Openwind has the capability to optimise layouts to minimize the cost of energy, taking into account both energy production, O&M costs and capital costs including turbine and balance-of-plant costs. In order to do this it combines the standard energy capture and turbine siting routines with routines for designing the collector system and access road networks. The cost of energy is then evaluated in a financial model, which iterates the net present value (NPV) of the project to zero. Openwind relies on the user to input collector system and road costs as well as other financial assumptions and provides multiple ways in which the user can guide the process.
In order to use the OCOE, each turbine layout that is included in the optimiser needs access to one tree layer whose interpretation is Site Roads as well as one tree layer whose interpretation is Site Cabling.
Each of these tree layers can be created by right-clicking in the left hand panel and then selecting New Layer and Tree Layer. Both of these layers need to be created (digitised) with just one start node. For the site access roads, the start node should be positioned as close to the centre of the project area as possible while driving a turbine truck on existing roads. If this happens to be outside the project area, which is fine as the road optimiser can upgrade existing roads in order to get closer to the site.
When it comes to the collector system start node, there is no need to add one any more as this has been superseded by the use of Grid Connection Points. Each collector system can use one or more grid connection nodes and will consider all grid connection points which are visible using the layer hierarchy, regardless of whether they are being used by another collector system or not and regardless of which option is chosen as the substation strategy. In addition to one or more grid connection layers, it is also necessary for each collector system layer to be able to see one or more substation layers containing one or more Substation Points.
In the cost of energy collector system settings there is a choice between auto-placing the substation and using fixed substation locations (see Turbine-Specific and Balance-of-Plant Costs ). If the first option is chosen then the properties of the first substation are used to auto-place a single substation for each collector system. If the second option is chosen then all substation locations are considered. The decision to use or not use a grid connection or substation is made purely on the basis of minimising the BOP costs and so it is perfectly possible that one or more grid connection or substations will not be used. If this is the case then the associated costs will not be included in the financial model.
Once the cost of energy has been run then the access road and collector system solutions will be available in the geometry tab of the respective tree layer properties. This is a detailed breakdown of every single section of road and collector system including what factors influenced the cost of that section. The grid can be reordered by headings so that the user can group all stream crossings or pipeline crossings together or to order from highest to lowest cost and so on. Clicking on a record will cause that road or collector segment to flash in the mapping view (note: there is currently an issue with road events being sometimes assigned to the neighbouring segment but this should not affect the validity of the solution so far as we are aware – we hope to rectify this in a future update).