As there are many types of development in energy substitution to replace fossil fuels due to the recent energy crisis, one of them is to use solar energy.  The use of solar energy can be categorized into two types; one of the types is to use solar radiation for heating and the other type is to convert solar energy into electricity using solar cells. 
In either way, in order to use solar energy, it is necessary to have a device to collect the solar energy and the solar panels are generally used to absorb energy by directly facing the sunlight.  This type of solar panel has a structure of multiple solar cells in a flat type structure or having conduits to circulate operating fluids and the efficiency depends on the altitude of the sun. 
Accordingly, a tracking system to control the angle of the solar panel according to the altitude of the sun was used traditionally.  This type of tracking system can be categorized as a one-axis system or two-axis system depending on the number of rotational axes and is designed to gain maximum efficiency by adjusting the angle of the solar panel automatically or manually depending on the altitude of the sun with measured or previously gathered data. 
This type of solar panel is anchored on top of a rotational torque tube on top of the post on the ground.  On the other hand, said torque tube which supports the solar panel is supported by a post in the ground and the bearing is installed between the torque tube and post to enable smooth rotation.  Traditionally, said bearing is made of metal and a lubricant is applied to improve lubrication and to prevent wear.  But said lubricant must be added periodically and since the solar panels are installed on a vast area, adding lubricant is extremely inconvenient and hard to do.  Especially, while the lubricant has to be added to maintain friction coefficient to prevent the movement of solar panel due to wind pressure, the difficulty of work increases. 
Additionally, as outside dirt can attach to the lubricant, a process of periodic cleaning has to be done at the same time.