The Earth is tilted toward Polaris, but its hemispheres lean toward or away from the Sun. Earth's tilt remains constant over the course of a year. Earth's movement around the Sun carries each hemisphere, in turn, to a different orientation relative to the Sun.
Since the clock produces 45 useful unites energy units for every 100 unites of energy that it uses, than it turns out that the efficiency of the clock is 45 percent.
