What is changing the way wind farms are constructed?

This article is part of the 2017 Renewable Energy Handbook. A complete digital version of the Handbook is here: https://goo.gl/Sg4mHO

Several trends underway are changing how wind farms are constructed. In a nutshell, the trends have been working to trim time and cost from the work that goes into a wind farm and that has led to new equipment and construction methods. The principles of lean manufacturing are being applied to trim waste time and labor as it is found in construction activities.

A tower and rotor are ready for assembly at the Tucannon River Wind Farm during construction in the summer of 2014.

On the financial side, the big stimulus to get things done as quickly as possible has been the Production Tax Credit. It provides about 2.3 ¢/kWh for the power produced. That figure will drop 20% in 2017, 40% in 2018, 60% in 2019, and will disappear in 2020. Before that, however, the wind construction industry will remain working at full speed using modern construction equipment and methods.

One piece of equipment in particular is the MLC650 crane from Manitowoc. The VPC MAX option increases the cranes capacity from 716 to 770 tons, and the luffing jib adds to the standard 331-ft. lift height for a total of 357 ft. The company says it has a 50% greater load capacity than competing models. That’s useful on wind farms because it allows lifting larger and more complete nacelles, or a hub and rotor that have been assembled on the ground – not in the air. Building on the ground is easier than lifting and fastening each blade to a hub 300-ft. up.

The notable new feature on the crane is the variable position counterweight that shortens work time. Controls automatically position the counterweight based on the crane’s load and required radius. The weight moves on a track either away from the crane cab or toward it to keep the center of gravity over the crane tracks. The capability has several plusses. For one, the crane need not set up for every lift on a jobsite. It can be erected and set up once and then the crane adjusts itself for different lifts. The moving counterweight means less overall counterweight is needed for work. On conventional high-lift cranes, counter weights (some in 10-ton increments) are added to a fixed bed or removed as lift needs change, a time-consuming task. Also, a wider track than the 60-in. standard is available which means lower ground bearing pressure, hence, less job site prep.

Another factor that has improved wind farm construction is the application of lean construction principles. These come from lean manufacturing principles that have the goal of identifying and eliminating waste from every step in a project. A few lean construction principles include:

  • Making sure value-added activities flow smoothly
  • Buildings should be prefabricated and modular
  • Nothing is made or delivered until needed
  • Recognizing that perfection is sought by a commitment to continually improve the entire process. One construction crew leader, for example, says that after each project, subcontractors and other bosses gather to discuss what slowed things down and how to eliminate them in the next job.

An example of applied lean construction comes from the 267-MW Tucannon River Wind in Washington State. It received a Gold rating from ISI Envision by meeting its sustainability principles. For instance, the wind farm was sited to avoid all wetlands and surface water, floodplains, steep slopes, and other potentially fragile or hazardous terrain.

Before construction began, a design team evaluated ways to reduce the project’s net embodied energy. For example, turbine foundations were designed to reduce the amount of required concrete and a significant portion of construction materials used in the project was sourced locally. This cut transportation costs and boosted the local economy. In addition, materials excavated during construction were retained and reused onsite where possible.

The effort is paying off. Not long ago, it was safe to use $2 million/MW as a cost estimate for a wind farm. Today, thanks to lean principles, one farm was constructed in Iowa at $1.69 million/MW.

This section was written by Paul Dvorak, WPE&D editorial director

 

Windpower Engineering & Development