US coal-reliant grids meet summer reserve margins

OREANDA-NEWS. May 18, 2015. US power grids most reliant on coal generation will have sufficient reserve margins to meet peak load this summer despite massive capacity retirements, the US electric grid reliability agency said.

But the North American Electric Reliability Corp. and grid operators across the US are seeing a potentially greater challenge in 2016 when power plants that won a one-year reprieve from the federal mercury and air toxics rule have to shut down ahead of the summer cooling season when electricity demand peaks.

The Midcontinent Independent System Operator (MISO) grid is projected to have an 18pc reserve margin, above the required 14.3pc, according to the summer 2015 assessment released today by the US reliability watchdog. Coal in June-August 2014 accounted for 60pc of total generation on that grid that covers 15 states from Minnesota to the Gulf coast and is the second largest US grid after PJM.

Most coal retirements on the midcontinent's primary grid are expected to take place in April 2016. Reserve margins across the midwestern portion of MISO will fall significantly. Michigan's lower peninsula is particularly affected, as installed capacity there after April 2016 will be 3GW lower than required.

The 13-state PJM regional transmission organization is projected to have a 19.3pc reserve margin, above the required 15.6pc, despite the planned retirement of almost 8GW of coal resources by 1 June. Coal in summer 2014 accounted for 42pc of generation on that grid.

The Southwest Power Pool's projected summer margin is the highest among its eastern peers at 35pc, above the 13.6pc target. Coal last year accounted for 59pc of generation in that grid that covers nine states in the Gulf coast, southwest and Plains regions.

The projected reserve margin in the Electric Reliability Council of Texas is 16.24pc, which is higher than the 13.75pc goal. But the projection reflects the expected start of service of two gas-fired plants with about a gigawatt of combined capacity. Coal last summer provided 35pc of generation on the Texas primary grid, second to gas' 45pc share. Coal burn in Texas in recent months is below historical norms.