Thermal power plants rely on surface water to cool the steam that drives the turbines and generates electricity. But during times of drought, that surface water can no longer be counted on.
How can pump station operators ensure that their critical operations run smoothly during challenging drought conditions? Our hydraulic flow experts have a few suggestions.
Know the Limits of Your Power Plant Cooling System
How low can water levels get while still maintaining the safety and effectiveness of your pump?
If drought conditions are leading to lower-than-recommended water levels in a wet well, one way to determine whether there's a problem is to perform scale physical flow modeling. In Texas, where drought duration and intensity have been threatening the power grid, several stations have taken this action. These models have provided helpful data on flow patterns and also thorough information on air entrainment — pockets of air that can adversely affect plant operations.
Monitor Your Thermal Power Plant for Two Noisy Problems
Pumps are designed to operate with a specified amount of upstream water pressure, known as Net Positive Suction Head Required (NPSHR), as well as a specified submergence below the wet well water surface.
Two serious problems can occur when these requirements are not met, such as in a drought or low water level situation. Both come with telltale sounds that operators should be monitoring.
Cavitation is a process in which water boils and forms vapor within the pump impeller because of low pressure. Over time, it can cause erosion of the impeller. But you should be able to catch it before it does much damage — it sounds like rocks rolling around inside the pump.
2. Air Entrainment
We touched on this a bit earlier, but air entrainment happens when pumps no longer have sufficient submergence, resulting in the formation of a vortex. You can see this concept in action when you’re draining a bath. As the water levels get low, you’ll start to see a vortex form, and the once-quiet process will take on a signature sound.
Air entrainment in a thermal power plant sounds like sucking or rumbling and can cause changes in pump performance, loss of suction, fluctuations in component loads, and vibration severe enough to destroy the pump.
Design Modifications To Boost the Efficiency of Your Thermal Power Plant
With observational and modeling data in hand, a plant has the ingredients to determine which (and whether) wet well design modifications could help the plant to operate at even lower water levels.
In the case of the Texas stations, modeling revealed undesirable flow characteristics at low water levels. Our team was able to address these issues with the following modifications:
- Lowering the pumps
- Adding subsurface wall grating
- Inserting pump bell floor splitters
- Putting in horizontal grating at the water surface
- Installing curtain walls
Dry Cooling Power Plants and Other Innovative Solutions
Thermal plants can also save 80% of their water by taking advantage of a few recent design innovations: dry coolers, hybrid coolers, and air-cooled condensers (ACCs).
Dry cooling systems take advantage of the surrounding air to cool and condense steam. Direct systems require no additional water. Indirect systems use closed-system cooling water to condense the steam to prevent excess water loss due to evaporation.
Like the name suggests, hybrid cooling systems accommodate both dry and wet cooling. These systems are helpful for areas that have wet and dry seasons.
Air Cooled Condensers
An ACC condenses steam inside finned tubes and uses cool air outside the tubes to reduce heat.
Add Resiliency With a Power Engineering Company
Since 1950, data shows that certain regions of the world are experiencing longer and more intense droughts — a phenomenon that is projected to continue as the climate warms. Having a strategy in place to drought-proof pump stations in hard-hit regions can help ensure essential power generation and drinking water operation.
If you’re hoping to add resilience to your thermal power station, we’re happy to help! Verdantas was created to solve complex engineering problems and add resilience to civil infrastructure. If your plant is frequently operating below its design basis, our team can make strategic modifications to allow your plant to operate safely and effectively. But timing is key — it’s best to make these modifications early before low water levels damage your pumps.
Click below to learn more about how our team worked with nuclear plant operators to minimize vortex formation and air entrainment.
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