This ensures that when the brake is released, the rolling weight (4) begins to descend under the force of gravity and drives the electric machine. Increasing the angle 'a' results in a higher discharge speed. The instantaneous discharge power of the system, that is, the torque appearing on the drive shaft stub (10), remains uniform and linear from the upper to the lower end position.

[0021] Another device that also operates on the principle of gravity and the vertical movement of a weight is described in utility model HU 5111 U (SZIKRA TAMAS et al., Hungary), dated 28.01.2020. It is an ingenious solution in which the motor and gearbox are mounted directly on the storage weight, thereby increasing the total mass of the storage weight. However, the disadvantage of this system is that the rack and pinion are subjected to high surface loads both during operation and when stationary, meaning they are continuously under stress. Similar to the previously mentioned design, the rack in the middle position of the storage weight tends to bend, which overloads the linear bearing and increases friction losses. A reliable lubrication system is therefore required in this case as well. Ensuring the damage-free internal movement of the motor / generator's wiring also poses a challenge. In contrast, the design according to the present application avoids overloading or deformation of the structural components by distributing the mass of the rolling weight (4) across several appropriately sized rollers. Except in the version using sliding plates, no lubrication system is required. The electric motor / generator can be placed at the top of the device. Cooling and ventilation are ensured, and replacement or modification of type or size can be easily carried out. Alongside minimal maintenance needs, the system guarantees long-term, reliable operation. The mechanical energy storage device offers the following advantages:

[0022] • It can serve as a cost-effective alternative to battery-based energy storage systems.

[0023] • The use of rolling bearings ensures high mechanical efficiency.

[0024] • It is made almost entirely of environmentally friendly and recyclable materials.

[0025] • It can be installed outdoors.

[0026] • During operation, it produces no noise, light, chemical, particle, or any other form of environmental pollution.

[0027] • Its manufacture does not require any special technological solutions, and it can be produced in large series and in various performance ranges.

[0028] • Its structural design ensures a long service life.

[0029] • It requires minimal maintenance; only occasional condition checks are needed, which do not demand a high level of technical expertise or special instruments.

[0030] • Refurbishment can be easily carried out by replacing worn components, even on-site.

[0031] • The stored energy can be preserved indefinitely without any losses.

[0032] • As a stable column-like structure, the device can be painted to match its surroundings or used for informational or advertising purposes by applying inscriptions or images.

[0033] • Since it can be manufactured in various sizes and power capacities, it is suitable for supplementing small household power plants, storing temporary surplus output from smaller peak power plants, or reducing start-up time.

[0034] • Provided there is sufficient available space, multiple units can be operated in parallel mode, their number can be expanded at any time. Their activation or deactivation can be carried out in any sequence and timing.

Claims

Patent claimsMechanical energy storage equipmentA mechanical energy storage equipment which, supplemented by a dual-function electric machine, mechanically stores renewable green electrical energy and, when required, feeds it back into the grid using the same electric machine, consisting of characterised in that with its cylindrical design it serves both to accommodate the other components of the device and provides its static stability; its material may be carbon steel or, in the case of mass production, cast steel or cast iron; its height determines the potential energy storage capacity; it is further characterised in that a continuously rising, evenly inclined track section is formed on its inner surface, which is connected at the same inclination angle to the subsequent moving part.

1. three main parts:(a) The Base Body (1):(b) The Rolling Weight (4): characterised in that it performs a simultaneous rotary and vertical motion, rolling upward or downward along the evenly inclined track of the base body (1); depending on whether potential energy is being increased, meaning energy storage, or whether it rolls downward by its own weight, meaning energy release; on its outer surface there are built-in, bearing-mounted rollers (12) positioned at the same inclination angle as the inclined track section of the base body (1), which, by engaging with the base body (1), ensure uniform load distribution and create simultaneous upward-rotating or downward-rotating motion; the material of the rolling weight (4) may be carbon steel or, in the case of mass production, a combination of cast steel and cast iron; its robust structure allows it to accommodate the weight filling (9); further characterised in that its internal connecting element, the vertical guide plate (11).(c) The Rotor (5):• Being permanently connected to the vertical guide plate;« characterised in that it transmits energy input and output through its rotary motion to the electric machine via its connection to the drive shaft stub (10), which is supported by a base bearing (2) and a support bearing (7);• on the outer surface of its hollow shaft, bearing-mounted rollers (12) are installed, which, when the drive shaft stub (10) rotates, cause the rolling weight (4), connected to the vertical guide plates (11) that enclose the rollers (12) from both sides, to perform rotarymotion thereby forcing the rolling weight (4), depending on the direction of rotation, to move upward or downward while simultaneously rotating within the base body (1);• during which its bearing-mounted rollers (12) enter and exit between the guide plates (11) of the rolling weight (4);• the rotor (5) may be made of carbon steel or, in the case of mass production, cast steel.Wherein the three main units together, according to the current state of the art, are capable of:• moving the particularly heavy rolling weight (4) vertically with high mechanical efficiency by means of the low-inclination track section formed in the base body (1), utilising the torque that appears on the drive shaft stub (10) from the electric machine;• conversely, of converting the change in potential energy of the rolling weight (4), which moves downward and rotates under its own mass and the effect of gravity, through the drive shaft stub (10) into rotary motion on the shaft of the electric machine, thereby generating electrical energy with the resulting torque.

2. The rolling weight (4) and rotor (5) according to claim 1, characterised in that they may also be fitted with sliding plates and forced lubrication instead of bearing-mounted rollers.

3. The device according to claims 1 and 2, comprising the additional components of the brake (8), the damping spring (3) and the rubber block (6), characterised in that these components prevent damage to the device in the event of uncontrolled downward movement of the rolling weight (4).

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