Abstract:
An apparatus for providing air-conditioning to a vehicle is disclosed. The apparatus includes a solar photovoltaic panel positioned in a window or windshield to provide direct current to power a thermoelectric assembly to pump excess heat out of the interior of the car. The car is air-conditioned in a parked state and pre-air-conditioned before use.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Ser. No. 61/028,063 filed Feb. 12, 2008, which application is fully incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to thermoelectric cooling, and more particularly to a system and its methods of use for cooling an interior of a vehicle by using a thermoelectric cooling assembly powered a solar photo-voltaic panel. 
     2. Description of the Related Art 
     Interior compartments of stationary vehicles tend to get enormously hot particularly during sunny, daylight periods of the day. On a warm sunny day, for example, a vehicle&#39;s windows collect light, trapping heat inside the vehicle and pushing the temperature inside to dangerous levels (100-130° F.). Such temperature increases can occur in a car even if the windows are opened slightly. An extremely hot interior of a vehicle poses a danger to pets, electronics and heat-sensitive items, such as medications, left in the vehicle, such as a car. An extremely hot stationary vehicle interior increases the cooling load on the vehicle air-conditioning unit when the vehicle is operated. 
     An existing method in cars to passively prevent this heating problem involves aluminum-coated reflectors mounted on the windshields of the parked cars which reflect the sun&#39;s incoming radiation. This technique is not effective because these reflectors are not so efficient in preventing the sun&#39;s radiation from entering the car and eventually the temperature inside the car becomes undesirable. 
     A thermoelectric cooler (TEC), also known as a thermoelectric module or Peltier cooler, is a semiconductor-based electronic component that functions as a small heat pump. By applying a low voltage DC power source to a TEC, heat will be moved through the thermoelectric material from one side to the other. One cooler face, the cold side, therefore is cooled while the opposite face, the hot side, is simultaneously heated. 
       FIG. 1  is a diagram of a practical TEC  101  comprising two or more elements of p-type and n-type semiconductor material P and N that are connected electrically in series and thermally in parallel. The semiconductor material is generally bismuth telluride. The elements of semiconductor material P and N are biased by a low DC voltage provided by a DC power source  102 . These thermoelectric elements and their electrical interconnects typically are mounted between two ceramic substrates  103  and  104 . One ceramic substrate is the cold side  103  removing heat from an object being cooled  105 . The object being cooled  105  may, in turn, be used to remove heat from another object or air. A heat sink  106  must remove from the other ceramic substrate, the hot side  104 . In turn, heat must be removed from the heat sink  106 . The heat sink may have fins fabricated into to enhance the exchange of heat between it and air and/or water. Placing TEC&#39;s on top of one another in stages to form a multi-stage thermoelectric module increases cooling performance. 
     Like mechanical refrigerators, TEC&#39;s are governed by the same fundamental laws of thermodynamics. In a mechanical refrigeration unit, a compressor raises the pressure of a liquid and circulates the refrigerant through the system. In the evaporator or “freezer” area, the refrigerant boils and in the process of changing to a vapor, the refrigerant absorbs heat causing the freezer to become cold. The heat absorbed in the freezer area is moved to the condenser where it is transferred to the environment from the condensing refrigerant. 
     In a thermoelectric cooling system, a doped semiconductor material essentially takes the place of the liquid refrigerant, the condenser is replaced by a heat sink  106 , and the compressor is replaced by a DC power source  102 . The heat sink  106  may be fabricated with fins to exchange heat from the heat sink  106  with surrounding air. The application of DC voltage to the thermoelectric module causes electrons to move through the semiconductor material. At the cold side  103 , heat is absorbed by the electron movement, moved through the semiconductor material P and N, and expelled at the hot side  104 . 
     It should be noted that thermoelectric modules can only transfer heat from the cold side  103  to the hot side  104 , but cannot dissipate heat by themselves into the atmosphere. Hence, heat sinks must be in contact at the hot side  104  of the thermoelectric module to dissipate heat to the atmosphere through convection. Applications for thermoelectric modules cover a wide spectrum of product areas. These include equipment used by the military, medical, industrial, consumer, scientific and telecommunication organizations. Uses range from simple food and beverage coolers for an afternoon picnic to extremely sophisticated temperature control systems in missiles and space vehicles. Some of the more significant features of thermoelectric modules include: no moving parts, small size, ability to cool below ambient as well as heat above ambient, reliability and environmental friendliness. 
       FIG. 2  is a diagram of the top view of a small enclosure  200  air-conditioned by the thermoelectric effect. An air-to-air heat exchanger  201  is used for the cooling of air in an enclosure. The air-to-air heat exchanger  201  utilizes the thermoelectric effect whereby the heat is transferred via the flow of current through thermoelectric modules  202 . One part absorbs the heat and, as a consequence, reduces the temperature on the cold side  203  and the other part dissipates the heat to ambient on the hot side  204 . 
     Fans  205  and  206  are used to move air over heat sinks  207  and  208  on both the hot and cold sides of the thermoelectric modules. The cold side  203  of the modules  202  is connected to a heat sink  207  with a fan  205  (forced convection) that absorbs heat from within the enclosure  200  and circulates the cooled air. The hot side  204  of the thermoelectric modules  201  is connected to another forced convection heat sink  208  that dissipates the heat absorbed through the cold side  203  to the atmosphere. Forced convection improves the cooling performance. In  FIG. 2 , the thermoelectric modules  201  form the active cooling element and the fans  205  and  206  in combination with the respective heat sinks  207  and  208  form the passive cooling elements. 
     U.S. Pat. No. 6,119,463 describes a thermoelectric cooling system that cools seats by thermoelectric cooling air supplied to passages inside the surface of a seat. The heat is removed from the hot side of the TECs by a heat exchanger cooled by air passing over it and into the interior compartment of the vehicle. Thus, this apparatus cools the seat surface but heats the air in the interior of the vehicle. 
     Solar photovoltaic panels have been permanently constructed into vehicles. In land vehicles, such as cars and trucks, these panels have been built in the sun roof to supplement electric power for various applications in the vehicle. Some of these applications can operate without use of electric power provided by the vehicle&#39;s engine. 
     Permanently installed, solar photovoltaic panel-powered thermoelectric cooling systems have been developed for cars. Thermoelectric car air-conditioning has been previously described. Japanese Patent Application Publication No. 08-011517 discloses a built-in thermoelectric air-conditioning apparatus for a car powered by the battery, in turn, powered by the engine or, alternatively, a solar panel installed on top of the roof. However, this apparatus must be factory-installed for new cars or retrofit, at significant expense, in existing cars. Because the apparatus sticks out of the floor of the car, it is intrusive to the driver and/or passenger. 
     Additionally, Japanese Patent Application Publication No. 11-342731 discloses solar photovoltaic panel-powered thermoelectric cooling system. However, this system must also be factory-installed for new cars or retrofitted, at significant expense, in existing cars. Additionally, in a parked state, the hot sides of the TEC&#39;s are inefficiently passively cooled by external air flowing in a narrow passage between roof of the car where the TEC&#39;s are installed and the bottom of the solar photovoltaic panel. The apparatus sticks out of the roof of the passenger automobile such that the aerodynamics, stability and structural integrity of the car are compromised. 
     Accordingly, there is a need for a need for a compact, removable apparatus to prevent the temperature inside a vehicle from becoming dangerously high during stationary periods in sunny conditions without requiring an expensive retrofitting of existing vehicles, compromising the structures of vehicles, or using the battery of the vehicle. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an improved system, and its methods of use, for cooling the interior of a vehicle. 
     Another object of the present invention is to provide a compact and removable apparatus for cooling the interior of a vehicle. 
     Yet another object of the present invention is to provide a system, and its methods of use, for cooling an interior of a vehicle using a thermoelectric cooling assembly powered by a solar photo-voltaic panel without retrofitting the vehicle. 
     A further object of the present invention is to provide a system, and its methods of use, for cooling an interior of a vehicle using a thermoelectric cooling assembly powered by a low DC voltage from the solar photo-voltaic panel. 
     Yet another object of the present invention is to provide a system, and its methods of use, for cooling an interior of a vehicle using a thermoelectric cooling assembly powered by a low DC voltage from the solar photo-voltaic panel, wherein a direction of heat flow is controlled by a direction of the DC voltage applied to the TEC inside the thermoelectric cooling assembly. 
     These and other objects of the present invention are achieved in an apparatus for cooling the interior of a vehicle. A solar photo-voltaic panel is removably mounted on an inside of a window or a windshield of the vehicle. The solar photo-voltaic panel is mounted to block at least a portion of sun rays from entering the vehicle and configured to convert energy from the sun&#39;s rays to generate a DC voltage. A thermoelectric cooling assembly is powered by the low DC voltage from the removably mounted solar photo-voltaic panel. 
     In another embodiment of the present invention, an apparatus for cooling the interior of a vehicle includes a solar photo-voltaic panel removably mounted on an inside of a window or a windshield of the vehicle. The solar photo-voltaic panel is mounted to block at least a portion of sun rays from entering the vehicle and configured to convert energy from the sun&#39;s rays to generate a DC voltage. A thermoelectric cooling assembly is powered by the low DC voltage from the removably mounted solar photo-voltaic panel. Heat is transferred from air in the interior of the vehicle to an exterior of the vehicle through the thermoelectric cooling assembly. 
     In another embodiment of the present invention, an apparatus is provided for cooling the interior of a vehicle. A solar photo-voltaic panel is mounted on an inside of a window or a windshield of the vehicle. The solar photo-voltaic panel is mounted to block at least a portion of sun rays from entering the vehicle and configured to convert energy from the sun&#39;s rays to generate a DC voltage. A thermoelectric cooling assembly is included that is powered by the low DC voltage from the solar photo-voltaic panel. Heat is transferred from air in the interior of the vehicle to the exterior of vehicle through the thermoelectric cooling assembly. The thermoelectric cooling assembly includes a TEC. A direction of heat flow is controlled by a direction of the DC voltage applied to the TEC inside the thermoelectric cooling assembly. 
     In another embodiment of the present invention, a method is provided for cooling an interior of a vehicle. A solar photo-voltaic panel is mounted on an inside of a window or a windshield of the vehicle. The solar photo-voltaic panel is coupled to a thermoelectric cooling assembly that includes a TEC. The solar photo-voltaic panel is used to block at least a portion of sun rays from entering the vehicle. Energy from the sun&#39;s rays is converted to generate a DC voltage. At least a portion of the thermoelectric cooling assembly is powered by the low DC voltage. 
     In another embodiment, a method is provided for cooling an interior of a vehicle. A solar photo-voltaic panel is mounted on an inside of a window or windshield of the vehicle. The interior of the vehicle is thermoelectrically cooled using a thermoelectric cooling assembly powered by a low DC voltage from the solar photo-voltaic panel. The thermoelectric cooling assembly includes, a TEC with a cold side and a hot side, an internal heat sink in thermal contact with the cold side and in thermal contact with air in the interior of the vehicle on another side of the internal heat sink and an external heat sink in thermal contact with the hot side and in thermal contact with air in the exterior of the vehicle on another side of the external heat sink. The cold side of the TEC is sued to remove heat. Heat is transferred to the hot side of the TEC. The external heat sink is used to remove heat from the hot side of the TEC to an exterior of the vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of a practical TEC comprising two or more elements of p-type and n-type semiconductor material that are connected electrically in series and thermally in parallel. 
         FIG. 2  is a diagram of the top view of a small enclosure air-conditioned by the thermoelectric effect. 
         FIG. 3  is a diagram of a solar photo-voltaic panel manually and removably mounted on the front windshield of a vehicle by the vehicle&#39;s operator. 
         FIG. 4  is a diagram of a thermoelectric cooling assembly. 
         FIG. 5  is a diagram of a vehicle with its interior thermoelectrically cooled. 
         FIG. 6  is a diagram of a casing configured to transfer heat from the air interior to the vehicle to the air exterior to the vehicle. 
         FIG. 7  is a diagram of the interior of a vehicle cooled by the thermoelectric cooling assembly comprising a casing by transferring heat to the air external to the vehicle through a narrow opening of the casing extending through a window slightly ajar. 
     
    
    
     DETAILED DESCRIPTION 
     In one embodiment of the present invention, an apparatus and associated methods are provided for cooling an interior of a vehicle. Suitable vehicles include but are not limited to cars, trucks, trailers, planes, boats and the like. In one embodiment, the cooling apparatus is a thermoelectric cooling assembly powered by a low DC voltage from a removably mounted solar photo-voltaic panel, as more fully described herein. “Low” is of a sufficient amount to provide the necessary power. The amount of DC voltage is dependent on the internal temperature conditions found inside the vehicle. 
     In one embodiment, a solar photo-voltaic panel is removably mounted on the inside of a window or a windshield of the vehicle. The apparatus also includes a thermoelectric cooling assembly powered by a low DC voltage from the removably mounted solar photo-voltaic panel. The thermoelectric cooling assembly can be a TEC with a cold side from which heat is removed and a hot side where heat is transferred. The thermoelectric cooling assembly can include an internal heat sink in fixed, thermal contact with the cold side on one side of the internal heat sink and in thermal contact with air in the interior of the vehicle on another side of the internal heat sink. 
     In one embodiment, the thermoelectric cooling assembly includes an external heat sink in a fixed, thermal contact relationship with the hot side on one side of the external heat sink. In this embodiment, the external heat sink is in thermal contact with air or water exterior to the vehicle on another side of the external heat sink. 
     In another embodiment of the present invention, a method is provided for cooling the interior of a vehicle. A solar photo-voltaic panel is mounted on the inside of a window or windshield of the vehicle. A thermoelectric cooling assembly is used to cool the interior of the vehicle. The thermoelectric cooling assembly is powered by a low DC voltage from the removably mounted solar photo-voltaic panel. The thermoelectric cooling assembly can include a TEC with a cold side from which heat is removed, and a hot side to which heat is transferred. The thermoelectric cooling assembly can also include an internal heat sink in a fixed, thermal contact with the cold side on one side of the internal heat sink and in thermal contact with air in the interior of the vehicle on another side of the internal heat sink. The thermoelectric cooling assembly can include an external heat sink in a fixed, thermal contact with the hot side on one side of the external heat sink and in thermal contact with air in the exterior of the vehicle on another side of the external heat sink. 
       FIG. 3  is a diagram of one embodiment of a solar photo-voltaic panel  301  of the present invention that is manually and removably mounted on the front windshield  302  of a vehicle  303 , such as a parked automobile, by the vehicle&#39;s operator  304 . The solar photo-voltaic panel  301  not only blocks the sun&#39;s rays  305  from entering the vehicle  303 , but also converts the energy of the sun&#39;s rays  305  to generate a DC voltage that can be applied to a thermoelectric cooling assembly, as described below, which pumps heat out of the interior  306  of the vehicle  303  into the atmosphere  307 . 
       FIG. 4  is a diagram of a thermoelectric cooling assembly  401 . The thermoelectric cooling assembly  401  is powered by a low DC voltage from the removably mounted solar photo-voltaic panel  301 . The thermoelectric cooling assembly  401  can include a TEC)  402  with a cold side  403  from which heat is removed and a hot side  404  to which heat is transferred. The thermoelectric cooling assembly  401  can further include an internal heat sink  405  in fixed, thermal contact with the cold side  403  on one side of the internal heat sink  405  and in thermal contact with air  406  in the interior  306  of the vehicle  303  on another side of the internal heat sink fabricated with fins  407 . The thermoelectric cooling assembly  401  can include an external heat sink  408  in fixed, thermal contact with the hot side  404  on one side of the external heat sink  408  and in thermal contact with air  409  exterior to the vehicle on another side of the external heat sink fabricated with fins  410 . 
     Heat is transferred from the air  406  in the interior  406  of the vehicle  303  to the air  409  exterior to the vehicle  303  through the various components of the thermoelectric cooling assembly  401 . Heat is extracted from the air  406  in the interior  306  of the vehicle  303  by the fins  407  fabricated into the internal heat sink  405 . This heat extraction may be improved by placing a fan (not shown) to blow the air  406  in the interior  306  of the vehicle  303  into the fins  407  fabricated into the internal heat sink. 
     The heat is then transferred from the internal heat sink  405  to the cold side  403  of the TEC  402 . From the cold side  403 , the heat is pumped to the hot side  404  of the TEC  402 . Subsequently, the heat is removed from the hot side  404  by the external heat sink  408  and expelled to the air  409  exterior to the vehicle through the fins  410  fabricated on the external heat sink  408 . The transfer of heat from the fins  410  of the external heat sink  408  to the air  409  exterior to the vehicle  303  may be enhanced by a fan  411  connected to the fins  410  fabricated on the external heat sink  408  wherein the fan is configured to blow air on to the fins  410 . 
     The solar photo-voltaic panel-powered thermoelectric cooling assembly has no moving parts except for optional fans, are extremely reliable with an almost unlimited life span and require no maintenance, other than replacement of optional fans. “Static” construction makes thermoelectric cooling assemblies immune to vibration thus allowing them to be used in any orientation and makes them particularly suitable for application on moving systems including ships, aircraft and automobiles, including passenger cars. The thermoelectric cooling assembly does not contain any polluting substances such as chlorofluorocarbons (CFC) or other gases, has a more compact and simple structure than a compressor system, and can also be easily adapted and mounted. 
     In this embodiment of the thermoelectric cooling assembly  401 , the air  409  exterior to the vehicle is the atmosphere  307 . Alternatively, for vehicles floating, including docked or anchored, in water, the external heat sink  407  is in thermal contact with water exterior to the vehicle. 
       FIG. 5  is a diagram of a vehicle  501 , such as a parked automobile, with its interior  502  thermoelectrically cooled. The solar photo-voltaic panel  503  is removably mounted on the windshield  504  of the vehicle  501 . The thermoelectric cooling assembly  505  is removably and manually placed in thermal contact between air in the interior  502  of the vehicle and the air  506  external to the vehicle at another window  507  in the vehicle left slightly open. The direction of heat flow is controlled by the direction of the voltage applied to the TEC  508  inside the thermoelectric cooling assembly  505 . The solar photo-voltaic panel  503  can be folded and stored safely before operation of the vehicle  501  requiring viewing through the windshield  504 . The apparatus of the solar photo-voltaic panel  503  and thermoelectric cooling assembly  505  can be used by owners of existing vehicles without any retrofitting. 
       FIG. 6  is a diagram of a casing  601  configured to transfer heat from the air  602  interior to a vehicle  501 , such as a parked automobile, to the air exterior to the vehicle  501 . The casing  601  can be a TEC  603  inside the casing comprising a cold side  604  from which heat is removed and a hot side  605  to which heat is transferred. The cold side  604  of the TEC  603  is exposed to air  602  inside the vehicle  501  and the hot side  605  of the TEC  603  is exposed to air  606  exterior to the vehicle  501 . 
     An internal heat sink  607  is in fixed contact with an external surface of the wall of the casing  601  configured to be in thermal contact with the cold side  604  on one side of the internal heat sink  607  and air in the interior of the vehicle on another side of the internal heat sink  607 . The internal heat sink  607  may be fabricated with fins (not shown) on its other side to exchange heat from the air  602  interior to the vehicle with the internal heat sink  607 . The other side of the internal heat sink  607  may also be connected to a fan (not shown) to enhance heat removal from the air  602  interior to the vehicle. 
     An external heat sink  608  is in fixed, thermal contact with the hot side  605  on one side of the external heat sink and air outside the vehicle on another side of the external heat sink  608 . The other side of the external heat sink  608  may additionally be fabricated with fins (not shown) to exchange heat from the external heat sink  608  and the air surrounding the fins. Moreover, the other side of the external heat sink  608  may be connected to a fan  609  configured to blow air inside the casing on to the other sided of the external heat sink  608  and to facilitate the exchange of the air and heat inside the casing  601  with air  602  external to the vehicle  501 . 
       FIG. 7  is a diagram of the interior  701  of a vehicle  501 , such as parked automobile, cooled by the thermoelectric cooling assembly comprising a casing  702  transferring heat to air  703  external to the vehicle  501  through a narrow opening  704  of the casing  702  extending through a window  705  of the vehicle slightly ajar. The solar photo-voltaic panel  706  used to provide a low DC voltage to the thermoelectric cooling assembly is removably mounted on the windshield  707  of the vehicle  501 . Below the windshield  707  are shown various controls for the vehicle  501 . To prevent air leaking from the interior  701  of the car to the exterior of the car, a removable, sealing grommet  708  is placed in the area bounded by the top of the window  705  and the exposed frame  709 . The window  705  may be a window of a door of a parked automobile. 
     Additionally, the casing may be configured to have a fan  710  to facilitate cooling the interior  701  of the vehicle  501  with the thermoelectric cooling assembly comprising the casing  702 . The solar photo-voltaic panel  706 , the casing  702  and the removable, sealing grommet  708  can be manually installed by the vehicle operator without any retrofitting of the vehicle. 
     While the present invention has been described in connection with a number of embodiments and implementations, the present invention is not so limited but covers various obvious modifications and equivalent arrangements, which fall into the purview of the appended claims.