# Peak Energy Reduction in Flow Shop including Switch-Off Policies and Battery Storage
## 1 Introduction and Motivations  
The efficient use of energy is crucial at different levels; the reduction of energy consumption allows to cut the production costs (energy bill) and meet the objective of CO2 emission level. The sector of industrial activities accounts for about 24% of the global greenhouse gas emissions [1]. A drastic reduction in emissions, around 80%, can be achieved by improving energy efficiency and introducing renewable energy sources [2]. From the point of view of production costs, the energy bill can be reduced by pursuing energy-saving and reducing the peak power costs. In several manufacturing systems, the idling power consumption is comparable to the operating power consumption. Then, the switch-off policies to turn off the idle machines are suitable for many manufacturing processes [3].  
The power usage agreement between users and energy providers defines a maximum power constraint. This constraint is necessary to ensure the stability of the power grid and the use over the constraint leads to significant penalty costs [4, 5].  
The reduction in the price of lithium-ion batteries has made this component available to support the energy storage system [6]. Furthermore, the reuse of Li-ion battery packs for electric vehicles can be very relevant to storage systems in production systems [7, 8]. Energy storage in manufacturing systems can contribute to saving energy costs. The energy can be stored when the demand is under the maximum power usage constraint and using it when the demand is over the constraint.  
The above discussion introduces three topics (battery, switch-off, and peak power constraint) that have been studied separately in the literature.  
The literature review (as discussed in the next section) highlights that the energy storage system is used mainly to align the energy provided by renewable sources with the energy demand of the manufacturing system; moreover, the switch-off policies are proposed only to reduce the energy consumed in the idle state of the machines. Then, this study evaluates the introduction of the energy storage system to reduce the costs due to thepeak power constraint. The other original contribution regards how the switch-off policies and energy storage systems work together and if they can be a real value added to reduce the costs of peak power constraints.  
This study proposes and evaluates the introduction of an energy storage system in a flow line that works with switch-off policies. The study considers different battery characteristics as capacity and charging speed. In addition, the power fluctuation is considered in the flow line.  
We use the simulation to evaluate the performance compared to a system without an energy storage system. It is evaluated the improvements of the only energy storage system and then the value added by the switch-off policies. To our knowledge, no previous studies investigated the integration of switch policies with the battery storage system.  
This paper is organized as follows. Section 2 discusses the recent works proposed in the literature about the energy storage systems, switch-off policies and peak power constraints. Section 3 describes the reference context and the proposed approach with energy storage and switch-off.  
Section 4 shows the simulation experiments, while Section 5 discusses the numerical results. Finally, Section 6 reports the conclusions and future research developments.