Photovoltaic (PV) panels are generating clean, green electricity on top of an existing hazardous waste site on the island of Oahu. Seven acres of land, once thought to be undevelopable, are now home to the island’s first utility-scale PV solar energy facility.
The U.S. Environmental Protection Agency halted dumping on the industrial disposal site in 1986. The site was then sealed under a plastic liner and thick mound of asphalt. Twenty-seven years later, a design and construction team has transformed the site into the Kapolei Sustainable Energy Park.
At the utility-scale solar field in Kapolei, Hawaii, the 1.18MW ground-mounted PV system generates enough power to supply 150 to 250 homes.
“Repurposing this land is very important to the future of Hawaii,” says Mark Cripe, vice president of Helix Electric, the electrical contracting firm working on the project.
Working together as a team
This project pioneered the first PV system feeding directly onto the HECO electric utility grid. Because a solar project of this size and complexity had not been previously accomplished on Oahu, it presented many unknown design challenges and interconnection requirements.
As such, the project required coordination and cooperation from all of the companies involved. Hawaii Electric Co. Inc. (HECO) first established its requirements on the utility side, and then Hoku Solar, the general contractor, and Helix Electric worked with Morikawa & Associates LLC, the design firm, to engineer the project. Team members took into account all of the requirements of the site, owner, and electric utility.
Before they could interconnect with the HECO grid, the companies had to develop an interconnection study and system protection settings for the primary medium-voltage equipment and 480V inverters.
Coordinating and scheduling work
Because of the sheer scale of the project and the work that needed to be done, the construction team worked simultaneously on multiple interdependent activities. This required a high level of detailed planning and coordination in order to execute the work smoothly and successfully.
For example, the distribution activities were happening concurrently with the installation of the PV field. On the PV field itself, workers were performing multiple tasks, including installing solar modules, stringing the DC wiring, and connecting the wiring from the combiner boxes back to the inverters.
The project had numerous repetitive work activities, and Helix Electric concentrated on making sure its electricians were focused on what they were doing from one day to the next. Peaking at roughly 25 employees, Helix Electric’s scope of work included assisting with engineering review and design, installing the ground-mounted ballasted racking system, providing and installing 4,200-plus solar modules, putting in all electrical DC and AC wiring, interconnecting directly to HECO 12kV electric utility grid, and handling the commissioning. Throughout the project, Helix focused on keeping its workers safe in the field.
“We wanted to make sure they were working safely, productively, and also at a level of quality that we expect,” Cripe says. “On this type of job, it’s easy to become complacent, and when you let your guard down, accidents can happen. We took safety very seriously, and the result was zero loss-time accidents.”
Complying with environmental restrictions
To successfully install the PV system, the companies had to follow many guidelines aimed at protecting the environment. One of the most significant challenges was that instead of building the PV system on a flat open field as in most utility-scale solar projects, the workers had to construct the system on top of an asphalt mound.
Because the cap protected the hazardous industrial waste contained beneath, the field workforce had to avoid penetrating or puncturing it in any way. For example, their construction equipment had to meet certain weight restrictions and feature tracks rather than hard, rubber wheels.
An independent environmental consultant continually monitored the condition of the asphalt cap throughout construction for excessive wear or damage. This consultant also monitored the underground activities required for the distribution portion of the project and sampled the soil conditions.
Shortly after preliminary excavation commenced, elevated levels of lead were discovered in the soil adjacent to the cap. Additional safety, monitoring, and abatement measures were then employed to complete the work in a safe and environmentally controlled manner.
Due to environmental findings, the companies had to be flexible and adaptable to changes in the design, particularly after the equipment was procured, says Lyman Morikowa, principal engineer for Morikowa & Associates in Pukalani, Hawaii. For example, the team had to redesign and relocate the 12.47kV electrical service from underground to overhead to minimize the need for excavation and handling after discovery of contamination.
The Hoku Solar and Morikawa & Associates, LLC team also worked on solving the non-penetration design challenges of the PV array field, equipment layout, and system grounding.
Because the sides of the cap were sloped, it also posed challenges in the safe handling of material on the site and installation of the racking and PV modules on the existing sloped surface. Because the protective asphalt cap could not be penetrated, Helix worked with the other firms to design a racking system that could be anchored to surface-mounted concrete ballasts.
By focusing on safe work practices and working together, the companies were able to complete the job in less than six months from start to finish. Because it was Oahu’s first electric utility-scale PV solar energy facility fed directly onto the HECO grid, the team had to address numerous technical challenges. Through hard work and pre-planning, however, the companies were able to take a hazardous waste site and transform it into a facility that will generate safe green energy for years to come.
Fischbach is a freelance writer and editor based in Overland Park, Kan. She can be reached at [email protected].