Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
2002-01-28
2003-10-28
Gartenberg, Ehud (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
C137S613000, C060S039440, C060S787000
Reexamination Certificate
active
06637207
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a gas-storage power plant having the features of the preamble of claim 1. The invention also relates to a method of throttling a storage pressure to a working pressure for a turbogroup of such a gas-storage power plant.
BACKGROUND OF THE INVENTION
Such a gas-storage power plant is normally interconnected in a “Compressed-Air-Energy-Storage System”, in short a CAES system. The basic idea of a CAES system is seen in the fact that excess energy which is generated by permanently operated conventional power generating plants during the base-load times is transferred to the peak-load times by bringing gas-storage power plants onto load in order to thereby use up less resources overall for producing electrical energy. This is achieved by air or another gas being pumped under a relatively high pressure into a reservoir by means of the inexpensive excess energy, from which reservoir the air or gas can be extracted when required for generating relatively expensive current. This means that the energy is stored in a retrievable manner in the form of potential energy. Worked-out coal or salt mines, for example, serve as reservoirs. Since the gas stored in the gas reservoir is normally air, such a gasstorage power plant is generally also designated as an air-storage power plant.
Gas-storage power plants of this type are known, for example, from the report “CAES REDUCED TO PRACTICE” by John Daly, R. M. Loughlin from Dresser-Rand, Mario DeCorso, David Moen from Power Tech Associates Inc., and Lee Davis from Alabama Electric Cooperative Inc., which has been presented at the “ASME TURBO EXPO 2001”. Accordingly, a gas-storage power plant normally comprises a gas reservoir, in which a gas can be stored under pressure, and a turbogroup which has at least one turbine. A gas-supply line connects the gas reservoir to the turbogroup, so that the turbine of the turbogroup can be driven with the gas from the gas reservoir. Arranged in the gas-supply line is a control valve arrangement which throttles a storage pressure applied on the inlet side to a working pressure required by the turbogroup. The control valve arrangement normally comprises a control valve, the throttling effect of which can be controlled in an open-loop and/or closed-loop system, and a stop valve which is connected upstream of the control valve and can be switched over between an open position for normal operation and an emergency-trip position.
In this case, the control valve must be actuated in such a way that the required working pressure is always provided on the outlet side. However, this working pressure is variable and depends on the current operating state, or on an operating state to be set, of the turbogroup. In addition, the storage pressure applied on the inlet side may also vary within a relatively large range, since the gas reservoir empties during operation of the turbogroup, a factor which is accompanied by a decrease in the storage pressure. For example, the storage pressure varies within a large range over the course of the operating week by virtue of the fact that the storage pressure is highest at the start of the week and, after daily decrease and partial refilling of the storage cavern at night during the working week, the storage pressure toward the end of the working week is finally at the lowest level. The storage pressure rises again to the level at the start of the week by filling the storage cavern during the weekend. Accordingly, the control range, for example, over the course of a week is very large and the outlay in terms of open-loop or closed-loop control at the control valve for the provision of the currently desired working pressure is relatively high. However, increased outlay in terms of closed-loop or open-loop control at the control valve may be at the expense of the reliability and thus of the operating safety of the control valve arrangement. Furthermore, in particular during start-up and during the loading of the turbogroup, very high pressure differences may be present between the storage pressure applied at the inlet side of the control valve and the working pressure to be provided on the outlet side, for example if the gas reservoir is still filled to the maximum level and the turbogroup only requires a minimum working pressure. Accordingly, the control valve must realize extremely pronounced throttling effects. In the process, vibrations and oscillation excitations, in particular in combination with noise emissions, may occur in the control valve, as a result of which the control valve is highly loaded. High loads may lead to material fatigue and to failure. A control valve which fails during start-up of the turbines may lead to damage or destruction of the turbines.
SUMMARY OF THE INVENTION
The invention is intended to provide a remedy here. The object of the present invention is to show a gas-storage power plant of the type mentioned at the beginning which ensures relatively high reliability and operating safety for the valve arrangement.
This problem is solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.
The present invention is based on the general idea of designing the throttling of the storage pressure to the working pressure in at least two stages. This measure leads to considerably smaller pressure differences in the individual throttling stages. Accordingly, the loading on the throttling points is reduced. Furthermore, the invention provides considerable simplification of the closed-loop or open-loop control of the individual throttling points by the first throttling stage being controlled in a closed-loop or open-loop system according to the changes in the storage pressure, whereas the last throttling stage is controlled in a closed-loop system according to the changes in the working pressure or the intermediate pressure. Both the reduction in the outlay for the closed-loop or open-loop control of the throttling points and the reduction in the pressure difference occurring at the individual throttling points result in an increase in the reliability and the operating safety of the valve arrangement.
In a preferred embodiment of the invention, the valve arrangement has two throttling stages. There, the first throttling stage is designed as a first control valve, this control valve in particular having the function of an emergency-trip or stop valve and a control function.
The first throttling stage serves to reduce the storage pressure applied on the inlet side to an intermediate pressure. The result of this measure is that the aforesaid intermediate pressure is admitted on the inlet side to the second throttling point, a second control valve, as a result of which the throttling to the working pressure is considerably simplified.
The valve arrangement may of course have any desired number of throttling stages, by means of which throttling is effected to several intermediate pressures and, by the last stage, to the working pressure.
In a further preferred embodiment of the invention, the control valves each have an actuator, these actuators being connected to a control device which is interconnected in a feedback control circuit or a plurality of feedback control circuits. A feedback control circuit for the first control valve directs values of the storage pressure and/or of the intermediate pressure to the control device. A feedback control circuit for a further control valve or the last control valve directs values of the intermediate pressure and/or of operating variables of the turbogroup to the control device.
In a further embodiment, a control valve or a plurality of control valves are designed as relieved single-seat valves. All the control valves are preferably designed as relieved single-seat valves, which permits a cost reduction. A relieved single-seat valve has the advantage that it requires small actuating forces and thus small drives. Small drives also have short actuating times. (Such short actuating times ensure that the overspeed of the air t
Konezciny Stephan
Suter Franz
Alstom (Switzerland Ltd
Gartenberg Ehud
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