Energy storage devices with rotating mass made of high-strength homogeneous fibers or films

Abstract

Energy storage, comprehensive: a) a rotating mass made of high-strength homogeneous fibers or films, b) wherein the fibers or films are minimally bonded, c) wherein the flywheel is operated in a vacuum, d) wherein the motor-generator is designed in such a way that rotating magnetic fields are avoided except for charging and discharging.

Description

[0001] The "energy transition" encompasses the almost complete coverage of the electrical power supply by renewable energies (RE), primarily wind and photovoltaics (PV), while simultaneously expanding the use of electricity to include heating and transport (sector coupling). Due to the uneven availability of RE caused by weather and astronomy, with even brief periods of "dark lulls" occurring, the energy transition can only be implemented with the use of storage systems.

[0002] The present invention relates to an energy storage device that stores energy in the form of rotating masses (kinetic energy). In particular, the invention relates to flywheel storage devices whose rotating mass consists of high-strength homogeneous fibers or films, especially glass fibers.

[0003] In the context of the present invention, the term “homogeneous fibers or films” means that they are not composite fibers or composite films.

[0004] Flywheels have long been used as energy storage devices, for example in pottery wheels or combustion engines. Flywheel energy storage systems designed to store energy for periods longer than just a few seconds or minutes are typically mounted magnetically to minimize friction losses and operate in a (partial) vacuum. To achieve the highest possible strength, fiber composites are used in the rotating medium, allowing higher rotation speeds than, for example, solid steel flywheels—and thus more stored energy.

[0005] Given the same external dimensions, the energy content of the flywheel storage device is limited by the tensile strength of the material used. The amount of stored energy is proportional to the tensile strength. The storage duration is limited by losses. The largest share of losses arises from frictional losses of the flywheel against the surrounding gas mixture, since a perfect vacuum is never achievable. Further losses arise from magnetic fields that rotate with the storage medium and induce eddy currents in electrically conductive materials in their surroundings. If the rotating mass itself contains conductive materials, external magnetic fields induce such eddy currents in them.

[0006] A disadvantage of conventional flywheels is the use of composite materials, where strength is limited by the less rigid joining material. Furthermore, the use of plastics results in outgassing, which weakens the vacuum and reduces the system's efficiency.

[0007] The object of the present invention is to provide a flywheel energy storage device which: • can store larger amounts of energy, • enables longer storage periods, • inexpensive materials are used and • overcomes the disadvantages of the state of the art with regard to self-discharge and material strength.

[0008] To solve this problem, the invention proposes that the rotating mass of the flywheel be composed almost entirely of high-strength homogeneous fibers or foils. In particular, glass fibers are used to achieve maximum strength of the rotating body. This homogeneous fiber structure enables higher rotation speeds and thus a greater amount of stored energy.

[0009] Essential features of the invention are: • The rotating mass consists almost entirely of high-strength homogeneous fibers or films, preferably glass fibers. • The use of adhesive is minimized and only applied selectively to avoid air pockets. • The preferred main material is glass, which does not cause outgassing. • The motor generator avoids rotating magnetic fields and thus eddy current losses - except for charging or discharging. • When overloaded, the flywheel disintegrates into a fine sand-like mass, making a particularly stable housing unnecessary. • A vertical arrangement of the rotation axis supports operation without changing magnetic fields.

[0010] Instead of a composite material, as is known from the prior art, which consists of less rigid connecting material and reinforcing fibers, the energy-storing rotating mass is made almost entirely of strength-providing fibers and bonded only minimally – only to the extent necessary to support the weight and the additional forces generated by expected vibrations and the input and output of energy. Thus, for a given strength-determining (fiber) material, the maximum strength of the rotating body is achieved for maximum orbital speed and thus maximum energy content.

[0011] The plastics contained in conventional composite materials continuously release molecules into the surrounding vacuum, weakening the vacuum. The inventive design reduces this effect by using glass as the primary material (no outgassing), minimizing the use of plastic, and allowing the plastic to outgas directly from its surface, not after diffusion through thick plastic layers. This means that outgassing will decrease significantly after a limited time; this outgassing enables a stronger vacuum, thus reducing friction losses and increasing the achievable storage time.

[0012] To achieve the best possible degassing, the bonding points are arranged in such a way that air pockets are excluded. This is best achieved when the bonding points are so small that they only connect individual fibers at specific points.

[0013] The motor-generator is preferably designed to avoid rotating magnetic fields, except for charging and discharging. For example, the use of permanent magnets on the rotor is preferably avoided, thus eliminating the associated eddy current losses.

[0014] If the construction requires co-rotating electrical conductors in which ohmic losses can occur, it can be shielded against external magnetic fields (e.g. Earth's magnetic field).

[0015] The arrangement of the rotation axis and magnetic bearings is preferably chosen so that rotation does not result in changing magnetic fields (or such fields are minimized – at least the dynamic component of the magnetic bearing uses magnetic fields of varying strength by definition), and corresponding currents and losses are avoided or minimized. This can be supported by a vertical arrangement of the rotation axis. The part of the magnetic bearing that bears the entire weight of the flywheel and therefore has to generate the highest field strengths in the entire magnetic bearing system can be completely rotationally symmetrical and constructed of permanent magnets; the field strengths do not change at any point in the magnetic bearing due to rotation, so no leakage currents can arise.

[0016] Because the fibers are more or less loose due to minimal bonding, there are no flying fragments in the event of overload and breakage of the material, which would require a particularly sturdy housing to protect against. Instead, in the event of an overload, the fiber flywheel disintegrates into a harmless, fine sand-like mass. Disaster and especially earthquake protection:

[0017] To protect the system from extreme vibrations, all magnetic bearings can be equipped with an additional rolling bearing. This bearing does not touch any rotating part during normal operation of the magnetic bearings, but only when the rotor exceeds its specified mechanical tolerance range. To limit the forces under these conditions, the rolling bearings themselves can be mounted on strong springs, thus reducing the forces acting on the rolling bearings and the rotor during a given vibration.

[0018] Since the surrounding vacuum makes cooling difficult, a configuration is proposed that allows the stator of the motor-generator to be operated outside the vacuum while the rotor remains in the vacuum. This way, some of the waste heat is generated outside the vacuum, where it can be more easily dissipated. One possible configuration is to arrange a squirrel cage rotor at one or both ends of the shaft, while the stator is arranged around the squirrel cage rotor. The separation between vacuum and non-vacuum is possible, for example, by • Rotor and stator are separated by a part of the vacuum housing ( Fig. 6a) - this part of the vacuum housing must be magnetically neutral, or • that the stator itself is part of the vacuum housing ( Fig. 5, Fig. 6b).

[0019] In such an arrangement, the motor-generator can even be part of the magnetic bearings. For example, it can be controlled to generate appropriate counterforces in the event of positional deviations of the axle. It can also be activated for this purpose even when no electrical energy exchange is otherwise required.

[0020] In a preferred embodiment of the invention, the rotating mass of the energy storage device consists almost entirely of high-strength homogeneous glass fibers or glass foils.

[0021] In a further preferred embodiment of the invention, glass fibers are used whose tensile strength has been increased by treatment with AlCl3 (in a manner known to those skilled in the art) during the drawing process.

[0022] In further, likewise preferred embodiments, the rotating mass of the energy storage device consists almost entirely of high-strength homogeneous other materials, for example carbon fibers, aramid fibers, metal wires or high-strength nanomaterials.

[0023] The strength-providing material does not necessarily have to be in fiber form; films or tapes can also be used instead, e.g., ultra-thin glass films, which are commercially available in a minimum thickness of 25 µm, for example. The inventive principle of largely eliminating filler materials can also be implemented with films, and gas inclusions can be avoided just as with fiber material.

[0024] In a further preferred embodiment of the present invention, the rotating mass of the energy storage device consists entirely of a high-strength, homogeneous material in the form of a solid component, so that the energy storage device achieves its full strength without the need for fibers or foils. Here, too, the inventive principle of not weakening the strength-providing material by unnecessarily combining it with less strong material is adhered to.

[0025] In a further preferred embodiment of the present invention, instead of a motor generator that is more or less separate from the flywheel, the motor generator is incorporated into a hollow design of the flywheel axle.

[0026] If the rotating mass of the energy storage device is to consist almost entirely of high-strength homogeneous glass fibers, the energy storage device can be manufactured as follows: Preferably, the glass fibers are rolled onto the flywheel directly from the glass fiber drawing system, which offers the following advantages: • There is no need to unwind or roll up the glass fibers unnecessarily. • Instead of first sizing the freshly drawn glass fiber so that it can be stored and transported as a roving (bundle or strand of parallel arranged filaments), any necessary adhesion promoter can be applied immediately, which also means that there is no need to remove the sizing before bonding. • When drawing the glass fibers, the strength-enhancing gassing with AlCl3 can be done at the same time.

[0027] The adhesive can be applied in any manner familiar to the expert.

[0028] Before winding, the glass fibers are preferably guided over a rotating body coated with a very thin layer of adhesive, where they absorb exactly the required amount of adhesive.

[0029] It is also preferable to structure the adhesive application to the glass fibers in such a way that gas inclusions in the finished flywheel are avoided, e.g.: • structure the surface of the rotating body in such a way that the absorbed adhesive is in turn structured in such a way that gas inclusions in the finished flywheel are avoided (e.g. analogous to high or low pressure printing) • structure the adhesive application to the rotating body in such a way (e.g. analogous to offset printing) that gas inclusions in the finished flywheel are avoided.

[0030] According to the invention, the adhesive can also be applied using nozzles that, like inkjet printing, place tiny droplets of precisely selectable size from selectable directions onto each individual glass fiber to bond the fibers together at specific points. This can occur on the way from the drawing machine to the glass fiber reel, or alternatively, the adhesive droplets can be applied to the newly wound layer. Fig. 1 refers to such a point-by-point application of adhesive. In this example, the adhesive drops have approximately the same diameter as the glass fiber and are applied such that they are spaced approximately three fiber diameters apart in all three spatial directions. Depending on the intended use of the flywheel (e.g., charging / discharging within a few minutes or over several days), the bonding points can be placed closer or further apart. When using two-component adhesive, the frequency of cleaning the nozzles can be reduced by applying the two components separately to each bonding point. This ensures that the nozzles remain ready for use for a long time, even during production breaks.

[0031] All common products that are readily available and processable industrially can be considered as adhesives, including the resins commonly used in the production of glass fiber composite materials (e.g. epoxy, polyester, polyamide, silicone) or other adhesives such as cyanoacrylates.

[0032] A suitable size for the adhesive points is on the order of the volume of a sphere with the diameter of the fibers; a suitable spacing of the adhesive points from each other is approximately 2 to 4 fiber diameters, depending on the subsequent use as a long-term storage device (slow charging or discharging over weeks) or a short-term storage device designed to generate profit from short-term electricity price fluctuations (rapid charging or discharging within a few hours).

[0033] In a preferred embodiment of the present invention, the rotating mass of the energy storage device consists of discs from which the flywheel is assembled. Winding such a disc, whose profile follows a precise specification, is very difficult, if not impossible, simply by precise fiber guidance – even in combination with precisely positioned adhesive points. Therefore, according to the invention, it is preferable to attach a limiting disc to each side of the fiber coil, which is to be created in a profiled disc shape, for the winding process. The two discs then leave exactly a space with the desired profile, which is then "wound" with fibers. The fibers are coated with adhesive droplets in such a way that they are bonded to each other as intended, but no adhesive is applied to the profiling discs so that the profiling discs can be easily removed after the winding process. Alternatively, the profiling discs can also be provided - or additionally - with a coating to which the adhesive used does not adhere.

[0034] Despite all the care taken in manufacturing, there will always be small irregularities in the mass distribution. Therefore, the flywheels, or rather their individual discs, must be carefully centered on the axle. In principle, any method familiar to a person skilled in the art is suitable for this purpose. According to the invention, the use of piezoceramics is preferred, which can both signal imbalance and correct it by applying voltage. A centering method that consumes energy only during the centering process, such as an electromotive method with a worm gear / threaded rod, is also preferred.

[0035] Within the scope of the present invention, one of the disks composing the rotating body can be wound from very thin fibers, since experts generally assume that the thinner the fibers are drawn, the higher their strength relative to their cross-section. The smallest currently readily available fiber cross-section for glass fibers is 10 µm. However, their use can delay the production process, as winding very thin fibers is time-consuming. A preferred possibility according to the invention for producing more quickly is to produce only thin slices, but a corresponding number of them at the same time.

[0036] If the "thinner, stronger" rule does not always apply - contrary to the majority opinion among experts - production can be carried out with thicker fibers; the winding time saving effect increases with the square of the fiber diameter.

[0037] The advantages of the flywheel energy storage system according to the invention compared to conventional chemical batteries are: • Can be recharged as often as required without loss of capacity. • No toxic chemicals involved.

[0038] Compared to existing rotary storage systems, the subject matter of the present invention offers a significant cost advantage. It also achieves the following significant technical advances: • Reduced friction losses due to improved vacuum. • Greater strength through the use of high-strength homogeneous fibers.

[0039] All known rotational storage technologies that rely on the strength of fibers use composite materials, i.e. fibers completely embedded in plastic.

[0040] Such a state-of-the-art device is described on this website: https: / / www.ingenieur.de / technik / fachbereiche / energie / diesesschwungrad-speichert-windenergie / [created on November 2, 2016, accessed on November 8, 2024] (4 kWh, 45 cm cross-section, 45,000 rpm, carbon fiber compound). From this data, a surface speed of 1057 m / s is calculated; this corresponds to the surface speed achievable using E-glass, which is at least ten times cheaper, based on the arrangement according to the invention.

[0041] A preferred area of ​​application of the present invention is stationary energy storage for electrical energy supply, particularly in connection with energy generation from solar and wind power plants.

[0042] This could make it possible to eliminate non-renewable energy sources across Europe (and worldwide). Furthermore, the use of energy storage systems according to the invention provides the necessary storage capacity to bridge downtimes or periods of darkness (“dark lull”), which are currently insufficient. Over the course of the year, there are more than enough resources available from solar energy alone: ​​In Germany, solar radiation of 1000 kWh per m 2 and year. At a good 350,000 km 2 This results in a total irradiation of 350,000 TWh. To produce the current annual amount of electricity of approximately 700 TWh, one would have to cover approximately 1% of Germany's surface area with solar cells, i.e. 3,500 km², assuming a solar generator efficiency of 20%. 2 , which corresponds to about 1 / 5 of the traffic areas in Germany. The required area is therefore relatively small in comparison. Or to put it another way: There are approximately 20,000,000 single- and two-family homes in Germany. For simplicity, assuming a usable roof area of ​​100 m 2 per house, then that alone with 2000 km 2 more than half of the solar area required in this calculation. While these figures are neither exact nor fully applicable, they do give an idea that a complete electricity supply from renewable energy sources is easily achievable—at least in terms of the amount of harvestable energy and the required space. If we could store energy from summer to winter, we would already be set for life. Such storage is possible by means of the energy storage device according to the invention.

[0043] Energy storage in flywheels according to the invention can be applied both close to the power generation site (which evens out energy supply) and close to the consumer (which smooths consumption curves). Both of these applications drastically reduce the maximum required transmission capacities. Description of figures and reference symbols: Fig. Figure 1 shows a cross-section through a fiber coil (1) wound on an axle (2). The adhesive drops are not shown here. Fig. Figure 2 shows a greatly enlarged section of a fiber coil in which the fibers (21) are bonded together with small drops of adhesive (22). To improve visibility, the fibers are shown in an exaggeratedly drawn-out manner.

[0044] The adhesive droplets are spherical in the drawing to make the drawing easier to see. Of course, the applied adhesive droplets in the finished fiberglass wrap are not spherical, but rather cling to the fibers, bonding them together. In Fig. 2a to Fig. 2d, the adhesive droplets are arranged so that they have three times the fiber spacing in all three spatial directions. In Fig. 2e, the spacing is reduced so that they are twice the fiber spacing. The spacing of the adhesive droplets depends on the mechanical load the fiber coil is designed for (slow / fast charging and discharging, vibration resistance, etc.). Fig. 2c and Fig. 2e shows a section through the fibers.

[0045] Fig. 3 shows a cutaway vacuum housing with flywheel, without showing bearings or brackets etc.

[0046] Fig. Figure 4a shows a stack of flywheels, deliberately exaggerated so that the individual discs can be seen. Instead of being wound directly onto the axle, the individual discs can be wound onto sleeves, which are then attached to the axle. This allows the individual discs to be manufactured independently of one another, and it is also possible to center each disc individually on the axle.

[0047] Fig. 4b shows the cross-section through such a disc, the fiber winding (41) is shown hatched. Fig. Figure 4c shows the same disc in axial plan view. The axle and any sleeve are not shown.

[0048] Fig. Figure 5 shows a flywheel energy storage device with a motor-generator, cut in the center. In this case, the motor-generator is designed so that the rotor (52) rotates within a stator (51), which is part of the vacuum envelope.

[0049] In Fig. 6 is an excerpt from Fig. 5, which shows the motor-generator part enlarged. In this case, Fig. 6a shows the construction in which the vacuum housing (64) between the stator (61) and rotor (62) ensures the separation between vacuum (63) and non-vacuum, while in Fig. Figure 6b shows how the stator (61) itself has become part of the vacuum housing, thus reducing the distance between the stator (61) and the rotor (62). For clarity, the gaps are exaggeratedly wide. Fig. Finally, 6c represents a motor-generator completely located in the vacuum housing: QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] https: / / www.ingenieur.de / technik / fachbereiche / energie / diesesschwungrad-speichert-windenergie / [created on 02.11.2016, accessed on 8.11.2024

[0040]

Claims

[1] Energy storage, comprising: a) a rotating mass of high-strength homogeneous fibres or films, b) where the fibres or films are minimally bonded, c) wherein the flywheel is operated in a vacuum, d) the motor-generator being designed so that rotating magnetic fields are avoided except for charging or discharging. [2] Energy storage device according to claim 1, wherein the homogeneous fibers or films are selected from glass fibers, carbon fibers, aramid fibers, metal wires or high-strength nanomaterials, preferably glass fibers. [3] Energy storage device according to one of the preceding claims, wherein the vacuum is improved by the use of materials with minimal outgassing. [4] Energy storage device according to one of the preceding claims, wherein the fibers or films are bonded with an adhesive selected from epoxy, polyester, polyamide, silicone or cyanoacrylate. [5] Energy storage device according to one of the preceding claims, wherein the rotating mass of the energy storage device consists of discs from which the flywheel is assembled. [6] Energy storage device according to claim 5, wherein the discs are very thin and are wound from very thin fibers, in particular from glass fibers with a fiber cross-section of 5 to 50 µm, particularly preferably 10 µm. [7] Use of an energy storage device according to the characterization in one of claims 1 to 6 in stationary energy storage for electrical energy supply, in particular in connection with energy generation from solar and wind power plants.

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