Sheet Metal & Air Conditioning Contractors’ National Association

Hawaii Hotel Co-gen Plant Produces Electricity From Waste Heat

A new co-generation plant is supporting energy conservation and savings by producing electricity and hot water for a beachside hotel in Waikiki, Hawaii.

The Sheraton co-gen plant is the largest in Hawaii.SMACNA contractor Alaka’i Mechanical Corporation (AMC) of Honolulu has been working on the new co-generation and central plant upgrade at the Sheraton Waikiki Hotel in Honolulu since 2016. Completion of all phases is scheduled for early August 2018. AMC is a member of SMACNA’s newest chapter—SMACNA Hawaii.

“To my knowledge, this co-generation plant is the largest in the state, with a maximum capacity of about 2.2 megawatts (MW) when the two units are running,” said Darryl Kanno, AMC’s vice president- business development.

“In a nutshell, the co-generation equipment, electric generators, will burn synthetic natural gas (a gas fuel produced from fossil fuels such as lignite coal, oil shale, biofuels, or renewable electrical energy) to produce electricity for the hotel,” said Kanno. “The waste heat from burning the gas is then used to make hot and chilled water for the hotel. Waste heat from the absorption chillers’ condenser water will also be used for pool heating.”

A developer sold the idea of a co-gen project to the hotel owner and brought in Penn Power Group (PPG), who brought AMC onboard, Kanno said. “AMC, as the acting general contractor, is responsible for design-build and installation, with help from PPG.” PPG provided the equipment and chillers. AMC’s piece of the project was a little over $8 million, he said.

Phase one involved constructing a new hot water generation and storage plant in a new location. “The sheet metal work involved installing two new flues, one for each of the two existing boilers in new termination locations. The installs involved about 250 feet of 16-inch inside diameter (ID) flue, and various elbows and tees with 4-inch-thick insulation,” said Kanno. AMC installed Selkirk Metalbestos 316 inner and outer walls for the rerouted boiler exhaust flue.

IMG_4836-250x188The hot water storage tanks were removed in the second phase to make room for the new co-generation equipment. Sheet metal work in phase three included installing 16-inch ID flue from the co-generation units to the oxidation catalysts, heat exchangers, and silencer to the existing flue. Providing co-gen to the oxidation catalysts (OCs) involved about 102 feet of 16-inch ID flue and fittings with 4-inch-thick insulation.

In phase four, AMC installed a mechanical screen, also called architectural louvers, to conceal radiators on the roof that eject excess heat from the co-gen equipment. The fifth phase involved installing 8-foot-high, 4-inch-thick sound panels, which mitigates the noise generated by the co-generation units. Inside the enclosure, the sound is about 110 to 120 dBa (a-weighted decibels) with the two units running. Outside, the sound is about 85 to 90 dBa in four walls, each 25 feet long, and two doors for the enclosure along with intake ventilation ductwork from outdoors.

“The co-generation units are currently operational, generating electricity and producing hot water for the hotel,” said Kanno. The electric utility handled phase six, and AMC is now in the seventh phase, which involves replacing two 1,400-ton centrifugal chillers with two new 1,500-ton centrifugal chillers and a new 300- ton absorption chiller.

Sheraton Waikiki _060 250x167“There were so many challenges that accurate three-week schedules were not possible for a majority of the project and scheduling was constantly revised,” Kanno said of the complex project. Their primary challenge included making the least possible impact on the hotel, so it could remain operational throughout the work.

However, “having good subcontractors on this project made it a lot easier,” Kanno said.

Thanks to AMC’s co-generation installation, the Sheraton Hotel co-generators are humming along, creating electricity and hot water for its guests on Waikiki Beach.