between about 40 mm and about 100 mm between the supporting surface 38 and the wall attachment surface the engagement channel 44 preferably extends upwardly between about 400 mm to about 1400 mm from a bottommost surface of the support housing 32 as seen in fig4 the exterior facing surface 34 defines on an upper portion an air inlet 46 for permitting a constant flow of ambient air into an interior chamber of the support housing 32 provided over the air inlet 46 are a number of vertical bars or strips laterally spaced apart from each other to prevent larger solid objects from entering through the air inlet 46 and without significantly affecting or reducing air flow therethrough the exterior facing surface 34 furthermore defines on a lower portion a power supply retention slot 48 which extends into the exterior housing portion 40 as shown in fig6 and which is sized for removably retaining a removable rechargeable battery 50 it is to be appreciated that while the retention slot 48 is shown with the removable battery 50 disposed therein the retention slot 48 may be configured to receive other power supply components such as an electrical power converter connected to.