Making electricity is like creating a huge science project for school. You get all your materials together, mix them up to make something incredible, and then your mom gets on you to clean up the mess youve made in the kitchen.
You cant make anythinga science project, a cake, or electric powerwithout having to clean up afterwards. For TVA that means finding ways to make power for millions of homes, schools, farms, and businesses, and at the same time keep the environment clean and healthy.
Wheres the dirt?
Electricity looks pretty clean, right? You flip a switch and a light goes on. Whats so messy about that? Well, its the making of electricity that can create pollution. A significant portion of TVAs power is generated by the burning of coal. When coal burns, potentially dangerous chemicals like sulfur dioxide and nitrogen oxides are released into the air. (Read information from the U.S. Environmental Protection Agency about air quality.)
Clearing the air
To clean up the air while still providing everyone in the Tennessee Valley with electric power, TVA uses some pretty complex, expensive equipment.
Through 2011 TVA has spent around $5.4 billion to control the release, or “emission,” of chemicals from its coal-burning power plants. To stay in compliance with future air quality regulations, TVA may spend another $3.4 billion by 2018.
Here's some of what TVA has done so far:
- To reduce sulfur dioxides, which are a component of acid rain, TVA has installed scrubbers on 17 of its coal-fired units and switched to lower-sulfur coals at 41 units. In August 2011, the TVA board of directors approved plans to install scrubbers on seven more coal-fired units.
Scrubbers mix powdered limestone with the hot gas that results from burning coal. This converts up to 95 percent of the sulfur dioxide to benefical byproducts like gypsum -- which is the main ingredient in the wall board that is used in the interior walls of many homes and offices.
- Nitrogen oxides contribute to ground-level ozone and acid rain. To reduce nitrogen oxides, TVA has installed a variety of technologies on many of its coal-fired units, including selective catalytic reduction systems. These systems convert nitrogen oxides to harmless nitrogen gas and water vapor. TVA has installed them on 21 of its coal-fired units.
TVA also has installed a variety of cleaner, more efficient combustion equipment on the majority of its coal-fired units to further reduce nitrogen oxides.
- Particulates are extremely small particles or droplets that result when fuels are burned. TVA has equipped all its coal-fired units with devices to reduce particulate emissions. These devices include electrostatic precipitators, similar to those in home air cleaners, that capture the particulates with static charges of electricity.
As a result of these and other actions, TVA has reduced its emissions of nitrogen oxides by 87 percent from their peak levels in 1995. And TVA has reduced its emissions of sulfure dioxides by 91 percent from their peak in 1977.