Novel supercritical CO2/organic Rankine cycle systems for solid-waste incineration energy harvesting: Thermo-environmental analysis

Waste-to-energy is considered as an effective way to simultaneously digest the municipal waste and generate useful power. Steam Rankine cycle is conventionally adopted for solid-waste incineration energy harvesting. To further improve the energy conversion efficiency, cascade systems consisting of a supercritical CO2 cycle and an organic Rankine cycle were proposed, where both the subcritical and transcritical organic Rankine cycle systems using R1233zd(E) as the working fluid were considered. Thermodynamic and the environmental analysis were evaluated comprehensively, with a follow-up comparison with the state-of-the-art technologies. The results show that compared with the original waste-to-energy plant, the turbine output (2.55 x 10(7) W) and waste-to-energy efficiency (42.61%) of the supercritical CO2 cycle/subcritical organic Rankine cycle power plant are increased by 9.50 x 10(6) W and 59.41%, respectively. If changing to the supercritical CO2 cycle/transcritical organic Rankine cycle system, the improvement will be greater, i.e., 10.19 x 10(6) W and 63.71% respectively. The comparison with the state-of-the-art power plants also shows the new waste-to-energy plant has higher efficiency and better environmental performance. The ecological efficiency and sustainability index of supercritical CO2 cycle/subcritical organic Rankine cycle system power plant are 88.82% and 1.54, while 89.14% and 1.57 with the supercritical CO2 cycle/transcritical organic Rankine cycle system. The proposed cascade system demonstrated its potential in performance improvement in the field of waste-to-energy incineration. The study provides insights into the next-generation power plants for solid-waste disposal.