Parametric Exergy Analysis of a Biomass-assisted Organic Rankine Cycle Tri-generation Energy System.
Keywords:
ORC, exergy, biomass, tri-generation. EnergyAbstract
The study applied conventional exergy analysis to a biomass-assisted multi-generation energy system for power generation, heating and cooling. The parametric assessment was done using environmentally friendly refrigerants - R245fa, R1234yf, and R1234ze. To understand optimum operating parameters for the proposed system, both first and second law thermodynamic models were used to simulate the cycle with Engineering Equation Solver (EES). The results demonstrates that the exergy efficiency of the system is greatly enhanced by virtue of the new organic Rankine cycle(ORC) configuration to include cooling and heating as products. This led to an increase in exergy efficiencies of 28.34 %, 22.32 %, and 29.61 % with refrigerants R245fa, R1234yf, and R1234ze, respectively, compared to an earlier study with a similar configuration. The net power output ranged between 14.08 and 32.55 kW at very moderate refrigerant mass rate of 2.05 kg/s and 0.3071 kg/s of the biomass syngas. This provision allows the operation of the system at relatively low external heat content, but at flue gas temperatures up to 600 oC. Therefore, the system can be fired with a Brayton topping cycle at controlled mass flow rates of flue gas (0.3071 kg/s). Furthermore, turbine inlet temperatures were spread as 120 oC, 95 oC and 90 oC, respectively for R245fa, R1234yf, and R1234ze. This low range can facilitate the system’s operation from very low temperature waste heat from many sources
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