Calculating weather windows: Application to transit, installation and the implications on deployment success

• We demonstrate a method to assess the accessible conditions for marine operations.
• We show the importance of considering all phases of an operation.
• Transit towing a marine energy device may have greatest impact on success.
• We provide information as to the implications of a lack of accessible conditions.
• A case study for installation operations at the Wave Hub is presented.

In order to fully utilise test sites, marine energy device developers must be able to deploy, maintain and decommission their equipment in a timely and cost effective manner. In addition, the marine energy industry is moving towards array deployments (DECC, 2012 and BBC, 2012) and whilst these deployments present an excellent opportunity to maximise resource usage whilst minimising the associated costs, for example of deployment, it is essential that said deployment is performed in a cost effective manner. Critical to this is the knowledge of the metocean conditions at the site and the weather window availability, particularly when this is coupled with vessel availability and downtime costs.In this paper a method is presented based on a Weibull model which uses cumulative distributions of the mean duration of persistence of exceedance (Stallard et al., 2010 and Walker et al., 2011a). The method discussed has been applied in a case study for the South West of England using site specific environmental parameters and empirical expressions to calculate the accessible periods. The outcomes from the case study are applied to identify the accessible periods and the waiting time for marine operations, and a discussion is made regarding the installation of wave energy devices at the south west Wave Hub (Wave Hub, 2010).