Successful modelling requires that the appropriate modelling level be chosen.

Models can be developed at many levels of detailing, and there are many reasons why it is a good idea to identify the appropriate level.

For instance, if you are interested in the energy production or energy consumption of an energy system, and the system effect level is known, it is merely a simple input/output calculation. Any “bookkeeper” will be able to do that. 

If you are interested in identifying the process that will be able to realise the desired energy exchange, the process itself needs to be modelled. In this case, it is mainly thermodynamics knowledge that needs to be applied. In this case, a “physicist” is needed.

If you are interested in identifying the system – in terms of component choice and composition – that will be able to realise the desired process, you need to make use of your knowledge as an “engineer” in addition to the two above-mentioned modelling levels.

If the components are unknown, for instance, if they cannot be purchased ready-made, they need to be modelled at the highest level of detailing (design models), where consideration is given to the present geometry, etc.