What is the main challenge of moving towards only using alternative energy sources such as wind, water, or solar

It's not too complicated

Explanation:

There are many factors to consider because there's different decision/energy complexities to factor. Your farming-role (energy requirements) determines the energy requirements.  

If you are an electrical farmer, for example, you might require intricate measurements of energy -- like sunar rays (solar ray force). This is one subverse to observent, before making a stupper decision.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.