Converting to Gas Generation is No Slam Dunk

Issue 1 and Volume 121.

By Joe Rubino, principal scientist/department manager, environmental/urban design practice, Stanley Consultants

As the country makes its inexorable move from coal to natural gas electricity production, the headlines are filled with power plant conversion announcements. Those utilities considering fuel conversions should understand that several obstacles potentially stand in the way to obtaining environmental permits, and that planning needs to start three years or more in advance.

From 2015 to 2040, natural gas consumption will rise 1 percent per year, the Energy Information Association predicts. From 2016 to 2018 alone, nearly 19,000 MW of gas-fired power will be commissioned in the Unites States. Gas is setting power generation records, accounting for 33.5 percent during the first half of 2016, compared to coal’s 28 percent. With shale fracking production stabilized, gas is no longer the wild hare of the oil patch. Combining low prices and plentiful supply with more stringent emissions standards, cleaner burning gas is on every utility manager’s mind.

Crafting a road map to permitting and building a gas-fired plant should also be on the utility manager’s mind. It requires multiple permitting steps and long-lead analyses that have to be funded and planned for as part of the capital project execution. And finally, the general public isn’t always convinced that natural gas is viable and in their best interests.

New Gas Plant Modeling Scenario Shows Likely Regulations

Gas-fired power plants are affected by three general permitting challenges. They include the Environmental Protection Agency’s (EPA) 316(b) rule that regulates how utilities draw and use water in their cooling processes; federal air pollution standards, and local government permitting.

In order to illustrate typical permitting challenges, Stanley Consultants developed a model for a fictitious gas-fired combined cycle plant of 500 MW to be built in the Midwest. The scenario featured a standard vendor turbine package in a 2×1 arrangement with a heat recovery steam generator (HRSG), cooling tower, and evaporative coolers. The model assumed 1 percent blowdown and no duct firing in the HRSG. The water consumption rate predicted was 889 Kilo-Pascals per hour, which equates to 2,560,320 gallons per day.

316(b) Requirements

Under Phase I of the 316(b) rule, a new power plant must implement measures to reduce impingement and entrainment at facilities which require a NPDES permit, have design intake rates of greater than 2 million gallons per day (MGD), and use at least 25 percent of the water withdrawn for cooling purposes. It’s not difficult to meet these thresholds. Say, for example, our fictitious plant did not have a cooling tower and relied on once-through cooling. Our model calculated a water use approaching 200 MGD.

Two Section 316(b) compliance tracks present different levels of compliance depending on whether you are using a cooling tower (Track 1) or alternate methods of complying with the regulatory standards (Track 2). Both tracks require meeting technical criteria for the water intake structures; however Track 2 involves a source water biological study. Both tracks involve long lead items because they require technology studies. In the case of Track 2, it also takes two years to gather information on aquatic life and the ecosystem, and project the extent of impact to the ecosystem.

Air Quality

Air quality standards play a role in gas-fired power plants. In 2015, the EPA strengthened the ozone standard from 75 to 70 parts per billion. This may not seem like a lot, but it could lead to significant cost increases for a new plant, as natural gas combustion is a source of NOx and VOC emissions.

Lowest achievable emission rate (LAER) technology is required in plant design. The severity of a nonattainment status will require emission offsets so that there is a greater reduction of pollution overall. It can easily take nine months to permit the LAER determination.

Local Permitting

Finally, local permitting is required to build the plant, bring in construction equipment, and deal with dust and traffic issues. Certain permits require a period of public comment. If there is known resistance, outside help will be needed to address stakeholder concerns. Gas pipelines and transmission are another major concern and frequently the target of opposition.

Gas-fired plants offer many benefits but are no slam dunk. A comprehensive plan will help operators avoid costly issues down the road.