Energy, exergy, environmental and economy (4E) analysis of the existing of biomass-ORC plant with capacity 150 kWe: A case study

Biomass makes a substantial contribution to Italy’s renewable energy mix. In 2018, 19,235 GWh of energy were created, continuing a trend that began three years earlier. Italy’s demand for biofuel is expected to reach 2.8 million tonnes of oil equivalent by 2025 and remain constant until 2040. Biomass combustion frequently generates high temperatures (900–1000 °C), which justifies the construction of high-temperature heat recovery units such as steam Rankine or supercritical carbondioxide (SCO2) cycles. However, these methods are only economically practical on a medium to large scale. Small-scale units have high component costs because of the high specific volume of steam, while high turbomachinery costs mostly hamper small sCO2 systems. So, another alternative way is to use an organic Rankine cycle (ORC). This study uses thermodynamic analysis to determine how much power can be achieved in terms of energy, exergy, economy and what impact on sustainability is achieved at the Bologna ORC plant. From the study results, it was found that the Bologna unit has a capacity of 150 kWe. When data was collected, the maximum power obtained was 85 kW at a temperature and pressure of 153 °C and 1.84 MPa, respectively. Biomass-ORC investment is economically competitive, with NPV and LCOE values of 238 kE and 0.93 E/kWh, respectively, and a simple payback period of 24 years for residents with yearly energy needs of 2000 h.