Cooling system upgrade |
Figure 4. Scatter plots of steam turbine generator (STG) gross power output (vertical axis, MW) vs backpressure at the discharge of the steam turbine (horizontal axis, bar). Orange dots are for a week in January 2022 and blue dots for a week in January 2021. The higher the back pressure, the more restriction on the steam turbine affecting output and efficiency. Improved ACC cooling reflects Galebreaker installation.
The January 2022 dots are compared with those of January 2021, ie before and after the wind screen upgrade, so that weather conditions (temp/pressure) as well as wind speeds are similar. The plots are over a seven-day period with the plant running regularly at full load. Axis details on the graph are limited due to restriction on information that can be published, however, the following conclusions can be drawn:
● Comparison of the orange and blue scatter plots show increased MW output after installation of the Galebreaker replacement screens.
● A key contributor to this is the reduced back pressure, which improves the efficiency of the steam turbine.
Source: Galebreaker
“Plants vary by construction, location and output, so this step is crucial – there’s no universal solution,” he adds.
“Coryton was no different; we started with the CFD modelling to test configurations of screens and determine what would deliver the best results.
“We found that Coryton was experiencing significant disruption from south-westerly winds,” Gary recalls.
“The original installation, which involved a large open mesh full height screen to block the wind, actually starved the system of airflow. “We were able to redesign this system for Coryton, utilising lower solidity high-level screens to reduce wind velocity directly underneath the fans.”
26 new screens were designed, consisting of 50% solid high-level perimeter screens, engineered and manufactured in around three months and installed over a three-week period. See Figures 2 and 3.
Evaluating the original performance report from Galebreaker’s first wind screen installation at the site around 20 years ago, Gary says substantial improvements were recorded. “The site’s average windspeed at that time was between 2.8 m/s - 4.3 m/s. Installation of the windshields improved the ACC vacuum by 4.8 mbar at wind speeds of 3.6 m/s, with greater improvements at higher wind speeds, which helped Coryton recover more energy.” Steam turbine efficiency and output is directly linked to the steam condensing temperature in the ACC, which is relative to backpressure. Figure 4 shows plots of back pressure in the ACC for one week in January 2021 and January 2022, ie before and after the installation of the replacement wind protection screens. Data shared by Coryton illustrates the shift in turbine
back pressure, demonstrating the benefits of the wind protection screens on the ACC, as well as other improvements that were carried out to enhance the station’s output. Plant operators and engineers typically diagnose ACC performance problems after the plant has been operational for an extended period, usually following the expiry of initial warranties.
“Operators often notice a drop in efficiency but don’t realise the root cause until performance issues become significant,” says Gary. “They typically consider fan performance, cleaning and air tightness first because of the obvious impact issues with airflow, dirty heat transfer surfaces, and higher levels of non-condensable gas ingestion can have on performance.
“Once that’s ruled out, they begin to consider external factors.”
Gary explains many plants are unaware of how much wind affects performance, ultimately impacting turbine output.
“When wind disrupts ACC performance, it can directly affect the plant operators’ ability to meet their agreed output to the grid,” he explains. “Operators can be fined for not delivering the energy they committed to. Moreover, if the plant is unable to deliver as expected, they might have to reduce their expected output or shut down temporarily.”
Gary adds, “Baseload plants need consistent performance to maximise output and are often the biggest winners when it comes to mitigating the effects of wind on performance. However, opportunities also exist in delivering power at peak times where energy demand on the grid is high and a premium price is offered. Performance drops during these times can lead to significant missed revenue opportunities, making the financial impact of wind much greater.”
28 | March 2026 |
www.modernpowersystems.com
Unlike OEMs, which focus on ensuring the ACC functions within predetermined limits, Gary and his team focus on retaining efficiency. “We’re not trying to push performance beyond design specs. Instead, we’re trying to determine how a plant can squeeze the most out of their equipment with no increase in operating costs. This is where screens come in. “For Coryton, as with other installations, we built a full 3D model of the plant, creating a ‘digital twin’ in Excel, governed by thermodynamics,” Gary explains. “We fed in a year’s worth of wind and weather data so we could predict plant output with and without wind screens across every common operating condition.” The CFD model tracks millions of air particles as they move across the plant, hitting structures and interacting with each fan. The outputs are quantitative as well as visual, with heat maps and velocity plots over each fan, showing areas where airflow is good or compromised.
“Each fan behaves according to its own fan curve, so you can see which units are being starved of air, where hot air is recirculating and how that changes once you add screens,” Gary explains. This data-driven approach provides plant operators with clear, quantifiable evidence of the potential benefits of installing wind protection.
“Ultimately we can say: this is how many megawatts you’re losing to wind, this is how much we can realistically recover, and this is the payback period.”
“Combining CFD, quantum computing and real-time weather data could enable complex modelling and instant adjustments,” says Gary.
Changing face of power generation Gary highlights that while the UK’s focus on net- zero is driving innovation in energy efficiency, international markets, especially in Asia and the Middle East, present different challenges. “In the UK, we’re seeing a shift towards more renewable energy sources like wind, EfW, and solar, so the focus is on extending the life of existing assets, improving efficiency to meet sustainability targets – but globally, especially in the Middle East, gas-fired power plants continue to be a major energy source,” he says. “The challenge there is the plants are often huge, and environmental conditions are much harsher, with higher temperatures and wind speeds, which makes it more difficult to maintain cooling efficiency, so the global outlook for wind protection systems is expanding.”
* VGB-R-131 (the VGB test code used for acceptance limits for thermal performance testing: mean wind velocity (average over the test period) must not exceed ~3 m/s; peak instantaneous wind velocity must not exceed ~6 m/s more than 20 times per hour. These limits are measured approximately 1 m above the upper edge of the condenser under undisturbed conditions and apply to test conditions, not structural low and ask for a higher design wind speed.
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