Hawaiian Electric Co. on May 16 asked the Hawaii Public Utilities Commission for approval to spend $170m on the 50-MW Schofield Generating Station (SGS) on O’ahu.
The utility noted that this project would move Hawaii closer to its 40% by 2030 renewables mandate by adding biomass capacity and by adding flexibility to Hawaii’s grid to allow more wind and solar integration.
At the commission’s direction, Hawaiian Electric said it will be filing its Power Supply Improvement Plan (PSIP) for O’ahu. The proposed project will be included as an integral component in the power supply plan as it is considered to be a foundational and necessary step for modernizing O’ahu’s generation fleet.
The project will have a generating capacity of 50 MW. More importantly, however, would be the project’s operational flexibility due to it being configured with six separate reciprocating engines each having a generating capacity of 8.4 MW. Each engine may be independently dispatched from 4 MW to 8.4 MW, resulting in a dispatch range for the project of 4 MW to 50 MW. Moreover, the project can be started from a de-energized and unsynchronized state to full capacity (i.e., 50 MW) within six minutes.
Each engine will be multi-fuel capable for maximum fuel optionality, including the ability to switch while operating between different liquid fuels and natural gas. The reciprocating engines will be very fuel efficient, and the project will operate at heat rates throughout its load range that are better than every other firm generating unit currently operating on the O’ahu grid.
The project would serve all Hawaiian Electric customers under “normal” operating conditions, and it would provide enhanced energy security and resilience for the island of O’ahu, the utility noted. All of O’ahu’s existing generating stations are located near the coast and are subject to major storm surges and tsunamis. Conversely, as the first generating station centrally located over eight miles from and approximately 900 feet above the sea, the proposed project would be immune to the coastal effects of tsunami and storm surge. The U.S. Army recognizes the benefits and energy security attributes of the project and, subject to Hawaiian Electric providing the energy security guarantees that the Army requires, is willing and able to provide the land necessary for the project and waive lease payments.
Under defined emergency conditions, the project will be able to provide power directly to the Army facilities of Schofield Barracks, Wheeler Army Airfield and Field Station Kunia. Self-contained with on-site fuel storage, rugged, and not requiring any seawater cooling or external supplies to operate, the project will be the most “survivable” generating station on O’ahu.
The project will also have the capability to blackstart the island’s grid by providing the power necessary to start other combustion turbine units at the company’s Waiau power plant via multiple redundant existing transmission paths.
Hawaiian Electric proposes the SGS project, in which Hawaiian Electric will finance, design, procure, and construct a firm, dispatchable 50-MW plant and the associated overhead 46-kV sub-transmission line, as well as make related modifications to existing grid infrastructure. The new 46-kV sub-transmission line will extend about 2.5 miles from the generating station to both the existing Wahiawa Substation and the existing Wahiawa-Mikilua 46-kV line. Upon completion, Hawaiian Electric will solely own and operate the project.
Fuels range from liquid biofuels to liquefied natural gas
The RICE technology selected for this project provides fuel optionality, since the engines are capable of running on a variety of liquid and gas fuels. As originally envisioned, this project had the capability to receive, store, and deliver only liquid fuels (biodiesel and diesel) to the engines, because natural gas was not anticipated to be available in adequate quantity until well after the project would be commissioned. It was anticipated that, when natural gas in the form of LNG became cost-effectively available, the capability to receive, store, and deliver natural gas would be added at that time as a separate project. For this reason, the project specification issued as part of the generating station request for proposals (RFP) did not require LNG capability, only the ability to incorporate it later. But then the utility found that LNG may be available more quickly that it first thought, so LNG was added to the project specs.
The SGS is anticipated to operate primarily as a peaking unit that will operate during the evening peak, and to a lesser extent during the morning peak. The total annual energy output is estimated to be 59 gigawatt hours per year, which corresponds to a capacity factor of about 13.4%. This energy will be generated using a fuel mix that consists of at least 50% biofuel, with a minimum biofuel consumption of 3.5 million gallons per year pursuant to Army requirements. The other fuel will be the most cost-effective, technically viable fuel available. If LNG is available, the company anticipates using it. If LNG is not yet available, the SGS will run on a biofuel blend in which biodiesel is mixed with diesel, until such time as natural gas becomes available.
The proposed in-service date for this project is in October 2017, with a November 2015 construction start pending receipt of needed regulatory approvals.
The total cost for the SGS Project is estimated to be $170m. There are two variables in the cost estimate that will directly affect the overall project cost and are dependent upon when full Notice to Proceed (NTP) is given to the EPC contractor and the engine manufacturer, Wartsila North America: escalation and the euro exchange rate. Hawaiian Electric said it has taken measures to minimize the effect these factors will have on overall project cost, but they are not totally within the control of the company.