WO2009063468A2

WO2009063468A2 - An electric power generating method and system

Info

Publication number: WO2009063468A2
Application number: PCT/IL2008/001500
Authority: WO
Inventors: Yossi Ram
Original assignee: C.Cogen
Priority date: 2007-11-15
Filing date: 2008-11-13
Publication date: 2009-05-22
Also published as: EP2222943A2; WO2009063468A3; IL187398A0

Abstract

The subject invention provides a system for electric power generation, a method for generating electric power from natural gas, and a gas-operated power station.

Description

An Electric Power Generating Method and System

FIELD OF THE INVENTION

The invention is generally in the field of power generation and more specifically of electric power generation from natural gas.

BACKGROUND OF THE INVENTION

Natural gas is the most common type of hydrocarbon that is in a gaseous state at common environmental temperatures. Natural gas is well recognized as a low cost, easily-handled and clean burning fuel, as it is often priced below liquid oil, it can be distributed to households and businesses by pipeline, and it creates little emissions other than carbon dioxide.

The need for transportation and storage of gas has increased as gas resources have been established around the globe. To this date, only a few methods have proved viable in transporting and storing gas in large quantities.

One transportation method is to build a pipeline feeding the gas directly to a desired location. A typical storage method is to build large pressure vessels or storage tanks to store the gas at ambient conditions or at a slightly pressurized condition. As an alternative to large pressure vessels pipeline loops have also been constructed to store a quantity of gas at pipeline conditions. However, using pipes for the transportation of gas is expensive and at times impossible due to geographical and/or political constrains.

Another method for storing the natural gas included condensing the gas to a Liquid Natural Gas (LNG) thereby substantially reducing its volume for ease of transport and storage. LNG involves liquefaction of the natural gas and normally includes transportation and storage of the natural gas in the liquid phase. Some drawbacks of using LNG are known: in order to liquefy natural gas, it must be cooled to approximately -26O⁰F., at atmospheric pressure; LNG tends to warm during long term storage and transport and therefore will not stay at that low temperature so as to remain in the liquefied state. Cryogenic methods must be used in order to keep the LNG at the proper temperature during transport. In addition, the LNG must be re-gasified at its destination before it can be used.

In using Compressed Natural Gas (CNG) for storage and transportation, much of the technical problems of ambient condition storage and transportation and the costs and temperatures of LNG, are avoided.

The present invention provides methods and systems for generating power from natural gas in small-to-medium size power-generating stations in remote areas, thereby avoiding the high costs of transportation and storage of known methods.

SUMMARY OF THE INVENTION

In accordance with the invention small to medium size natural gas-operated power stations are provided and fed with compressed natural gas (CNG) by a fleet of suitable transport vehicles.

The present invention provides, according to one of its aspects, a method for generating electric power from natural gas. The method comprises: providing one or more small-to-medium size power-generating stations, each of which comprises one or more natural gas-operated electric power-generating unit, optionally, a natural gas storage sub-system and at least one natural gas feeding port; providing a fleet of one or more CNG transport vehicles for collecting compressed natural gas at a natural gas dispensing station and for transporting it to the power generating stations; the fleet transporting the natural gas to said power-generating stations and feeding the natural gas into the at least one feeding port; and feeding said gas to said electric power- generating unit and operating the unit to generate electric power.

The present invention provides, according to another of its aspects, a system for electric power generation, comprising: one or more small-to-medium size power- generating stations, each of which comprises one or more natural gas-operated electric power-generating unit, optionally a natural gas storage arrangement and at least one natural gas feeding port; and a fleet of one or more compressed gas transport vehicles for collecting natural gas at a natural gas dispensing station, transporting the natural gas to said power-generating stations and for feeding the natural gas into said feeding port. According to one, non-limiting embodiment, the transport vehicles comprise one or more composite reinforced transport modules. Examples of such modules are those disclosed in US patent 6,779,565, the content of which is incorporated herein by reference. However, the invention is not limited to this embodiment and any other transport module that is suitable for the transport of compressed natural gas (CNG).

The power-generating station, according to one embodiment comprises two or more gas feeding ports for connecting to corresponding two or more CNG transport modules. A switching arrangement is then provided to selectively connect one or more feeding ports to the power generating unit at one time and one or more others at another time. In accordance with this embodiment natural gas may be fed directly from one or more transport module to the power generating unit. Upon exhaustion of the gas in said one or more transport modules the corresponding feeding ports may be switched off and at the same time one or more other feeding ports that are hooked up to one or more other transport modules are switched on to permit feeding of gas therefrom to the power generating unit.

In accordance with another embodiment, one or more of the power generating units have a CNG storage sub-system comprising one or more storage tanks which may composite reinforced tanks or others. The CNG storage sub-system is connectible to the one or more feeding ports to permit feeding gas thereinto and is also connectible to the power generating unit for feeding gas to it. The gas storage sub-system then serves as a buffer to permit gas feed to the power generating unit also at times when no CNG transport module is hooked to a feeding port. A switching arrangement then permits selection between different gas-feeding operational states as discussed below.

In one gas-feeding operational state, the natural gas is fed directly from the transport module through said port to the power-generating unit. In another gas-feeding state, gas is fed to the power generating unit by the gas storage sub-system. In a further gas-feeding state gas is fed from said transport module to said storage sub-system and to said power generating unit. Typically, although not exclusively, a power generating station with a gas storage sub-system has three gas-feeding operational state, in a first of which gas is fed jointly into the storage sub-system and directly to the power generating unit until yielding pressure equilibrium between the transport module and the tanks of storage sub-system, then the switching arrangement seals the tanks to permit gas feed to the power generating unit directly from the CNG transport module, and upon exhaustion of gas from the transport module the switching arrangements switches for gas feed from the tanks of the storage sub-system until attachment of another CNG transport module to a port.

The system and method of the invention are particularly, although not exclusively, suitable for small-to-medium power generation capacity. A small-to- medium power generating station is typically one that generates power for a specific use, location or installation. Exemplary, non-limiting power generation stations with small-to medium power generating capacity are power generating stations intended for use in generating electricity for greenhouses, dairy farms or other agricultural installations, airports, plants, factories, hotels, office buildings, transport terminals, schools, universities, recreation centers, domestic use is small remote communities, etc. Examples are power generating stations with a power generating capacity of less than 50 megawatts (MW), at times less than 40 MW or less than 30 MW, often less than 20 MW₅ 10 MW and at times even less than 5 MW.

A small-to-medium power generating station is particularly useful for generating power at periods of peak or medium demand for electric power.

The power generating station may also includes, according to some embodiments, a cooling or heating sub-system for cooling or heating the switching arrangements, cooling or heating the gas flowing from the storage to power generating unit or the gas tubing. In some cases for example the gas tubing may heat up during gas passage therethrough, thereby cooling said gas tubing may be needed. In another example, the cooling sub-system may at times also be made to cool the port as it may also heat up during feeding of gas thereinto.

Power generating stations, useful in accordance with the invention, are often adapted for co-generation of electricity and heat. This permits to increase the yield of energy utilization. The co-generated heat that is collected can then be used directly for a variety of purposes such as heating buildings and installations, use in industry that uses heat in the manufacturing process such as the ceramic or brick industry, generation of steam, operating hot-cold engines, etc. In such a co-generation power station the electric power-generating unit is associated with a heat absorption sub-system. This sub-system is then associated with a heat transport system for transporting the heat to one or more users. According to another aspect of the invention there is provided a gas-operated power station comprising: a natural gas-operated power-generating unit; a gas feeding port for hooking up to a compressed natural gas (CNG) transport module; a gas storage sub-system; a gas piping system permitting gas flow (i) from the feeding port to the gas storage sub-system, (ii) from the feeding port to the power generating unit and (iii) from the storage sub-system to the power-generating unit; and a switching arrangement to permit different gas flow patterns at different gas feeding operational states.

A gas-operated power station according this aspect has typically three gas- feeding operational states, comprising: (i) a first gas-feeding state in which gas is fed from said transport module to said storage sub-system and to said power generating unit, (ii) a second gas-feeding state in which gas is fed from said transport module to said power-generating unit while the storage sub-system is sealed, and (iii) a third gas- feeding state in which gas is fed from the storage sub-system to said power-generating unit.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 is a general, schematic depiction of the system in accordance with an embodiment of the invention.

Fig. 2A shows a schematic depiction of a power generating station of an embodiment of the invention with a storage sub-system.

Figs. 2B-2D show the station of Fig. 2 A is three gas-feeding operational states.

Fig. 3 shows a power generating station of an embodiment of the invention with two gas feeding ports.

Fig. 4 is a schematic flow-chart of a method in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference is first made to Fig. I₅ showing a schematic depiction of a system in accordance with an embodiment of the invention. The system generally designated 100 includes a fleet 102 with a plurality of vehicles 102-1, 102-2, ... , 102-N. Each of these vehicles carries a CNG transport module 104 adapted for holding highly compressed natural gas, typically at a pressure above about 250 Atm. The system also comprises a plurality of electricity-generating stations 106-1, 106-2, ... , 106-P. The transport modules 104 of vehicles 102-1, 102-2, ... , 102-N can hook to a natural gas-dispensing stations 108 for filling gas thereinto, which may in turn be fed gas by a gas piping system 110. The gas piping system may transport gas directly from a natural gas pumping site, from a docking station of gas-transporting ships, from gas storages, etc.

Each of the power generating stations 106-1, 106-2, ... , 106-P comprises one or more feeding port 112, an optional gas storage sub-system 114 with one or more tanks 116, a power generating unit 118 comprising a turbine 120 and inked to a generator 122, for generating electric power that may then be transported to users. According to some embodiments of the invention, the power generating station is of the co-generation type and includes a system to absorb heat 124 that is produced by unit 118 and which can this be transported through an appropriate transport system directly to users. A piping system 126 connects the feeding port, the tank and the turbine to permit gas feed in a manner such as that which is described below with reference to Figs. 2B-2D.

The vehicles 102-1, 102-2, ... , 102-N of fleet 102 then transport the CNG transport modules, filled with highly compressed gas, from the natural gas-dispensing stations 108 to stations 106-1, 106-2, ... , 106-P, where the gas may be fed through feeding ports 112 to the power generating unit 118. The compressed gas storage tanks 116 are typically reinforced by a composite material, for example, as described in US patent No. 6,779,565.

Reference is now made to Fig. 2A, showing a schematic depiction of a power generating station 106 according to an embodiment of the invention. In this Fig. like elements to those of Fig. 1 were given like reference numerals. Three gas flow-control switches are provided: a first 130, controlling flow of gas from the port 112 to tank 116; a second 132, controlling flow of gas between port 112 to power-generating unit 118; and a third 134 for controlling flow from tank 116 and power-generating unit 118.

Reference is now made to Figs. 2B-2D showing three gas feeding states. For ease of description, shown in Figs. 2A-2D are only those switches that are at an "OFF" or sealed state, namely blocking flow of gas thereto. In a first gas feeding state shown in Fig. 2B, all switches are in an open state and thus gas can flow from port 112 both to tank 116 and to unit 118. AU switches may be kept open until pressure equilibrium between CNG transport module 104 and tank 116 is achieved, whereupon switch 130 and 134 are switched to an OFF state thus sealing tank 116, as shown in Fig. 2C. In this state gas flows directly from the CNG transport module 104 power generating unit 118. Once the gas in the transport module has been exhausted, switch 132 may then be sealed and switch 134 opened to yield a state as shown in Fig. 2D₅ in which gas to power generating unit 118 is fed from tank 116.

Reference is now being made to Fig. 3 showing a power generating system according to an embodiment of the invention. In this figure like elements to those of Fig. 2A were given like reference numerals shifted by 100. The reader is referred to the relevant description in Fig. 2 A or in Fig. 1 for explanation of their function. The power generating station according to this embodiment has two feeding ports 212A and 212B for hooking up to respective CNG transport modules 104A and 104B. A switching arrangement 240 is provided for switching from one port to another upon exhaustion of the gas in the transport module hooked thereto.

The method according to an embodiment of the invention is depicted in a schematic flow chart shown in Fig. 4. At a first step 400 vehicles with a CNG trasport module arrives at a natural gas dispensing station and highly compressed natural gas is then fed into the tanks of the gas transport modules.

At a next step 402 the vehicles transport the natural gas to the power stations and there the transport module is hooked to the feeding port and then at 404 the natural gas is fed to the turbine of the power generating unit. The natural gas then operates the turbine to generate at 408 electric power and optionally, at 410 with co-generation of heat.

Claims

CLAIMS:

1. A method for generating electric power from natural gas, the method comprising:

(a) providing one or more small-to-medium size power-generating stations, each of which comprises one or more natural gas-operated electric power-generating unit and at least one natural gas feeding port;

(b) providing a fleet of one or more compressed gas transport vehicles with a compressed gas transport module for (i) collecting compressed natural gas at a natural gas dispensing station and (ii) transporting it to the power-generating stations;

(c) the fleet transporting the natural gas to said power-generating stations;

(d) connecting a transport modules to the at least one feeding port for feeding the natural gas to the station; and

(e) feeding said gas to said power-generating unit and operating the unit to generate electric power.

2. A method according to Claim 1 , wherein one or more of said stations have a gas-feeding operational state in which natural gas is fed directly from the transport module through said port to the power-generating unit and.

3. A method according to Claim 1 or 2, wherein one or more stations comprise a natural gas storage sub-system connectible to said feeding port and to said power- generating unit for feeding gas thereinto and for supplying gas to said unit, respectively.

4. A method according to Claim 3, wherein one or more stations have three gas- feeding operational states, comprising (i) a first gas-feeding state in which gas is fed from said transport module to said storage sub-system and to said power generating unit, (ii) a second gas-feeding state in which gas is fed from said transport module to said power-generating unit while the storage sub-system is sealed, and (iii) a third gas- feeding state in which gas is fed from the storage sub-system to said power-generating unit.

5. A method according to any one of the preceding claims, wherein said power generating stations have a power generating capacity of less than 50 MW.

6. A method according to Claim 5, wherein the power generating capacity is less than 20MW.

7. A method according to Claim 6, wherein the power generating capacity is less than 10 MW.

8. A method according to any one of the preceding claims, comprising operating the power-generating unit at period of peak or medium electric power demand.

9. A method according to any one of claims 1-8, wherein said power generating station are adapted for co-generation of electricity and heat.

10. A method according to Claim 9, comprising transporting the generated heat to a user.

11. A system for electric power generation, comprising: one or more small-to-medium size power-generating stations, each of which comprises one or more natural gas-operated electric power-generating unit, at least one natural gas feeding port and optionally a natural gas storage sub-system; and

- a fleet of one or more compressed gas transport vehicles for collecting natural gas at a natural gas dispensing station, transporting the natural gas to said power-generating stations and for feeding the natural gas into said feeding port.

12. A system according to Claim 11, wherein one or more of the stations have at least two feeding ports for connecting to at least two gas transport modules and comprising a switching mechanism for selectively linking the at least two feeding ports to the power-generating units.

13. A system according to Claim 11 or 12, wherein one or more of said stations comprise a natural gas storage sub-system connectible to said feeding port and to said power-generating unit for feeding gas thereinto and for supplying gas to said unit, respectively.

14. A system according to any one of claims 11-13, wherein one or more stations have a gas-feeding operational state in which natural gas is fed directly from the transport module through said port to the power-generating unit.

15. A system according to any one of claims 11-14, wherein one or more stations have a gas feeding state in which gas is fed to the power generating unit by the gas storage sub-system.

16. A system according to any one of claims 11-15, wherein one or more stations have three gas-feeding operational states, comprising: (i) a first gas-feeding state in which gas is fed from said transport module to said storage sub-system and to said power generating unit, (ii) a second gas-feeding state in which gas is fed from said transport module to said power-generating unit while the storage sub-system is sealed, and (iii) a third gas-feeding state in which gas is fed from the storage sub-system to said power-generating unit.

17. A system according to any one of claims 11-16, wherein said power generating stations have a power generating capacity of less than 50 MW.

18. A system according to Claim 17, wherein the power generating capacity is less than 20 MW.

19. A system according to Claim 18, wherein the power generating capacity is less than 10 MW.

20. A system according to any one of claims 11-19, wherein the power generating stations are intended for use at periods of peak or medium electric power demand.

21. A system according to any one of claims 11-20, wherein said station includes a cooling sub-system for cooling gas conduits or gas switching mechanism.

22. A system according to any one of claims 11-21, wherein said station is adapted for co-generation of electricity and heat.

23. A system according to Claim 22, wherein the power-generating units are associated with a heat absorption sub-system.

24. A system according to Claim 22 or 23, associated with a heat transport system for transporting the heat to one or more users.

25. A gas-operated power station comprising: a natural gas-operated power-generating unit;

- a gas feeding port for hooking up to a compressed natural gas (CNG) transport module;

- a gas storage sub-system; a gas piping system permitting gas flow (i) from the feeding port to the gas storage sub-system, (ii) from the feeding port to the power generating unit and (iii) from the storage sub-system to the power-generating unit; and a switching arrangement to permit different gas flow patterns at different gas feeding operational states.

26. A gas-operated power station according to Claim 25, having three gas-feeding operational states, comprising: (i) a first gas-feeding state in which gas is fed from said transport module to said storage sub-system and to said power generating unit, (ii) a second gas-feeding state in which gas is fed from said transport module to said power- generating unit while the storage sub-system is sealed, and (iii) a third gas-feeding state in which gas is fed from the storage sub-system to said power-generating unit.