Gridflex seeks permit on 500-MW Maysville pumped storage project

Gridflex Energy LLC, on behalf of project company Maysville Pumped Storage LLC, on Jan. 10 filed with the Federal Energy Regulatory Commission a revised application for a preliminary permit for the Maysville Pumped Storage Project that reflects commission staff’s Jan. 4 request for clarification on the intake structure and the proposed phases of development. 

The Maysville project would be an underground pumped storage project utilizing water drawn from the Ohio River and a new artificial lower reservoir created within existing excavated underground mine space. As currently envisioned, the project would be developed in phases, initially using only the Ohio River as the source of water for generation, with up to two reservoirs constructed later to provide for greater flow and project generating capacity.

The lower reservoir would be constructed by installing concrete plugs in previously excavated panels within the Maysville underground mine. Five vertical power shafts would be constructed, each running down to individual penstocks and into the powerhouse constructed below the lower reservoir.

In Phase I, a submerged intake/outlet on the Ohio River would connect to a headrace leading to the first two shafts, each of these leading to a 100-MW unit in the powerhouse (for a total of 200 MW). In Phase II and III, up to two reservoirs would be constructed using two adjacent ravines located west of the surface operations of the existing mine and near the Ohio River. Low-pressure conduits would be constructed from these reservoirs to the remaining vertical shafts. Up to three additional 100-MW units would be constructed.

Equipment at the full built-out level would tentatively consist of five 100-MW, adjustable-speed reversible pump-turbines, totaling 500 MW of generating capacity. Annual projected energy production would be approximately 1,296,480 megawatt-hours, including ancillary services output. Maximum hydraulic head would be 767 feet using the Ohio River (Phase 1) and 975 feet using the reservoirs added in Phase II and III.

The project would interconnect with the PJM Interconnection system at a 345-kV bus at the Stuart Generating Station via a new two-mile, single-circuit 230-kV line, which would run a length of 2,800 feet under the Ohio River and approximately 8,000 feet above ground. A second gen-tie line, with a voltage of 138 kV and length of 2.3 miles, would follow an existing 69-kV path from the project site to the Plumville 138-kV substation.

Said the Jan. 10 filing: “The Project will be operated to provide firm capacity and ancillary services to the regional markets (PJM and/or MISO and/or TVA), and serve to support to the integration of new renewable resources being interconnected in these systems. It will also help to improve general grid reliability and the operational efficiency of generating units in these systems. The Project also makes beneficial use of excavated mine space.”

A project contact is: Matthew Shapiro, Chief Executive Officer, Gridflex Energy LLC, (208) 246-9925,

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.