Impact of Gas Third Party Access in the Unit Commitment Optimal Solution

The importance of the natural gas sector in the electric power industry has increased substantially over the last decades, reaching 21% generation capacity in Europe in 2016. Generation companies that own combined cycle gas turbines have to take into account not only the fuel and the operation and maintenance costs, but also the costs related to the third-party access (TPA) tariffs to the gas network. These TPA costs depend on the daily gas consumption for a whole month period, and this fact introduces additional transversal constraints. This paper highlights the importance of modeling these TPA tariffs in a more accurate manner, and presents the corresponding mathematical formulation that can be included in a unit commitment problem. The paper includes an example case that mustrates the impact of the TPA on the optimal hourly scheduling and it compares the results with the standard formulation based on individual cost functions.