Power plants – Combustion products used as motive fluid – Combined with regulation of power output feature
Reexamination Certificate
1999-11-30
2001-08-28
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combined with regulation of power output feature
C060S039550
Reexamination Certificate
active
06279312
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an energy generating installation comprising a gas turbine operated by steam injection, with a waste heat boiler being provided for steam production, which additionally supplies process steam to an external consumer.
Energy generating installations are known in the art, with a gas turbine being operated by additional steam injection, wherein the steam production takes place in a waste heat boiler heated by the exhaust gases of the steam turbine and a back-up firing equipment may be provided. This principle is consistently realized in the Cheng cycle where the overall steam flow can be fed into the gas turbine without a back-up firing equipment being required. Such an energy generating installation is described in the catalog “Cheng Cycle Series 7, Kraft-Wärme-Kopplung mit Gas Turbinen” [Cheng Cycle Series 7, Combined heat and power generation using gas turbines] of ELIN Energieversorgung Gesellschaft mbH. As compared with steam turbine installations, the Cheng cycle is characterized by lower investment costs involved, since moderate pressures and temperates prevail in the waste heat boiler and a condenser is not required.
Further, solar steam generators are known in the art, which use solar energy for steam generating purposes. Typical installations are parabolic trough collectors where paraboloidal type reflectors focus the solar energy onto a pipe carrying a heat transfer medium. One problem encountered when using solar steam generators is the unreliable availability of solar energy. It is therefore necessary that an additional fuel-firing equipment is provided. Due to the steam conditions achievable with solar energy, the fuel fired by such a back-up equipment can only be utilized with lower energy efficiency.
In the case of hybrid installations negative interactions between solar and conventional installation sections are normally inevitable (e. g. reduced efficiency when fossil fuel is fired, restricted operating range of the solar field). Solar steam injection into a gas turbine is not attractive for pure power generation since the steam flow which can be produced in the waste heat boiler satisfies or even exceeds the maximum operating flow of the turbine. The necessity of using a 100% fossil fuel-firing back-up equipment hitherto resulted in a solar installation which had not been optimally incoporated in an overall system designed for this purpose but “placed upon” a conventional installation. The additionally generated solar heat can be utilized in such systems only to a limited extent. This reduces the utilization ratio of the solar installation and the realizable fuel saving.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide an energy generating installation which is supplied with both fossil energy and solar energy and is capable of responding to the quantity of solar energy offered in order to be in a position to operate a gas turbine at high efficiency.
The energy generating installation of the invention generally operates according to the Cheng cycle principle offering all advantages achievable in this way. In addition to the evaporator which, together with the steam drum, forms a first circuit, a second circuit is connected to the steam drum said second circuit containing a solar steam generator. Here the moderate pressure and temperature conditions occurring in the first circuit of the Cheng cycle are utilized to directly couple a solar steam generator. The steam generated by the solar field is heated in the superheater of the heat exchanger and can be utilized as saturated steam in the gas turbine operated by steam injection either to increase the power generation or reduce the fuel consumption. Steam injection into the gas turbine requires only moderate pressures (approximately 20 bar). The resultant low saturation temperatures have a positive effect on the efficiency of the solar energy generator.
Special advantages are offered with regard to direct evaporation. The saturated steam production in the recirculation process allows stable operation of the solar steam generator without high demands being made on the control means even if the amount of solar radiation available is subject to variations. The solar steam generator may be configured as a parabolic trough collector in which the circulating water is directly evaporated. On the other hand it is also possible to heat a heat carrying medium, e. g. oil, with solar energy and transfer the heat energy absorbed via a heat exchanger to water. The temperature of the steam supplied by the solar steam generator should amount to approximately 200° C.
In the following an embodiment of the invention is explained in detail with reference to the single drawing.
REFERENCES:
patent: 5444972 (1995-08-01), Moore
patent: 5566542 (1996-10-01), Chen et al.
patent: 5623822 (1997-04-01), Schuetzendueble et al.
patent: 195 38 670 (1997-04-01), None
Casaregola Louis J.
Deutsches Zentrum fuer Luft -und Raumfahrt e.V.
Diller Ramik & Wight
LandOfFree
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