# Guernsey Power Station

Guernsey Power Station is a privately owned gas-fired power plant located in Guernsey County, Ohio south of Byesville in the heart of the Utica and Marcellus shale region. It generates 1.875 GW of power, currently the 67th largest power station in the United States.
The electric generating facility sells energy and capacity into the Pennsylvania-New Jersey-Maryland Interconnection (PJM) market. PJM is the regional transmission organization that coordinates the movement of wholesale electricity in 13 states, including Ohio.
The facility uses three GE advanced gas turbines, producing electricity equivalent to the power needs of approximately 1.4 million homes. Plant construction cost $1.7 billion and at that time (anno 2021) was:
* the United States' largest natural-gas powered plant built in a single phase and
* the United States' largest plant using the single shaft combined-cycle configuration, employing dual turbine generator technology, first stage being natural gas-powered, then waste heat steam-powered.

## History

The Guernsey Power Station, LLC (GPS) is a commercial operation developed by Apex Power Group, LLC, formed in 2007, and Caithness Energy. Caithness Energy, L.L.C. is a privately held IPP having completed 54 power plant projects prior to this venture. Gemma Power Systems, a subsidiary of Argan, Inc., was responsible for engineering, procurement and construction of the plant. Caithness Energy is the on-going GPS asset manager.
Key to GPS' location in Valley Township was access to Utica and Marcellus shale natural gas, offering a price competitive, environmentally friendly fuel source. The power plant sits atop a depleted former coal mine, its acreage transected by the Rockies Express East natural gas pipeline and near AEP Ohio (AEP)'s Kammer–Vassell overhead transmission lines linking with PJM's 765 kV interstate network, providing convenient commercial tie-ins.
In Spring 2016, Apex Power Group, LLC presented public meetings to Guernsey County residents explaining the GPS project. Construction was expected to create up to 1,000 temporary jobs with taxes paid benefitting the local community. Plans were included to fund new buildings at Byesville, Ohio's Meadowbrook High School. Rolling Hills school district officials planned this upgrade after developers agreed future GPS tax revenues would pay the district’s 40% share of a contract with the Ohio Facilities Construction Commission, local taxpayers thus having no tax burden for Meadowbrook's new construction.
Regulatory filings were submitted in 2016 for construction of a natural gas-fired power plant capable of generating 1100 megawatts, using two high-efficiency combustion turbines. Plans were subsequentially postponed during which time the project's scope increased to include a third turbine, raising total capacity to 1.875 GW maximum output. On January 31, 2019, GPS authorized Gemma to start preliminary design and site preparation activities. Site prep was allocated six months' time and 10-12 % of the entire project budget.
CTL Engineering Inc. of Morgantown, West Virginia, planned the drilling grid patterns required for site stabilization per Ohio Environmental Protection Agency’s Underground Injection Control (UIC) Program. Two separate grids were needed on the 118-acre tract, foundation preparations for the power generating facility and a new off-site AEP 765KV switchyard. Howard Concrete Pumping provided mine mitigation, injecting approximately 200,000 cubic yards of grout into acres of subterranean cavities, leavings of century-old underground mining activities.
In May 2019, the Federal Energy Regulatory Commission approved the request and by September 2019 three GE 7HA.02 gas turbines had been ordered. Construction began 3rd quarter 2019. GPS developers paid for extension of municipal water and sewer lines from Byesville to the site, GPS to subsequently purchase those services from the village. Connection between the plant and onsite 42" natural gas pipeline was subcontracted to Aspire Energy Express LLC, an Ohio subsidiary of Chesapeake Utilities Corporation. The branch connection was designed to provide up to 300,000 Dekatherms/day (~ 300,200 MMBtu/day) with end-point metering and pressure regulation. Baker Concrete Construction provided foundations for the new construction.
On June 3, 2020, AEP sent update notifications to Guernsey County residents, both contiguous and at large, of GPS' Kammer-Vassell 765 kV Transmission Line tie-in. New transmission towers and lines would be constructed within AEP's existing right-of-way from the preexisting lines to GPS' site, beginning in fall 2020 and concluding summer 2021.
In June 2020, local union construction workers protested the hiring of out-of-state non-union workers instead of the completely local workforce promised. A company spokesperson denied the allegations. In May 2021, as construction neared 50% completion, Caithness Energy's senior Engineering VP reported 900 workers currently on site with about 70% being regional, from the tri-state Ohio, West Virginia and Pennsylvania area.
EPC Services Company, a subsidiary of Electrical Consultants Inc., provided design-build support for the plant's onsite switchyard, where 230 kV lines from the turbines merge into a collector bus and are stepped-up to 765 kV via auto transformers. Local Derwent-based Bi-Con Engineering, LLC, installed metering stations. GPS' switchyard output feeds a new AEP substation located on a 1200’ x 500’ pad near the plant, Aka Guernsey 765 kV Switching Station, which then connects via two 0.3-mile 765-kV transmission line sections to the east- and west-bound legs of the Kammer–Vassell line, respectively. (The Kammer substation lies SW of Wheeling, West Virginia; Vassell, N of Columbus, Ohio). All tie-in and substation expenses were funded by GPS' developers with ownership transferred to AEP upon completion.
GPS began live operation in February 2023 and commercial operation on April 7, 2023. Its construction phase provided an average of 300 jobs with highs of 1,000 during construction peaks. Its ongoing 24/7 in-service operation requires 29 permanent high-tech jobs to maintain operation. Additional labor for scheduled spring and fall shutdowns will require between 100–300 contractor employees on an ongoing semiannual basis for maintenance and reequipping.

## Operation

The GPS facility is a scaled system of three identical power units, each employing a GE 7HA.02 gas turbine with a GE W84 generator and a GE STF-A650 steam turbine paired with a water/hydrogen cooled generator, all power train components arranged on a single shared power shaft. The 7HA.02 combustion turbine is equipped with evaporative inlet cooling, selective catalytic reduction for NOx reduction, and oxidation catalysts to minimize CO and VOC emissions. The outdoor located GE triple pressure Heat Recovery Steam Generator (HRSG) powers the STF-A650 turbine. The HRSG is also equipped for supplemental natural gas firing to boost steam generation and startup time, allowing the facility to supply 300 megawatts of power to PJM's grid within 10 minutes notice.
The plant's closed-loop cooling system uses dry air cooling vs. conventional water-cooled technology, reducing facility water consumption by 90 to 95%. The air-cooled condensers were supplied by SPG Dry Cooling of Brussels, Belgium." Water for facility operation is provided by the village of Byesville with wastewater being returned for processing, the arrangement having a 20-year renewable contract.
GPS developers contracted the facility's first 5 years of operation to EthosEnergy, headquartered in Houston, Texas, responsible for recruiting and hiring all operation and maintenance staff.
Because of its near 64% combined-cycle efficiency, GPS is anticipated to operate year-round as a PJM base load supplier. Plant maximum capacity can use up to 160,000 MMBtu (1 million British thermal units) or 1,000 MCF (volume of 1,000 cubic feet) per day. GPS' 2024 annual operation generated 10.9 TWh power from 77.0 M MMBtu fuel consumption.

## Environmental and social consequences

GPS was able to have all of the large, heavy equipment delivered to the site via adjacent rail lines operated by the Byesville Scenic Railway, reducing impact to local roadways and traffic disruptions in nearby Byesville.
Site preparation, grading for GPS' foundation, altered preexisting surface water flow. Post rainfall, water runoff from the site began flooding neighboring properties. The Ohio EPA investigated, issuing two violation notices to Gemma Power Systems for erosion and sediment run off. A sediment settling pond was required and functioning surface skimmers needed at egress points. Mine mitigation required drilling injection wells every 25 feet over the site, filling them with toxic coal ash. GPS was authorized the use of a grout blend consisting of water, Portland Cement, fly ash and sand. Filling the mine raised the local water table, contaminating neighbor's water wells. Water testing found contaminates associated with the use of fracking waste water- methane, toluene, and benzene.
Neighbors report ongoing noise bursts from the power plant. High noise events are associated with unit restarts, HRSG steam blows while running in bypass mode. GPS implemented several mitigation measures to minimize sound levels during construction, including the erection of a temporary sound barrier wall on the east side of the facility. Once the facility completed commissioning, normal sound levels were anticipated to be substantially less than during the construction period. Sporadic high noise events still occurred during 2024, being associated with random mechanical equipment issues and scheduled electrical equipment repairs rotating between all three units.