Thermal power plant with compressed air storage

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PATENT AUTHORITY (62) National application number (86) International filing date (86) Filing date for European patent application

Application received as:

(0 Swedish patent application □ completed international patent application with number (30) Priority information □ converted European patent application with number

76-03-15 CH 3165/76

KB 3-A4 according to SIS 61 30 13 allf · in a? aa (71) Applicant: BBC AG Brown Boveri & Cie, Baden CH (72) Inventor: G Gyarmathy, H Pfenninger, Zollikon, Baden (74) 0mbud: Grahn T (54) Title: Methods of operating thermal power plants with compressed air accumulators (56 ) Published publications:

US 3,597,621 (290-2), US 3,567

008 (60-59)

DD 99 415

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The present invention relates to a method of operating thermal power plants with compressed air accumulators, whereby compressed air is generated under low load utilizing electrical surplus energy and collected in an accumulator and then at peak load is recaptured from the accumulator to generate supplementary energy and after heating is supplied to the heat.

It is known to use compressed air accumulators at thermal power plants for peak loads. Nuclear power plants, for example, cannot be switched off overnight, whereby surplus energy is available during low load time, which energy is appropriately stored and utilized to cover load peaks. Since water is available at larger level differences, hydraulic accumulators with pumping stations are built, which has long been carried out. In flat terrain, such a facility can only be realized at great cost, insofar as this geological head is possible.

In other cases, a compressed air accumulator is the right solution. As is known, for example, by Brown Boveri Mitteilungen 62, 1975 p. 332-337, air is compressed during low load time and stored in an underground cavity. To cover load peaks during the day, the compressed air is supplied to the combustion chamber in a gas turbine plant and the thus stored energy is converted into electrical energy. Such plants require high quality fuel, with the fuel cost playing a major role. In Europe, fuel costs amount to about the same amount or even more than the total other operating costs for the power plant.

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A power plant is known in which the compressed heat of the compressed air is transferred to an underground heat accumulator before the air enters the compressed air accumulator. When extracting air from the accumulator, the air again flows through the heat accumulator, where it is heated and then a hot air turbine is supplied. This plant has the disadvantage that no intermediate cooling can take place in the compressor, since the heat is used to operate the turbine. Therefore, much energy must be consumed for the operation of the compressor. Furthermore, the production of an underground heat accumulator is associated with various difficulties.

The invention has for its object to provide an improved utilization of surplus energy in thermal power plants with compressed air accumulators.

This object is achieved by a method initially specified for the operation of such power plants, the method according to the invention being characterized in that:

a) a steam accumulator is heated with a steam vapor from the plant steam turbine during periods of low load;

b) a compressor for charging the compressed air accumulator is operated with the electrical energy of the steam turbine during periods of low load;

(c) the full power of the steam turbine develops under peak load; and

d) the compressed air stored in the compressed air accumulator is used under peak load to drive a hot air turbine, the compressed air first being heated by the stored heat potential from the steam accumulator.

By utilizing surplus energy during periods of low load, the entire power of the steam turbine can be utilized under peak load. In this case, the stored compressed air can also be utilized for operation of the hot air turbine, whereby the compressed air is heated by means of the stored heat potential from the exhaust steam from the turbine.

7702793-6 via the accumulator.

Steam as a heating means has the advantage that the temperature of the compressed air can be raised arbitrarily within technical limits, which leads to a sharp increase in the turbine power. In addition, intermediate cooling of the air during compression and post-cooling is possible, which reduces the required compressor power. When using a steam accumulator, this can be made considerably less than the known underground heat accumulator due to the good heat transfer.

The invention is described below in the form of exemplary embodiments and with reference to the accompanying drawings, in which unnecessary details are disclosed. In all figures, equal parts are provided with equal reference numerals.

Figure 1 shows a plant according to the invention. Figure 2 shows alternative heating of the compressed air from an electrically driven steam accumulator.

According to Figure 1, the air from the ambient of the multi-stage compressor 1 is sucked in and compressed to 60 bar, for example. Thereafter, the air in the aftercooler 2 is cooled to about. 30 ° C, after which it flows through the pressure line 3 to the accumulator 4. The shut-off valve 5 in the line 3 is open during this time.

To convert the energy stored in the compressed air to electrical energy, the valve 5 is closed and the shut-off valve 6 is opened in the conduit 7, which leads to the hot air turbine.

Eighth In the heat exchanger 9, which is connected in the supply line 7, the air is heated before it enters the turbine 8, where the air now serves as working gas. After the high pressure part of the hot air turbine 8, an additional heat exchanger 10 may be provided, in which the partially expanded compressed air is intermediately heated before expanding to ambient pressure in the low pressure part of the turbine 8.

Via the two disconnectable couplings 11, the unit 12 is connected partly to the hot air turbine 8 and partly to the compressor 1.

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During low load time, thus mainly at night, the coupling to the turbine 8 is switched off and the coupling to the compressor 1 is switched on. The unit 12 operates as a motor and drives the compressor, which transports compressed air to the accumulator 4. At peak load, the connection to the turbine 8 is switched on and the connection to the compressor 1 is switched off. The unit 12 then operates as a generator and delivers electrical energy to the grid.

The two heat exchangers 9 and 10 are heated with steam. Required steam is taken from a steam turbine plant, which essentially consists of the steam generator 13, the multi-stage turbine 14, the condenser 15 and the steam turbine generator 16. Under peak load, the steam at the point 17 is taken, which steam at the open valve 18 is supplied to the heat exchangers 9 and 10. During the night, the valve 18 is closed and the generator 16 in the steam turbine plant supplies its energy partly or completely to the unit 12.

This device has the advantage of being simple and therefore inexpensive. However, it has the disadvantage that just during peak load time, when the greatest power is required, steam is taken from the steam turbine plant, thereby reducing the generator power.

To avoid this reduction in power of the steam turbine plant, a valve 21 can be connected to the drain line 19 from the steam accumulator 20 after the accumulator in the flow direction. Instead of the steam accumulator, a hot water accumulator can be used, for example a Ruths accumulator. During low load time, the steam turbine plant not only drives the compressor 1 electrically over the assembly 12, but the accumulator 20 is further charged by the steam turbine. Under peak load, steam is then released from the accumulator 20 for the heat exchangers 9 and 10. In this way, during peak load time, not only the full power of the hot air turbine 8 but also the entire steam turbine power is available.

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A variant of the described plant consists in that the unit 12 has no connection with the compressor. The unit then serves only as a generator for the hot air turbine 8, and the compressor is driven, for example, directly by the steam turbine 14, from which it must then of course be disconnected.

Another possibility of steam generation for heating the compressed air is shown in Figure 2. From the circulation pump 22, water is transported from the container 23 to the hot water accumulator 24, where the water is evaporated by electric heating 25 and the heat exchangers 9 and 10. The condensed steam flows to the return line 26. the container 23.

Instead of a separate container 23, the cold condensate can also be supplied directly to the lower part of the hot water accumulator 24. It must be mentioned that the process heat generated, for example from the intermediate cooling of the compressor, can be used for preheating the water.

Of course, instead of the hot water accumulator, a steam accumulator can also be heated during the night by means of electrical energy, for example a steam accumulator according to figure 1. The night energy according to the system's basic load is in this case not only used for compressing the air, but also for charging the steam accumulator.

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