Solar Power

Solar engineering advancements contributing to reduced costs on large-scale projects

By Scott Canada, Senior Vice President of Renewable Energy at McCarthy Building Companies

Solar power has experienced extreme growth in recent years, and significant drops in plant costs have fueled much of the expansion. Within the past decade, solar costs have dropped by as much as 85% from above $ 6/W to $ 1/W in some locations, making solar project costs competitive with traditional generating resources in much of the Western United States. The cost reductions also open solar development within new geographies that have lower solar resources, such as the Southeast. These cost reductions have fueled additional growth of the resource.

Many cost reductions can be attributed to significant lowering of solar panel prices. However, there have also been important improvements in product design and engineering and workforce development, which drive reductions in balance of plant system costs. The industry has seen two major developments:

  1. Overall cost reductions on all solar projects.
  2. Lower solar costs for marginal sites (for example, sites that may have tough soil, difficult slopes or oddly shaped parcels).

Tracker Design

One of the most integral areas of improvement in solar power involves new tracker designs, representing a cost savings of 3¢/W to 10¢/W compared to just a few years ago.

Trackers are now designed as single rows with a tracker motor on each row. Prior to this, multiple rows were linked via an actuator arm to be cost effective. This resulted in 20 or more rows with a single actuator. With the new single-row design, there is now greater flexibility in site design resulting in opportunities for cost reduction.

There is also improved flexibility in the placement of trackers to optimize the land-use. Trackers can be placed in the most optimal arrangement to meet the financial return, PPA requirements and land-use options. For example, the newer tracker has reduced access areas because you can drive between tracker blocks. This allows the plant to optimize land-use giving the designers an opportunity to add DC capacity. The new design also allows for more above-grade wiring, which reduces costs and helps with maintenance and general accessibility.

Additionally, the newer trackers can handle steeper slopes, upwards of 10%. As recently as two years ago, trackers were only able to support up to a 3% slope, which meant many sites required tiered grading plans adding to project costs.

Moreover, many drives are now solar powered and controllers are wireless, which reduces the amount of cabling that runs from control boxes to tracker drivers. And trackers now have a larger range of rotation, which allows more electricity to be generated.

Pile Design

Another improvement in solar power comes in the form of pile support for the trackers. Testing and design procedures for piles have improved to provide a 1¢/W to 2¢/W reduction in costs. Many new trackers feature fewer piles, which reduces material needs and labor costs.

Prefabrication

An increase in prefabrication opportunities is responsible for another 2¢/W to 4¢/W reduction in solar costs. The prefabrication opportunities include electrical and trackers.

Electrical: Prewiring of combiner boxes, widespread use of wiring harnesses for the panels, auxiliary power and SCADA rack (rack, equipment mounted, wired offsite), precut fiber optic cable and precut paralleled DC feeder cable.

Trackers: Prepackaged hardware per megawatt, per block or per tracker kit has resulted in a streamlined process. Additionally, prefabrication of bearings, housings and other smaller components is now commonplace.

New Inverter Sizes

Inverters are larger and commonly single units between 2.5 and 4 MW at 1,500 Vdc. These units have an above-grade throat connection between the inverter and transformer, reducing the need for premanufactured skids and the wiring cost of the invertors. Furthermore, there is less DC wiring because the unit is 1,500 V. This combination is saving solar plant owners between 4¢/W and 6¢/W.

Labor Installation and Workforce Training

Finally, improvements in labor installation production methodologies and workforce training are helping reduce the overall project costs approximately 2¢/W to 4¢/W on solar projects. Contractors like McCarthy Building Companies are moving to a just-in-time material delivery methodology, providing the necessary equipment only when required in the correct quantity and at the correct time. This reduces the double handling of materials and field labor. McCarthy has also implemented Training Within Industries (TWI) to improve the capability of installers who are often recruited from local workforces and are unfamiliar with the solar installation process. TWI was developed during World War II to help certain industries facing a shortage of workers; it focuses on improved job training, which results in more skilled and productive employees.

As the solar industry gains experience, plant costs will continue to decrease and new innovations will provide for more flexible designs and installations. This will afford opportunities to refine designs thanks to collaboration among project owners, product manufacturers and EPCs. With each project completion, lessons learned will translate to real-world project improvements, reducing costs even further.

Solar Power World


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