Efficiency and Emissions Measurement of a Stirling-Engine-Based Residential Microcogeneration System Run on Diesel and Biodiesel

Abstract

Concern with climate change and energy security has generated interest in both cogeneration and biofuels. This experimental study examines the performance of a residential microcogeneration system based on a Stirling engine fueled by diesel and biodiesel. Run on diesel, the system achieves a power efficiency of 11.7% and a heat efficiency of 78.7%. The corresponding efficiencies for the system, when run on biodiesel, are slightly lower at 11.5% and 77.5%, respectively. Particulate emissions for biodiesel are 69.2 mg/kWh, an order of magnitude higher than that of diesel (2.3 mg/kWh). The total unburned hydrocarbon emissions for biodiesel are higher than those of diesel. Emissions of carbon monoxide, nitrogen dioxide, methane, acetylene, ethylene, formaldehyde, and acetaldehyde are comparable between diesel and biodiesel, but nitric oxide emissions for diesel are observed to be higher at 151 ppm compared to those for biodiesel (117 ppm). The difference in the performance of the system is generally attributed to higher boiling range compounds in biodiesel that affect the flame stability, the fuel evaporation, and the complete burnout of the fuel. The system achieves energy efficiencies comparable to those of internal-combustion-engine-based and fuel-cell-based cogeneration systems.

Experimental Determination of the Efficiency and Emissions of a Residential Microcogeneration System Based on a Stirling Engine and Fueled by Diesel and Ethanol

“…27 Also, mean cycle pressures in the range of 10−20 MPa are required to achieve high power efficiencies, whereas the working fluid of this engine was pressurized to only 2.8 MPa. 32 A similar study by Aliabadi et al 10 revealed a thermal output of 7.4 kW and a LHV energy efficiency of 90.5% when powered by diesel fuel, values larger than those obtained in this study. This is likely a consequence of their measurements being recorded during the absorption-charging stage in which electricity from the battery is used to generate heat.…”

“…Featuring a natural gas burner and producing 2−9 kW of power and 8−24 kW of heat, emission levels were fairly low with 80−120 mg/m 3 of nitrogen oxides (NO x ), 40−60 mg/m 3 of carbon monoxide (CO), and trace levels of unburned hydrocarbon (UHC) and soot emissions. An efficiency and emissions study has also been conducted by Aliabadi et al 10 on a residential Stirling enginebased cogeneration system developed by Whisper Tech. The system features a diesel fuel burner and produces 0.6−1.1 kW of power and 5.5−7.0 kW of heat.…”

Numerical Investigation of Thermofluid Performance of a Regenerator Relative to the Matrix Geometry

“…The actual efficiency of a Stirling engine is about 20-60% of this [4] with the departure coming from friction losses and thermal irreversibilities in the system [9]. Similarly, achieving high system temperature necessary for improved efficiency is constrained by material limitations, while the desired low regenerator exit temperature requires an increased surface area which introduces friction into the system with resultant undesirable pressure drop [10].…”

Biomass-fired combined cooling, heating and power for small scale applications – A review

“…It is based on findings from different sources as well as on the authors' judgement. Up to 2 MW [25] Up to 150 kW [2] up to 2 MW [2] Up to 1,000 kW [21] Advantages Very high reliability (with clean fuels) [21,45] Rapid start-up [21] Low investment costs [21] Excellent partial load performance [25] Very high electric efficiency [5,21] Low noise [45] Low emissions [5,21] Can use low quality fuels due to external combustion [21,25,32] Good partial load performance [12,25,32] Potentially low maintenance requirements/ less moving parts [21,46] High thermal efficiency [5] Low emissions [5,32] Can run with low grade heat [12] High reliability [12,47] Low maintenance costs [5,48] Good partial load behaviour [47] Low quality fuels can be used for externally driven units [21] Very few moving parts [21] Very compact sizes [21] High temperature exhaust [45] Low emissions [45] Disadvantages Short maintenance intervals [21,45] Instability with bioand syngas/ limited fuel flexibility [21,48,49] High noise [45] High NOxemissions…”