The chemical pulp mill as a flexible prosumer of electricity

Abstract

Chemical pulp mills act as industrial-scale prosumers of energy, in that they demand heat and electricity for the production processes while supplying heat and electricity from the combustion of by-products. As such, they have potential relevance as providers of flexibility to the electricity system, supporting the integration of variable renewable electricity generation.In this study, a novel dispatch optimisation model is presented and applied to a generic mill, covering the production processes, boilers, and turbines, together with the associated storage of intermediate products. We analyse the trade in electricity between the mill and the central grid, the economic value of pulp mill flexibility, and the internal dynamics of the mill, when flexibility measures in different parts of the mill are combined.The results show that the suggested flexibility measures increase the amount of sold electricity during high-value hours and reduce the amount of sold electricity during low-value hours. In the present electricity market, the value of the electricity traded with the central grid is, thereby, increased by 1–8% compared to steady-state operation, without impacting the pulp production volume. The results reveal both synergies and conflicts between the different flexibility measures, underlining the importance of mill-wide optimisation.