Besides being the fuel source for a new combined-cycle unit at the Kahe power plant, the Hawaiian Electric Companies plan to convert several existing oil-fired units to dual-fuel capability in order to take advantage of new liquefied natural gas (LNG) imports.
The Hawaiian Electric Companies applied May 18 at the Hawaii Public Utilities Commission for approval of a plan to buy LNG from Fortis Inc. that will be imported from British Columbia. That LNG would be brought by ship to a central bay, then be transferred from the ships to smaller vessels that would distribute it to Hawaiian islands where there are power plants to burn it.
Providing supporting testimony about the dual-fuel conversions was Robert C. Isler, Manager of the Generation Project Development department of Hawaiian Electric. He was testifying for Hawaiian Electric, Hawaii Electric Light and Maui Electric (collectively called the Hawaiian Electric Companies).
The plan is to use natural gas in the following existing units:
- Kahe Unit 5, 140 MW, owned by Hawaiian Electric;
- Kahe Unit 6, 140 MW, Hawaiian Electric;
- Kalaeloa, 208 MW, owned by KPLP;
- Maalaea 14/16, 58 MW, Maui Electric;
- Maalaea 17/19, 58 MW, Maui Electric;
- Keahole CT-4/CT-5, 56 MW, Hawaii Electric Light; and
- Hamakua, 60 MW, Hamakua Energy Partners.
These plants consist of:
- Kahe Generating Station: Kahe 5 and Kahe 6, which are steam boilers with an output totaling 280 MW (nominal), will be converted to use natural gas in addition to low sulfur fuel oil (LSEO). Kahe 5 and 6 will be converted such that they will be able to fire both natural gas and liquid fuels independently or simultaneously, as necessary.
- Kalaeloa Partners LP (KPLP): Two combustion turbines coupled with an associated steam turbine for a total output of 208 MW (nominal), will be converted to use natural gas. These turbines currently fire on LSEO and will be converted to allow firing ofnatural gas or LSEO independently. Simultaneous firing of natural gas and LSEO in these combustion turbines will not be possible. KPLP is an independent power producer (IPP) generally responsible for its unit conversions. As such, the cost to convert these units is not included in any company-owned unit conversion work to be performed.
- Maalaea Generating Station: Units M-14, M-16, M-17 and M-19, which are four combustion turbines with a total output of 80 MW (nominal), will be converted to use natural gas. When coupled with their associated steam turbines in combined cycle operation, the total output is 116 MW. These turbines currently fire on diesel and will be converted to allow firing of natural gas or diesel independently. Simultaneous firing of natural gas and diesel in these combustion turbines will not be possible.
- Keahole Generating Station: Units CT-4 and CT-5, which are two combustion turbines with a total output of 40 MW (nominal), will be converted to use natural gas. When coupled with their associated steam turbine in combined cycle operation, the total output is 56 MW. These turbines currently fire on diesel and will be converted to allow firing of natural gas or diesel independently. Simultaneous firing of natural gas and diesel in these combustion turbines will not be possible.
- Hamakua Energy Partners (HEP): Two combustion turbines with a total output of 40 MW (nominal), will be converted to use natural gas. When coupled with their associated steam turbine in combined cycle operation, the total output is 60 MW. These turbines currently fire on naphtha or diesel and will be converted to allow firing of natural gas, naphtha or diesel independently. Simultaneous firing of natural gas and naphtha/diesel in these combustion turbines will not be possible. Although HEP is an IPP and generally responsible for its unit conversions, the companies have provided an estimate of capital expenditures for unit conversions for this facility, considering Hawaii Electric Light is seeking approval to acquire HEP.
The decision on what units to convert was based upon the results of production simulations, which analyzed the most cost-effective means of distributing the targeted volume of 0.8 million tonnes per annum (mtpa) of LNG across the generation fleet. This analysis included the additional capital costs of converting existing units to use LNG as a fuel source and building regasification facilities at these generating stations.
In general, the analysis showed that following the unit conversions of the combined cyle units on Maui and the island of Hawaii, the most cost-effective overall plan involves maximizing LNG use at those locations. Therefore, the intent is to maximize LNG on those islands with the remainder ofthe LNG targeted for use on Oahu. The production simulations indicate that using LNG at KPLP and Kahe will consume the remainder of the 0.8 mtpa and therefore, the Waiau Generating Station will not be targeted for LNG consumption.
Since Kahe 1, 2, and 3 are designated for replacement with the addition of a 383-MW combined cycle unit at Kahe, they will not be converted to use LNG. Additionally, since Kahe 4 is slated for retirement soon after the LNG is available and because it is not needed to consume the contracted LNG volumes, Kahe 4 will not be converted to use LNG. Thus, the only units at the Kahe Generating Station that are anticipated to operate for an extended period following delivery of LNG (i.e., the new 383 MW 3×1 combined cycle plant), as well as the existing Kahe 5 and 6) will be designed or converted to use LNG.
LNG to be regasified at each converted power plant
The companies’ LNG infrastructure plans encompass the receipt, storage, regasification and utilization of LNG at Kahe, Maalaea, Keahole, and HEP. Specific activities at each generation station include installation of new equipment to receive, store and regasify the LNG, and the adaptation of the existing generating units to allow for gas utilization.
A few of the specific adaptations contemplated include:
- a fire-safe isolation valve will be installed for each generating unit and will serve as the boundary between the LNG facility and the unit;
- boiler conversions will include new burner front plates (with gas manifolds to direct gas to multiple injectors), gas injection nozzles, flame detectors for gas and oil firing, oil gun extensions and automatic air register operators (or compartment damper operators);
- combustion turbine conversions will include a change-out of the existing combustor section, installation of gas metering and safety shutoff valves, and upgrades to the turbine control system to add gas firing capability; and
- a Burner Management System (BMS) will be added to each generating unit, and will be housed in the existing control rooms and in several new BMS control cabinets. The BMS for each unit will supervise safe operation ofthe new gas firing system and the converted oil firing system.
With regard to the converted combined cycle combustion turbines at Maalaea, these flexible and efficient units cost-effectively provide the support services needed to operate in conjunction with high levels of as-available renewable generation. Thus, current plans are to maintain operation of these units indefinitely. As for Kahe units 5 and 6, there are currently no projected retirement plans for these units if LNG is available.
As it relates to HEP, Hawaii Electric Light has submitted a request for approval to allow it to purchase HEP’s 60-MW combined cycle plant and its related assets. If approved, this unit will continue to bring significant benefits to the fleet. As it stands, the HEP unit is a reliable, flexible firm capacity resource that continues to be critical in meeting the supply and system security needs with reasonable energy costs, Isler wrote. In addition, the company anticipates economic and system reliability improvements by adding a steam bypass system. This addition will permit faster startups in simple cycle mode, providing improved system benefits associated with increasing variable renewable energy, and reducing startup costs. With the conversion to burn clean, cheaper LNG, the HEP unit will support a transition to 100% renewable energy by 2050 at a lower cost.
With regard to Units CT-4 and CT-5 at Keahole, these flexible and efficient units cost-effectively provide the support services needed to operate in conjunction with high levels of as-available renewable generation. Moreover, because of voltage and transmission security constraints, current planning reflects a need to maintain operation of a unit at Keahole. Therefore, the Keahole units remain in planning projections for the current planning period.
As for KPLP, the combined cycle design of this unit has the operational flexibility required to support the needs of the renewable fleet. The existing purchase power agreement (PPA) for KPLP is, however, restrictive and does not allow the companies to operate the plant with the flexibility that will be required in the future, Isler said. “We are engaged in efforts to come to an arrangement that will provide us with the ability to operate this plant to more closely align with design limits that would enable the facility to better meet the support needs of the future renewable fleet,” he added. “However, should the PPA expire and KPLP cease to provide firm capacity, we might seek additional capacity by deferring future deactivation of units, increasing demand response programs, optimizing maintenance schedules, reactivating currently deactivated units, or acquiring additional firm capacity and seek approval to convert some additional units to natural gas.”