| Gas turbine technology


This requirement led Powerlink to meet with Townsville power station owner Ratch to discuss options for a facility that includes a 160 MW Siemens Energy SGT5-2000E gas turbine and an 82 MW heat recovery steam generator (HRSG). After reviewing eight possible solutions, Powerlink concluded that the least-cost option to address system strength services was the addition of a clutch to the shaft between the Siemens Energy gas turbine and the generator, to be carried out during a scheduled major outage in 2025.


“Replacing the intermediate shaft of the gas turbine with a Synchro-Self-Shifting (SSS) clutch will provide an instantaneous switch from power generation to synchronous condenser mode,” said Garwood.


When in synchronous condenser mode, the RGS unit can provide rotating inertia and 350 to 400 MVA of short-circuit power without the need to produce power. The electrical inertia while operating in the grid stabilisation mode is calculated to be around 250 megawatt seconds


(MW.s) and around 1000 MW.s while operating in power generation mode. Plant owner Ratch- Australia gains a new revenue stream from providing these additional grid services. “This modification is cheaper and faster than a greenfield dedicated synchronous condenser and provides our gas turbine customers with an additional revenue stream,” said Garwood. “It allows one unit to fulfill two roles: to operate as a power generator as it always has (clutch closed); or operate as a synchronous condenser when power generation is not required (clutch open and GT not operating).”


Grid support: a niche for gas turbines


The history of technology has many examples of the new trying to get rid of the old a little too rapidly. The mainframe computer was “dead” in the mid nineties according to Microsoft and IT analyst firm Gartner. Yet it remains very much alive and well inside large corporations as the best technology for very high-end transactional


processing systems. Similarly, tape-based storage was killed off by disk more than twenty years ago, according to disk advocates. Yet more tape is being used today than ever, primarily for long- term archiving of large quantities of data. The moral of the story is that the old may lose ground to newer technologies, but they usually find a niche in which they continue to add value for some time to come. This is the case with the new of renewables and the old of gas turbines. Yes, renewables can and will prevail. But if advocates insist on the elimination of any and all natural gas generation assets, they will only destabilise the grid, drive up costs and potentially cause rolling blackouts. The evolving role of the gas turbine, then, is to provide reliable backup and peaking generation and to offer grid support that makes it possible for more and more renewables to come onto the grid. “The transition to more renewable energy is a balancing act between sustainability, reliability and affordability and is best thought of as a marathon, not a drag race,” says Axford.


Methanol: gas turbine fuel of the future?


Aberdeen based Net Zero Technology Centre (NZTC) and Siemens Energy have again proven the transformative potential of alternative fuels as a means of decarbonisation. The latest demonstration successfully operated an SGT-A35 gas turbine on methanol, retrofitted with relatively minor modifications, “proving the feasibility of green methanol for decarbonising current infrastructure.”


One of the benefits of methanol as an alternative to traditional fossil fuels is that it can be produced from a range of feedstocks, including lower carbon intensity routes involving carbon capture and storage (blue methanol), biogenic sources (bio-methanol) and green hydrogen with captured CO2


(e-methanol).


Widely available conventional methanol, produced from natural gas, can result in a 10% reduction in CO2


emissions by up to 95%.


Use of methanol, in all its forms, significantly reduces other emissions, including NOx


and smoke. The demonstration test showed a decrease in NOx


of up to 80%.


Siemens Energy and NZTC carried out the demonstration at RWG’s test facility in Aberdeen. It was witnessed by methanol producer Proman, which contributed the methanol fuel for the test. The aeroderivative SGT-A35 gas turbine, now rated at 38 MW, was introduced to the market by Rolls-Royce in the 1970s as the Industrial RB211. Used both offshore and onshore for power generation and mechanical drive, there are 800 plus machines worldwide, which have accumulated over 46 million operating hours. Siemens Energy used 3D printing techniques to manufacture the new components required for methanol fuel conversion.


This latest demonstration builds on a 2023 SGT-A35 gas turbine on the test bed in RWG’s Aberdeen facility www.modernpowersystems.com | November/December 2024 | 29 emissions today compared with


traditional liquid fuels. Renewable methanol can cut CO2


, PM, SO2


world-first collaboration between NZTC and Siemens Energy that saw an SGT-A20 turbine


running on bio-methanol. This showed CO2 emissions could be reduced by up to 75% when compared to conventional fuels. Conventional methanol can be blended with increasing amounts of blue or green methanol to meet customer needs and achieve specific carbon intensity targets supporting the decarbonisation pathway.


The demonstrations are being delivered through NZTC’s Alternative Fuel for Gas Turbines project, one of seven projects under NZTC’s Net


Zero Technology Transition Programme (NZTTP). NZTTP is funded with £16.5 million from the Scottish government’s Energy Transition Fund and industry matched funding to transform the North Sea energy system.


NZTC, established in 2017, is a not-for-profit organisation working with industry, government and academia driving innovation to accelerate the energy transition.


It was created as part of the Aberdeen City Region Deal, with £180 million of UK and Scottish government funding with the aim of helping to maximise the potential of the North Sea.


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