Optimisation of auxiliary, renewable energy resources and stationary storage in the context of a liberalised electricity market

This document addresses the possible uses of batteries on the Belgian grid with a potential combination with renewable energy sources. The case study concerns a battery storage system integrated on the same site as renewable units whereas the objective is to find the most profitable function for batteries. After describing the mechanisms ruling the electricity market in Belgium, the choice is made to limit the study to two cases. The first approach will be to operate the system on the day-ahead spot market and to perform arbitrage. A support will also be brought to renewable generation in the form of imbalance compensation. Assuming accurate prediction of the prices, arbitrage relies on an optimisation of the day-ahead charge and discharge profile. Imbalance compensation, however, is based on historical values of the grid total imbalance in order to smooth the renewable generation. This study will show that, even if it is possible to plan the operation on the spot market and partially balance the renewable generation, the income generated is not sufficient to justify the investment. The second approach will focus on the ability of batteries to provide frequency containment reserve. As this product is strongly regulated, several control mechanisms will be compared and the size of the system optimised based on its net present value. This part will show that, following a given algorithm, it is possible for a battery storage system to be profitable. Throughout the document, emphasis will be given to the influence of the battery size but also to the regulatory framework within which the study falls.