  Although energy system optimisation based on linear optimisation is often
used for influential energy outlooks and studies for political decision-makers,
the underlying background still needs to be described in the scientific
literature in a concise and general form. This study presents the main
equations and advanced ideas and explains further possibilities mixed integer
linear programming offers in energy system optimisation. Furthermore, the
equations are shown using an example system to present a more practical point
of view. Therefore, this study is aimed at researchers trying to understand the
background of studies using energy system optimisation and researchers building
their implementation into a new framework. This study describes how to build a
standard model, how to implement advanced equations using linear programming,
and how to implement advanced equations using mixed integer linear programming,
as well as shows a small exemplary system. - Presentation of the OpTUMus energy
system optimisation framework - Set of equations for a fully functional energy
system model - Example of a simple energy system model
