Page 24 - North American Clean Energy May/June 2019 Issue

solar energy
4 Ways to Save Time
on Solar Tracker
Installations
by Matthew Schneider
Over the past decade, solar trackers have evolved to become less expensive, and easier to operate and maintain. ese innovations, along with an increase in the scale of production, help explain how global tracker shipments topped 20 gigawatts in 2018 - accounting for over a quarter of ground-mount installations worldwide. at’s more than 87 percent of utility-scale systems in the United States.
But most trackers in the eld continue to use electric motors and gearboxes. ese limit design exibility, restrict the addressable market for solar tracking systems, and increase labor costs, making it unnecessarily di cult for many projects to pencil out on sites that are not simple rectangular parcels of land.
In 2018, the market started wide adoption of motor-free, air-driven tracker systems. ese systems remove design constraints; they reduce the costs of civil work, labor, material handling, and site management, all of which will help the global market reach new heights in the years ahead.
Eliminate civil work
Site preparation time and expense vary from project to project. Cutting away slopes and lling in sections of land can undermine or ruin project economics. Additional unexpected costs are incurred when ood plains or wastewater runo needs to be addressed, or if project designs need
to accommodate habitats of native species. e keys to minimize these costs are to reduce or eliminate earthwork, and take full advantage of the layout exibility available from motor-free tracking systems.
To reduce and eliminate time consuming and expensive earthwork, project developers and EPCs can use trackers with easily adjustable spans that can follow the grade, and typically eliminate the cost of civil work.
Adjustable-length spans have the added bene t of reducing post length and tracker height. A 90-module-long tracker on land with a 2 percent grade is 6 feet higher at one end than the other. is typically requires ladders to be used to complete module installation. On the other hand, a 30-module-long tracker on the same land has a height increase of only 2 feet.
Lay modules at
Module attachment is typically the single most time-consuming step in the construction of a new project. It accounts for as much as 40 percent of time at the job site. Module installation crews spend most of their time ghting gravity - holding modules while waiting for other crew members to bolt them in place.
Two simple tracker system improvements dramatically reduce module installation time. e rst eliminates torque tubes and replaces them with dual rails (purlins),
so modules can lay at across the top of the rails and crew members aren’t spending time holding them in place. e second uses top mounting clamps that hold modules in place, allowing crews to nish tracking system installations without working underneath the modules.
ese improvements reduce direct labor time and time spent on the construction site, so that trailers, forklifts, security personnel, portable toilets, and other general conditions-related budget line items can move to the next project sooner.
Reduce walking with fewer unique components
Each unique structural component delivered to a job site increases the time wasted walking though the project. Each person walking a project, up one row and down the next, adds 1.88 miles of walking per megawatt to their day.
ere are typically four types of crews, with about seven construction laborers overall. One crew distributes the components throughout the eld. Another hand tightens components in place. A third tightens fasteners with a torque wrench. A fourth performs quality inspections. For every megawatt, each unique component adds 13 miles of walking.
e number of unique components in a tracking system can range from streamlined systems with three core components, to standard systems with 15 components or more. Streamlined systems can eliminate 156 miles of walking per megawatt – not including the work of removing components from pallets or collecting trash at the end of the day. Fewer unique components can eliminate a tremendous amount of wasted walking.
Use a single type of post
Traditional tracking systems use multiple types of posts (bearing posts and actuator posts) in each row. Streamlined systems eliminate this complexity, avoiding the need to distribute multiple post types to speci c locations throughout the eld. is reduces construction cost.
Streamlined systems also employ drives at every post. is enables the EPCs to use shorter, lighter piles, with as little as 4 feet of embedment. Smaller piles reduce post driving crew sizes, speed up driving times, and result in fewer post rejections.
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