1.  Field of the Invention
The present invention relates to a system for maintaining an unoccupied vehicle at a more comfortable temperature relative to the outside temperature using both heating and cooling.  The system uses an air duct with a fan, a heating element, vents, a solar panel and other control elements. 
2.  Description of the Related Art
On warm or hot days with the sun up, a vehicle parked unoccupied in the sun will experience a greenhouse like heating effect that is much more uncomfortable for driver and passengers to tolerate when entering than if the vehicle was parked in the shade.  Alternately, when the vehicle has been parked unoccupied on a cold night and/or day, the vehicle may be very uncomfortable for the driver and passengers to tolerate when entering. 
In the prior art, systems for providing an unoccupied vehicle with a more comfortable temperature used systems for cooling and/or ventilating the vehicle using solar power and/or batteries as the power source and a fan for forcing the ventilation. 
Exemplary references of this type are: U.S. Pat.  No.  3,943,726 to Miller issued on Mar. 16, 1976; U.S. Pat.  No.  4,939,986 to Turner issued on Jul. 24, 1990; U.S. Pat.  No.  4,942,806 to Hwang issued on Jul. 24, 1990; U.S. Pat.  No.  4,953,448 to Duh issued on Sep. 4, 1990; U.S. Pat.  No.  4,955,203 to Sundhar issued on Sep. 11, 1990; U.S. Pat.  No.  5,040,455 to Doi et al.  issued on Aug. 20, 1991; U.S. Pat.  No.  5,081,912 to Clenet issued on Jan. 21, 1992; U.S. Pat.  No.  5,148,736 to Juang issued on Sep. 22, 1992; U.S. Pat.  No.  5,167,574 to Ikeda et al.  issued on Dec. 1, 1992; U.S. Pat.  No.  5,205,781 to Kanno et al.  issued on Apr. 27, 1993; U.S. Pat.  No.  5,205,782 to Ohba et al.  issued on Apr. 27, 1993; U.S. Pat.  No.  5,248,278 to Fuerst et al.  issued on Sep. 28, 1993; and U.S. Pat.  No.  5,344,361 to Matthias issued on Sep. 6, 1994. 
Other exemplary references of this type are: U.S. Pat.  5,433,660 to Ohba issued on Jul. 18, 1995; U.S. Pat.  No.  5,588,909 to Ferng issued on Dec. 31, 1996; U.S. Pat.  No.  6,158,225 to Muto et al.  issued on Dec. 12, 2000; U.S. Pat.  No.  6,186,886 to Farrington et al.  issued on Feb. 13, 2001; U.S. Pat.  No.  6,435,961 to Biancone issued on Aug. 20, 2002; U.S. Pat.  No.  6,439,658 to Ganz et al.  issued on Aug. 27, 2002; Japanese Patent 114,522 published Jun. 1989; Swedish Patent 468,668 published Mar. 1993; German Patent 4,437,209 published Aug. 1995; European Patent 1,024,038 published Aug. 2000; and German Patent 10,021,807 published Nov. 2001. 
In the above prior art systems, no device was provided for adding extra heat to circulated air inside the vehicle to make the interior of the vehicle more comfortable to enter during cold weather. 
In another prior art system shown in U.S. Pat.  No.  6,433,915 to Mounir issued on Aug. 13, 2002, an unoccupied vehicle is maintained at a more comfortable temperature by providing a system using a complex film on the windows that changes state via electrical or temperature changes applied to the film, resulting in a change of color.  The color changes serve to heat or cool the vehicle via reflection or absorption of sunlight.  This prior art system implements a system to heat and cool the inside of the vehicle that is slow and which may not provide the amount of comfort level associated with the system in the present invention. 
It would be desirable to have a system for maintaining an unoccupied vehicle at a more comfortable temperature by providing both heating and cooling using solar power and batteries as the power source and using an electric fan and a heater. 
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.  Thus, a solar powered heating and ventilation system for vehicle solving the aforementioned problems is desired. 
The present invention is a system for maintaining an unoccupied vehicle at a more comfortable temperature relative to the outside temperature using both heating and cooling, as appropriate. 
The system uses an air duct having an electric fan, an electric heater, vents, a flap controller and flaps.  The system also uses a solar power panel, battery, selector switch and power control circuits.  The system provides power to the electric fan and electric heater via a selector switch and power control circuits.  The duct is located on the interior ceiling of the vehicle and has at least three vents.  The fan and heater are located inside the duct.  The first input vent is located on one side of the fan and heater at the front of the vehicle and the other two vents and flaps are located on the other side of the fan and heater at the rear of the vehicle.  One of the other two vents opens to the interior of the vehicle.  A second of the other two vents opens to the exterior of the vehicle above the rear window. 
When there is a need to cool the interior of the vehicle due to the heat of the sun acting on the vehicle as if it were a greenhouse, air enters the duct through the first input vent pulled by the fan mounted in the duct to the second of the other two vents opening at the exterior of the vehicle so that hot air can exit.  Flaps in the first of the other two vents are pushed or pulled closed to close off the exit of air back into the vehicle.  When there is a need to heat the insides of the vehicle due the lack of sun and cold outside temperatures, the interior vehicle air enters the duct through the first input vent pulled by the fan and pushed past active heating elements in the duct with air exiting at the first of the other two vents on the inside of the vehicle.  Flaps in the first of the other two vents are pushed to close off the exit of air to the outside of the vehicle at the second of the other two vents.  Thus, air is forced over the active heater and circulated back into the vehicle to warm the air inside the vehicle. 
During the heating of the interior of the vehicle, battery power may be the most used source of power since the sun may not always be available or adequate when temperatures are low.  Since the heater and the fan are both used and the heater requires so much more power than the fan, a power control circuit is used to regulate the power to the fan and heater.  The power control circuit will, based on the current draw from the heater and fan, decide whether to provide power from the solar cells or battery or both.  Also, it will prevent the battery from discharging so much that the vehicle cannot be started.  It will also cut off all power for the heater and fan if neither power source can provide enough power.  Also, the battery used may be the vehicle battery, or an auxiliary battery that does not provide power to any other parts of, the vehicle. 
Accordingly, it is a principal object of the invention to provide a system for maintaining an unoccupied vehicle at a more comfortable temperature relative to the outside temperature using both heating and cooling as appropriate. 
It is another object of the invention to provide a system for maintaining an unoccupied vehicle at a more comfortable temperature using solar power and battery as power sources. 
It is a further object of the invention to provide a system for maintaining an unoccupied vehicle at a more comfortable temperature using solar power and battery as power sources and using a controller to regulate power to the heater and fan which also prevents damaging discharge of the battery. 
Still another object of the invention is to provide a system for maintaining an unoccupied vehicle at a more comfortable temperature using a duct system with flaps and vents for providing circulation and heating of excessively cold air or exhaustion of excessively hot air inside the vehicle. 
It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.