Cooperative Energy on March 4 filed with the Mississippi Public Service Commission a petition to amend its certificate of public convenience and necessity to allow Cooperative Energy to own, install, operate, and maintain the Morrow Repower Project.
As noted in the petition, the commission in November 1973 issued to Cooperative Energy a certificate of public convenience and necessity authorizing it to build, own, operate, and maintain a coal-fired, steam-electric generating plant near Purvis, in Lamar County, with two turbine generating units, each having a maximum expected net capability of about 180 MW. That generating station later became known as the R.D. Morrow, Sr. Generating Station – referred to as Plant Morrow.
Cooperative Energy added that it built Plant Morrow and began operating the facility in 1978, where it continued operation until recently, wherein the decision was made to retire the facility.
Cooperative Energy noted that it dispatches all owned generating units into the Midcontinent ISO (MISO) market, in which units are dispatched on a day-ahead basis and in real time, as needed. Units are bid into the market and dispatched primarily based upon economics. Cooperative Energy also said that the original coal-fired steam units at Plant Morrow were not competitive in the MISO market environment, and that the units required 36 hours to reach full load from a cold start, making day-ahead and real-time market decisions impossible.
The rising cost of delivered coal and the low cost of competing natural gas-fired market resources, coupled with the inefficiency of the dated Plant Morrow technology made the units uneconomical to operate, Cooperative Energy said. Considering the dispatch cost and the need for large investments in component repairs and replacements on the coal-related assets, the decision was made to retire the two coal-fired steam units, effective Dec. 31, 2018, and convert the plant to a natural gas-fired, combined cycle facility, Cooperative Energy said.
Cooperative Energy noted that it conducted a power supply options study in 2016 that contemplated the most economical solution to maintain adequate generation resources over the long-term future. Considering the forecast load growth among the 11 member-owner distribution cooperatives and a number of other industry related forecasts, retiring Plant Morrow on coal and repowering the units with natural gas-fired combustion turbine generators (CTG) and heat recovery steam generators (HRSG) was identified as being among the most beneficial options to the members and Cooperative Energy, Cooperative Energy said.
The scope of work to repower Plant Morrow – referred to as the Morrow Repower Project – consists of demolishing all coal handling, processing and burning equipment and systems, including the coal-train unloading trestle; the flue gas treatment equipment and systems required for coal-fired operation will also be demolished.
Cooperative Energy added that within the general footprint of the demolished assets, one new gas-fired CTG would be installed. The CTG would be coupled with a new HRSG that would utilize CTG exhaust heat to generate superheated steam to drive the existing unit 1 steam turbine generator (STG).
Cooperative Energy also noted that the repowered combined cycle unit would produce about 550 MW of electric power at an improved heat rate of about 6,500 Btu/kWh. The advanced class combustion turbine selected is the Siemens 9000HL, which is rated at about 400 MW. Cooperative Energy added that the HRSG would be manufactured and supplied by Nooter/Eriksen. The existing steam turbine generator is expected to produce about 150 MW of electric power in the combined cycle configuration.
Cooperative Energy added that converting Plant Morrow to a natural gas-fired, combined cycle unit via the Morrow Repower Project would allow for reuse of the existing steam turbine-related assets, minimizing capital cost and increasing efficiency, while reducing air emissions rates at the site. The modified unit would be more operationally flexible and competitive in the MISO market, Cooperative Energy said.
As a result of the increase in power output at Plant Morrow from about 408 MW to 550 MW, some additional high-voltage transmission lines and substation upgrades would be required, Cooperative Energy said, adding that all upgrades are subject to change due to the MISO Generator Interconnection Agreement (GIA) process results.
Internal analyses indicate that the existing Morrow 161-kV substation would be demolished and rebuilt with increased capacity and additional bays to accommodate system improvements necessary to support the increased generation of the plant. Cooperative Energy also said that about five miles of new 161-kV transmission line would be built from Plant Morrow to the Purvis bulk substation, in addition to 161-kV breaker upgrades at Purvis Bulk necessary to achieve additional capacity on existing transmission lines.
The total installed cost is estimated to be $442m, Cooperative Energy said.
The Morrow Repower Project is needed and required in order for Cooperative Energy to have the required supply of power to serve the present and immediately foreseeable requirements of its members, Cooperative Energy said.
Among other things, Cooperative Energy said that it requests a waiver of the requirement of Appendix “A,” Schedule 3, Item 7, of the procedural rules to allow Cooperative Energy to not file with the petition a complete set of engineering plans and specifications for the Morrow Repower Project. Cooperative Energy said that upon request, it would make such complete set of plans and specifications available, when such information is completed and available.