Energy Excursions

Water and Electricity

Water is used in two primary ways for electricity generation: 

  1.  To create steam to power the turbines generating electricity 
  2. Thermodynamic cooling of the power plant (condense the steam back into water, etc.) 

We rely on the heat from energy sources such as coal, natural gas, nuclear, etc. to create power. How does this work? The heat from the particular fuel type generates steam that is then used to power the turbine, generating electricity that can then be sent to the grid. Once the steam is used it is cooled back down to either be released back into its original source (river, lake, etc.) or to be reused.  Water is used to condense the steam in a term referred to as a steam loop.1Stillwell , A., King , C., Webber , M., Duncan , I., & Hardberger, A. (2009, April). Energy‐Water Nexus in Texas. http://texaslivingwaters.org/wp-content/uploads/2013/04/energy-and-water-in-tx09.pdf Different power plants use different quantities of water for cooling purposes. For example, cooling a coal-fired power plant requires different quantities of water compared to a nuclear power plant. 

According to the U.S. Energy Information Administration (EIA), 40% of total water withdrawal in the country accounts for cooling technologies in electrical power generation.2U.S. Energy Information Administration. (n.d.). U.S. Energy Information Administration – EIA – Independent Statistics and Analysis. Some U.S. electricity generating plants use dry cooling – Today in Energy – U.S. Energy Information Administration (EIA). https://www.eia.gov/todayinenergy/detail.php?id=36773 There are ways to reduce water consumption such as recirculating the condensed steam back into the steam generator source or reducing consumption from the original source. This process is referred to as a closed steam loop.3Stillwell , A., King , C., Webber , M., Duncan , I., & Hardberger, A. (2009, April). Energy‐Water Nexus in Texas. http://texaslivingwaters.org/wp-content/uploads/2013/04/energy-and-water-in-tx09.pdf There are also technologies that use dry cooling, which entails using ambient air for cooling the steam once it is used to power the turbines instead of water. Hybrid cooling systems can also be used, including a mix of dry cooling and water consumption for cooling purposes.4U.S. Energy Information Administration. (n.d.). U.S. Energy Information Administration – EIA – Independent Statistics and Analysis. Some U.S. electricity generating plants use dry cooling – Today in Energy – U.S. Energy Information Administration (EIA). https://www.eia.gov/todayinenergy/detail.php?id=36773

Exploring Nameplate Capacity

Nameplate capacity, also known as the rated capacity, nominal capacity, or installed capacity, is the intended full-load sustained output of a facility such as a power station, electric generator, a chemical plant, fuel plant, etc. Nameplate capacity is the theoretical output registered with authorities for classifying the unit. For intermittent power sources, such as wind and solar, nameplate power is the source’s output under ideal conditions, such as maximum usable wind or high sun on a clear summer day.5Wikipedia contributors. (2023, March 14). Nameplate capacity. In Wikipedia, The Free Encyclopedia. Retrieved 17:40, July 12, 2023, from https://en.wikipedia.org/wiki/Nameplate_capacity Let’s use a power plant in Central Texas and see how nameplate capacity might differ from the actual capacity, for example, in the summer.

Thomas C. Ferguson Power Plant

The Thomas C. Ferguson Power Plant, located about 55 miles northwest of Austin, Texas, uses natural gas fired combined cycle technology to generate electricity. The facility is located along the Lower Colorado River. Cooling water is provided by Lake LBJ, a freshwater reservoir created by Wirtz Dam.

The EIA provides an All Energy Infrastructure and Resources web mapping application that shows all U.S. energy infrastructure that EIA has available in geospatial format. The map enables users to visualize the geospatial location of various energy infrastructure assets and explore attribute data on individual features. The data layers are developed by EIA or from other publicly available data.6U.S. Energy Information Administration. All Energy Infrastructure and Resources: About. https://atlas.eia.gov/apps/eia::all-energy-infrastructure-and-resources/about

Let’s open up the web mapping application and look for the Thomas Ferguson Power Plant, just northwest of Austin along the Lower Colorado River.

Using the search feature on the map, find Austin, then follow the Lower Colorado River northwest out of the city until you get to Horseshoe Bend labeled along the river. You’ll note that different types of infrastructure have different symbols—there is a scrolling legend located on the map. Find the icon for the Thomas C. Ferguson Power Plant and click on it for information on the facility. [Careful to click on the plant icon; there are also transmission lines, railroads and other infrastructure elements that are interactive.] Answer the following questions related to the Thomas C. Ferguson Power Plant and the nearby surroundings.

Who operates the Thomas C. Ferguson Power Plant? Look for the Utility name in the info on the plant.

The plant is operated by the Lower Colorado River Authority

What is the nameplate capacity of the Thomas C. Ferguson Power Plant?

574.6 MW

What is the total net summer capacity of the Thomas C. Ferguson Power Plant?

Total Net Summer Capacity is 516.0 MW

Why is the summer capacity different from the nameplate capacity for the Thomas C. Ferguson Power Plant?

The net summer capacity is the peak load that the plant can support during the summer after taking into consideration power used for internal plant operations. Summer capacity is lower than the nameplate capacity because of the increased temperature of cooling water supplies.

Based on the map, what lake provides the cooling water for the Thomas C. Ferguson Power Plant?

Lake Lyndon B. Johnson

What other types of power plants are located quite near the Thomas C. Ferguson Power Plant? Look at the four other power plants closest to the Thomas Ferguson Power Plant.

There are four hydroelectric plants nearby along the Lower Colorado River. You may have noted that all four are operated by the same utility: the Lower Colorado River Authority.

What is the range of nameplate capacity for the 4 plants of this type closest to the Thomas C. Ferguson Power Plant? How do they compare to the gas-fired power plant?

The nameplate capacity range is ~15-55 MW for each of these hydroelectric plants. Cumulatively, these hydroelectric plants have less than a third of the nameplate capacity of the Thomas C. Ferguson Power Plant.

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Oklahoma Academic Standards
TEKS Standards
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Next Generation Science Standards