Integration of biodiesel internal combustion engines and transcritical organic Rankine cycles for waste‐heat recovery in small‐scale applications

Abstract

The aim of the work is the analysis of a novel integrated energy system for small-scale combined heat and power (CHP) generation. The system consists of a topping biodiesel-fired internal combustion engine (ICE) and a bottoming transcritical organic Rankine cycle (TORC) for waste-heat recovery. Specifically, the engine exhaust gas provides energy to the TORC sub-system, while the energy contribution of the ICE cooling circuit assures low-temperature heat generation. Furthermore, a thermal energy storage (TES) unit for the exploitation of the thermal surplus and an auxiliary boiler are present. A mathematical model is developed to evaluate the main performances at full and partial load in terms of thermal and electric production, efficiency, fuel consumption, and primary energy saving. A preliminary analysis is carried out to find the proper organic working fluid for the TORC sub-system. Afterwards, the biodiesel ICE-TORC combined system is adopted to satisfy thermal and electric requests of a commercial centre. To this purpose, hourly energy balances are evaluated, and a techno-economic analysis is performed on an annual basis. The investigated system guarantees a 16.7% primary energy saving and an 8.4 years payback time.

Experimental investigation on the performance of a micro-ORC system for different operating conditions

“…Organic Rankine cycle (ORC) systems can be used for combined heat and power generation, making them a promising solution for improving energy efficiency and reducing greenhouse gas emissions in various applications [7]. These systems utilize the principles of the Rankine cycle, typically used in large-scale power plants, but are specifically designed for small-scale and decentralized energy generation [8,9], and offer a viable option to convert thermal energy into electricity and/or usable heat [10][11][12][13]. The selected thermal oil Therminol SP is ideal for applications requiring moderate temperatures up to 300 °C.…”

Experimental Investigation and RSM Modeling of the Effects of Injection Timing on the Performance and NOx Emissions of a Micro-Cogeneration Unit Fueled with Biodiesel Blends

“…Due to its benefits such as renewability, easy producibility, availability, high resulting combustion efficiency, and low pollutants emission, the interest behind the use of biodiesel in traditional compression-ignition engines has grown in the last 20 years [8]. The assessment of its potentiality as a petro-diesel substitute, especially in terms of environmental impact, still represents a research focus for the scientific community [9][10][11][12][13][14]. Critical aspects are related to the controversial issue related to the possible increase in Nitrogen Oxides (NO x ) emissions [15], which are dangerous to humans, causing breathing problems, chronically reduced lung function, and eye irritation and may, in the long run, cause cancers and premature death [16].…”

Thermal stability and pyrolysis mechanism of working fluids for organic Rankine cycle: A review

“…Among them, ORC has the characteristics of low-system cost, high-thermal efficiency, easy operation and maintenance, and variable load adaptability. It is an important technology used to recover effectively industrial waste heat at temperatures below 350 C, and is extensively used to utilize the solar energy, 1,2 industrial waste heat, 3,4 biomass energy, 5,6 and geothermal energy. 7,8 According to the state of the working fluid, ORC systems can be divided into supercritical and subcritical ORCs.…”