The cooling cost consists of fixed cost (cc0) and variable cost (cc(T)) components; the former caused by activating the refrigeration system and the latter by how low the outside temperature is (T) and how long the system continues to work (t). It is reasonable to assume that if there is no product on board, there is no need for the
refrigeration system to be activated. As soon as products are loaded, the refrigeration
system is activated leading to the cooling cost. cc(T) can take alternative forms, based on different cooling systems and dcc/dTo0, i.e., the higher the temperature the less energy consumed.