The subject of the invention is sealing of the moving cylindrical surfaces in particular of pumped storage installation and gasket for such sealing.

Pumped storage installations are known with two reservoirs, lower and upper ones, in which electrical energy is converted into potential energy of water pumped from the lower reservoir to the upper one, and then, in the reverse process, potential energy is converted into kinetic energy of water released from the upper reservoir and finally it is converted to electrical energy by means of a water turbine and generator, however efficiency of this process reaches 80%.

The advantage of a typical pumped storage installation is simple design and the consequent reliability and longevity.

Significant drawback related to construction of such an installation is the necessity of locating it near to water reservoirs or one water reservoir adjacent to a hill allowing for the construction of an artificial reservoir on its top, wherein the difference between the altitudes of the water mirrors in both reservoirs should be substantial, usually exceeding 100m.

There are pressure tanks known in the technique, called hydrophores, where liquid pressure, usually water, is obtained due to effect of gas, usually air, present at the top of the tank or in a special rubber bag. Their main advantage is compact design allowing for miniaturization of the installation so that it can be widely used in detached buildings.

The principal limitation is the relatively low volume, limited by the strength of the tank walls to which the pressure is applied, which causes an exponential increase of the tank cost in a function of its volume, resulting from the need of thickening its walls with the increase of size. In addition, there are energy losses in the hydrophores resulting from the escape of the heat produced by heating of gas during compression, which may be prevented only with good thermal insulation of the whole tank, which again affects the cost increase.

Additional drawback are large differences of working pressures arising from the change of volume in the hydrophore part containing compressed air, with a change in the degree of its filling. Therefore, both the hydrophores and pressure towers, in which the altitudes difference is the source of hydrostatic pressure, as in the case of pumped storage installation, are not suitable to serve as a high capacity energy accumulator and only as constantly supplemented source of water under pressure.

An intermediate solution between hydrophore/pressure tower on the one hand and a typical pumped storage installation with two open reservoirs on the other hand, seems to be pressure vessel with gravity piston known in the technique, wherein the main source of hydrostatic pressure is the highly loaded moving piston, pushing water which fills cylindrical tank.

The main advantages of such an installation is, like in a typical pumped storage installation, relatively balanced pressure in all phases of filling the tank, wherein the differences between its extremities do not exceed more than a dozen percent of average values, while for hydrophores the difference is several hundred percent.

In contrast to the pressure tower or hydrophore, such a tank can have a considerable size and volume, which the pressure tower or hydrophore is not able to achieve because of unfavourable relation of construction cost to volume.

Up to now, an essential element limiting applicability of this type of installation as an energy accumulator is relatively large losses resulting from the friction between the gasket, which is a necessary element in this installation, and tank walls. The larger operating pressure of the installation, the tighter, larger and stiffer the gasket must be, which significantly affects the resistance of the piston movement.

The object of the invention is to develop the sealing and gasket for the moving cylindrical surfaces of, in particular, pumped storage installation, allowing for significant reduction of frictional force between the seal and the walls of the pressure tank.

Sealing of the moving cylindrical surfaces of, in particular, pumped storage installation, according to the invention is characterized by the fact that between the wall of the cylindrical tank and the piston wall there is a toroid shaped gasket made of flexible material filled with fluid, wherein the gasket is subject to flattening between cylindrical tank wall and the piston and together with the movement of the piston it rotates around its upper and lower axis, moving between the piston wall and cylindrical tank wall, wherein a pressure is applied on the bottom surface of the gasket by pressure of water present below the piston and pressurized by such piston. Preferably, the gasket, on external surface, has a tread in the form of longitudinal bulges that mesh with respectively shaped recesses made on the surface of the piston and cylindrical tank.

Preferably, the gasket is located so that in the lower position of the piston it is in the middle of the cylindrical tank.

A gasket for sealing moving cylindrical surfaces of, in particular, pumped storage installation, according to the invention is characterized by the fact that it has the shape of a toroid made of flexible material filled with liquid.

Preferably, the gasket consists of segments, which ends are tightly connected with each other so that the end of the segment of tapering cross- section is located inside the end of the next segment, wherein the combined ends are connected by means of bolts placed perpendicularly to the surface of the gasket.

Preferably, the gasket, on external surface, has a shaped tread in the form of longitudinal bulges.

The embodiment according to the invention provides stable movement of soil and ferroconcrete piston of a diameter of a kilometre and more, travel from several dozen to several hundred meters and weight from several dozen to several hundred million tonnes with relatively low resistance.

Construction of the gasket will allow for designing large-scale pumped storage installations near most large agglomerations, where there are no natural conditions for the construction of typical pumped storage installations requiring two open reservoirs with a significant vertical distance of one of them. Construction of pumped storage installations according to the invention can significantly improve the RES economics, especially where there is a large concentration of them, for example wind farms, however they can also be located at the bottom of the coastal ocean shelf. With this accumulator, RES will be able to work always with the greatest efficiency allowed by natural conditions and energy produced by them can be used when it is needed the most.

Accumulating the energy in the form of hydrostatic water pressure allows the change of design of wind turbines, which instead of generators can be equipped with much simpler and cheaper pumps of similar energy efficiency.

These and other characteristics of the invention will be clear from the following description of a preferential form of embodiment, given as a non- restrictive example, with reference to the attached drawings wherein:

Fig. 1 presents the piston surrounded by the gasket with visible cross- section, located inside the cylindrical tank when viewed in cross section; Fig. 2 presents magnification of cross-section of the gasket placed on the surface of the piston;

Fig. 3 presents a part of the cross-section of the gasket with visible tread of the gasket, piston and cylinder surface;

Fig. 4 presents a cross-section of the gasket, piston and cylinder in larger scale;

Fig. 5 presents a single segment of the gasket 6 and two connected segments;

Fig. 6 presents a cross-section of the surface of two segments of the gasket bolted together;

As shown in the figure, between the wall of the cylindrical tank 1 and the wall of the piston 2 in the pumped storage installation, there is a gasket 3 provided of toroid shape made of flexible material, such as rubber reinforced with steel or Kevlar links of similar design to those used in automotive tires, whose interior is filled with water. The gasket 3 is subject to flattening between walls of the cylindrical tank 1 and piston 2 and with the movement of the piston 2 it rotates around its upper and lower axis moving between the wall of the piston 2 and the cylindrical tank 1, wherein the bottom surface of the gasket is subject to water pressure present below the piston, and compressed by this piston.

In order to increase the traction of the gasket 3 to the wall of the piston 2 and pressure tank 1 , and to prevent its uneven rotation during movement of the piston 2, the gasket 3, on external surface, has a tread in the form of longitudinal bulges 4 of trapezoidal cross-section that mesh with respectively shaped recesses 5 made on the surface of the piston 2 and the cylindrical tank 1. In the lower position of the piston 2, the gasket 3 is located in the middle of the height of the cylindrical tank 1.

The gasket 3 consists of segments 6, which ends 6a, 6b are tightly connected with each other so that the end of the segment of tapering cross- section is located inside the end of the next segment and is pressed, thus sealed, against the walls of the next segment, wherein the combined ends 6a, 6b are connected with bolts 7 located perpendicularly to the surface of the gasket 3, pressing the ends of both gasket fragments to each other, precluding their mutual displacement.

Water by pressing on the flexible lower surface of the gasket 3 compresses the operating fluid inside it, for example water, which in turn evenly presses the gasket 3 to the wall of the cylindrical tank 1 on the one hand and the moving piston 2 on the other, ensuring their tightness. The gasket 3 is filled with water at an ambient pressure and compression of the liquid (water) filling it is ensured by the above described process. During the movement of the piston 2 and rotation of toroidal surface of the gasket 3 induced by it, its internal side is reduced and compressed, and the external side is expanded and extended. This is possible because the material which the seal is made of and its reinforcements are modelled on those used in automotive tires, yet appropriately thicker, directly proportional to the increased size and higher working pressure. These deformations necessitate a very large difference between the diameter of the piston 2 and the thickness of the clearance between the piston 2 and cylindrical tank 1 in which the gasket 3 moves so that the difference in length between the outer and inner part of the gasket and the resulting tension is kept to a minimum. In large-scale installations the relation of size between the diameter of the piston 2 and the thickness of the clearance in which the gasket moves should be in the range between 1 :500 and 1 : 1000.

In the lower position of the piston 2, with complete emptying of the cylindrical tank 1 of water located under it, the pressure vanishes and the gasket is located in the middle of the cylindrical tank 1 height. At this position, it is possible to replace its segments or the whole gasket.