## 5 Conclusions  
This paper presents a BESS dimensioning methodology for reducing the fixed term of the electricity access fee for industrial consumption, considering battery ageing and the cost of the BESS and electricity access fees. By connecting a BESS together with a consumption, the power demand peaks can be reduced, so there is no need for contracting a high fixed term power to cover the high demand peaks. A five-step dimensioning methodology is described, finishing with a cost-benefit analysis to facilitate the final decision making. The methodology is easily implemented and can be adapted to different electricity market conditions, as well as particularized to different BESS or load conditions. The parameter that defines the different scenarios of the methodology is the power contracted from the grid, being the decision variable the combined cost of the BESS and the fixed electricity fee. Results drawn from the two case examples show that implementing a small battery to limit the consumption peaks can lead to considerable cost reduction for the industrial consumer. In fact, the best techno-economical solution corresponds to a small BESS that limits the peak consumption. The low C rate, DoD, and steady temperature experienced by a BESS that only limits the top part of the peak consumption, guarantees a long lifespan that highly reduces the overall yearly costs. Given that BESS are over-dimensioned in energy in several scenarios (S6, S5, W8, W7, and W6), a higher contribution from the BESS could be imposed in order to reduce the fixed power contracted from the grid, achieving a higher peak reduction. However, this leads to an increased ageing (higher C rate, DoD, and temperature profile) that has an impact on the techno-economical decision, turning those solutions into non-optimum. Apart from the previous conclusion, depending on the case example and scenario under study, it could be beneficial from the economical point of view to increase the size of the BESS with more cells in parallel. This situation occurs when the BESS energy is suited to the BESS energy requirements (scenario S4). This forces the BESS to work with a high DoD and high C rates, deriving in a premature ageing. Thus, increasing the BESS size will allow it to work under less stress, extending the time needed to a BESS replacement and reducing the overall yearly costs. One important conclusion drawn form the case examples results is that the optimum BESS is over-dimensioned in both power and energy. This may indicate that other energy storage technologies different than Li-ion batteries could be more beneficial from the techno-economic point of view. Supercapacitors, which can last millions of cycles until they need a replacement, or flow batteries, which can dissociate energy and power, may be suitable for their inclusion in a further study. In addition, if the industrial consumption is facing a scenario with low consumption peaks, the optimum solution could be discarding the usage of an energy storage system at all. As previously stated, the presence of high consumption peaks is the reason that justifies the inclusion of a BESS together with the industrial consumption. Consequently, the proposed methodology is of potential interest for industrial consumers, since the cost-benefit analysis may reduce the yearly cost of their infrastructure, and also for TSOs and DSOs, since the peak reduction improves the efficiency of the transmission and distribution of the energy along the electric power grid. Moreover, BESS manufacturers could also find benefits in this methodology for the development of specific products related to this industrial demand peak and fixed term fee reduction. Suggested future works include the parametrizations of the grid with frequency and voltage variations, so that further analysis considering BESS contributions to the grid in terms of frequency and voltage regulation can be performed.