## 1 Introduction
They argued that combining the maintenance activities was cheaper than having each component of a system planned separately. [PERSON] et al. [34] proposed a model for the integration of maintenance and production planning considering the production losses due to preventive maintenance, corrective maintenance and operation dependent failures. [PERSON] et al. [35] discussed the problem of integrating production planning and preventative maintenance for a single machine in order to maximize its production capacity. A mixed-integer linear programming model was proposed to tackle the problem. [PERSON] et al. [36] proposed a preventive maintenance and production policy for a manufacturing system consisting of parallel machines considering the lease contract. The aim of the proposed model was to determine the economical production quantity and the preventive maintenance interval for the machines while minimizing the total cost of production and maintenance. [PERSON] and [PERSON] [37] investigated a bi-objective mathematical model which integrated both tasks; preventive maintenance planning and energy hub components repair under the assumption of stochastic demand. [PERSON] et al. [38] discussed the integration of production quality and the condition-based maintenance of a single-machine production system. The problem tackled assumes that a machine will have some product defects after a certain level of degradation. The model considers the inspection time and preventive maintenance to reduce off-specification products. The oil and gas supply chain includes many petrochemical plants such as sweetening plants, refinery plants, gas plants, and fractionation plants which constitute connected and advanced equipment to help maximize the value of the petroleum product. To reduce the sudden breakdown, prolong their lives, and minimize the lifetime cost of energy, both operations and maintenance costs need to be optimized simultaneously. Similarly, renewable energy plants such as onshore/offshore wind energy plants involve many connected units that need to be maintained regularly. Wind power is often considered as an expensive source of energy. Therefore, coordinating operations and maintenance decisions will reduce the costs for operations and maintenance which indicates that there is large potential in cost-savings. Several studies have optimized operation and maintenance scheduling for renewable energy power plants applications. For example, [PERSON] et al. [39] developed an optimization model to coordinate the operation and maintenance activities for offshore renewable energy farm. [PERSON] et al. [40] studied the integration of operation and maintenance scheduling of an offshore wind farm by conducting a sensitivity analysis to identify the most significant factors affecting availability and operation and maintenance costs. [PERSON] et al. [41] optimized the operation and maintenance activities of an offshore wind farm using genetic algorithms in order to minimize operation and maintenance costs of the offshore farm while maximizing both the availability and reliability. [PERSON] et al. [42] studied the optimization of the operation and maintenance strategy of a wind farm using a big data approach with the aim to understand the failure mechanisms of wind turbines. [PERSON] and [PERSON] [43] developed a mathematical model for operation planning and maintenance scheduling of a single wind turbine. Both condition-based and corrective maintenance are compared taking into consideration constraints of design and inspection. [PERSON] [44] developed a mathematical model for coordinating the operation and maintenance decisions for an offshore wind farm. This model minimizes the lifetime cost of energy by optimizing both the operations and maintenance costs of offshore wind farm. [PERSON] and [PERSON] [45] conducted a comprehensive review on the area of operation and maintenance of offshore wind farms.