Waste Management Plant Commits to Solar Power

The Honolulu Program of Waste Energy Recovery, or H-POWER, in Kapolei, West Oahu, generates up to 90 megawatts of energy for Hawaiian Electric Company — enough to meet nearly 8 percent of Oahu’s energy needs. The facility processes 700,000 tons of waste annually, which is combusted to generate steam, converted into electricity and sold to Hawaiian Electric for use by Oahu’s residents and businesses.

The city added solar photovoltaics (PV) to six existing rooftops at the City and County of Honolulu’s Waste-to-Energy Recovery facility operated by Covanta Honolulu Resource Recovery Venture (H-POWER). However, there wasn’t sufficient space to meet their full commitment of solar energy production at the facility, so a new metal “solar building” was constructed on the adjacent lot, which would house and provide the balance of solar power requirements.

Elevating the PV panels on rooftops would reduce shadowing from adjacent properties and maximize power generation, and was therefore more favorable to achieve reliable and consistent system performance.

In total, the project involved installing a 3-megawatt system — one of the largest rooftop solar projects in the state of Hawaii — consuming 290,181 square feet of rooftop space for the PV system. The system would offset some of H-POWER’s in-house demand of 7 megawatts to run the plant. 

A Varco Pruden steel building was selected as the product of choice for the structure of the “solar building” and for the facility’s rooftops. Taylor Metal Products trapezoidal rib metal roofing was chosen to replace existing roof panels for the six buildings at the H-POWER plant facility. S-5! solar attachments were chosen to secure the solar panels to the metal rooftops of all buildings for this project.

Numerous Challenges

The newly constructed metal “solar building” had to be designed with cost-effective solutions for the long-term both for the PV project and various recycling programs within the building. In addition, the metal roofs on the six buildings at H-POWER facility were more than 30 years old and in need of replacement.

Since the service life of a PV system is typically between 28 and 37 years, the new roof and the replacement roofs would need to meet the expected service life of the PV system. The entire project had to be completed within a tight timeframe and without disruption to H-POWER’s operations, as the complex is a key component of the island’s waste management infrastructure.

Metal was selected for this project because it was the lowest cost and best use option. The “solar building” structure is steel framed with metal roofing and siding, supported by a concrete slab on a grade foundation. It is enclosed with overhead doorways and man doors.

Metal roofing was chosen for all the roofs as it provides an ideal platform for mounting PV and features a service life that exceeds that of the solar PV system. A standing seam metal roof was chosen for the “solar building” since it was also easier and less expensive to mount solar PV to this metal roof type over any other.

The S-5-S Mini clamp was selected as the preferred attachment method to secure solar modules to the roof of the new “solar building” to allow a penetration-free attachment for the solar racking system. S-5!’s VersaGard was selected to secure PV racking to the newly replaced trapezoidal exposed-fastened purlin bearing rib (PBR) metal roofs at the Covanta Honolulu plant facility.

The H-POWER plant and adjacent “solar building” utilized metal building components to achieve lasting performance and durability, while allowing the city to process and manage the island’s solid waste, converting trash to power, and to further explore recycling and renewable efforts for a more sustainable Hawaii. 

TEAM

Architect: HDR, Honolulu, Hawaii, hdrinc.com

Solar Contractors: Engie, engie-na.com, and Hawaii Unified Industries, Waianae, Hawaii, hawaiiunified.com

MATERIALS

Steel Building: Varco Pruden Buildings, varcopruden.com

Roof Profiles: Taylor Metal Products, taylormetal.com, and MBCI, mbci.com

Solar Attachments: VersaGard and S-5-S Mini, S-5!, s-5.com