ENERGY EFFICIENT BUILDING

FIELD OF THE INVENTION

[0001] The present invention generally relates to building energy systems, and more particularly to controlling ventilation and temperature and generating power in buildings using the stack effect. BACKGROUND OF THE INVENTION

[0002] Conventional building designs rely on powered building-mechanical systems to bring ventilation into habitable spaces from the outside of the building. These conventional designs typically include powered louvers positioned on the outer surfaces of the building that open to allow air to enter the habitable spaces for ventilation, heating, and cooling. Typically, powered fans draw the outside air through the louvers and into the habitable spaces, and then expel the air from the habitable spaces to the outside of the building. This conventional approach requires large energy consumption to drive the louvers and power the fans. A need exists for improved energy efficiency in buildings. SUMMARY OF THE INVENTION

[0003] Methods and systems consistent with the present invention improve building energy efficiency. A solar engine, which is vertically aligned along an interior portion of a building, is heated by solar radiation. The solar engine includes a warm air chamber at an upper portion of the solar engine and a hollow core or void positioned below the warm air chamber. Habitable spaces are positioned around the outside of the core toward an exterior of the building. Solar radiation on the warm air chamber creates a high temperature zone in the warm air chamber. This creates a stack effect in which air rises through the core due to the lower temperatures in the core, and results in a negative pressure in the core. Air enters at a lower portion of the building and is pulled through the core by the solar engine. If the windows on the outside of the habitable spaces are opened, the negative pressure in the core causes passive cross ventilation from the outside of the building through the habitable spaces and into the core, where the air rises to the warm air chamber and then out of the building. This allows the habitable spaces to be naturally cooled and ventilated with no energy costs.

[0004] The habitable spaces may also be ventilated by drawing air out from the core and into the habitable spaces. In this case, mechanical units in the habitable spaces draw

air, which is moving upward through the core, into the habitable spaces. The air from the core ventilates the habitable spaces and is expelled to the exterior of the building. Habitable spaces in a lower portion of the building may generate high internal loads and may require cooling in the interior zones. As air passes through the core along the interior surfaces of the habitable spaces it is preheated by energy transfer with the surrounding conditioned space. The preconditioning of the air by drawing it through the core as opposed to the exterior of the building saves considerable heating energy. Further, air from the core provides more consistent ventilation compared to air brought in through louvers located outside the building, which are susceptible to changing wind conditions and often cannot pull in air since the suction forces of the wind may outweigh the external static pressure of the louver fan.

[0005] The stack effect may be enhanced by providing one or more solar reflectors in the warm air chamber. Solar radiation reflects from the solar reflector down into the warm air chamber and core. The solar radiation may be directed farther down into the core through the use of additional reflector or reflective surfaces within the core. The introduction of solar energy into the core further heats the air in the core, resulting in a higher air velocity through the solar engine and enhancing the stack effect. The introduction of light into the core may also beneficially illuminate the interior portions of the habitable spaces located around the core. This allows for reduced energy consumption for illuminating the habitable spaces.

[0006] Further, one or more wind turbines positioned in the solar engine may be used to convert the wind energy of the air moving upward through the solar engine into electricity to power the building. Thus, methods and systems consistent with the present invention reduce the amount of energy required to ventilate a building and also generate electricity that may be used to power the building.

[0007] In accordance with systems consistent with the present invention, a building ventilation system is provided. The building ventilation comprises: a warm air chamber located in an upper portion of a building, the warm air chamber having a warm air chamber inlet at a bottom portion of the warm air chamber and a warm air chamber outlet at a top portion of the warm air chamber, at least a portion of the top of the warm air chamber comprising a transparent material, air in the warm air chamber being heated by solar radiation radiating on the air via the transparent material; and

a hollow core extending vertically down from the warm air chamber inlet along an interior portion of the building, at least a portion of a side wall of the core being defined by an interior wall of a habitable space, the core having a first core opening coupled to an outside air duct that extends to an outer portion of the building and having a second core opening coupled to the habitable space via the interior wall of the habitable space, the air in the core being a lower temperature than the air in the warm air chamber and therefore the air in the core rising toward and through the warm air chamber inlet creating a negative pressure in the core relative to a pressure outside the building and effecting a suction of outside air from outside the building through the outside air duct and into the core, the air from the core that rises into the warm air chamber mixing with the air in the warm air chamber and at least a portion of the mixed air exiting the warm air chamber through the warm air chamber outlet.

[0008] In accordance with methods consistent with the present invention, a method for ventilating a building is provided. The method comprises the steps of: heating air in a warm air chamber, which is located in an upper portion of a building, using solar radiation that radiates through a transparent top of the warm air chamber, the warm air chamber having a warm air chamber inlet at a bottom portion of the warm air chamber and a warm air chamber outlet at a top portion of the warm air chamber, a hollow core extending vertically down from the warm air chamber inlet along an interior portion of the building, at least a portion of a side wall of the core being defined by an interior wall of a habitable space, the core having a first core opening and a second core opening that is coupled to the habitable space via the interior wall of the habitable space; and providing an outside air duct having a first end that extends to an outer portion of the building and a second end that is coupled to the first core opening, the air in the core being a lower temperature than the air in the warm air chamber and therefore the air in the core rising toward and through the warm air chamber inlet creating a negative pressure in the core relative to a pressure outside the building and effecting a suction of outside air from outside the building through the outside air duct and into the core. [0009] Other systems, methods, features, and advantages of the invention will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[00010] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an implementation of the invention and, together with the description, serve to explain the advantages and principles of the invention. In the drawings,

[00011] Figure 1 is a cross-sectional view of a building consistent with the present invention;

[00012] Figure 2 is a top cross-sectional view of the core;

[00013] Figure 3 is a functional cross-sectional view of the building showing air flow through the solar engine using the stack effect;

[00014] Figure 4 is a cross-sectional side view of a conventional habitable space;

[00015] Figure 5 is a cross-sectional side view of a habitable space consistent with the present invention;

[00016] Figure 6 is a cross-sectional view of the building with a reflector;

[00017] Figure 7 is a cross-sectional view of the building with an alternative reflector;

[00018] Figure 8 is a cross-sectional view of the building with wind turbines at the top of the core; and

[00019] Figure 9 is a cross-sectional top view of the core with wind turbines around the top of the core.

DETAILED DESCRIPTION

[00020] Reference will now be made in detail to an implementation consistent with the present invention as illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same or like parts.

[00021] Methods and systems consistent with the present invention improve building energy efficiency. Figure 1 is a vertical cross-sectional view of an illustrative building 100 consistent with the present invention. The illustrative building comprises a plurality of floors 1-n of habitable spaces 102 in a lower portion of the building and a crown 104 at an upper portion of the building. The habitable spaces 102 are positioned around an exterior portion of the building. The interior walls 106 of the habitable spaces 102 form the outer boundary of a core 108 or open space at an interior portion of the building. In the

illustrative example, the core is an atrium that extends the height of the habitable spaces. Although the core is shown in the illustrative example as extending along the entire height of the habitable spaces, the core may alternatively stop short of the lower floors. [00022] Referring to Figure 2, the illustrative building 100 has a circular cross section. However, the building is not limited to this configuration. The building may alternatively have another cross-sectional shape, such as square, rectangular, and the like, and may have different cross-sectional shapes at various points along the height of the building. Further, although the illustrative core 108 has a circular cross section and is located at the center of the illustrative building, the core may have a cross-section of any shape or position within the building.

[00023] Conventional building designs rely on powered building-mechanical systems to bring ventilation into habitable spaces from the outside of the building. These conventional designs typically include powered louvers positioned on the outer surfaces of the building that open to allow air to enter the habitable spaces for ventilation, heating, and cooling. Typically, powered fans draw the outside air through the louvers and into the habitable spaces, and then expel the air from the habitable spaces to the outside of the building. This conventional approach requires large energy consumption to drive the louvers and power the fans. Methods and systems consistent with the present invention reduce energy consumption by providing a solar engine within the building that effects natural ventilation through the habitable spaces.

[00024] Referring to Figure 3, the connected spaces of the crown 104 and the core

108 form a solar engine 302. The illustrative solar engine is depicted in solid lines. In the illustrative example, the crown has a width that is greater than the width of the core. Thus, air enters the crown from the core through a via at the base of the crown. At least a portion of a roof 304 of the crown comprises transparent material, such as glass, plastic, and the like. Solar radiation 306 heats the roof of the crown and enters the crown through the transparent material, which heats the air within the crown, forming a high temperature zone relative to the core. Thus, the crown is referred to herein as a warm air chamber 308. [00025] The air in the warm air chamber 308 is warmer than the air in the core.

Further, the air in an upper portion of the core is warmer than air in a lower portion of the core due to solar radiation illuminating the air in the upper portion of the core. This causes the air to rise toward the top of the core and into the warm air chamber, creating a negative pressure in the core. This negative pressure in the core results in a stack effect in which air

310 from outside the building is suctioned through ventilation shafts and may be suctioned through windows, through the habitable spaces, into the core. As long as the air in the core is warmer than the outside air, the stack effect is maintained.

[00026] The outside air enters the building through outer ventilation openings 312 and may also enter the building through open windows 314 in the habitable spaces 102. The negative pressure in the core draws the outside air through the outer ventilation openings 312 and then through inner ventilation openings 316 into the core. The negative pressure may also draw outside air through one or more windows 314 and then through inner ventilation openings 316 into the core. The inner ventilation openings may be, for example, interior window openings, vias, ventilation shaft openings, voids in walls, doorways, and the like. One having skill in the art will appreciate that the windows can be any suitable opening, such as but not limited to exterior window openings, vias, ventilation shaft openings, voids in an exterior wall, doorways, and the like. In the illustrative embodiment, the windows are closable, however, they may alternatively be permanently open. Air enters at a lower portion of the building and is pulled up through the core by the negative pressure in the core. Warm air is expelled from the crown via one or more exhaust openings 318 in the crown. The exhaust openings may be located in an exterior side wall of the crown, in the roof of the crown, or both.

[00027] In the illustrative example, the outer ventilation openings 312, inner ventilation openings 316, windows 314, and exhaust openings 318 may be any size suitable for effecting air flow from the outside of the building into the core. The outer ventilation openings 312, inner ventilation openings 316, windows 314, and exhaust openings 318 may have a height and width greater than 0 m. In an experiment, when the outer ventilation openings 312 are 6.0 m high and the exhaust openings are 3.0 m wide, the average wind speed at the top of the core is 7.0 m/s in the transitional season and 7.5 m/s in the winter season. During the transitional season, the ambient air was 17 ⁰ C, the building external surface was 20 ⁰ C, the core surface was 27 ⁰ C, the crown internal surface was 45 ⁰ C, and the building rooftop was 40 ⁰ C. It was found that the air inside the core averaged between 18 ⁰ C and 20 ⁰ C, which was 1 to 3 ⁰ C warmer than the outside air temperature. The air temperature in the building crown was an even higher temperature, from 20 to 23 ⁰ C or higher than the ambient air temperature. During the winter season, the ambient air was 1 ⁰ C, the building external surface was 5 ⁰ C, the core surface was 14 ⁰ C, the crown internal surface was 25 ⁰ C, and the building rooftop was 20 ⁰ C. As air moved up the core, it was

found that the air temperature in the core increased by more than 2 ⁰ C when it reached the top of the core. After the air enters the warm air chamber, the temperature was further increased by another 1 to 2 ⁰ C. During the winter season, outside air was suctioned into the outer ventilation openings 312 at a speed of around 3.5 m/s. As the air was warmed up by the core wall surface it flowed upward toward the top of the core and entered the warm air chamber with a peak velocity of 9.0 m/s.

[00028] Through experimentation and modeling, the inventors have discovered that the air temperature in the crown can be increased when certain materials are used in the external walls of the crown. For example, in an experiment, when the crown walls were normal double panel glazing, the outer panel had a reflectance of 0.08 and an absorptance of 0.16, and the inner panel had a reflectance of 0.08 and an absorptance of 0.16. When absorptive inner panel glazing was used, the outer panel had a reflectance of 0.08 and an absorptance of 0.16, and the inner panel had a reflectance of 0.08 and an absorptance of 0.41. When the absorptive inner panel glazing had a low-e coating (such as a low-e value of 0.20), the outer panel had a reflectance of 0.08 and an absorptance of 0.16, and the inner panel had a reflectance of 0.08 and an absorptance of 0.41.

[00029] In the experiment, it was discovered that the normal double panel glazing had a surface temperature of around 36 ⁰ C during peak sunlight hours, the absorptive inner panel glazing had a surface temperature of around 43 ⁰ C during peak sunlight hours, and the absorptive inner panel glazing with a low-e coating had a surface temperature of around 44 ⁰ C. Thus, absorptive internal panel glazing at the crown with a low-e coating provided increased temperatures in the crown.

[00030] Further, the temperature within the crown may be further increased by providing internal surfaces in the crown that have a dark color, such as black. In an experiment, it was discovered that when normal double panel glazing was used on the crown and when an internal vertical black cylinder was located at a central portion of the crown, the outer panel had a reflectance of 0.08 and an absorptance of 0.16 and a surface emissivity of 0.90; the inner panel had a reflectance of 0.08 and an absorptance of 0.16 and a surface emissivity of 0.90; and the inner cylinder surface had a reflectance of 0.10 and an absorptance of 0.90 and a surface emissivity of 0.90. In this experiment, the normal double panel glazing had a surface temperature of around 36 ⁰ C during peak sunlight hours and the internal black cylinder had a surface temperature of around 42 ⁰ C.

[00031] When absorptive internal panel glazing was used with an internal black cylinder in the core, the outer panel had a reflectance of 0.08 and an absorptance of 0.16 and a surface emissivity of 0.90; the inner panel had a reflectance of 0.08 and an absorptance of 0.41 and a surface emissivity of 0.90; and the inner cylinder surface had a reflectance of 0.10 and an absorptance of 0.90 and a surface emissivity of 0.90. In this experiment, the absorptive internal panel glazing had a surface temperature of around 40 ⁰ C during peak sunlight hours and the internal black cylinder had a surface temperature of around 42 ⁰ C. [00032] Thus, absorptive internal panel glazing, particularly with a low-e coating, and one or more internal black surfaces, such as internal cylinders, in the crown provide greater air temperatures within the warm air chamber, which enhances the stack effect and air movement through the core.

[00033] In the illustrative example, at least a portion of the interior walls 106 of the habitable spaces comprise a reflective surface on their side that faces the core. Thus, solar radiation that enters the core is reflected off the reflective surface and downward toward a lower portion of the core. This enhances the stack effect by heating the air in the lower portion of the core. The reflective surface may comprise any suitable material that reflects solar radiation, such as but not limited to at least one of glass, plastic, metal, a painted surface, and the like.

[00034] Figure 4 is a cross-sectional view of a conventional habitable space 402. In accordance with conventional ventilation practices, ventilation and comfort control is provided to the conventional habitable space 402 through the use of a circulation fan 404, a mechanical ventilation system 406, or floor heating system 412. The mechanical ventilation system 406 includes air ducts that couple to a powered heating, ventilation, and air conditioning unit (not pictured). A person in the conventional habitable space 402 turns on the circulation fan 404 or the mechanical ventilation system 406 using a control actuator 410, such as a wall switch or thermostat operator. When the circulation fan 404 or mechanical ventilation system 406 turns on, the room air is circulated. The mechanical ventilation system 406 may also provide heated or conditioned air to the room. The heating system 412 in the floor 414 may also be turned on to heat the room. Thus, the conventional habitable space 402 requires energy to be consumed to operate the circulation fan 404, mechanical ventilation system 406, and floor heating system 412 in order to ventilate, heat, and cool the room. Outside air may enter the conventional habitable space 402 through a window 408. However, unlike methods and systems consistent with the present invention,

air is not introduced into or extracted from the conventional habitable space 402 using a solar engine.

[00035] In accordance with methods and systems consistent with the present invention, the stack effect induced in the core beneficially provides natural ventilation through the habitable spaces. This allows the habitable space to be naturally ventilated, cooled, and heated with reduced or no energy costs. Figure 5 is a cross-sectional view of an illustrative habitable space 102 consistent with the present invention. The habitable space 102 includes a window 314 located at an exterior side of the building and an inner ventilation opening 316 that forms a via into the core. When the window 314 on the outside of the habitable space is opened, the negative pressure in the core causes passive cross ventilation of air 310 from the outside of the building through the habitable space and into the core, where the air rises to the warm air chamber and then out of the building. This allows the habitable space to be naturally cooled and ventilated with no energy costs. [00036] The ventilation and comfort controls in the habitable space 102 may be supplemented, for example, by a circulation fan 502, mechanical ventilation system 504, and floor heating system 506 located under a floor 508. Alternative or additional ventilation and comfort control systems may be used. For example, a person in the habitable space 102 may use a control operator 510 to turn on at least one of the circulation fan 502 or the mechanical ventilation system 504 to further cool the air in the room. Alternatively, the person may use the control operator 510 to turn on at least one of the floor heating system 506 or mechanical ventilation system 504 to heat the room. In the illustrative example, the control actuator operator is, for example, a wall switch, thermostat, or the like, that is mechanically or electrically coupled to a control system that can operate at least one of the circulation fan 502, mechanical ventilation system 504, and the floor heating system 506. [00037] The control operator 510 may also actuate an exhaust fan 512, as well as vents 514 and 516 in the window 314 and inner ventilation opening 316, respectively. In an illustrative example, the control operator 510 may turn off the circulation fan 502, mechanical ventilation system 504, and floor heating system 506; turn on exhaust fan 512; and open vents 514 and 516. This allows natural ventilation to be drawn through the room by the solar engine, with the exhaust fan 512 assisting with drawing air into the core 108. In this case, only the exhaust fan 512 is consuming energy, while the room is being cross ventilated and heated cooled by outside air. Alternatively, the exhaust fan 512 may be

turned off, allowing the room to be cooled and ventilated using only the suction force of the solar engine and no energy consumption.

[00038] In an embodiment, a pressure sensor 518 may monitor room pressure or take a differential pressure between the room and the core. If the room pressure drops to a level below a predetermined threshold or below the pressure in the core, then the pressure sensor may signal the mechanical ventilation system 504 to turn on to force air into the room. This creates a positive pressure relative to the core and assists with the stack effect. Alternatively, the mechanical ventilation system 504 may vary its speed up or down to maintain a particular pressure in the room that is greater than the pressure in the core. [00039] The habitable space 102 may also be ventilated by drawing air out from the core, through the inner ventilation opening 316, and into the habitable space. This may be done for example during the winter season, when the exterior building facade may be closed. In this case, at least one of the exhaust fan 512 or mechanical ventilation unit 504 may draw air, which is moving upward through the core, into the habitable space. The air from the core ventilates the habitable space and is expelled to the exterior of the building or to the mechanical ventilation system.

[00040] Habitable space in a lower portion of the building may generate high internal loads and may require cooling in the interior zones. As air passes through the core along the interior surfaces of the habitable spaces it is preheated by energy transfer with the surrounding conditioned space. The preconditioning of the air by drawing it through the core as opposed to the exterior of the building saves considerable heating energy. Further, air from the core provides more consistent ventilation compared to air brought in through louvers located outside the building, which are susceptible to changing wind conditions and often cannot pull in air since the suction forces of the wind may outweigh the external static pressure of the louver fan.

[00041] Referring to Figure 6, the stack effect may be enhanced by providing one or more solar reflectors 602 at the crown of the building. Solar radiation reflects off surfaces of the crown onto the solar reflector, which directs the solar radiation into the core. Thus, solar radiation that may reflect off the crown in a direction that would not normally allow the solar radiation to enter the core is directed into the core by reflecting off the solar reflector. Thus, the solar reflector in combination with the reflective surfaces of the crown form a heliostatic system that directs solar radiation into the core.

[00042] The solar reflector 602 has a reflective surface 604 comprising one or more reflective materials, such as one or more mirrors, glass, metal, and the like. In the illustrative example shown in Figure 6, the reflective surface 604 has a generally parabolic shape and comprises a plurality of mirror sections that fit together to form the reflective surface. The reflective surface may have alternative shapes or orientations, such as the orientation shown in Figure 7, and the like. The solar reflector's reflective surface may be chosen to provide a particular reflective angle. For example, a solar reflector that has a reflective surface with greater angle may direct solar radiation farther down into the core. This is shown in the illustrative example of Figure 7, in which the solar reflector 702 has a reflective surface 704 that directs solar radiation farther down into the core than the illustrative solar reflector of Figure 6.

[00043] The surfaces of the crown may be treated with one or more reflective materials, such as one or more mirrors, glass, metal, and the like. Further one or more surfaces of the crown may be adjustable, either manually or automatically using a control system, to adjust the angle of the surface of the crown to allow more light to reflect onto the solar reflector.

[00044] Solar radiation reflects from the solar reflector down into the warm air chamber and core. The solar radiation may be directed farther down into the core through the use of one or more additional reflectors or reflective surfaces within the core. For example, one or more walls of the habitable chambers 102 that face the core may have windows or mirrored surfaces that reflect light down into the core. In another illustrative example, at least a portion of the walls of the core may be painted a reflective color, such as white, silver, or gold, to reflect light down into the core. The introduction of solar energy into the core further heats the air in the core, resulting in a higher air velocity through the solar engine, thereby enhancing the stack effect.

[00045] The introduction of light into the core also beneficially illuminates the interior portions of the habitable spaces located around the core. For example, one or more of the habitable spaces may have windows or open vias adjacent the core that let light into the habitable spaces. This allows for reduced energy consumption for illuminating the habitable spaces.

[00046] As air rises toward the top of the core, it mixes with warmer air and increases velocity. As shown in Figure 8, wind turbines 802 positioned around the top exit of the core rotate within this moving air, driving generators that convert the mechanical turning

energy into electricity. In the illustrative example, the wind turbines are manufactured by Windside of Finland. However, alternative wind turbines may be used. [00047] In the illustrative example, the wind turbines are horizontally disposed and coupled at a first end to a side wall at the top edge of the core and coupled at an opposite end to a ceiling 804 positioned at the top of the core. The ceiling 804 is at least partially transparent or has one or more vias therethrough to allow solar radiation to pass through the ceiling into the core. In the illustrative example, the ceiling comprises supported glass plates that allow sunlight to pass into the core.

[00048] Each wind turbine comprises blades that are rotatable about its horizontal axis. When warm air passes over the wind turbine's blades, the wind turbine rotates about its horizontal axis. The wind turbine has an axle that is mechanically coupled to a generator 806. As the wind turbine rotates, its axle rotates and, in turn, causes the generator to convert the axle's mechanical energy into electricity.

[00049] Figure 9 shows a top view looking down onto a plurality of illustrative wind turbines 802 that are positioned around the top of the core 108. As depicted, each wind turbine is coupled at a first end to a generator 806 mounted near a side wall at the top edge of the core and coupled at an opposite end to the ceiling 804. The illustrative ceiling 804 is substantially solid. Therefore, as air rises up through the core, it is forced to pass through the space between the core side wall 106 and the ceiling 804. Accordingly, at least some of the air moves across one or more of the wind turbines, causing the wind turbines to rotate and generate electricity at the generators. The generated electricity may be used as a power source for the building. Thus, methods and systems consistent with the present invention reduce the amount of energy required to ventilate a building and also generate electricity that may be used to power the building.

[00050] The foregoing description of an implementation of the invention has been presented for purposes of illustration and description. It is not exhaustive and does not limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practicing the invention. For example, the described implementation includes software but the present implementation may be implemented as a combination of hardware and software or hardware alone. The invention may be implemented with both object-oriented and non-object-oriented programming systems. The scope of the invention is defined by the claims and their equivalents.