Effective Projected Area

What is an Effective Projected Area (EPA)?

Effective Projected Area (EPA) is a structural and civil engineering concept that evaluates a structure’s response to wind forces. The EPA is the area that the wind acts upon, projected onto a plane perpendicular to the direction of the force. Essentially, EPA aims to determine how the structure will react to wind forces head-on.

EPA is an overarching concept applied to lighting poles, signs, telecom towers, and even buildings to make sure they can withstand expected wind conditions. EPA can also be applied to wind turbines, although they are built from the ground up to withstand wind.

Effective Wind Area (EWA) is often confused with EPA, but it has a more narrow focus — EWA refers to a specific portion of a structure exposed to wind loads. EWA is more commonly used with wind turbines to improve turbine efficiency and resilience to wind forces. 

EPA is a Vital Engineering Metric

Nearly any industry with structures outside needs to calculate EPA and make design changes prior to changes. An EPA structure needs to be able to withstand the maximum amount of wind it may be subjected to, which varies based on location.

Structures like buildings can use an EPA wind rating map to help determine how much force the future structure needs to withstand in its specific location. Using an effective projected area calculator based on this data helps engineers throughout the design process.

However, other structures, like wind turbines or lighting posts, are often manufactured without knowing exactly where they’ll be installed. That’s why these types of structures place a focus on wind resistance from the beginning — they might end anywhere in the world.

Design and Engineering

Understanding how wind forces react with a turbine is commonly used throughout the engineering phase. For example, evaluating how blades will react to different wind forces optimizes future performance and durability.

Fortunately, leading-edge solutions provide added utility to simulate wind forces on turbines and other structures. The same underlying mathematics becomes visual to understand better if a turbine is ready to build or needs additional engineering.

Load Calculations

Similarly, wind turbines are inherently exposed to intense winds, so calculating how a new turbine will respond to high wind loads is of the utmost importance. EPA is used to understand the maximum wind conditions a turbine can withstand, allowing the manufacturer to make changes or refine specifications provided to wind farms. 

Additionally, EWA often focuses on the forces that the blades can withstand and use effectively. These metrics go beyond preventing collapse and ensuring optimal functionality.

Performance Analysis

Something unique to wind turbines and EPA is that it’s also an indicator of future performance. Other structures simply need to withstand wind forces, but turbines need to generate electricity from them efficiently. These calculations and simulations are foundational to developing performant turbines.

Any structure that will be subjected to wind, from billboards to telecommunications towers, must be resilient to high wind forces. The estimated projected area helps ensure this durability, and when applied to turbines, it provides even more value by optimizing performance.

Safety Standards

Manufacturers and wind farms are typically subject to safety regulations and must remain compliant. Engineers need to accurately calculate how much wind force a turbine can withstand, while wind farms need to make sure their turbines will withstand high wind forces in their specific region.

Do Wind Farms Use EPA?

Wind farms don’t typically use EPA or EWA during day-to-day operations. Instead, the focus is more on present conditions and adjusting as necessary by understanding EPA and EWA rather than continually calculating them.

However, the EPA will need to consider some types of maintenance and repairs to ensure ongoing structural integrity. If handled in-house, a wind farm’s technicians will need to understand how to handle specific tasks affecting EPA and EWA.

Ultimately, wind farms need to understand their turbine’s EPA before installation and during repairs. Otherwise, there’s a risk of non-compliance, suboptimal performance, or even turbine collapse.