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The Magazine
Optimized turbine blades and vanes: part of the Siemens Operational Flexibility Upgrade 7.

Operational flexibility

Custom modernization raises Marchwood’s output

The custom-designed Operational Flexibility Upgrade 7 for the SGT5-4000F gas turbine has been implemented for the first time ever, with outstanding success meaning that Marchwood power plant is now one of the most efficient in the UK.

Installed in 2009, 840-megawatt Marchwood CCPP used to be a combined cycle power plant like many others. Over the years, however, the market conditions changed and plant operator Marchwood Power Limited sought increased flexibility in terms of managing production as more renewable energy has become part of the mix. At the same time, the company wanted to profit from the full revenue potential of its power purchase agreement (PPA).
With the implementation of the Operational Flexibility Upgrade 7 in 2015 – which included the technological modernization of the two SGT5-4000F gas turbines and an extension and modification to the service contract to increase the power plant’s operational flexibility – Marchwood is now one of the most efficient power plants in the UK, with the highest level of availability. The plant’s output rose by 58 megawatts – it now operates at 898 megawatts – and efficiency increased by 0.7 percentage points for each gas turbine.

A cross-section of a SGT5-4000F gas turbine: The highlighted components have been upgraded or exchanged as part of the Operational Flexibility Upgrade 7.


The gas turbines in Marchwood profited from three main modernizations;

Firstly, Siemens installed new hot-gas parts for the turbine and combustion chamber to improve the cooling air concept and save cooling air;

Secondly, it implemented new burners to improve combustion stability;

Finally, the team adapted new instrumentation and control logic to optimize the firing temperature, which lead to an increase of power and efficiency.

Better availability, more power
The plant’s operator directly benefits from these improvements, which maximize the power plant’s viability. “Safety, reliability, and flexibility are the most important things for our plant,” explains Robert Apsley, the station manager of Marchwood Power Limited. Higher availability and efficiency result in more power – and hence more revenue being generated with the existing infrastructure.

Safety, reliability, and flexibility are the most important things for our plant.
Robert Apsley, Power Station Manager at Marchwood Power Station


The implementation of the upgrade was straightforward: A planned outage was extended for two weeks to allow for the hardware and control system upgrade of the SGT5-4000F gas turbines. Marchwood is the first customer to profit from the customized OFU7 package.

Proactive strategy

Marchwood Power decided to adopt a proactive strategy. The power purchase agreement (PPA) is set to end – in 2024 –, so roughly 10-12 years before this the company began discussions with Siemens about its options for modernizing components to raise the efficiency of its gas turbines. Marchwood also wanted to know more about its options to adapt and extend the service contract with Siemens.

“The successful implementation of the OFU 7 upgrade was a result of our close collaboration with Marchwood,” says Falk Eisermann, Project Manager for First Time Application and Product Commercialization, Power Generation Services, Power and Gas at Siemens.

“The original idea was to sell a small upgrade package to the customer, but in the negotiations, we discovered that there was money that could still be earned for the customer if we combined a bigger upgrade package. This helps to increase power, efficiency, and flexibility with a contract adaption to raise the availability to a higher level,” he adds. Marchwood was the first customer to profit from the customized OFU7 package.

New sources of revenue
In addition, Eisermann says, the modernization gave Marchwood the chance to offer new and different grid services, such as the National Grid’s fast reserve service. Previously this was possible with GT load gradient optimization. “We gave them a better minimum operation point. Marchwood is able to generate with lower power output and emissions and it doesn’t have to shut down the power plant overnight,” explains Eisermann.

For Marchwood, the modernizations mean its business model is stable through to 2024. The plant’s newfound flexibility is already paying off and is reflected in Marchwood’s increased power sales.

Rhea Wessel, American freelance writer based in Frankfurt, Germany
Picture credits: Siemens AG