Innovation and Technology Development
Carbon dioxide capture
Carbon dioxide (CO2) is a greenhouse gas: it traps heat that would ordinarily be radiated into space and holds it near the earth’s surface. Some scientists believe that the increased production of such gases is related to global climate change. TVA is partnering with the Electric Power Research Institute (EPRI) and the Department of Energy (DOE) on several projects to develop and evaluate technologies for removing and storing atmospheric CO2.
One project, the Carbon Capture and Water Emissions Treatment System (CCWESTRS), is testing methods of capturing, or sequestering, CO2 and storing it in forms that prevent its reintroduction into the atmosphere. Some highlights:
• Begun in 2002, this demonstration project is located on marginally reclaimed surface-coal-mine land at Paradise Fossil Plant in western Kentucky.
• The 40-hectare (100-acre) site has been planted with sycamore and sweetgum trees that have the estimated potential to capture 70 to 90 metric tons (78-100 tons) of carbon per year over a 20-year period.
• A unique aspect of the project is that the gypsum produced by the plant’s scrubber (the emission control system for sulfur dioxide) is used as a soil additive and mulch for the trees, and water from the plant’s fly ash pond is used for irrigation. Both of those substances must be properly managed to avoid unwanted environmental impacts.
• Added benefits include the production of commercial-grade lumber from the trees and the development of the site as wildlife habitat.
• Soil analysis and measurement of the below-ground carbon being stored by the trees’ roots indicate positive results. Read more about TVA’s carbon capture research.
Solar-powered hybrid lighting system
Solar-powered hybrid lighting is an exciting new technology launched in 2005 that promises to provide a better quality of indoor lighting for commercial buildings while saving energy and money. Developed at the Oak Ridge National Laboratory and funded by the Department of Energy and TVA, the system pipes sunlight into a room. A roof-mounted collector and small optical fibers transfer the sunlight to hybrid fixtures that allow both solar and electric light sources to work in tandem. The electric lights are dimmed when the sunlight is bright and are turned up again when clouds move in or the sun sets. Because the system can block ultraviolet and infrared heat more effectively than windows and skylights, it reduces the energy used for cooling as well as lighting. The cost savings can be especially dramatic in areas where sunshine is abundant.
Solar aeration project
Solar aeration is a promising technology for catfish ponds and sewage treatment lagoons where water temperature and oxygen concentrations vary at different water depths, requiring some mechanism to mix the layers. TVA is collaborating in this project with the Mississippi Technology Alliance; S&N Airoflo, a manufacturing company; and the city of Fulton, Mississippi. The system uses 18 solar panels connected to a DC motor that operates the mixer. Phase 1 of the project verified that the system would operate and improve the oxygen content of the pond. Phase 2 is under way and will quantify the effectiveness of the system. This approach can be used to provide aeration to ponds and lagoons where electricity is not readily available.
Aquatic toxicity improvement
To comply with stricter air quality regulations, fossil power plants have to undergo numerous technological modifications to capture pollution from air emissions, such as selective catalytic reduction systems, scrubbers, and mercury controls, all of which raise the potential for increased toxicity of water discharges.
TVA, in partnership with DOE, EPRI, American Electric Power, and Duke Power, is conducting field-scale investigations and demonstrations of integrated passive treatment technology to remove ammonia, nitrate, and heavy metals from the large amounts of water used for fossil plant processes. TVA designed and operated laboratory-scale passive treatment systems from 2001 to 2004 to test various biological and geochemical components for pollutant removal. In 2005, an operational scale passive treatment system was constructed at Paradise Fossil Plant. This system will be operated and evaluated for two to three years to determine its performance potential, costs, and benefits.