Passive cooling device for extending battery life

DETAILED DESCRIPTION In accordance with the present invention, an electrical-energy-supplying device having an extended storage life, which may be used as a battery backup power supply for a TOU watt-hour meter when utility power is interrupted, comprises a battery for supplying electrical energy and chimney means for generating an air flow to dissipate heat from the battery, with the rate of air flow in the chimney being responsive to the intensity of sunlight incident on the chimney.
In the preferred embodiment of the invention, the battery is placed within the chimney and the air flow generated by the chimney passes directly over the battery housing, removing heat from the battery.
The chimney means is exposed at least in part to the incident sunlight which heats the battery.
The heating of air within the chimney results in a natural convective flow in which the heated air rises through the chimney and exits the upper end of the chimney.
Cooler outside air is drawn into the bottom of the chimney, thereby allowing heat from the battery to be rejected to the cooler air flowing up the chimney.
The chimney body preferably has a lower segment, the exterior of which is light reflective, and an upper segment, the exterior of which is light absorptive.
The lower segment may also advantageously comprise a low thermal conductivity material to minimize heating of the air contained within the lower segment, and an upper segment that comprises a high thermal conductivity material to enhance heating of air enclosed by the upper segment.
Air in the chimney upper segment is warmed when light or other heat energy is incident on the heat-absorbent upper segment; the warmed air will rise in the chimney through natural convective flow and exit the chimney through the opening in the upper segment.
The rising air causes cooler air to be drawn into the bottom opening and then up through the chimney to create a draft.
Air will thus continuously circulate through the chimney as long as sufficient light or heat energy is incident upon the heat absorbent upper segment to sustain a draft which will draw fresh air into the open bottom of the chimney