Hawaiian Electric’s Kahe project to consist of three GE combustion turbines

The Kahe combined cycle (CC) project will be a 3×1 CC unit consisting of three General Electric 6F.03 combustion turbines (CTs) and three heat recovery steam generators (HRSGs), which will use the waste heat from the CTs to produce steam to be utilized in a new steam turbine generator.

The Kahe CC’s base capacity will be 358 MW, and for additional power production, the facility will be capable of utilizing wet compression technology during peak demand periods to add about 25 MW of capacity to the unit, totaling 383 MW, said Hawaiian Electric in a May 18 application for approval of this project filed with the Hawaii Public Utilities Commission.

Together with planned merger partner NextEra Energy (NYSE: NEE), Hawaiian Electric decided on this project, which involves a partiall repowering of the existing Kahe power plant. They first evaluated potential high capacity factor generation using the following criteria:

  • Lowest total (capital and operational) cost
  • High efficiency to minimize fuel cost
  • Operational flexibility to support renewables
  • Low emissions

That analysis showed that combined-cycle technologies are the best generating technologies available for high capacity factor service. These technologies provide the operational flexibility necessary to support a growing level of intermittent renewable resources. Incorporation ofthis type oftechnology could also be accomplished at a lower total cost compared to other generation options.

Having identified combined-cycle technologies as the best resource options, two alternative combined-cycle technologies were further evaluated: advanced combined-cycle units and aero-derivative combined-cycle units. It was determined that advanced combined-cycle units have the necessary operating characteristics, higher efficiencies, and the lowest total cost. In comparison, aero-derivative combined-cycles have higher total costs and lower efficiencies.

The next step in the analysis was screening various combined-cycle sizes and configurations. It was determined that an approximate 350 MW unit had the greatest overall savings for the customer. Two combined-cycle configurations designed to meet the optimal determined size were considered further: a configuration of three combined-cycle units, each with one CT and one HRSG, that supply steam to one steam turbine {i.e., three 1×1 CC units); and one combined-cycle unit with three combustion turbines, three heat recovery steam generators, and a single steam turbine {i.e., a 3×1 CC unit). The evaluation of these two configurations revealed that the 3×1 CC would save $136 million in total lifetime cost over the three 1×1 CC units. The 3×1 CC would save $48 million in capital construction costs, $21 million in maintenance costs, and $67 million in fuel cost over the unit life due to its more efficient heat rate.

The Kahe CC would be constructed upon approximately 15 acres at the Kahe Generating Station, in a portion of the currently unused valley to the north of the existing units. The Kahe site proved to have significant advantages over the Waiau site that was considered as an alternative site for a 3×1 CC unit. The primary advantage of the Kahe site is that existing unused land and infrastructure at the site can be employed, while allowing the existing Kahe 1,2, and 3 units to remain running for the majority of the construction period. In contrast, there was not enough unused land at the Waiau site to allow the existing units to run during the construction of the CC unit. This would have created reliability challenges for the system during the construction of the CC unit at Waiau.

Kahe Units 1,2 and 3 will be retired in July 2020. The new CC unit’s base heat rate using gas will be 6,965 Btu/kWh at an average ambient temperature of 86° F. The unit will have an estimated average forced outage factor of approximately 1.6% and an equivalent availability factor of 92.2%.

Fast ramping a key positive for this project

The Kahe CC will be a flexible, high performance generating unit. For instance, the Kahe Units 1, 2, and 3 have a combined ramp rate of 13 MW/minute. By comparison, the rate at which the Kahe CC unit will be able to change load is 35 MW/minute – at least a 270% improvement across a larger range of output. Consistent with its state-of-the-art design, the Kahe CC unit will provide enhanced reliability, because it will have the capability of bypassing the steam turbine, which in turn avoids the potential that a single contingency event would result in a loss of generation any greater than 145 MW. Additionally, a dump condenser will be included in the design, which will allow for the steam turbine and its main condenser to be taken offline for maintenance while still allowing for operation of the three combustion turbines.

The Kahe CC will be designed and permitted such that it can fire either natural gas or liquid fuels such as diesel and biofuels. As such, the Kahe CC unit is a significant component of the companies’ liquefied natural gas (LNG) import project. An application for the LNG project was also filed with the commission on May 18.

In order to realize the maximum savings associated with generation modernization, the company has submitted, contemporaneously with this application, a waiver request from competitive bidding requirements. This application for the Kahe CC assumes a favorable decision on the waiver and a schedule for the disposition of the application that would allow thirty-nine months for engineering and construction of the Kahe CC unit in order to achieve an in-service date of January 2021.

If the commission denies the waiver request, then the in-service date of the Kahe CC unit will be delayed to at least June 2021. Denial of the waiver would require a time consuming (and costly) Request for Proposal (RFP) process to be conducted, even though the Kahe CC is probably the best option, said the utility. Such a delay in the in-service date of the Kahe CC unit would cost customers (in terms of avoided costs) as much as $48 million to $77 million, the utility argued.

Said Hawaiian Electric: “Given the circumstances and the significant savings to be lost in the event of delay, the Company urges the Commission to grant the Waiver Request. Beyond disposition of the Waiver Request, the Company also notes that both the LNG Project and the Kahe CC described herein are conditioned on approval of the Proposed Merger [with NextEra Energy], filed in Docket No. 2015-0022. Construction of the Kahe CC unit is expected to commence in mid-2018, assuming that a waiver of the Competitive Bidding framework for the Kahe CC unit is granted by the Commission.”

The Kahe CC project cost, excluding Accumulated Funds Used During Construction (AFUDC) and interconnection costs, is estimated to be approximately $716 million, which equates to about $1,870/kW.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.