*3.1. Operating Principle*

The Logistics and Marine Operation (LMO) module was designed to generate optimal logistical solutions for the installation, O&M, and decommissioning phases of ocean energy projects. These logistic solutions consist of an operation plan (featuring dates and sequence of activities) and an optimal combination of vessels, equipment and ports that minimize the costs of each operation individually, reducing the capital and operational expenditures (CAPEX and OPEX) of the project.

The operating principle behind the LMO module is similar for all three life cycle stages of the project, and can be described as a sequence of different steps, as schematized in Figure 2. First, the LMO module collects design inputs from the user and previously run Deployment design modules (listed in Section 2), data related to the devices and subsystems that must be installed, maintained, and dismantled throughout the lifetime of the project (see Figure 3. More information about the inputs available in [46]). These attributes are subsequently converted into project logistic requirements (e.g., *N* monopiles with specific dimensions and a given weight need to be lifted, transported, and installed). Second, based on the specified components and identified requirements, the corresponding marine operations that must be carried out are identified (e.g., pile installation). In respect to O&M, two maintenance types are simultaneously considered in the LMO module: preventive (time-based maintenance) and corrective, based on failure events generated by the RAMS module [47] taking into consideration component failure distributions.

**Figure 2.** Working principle of the Logistics module.

**Figure 3.** Schematic representation of the inputs to the LMO module.

In a third step, the process of identifying feasible infrastructure solutions begins. Vessels, ports, and equipment must not only meet their minimum individual prerequisites imposed by the project, but also be compatible between each other. Then, for each potential logistic solution, defined by a specific operation plan and infrastructure setup, the operation

net durations and expected waiting on weather (WOW) are computed based on historical weather data and a operation catalog, featuring reference operation durations and weather restrictions (e.g., maximum wave height and maximum wind speed). Following the calculation of the total operation durations (including weather delays), for each logistic solution, the operation total costs can be calculated by considering the daily costs of the infrastructure setup. Finally, the logistic solution that presents the lowest operation total costs can be chosen as the optimal solution.

In the DTOceanPlus software suite, each module was developed with three levels of complexity (Cpx1, Cpx2, and Cpx3) to accommodate different stages of project maturity, and different amounts of data availability and uncertainties. In LMO, the main differences between complexity Cpx2 and Cpx3 are the certainty of the inputs and whether default values are assumed instead of requesting these from the user. Alternatively, the simplified mode (Cpx1) can be used for early stage technologies, at lower technology readiness levels (TRL 1-3), or whenever limited information is available about the technology design and project specifics. The simplified mode may also be used to provide a quick and rough estimate for higher TRL projects. Finally, a "study comparison" feature was implemented in DTOceanPlus to enable the user to evaluate and compare different inputs, strategies, and scenarios, in respect to their impacts on the logistic solutions.

In order to carry out the design of the installation, maintenance, and decommissioning phases, the LMO module employs databases of vessels, port terminals and operations, that will be publicly available once the final version of the DTOceanPlus suite of tools is released.

### *3.2. Compilation of Operations and Logistic Requirements*

In a first step, the Logistics and Marine Operations module reads component design inputs generated by previously run DTOceanPlus Deployment Design modules and/or introduced by the user. Based on the specified component designs, number of components, and user preferences, the LMO module identifies and proposes to the user a list and sequence of operations to install, service and/or dismantle a given ocean energy farm (see Table 2 for the list of operations considered in LMO). For each operation, relevant operational methods (e.g., transportation method and piling method) are read from upstream modules (e.g., cable burial layout is generated by the Energy Delivery module, using specific cable burial methods), or requested to the user, as described in Table 3.

Based on the identified operations and specified operation methods, infrastructure requirements are defined (e.g., the vessel's deck area must be sufficient to transport at least one device or system). Infrastructure requirements are compiled in Table 4.


**Table 2.** List of operations for each project phase included in the Logistics and Marine Operations module.


**Table 3.** Operation methods considered in the LMO module.

**Table 4.** Infrastructure requirements considered in the LMO module.

