Method for thermally assisted electric energy storage

Abstract

A proposed method for thermally assisted electric energy storage is intended for increase in round-trip efficiency through recovery of waste heat energy streams from the co-located power generation and industrial facilities, combustion of renewable or fossil fuels, or harnessing the renewable energy sources. In the charge operation mode, it is achieved by superheating and expansion of recirculating air stream in the liquid air energy storage with self-producing a part of power required for air liquefaction. In the discharge operation mode, it is attained through the repeated use of a stream of discharged air for production of an additional power in auxiliary discharge cycle.

Claims

1. A method for thermally assisted electric energy storage (TAEES), comprising in combination: pressurizing a process air, as a sum of fresh and recirculating air streams, up to an intermediate pressure with use of mechanically or electrically driven intercooled compressor train consuming an external power during TAEES charge; succeeding TAEES operation using the principle of at least one turbo expander-compressor based open air auto-refrigeration cycle and including: a) compressing the process air up to a top cycle pressure by the boost compressor; b) pre-cooling the entire process air; c) work-expanding the most part of pre-cooled process air down to a bottom cycle pressure and a corresponding its deep cooling; d) harnessing an expansion work for driving the said boost compressor; e) liquefying the rest of process air at a top cycle pressure and its expanding with a final cooling down to the bottom cycle pressure and temperature; f) separating the liquid and gaseous phases of the rest of process air; g) forming a recirculating air stream at a bottom cycle pressure as a mixture of the deeply-cooled most part of process air and a gaseous phase of the rest of process air; h) further sequential using a cold thermal energy of recirculating air for liquefying the rest of process air and pre-cooling the entire process air; storing the liquid air between the TAEES charge and discharge; performing the main TAESS discharge cycle through pumping the liquid air, its re-gasifying, further superheating at a sacrifice of an assistant thermal energy and expanding with producing the main discharge power; producing an additional discharge power in the auxiliary TAEES discharge cycle with use of the assistant thermal energy and a cold thermal energy released during the liquid air re-gasifying; and wherein in combination: a bottom pressure of said open air auto-refrigeration cycle is selected at a level exceeding atmospheric pressure by 1-10 bar and preferably by 3-8 bar; a recirculating air escaping the pre-cooler of process air is superheated with use of an assistant thermal energy delivered during TAEES charge in the amount of 100-300% of such energy delivered during TAEES discharge; a superheated recirculating air is further expanded down to near-atmospheric pressure with self-producing a power used for driving a compressor train and for decreasing the consumption of external charge power at least by 40%; and a said liquid air being pumped, re-gasified, heated and expanded in the main TAEES discharge cycle is further and repeatedly used as a working medium for producing a said additional discharge power in the auxiliary TAEES discharge cycle.

2. The method as in claim 1, wherein: an assistant thermal energy comprises at least a waste heat delivered from the co-located power generation or industrial facilities at a temperature of heat carrier exceeding 300 C. and preferably above 500 C.; the said co-located power generation or industrial facilities are selected from a group of facilities being operated during TAEES charge and discharge and exemplified but not limited by the simple cycle turbocharged reciprocating engine or gas turbine-based power plants, industrial heaters, furnaces, driers and other facilities with the gaseous and liquid waste heat streams, as well as by the concentrated solar power plants; a high temperature part of assistant thermal energy is added to a said waste heat part, aiming to increase a temperature of waste heat carrier from its said moderate level up to a selected higher value not exceeding 1000 C.; and adding a high temperature part of assistant thermal energy to waste heat stream is performed by deriving this energy from combustion of any available renewable or fossil fuels.

3. The method as in claim 1, wherein a designed amount of self-produced power in the TAEES charge cycle is provided through selecting a number of the stages of intercooled compressor train and a number of the turbo expander-compressors in the open air auto-refrigeration cycle, as well as through selecting a bottom pressure of said cycle, flow-rate and a temperature of heat carrier delivering a said assistant thermal energy to the TAEES facility.

4. The method as in claim 1, wherein the main TAEES discharge cycle comprises in combination: delivering a liquid air from a storage and its pumping up to top cycle pressure selected in the range between 60 and 200 barA; re-gasifying a liquid air through recovering a waste heat of main discharge cycle; further superheating a re-gasified air up to the temperature selected in the range between 500 and 600 C. with use of one part of an assistant thermal energy delivered into a superheater of main TAEES discharge cycle; a partial expanding the superheated re-gasified air down to an intermediate pressure selected in the range between 25 and 45 barA with producing a part of discharge power in the main TAEES discharge cycle; succeeding reheating a partially expanded re-gasified air with use of another part of an assistant thermal energy delivered into a reheater of main TAEES discharge cycle; a final expanding the reheated re-gasified air down to the near-atmospheric pressure with producing another part of discharge power in the main TAEES discharge cycle; and a said recovering a waste heat of air escaping the second expansion stage for re-gasifying a liquid air delivered from the storage with corresponding recovering a cold thermal energy of liquid air being re-gasified for deep cooling a said expanded air.

5. The method as in claim 4, wherein the said auxiliary TAEES discharge cycle comprises in combination: compressing a deeply cooled repeatedly used air up to a pressure selected in the range between 5 and 15 barA; preheating the compressed repeatedly used air through recovering a waste heat of auxiliary discharge cycle; further superheating the compressed repeatedly used air through recovering the rest of another part of assistant thermal energy delivered into a superheater of auxiliary TAEES discharge cycle from said reheater of main TAEES discharge cycle; expanding the superheated repeatedly used air down to the near-atmospheric pressure with producing an additional discharge power of the auxiliary TAEES discharge cycle; and recovering a waste heat of expanded repeatedly used air for the said preheating the compressed repeatedly used air.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments will hereinafter be described in detail below with reference to the accompanying drawings, wherein lie reference numerals represent like elements. The accompanying drawings have not necessarily been drawn to scale. Where applicable, some features may not be illustrated to assist in the description of underlying features.

(2) FIG. 1 is a schematic view of the first embodiment for implementing the invented method of the TAEES with one turbo expander-compressor based open air auto-refrigeration cycle used in the charge operation mode.

(3) FIG. 2 is a schematic view of the second embodiment for implementing the invented method of the TAEES in discharge operation mode.

(4) FIG. 3 is a diagram showing a relationship between a power self-produced by recirculating air expander, an expander inlet temperature and a number of turbo expander-compressors in auto-refrigeration cycle during TAEES charge.

(5) FIG. 4 is a diagram showing a relationship between a power self-produced by recirculating air expander and the external power consumed by compressor train with two turbo expander-compressor auto-refrigeration cycle vs. an expander inlet temperature and a number of train stages.

(6) FIG. 5 is a diagram showing a relationship between a specific charge power consumed by the compressor train with two turbo expander-compressor auto-refrigeration cycle, an expander inlet temperature and a number of train stages.

(7) FIG. 6 is a diagram showing a relationship between a power self-produced by recirculating air expander and the external power consumed by compressor train with one turbo expander-compressor auto-refrigeration cycle vs. an expander inlet temperature and a number of train stages.

(8) FIG. 7 is a diagram showing a relationship between a specific charge power consumed by the compressor train with one turbo expander-compressor auto-refrigeration cycle, an expander inlet temperature and a number of train stages.

(9) FIG. 8 is a diagram showing a relationship between a total discharge power produced by the TAEES facility, an expander inlet temperature and a number of turbo expander-compressors in auto-refrigeration cycle.

(10) FIG. 9 is a diagram showing a relationship between a grid round-trip efficiency of the TAEES facility with two turbo expander-compressor auto-refrigeration cycle, an expander inlet temperature and a number of compressor train stages.

(11) FIG. 10 is a diagram showing a relationship between a grid round-trip efficiency of the TAEES facility with one turbo expander-compressor auto-refrigeration cycle, an expander inlet temperature and a number of compressor train stages.

(12) FIG. 11 is a diagram showing a total discharge power produced by the TAEES facility and charge power consumed by the facility vs. an expander inlet temperature for one of the TAEES design configurations.

(13) FIG. 12 is a diagram showing the impact of expander inlet temperature during TAEES facility charge and discharge on the grid and recasted round-trip efficiencies of the facilities co-located with gas engine plant and having two different design configurations.

(14) FIG. 13 is a diagram showing the impact of expander inlet temperature during TAEES facility charge and discharge on the recasted round-trip efficiency of the facility co-located with gas turbine plant and having one selected design configuration.

DETAILED DESCRIPTION OF THE INVENTION

(15) The practical realization of the proposed method for thermally assisted electric energy storage (TAEES) may be performed through the operational integration between the Liquid Air Energy Storage (LAES) facility and any co-located source of waste thermal energy at a moderate temperature of the available heat carrier exceeding 300 C. and preferably exceeding 500 C. In addition, a possible increase in temperature of waste heat carrier up to a higher value not exceeding however 1000 C. should be provided, if needed. A bottom value of the waste heat carrier is determined by a possibility to get at least a minimum profit from the use of TAEES instead of the LAES with conventional one or two expander-compressor based liquefier. A top value of carrier high temperature may be selected in such a way as to use a simple uncooled design of the turbines and expanders being installed at the TAEES facility and accordingly to significantly reduce their first cost. At the same time any increase in temperature of heat carrier at the TAEES inlet leads to a corresponding enhancement of expanders (turbines) inlet temperature. In its turn this results in increasing a power self-produced during TAEES charge and correspondingly in decreasing a rate of external power consumed by the compressor train from the grid. With the technical and economic feasibility of increasing a carrier temperature above 1100 C. a power self-produced during TAEES charge may be comparable to a charge power consumed by the compressor train and there is not a need for consuming even a part of such charge power from the grid.

(16) In deciding on a source of thermal energy integrated with the TAEES, the preference should be given to the sources of waste or clean energy, such as exhaust gases of the simple cycle gas engine and gas turbine power plants, waste heat streams of the different industrial facilities and excessive solar thermal energy. A possible increase in temperature of heat carrier from a moderate up to a high value may be performed through combustion of any clean, preferably renewable fuel. A relationship between the quantities of thermal energy delivered into TAEES facility during its charge and discharge lies in the range from 3:1 to 1:1, depending on an inlet temperature of the supplied waste heat carrier, further enhancement of this temperature in one or both TAEES operation modes and a selected value of expander inlet temperature.

(17) The schematic view of the first embodiment for implementing the invented method of the TAEES with one turbo expander-compressor based open air auto-refrigeration cycle used in the charge operation mode is presented in the FIG. 1 and includes the following equipment packages: 100the air compressor train with associated equipment 200the one turbo expander-compressor train 300the liquefaction, separation and storage equipment package 400the recirculating air expander train 500the co-located source of assistant thermal energy with enhancer (if needed) of waste heat carrier temperature.

(18) As shown in the FIG. 1, the first equipment package 100 integrates the equipment required for pressurizing a process air up to an intermediate pressure during TAEES charge with use of electrically driven compressor train. The second and third equipment packages 200 and 300 integrate the equipment required for performing one turbo expander-compressor based open air auto-refrigeration cycle, which provides liquefying and storing a part of process air and forming a recirculating rest of process air at a bottom cycle pressure. Finally, the fourth equipment package 400 integrates equipment harnessing an assistant thermal energy delivered from the co-located source 500 of this energy at a required moderate or higher temperature and self-producing a power inside of TAEES facility, resulting in reduction of external power consumed by the compressor train 100.

(19) According to the proposed method, the charge of TAEES equipped with one turbo expander-compressor based open air auto-refrigeration cycle equipment is accomplished as follows. A stream of fresh air 101 from the atmosphere is compressed up to a selected low pressure at the first compressor stage 102, after-cooled in the cooler 103 and freeing from atmospheric moisture and carbon dioxide in the adsorber 104. The second compressor stage 105 provides first the after-cooled pressurizing of a recirculating air stream 406 incoming from the package 400 up to a said selected low pressure and then a further pressurizing of a process air, as a mixture of the fresh and recirculating air streams, up to an intermediate pressure. Compressor train is designed as at least two-stage compressor, wherein the first stage 102 and second stage 105 are driven by an electric motor 106. If needed, the second compression stage 105 may be designed in the intercooled configuration.

(20) The process air stream 110 escaping the aftercooler 109 at a said intermediate pressure is supplied to the booster compressor 201 driven by the turbo expander 202. Here a process air is pressurized up to a top cycle pressure and after-cooled in the cooler 203. Then a process air stream 204 is directed to the pre-cooler 301, wherein its temperature is further decreased well below 0 C. At the outlet of deep cooler 301 (point 302) the process air stream is divided into two streams 303 and 306. The most air part 303 is expanding down to a bottom cycle pressure in the said turbo expander 202 with an accompanied deep cooling of expanded air stream 304. In its turn, the rest part 306 of process air is deeply cooled and fully liquefied at a top cycle pressure in the air liquefier 307. The liquefied rest of process air is further directed into a generator loaded turbine 308, wherein it is expanded down to a bottom cycle pressure with an accompanied final cooling of expanded air down to bottom cycle temperature. A bottom cycle pressure is selected at a level exceeding atmospheric pressure by 1-10 bar and preferably by 3-8 bar. An air separator 309 installed at the outlet of expander 308 is used to separate the liquid and gas phases of the finally expanded and cooled rest of process air. The liquid air stream 312 is directed to the pressurized liquid air vessel 313, wherein it is stored at the bottom cycle pressure and temperature between the TAEES charge and discharge. The gaseous air stream 310 is directed to the point 305, wherein its mixing with an expanded and deeply cooled greater part 304 of process air is performed. This results in formation of deeply cooled recirculating air stream 311 at a bottom cycle pressure. The said recirculating air stream 311 is further sequentially used first for the deep cooling and liquefying the rest part 306 of process air in the air liquefier 307 and then for said pre-cooling the process air stream in the pre-cooler 301. Heat exchange in the air liquefier 307 and pre-cooler 301 leads to a progressive heating of recirculating air and a temperature of outgoing recirculating air stream 314 above 0 C.

(21) The said air stream 314 is further directed to the recirculating air expander package 400, wherein it is firstly preheated in the recuperator 401 and then finally heated up to a top cycle in the superheater 402. The superheating a recirculating air is performed at the sacrifice of a heat exchange with the stream 403 of heat carrier which is delivered from an external co-located source of thermal energy 500 at the required moderate or higher temperature and returned to the energy source 500 as the stream 404 at the reduced temperature. The superheated recirculating air stream is directed into a recirculating air expander 405, which is placed on the common shaft with the compressor stages 102 and 105 and electric motor 106. However, the recirculating air expander 405 may be designed as a separate turbomachinery and equipped with its own electric generator. In the recirculating air expander 405 the superheated air is expanded down to near atmospheric pressure with an accompanied partial cooling of the expanded air. A mechanical power self-produced by the recirculating air expander 405 reduces an amount of electric power consumed by the compressor train from the grid and leads to a decrease in required installed horsepower of the electric motor 106. Hypothetically, one can envision a situation at which a power self-produced by the expander 405 exceeds a power consumed by the compressor train, resulting in possibility for replacement of electric motor by a motor-generator. However, conversion of the TAEES facility into a system co-producing liquid air and power in charge operation mode is possible only with the availability and by fulfillment of a number of the mentioned above and other conditions. The finally expanded and partially cooled recirculating air stream is directed from the expander 405 to the recuperator 401, wherein the remainder of its hot thermal energy is used for the said preheating of the recirculating air stream 314 at the inlet of package 400. The described cycle is completed by delivering a recirculating air stream 406 at the near atmospheric pressure from the outlet of recuperator 401 to the inlet of the second compression stage 105.

(22) The described method for charging the TAEES facility is applicable to its configurations both with one turbo expander-compressor open auto-refrigeration cycle, as outlined above, and with two turbo expander-compressor cycle (not shown in the drawing), as well as to the compressor train with a number of stages greater than two (not shown in the drawing). As this takes place, it should be stressed that an increase in number of the turbo expander-compressors installed and used stages of compressor train significantly decreases a power consumed for the charge of TAEES facility, but leads to a some increase in complexity and first cost of the charge equipment.

(23) The schematic view of the third embodiment for implementing the invented method of the thermally assisted electric energy storage (TAEES) in discharge operation mode is presented in the FIG. 2 and includes the following equipment packages: 300the liquefaction, separation and storage equipment 500the co-located source of assistant thermal energy 700the main discharge power production block 800the auxiliary discharge power production block.

(24) Operation of the TAEES facility in discharge cycle mode is performed as follows. A stream 317 of liquid air is extracted at a bottom cycle pressure from the storage 316 and pumped by a pump 318 up to a top cycle pressure. A said top pressure is selected in the range between 60 and 200 bar. At this pressure the stream 319 of liquid air is delivered into air re-gasifier 701, wherein the liquid air regasification process is supplemented by some preheating a regasified air. A further increase in regasified air temperature is performed in the superheater 702 at the sacrifice of heat exchange with a heat carrier stream delivered from a co-located source of assistant thermal energy 500 through a pipe 707 and returned into source 500 through a pipe 708. Before entering the superheater 702 a temperature of heat carrier may be increased from a moderate up to a required higher level (not shown in the drawing). A superheated regasified air is further expanded in the first stage 703 of the air expander train comprising at least two stages (703 and 705) and electric generator 706, which converts a mechanical work of expanded air into electric power. A modernized back-pressure steam turbine may be used as the first (high-pressure) stage of air expander, therefore at any temperature of heat carrier incoming from the source 500 a control valve 712 should be adjusted so that a temperature of superheated regasified air at the inlet of expander 703 does not exceed 500-600 C. The regasified air partially expanded in the expander 703 down to 25-45 bar is further reheated in the reheater 704 up to the top cycle temperature. For these purposes a thermal energy of heat carrier incoming from an external source 500 through a pipe 709 and exhausting through a pipe 710 is used. A final expanding of reheated regasified air down to near atmospheric pressure is performed in the second (low-pressure) stage 705 of air expander train and accompanied by some cooling a stream 711 escaping the LP stage of expander. An industrial expander or conventional gas turbine may be used as the second (low-pressure) air expander 705. Its operation is possible as uncooled turbomachinery at the inlet air temperature not exceeding 1000 C. Operation of LP air expander at the higher values of inlet air temperature calls for usage of turbomachinery with a more complicated and expensive cooled design of rotor blading. But at any temperature a regasified air escaping the expander train possesses a sufficient thermal energy to be used in the regasifier 701 for the said liquid air regasifying and regasified air preheating, completing in such a manner the main discharge cycle.

(25) A stream 801 of the air coming from the regasifier 701 at near atmospheric pressure is deeply cooled, resulting from heat exchange with the liquid air being regasified. This air is further repeatedly and highly efficiently used in the auxiliary discharge cycle. This is because a work of so-called cold compressor pressurizing the air at a cryogenic inlet temperature is drastically reduced, as compared to the compression of air at the normal inlet temperature. In addition, since the repeatedly used air is free from H.sub.2O and CO.sub.2 components, any its pretreatment is not required. A repeatedly used air is pressurized in the one-stage compressor 802 up to top pressure of 5-15 bar of the auxiliary discharge cycle and delivered into a recuperator 803 for its preheating at the sacrifice of waste heat of auxiliary cycle. A temperature of preheated repeatedly used air is further increased in the auxiliary superheater 804, wherein an assistant thermal energy of heat carrier stream 710 escaping the main superheater 704 of regasified air is used for superheating a repeatedly used process air up to top temperature of the auxiliary discharge cycle. Expanding a superheated repeatedly used air in the air expander 805 down to the bottom near-atmospheric pressure is accompanied by fulfillment of a work, which after deduction of compressor 802 work is converted by the generator 806 into an additional power of the said auxiliary discharge cycle. This additional power is in the range from 10 to 20% of the power of main discharge cycle. The expanded repeatedly used air is directed to the said recuperator 803. Here its thermal energy is used for said preheating a pressurized repeatedly used air coming from compressor 802. A heat transfer between two streams of repeatedly used air leads to cooling the stream 807 escaping the recuperator 803 before its exhaust into atmosphere.

INDUSTRIAL APPLICABILITY

(26) The performances of Thermally Assisted Electric Energy Storage (TAEES) facility using the proposed method of operation are presented below. The calculation of these performances has been performed for the case of a possible integration between a 5-10 MW TAEES facility and co-located thermal energy source with available outgoing stream of a waste heat carrier at a moderate temperature in the range between 300 and 600 C. It is assumed that a said temperature level may be if needed enhanced at the TAEES inlet up to a required higher value selected in the range up to 1010 C. Such enhancement may be performed both in the TAEES charge and discharge modes, or only in one of the said modes, thereby the selected high temperatures of heat carrier streams may be both identical and different during TAEES charge and discharge.

(27) In the conducted feasibility study the TAEES facility is equipped with the equipment making possible to realize one or two turbo expander-compressor (1 TC or 2 TC) based open air auto-refrigeration cycle during charge period and to recover an obtained assistant thermal energy during TAEES charge and discharge. The intercooled air compressor train has from two to four stages (2 st AC-4 st AC) placed on the common shaft with the recirculating air expander and electric motor. The TAEES facility is also equipped with the equipment for fulfillment of the main and auxiliary discharge cycles.

(28) The given and assumed technical data used in numerical simulation of the TAEES facility performance are listed in the Table 1 below.

(29) TABLE-US-00001 TABLE 1 Parameter Unit Data TAEES facility discharge power at the identical number of MW 5-10 charge and discharge hours Number of intercooled air compressor train stages (st AC) 2-4 Total compressor polytropic & mechanical efficiency % 87 Total expander adiabatic & mechanical efficiency % 87 Total coupling & electric motor efficiency of turbomachinery % 97.5 Number of turbo expander-compressors (TC) 1-2 Isentropic liquid air expander efficiency % 85 Isentropic liquid air pump efficiency % 80 Small generator/motor efficiency % 96 Compressor train intermediate pressure (for 2TC/1TC cycles) barA 34.5/39.6 Top auto-refrigeration cycle pressure (for 2TC/1TC cycles) barA 61.7 Bottom auto-refrigeration cycle pressure (for 2TC/1TC cycles) barA 6.7 Inlet temperature of heat carrier during LAES charge/discharge C. 560-1010 Pumping pressure of liquid discharged air barA 150 Assumed pressure drop in piping barA 0 Assumed pressure drop in each heat exchanger barA 0.025 Discharged regasified air pressure at HP expander outlet barA 43 Repeatedly used air pressure at compressor outlet barA 11

(30) In their turn, the calculated performance resulted from numerical simulation of the TAEES facility charge are presented in the Table 2 and FIG. 3-7 for operation of facility with 2 st-4 st air compression stages and two and one turbo expander-compressors (TC) in the air compression, refrigeration and liquefaction cycle. Here the following designations are used: Xst ACa number of stages in the intercooled compressor train, wherein X=2, 3 and 4; T.sub.EITrecirculating air expander inlet temperature during TAEES charge without enhancement (350 C. and 560 C.) and after enhancement (710-1010 C.) of assistant thermal energy;

(31) TABLE-US-00002 TABLE 2 Xst AC T.sub.EIT, G.sub.PA, G.sub.LA, W.sub.AC-CH, W.sub.AE-CH, W.sub.AE-CH/ W.sub.CH, .sub.CH, Q.sub.TH-CH, X = 2-4 C. kg/s kg/s kWm kWm W.sub.AC-CH, % kWe kWh/ton kWth Two turbo expander-compressors auto-refrigeration cycle 4st AC 350 48.0 8.9 20341 8750 43.0 11837 369 8897 560 48.0 8.9 20341 11853 58.3 8654 270 12003 710 48.0 8.9 20341 14097 69.3 6353 198 14249 860 48.0 8.9 20341 16364 80.4 4028 126 16519 1010 48.0 8.9 20341 18648 91.7 1685 53 18805 3st AC 560 48.0 8.9 21254 11853 55.8 9591 299 12003 710 48.0 8.9 21254 14097 66.3 7289 228 14249 860 48.0 8.9 21254 16364 77.0 4964 155 16519 1010 48.0 8.9 21254 18648 87.7 2622 82 18805 2st AC 560 48.0 8.9 23372 11853 50.7 11763 367 12003 710 48.0 8.9 23372 14097 60.3 9462 295 14249 860 48.0 8.9 23372 16364 70.0 7137 223 16519 1010 48.0 8.9 23372 18648 79.8 4794 150 18805 One turbo expander-compressor auto-refrigeration cycle 4st AC 560 48.0 7.3 21207 12207 57.6 9191 350 12371 710 48.0 7.3 21207 14524 68.5 6814 259 14689 860 48.0 7.3 21207 16865 79.5 4413 168 17033 1010 48.0 7.3 21207 19224 90.6 1994 76 19395 3st AC 560 48.0 7.3 22156 12207 55.1 10164 387 12371 710 48.0 7.3 22156 14524 65.6 7788 296 14689 860 48.0 7.3 22156 16865 76.1 5387 205 17033 1010 48.0 7.3 22156 19224 86.8 2967 113 19395 2st AC 560 48.0 7.3 24331 12207 50.2 12394 472 12371 710 48.0 7.3 24331 14524 59.7 10018 381 14689 860 48.0 7.3 24331 16865 69.3 7617 290 17033 1010 48.0 7.3 24331 19224 79.0 5197 198 19395
G.sub.PA and G.sub.LAflow-rates of process and liquid air; W.sub.AC-CH and W.sub.AE-CHmechanical power consumed by compressor train and self-produced by recirculating air expander; W.sub.CH=W.sub.AC-CHW.sub.AE-CHresulting power consumed by the TAEES facility during its charge; .sub.CH=W.sub.CH/(G.sub.LA3.6)specific charge power consumed by the TAEES facility during its charge; and Q.sub.TH-CHassistant thermal energy input during TAEES charge.

(32) The calculated performance resulted from numerical simulation of the TAEES facility discharge are further presented in the Table 3 and FIG. 8 with regard to different amounts of liquid air produced during TAEES charge using two and one turbo expander-compressors (TC). Here the following designations are used: T.sub.EITregasified air expander inlet temperature during TAEES discharge without enhancement (350 C. and 560 C.) and after enhancement (710-1010 C.) of assistant thermal energy; G.sub.LAflow-rate of liquid process air; W1.sub.AE-DCH and W2.sub.AE-DCHmechanical power produced by the HP and LP regasified air expanders in the main discharge cycle; W.sub.AC-DCHmechanical power consumed by repeatedly used air compressor of auxiliary discharge cycle; W3.sub.AE-DCHmechanical power produced by the repeatedly used air expander in the auxiliary discharge cycle; W.sub.DCHtotal electric power produced by the TAEES facility during its discharge; .sub.ADD=(W3.sub.AE-DCHW.sub.AC-DCH)/(W1.sub.AE-DCH+W2.sub.AE-DCH)a ratio between the power of an auxiliary and main discharge cycles; and Q.sub.TH-DCHassistant thermal energy input during TAEES discharge.

(33) TABLE-US-00003 TABLE 3 T.sub.EIT, G.sub.LA, W1.sub.AE-DCH, W2.sub.AE-DCH, W.sub.AC-DCH, W3.sub.AE-DCH, W.sub.DCH, .sub.ADD, Q.sub.TC-DCH, C. kg/s kWm kWm kWm kWm kWe % kWth for TAES with two turbo expander-compressors cycle 350 8.9 1432 3192 726 1282 5051 12.0 8560 560 8.9 2004 4338 1250 2476 7187 19.3 10423 710 8.9 2013 5171 1250 2541 8071 18.0 11329 860 8.9 2000 6016 1250 2584 8924 16.6 12205 1010 8.9 2012 6871 1250 2663 9846 15.9 13151 for TAES with one turbo expander-compressor cycle 560 7.3 1646 3558 1025 2043 5908 19.6 8564 710 7.3 1652 4241 1025 2102 6637 18.3 9312 860 7.3 1653 4935 1025 2159 7371 17.2 10063 1010 7.3 1646 5636 1025 2210 8097 16.3 10807

(34) The resulting performance of the TAEES facility derived from its calculated performance in the charge and discharge modes is presented in the Table 4 and FIG. 9-10, as applied to the TAEES facility which may be equipped with 2 or 3 or 4 stage intercooled compression train and 1 or 2 turbo expander-compressors and supplied with the exhaust gas stream from the co-located simple cycle gas turbine plant at the moderate temperature of 560 C. in the charge and discharge TAEES operation modes. A said temperature level may be enhanced up to 710-1010 C., resulting in a drastic increase in the TAEES grid round trip efficiency (RTE) values, which are presented using the following designations: RTE.sub.GRID=W.sub.DCH/W.sub.CH, where W.sub.DCHa total electric power delivered by the TAEES facility to the grid during facility discharge and W.sub.CHa resulting electric power consumed by the TAEES facility from the grid during facility charge.

(35) TABLE-US-00004 TABLE 4 TAEES RTE.sub.GRID = W.sub.DCH/W.sub.CH, % T.sub.EIT, 2 Turbo Expander-Compressors 1 Turbo Expander-Compressor C. 4st AC 3st AC 2st AC 4st AC 3st AC 2st AC 560 83 75 61 64 58 48 710 127 111 85 97 85 66 860 222 180 125 167 137 97 1010 584 376 205 406 273 156

(36) However, in the case of TAEES facility its RTE.sub.GRID value defines quantitatively the TAEES interplay solely with the grid and does not take into consideration the quantity, temperature level and energy value of assistant thermal energy flow obtained from the co-located energy source and means for enhancement of temperature level of this energy flow. To give a total quantitative assessment of the said interplay between the TAEES facility, electrical grid and co-located sources of assistant thermal energy it is suggested to use a so-called facility recasted round trip efficiency (RTE.sub.REC). A procedure of its determination is described below as applied to the TAEES facility which may be co-located with a simple cycle power plant, using as an example the reciprocating prime mover being in service during the TAEES charge and discharge. It is assumed that TAEES facility is equipped with 4 stage intercooled compression train and 2 turbo expander-compressors and uses the exhaust gas stream of the co-located plant providing a moderate air expander inlet temperature of 350 C. A said air temperature level at the expander inlet may be enhanced up to 560-1010 C. during TAEES facility charge and/or discharge, resulting in an impressive decreasing the resulting charge power W.sub.CH and increasing the resulting discharge power W.sub.DCH (see FIG. 11). In so doing, there is a need to take into account the following circumstances.

(37) Firstly, the simplest way for increase in air expander inlet temperature is an increase in temperature of waste heat carrier through combustion of any available fuel and above all of excessive fuel from the national natural gas grid. Such excess of fuel at a frequently reduced price occurs during the off-peak hours in the electrical grid, which are usually chosen for energy storage charge. Secondly, as is evident from the FIG. 11, a drop in resulting power consumed during TAEES charge (W.sub.CH) due to the increase in air expander inlet temperature from 350 up to 1010 C. exceeds an alternative rise in total power produced during TAES discharge (W.sub.DCH) more than three and half times. However the need for immediate enhancement of the heat carrier temperature during TAEES charge does not exclude a possibility and expediency of the similar temperature enhancement during TAEES discharge or simultaneously during TAEES charge and discharge.

(38) At the same time consideration must be given to the different results from such enhancement in air expander inlet temperature. As will be shown below, during TAEES charge it leads to an impressive increase in RTE.sub.REC value without any changes in the W.sub.DCH values, whereas during TAEES discharge it makes possible to reach a less significant enhancement of RTE.sub.REC value but with simultaneous and marked increase in the W.sub.DCH value. The greatest increase in the RTE.sub.REC value with a said simultaneous increase in its W.sub.DCH value may be obtained from concurrent use of the recirculating and regasified air at the enhanced temperatures during TAEES charge and discharge. Finally, there is a need for assessment of the energy value of fuel being used for increase in temperature of supplied heat carrier accompanied by production of an additional power in the charge and discharge cycles. In so doing, account must be taken of the average efficiency (.sub.GRID) of converting the fuel into power in the grid which is currently estimated at .sub.GRID31% with regard to losses of this power in the grid. The said additional power should be added to the calculated W.sub.CH value, if fuel is used for increase in heat carrier temperature during TAEES charge and subtracted from the calculated W.sub.DCH value, if fuel is used for increase in heat carrier temperature during TAEES discharge.

(39) The dependence of the grid and recasted RTE values on the expander inlet temperatures are graphically presented in the FIG. 12 for two selected cases of operating the TAEES facility co-located with gas engine plant. In the first case during TAEES facility discharge a waste heat carrier is delivered without any enhancement in its temperature, resulting in regasified air expander inlet temperature of T.sub.EIT-DCH=350 C. During TAEES facility charge a temperature of waste heat carrier is enhanced, resulting in recirculating air expander inlet temperature of T.sub.EIT-CH=710-1010 C. In the second case an enhancement of waste heat carrier temperature is performed both during facility charge and discharge and in such a way that the temperature equality T.sub.EIT-CH=T.sub.EIT-DCH is provided in the range from 710 C. to 1010 C. As shown in the FIG. 12, the recasted values of round trip efficiency (RTE.sub.REC) are significantly less than its grid values (RTE.sub.GRID) especially in the region of the high expander inlet temperatures. Nevertheless, an increase in these temperatures makes possible to provide a significant enhancement of the RTE.sub.REC values even with the use of the elevated temperatures only during TAEES charge. A further drastic increase in the RTE.sub.REC values may be achieved using the elevated expander inlet temperatures during TAEES charge and discharge alike. By and large the presented data testify the technical and economic expedience of integrating the LAES and co-located gas engine plant into the TAEES facility.

(40) The even greater benefits may be derived from integration of the TAEES facility with any other thermal energy source having a higher initial temperature of waste heat carrier, such as a simple cycle gas turbine. Resulting from a higher temperature of gas turbine exhaust assumed at a level of 570 C., a lesser difference in RTE.sub.GRID and RTE.sub.REC values may be obtained as the waste heat carrier temperature further enhances. In its turn this results in the greater values of the RTE.sub.REC in all cases of the enhanced heat carrier temperature usage. For example, as evident from the Table 5 and FIG. 13 co-location with the gas turbine plant and enhancement of expander inlet temperature from 560 C. up to 860 C. during TAEES charge and discharge provides the TAEES RTE.sub.REC value at a level of 154%, whereas co-location with the gas engine plant and enhancement of expander inlet temperature from 350 C. up to the same value of 860 C. makes possible to reach RTE.sub.REC value of 122% only (see FIG. 12). A general grasp of the variety of achievable RTErec values for the TAEES facility co-located with the gas turbine plant at the different combinations of expander inlet temperatures during TAEES charge and discharge can be gained from the Table 5 and FIG. 13.

(41) The Table 5 and FIG. 13 make possible to determine any resulting TAEES RTE.sub.REC value for the selected combination of the expander inlet temperatures during facility charge and discharge and given configuration of the TAEES facility co-located with GT plant. For example, TAEES facility using the common expander inlet temperatures T.sub.EIT-CH=T.sub.EIT-DCH=785 C. during facility charge and discharge (see point A in FIG. 13) will have RTE.sub.REC=132%. On the other hand, the same Table 5 and FIG. 13 make possible to determine the required expander inlet temperature in any TAEES process (charge or discharge) to reach a given value of the facility RTE.sub.REC at a given expander inlet temperature in another TAEES process (discharge or charge). For example, for the given RTE.sub.REC value of 96% and at the T.sub.EIT-CH=635 C. of recirculating air expander inlet temperature in the charge process (see point B in FIG. 13) the discharge process at the TAEES facility should be conducted at the same temperature of T.sub.EIT-DCH=635 C. at the inlet of regasified air expander.

(42) TABLE-US-00005 TABLE 5 RTE.sub.REC values of the TAEES facility T.sub.EIT-DCH, C. T.sub.EIT-CH, C. 1010 860 710 560 1010 237 220 204 189 860 165 154 143 132 710 129 120 111 102 560 104 97 90 83
inlet temperature (see point B) the discharge process at the TAEES facility should be conducted at the same temperature of T.sub.EIT-DCH=635 C. at the inlet of regasified air expander.

(43) It should be noted that the term comprising does not exclude other elements or steps and a or an do not exclude a plurality. It should also be noted that reference signs in the claims should not apparent to one of skill in the art that many changes and modifications can be effected to the above embodiments while remaining within the spirit and scope of the present invention. For example, a thermally assisted process of air liquefaction described in the present invention could be applied to the air separation and liquefaction of the different gases, including ASU technique and LNG production plants.