Page 10 - North American Clean Energy January February 2015

wind power

Optimizing Wind Turbine Layouts

Considering cost-of-energy & constructability

By Nick Robinson & Whitney Wilson

Image 1. Example of a potential wind farm site in Nova Scotia, Canada Image 2. Comparing the cost-of-energy (COE) optimization to energy optimization

more emphasis • Consider existing infrastructure
AS WIND CONTINUES TO MOVE INTO THE COMPETITIVE ENERGY MARKET,
should be placed on siting turbines with an understanding of cost implications. Accounting for the elements already onsite as part of the wind turbine optimization process
Historically, layouts have been completed by micro-siting turbines, to limit road and encompasses:
collection system length, or by a computer-based optimization tool, which optimizes for - Existing transmission corridors: Understanding the point-of-interconnection, and how to
energy. In either case, limited to no balance-of-plant (BoP) construction considerations use existing rights-of-way to beneit the facility; and

were given.
- Existing major and secondary highway systems: Understanding the best paths for site
With computerized optimization, a turbine could be moved to gain a greater energy access, along with how to best minimize inter-turbine road costs.
yield, but if it cost more to get that extra energy (say, through the construction of roads or
collection wiring), it’s of little use to developers.
• Calculate the costs
What’s needed in today’s large project scenarios is a cost-of-energy (COE) optimization Turbines aside, consider the expense to build new and to update existing infrastructure, including:
tool that can help develop a proitable turbine layout for a wind project, which considers - Minimizing access road costs;
everything from cost, production potential, and overall constructability, while maximizing - Minimizing collector system costs (while respecting cable capacity limits and breaking the farm
energy potential. By taking BoP costs into account, wind power developers could also ind into optimal circuits);

the optimal plant size, identify and eliminate high-cost turbines, and create more compact, - Utilizing existing infrastructure and rights-of-way to save expenses; and
lower cost layouts.
- Considering cost additives for diiculty of construction, or the potential need for specialized
To demonstrate and quantify the diference in the two methods, a case study was construction equipment.
completed for an area in Nova Scotia, Canada. In comparing layouts, the irst one was

created by optimizing the potential wind farm layout for energy only; whereas, the second An iterative approach
method was created by optimizing the layout for the cost of energy. he comparison A computer-based iterative approach allows developers to optimize the potential wind farm
identiies how a COE-based optimization method can minimize the expenses of production site layout, taking account of access road and collector system costs. Each iteration involves the
ratios for the turbines, while maintaining a beneicial layout.
following steps to evaluate each solution:
• Layout considerations. Generation of road layout, with concern for turning radius, max
Cost-of-energy optimization
gradient, cut-and-ill, existing roads, the buildable area available to roads, together with various
Cost and constructability of BoP measures should be considered early in the development crossing costs (water, wetland, pipelines etc).

process of a wind farm, as they can become rather pricey. Preliminary estimates on BoP • System design. Collector system design, with regard to the available land, circuit limits, cable
parameters can help to generate a turbine layout that’s closer to buildable and that’s lower capacities, substation locations and costs, possible grid interconnection points, and crossing
in overall COE, compared to one that’s optimized on energy alone.
costs for water, pipelines etc.
he following are the steps to be taken into consideration for optimizing COE and • Power production. Annual estimated energy production in relation to wakes, turbine

constructability:
performance, and other losses, including electrical losses based on the automatically generated
collector system design.
• Deine the buildable area
• Operations and maintenance. Consideration of O&M costs based on input parameters, and
By excluding areas that are culturally or environmentally sensitive, or that have major cost potential suitability.

implications for construction, it’s possible to:
• Additional expenses. Inclusion of other capital costs based on input parameters.
- Exclude excessive slopes: Deine the maximum gradients and turning radii;
• Balance-of-Plant costs. BOP expenses based on access roads and collector systems, together
- Avoid water bodies and wetlands: Exclude or assume a higher price to cross;
with per turbine costs, form the initial capital cost of the project—which is, then, paid back with
- Setback from parks/wildlife habitats: Exclude or assume a higher price to cross; and revenues derived from the energy production of the wind-farm.

- Maintain standard setbacks: Ofset from roads, structures, transmission lines, etc.
• Financial model. Employed to ind the COE for the turbine layout, such that the net present
value (NPV) is zero. Additionally, a inancial model re-run for each turbine is considered to ind
that turbine’s COE.
Continued on page 12.

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