Abstract:
An HVAC system includes a fluid driven turbine configured to drive a centrifugal compressor and a permanent magnet motor/generator; a battery electrically connected to the permanent magnet motor/generator; and a controller for the battery and the motor/generator. The turbine, compressor and generator are coaxially positioned along a rotatable shaft. The controller is configured to cause the motor/generator to draw electrical power from the battery or to supply electrical power to the battery in order to rotate the shaft at an efficient speed. The motor/generator is configured to supply electrical power to charge the battery when driven by the turbine and is configured to drive the rotation of the compressor when supplied by electrical power from the battery.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
       [0001]    This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/064,512, filed Mar. 10, 2008. The foregoing provisional application is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    HVAC systems typically include a refrigerant that circulates through a series of components in a closed system to maintain a cold region (e.g., a region with a temperature below the temperature of the surroundings). One exemplary refrigeration system is a vapor refrigeration system including a compressor. 
         [0003]    Solar thermal energy is a technology that uses solar energy to produce heat. The heat collected with a solar thermal device may be used to generate power such as with a turbine. Solar thermal collectors are desirable because they are generally much more efficient than photovoltaic devices, which convert sunlight directly to electricity. However, solar thermal devices must include a storage device if continuous power is desired because they lose effectiveness during periods of low sunlight (e.g., at night or during excessive cloud cover). 
         [0004]    Additionally, HVAC systems are known to be integrated in vehicles. U.S. patent application Ser. No. 12/320,213, filed Jan. 21, 2009, and incorporated herein by reference in its entirety, discloses an HVAC system installable in a vehicle and having a module connected to vehicle&#39;s existing power system. It would be useful for an HVAC system installed in a vehicle to be at least partially powered by the waste heat of the vehicle and to store excess energy from this heat source in a stored energy device, such as a battery, which may also power some components of the HVAC system. It would be useful for the HVAC system to be powered by the heat source and stored energy device such that the HVAC components and system operate efficiently. 
       SUMMARY 
       [0005]    One disclosed embodiment relates to an HVAC system comprising a fluid driven turbine configured to drive a centrifugal compressor and a permanent magnet motor/generator; a battery electrically connected to the permanent magnet motor/generator; and a controller for the battery and the motor/generator. The turbine, compressor and generator are coaxially positioned along a rotatable shaft. The controller is configured to cause the motor/generator to draw electrical power from the battery or to supply electrical power to the battery in order to rotate the shaft at an efficient speed. The motor/generator is configured to supply electrical power to charge the battery when driven by the turbine and is configured to drive the rotation of the compressor when supplied by electrical power from the battery. 
         [0006]    Another embodiment of the invention relates to an HVAC system for a vehicle utilizing a heat exchanger configured to receive heat from a vehicle component, wherein the heat exchanger exchanges heat with a fluid. The HVAC system further comprises a fluid driven turbine configured to drive a centrifugal compressor and a permanent magnet motor/generator; a battery electrically connected to the permanent magnet motor/generator; and a controller for the battery and the motor/generator. The turbine, compressor and generator are coaxially positioned along a rotatable shaft. The controller is configured to cause the motor/generator to draw electrical power from the battery or to supply electrical power to the battery in order to rotate the shaft at an efficient speed. The motor/generator is configured to supply electrical power to charge the battery when driven by the turbine and is configured to drive the rotation of the compressor when supplied by electrical power from the battery. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0007]      FIG. 1  is a block diagram of a solar-powered HVAC system according to an exemplary embodiment. 
           [0008]      FIG. 2  is a more detailed block diagram of a solar-powered HVAC system according to an exemplary embodiment. 
           [0009]      FIG. 3  is a graph showing one exemplary embodiment of the power produced by a first cycle and the power required by a second cycle over one day. 
           [0010]      FIG. 4  is a block diagram of an HVAC system according to another exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION  
       [0011]    Referring to  FIG. 1 , a block diagram of a heating, venting, and air conditioning (HVAC) system according to an exemplary embodiment is shown. The HVAC system generally includes a first cycle  100  and a second cycle  200 . At least one component of the first cycle  100  is coupled to a component of the second cycle  200 . The components are further coupled to an electric motor/generator  310 . 
         [0012]    The first cycle  100  converts thermal energy from a heat source and converts it into work. As shown according to one exemplary embodiment in  FIG. 2 , the first cycle  100  is a Rankine cycle such as is commonly used in power generation plants. The first cycle  100  includes a solar collector  110  that gathers energy form sunlight to boil a fluid such as water or another suitable coolant such as fluorinol 50, fluorinol 85, or isopentane. According to various exemplary embodiments, the solar collector  110  may be a thermosyphon, a glass tube collector, a flat plate collector, or any other suitable collector. The collector  110  may be concentrated (e.g., include lenses or mirrors to concentrate sunlight) or may be non-concentrated. The collector  110  may be active (e.g., configured to move to follow the sun and collect the maximum amount of solar energy) or may be passive. The collector  110  is configured to heat the fluid to a high-temperature vapor. 
         [0013]    The vapor is then allowed to expand through a turbine  130 , generating power as it loses temperature and pressure. As shown in  FIG. 2 , the turbine  130  is a steam turbine well known to those of ordinary skill in the art. The fluid is then converted to a liquid in a condenser  140  before re-entering the solar collector  110 . Condensers are frequently used in Rankine cycle operations, such as power plants, and are well known to those of ordinary skill in the art. As shown according to one exemplary embodiment, the first cycle may include a reservoir  150  for storing the liquid. The reservoir  150  is in fluid communication with both the condenser  140  and the solar collector  110 . The first cycle  100  may be passive or may be an active system and include a pump (not shown) for moving the fluid through the first cycle  100 . The first cycle  100  may further include a valve  120  that is configured to halt the flow of fluid through the turbine  130 , as will be described in greater detail below. 
         [0014]    The second cycle  200  is a refrigeration cycle that is configured to maintain a cold region (e.g., a region with a temperature below the temperature of the surroundings). As shown according to one exemplary embodiment in  FIG. 2 , the second cycle  200  is a vapor-compression refrigeration cycle. The second cycle  200  includes a compressor  210  that is mechanically coupled to the turbine  130  of the first cycle  100  with a shaft  400  and is driven by the turbine  130 . The compressor  210  is preferably a centrifugal compressor, which is optimal for refrigeration and air conditioning systems. The compressor  210  compresses a vaporized fluid such as water or another suitable coolant such as fluorinol 50, fluorinol 85, or isopentane and causes it to become superheated. The fluid is then cooled in a condenser  230  before passing through a metering device  240 . The metering device  240  is included to regulate the flow of the fluid into an evaporator  250 . One example of a metering device is shown in FIGS. 1-3 of U.S. patent application Ser. No. 11/808,469, filed Jun. 11, 2007 (incorporated herein by reference in its entirety). After passing through the metering device  240 , the fluid goes through the evaporator  250  where it absorbs heat from a region (e.g., the interior of a building) to cool the region before returning to the compressor  210 . 
         [0015]    The turbine  130  and the compressor  210  each have efficiencies that may depend on the speed at which they are run. Further, as shown best in  FIG. 3 , the first cycle  100  may produce more power than required by the second cycle  200  (e.g., when the sun is highest in the sky) or may not be able to produce enough power for the second cycle  200  (e.g., when it is cloudy, late in the day, early in the day, etc.). In some situations, the first cycle  100  may not produce any power at all (e.g., at night). The available solar energy to drive the first cycle  100  and the cooling load required for the second cycle  200  both generally peak during the day and reach a minimum at night, however, insulation and other factors offset the cooling load so the maximum cooling load typically occurs sometime in the afternoon and the minimum cooling load occurs sometime in the morning. To monitor and regulate the performance of the first and second cycles  100  and  200 , an electrical system  300  may be coupled to first cycle  100  and the second cycle  200 . 
         [0016]    Referring to  FIG. 2 , the electrical system  300  includes an electric motor/generator  310 , a controller  320 , and an energy storage device such as a battery  330 . An electrical system with similar components, such as a motor/generator, is shown in FIG. 10 of U.S. patent application Ser. No. 12/320,213, already incorporated herein by reference in its entirety. According to one exemplary embodiment, a motor/generator  310  of the electrical system  300  may be coaxially positioned on a rotatable shaft  400  to the turbine  130  and the compressor  210 . The electric motor/generator  310  may be a permanent magnet brushless DC motor/generator coupled to the battery  330  with a controller  320 . The shaft  400  can be one manufactured part or can include discrete sections connected together. The turbine  130  may be configured to be able to provide power to both the compressor  210  and the motor/generator  310  through the shaft  400 . The rotary motion created by the turbine  130  is translated by the rotatable shaft  400  to the compressor  210  to drive the operation of the compressor  210 , and is translated by the rotatable shaft  400  to the motor/generator  310  to drive the generation of electrical energy. 
         [0017]    In one mode, the battery  330  stores electricity produced by the motor/generator  310 . For instance, when the sun is highest in the sky, the solar collector  110  will collect solar energy at a maximum rate, causing the turbine  130  to produce more power. Power generated by the turbine  130  that is not used by the compressor  210  to drive the second cycle  200  will drive the motor/generator  310  and be converted to electricity to be stored in the battery  330 . 
         [0018]    In another mode, the battery  330  provides power to turn the motor/generator  310  and, in turn, the compressor  210 . For instance, at night, when the first cycle  100  is producing no power, the battery  330  discharges to turn the motor/generator  310  and the compressor  210  through the shaft  400 . When the battery  330  is providing power, a valve  120  in the first cycle  100  may be turned off to effectively uncouple the turbine  130  from the first system  100  and reduce wasted power. The battery  330  may further provide electrical power to other components of the HVAC system. For example, if the solar collector  110  is an active system, the battery  330  may provide electrical power to adjust the solar collector  110 . 
         [0019]    The controller  320  regulates the flow of power to and from the battery  330  through the motor/generator  310 . The controller  320  can be configured to determine the efficient speed of the rotatable shaft  400  based on a combined efficiency of the compressor  210  and the turbine  130 . The efficient speed of the turbine  130  or the compressor  210  may be based on pressure differentials across each rotating component of the turbine  130  or compressor  210 . The controller  320  controls when the motor/generator  310  draws only a portion of the power from the turbine  130  or when the motor/generator  310  provides only a portion of the power from the battery  330  to the compressor  210 . For example, if the solar collector  110  does not provide enough energy for the turbine  130  or compressor  210  to operate efficiently, the controller can control the motor/generator  310  so that it may provide enough power from the battery  330  to rotate the shaft  400  at an efficient speed. Thus, the controller  320  can maximize the efficiency of the turbine  130  and/or compressor  210 . 
         [0020]    According to another exemplary embodiment, an HVAC system similar to the one described above may be used elsewhere, such as a vehicle. As shown in  FIG. 4 , the first cycle  100  may collect energy from another source  500 , such as waste heat from the vehicle&#39;s internal combustion engine. Alternatively, the heat source  500  may be the engineer block or other component of the internal combustion engine. Heat exchanger  510  may be constructed in a manner similar to conventional well known examples of heat exchangers utilizing the heat from the engine or engine exhaust to heat a fluid. Examples of such heat exchangers are disclosed in U.S. Pat. Nos. 4,003,344 and 7,013,644, both of which are incorporated by reference herein in their entireties.