New Projects, News, O&M, Renewables, Solar

Illuminating the Path to Successful Solar Construction

Navigating the dimly lit road of utility-scale solar requires the collaboration, continuity and experience of engineering-led EPC firms.

Within the span of one second, the sun produces enough energy to satisfy the earth’s needs for 500,000 years. In other words, more power is delivered to our planet in a single hour than humanity uses in an entire year. It’s no wonder the $17 billion U.S. solar industry is on track to double its installations by 2023.

Solar’s swift ascension and incredibly high ceiling for future growth have enabled the sunny source to stake its claim as the unquestioned leader in the burgeoning renewable energy market. The driving force behind this sudden surge of solar? A trio of enticing incentives – dwindling costs, increases in renewable mandates and a scheduled reduction in the solar investment credit tax (ITC) – are lighting the way for solar’s rise to the utility throne.   

But solar developers aren’t exactly walking on sunshine. An ever-evolving marketplace is complicating the development of new utility-scale solar farms. From project site selection to panel installation, navigating the dimly lit path of solar construction can be a daunting endeavor for solar project teams.

In today’s complex energy scene, contractor knowledge and experience in the current landscape are crucial for successful completion and operation of large-scale solar ventures.

Preliminary Procedures

Site selection, SCADA requirements, geotechnical investigation and equipment selection each play a decisive role in determining the viability of solar projects. By conducting thorough research and proactively planning before installation begins, developers greatly increase the economic viability of their solar project(s) for years to come.

Site selection – Permitting and environmental considerations, such as wildlife, plant species and cultural factors, must be accounted for prior to the project’s start. Environmental impact studies can serve to identify the most favorable sites to bypass permitting and environmental issues.

Site capacity and production goals often factor into site selection as well. When selecting a project site, a developer may seek a plot of land capable of hosting a specific capacity or energy production goal instead of one that considers the potential future needs. Conducting a site search that proactively accounts for future safety and efficiency requirements is a more reliable approach than one that considers solely present-day site capacity and production goals. This forward-thinking strategy allows the needs of both the construction crew and operations and management (O&M) team to be factored into planning and design.

Just as site capacity and production goals do not necessarily equate to operational success, the same can be said for plot size. Just because a proposed site is large enough to accommodate the desired PV generation capacity does not mean it meets the required operational imperatives.

Some specific examples of operational demands include:

  • Ample space between tracker rows for operations personnel to navigate arrays safely.
  • In arid climates, spacious accessways to enable pickups, trailers or water trucks to traverse the site periodically to wash and clean modules.
  • In areas of heavy vegetation growth, broad accessways for vegetation management and equipment.

SCADA requirements – Supervisory control and data acquisition system (SCADA) requirements often remain vague or receive little oversight until the later stages of a solar project. Projects that fail to address SCADA needs early tend to suffer change orders, or even worse, the costly retrofitting, standardizing and integration of a compatible SCADA platform.

SCADA specifications should be outlined prior to a request for proposal (RFP) to achieve a useful control system the first time. This proactive step enables the contractor to coordinate with the owner on the development of a detailed architecture that can be validated through factory acceptance tests.

Geotechnical surveillance – Subsurface conditions account for some of the most significant risks on a solar installation. Without an accurate geotechnical survey, engineers may make erroneous assumptions that can dramatically impact project costs and schedules. Obtaining detailed geotechnical information on a site within the preliminary design phase empowers engineers to make optimal assumptions for a project’s civil, structural and electrical design. A detailed “geotech” report often encompasses results from corrosivity testing, field and laboratory resistivity testing, soil borings and test pits.

Comprehensive geotech reports also shine light on quality pile design and installation requirements. The final report should include pile pull testing results for:

  • Both driven and pre-drilled piles, including compression, tensions and lateral loads
  • Groundwater information
  • Lateral and axial design parameters (i.e. L-Pile or A-Pile)
  • Design frost depth and how to address adfreeze (in which two objects adhere to each other via ice) stresses in pile design (only for colder climates)

All told, the owner runs several consequential risks when a preliminary or incomplete geotech report is used to crosscheck the contactor’s pile embedment depth assumptions. Thorough reports greatly reduce the risk of costly change orders that can sometimes result in seven-figure cost differentials.

In addition to pile embedment design recommendations, geo-tech reports should provide details on soil corrosivity – information that is essential for steel pile corrosion design – with measurements for chlorides, electrical resistance, organics, pH and sulfates. A qualified corrosion engineer’s interpretation of corrosion severity for concrete and steel, as well as corrosion rates for carbon and galvanized steel, should also be included in the final report. Unlike inverters and other project equipment that have a 15- to 20-year design life, piles cannot be upgraded or replaced at a reasonable cost. Therefore, piles should possess a corrosion design life that will last the duration of the project’s life span.

The pile installation process revolves around three central determinants: embedment length, total pile length and whether the piles are driven or pre-drilled. By noting all of these factors in the geotech report, contractors are able to develop a more accurate cost estimate and better define the pile installation schedule and the project’s progress overall.

Equipment selection – As one of the most integral components of any construction endeavor, equipment selection is key to ensuring project goals are achieved and target budgets are met. On a project site, this translates to procuring reliable equipment that will operate throughout the life of the project and performing due diligence on all equipment, including collaborating with manufacturers to define specifications and performance requirements.

Following procurement, rigorous equipment testing should be conducted to verify performance. Not all equipment can meet the industry’s most basic demands, as seen within the results of PV Evolution Labs’ May 2019 modules scorecard:

  • 33% of the products tested failed the arc fault test
  • 25% failed the humidity freeze test
  • 21% failed the damp heat test

Some utilities find themselves working with smaller, less-established manufacturers in order to meet construction schedules. These partnerships serve as another reminder of the necessity for design verification testing, which should be outlined in EPC and vendor contractual requirements.

Achieving Successful Installation

Once all preliminary research, site and equipment selection, and pre-construction testing have concluded, it’s finally time for solar installation.

Module installation and wire management –Improper module installation and poor wire management can lead to ground faults and performance issues. To bypass these potential problems, installations should always be completed according to the manufacturer’s requirements, a well-defined quality management procedure and in accordance with applicable codes. Asking the manufacturer to send a representative to a project site to confirm proper module installation can provide added value if the solar installation experiences production problems.

Proper cable tie selection and installation are equally important. UV-rated products are different from UV-stabilized ones – just because a cable tie is UV-rated does not mean it’s guaranteed a long operational life. Industry testing for UV-weathering is not standardized, so soil characteristics, climate and proximity to water should all be accounted for when determining cable tie’s moisture and chemical ratings.  

Multifaceted mockup rows – Constructing a complete row of solar installation as a mockup is one of the most effective ways to control project quality. This step delivers an abundance of benefits to various project stakeholders:

  • Subcontractors – The mockup sets a template for subcontractors as they complete the remainder of the project, particularly for crucial elements like module installation and wire management.
  • Owner, engineer and contractor – By providing the owner, engineer and contractor the opportunity to review the installation jointly, the mockup allows all three parties to provide feedback and align on quality control, cable management, safety, O&M needs and other issues.
  • Labor force – Since most solar projects are located in rural and/or remote locations, solar project contractors often recruit the majority of workers from the local labor force. Even if local laborers have considerable construction experience, it is highly unlikely they are versed in solar construction. The mockup row can serve as a valuable training tool for the labor force completing the installation. 

Reaping the Rewards of An EPC Project

Almost all utility-scale solar projects are completed using the EPC contracting approach. After proposals are solicited for an installation of a given size and the owner evaluates the options on the table, the owner selects the EPC contractor with the preferred solution. The contractor then holds complete responsibility for every aspect of project delivery.

In other cases, EPC teams are led by full-service design and construction firms that perform all project functions in-house. A single-source EPC approach is often the favored solar installation plan for a variety of reasons, including collaborative teams, consistent oversight and project continuity.

Today’s ideal industry and economic conditions for solar construction won’t last forever. As substantial tax credit programs for solar projects steadily deteriorate, experienced EPC firms will continue to provide efficient, comprehensive solutions for utilities seeking to complete solar installation in the near future. With the ability to navigate solar construction challenges, streamline schedules and deliver both a high-quality project and peace of mind for owners, EPC firms are illuminating the path to successful solar installation.

About the authors: Chad Cotter is a regional construction practice manager at Burns & McDonnell with nearly two decades of experience. His combined background in mechanical engineering and construction gives him a well-rounded understanding of the design-build and engineer-procure-construct (EPC) project delivery approach.

Russ Gentemann is a project manager for the Construction/Design-Build Group at Burns & McDonnell. His industrial market project experience includes successful completion of multiple EPC utility-scale solar projects. He has also led projects on coal-fired power plants and oil, gas and chemical facilities.