Compressed-Air Storage Installation

Abstract

A compressed-air storage installation comprising a heat accumulator for storing heat contained in compressed air and the air is passed into subterranean caverns. The heat accumulator has partitions therein which are provided between a storage medium. The partitions form a number of air passages through which the hot compressed air entering at the central region of the heat accumulator flows in an essentially outward direction, thereby cools and flows on into the cavern. The present invention relates to a new and improved construction of a compressed-air storage installation having a heat accumulator for storing heat contained in compressed air, with the compressed air being passed into subterranean caverns. It is already known to employ compressed air instead of liquids as a storage medium for storing energy. The state-of-the-art compressed-air storage installations store compressed air at times of low load and utilize it at times of peak load to generate additional peak load energy. With these known installations, in order to increase the stored energy while the air is expanding, the air is heated by combustion of liquid or gaseous fuels before entering an expansion turbine. Compared with hydraulic pump storage stations, this technique has the disadvantage that additional energy in the form of a fuel is required for the storage of energy. It has also been proposed not cooling the air during the compression process, in order to thereby obtain as high as possible compressor discharge temperature, and that the compressed air then should be passed into a heat accumulator which removes heat from the air. After the heat is removed, the cold air then can be stored in a compressed-air store. Before the air expands in the gas turbine it is heated in the same heat accumulator in the reverse flow direction. Since the air usually has a pressure of 30 to 60 bar in these known installations, the outlay for storage above ground is too great and too expensive. It is for this reason that there are presently used subterranean caverns for storing air. Upon leaving the compressor the air which is to be stored has a temperature of about 300.degree. C to 500.degree. C. The rock strata forming the cavern will not withstand such temperatures, and even a lining of rock of relatively high heat resistance would be costly to maintain, especially since additional temperature fluctuations occur in the heat accumulator during such time as the storage cavern is being charged and discharged. Therefore, with the foregoing in mind it is a primary object of the present invention to provide an improved compressed-air storage installation which is not associated with the aforementioned drawbacks and limitations of the prior art proposals. Another and more specific object of the present invention aims at creating a compressed-air storage installation with heat accumulator which is operated without additional fuel and which is simple and cheap to construct and arranged such that no high temperatures and temperature fluctuations occur in the rock wall. Now in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the compressed-air storage installation of the present development is manifested by the features that partitions are provided within the heat accumulator between a storage medium, in particular stones. These partitions or partition members form a number of air passages through which the hot compressed air entering at the center or central region of the heat accumulator flows in an essentially outward direction, thereby cools and flows on into the cavern. One important advantage of the present invention resides in the fact that the partition walls or parititions between the storage medium, in particular between stones, are so arranged that the incoming air is forced to flow through the storage medium in an outward direction and gives up its heat to the medium. According to another advantageous construction of the invention, the air passages are arranged in such a manner that a rock wall serves as the outer bounding surface of the last passage. The consequence of this arrangement is that the air flowing around the partition walls or partitions has given up the heat contained in it to the storage medium by the time it reaches the rock wall, and hence the rock wall remains relatively cool, i.e., attains a maximum temperature of 40.degree. C to 80.degree. C. Due to these measures, there is avoided crumbling of the rock wall due to the thermal effects, and thus, there is ensured that the underground chamber of the heat accumulator retains its freedom from leaks, in other words remains leak-tight. Furthermore, it is advantageous if the partition walls are formed of sheet metal and are thermally insulated at places having large temperature gradients or differences between the individual air passages. It has proved to be of special benefit if the aforementioned partition walls are provided with thermal insulation at places with large temperature differences, in particular at the hot air inlet into the heat accumulator and also opposite the outlet from the heat accumulator to the cavern. According to another construction of the invention there are provided artificially calcined and hardened stones as the storage medium. Through the use of artificially calcined and hardened stones as a storage medium it is possible to fill the interior of the heat accumulator with uniform interstices allowing the passage of air, because the artificially calcined and hardened stones can be shaped according to requirements. It has been found to be especially beneficial if in the heat accumulator of the invention the minimum ratio of the accumulator length to the accumulator diameter is about 2:1. It is furthermore advantageous if there is provided between an air inlet pipe and the rock wall surrounding the same a gap in which, by means of natural air circulation, the heat passing through the thermal insulation can be removed to the outside. This avoids heating of the rock outside the central, hot air inlet pipe, and the occurrence of thermal stresses in the rock.

Patent Drawings (1 sheets)

Sheet 1