Abstract:
An energy conversion apparatus and method using captured energy of building wind resistance, supplemented by solar radiation and by liquefied air transferred to the building or made by excess captured energy. The energy sources are combined, as available, to drive a compressor for supplying intake working fluid of an engine of a reserve system, wherein the liquefied air provides pre-compression cooling of an atmospheric air portion of the working fluid. The liquefied air is stored and transferred between buildings and between buildings and vehicles, as required.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority of Provisional Application Ser. No. 60/602,949, filed Aug. 20, 2004.  
                                                     References Cited:       U.S. Patent Documents                                    4,182,960    1/1980   Reuyl   290/1R           4,227,374   10/1980   Oxley      60/651           4,229,941   10/1980   Hope      60/641.15               4,294,323   10/1981   Boese        180/69.5                      
 
       Other Publications  
       [0000]    
       
          “Ultra-Low Emission Liquid Nitrogen. Automobile” Knowlen, Mattick, Hertzberg,  
          Web Site, University of Strathclyde, Scotland (www.esru.strath.ac.uk/EandE/Web_sites/01-02/RE_info/Urban%20wind.htm) Web Site, MGx Wind Electric (http://mgx.com/)  
       
     
     
    
     BACKGROUND OF THE INVENTION  
       [0004]     This invention presents a unique wind energy converter for providing power to a building in conjunction with supplementary energy sources including imported cryogenic heat sink liquid for a reserve engine, while utilizing excess captured energy to produce additional heat sink liquid for export to vehicles and other buildings.  
         [0005]     Economical on-site generation of power in conjunction with renewable sources has long been a goal of building design to provide energy independence, conserve fossil fuels, and to lessen emission of combustion products. Several concepts are described in the prior art using wind energy dissipated by a building to provide power to the building. They are inefficient, capture a relatively small percentage of dissipated energy, and wind turbine designs are not optimized. With the exception of storage and transfer of electrical energy between buildings and vehicles, the prior art does not describe coordinated storage and transfer of captured energy using the full range of combined systems including pneumatic, cryogenic and electric, for both instant and reserve use. Relevant building energy capture, conversion and consumption devices of the prior art have disadvantages, as follows:  
         [0006]     (a) The prior art describes a fixed ducted wind turbine for capture of wind impact on roof tops. The turbine, integrated with the roof structure, was tested atop a Glasgow, Scotland lighthouse by Energy Systems Research Unit, University of Strathclyde, Scotland (www.esru.strath.ac.uk/EandE/Web_sites/01-02/RE_info/Urban%20wind.htm). Power output is limited because wind discharges to relatively weak suction in line with the turbine axis.  
         [0007]     (b) The prior art describes a movable ducted wind turbine-generator combined with a wind blocking and tracking panel for capture of wind impact at selected roof top locations. The turbine-generators are available from MGx Wind Electric (http://mgx.com/). Positioning for shifting winds is problematic and power output is limited because blockage area is provided by the panel rather than the building.  
         [0008]     (c) U.S. Pat. No. 4,182,960 to Reuyl (1980) describes transfer of renewable energy between stationary sites and vehicles after conversion to electricity. Solar energy recovered at a site is stored in batteries to provide power to the site and a portion is transferred to, and stored in batteries in a hybrid gas turbine-electric vehicle. The turbine engine of the vehicle, capable of burning a renewable fuel, provides power to the site via an electric generator to supplement site solar energy. Energy transfer using batteries has several problems including space and weight limitation, shortened battery life with high electric discharge, replacement handling, charge time, and ventilation.  
         [0009]     U.S. Pat. No. 4,227,374 to Oxley (1980) describes a method for storage of excess energy produced by renewable sources or by a conventional power station. The energy is used to liquefy atmospheric nitrogen and oxygen which is stored at cryogenic temperature and used, in combination with an over atmospheric temperature heat source, for powering a heat engine. Use of the liquefied gas for energy transfer and for indirect storage by engine efficiency gain is not recognized.  
         [0010]     Other energy storage concepts described in the prior art, including batteries, compressed air and pumped hydro, can only provide reserve power for a few days without solar or wind input. This is because of low energy density; batteries are weight limited, compressed air is volume limited, and pumped hydro is height limited.  
         [0011]     (d) U.S. Pat. No. 4,229,941 to Hope (1980) describes electric generation using combined solar and wind energy sources. Power output of this kind of system is limited by inability to store and efficiently reuse excess energy produced during periods of above average wind and solar capture.  
         [0012]     (e) U.S. Pat. No. 4,294,323 to Boese (1981) describes a cryogenic engine using imported liquid nitrogen. This device has low specific expansion energy and recent research programs at the University of Washington and at the University of North Texas worked on maximizing output by designing for quasi-isothermal expansion. Additional development is needed to improve isothermicity and to operate with working fluid above atmospheric temperature.  
         [0013]     (f) The prior art describes describes the use of liquefied gas in cryogenic engines, but does not adequately address efficiency and cost of providing the liquefied gas. State-of-the-art air liquefiers including; vapor-compression, magnetic, Stirling cycle and thermo-acoustic, are relatively inefficient. Work input of approximately 2.5 times the ideal heat removal per 2.2 kg (1 lb) of air liquefied can be achieved.  
         [0014]     (g) Micro-gas turbine generators in the 30 to 100 kW (40 to 134 hp) range are described in the prior art for distributed generation to buildings. Several of these burn renewable fuels, such as the units by Capstone Turbines (www.capstoneturbine.com/index.cfm). Thermal performance of micro-turbines and associated compressors is less than with full size units because leakage paths are large relative to engine size. Other problems include high compression work, high turbine blade and exhaust gas temperature, and expensive heat exchangers. Low grade fuels such as kerosene can be burned, however emissions are high due to high fuel consumption and formation of compounds at high temperature. Operation is characterized by falling efficiency with load.  
       SUMMARY OF THE INVENTION  
       [0015]     It is an object of the present invention, therefore to provide a unified energy system for efficient capture of wind energy dissipated by a building and for combining building dissipated wind with other available energy sources, such as solar insolation, and liquefied gas transferred between buildings and vehicles.  
         [0016]     It is another object of the present invention to provide an efficient reserve system to meet building energy requirements when recoverable energy sources are insufficient.  
         [0017]     In keeping with these objects and others which may become apparent, the present invention seeks to provide a unified energy system to recover, store, transfer and consume energy dissipated by a building or otherwise available thereto. It is estimated that up to 25% of wind energy dissipated by a building in the range of only 13 to 16 km/hr (8 to 10 mph) is recoverable.  
         [0018]     Liquefied air functions as indirect energy storage by raising reserve engine efficiency. In addition to imported liquefied air, a liquefier makes liquefied air using excess captured energy during above average winds when building wind resistance, a function of the third power of wind speed, predominates. Excess liquefied air is transferred for use in vehicles or at other building sites.  
         [0019]     Combining recoverable energy sources yields greater benefit than when taken individually. For example, up to a three-fold increase in efficiency of a gas turbine reserve engine is realized using captured energy to provide the engine with compressed air, pre-cooled by liquefied air. Accordingly, advantages of the present invention are illustrated as follows:  
         [0020]     (a) A feature of the energy system in accordance with the present invention lies in providing a building integrated system for efficient capture of wind energy having a turbine-generator driven by the difference between impact and wake pressures while discharging to high suction locations behind roof corners.  
         [0021]     (b) Another feature of the energy system in accordance with the present invention lies in providing a building integrated system for efficient capture of wind energy having a turbine-generator driven by the difference between impact pressure and wake pressure while discharging through a variable area duct system to follow changing wake pressures.  
         [0022]     (c) Another feature of the energy system in accordance with the present invention lies in providing liquefied air storage of captured energy, plus capability to transfer liquefied air between buildings and vehicles.  
         [0000]     The liquefied gas provides storage indirectly by reducing compression work in a reserve engine.  
         [0023]     (d) Another feature of the energy system in accordance with the present invention lies in providing a unified recoverable energy system for combining building dissipated wind energy, solar insolation and imported liquefied gas. This combination of energy sources is available to most buildings.  
         [0024]     (e) Another feature of the energy system in accordance with the present invention lies in providing a reserve system with a quasi-isothermal liquefied air expander. Pre-compression cooling of atmospheric air working fluid with cryogenic heat sink fluid increases performance by reducing compression work. Equivalent mass storage based on efficiency gain of a liquefied air powered expander is approximately three times as compared to batteries.  
         [0025]     (f) Another feature of the energy system in accordance with the present invention lies in providing an air liquefier to liquefy atmospheric air. Liquefier work input is equivalent to that of state-of-the-art liquefiers, however the captured energy driving the liquefier is only a virtual energy loss.  
         [0026]     (g) Still another feature of the energy system in accordance with the present invention lies in providing an efficient micro-turbine reserve engine for use when captured energy is insufficient. Pre-compression cooling of an atmospheric air portion of working fluid with cryogenic heat sink fluid enables reduced turbine inlet and exhaust temperatures. Heat input is from a renewable fuel, such as methanol. Low fuel consumption lowers emissions while expanding fuel choices, and efficiency is relatively constant over the load range. Equivalent mass storage based on efficiency gain of a fuel and liquid air powered engine is approximately eight times, as compared to batteries. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     Objects and advantages of the present invention will become apparent from the following when read in conjunction with the accompanying drawings and reference numeral list, wherein solid lines joining components indicate fluid flow, arrows indicate flow direction, and dashed lines indicate electrical connection:  
         [0028]      FIG. 1  is a schematic illustration showing connection of components of a wind energy capture system with a reserve system for providing power to a building.  
         [0029]      FIG. 2  is a schematic illustration showing connection of components of a reserve engine system of the building of  FIG. 1 .  
         [0030]      FIG. 3  is a plan illustration of a building with wind turbine discharge to selected wake regions of the roof of the building of  FIG. 1  through variable duct area for enhanced wind capture.  
         [0031]      FIG. 4  is a schematic illustration showing connection of a photo-voltaic panel for providing supplementary power to the building of  FIG. 1 .  
     
    
       [0032]    
       
         
               
             
               
               
               
             
           
               
                   
               
               
                   
               
               
                 Reference Numerals In Drawings 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 
                   FIG. 1 
                 
                   
               
               
                   
                 10 
                 building 
               
               
                   
                 11 
                 roof 
               
               
                   
                 12 
                 windward corner 
               
               
                   
                 13 
                 recess 
               
               
                   
                 14 
                 wind drive 
               
               
                   
                 15 
                 wind turbine 
               
               
                   
                 16 
                 main generator 
               
               
                   
                 17 
                 controller 
               
               
                   
                 18 
                 outlet duct 
               
               
                   
                 19 
                 wake region 
               
               
                   
                 20 
                 reserve system 
               
               
                   
                 
                   FIG. 2 
                 
               
               
                   
                 21 
                 reserve engine 
               
               
                   
                 22 
                 gas turbine 
               
               
                   
                 23 
                 compressor 
               
               
                   
                 24 
                 combustor 
               
               
                   
                 25 
                 recuperator 
               
               
                   
                 26 
                 header 
               
               
                   
                 27 
                 fuel pump 
               
               
                   
                 28 
                 reserve generator 
               
               
                   
                 29 
                 pumped air valve 
               
               
                   
                 30 
                 compressed air valve 
               
               
                   
                 31 
                 air liquefier 
               
               
                   
                 32 
                 pressurizer 
               
               
                   
                 33 
                 liquid air tank 
               
               
                   
                 34 
                 liquid air pump 
               
               
                   
                 35 
                 evaporator 
               
               
                   
                 36 
                 fill valve 
               
               
                   
                 37 
                 drain valve 
               
               
                   
                 38 
                 fuel tank 
               
               
                   
                 
                   FIG. 3 
                 
               
               
                   
                 39 
                 variable discharge system (typical) 
               
               
                   
                 40 
                 plenum valves (typical) 
               
               
                   
                 41 
                 wake region (typical) 
               
               
                   
                 42 
                 eaves plenum 
               
               
                   
                 43 
                 valve operators (typical) 
               
               
                   
                 44 
                 pressure sensors (typical) 
               
               
                   
                 
                   FIG. 4 
                 
               
               
                   
                 45 
                 photo-voltaic panel 
               
               
                   
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0033]      FIG. 1  illustrates a preferred embodiment of the energy capture and reserve system of the present invention installed in a building  10  with a roof  11  and a windward corner  12  with a recess  13  containing a wind drive  14 . Wind energy captured by a wind turbine  15  of drive  14  provides power from a main generator  16  to the building through a controller  17  while wind discharges through an outlet duct  18  to a wake region  19  of the roof. A reserve system  20  provides power to controller  17 .  
         [0034]     Energy capture works on the principle of parallel flow under equal pressure difference, with main flow over the building producing a smaller bypass flow through a turbine and duct. Performance is evaluated for a representative building demand of 15 kWhr (20 hphr) per day for a two story building with 186 m2 (2000 ft2) floor area and 46 m2 (500 ft2) frontal area. Demand for one day is met with wind capture by drive  14  at continuous upstream wind speed of 16 km/hr (10 mph), while estimated pressure difference of 6 m (20 ft) of air between wind impact pressure and wake region suction produces 15 kg/sec (33 lb/sec) of bypass flow through turbine  15  and duct  18 . Resulting duct area is only 3.6% of building frontal area, substantially less than the maximum calculated area of 30% in accordance with the parallel flow relationship. Additional wind for energizing the reserve system or storing energy for export from the building can be captured by increased turbine and duct area, and by taking advantage of above average wind energy which is proportional to the third power of wind speed.  
         [0035]      FIG. 2  illustrates a preferred embodiment of reserve system  20 . A reserve engine  21  with a gas turbine  22 , a compressor  23 , a combustor  24 , and a recuperator  25  receives air from a header  26  and fuel from a fuel pump  27  to drive a reserve generator  28  for providing power to controller  17 . Air to the header is controlled by a pumped air valve  29  and a compressed air valve  30 . An air liquefier  31  receives atmospheric air from a pressurizer  32  and discharges liquid air to a liquid air tank  33 . The liquid air is pressurized by a liquid air pump  34  and vaporizes while cooling atmospheric air in an evaporator  35 . Liquid air is transferred into tank  33  through a fill valve  36 , transferred from tank  33  through a drain valve  37 , and fuel is stored in a fuel tank  38 .  
         [0036]     Reserve system performance is evaluated to meet the 15 kWhr (20 hphr) per day demand for 4 days with no effective wind capture. During this period methanol consumption is 18 kg (39 lb) and liquefied air consumption is 95 kg (209 lb). The liquefied air imported to tank  33  minimizes compression work by cooling of intake air to compressor  24 , raising engine efficiency by over 300% as compared to a conventional inter-cooled and recuperated gas turbine. The need for imported liquefied air is reduced during periods of above average wind when liquefier  31  makes supplementary liquefied air, possibly including some for export. Liquefier operation during 6 hours of wind at 24 km/hr (15 mph) will provide enough liquefied air to meet daily demand. The quasi-isothermal pressurizer  32 , drawing power from controller  17 , provides inlet air to the liquefier. Liquefier performance is based on target work input of 1395 kj/kg (600 btu/lb) at 3 mPa (30 atm); approximately 200% of the ideal reversible work input of 714 kj/kg (307 btu/lb) of liquefied air produced. Engine output is 12000 kJ/kg (5200 btu/lb) of fuel with an air-fuel ratio of 16, and turbine inlet temperature is 1500 K (2700 R) at 3.0 mPa (30 atm). Methanol fuel is selected because it is renewable, oxygen content reduces liquefied air requirements, and production is enabled by low fuel demand in high efficiency gas turbines.  
         [0037]      FIG. 3  illustrates building  10  with two or more variable discharge systems  39  (typical) which receive air from duct  18  and discharge through plenum valves  40  to a wake regions  41  above an eaves plenum  42 . Plenum valve opening is adjusted by valve operators  43  under control of pressure sensors  44 .  
         [0038]     Capture of wind energy is increased for variable wind direction by discharge of air from wind drive  14  to selected wake regions of high suction by adjustment of the plenum valves. Drive  14  operates efficiently through a 90 degree variation of flow direction around corner  12 .  
         [0039]      FIG. 4  illustrates a solar photo-voltaic panel  45  for providing supplementary power to controller  17 .  
         [0040]     Energy capture system performance is evaluated for the representative building demand of 15 kWhr (20 hphr) per day with addition of 9 kWhr (12 hphr) per day by panel  45 . A 14 m2 (150 ft2) panel with average solar insolation of 11350 kJ/m2 (1000 Btu/ft2) and conversion efficiency of 20% enables production of an additional 23 kg (50 lb) of liquefied air by liquefier  31 , enough for 1 day of reserve engine  21  operation with no effective wind or solar capture.  
         [0041]     Although the description above contains many specifics, these should not be construed as limiting the scope of the invention, but only to provide illustrations of some of the preferred embodiments of this invention. For example: 
        The energy capture and reserve system of the present invention is applicable to houses and other structures using any suitable fuel, available heat source or working fluid;     Wind, solar insolation and liquefied gas can be used in any combination to enable mechanical or electrical drive of working fluid compressors, gas liquefiers or other components;     The reserve engine can have performance features such as quasi-isothermal expansion or reheating of working fluid;     The reserve engine can have emissions features such as separation of carbon dioxide from combustion products and support of combustion by oxygen enriched air;     The reserve engine can have combustion cooling by suitable fluids including water, liquid nitrogen and other liquefied gases; and     Wind capture can be enhanced in various ways including building orientation to the wind, fencing, arrangement of adjacent buildings and air discharge through one or more wind turbines to the wake of one or more roof or wall corners.        
 
         [0048]     Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than the examples given.