With low gas prices and renewable generation boosting demand and capacity factors for combined cycle plants, plant operators are being called upon to squeeze out every last megawatt from their systems. Fortunately, there have never been more ways to do it. Here are some you may not have thought of.
Gas-fired power is booming—even more than expected. For only the second time ever, but also the second time this year, gas generated more electricity in a month in the U.S. than coal. According to statistics from the Energy Information Administration (EIA), in July 2015 coal generated 139 TWh, while natural gas generated 140 TWh. Those statistics are a stark break from 2014, when coal produced 150 TWh and gas was responsible for only 114 TWh.
While coal remained in the lead with a 34.5%-to-31.1% advantage in the power mix through July, those numbers represent a fairly substantial departure from EIA predictions. In its Annual Energy Outlook this year, the EIA predicted gas would reach a 31% share—in 2040.
With gas-fired plants being called upon to shoulder an ever-growing share of the power mix, plant owners are looking for more and better ways to squeeze extra performance out of their equipment, without breaking the bank.
While gas turbine manufacturers such as GE, Siemens, and Mitsubishi-Hitachi Power Systems offer a selection of upgrade packages to improve performance, these kinds of choices are both expensive and require significant down time. For plants that are not in the position to undertake costly outages and upgrades, and those newer plants already operating state-of-the-art equipment, there are still some ways to tweak out a few extra kilowatts.
Jeff Fassett of IEM Energy Consultants, who spoke to POWER in October, recommended that plant operators think first about cleanliness.
Fassett pointed out that a substantial portion of a turbine’s energy is used by the compressor, which means dirty compressor blades can have a serious effect on efficiency. “When the blades are dirty, the airflow is more turbulent, and that will degrade performance.”
Of course, the importance of maintaining inlet filters and keeping intake air clean isn’t a novel idea. Poor-quality inlet air can also lead to blade erosion and corrosion of turbine components, both of which will hurt efficiency. One problem is that the effects of poor-quality air are cumulative: Though cleaning can address blade fouling to some extent, restoring original turbine performance is typically not possible—and erosion can only be addressed by replacement. Thus, it behooves turbine operators to keep air quality as high as possible from initial startup.
But Fassett said the solution he recommends isn’t one operators often take: Swapping out standard ASHRAE filters for HEPA-rated filters.