## 4 Research Needs and Trends in Wind Farm Design and Optimization
### Commercial Software  
Software tools are now being used to optimize wind farms. The most widely used commercial programs, including its strategies, are presented next. The Wind Atlas Analysis and Application Program (WAsP) v11 [48], developed in 1987 by the RISO National Laboratory, is considered the industry standard software for wind resource assessment and wind farm micro-siting. The software includes two different approaches for the wind resource quantification and wind resource mapping. The first approach is based on the so-called Wind Atlas methodology, which in turn is based on a set of linearized flow equations and is suitable for sites showing modest terrain complexity and near uniform roughness conditions. The second approach is based on the Reynolds-Averaged Navier-Stokes equations complemented with a standard \(k\)-e turbulence model, which is suitable to be used in complex terrain. Both approaches perform the procedures described in Section 2.1 to obtain accurate estimations of the local wind field and rely heavily on the quality and quantity of the measured data at the site. The WAsP software includes the possibility to perform different types of analysis regarding the wind farm production, the wind farm efficiency (incorporating the Park model, which is based on the Jensen-Katic wake model), wind data analysis, wind climate estimation, and wind atlas generation. However, it lacks an optimization framework for automated micro-siting. Nonetheless, upcoming versions of WAsP will incorporate the TOPFARM framework [164; 165; 166; 306; 354] as a complementary module that will allow to perform systematic optimization of wind farms. WindPRO v2.9 [49] is a robust tool developed by EMD International A/S that incorporates the WAsP engine for wind resource quantification. WindPro includes several different modules for the simulation and quantification of the wind farm energy production (incorporating the WAsP Park model to determine wake-based and turbulence-based energy losses) and environmental impacts (including noise impact, shadow flicker, and visual impacts). In addition, it includes modules for the electrical layout design and its optimization (including the quantification of power losses) and a robust financial balance model. WindPro optimizes the wind farm layout using the annual energy production as a performance metric while accounting for noise thresholds. However, shadow flicker, visual impacts and financial prospections are not accounted during the optimization procedure. The optimization is based on a pre-calculated wind resource map made up from the WAsP engine, which accounts for both the topography- and the roughness-based induced effects. Different types of optimization processes, based on greedy heuristics, can be performed: (1) a stochastic and gradual addition of WTs into the wind farm (without changing the preexisting WT positions) until no more WTs can be placed or a predefined maximum number of WTs is reached; (2) an iterative modification of the wind farm layout (by changing WT separation distances assuming a staggered or grid-like siting scheme); (3) an iterative filling up of the available land with WTs, resulting in a high dense WT cluster; or (4) optimization of noise operation modes for fixed wind farm layouts. The optimization processes depend on a set of predefined parameters such as the minimum distance between WTs, a predefined installed capacity per unit area and predefined restricted zones. The WindFarmer v5.2 [50] tool, developed by DNV-GL [PERSON], is similar to WindPro, as it incorporates the WAsP engine for wind resource quantification and offers a set of different modules for the design and optimization of wind farms. It includes the possibility of perform analysis regarding the energy production, noise impacts, visual impacts, shadow flicker, turbulence effects, electric system design, uncertainty modeling and financial balance prospections.