EPA grants permit for Texas gas plant, compressed air energy storage project

The U.S. Environmental Protection Agency (EPA) on April 14 issued a final greenhouse gas (GHG) prevention of significant deterioration (PSD) construction permit to Apex Matagorda Energy Center LLC for a 317 MW power plant that would store air underground and then release it during peak demand periods to support the electrical grid.

“We are working closely with business to protect both our environment and our economy,” said EPA Regional Administrator Ron Curry. “This permit demonstrates how business can save energy, reduce emissions, and take decisive steps toward a low-carbon future.”

The energy from stored compressed high pressure air will be supplemented with natural gas-fired combustion turbines to produce electricity during off-peak hours. The facility also aims to enhance the performance of renewable and conventional fossil fuel generation.

In June 2010, EPA finalized national GHG regulations, which specify that beginning on Jan. 2, 2011, projects that increase GHG emissions substantially will require an air permit.

Texas is working to replace a federal implementation plan with its own state program, which will eliminate the need for businesses to seek air permits from EPA. EPA has finalized over 32 GHG permits in Texas, proposed an additional 11 permits, and currently has over 30 additional GHG permit applications under development in Texas.

“APEX Matagorda Energy Center, LLC (APEX) plans to construct the Matagorda Energy Center, a 317-megawatt (MW) Compressed Air Energy Storage (CAES) facility located in Matagorda County, Texas (the Project),” said the 2012 air permit application. “CAES is a commercially available, economically attractive form of bulk energy storage for the electricity grid. The proposed Matagorda Energy Center will produce electricity by compressing air during off-peak demand periods for subsequent use in generating electricity during peak demand periods. This facility has the unique capability of providing bulk energy storage, which enhances the performance of both renewable (wind and solar facilities) and conventional fossil fuel energy generation.

Worldwide, two CAES plants, the McIntosh plant in Alabama and the Huntorf facility in Germany, have operated successfully for over 20 years.

“The CAES technology involves two major processes: (1) air compression and storage and (2) air release for electricity generation. During the air compression and storage process, electric motor-driven compressors are used to inject air into an underground cavern (or other storage media) for storage under high pressure. The storage cavern for the Matagorda Energy Center will be created by leaching a void space in an underground salt formation (the Markham Dome) located directly beneath the plant site. The Matagorda Energy Center storage cavern is expected to operate over a wellhead pressure range of approximately 1,900 to 2,830 pounds per square inch absolute (psia) (static pressure range). Electricity is generated by releasing the high-pressure air, heating the air with natural gas, and expanding it through sequential turbines (expanders), which in turn drive an electrical generator. When full, the inventory of stored air will support approximately 100 hours of generation at full-rated generation output without recharge.”

The compression and expansion equipment for the McIntosh Plant was supplied by Dresser-Rand. Notwithstanding the absence of a follow-on CAES project (subsequent to installation of the McIntosh facility), Dresser-Rand has maintained its commercial offering of CAES technology, the application noted. Dresser-Rand is the only equipment manufacturer offering an integrated CAES design, along with performance guarantees across the compression and generation functions, it added.

The Matagorda Energy Center will consist of two Dresser-Rand expansion turbine/generation (ETG) trains, each rated at 158.34 MW output at full load. The total capacity of the plant will thus be approximately 317 MW. There will be two compression trains installed, each driven by an electrical motor of 150 MW (nominal) power rating. Two sets of cooling towers will be installed to reject heat produced during compression.

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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.

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