In current years, using single-shaft mixed cycle energy vegetation has steadily elevated within the U.S. While multi-shaft configurations are advantageous in sure eventualities—for instance, when format flexibility or phased set up is required—single-shaft designs have confirmed to be a extremely environment friendly and cost-saving choice for energy plant homeowners and operators in search of to maximise the worth of their asset.
Single-Shaft vs. 1 x 1 Multi-Shaft
In a single-shaft configuration, each prime movers (the fuel and steam generators) are on one shaft line related by a synchronous self-shifting (SSS) clutch, and so they drive a single, widespread generator (Figure 1). Beyond a typical generator, the stability of plant (BOP) methods in a single-shaft configuration are additionally harmonized leading to fewer particular person elements. This is in distinction to multi-shaft configurations, the place the steam and fuel generators are on completely different shaft strains, supported by separate BOP methods, and drive their very own unbiased mills.
1. The shortest distance between two factors is a straight line. A single-shaft configuration signifies that each the fuel turbine and steam turbine are organized on one shaft and drive the identical generator. Courtesy: Siemens
Having a single generator related to the grid and fewer BOP gear provides monetary, operational, and footprint benefits for the single-shaft association. For occasion, one generator means one set of bus ducts, and one generator breaker, generator step-up transformer, and switchyard. In many circumstances, selecting a single-shaft association quite than a multi-shaft design can lead to capital expense financial savings of three% to five% for the plant.
A small acquire in plant effectivity can be achieved, as one giant generator sometimes has a barely greater effectivity than two smaller ones. Single-shaft configurations additionally require fewer mechanical connections, which interprets into decrease losses. Similarly, the simplification of BOP methods, reminiscent of lube oil methods, can lead to much less upkeep, greater availability, and decrease auxiliary energy demand. Single-shaft configurations have a extra compact design than multi-shaft, resulting in a smaller footprint for the plant. This is very advantageous on websites the place gear must be enclosed inside a constructing, attributable to noise or climate restrictions, for instance.
Multi-shaft configurations are most popular for assembly particular association necessities or when the fuel turbine is constructed and operated months or years forward of mixed cycle improvement.
2 x Single-Shaft vs. 2 x 1 Multi-Shaft
Two single-shaft vegetation can be utilized as a substitute for conventional 2 x 1 configurations. With one steam turbine for every fuel turbine, the single-shafts can exhibit greater effectivity in low-load eventualities (that’s, when just one fuel turbine is in operation). This can be the case when switching from one to 2 fuel turbine operation. In such circumstances, every warmth restoration steam generator (HRSG) produces steam for its personal steam turbine. As a end result, there is no such thing as a must carry up the second HRSG in bypass operation to match steam temperature and stress earlier than mixing with the steam going to the turbine from the primary HRSG.
An added good thing about the two x single-shaft design is that it permits for phased mixed cycle building of trains throughout the set up part of the ability plant. Having two mixed cycle blocks, every with a single-shaft energy prepare, additionally offers benefits as regards to availability and upkeep, because it permits for the servicing of 1 prepare whereas the opposite is in operation. In sure circumstances, this can allow energy plant operators to extra successfully reply to the wants of the market. Conversely, service on any part moreover a fuel turbine in a 2 x 1 configuration requires the whole plant to be out of operation.
The similar advantages talked about for a 1 x 1…