These pages present a detailed description and assessment of Texas' abundant renewable energy resources.
Water energy resources include hydroelectric power from lakes and rivers, ocean energy in its various forms, and energy technologies that take advantage of saline water. Texas possesses these resources in varying degrees, ranging from poor in the case of ocean resources to excellent for salt water. Each one is outlined below.
FIGURE 10. Hydro Potential of Texas River Systems
Hydroelectric Power (Hydropower)
Hydropower makes use of the kinetic energy water gains when it drops in elevation. Typically, water dammed in a lake or reservoir is released through turbines and generators to produce electricity. Hydropower has been a staple of electricity generation since the beginnings of the electric age. Historically, U.S. hydroelectric generation expanded until about 1975, but its share of the national electrical energy mix steadily declined from a peak of about 40% in the 1930's to approximately 10% today.
FIGURE 12. Energy From Texas Water Resources.
Hydroelectric, ocean, and saline water resource areas are identified. (See legend below.)
In Texas, hydropower's contribution is much smaller, accounting for only 1% (640 MWe) of the state's electrical generating capacity and less than 0.5 percent of the energy produced. The red dots in Figure 12 identify the location of the state's existing hydro facilities. A 1993 study by the Idaho National Egineering Laboratory identified an additional 1,000 MW of undeveloped hydro resource (identified as the green dots in Figure 12 and summarized with existing generation by river basin in Figure 10). Very little of this potential is currently slated for development. Significant legal and regulatory impediments, such as land acquisition and environmental protection, will be a part of any major hydro project. Additionally, reservoirs are typically built and managed primarily as municipal water supply and flood control systems and secondarily for power production. This fact lowers the potential impact of hydro development on the state's energy picture.
FIGURE 13. U.S. Hydroelectric Energy Potential.
This map depicts the hydroelectric potential of each state relative to its area. Washington, with 25% of the nation's potential, has 75 times more hydro energy per unit area than Texas, which ranks only 43rd out of the 50 states.
Three distinct types of ocean resource are commonly mentioned as possible energy sources: tides, waves, and ocean temperature differentials (ocean thermal energy conversion, or OTEC). None are significant resources in Texas and, to date, have not been commercially exploited elsewhere. Tidal energy schemes capture water at high tide and release it at low tide. But Texas, with a median Gulf Coast tidal range of just 1.3 feet, does not have the large tides necessary for such a system to be feasible. The wave resource is slightly better. Gulf Coast waves are comparable in size to those off the U.S. Atlantic Coast. However, Gulf Coast waves tend to dissipate close in to shore due to relatively shallow waters, a fact that would hinder development since electricity would have to be transmitted significant distances to land. Finally, the closest potential OTEC site to Texas is more than 100 miles offshore. This distance makes it difficult to classify it as a Texas resource, and, at any rate, the site is of marginal quality.
Saline and brackish water is common throughout much of Texas (Figure 12). Normally it poses a problem for fresh water supplies. Several technologies, however, can take advantage of saline water for energy production. These include solar ponds and algae production. Solar ponds use the salt water in such a manner that heat from sunlight is effectively locked in the pool and can be used for a number of process heat applications or electricity production. The ability of the pond to store solar thermal energy is unique and overcomes the resource variability that is a drawback of traditional solar development. Salt water algaes grow prolifically under cultivated conditions and can be pressed to extract biodiesel feedstocks or dried and burned for power production. Although neither technology has been demonstrated beyond pilot levels, Texas is fortunate in that regions with saline water resources also tend to be very sunny. If coupled with ongoing fresh water chloride control efforts, exploitation of the saline water resource for energy production may be possible for modest additional investment.
Potential Energy Value of Texas Water Resources
Hydropower is a mature renewable energy source. The relatively gentle terrain, low rainfall, and moderate changes in elevation throughout much of Texas means the state's hydropower resource is mediocre by national standards (see Figure 13), and, due to a variety of factors, will see only modest continued development. Ocean energy technologies are immature, but this point may be moot as Texas has poor ocean energy resources. Readily accessible saline water in much of West Texas coupled with the region's high annual insolation means that this area is among the best candidate solar pond sites in the U.S. Proposed projects to safeguard freshwater supplies from salt water intrusion may provide opportunities for feasibly employing saline water technologies.
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