System for storing potential energy and method for producing such a system

Abstract

A system for storing potential energy includes a hydraulic cylinder, a mass to be lifted, and a sealing ring at the edge of the mass to be lifted. The mass to be lifted is a solid rock mass in the form of a cut-out solid rock. The hydraulic cylinder is formed by the cavity between surrounding rocks and the cut-out solid rock. The cavity is sealed with respect to the surrounding rocks by the sealing ring. A method for producing such a system is also provided.

Claims

1. A system for storing potential energy, comprising: a hydraulic cylinder; a solid rock piston disposed in the hydraulic cylinder to be lifted therein, the solid rock piston being cylindrically-shaped and having a height substantially equal to a height of the hydraulic cylinder, wherein a cavity is formed between the solid rock piston and the hydraulic cylinder and wherein the solid rock piston tilts in response to the piston being raised a distance that is more than one half of the height of the hydraulic cylinder; and a sealing ring at an edge of the solid rock piston, the cavity between hydraulic cylinder and the solid rock piston being sealed by the sealing ring, wherein the potential energy that is stored by the system corresponds to a product of a mass of the solid rock piston and a height thereof within the hydraulic cylinder.

2. The system for storing potential energy as claimed in claim 1, further comprising: one or more ballasts arranged on the upper side of the solid rock piston.

3. The system for storing potential energy as claimed in claim 1, wherein the sealing ring is arranged at a halfway working height (H/2) so that a rolling sealing ring is provided.

4. The system for storing potential energy as claimed in claim 1, wherein a distance that the solid rock piston is lifted in the hydraulic cylinder is less than one half of the height of the solid rock piston.

5. The system for storing potential energy as claimed in claim 1, wherein the hydraulic cylinder is formed in the earth.

6. A system for storing potential energy, comprising: a hydraulic cylinder; a solid rock piston disposed in the hydraulic cylinder to be lifted therein, the solid rock piston having a height corresponding to a height of the hydraulic cylinder, a diameter corresponding to a diameter of the hydraulic cylinder, and a mass corresponding to a volume of the solid rock piston, wherein a cavity is formed between the solid rock piston and the hydraulic cylinder; and a sealing ring at an edge of the solid rock piston, the cavity between hydraulic cylinder and the solid rock piston being sealed by the sealing ring, wherein the potential energy that is stored by the system corresponds to a product of the mass of the solid rock piston and a height thereof within the hydraulic cylinder, wherein the sealing ring has a cone which surrounds the circumference of the solid rock piston and in which a cylindrical articulated joint is inserted which supports a lamella plate which is provided with a sealing bead so that, through the pressure of a hydraulic fluid, the sealing bead is pressed against a surface of a wall of the hydraulic cylinder, with the result that a seal is obtained.

7. The system for storing potential energy as claimed in claim 6, wherein a dense flexible material is attached to the underneath of the lamella plate and closes positively with the sealing bead and the solid rock piston.

8. The system for storing potential energy as claimed in claim 6, further comprising: one or more ballasts arranged on the upper side of the solid rock piston.

9. The system for storing potential energy as claimed in claim 6, wherein the sealing ring is arranged at a halfway working height (H/2) so that a rolling sealing ring is provided.

10. The system for storing potential energy as claimed in claim 6, wherein a distance that the solid rock piston is lifted in the hydraulic cylinder is less than one half of the height of the solid rock piston.

11. The system for storing potential energy as claimed in claim 6, wherein the hydraulic cylinder is formed in the earth.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the system described herein will now be explained in further detail with reference to figures. In the figures:

(2) FIG. 1: shows an embodiment of a system for storing potential energy,

(3) FIG. 2: shows a first intermediate stage when implementing a method for constructing such a system,

(4) FIG. 3: shows a second intermediate stage when implementing a method for constructing such a system,

(5) FIG. 4: shows a detailed view of the procedure when sawing out from the rock the mass to be lifted, and

(6) FIG. 5: shows a detailed view of the construction of a sealing ring for such a system.

(7) The same component parts having identical designs are provided with the same reference numerals in all the figures unless mentioned otherwise.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

(8) An embodiment of the invention is illustrated in Drawing 1 and will be described in further detail below. In the case of the illustrated system for storing potential energy 10 a lifting piston 1 cut out from the solid rock and having the diameter d is guided in a cylinder 2, which was formed by cutting the lifting piston 1 out from the solid rock. A seal 1b is fitted halfway up the section h, thus at the height h/2, between the lifting piston 1 formed by the mass to be lifted which is cut from the rock, and the cylinder 2 which serves as the hydraulic cylinder. Water is supplied by a pump 8 from the reservoir 9 from below into the cylinder 2 at the point 4 via a pipe system 5 and 6. The surface area 3 is to represent the earth's surface. If the lifting piston is located in the raised position (lift height) D, then water can flow back at any time by way of the hydrostatic pressure via a turbine 7 into the reservoir 9 and thereby produce power in a generator 7b. Water tanks 11 may be provided on a top portion of the piston 1 to provide ballast that inhibits tilting of the piston 1.

(9) The amount of energy E which can be stored depends on the lift height D and the effective mass m of the cylinder 2 by way of the simple equation: E=g*D*m, in which g is the gravitational acceleration with 9.81 N/kg.

(10) In order to store large amounts of energy the mass m must be selected to be as large as possible. The lift height D cannot be selected at will since it has to be smaller than half the cylinder length h, since otherwise it may result in tilting of the lifting piston.

(11) The construction of the embodiment is undertaken by mining work which will be described below in brief with reference to FIGS. 2 to 4. Firstly, as shown in FIG. 2, a shaft 30 is sunk to a depth H below the earth's surface. From this shaft two galleries, namely a gallery 32 at depth H and a gallery 31 at depth H/2, are driven forward horizontally close up to the planned cylinder wall 2. From there circular tunnels 35 and 36 are driven into the mountain with a toroidal diameter corresponding to the diameter d of the subsequent lifting piston 2.

(12) If the shaft 30, as illustrated in FIG. 2, is sunk down further by a depth G then it can later serve as the pipeline section 6 or can house same.

(13) Several bores 41, as shown in FIG. 3, are sunk from the earth's surface 3 down to depth H with a relatively small radius. These bore holes 41 serve to introduce stone saws with which the cylinder wall is sawn out.

(14) FIG. 4 shows how a saw band 51c with saw teeth 51d is tensioned between an upper saw drive 51a, which stands on the earth's surface, and a lower saw drive 51b, which stands in the tunnel 35. The saw band 51c moves driven by the upper and/or lower saw drive 51a, 51b and is guided against the solid rock wall. The rocks are thereby chipped away and removed in the tunnel 35. The saw band 51c can additionally be cooled with water which is introduced at the top using the saw drive 51a. The two saw band drives 51a, 51b are guided on a circular arc which corresponds to the lifting piston 2. The circular shaped cut-out upper lifting piston 2 is thereby formed. This work can be carried out in parallel at all the bore holes 41.

(15) Parallel to this further saw bands are likewise guided through the bore holes 41 from the tunnel 35 to the tunnel 36 and are driven by saw band drives which stand in the tunnels 35 and 36. The lower part of the lifting cylinder is thus cleared. In the case of very tall cylinders further toroidal tunnels can be provided, so that the length of the saw bands does not exceed the technical possibilities.

(16) Parallel to these work operations horizontal bore holes are guided from the tunnel 36, the base tunnel, into the center of the cylinder 2. These holes are filled with explosives and the explosives are then detonated. The rocks in the region of the cylinder base which is hereby formed are thereby broken up and there is no longer any fixed mechanical connection between the cylinder base and the lifting piston.

(17) Parallel to this the tunnel sections 5 and 4 of FIG. 1 are driven forward in order to reach the bottom of the cylinder 2, via which the water can be supplied into the cylinder.

(18) When the sawing work has been completed, the sealing ring 33 is fixed on the lifting piston from the tunnel 35 in FIG. 2. After this the connecting galleries 31 and 32 are closed off in a watertight manner. Water can now be fed in via the pump 8 and thus energy can be stored.

(19) FIG. 5 shows a sealing ring 33 of preferred structure which can react to balance out irregularities in the wall of the cylinder 2. For this purpose a cylindrical articulated joint 53 is inserted in a cone 52 which surrounds the entire lifting piston 1, which articulated joint supports a lamella plate 54 which, as the result of the water pressure 58, presses with a sealing bead 55 against the surface 57 of the cylinder wall 2 and thereby seals the piston 1 from its surroundings. In order to improve the sealing action a dense flexible material 56 can be attached to the underneath of the sealing lamella plate, which material closes positively with the bead 55 and the piston 51. It should be noted that the lamella plate 54, owing to the long length, which can amount to several kilometers, shows a one-dimensional mechanical behavior.

(20) There now follows a sample calculation for the amount of energy which can be stored by a system having a radius of 500 m. With an assumed average density of the rocks of

(21) .sub.1=2500 kg/m.sup.3 and according to equation (2) an effective density of .sub.2=1500 kg/m.sup.3, the result from equation (6) is
E=9.81 N/kg*1500 kg/m.sup.3*2*3.14*(500 m).sup.4
or calculated as
E=5,775,637,500,000,000 joules.

(22) Converted into the more usual unit of kilowatt/hour, 1,604,343,750 kWh can be stored in the system. For comparison, the net power production of an average day in Germany amounted to 1,635,000,000 kWh in the year 2009, source BMWI http://bmwi.de/BMWi/Navigation/Energie/Statistik-und-Prognosen/energiedaten.html) (Federal Ministry of Economics and Technology enery statistics)

(23) It is apparent from the calculation that the amount of stored energy is very large in relation to all comparable reservoir power stations using hydropower. The intrusion into the environment is thereby relatively slight. Only water is pumped into the ground, the necessary intrusion into the land surface is slight and is restricted essentially to the surface area of the lifting piston. Said intrusion is readily visible through the lifting, however. A catastrophic breakdown of the system is difficult to conceive since for this the water would have to escape suddenly from the system, which is not possible as a result of the method of construction, such as compared with that of a dam.

(24) Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.