Possible analogy to help students understand the Kelvin–Planck statement of second law of thermodynamics Let us consider a person has to transfer four bags upstairs to the top floor of a building.He Carries them one by one.Once he reaches the top floor, he has to return back to the ground floor to get the next bag. Without returning back, he will not be able to continue to transfer the bags.Just like the person, the system has to return back to its initial state to continue the cycle.To return back to the initial state, the system has to reject heat to a lower temperature sink.
Can this be presented as an analogy to explain the Kelvin Planck statement? Is this right or acceptable?

 A: In simple words the Kelvin–Planck statement states something like "it's impossible to have a cyclic process which transfers heat into energy with 100% efficiency". I know that the statement is actually more complicated than this, however, to me the efficiency is the key point of this statement. However, your statement misses this point, because your statement focuses on the concept of a cyclic process. In my words your statement say something like: In order to have a cyclic process, we have to bring the system back into its initial state. Thus, also your statement is perfectly fine, it misses the key point of the Kelvin–Planck statement. Do you agree?
A: The Kelvin-Plank Statement of the Second Law is "No heat engine can operated in a cycle while transferring heat with a single heat reservoir".  What this means is no heat engine can take heat from a single reservoir and convert it entirely into work (100% efficiency) in a cycle. Some heat must always be rejected to a lower temperature reservoir in order to complete the cycle and produce net work.. 
Your example cannot be presented as an analogy to explain the Kelvin-Plank statement. For one thing your example does not involve heat transfer. For another, the person in your example is not thermodynamically returned to his/her original state after returning to get the next bag. The person has expended internal energy (burned calories) raising the bag (as well as him/her self). Those calories are not replaced by simply returning to his/her original position. In a thermodynamic cycle all of the properties of the system (in this case the person being the system) have to be returned to their original state. That is not the case for the person returning for the next bag.  
By the way, a person's mechanical efficiency is the mechanical work performed divided by the body's chemical potential energy used to perform the work. According to one source, the body's mechanical efficiency is about 25%. A Corollary to the Kevin-Plank statement is: No heat engine can have a higher efficiency than a Carnot Cycle operating between the same reservoirs. 
The Carnot efficiency is
$$e=1-\frac{T_L}{T_H}$$
Where $T_H$ is the temperature of the high temperature reservoir (which delivers heat to the engine) and $T_L$ is the temperature of the low temperature reservoir (to which heat is rejected by the heat engine).
Hope this  helps.
