In a present world situation of geopolitical instabilities, retirement of coal property and rising curiosity in environmental duty, the assorted stakeholders of the energy sector are going through unprecedented challenges to fulfill market wants. The power producers are on the lookout for different applied sciences capable of assure greater effectivity and reliability, operational flexibility and long-term profitability in a risky surroundings.
SOFC: progressive energy supply
Inside the power generator area, gas cells are progressive options because the direct electrochemical conversion of the gas’s power content material into DC electrical energy removes the exergetic losses related to the combustion course of. In that perspective, Solid Oxide Fuel Cell (SOFC) could be very properly suited expertise for distributed energy era because of its excessive effectivity and low pollution emissions in stand-alone configuration. Furthermore, SOFC is taken into account an ideal candidate to be built-in into standard thermodynamical cycles since:
- Its electrolyte, a non-porous metallic oxide (usually yttria-stabilized zirconium oxide), has been proved to be tolerant to carbon monoxide. This enables the anode of the cell to be fed instantly with pure fuel (NG), which will be transformed internally to the SOFC module into hydrogen, via the endothermic reactions of Methane Steam Reforming (MSR) and Water Fuel Shift (WGS);
- Because of its excessive working temperature (between 650°C-1000°C), an enormous quantity of the obtainable hydrogen chemical power is dissipated as warmth into the surroundings. By integrating the SOFC with a thermodynamic cycle able to changing that wasted warmth into helpful work, an enchancment of the general effectivity of the method shall be achieved.
Triple Mixed System
Having stated this, a hybrid set-up wherein an SOFC is coupled with a Fuel Turbine (GT), represents progressive options of accelerating curiosity, able to making certain very excessive efficiency whereas minimizing environmental emissions. The Hybrid cycle idea will be utilized on massive centralized energy crops with an put in capability of tons of of MW.
In that context, Triple Mixed System obtained by integrating a SOFC and Fuel Turbine Mixed cycle (GTCC), is the final frontier of electrical energy era when it comes to effectivity, with a theoretical total conversion yield (primarily based on gas’s Decrease Calorific worth) 10% greater than these of the most recent H sequence turbogas mixed cycle.
Within the configuration of triple mixed cycle, the pressurized SOFC is situated between the compressor and the expander, each put in alongside the identical shaft and it’s linked to the exterior DC circuit. The first gas (pure fuel) and oxidant streams are preheated to 650-750°C temperature stage required at SOFC inlet earlier than getting into respectively the anode and cathode. The anode off-gas, which incorporates residual gas species, is blended with extra pure fuel and oxidized by the cathodic outlet depleted movement within the afterburner. The exhaust gases are expanded within the turbine which drives an electrical generator the place the web shaft energy is transformed into electrical one. On the outlet of the expander, the thermal power of the GT off-gases is recovered right into a 3-pressure ranges Warmth Restoration Steam Cycle (HRSC).
The system below investigation can attain an impressive total effectivity of round 80%, achievable when the first pure fuel movement is maximized and for strain ratio comparatively low (within the vary of 13- 16). Contemplating a plant’s theoretical put in capability of near 800 MW, the SOFC produces round 60% of whole electrical energy delivered, GT 30% and the HRSC 10%.
Nevertheless, because of structural issues, movement distributions and temperature management inside the cell, it’s not possible to set-up SOFC modules of tens or tons of of MW. It is likely to be conceivable to distribute the energy output from the gas cell over a sequence of modules in parallel, every of most dimension of kW or a couple of MW. In any case, because of the excessive value of the expertise and the decay of efficiency over time that has but to be verified, the triple mixed configuration for large-scale power generation has not discovered industrial or industrial curiosity these days.
Sooner or later years, with the event of a scale financial system on gas cell, an rising request to maximise electrical energy manufacturing yields and to respect strict environmental limits on emissions, this expertise will definitely discover rising investments and sensible software.
