Building energy capture and reserve system

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

BACKGROUND OF THE INVENTION

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.

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:

(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.

(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.

(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.

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.

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.

(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.

(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.

(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.

(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

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.

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.

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.

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.

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:

(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.

(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.

(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.

The liquefied gas provides storage indirectly by reducing compression work in a reserve engine.

(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.

(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.

(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.

(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

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:

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.

FIG. 2 is a schematic illustration showing connection of components of a reserve engine system of the building of FIG. 1.

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.

FIG. 4 is a schematic illustration showing connection of a photo-voltaic panel for providing supplementary power to the building of FIG. 1.

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

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.

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.

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.

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.

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.

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.

FIG. 4 illustrates a solar photo-voltaic panel 45 for providing supplementary power to controller 17.

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.

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.

Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than the examples given.

Claims

1. An energy system of a building comprising energy converter means driven by wind induced air flow through input drive means of said converter means to selected wake regions of said building, due to differential pressure between wind stagnation pressure impacting said input drive means and wind suction pressure in said wake regions, for providing power to output drive means of said converter means, whereby said output drive means provides power to selected components of said building.

2. The components of claim 1 comprising electrical generator means for providing electrical power to said building.

3. The system of claim 1 comprising a reserve system for providing power to said components when power of said output drive means is insufficient, whereby power supplied by said reserve system is independent of power sources external to said building.

4. The reserve system of claim 3 including: a. a heat engine, b. liquid transfer and storage means for storing cryogenic liquid heat sink fluid imported from a source external to said building, and c. cryogenic gas heat exchanger means and compressor means using vaporizing heat sink fluid from said storage means to first cool and then compress atmospheric air working fluid for said engine, whereby least compression work to said compressor means is approached.

5. The engine of claim 4 including: a. heater means for heating the compressed working fluid of said engine, and b. expander means for expanding the compressed and heated working fluid of said engine, whereby output power of said expander means supplements output power of said converter means.

6. The heater means of claim 5 including fuel combustor means for increasing temperature of the working fluid of said engine, whereby the working fluid of said engine comprises combustion products of said combustor means.

7. The compressor means of claim 4 including mixer means for adding vaporized cryogenic liquid discharging from said heat exchanger means to working fluid discharging from said compressor means, whereby maximum thermal efficiency of said engine is approached.

8. The components of claim 3 further including: a. a liquefier for conversion of atmospheric air to liquefied air, and b. liquefied air transfer means for transfer of excess liquefied air from said energy system, whereby liquefied air made by said liquefier is used to approach least compression work of said components and excess liquefied air made by said liquefier is utilized.

9. The liquefier of claim 8 further including pressurizer means driven by said input drive means for pressurizing atmospheric intake air to said liquefier, whereby least input work to said liquefier is approached.

10. The input drive means of claim 1 including: a. variable exhaust ducting means for discharging exhaust air from said input drive means to selected wake regions of said building, and b. automatic control means for regulating the flow area of said ducting means, whereby exhaust air from said input drive means discharges to said wake regions of low pressure.

11. The energy system of claim 1 further including solar energy means for supplementing power output of said system.

12. A method for using energy dissipated by a building to drive selected components thereof comprising the steps of: a. driving a wind energy converter by wind induced air flow through input drive means of said converter to selected wake regions of said building, due to differential pressure between wind stagnation pressure impacting said input drive means and wind suction pressure in said wake regions, for providing power to output drive means of said converter, b. operating an engine of a reserve system when power to said output drive means is insufficient, and c. operating an energy storage system for storing energy due to excess power of said output drive means, whereby power supplied to said building approaches independence from external energy sources.

13. The method of claim 12 further including the steps of: a. importing liquefied air from a source external to said building to liquefied air storage means of said building for use as heat sink fluid of said engine, b. cooling atmospheric air drawn from around said building with heat sink fluid from said storage means in heat exchanger means for intake by cryogenic compressor means, and c. pressurizing cooled atmospheric air from said heat exchanger means in said compressor means driven by said engine for providing compression of working fluid of said engine, whereby least compression work of said engine is approached.

14. The method of claim 13 further including the step of mixing vaporized heat sink fluid from said heat exchanger means with compressed atmospheric air from said heat exchanger means for supplementing the working fluid of said engine, whereby maximum thermal efficiency of said engine is approached.

15. The method of claim 12 further including the steps of: a. producing liquefied air by gas liquefier means driven by said output drive means for use as heat sink fluid of said engine, and b. exporting excess liquefied air to storage external from said engine, whereby excess power of said output drive means is utilized.

16. The method of claim 15 further including the step of providing intake pressure to said liquefier with pressurizer means driven by said output drive means, whereby maximum utilization of excess power of said output drive means is approached.

17. The method of claim 12 further including the step of supplementing power output of said energy converter by solar energy means.

18. The method of claim 12 further including the step of controllably discharging air from said input drive means through variable exhaust ducting means to selected wake regions of said building, whereby exhaust air from said input drive means discharges to said wake regions of low pressure.

19. An energy system of a building comprising a wind energy recovery turbine driven by wind induced air flow, due to differential pressure between wind stagnation pressure impacting said turbine and wind suction pressure in selected low pressure wake regions of said building, for providing torque to an electric generator connected to said turbine, whereby said generator provides electrical energy to said building.