*(b) Sizing study*

It is advisable to perform an initial screening of the components sizes at a simple spreadsheet level and at a conceptual design level: It is convenient to prepare the information for its use in the sizing tool (HOMER Pro is proposed, which in the last versions incorporates the Optimizer, and the automatic tool to search for the optimal configuration) and also it is convenient to have an estimate of the results. This spreadsheet may also be useful if a business model analysis is required, as HOMER Pro does not include it.

However, sizing tools require higher possibilities, such as the following: hourly basis simulation, which usually requires synthetic generation of data to compensate the possible lack of measured data; sensibility analysis, to cope with uncertainty of the inputs; more detailed (but still friendly) models of components, including all the necessary parameters to accomplish the study but at the lowest degree of complexity in order to make it useful; databases of commercial components, with the capability to create new ones.

At this level, both options of tools are available: commercial tools (either free or requiring a fee), such as HOMER PRO tool from Homer Energy by UL company, is an international reference; or self-designed proprietary tools, which take time and effort to develop but may be necessary if a specific analysis has to be made.

Real dynamic analysis is not usually necessary for these type of systems as they used to be inverter dominated microgrids based on a long-term battery using commercial power electronics solutions, which provide the necessary power quality and electrical stability to the system. However, it is convenient to implement this pseudo-dynamic analysis to assess the behavior of the battery through the simulation, mainly taking into account the influence of wind generation, as it was mentioned in Section 3.1. Whether this analysis is performed is up to the designer for establishing the stability of the system since the feasibility study does not cope with this issue.

The output of this stage in the design is a detailed behavior of the selected configuration in terms of stability and performance; the designer has to decide whether it is as expected or not (if not, then the designer would have to go back and make the necessary corrections on the configuration).
