1st Law Efficiency Research Articles

Energy Performance of Steam Generation Unit with Using Non-Renewable Fossil Fuel Like Imported (Indonesian) Coal at Spectrum Dyes and Chemicals Private Limited, Palsana-Surat

Now a day’s competition to became power fuel nation is increase industrialization and develop various process or methods for Energy sector. Due to increases energy demand with suitable use of Energy is important for any developing nation. The current case study work is an account of Energetic performance of steam generation unit like Boiler in the Spectrum Dyes and Chemicals Private Limited. The capacity of the Boiler for the steam generation 10 T/Hr. (2 Unit) and 6 T/hr. (1 Unit) coal fired boiler supplied by Rajdeep Boiler, Sachin. After completing the whole 1st law analysis of the Boiler plant has been presented The analysis carried out by using first law for a particular steam generation unit. There are useful assumption is required to analysis during calculations which is introduced in these performance calculations. Microsoft Excel is used for computer programs are developed for performance calculation energetic analysis of a steam generation plant. The PIE chart is graphical represent to energy flow in the system and the losses in the various components during normal operating condition have been identified. The analysis shows that the 1st law efficiency of Boiler Plant with solid Imported (Indonesian) coal fired boiler is 81.43%.

Performance Evaluation of Novel Advanced Recompression Absorption Refrigeration Systems Equipped with Ejector and Vapor Injection Technology

The absorption refrigeration cycle (ARC) faces challenges considering its decreased working pressure and COP. By integrating Recompression technology (RAC) into ARC, these issues are partly addressed. To address these inefficiencies, in this study, ejector and vapor injection techniques are incorporated into refrigerant side of the RAC cycle, resulting in the development of advanced systems: Refrigerant ejector enhanced recompression absorption cycle (RE-RAC) and Vapor injection enhanced recompression absorption cycle (VI-RAC). Key metrics assessed are 1st and 2nd law efficiency, system exergy destruction rate, compressor load, and generator heat requirements. Conclusively, under analogous operating conditions, RE-RAC and VI-RAC demonstrate a substantial improvement in COP, achieving 76 % and 63 % enhancements, respectively, over the standard RAC system. Compared to the conventional solution ejector-based SE-RAC, these systems show performance increases of 28 % and 19 %, respectively. The findings also highlight the sensitivity of these systems to parameters such as generator temperature and pressure, evaporator temperature, absorber temperature, evaporator recovery and normal pressure ratio. At higher evaporator temperature and lower generator temperature, the performance of these systems as well as enhancement of RE-RAC over VI-RAC is higher observed. The optimal value of generator pressure and recovery pressure ratio for maximum efficiency and minimum total exergy destruction rate is also dependent upon these. At a generator temperature of 67 °C and an evaporator temperature of 8 °C, RE-RAC exhibits a 35 % higher COP compared to VI-RAC. However, at −10 °C evaporator temperature, changes in external generator heat input and compressor work reduce the COP enhancement to 5 %.

Comprehensive analysis of energy, exergy, economic, and environmental aspects in implementing the Kalina cycle for waste heat recovery from a gas turbine cycle coupled with a steam generator

This study introduces a transformative approach by integrating the Kalina Cycle System (KCS) within a cogeneration of heat and power (CHP) framework alongside a gas turbine (GT) cycle and a single-pressure heat recovery steam generator (HRSG). Through development of thermodynamic and thermo-economic models, a comprehensive assessment of the system's performance is conducted, emphasizing energy, exergy, and exergoeconomic considerations. The outcomes reveal a remarkable enhancement in both 1st and 2nd law efficiencies for the GT-HRSG/KCS-11 system compared to its conventional counterpart. Witnessing an ascent from 53.60 % to 54.31 % in efficiency and an increase from 50.59 % to 51.27 % in 2nd law efficiency underscores the profound impact of the proposed system. Furthermore, a parametric study scrutinizes the influence of diverse design parameters on critical objective functions, encompassing second law efficiencies and the total system cost rate. Findings spotlight the combustion chamber, heat recovery steam generator, and gas turbine as focal points of exergy destruction, revealing crucial insights for system optimization. The combustion chamber, heat recovery steam generator, and gas turbine emerge as pivotal contributors to the total cost rate, highlighting key areas for economic consideration. According to the results, the share of the environmental cost rates in the system cost rate is insignificant.

System Design, Optimization and 2nd Law Analysis of a 100 MWe Double Reheat s-CO2 Power Plant at Full Load and Part Loads

Super-critical Carbon dioxide (s-CO2) power plants are considered to be efficient and environmentally friendly compared to the traditional Rankine cycle-based steam power plants and Brayton cycle-based gas turbine power plants. In this work, the system design of a coal-fired 100 MWe double reheat s-CO2 power plant is presented. The system is also optimized for efficiency with turbine inlet pressures and the recompression ratio as the variables. The components needed, mass flow rates of various streams and their pressures at various locations in the system have been established. The plant has been studied based on 1st and 2nd laws at full load and at part loads of 80%, 60% and 40%. Operating parameters such as mass flow rate, pressure and temperature have considerably changed in comparison to full load operation. It was also observed that the 1st law efficiency is 53.96%, 53.93%, 52.63% and 50% while the 2nd law efficiency is 51.88%, 51.86%, 50.61% and 48.1% at 100%, 80%, 60% and 40% loads, respectively. The power plant demonstrated good performance even at part loads, especially at 80% load, while the performance deteriorated at lower loads. At full load, the highest amount of exergy destruction is found in the main heater (36.6%) and re-heaters (23.2% and 19.6%) followed by the high-temperature recuperator (5.7%) and cooler (4.1%). Similar trends were observed for the part load operation. It has been found that the recompression ratio should be kept high (>0.5) at lower loads in order to match the performance at higher loads. Combustion and heat exchange due to finite temperature differences are the main causes of exergy destruction, followed by pressure drop.

Detailed assessment of specific exergetic costing, energy consumption, and environmental impacts of a rotary kiln in cement industry.

Türkiyeis one of the biggest developing countries and the second biggest cement exporter in the world. In 2021, the country exported around $1billion of cement, which is responsible for over 8% of emissions globally. In order to fulfill the EU norms, energy, emissions, and cost reduction investments continue in the country. The aim of this paper is to perform a detailed exergoeconomic assessment of a rotary burner to increase the energy and exergy performance and decrease energy consumption, exergy costs and environmental impacts of a real scale cement factory in Türkiye. During the 2-year period, detailed data has been obtained from the factory by real time detection of clinker manufacturing process. By applying the specific exergy costing (SPECO) method, energy and exergy destructions, and exergetic cost distributions for the rotary burner are calculated in detail. The 1st and 2nd law efficiencies of the overall factory, specific energy (SEC) and exergy (SExC) consumption, and SPECO for clinker production are calculated to be 59.84%, 39.04%, 4786.75MJ/ton, 5230.38MJ/ton, and 10.11 $/MJ, respectively. The use of magnesia-spinel composite refractory bricks and the anzast layer formation decreased the SPECO by 2.71% corresponding to a saving of $2,280,000 preventing 13.74 MtCO2 emissions yearly.

Exergy Analysis of a CI Engine Operating on Ternary Biodiesel Blends

Exergy analysis is carried out on a single-cylinder CI engine fueled with biodiesel blends of palm, jatropha and cottonseed oils. This is to identify the blends with high exergy destruction. To this end, experimental and analytical methods were adopted. Three types of biodiesel blends incorporated in this study are primary, binary and ternary. The load was varied as an independent parameter, and mass flow rates of air and fuel, flue gas composition, etc., were measured during the study. Moreover, the chemical composition of the fuel blends and flue gas, as well as their flow rates, were used to determine the total exergy. The output parameters determined were 1st and 2nd law efficiency and fuel exergy destruction under all loading conditions. The inference obtained from the experiment suggests minutely higher 1st law efficiency for the biodiesel blends. Increasing the blending ratio led to an increase in efficiency indices.

Development and comparative selection of surrogate models using artificial neural network for an integrated regenerative transcritical cycle

Surrogate models are becoming increasingly important in replacing the computationally-expensive physics-based simulation models in many applications, such as system optimization, sensitivity analysis and design space exploration. As one of the fastest-growing field, machine learning, specifically artificial neural networks (ANN) have been adapted to model various energy systems. In the present study, five ANN-based surrogate models are developed in replacing the physics-based model of a novel regenerative transcritical power cycle using methanol as the working fluid that is integrated with a small modular reactor. The input layer of the surrogate models consists of the seven design parameters of the cycle, and the output layer returns the 1st-law efficiency, levelized cost of energy and penalty. The evaluation results show that all five candidate surrogate models have demonstrated high R2 score, low relative absolute errors (RAE) and low L1 losses, with the separate multi-layer feed-forward (MLF) neural network model outperforming the others. Once coupled with global optimization, the surrogate model is expected to find the optimal design parameters in order to minimize levelized cost of energy (LCOE) and penalty value in the system.

Multi-objective optimization of thermoeconomic performance for an innovative combined energy system in the supply chain based on externally reformed-Molten carbonate fuel cell

• Triggering a combined heat and power system by biomass gasification. • Integrating Molten carbonate fuel cell with supercritical CO 2 Brayton cycle. • Assessment the effect of crucial design parameters on the system performance. • Maximization of 1st and 2nd law efficiency using NSGAII algorithm. Waste heat elimination via integration techniques has been recognized as an effective solution for the performance enhancement of renewable energy-based power plants. In this paper, a new plant, based on an external reformer molten carbonate fuel cell, is proposed and analyzed. The system consuming the biogas fuel produced by a digester plant. A gas turbine and a supercritical CO 2 cycle are used as bottoming cycles of the proposed layout and its superiorities over the previously developed models are reviewed in terms of thermodynamics, thermoeconomics, and environment. Moreover, a sensitivity analysis is carried out to assess the effect of crucial design parameters on the main performance indexes namely exergy efficiency, net output power, total cost, and the unit product cost of the system. The results indicate that the maximum exergy destruction rate is associated with the water preheater (HX1), and it is followed by the combustion chamber, main heat exchanger, and burner. Further, three-objective optimization is carried out employing the non-dominated sorting genetic algorithm II artificial neural network in MATLAB. Results demonstrate a very great potential in the system to have a higher exergy efficiency of 80.28% which corresponds to the cost of 9.82 $/GJ. Considering the cost and CO 2 emission, the minimum unit product cost of 9.46 $/GJ and minimum CO 2 emission of 354.01 g/MWh can be achievable.

Thermoeconomic analysis and optimization of a hybrid solar-thermal power plant using a genetic algorithm

The hybridization of solar-thermal and combustion technologies for power generation is an emerging concept that brings the possibility to mitigate carbon dioxide emissions while maintaining a firm supply. This work presents a thermoeconomic model for a distributed-scale (<100 kWe) hybrid solar-thermal power plant, developed to study its performance under different operating conditions in a region with a yearly direct normal irradiance of around 1600 kWh/m2 yr. The proposed system consists of a combined Rankine-Brayton cycle with a solar receiver and natural gas combustor working in series as heat sources to the topping cycle. A genetic algorithm was employed to perform a multi-objective optimization of such system, and the result was a set of Pareto-optimal designs, which were compared to a pre-defined reference design. Resulting optimized solutions yield levelized electricity costs as low as 0.179 USD/kWh, as opposed to the 0.237 USD/kWh associated with the reference design. Average 1st and 2nd law efficiencies of up to 27.97 % and 33.53 % were achieved, respectively, which represent increases of up to 7.71 % and 7.31 %. Finally, average solar shares of up to 65 % are possible for optimized designs versus the 58.4 % yielded by the base design.

Is exergy destruction minimization the same thing as energy efficiency maximization?

This paper discusses whether the exergy destruction minimization or energy efficiency maximization comes first in resolving the climate emergency problem and provides sustainable solution options regarding the 2nd Law of thermodynamics. It has been shown that low-temperature district energy systems with renewable energy sources and waste heat are effective in minimizing exergy destructions, while energy efficiency has a secondary impact. The research has been based on the Rational Exergy Management Model. The corresponding rational exergy management efficiency was directly related to nearly-avoidable CO2 emissions responsibility with a global magnitude of around 80% of direct emissions in the built environment. One conclusion deduced from such an unrecognized magnitude so far is that nearly-avoidable CO2 emissions may not be ignored anymore to develop new strategies for sustainable decarbonization, while the 1st Law measures have limited remaining capabilities. New equations were developed to show the impact of exergy destructions on total CO2 emissions. Sample results show that a 30 percent-point decrease of exergy destructions comparing to the supplied exergy in thermo-mechanical systems has the potential of reducing total CO2 emissions by 35%. The paper argues that current exergy destruction is around 0.8 of the supply exergy, as an industry average, which gives ample room for improvement using the 2nd Law, while the 1st Law efficiency is already higher, and there is less room available for improvements concerning CO2 emissions. The paper shows that the 1st Law efficiency may be increased by about 0.15 points, which gives a window of opportunity about a 25 percent-point decrease in emissions. The second main conclusion is that nowadays, new decarbonization strategies are needed based on the 2nd Law, which will positively impact when coupled with the current 1st Law measures towards meeting the Paris agreement.

Comparing the Potentiality of Propane, Propanol and Octane Fuel Using in SI Engine Based on Energy-Exergy Analysis

From the beginning of IC engine era, it is trying to improve the performance and efficiency of internal combustion engine. In this study, numerically analysis on combustion of Propane, Propanol and Octane in SI engine have been done thoroughly and presented to assess the potentiality and highlighted the comparison. For this analysis thermodynamic engine cycle model is developed for numerical analysis. Mathematical models considering fundamental equation and empirical relation are implemented in a single cylinder 4 stroke spark ignition engine (system) with the help of FORTRAN 95 to find out heat losses, friction losses, output parameter etc. Single cylinder four-stroke spark-ignition (SI) engine is considered as system. In this study, different working parameters like 8 and 12 compression ratios with three different rpm 2000, 4000 &amp; 6000 are considered for simulation. This study shows the different comparisons of energy-exergy content (%), as example of exhaust gas 35.08 &amp; 17.82, 37.02 &amp; 19.22, 37.79 &amp; 19.79 for Octane (at compression ratio 8 and 2000, 4000, 6000 rpm) etc., which explains the potentiality content and the potentiality losses in different process like combustion, mixing of gases etc. It also shows for the fuel propane and propanol in similar way with changing different operating conditions. Maximum inside cylinder temperature, 1st law and 2nd law efficiencies were determined for the fuels with respect to different compression ratio and engine speed.

Assessing the use of copper slags as thermal energy storage material for packed-bed systems

Thermocline tanks using packed-bed of rocks have become feasible candidates for improving the performance of Concentrated Solar Power plants, enabling high operating temperatures and reduced capital costs when industrial byproducts are employed as filler materials and low-cost working fluids, being competitive against molten salts thermal storage systems. The present work assesses the potential of using copper slags in packed-bed systems as filler material. Through a thermal characterization, it is demonstrated that copper slags show similar properties to other slags proposed in the literature for thermal storage medium and better thermal capacity (1.4–1.5 J/(gK)). A heat transfer model was developed to predict the cyclic behavior of a packed-bed storage using copper slags and employed in a parametric analysis to assess the impact of storage dimensions on 1st and 2nd law efficiencies for different storage materials, allowing to identify several design considerations depending on tank’s volume. The main findings indicate that the high thermal capacity of copper slags favors the development of a steeper thermocline, keeping a low rate of exergy loss at storage’s outlet, and also higher energy density stored of 138 kWh/m3 against 129 kWh/m3 of other byproducts under similar storage dimensions.

Efficiency of a power generation alternative regarding the composition of feeding biomass-glycerol slurry; theoretical assessment

Following studies on Fuel Glycerol Slurry Integrated Gasification/Gas Turbine (FGSIG/GT) power generation processes, the present investigates the efficiency of a FGSIG/GT alternative regarding the composition of the slurry pumped into the process. Such slurry is prepared by mixing sugar-cane bagasse (SCB) and raw glycerol—a residue of biodiesel production. Differently from previous investigations, the current one considers the alternative where the wet solid fuel is dried before mixing with raw glycerol to form the slurry to be pumped into the gasifier. Such feeding alternative circumvents the use of cumbersome multiple lock-hoppers, usually applied in feeding of particulate solid into pressurized vessels. The stream leaving the gasifier goes through cleaning before being injected into commercial turbines. Energy recovering drives two Rankine cycles. Despite biomass fuel enhancement provided by the glycerol, it has been shown that the highest power generation efficiency can be achieved for slurries with relatively small glycerol content. The 1st and 2nd thermodynamic law efficiencies reached maxima nearing 47% and 36%, respectively. Those values are much higher than the 20% 1st law efficiency currently achieved at sugar mill units as well as the 33% predicted by theoretical studies on Biomass Integrated Gasification/Gas Turbine process consuming only sugar cane bagasse.

Performance assessment of a biomass fuelled advanced hybrid power generation system

This paper deals with the development and detailed assessment of a biomass-fuelled electrochemical power generation system employing biomass gasification, solid oxide fuel cell, gas turbine, and organic Rankine cycle. The performance of the plant has been monitored with the changes in important operating parameters with respect to energetic, exergetic, economic and environmental points of view. The proposed system yields the maximum 49.29% 1st law efficiency and 44.57% 2nd law efficiency. Exergetic analysis reveals that among all the elements of the system, biomass gasifier is the highest (41.22%) contributor in total exergy destruction, followed by the heat exchanger (14.01%), and the organic Rankine boiler (13.27%). Economic analysis reveals that the plant can generate electricity at a minimum rate of 0.0654 $/kWh. The environmental analysis predicts that the proposed system has a maximum CO 2 emission reduction potential of about 2867 tCO 2 /year compared to a coal-fired sub-critical steam power plant of similar capacity, resulting in an environmental benefit value of about 430014 $/year. This study also reveals that the present system is better compared to previously investigated other biomass-fuelled power generation plants considering the efficiency and economy together. • Biomass-based SOFC-GT-ORC system has been conceptualized. • Energetic, exergetic, economic and environmental analyses have been performed. • The system has highest energetic and exergetic efficiencies of 49.29% and 44.57%. • Minimum cost of electricity can reach up to 0.0654 $/kWh. • The system has better thermo-economic results than other biomass-based power plants.

1D thermodynamic modeling for a solid oxide fuel cell stack and parametric study for its optimal operating conditions

Solid oxide fuel cell (SOFC) is regarded as one of the promising energy conversion technologies since it enables distributed power supply based on modularity and provides a high efficiency while emitting less CO2 than conventional power systems. In this sense, a number of SOFC systems have been studied actively aiming at high efficiency with various capacity, assisted by thermodynamic system analysis. However, previous SOFC stack models are not appropriate for the thermodynamic system analysis because those models use multi-dimensional simulation tools and require gross computational resources with excessive calculation time. Thus, in this study, an 1D model that employs analytical expressions with design values and properties measured from an in-house-fabricated SOFC for thermo-electrochemistry and resolves spatially a SOFC stack is developed by using C# to investigate its electrochemical and thermal behavior. The model is validated by using experimental data and is used to elucidate the effect of key operating conditions on thermo-electrochemical performance. A parametric study is conducted with respect to various operation variables such as current density, fuel utilization, air utilization, pressure, and steam to carbon ratio in order to estimate optimal SOFC operating conditions. Considering the effect of each parameter on the 1st law efficiency and outlet gas temperature, a performance map is derived as a function of current density, fuel utilization, and air utilization. To gain the efficiency higher than 50% and outlet gas temperature lower than 900℃, it is shown that the combination of a low current density, high fuel utilization, and low air utilization is necessary at an expense of power density and thermal energy. The results obtained in this study enables capturing optimal operating conditions of a SOFC stack without performing costly experiments.

THERMODYNAMIC OPTIMIZATION OF AN IRREVERSIBLE REGENERATED BRAYTON HEAT ENGINE USING MODIFIED ECOLOGICAL CRITERIA

The modified configuration of regenerated Brayton heat engine along with supplementary addition of heat in its irreversible mode is thermodynamically investigated and optimized. The definite temperature differential between system/reservoir is the source of external irreversibility and the losses because of rubbing/friction in turbine/compressor, regeneration heat losses and losses due to pressure drop are the internal irreversibilities considered in this analysis. The difference of output power and the exergy destruction rate, termed as ecological function, is thermodynamically optimized. It is found that regenerative effectiveness plays a vital role in obtaining maximum possible ecological function whereas output power and 1st law efficiency predominantly depends on the cold side effectiveness in the system. It is also observed that the thermodynamic performance of proposed system/device is prominently depends on the efficiency of the turbine and consequently less dependent on compressor efficiency. The major outcome of this analysis is that with the inclusion of additional thermal heats at constant temperature conditions, various performance parameters i.e., output power (about 13%) and 1st law efficiency (about 9%) of the model get improved significantly in comparison with the conventional gas power plant. Moreover, the model investigated in this study yields lesser output power, first law efficiency and ecological function and exactly follows the results/outcomes presented in the available literature at α1=α2=1, which are the pressure recovery coefficients at two ends.

Performance, emission, energetic and exergetic analyses of a compression ignition engine fuelled with sunflower oil methyl esters

In this study, performance and emission characteristics of sunflower oil methyl esters (sunflower oil biodiesel/SOB) and diesel were studied in between 1400-2600 engine speed. After determining fuel properties, performance and emissions of the test engine, energy and exergy analysis were conducted by using experimental data attained from the experiments. Analyses were performed at 1800 rpm (revolutions per minute) engine speed which gave maximum torque value. With the aid of experimental data and energy balances and exergy rates for the determined control volume which is the whole engine, first and second law efficiencies related with namely quantity and quality were determined for the test fuels, SOB and diesel fuel. Conclusions were evaluated to determine the effects of test fuels on 1st law and 2nd law efficiency performance.

Thermo-economic optimization of a nanofluid based organic Rankine cycle: A multi-objective study and analysis

This paper deals with the thermo-economic optimization of nanofluid based organic Rankine cycle (ORC) system recovering waste heat energy. The main objective of the work is to study the performance of the system by maximizing 1st law efficiency and minimizing levelized energy cost (LEC). Nanoparticles are incorporated into the system by mixing them with the base fluid in the heat exchangers to enhance the heat transfer. Addition of nanofluids enhanced the heat transfer coefficient thus making them compact and cost efficient. Based on the criteria of availability and cost, copper oxide (CuO) nanoparticles are considered and its effect on system performance in terms of thermal efficiency and LEC is analyzed. The effect of pinch point temperature difference for condenser & evaporator, evaporation pressure, mass flow of refrigerant and concentration of nanoparticles is investigated and discussed. The results shows that incorporation of CuO nanoparticles enhance the thermodynamic performance of the system and gives the 19.3% thermal efficiency with LEC of 2.616 $/kWh. Compared to conventional ORC, 3.47% reduction in LEC is obtained in nanofluid based system with higher thermal efficiency. Further, the effect of operating parameters and design variables on the system performance is studied and discussed.

Effect of dry-solid content level in feeding slurry of municipal solid waste consumed by FSIG/GT power generation process; a theoretical study

The theoretical studies on Fuel Slurry Integrated Gasification/Gas Turbine (FSIG/GT) power generation process have progressed. The present focuses on the influence of dry-solid content level (DSC) in the slurry consumed by FSIG/GT process. At the present, the portion of Municipal Solid Waste (MSW)—known as LWTR (letter, wood, textile, and rubber)—fuels the unit. In such a process, the solid fuel is mixed with water to form a slurry, which is pumped into a drier. The dried fuel is fed to a gasifier and the produced gas is cleaned until reaching adequate levels of particle content and sizes, as well alkaline concentrations for injection in commercial gas turbines. Energy recovering is provided by steam cycles. The highest 1st Law efficiency became close to 32% when DSC nears 50%. The results demonstrate that power generation efficiencies are very sensitive regarding the DSC of feeding slurry. Such information might be useful at the decision-taking phase of power generation unit design.

Gaseous fuels variation effects on first and second law analyses of a small direct injection engine for micro-CHP systems

This paper examines the detailed energy and exergy distribution of a 34 cc (cc) air-cooled, two-stroke engine configured to operate on different natural gas (NG) compositions, pure methane, and propane. The engine was developed for application in a small, decentralized combined heat and power (CHP) system. It included optimized intake and exhaust resonators designed from Helmholtz resonance theory to promote effective scavenging. Operation occurred at wide-open-throttle (WOT) at an engine speed of 5400 revolutions per minute (RPM) with low-pressure direct injection (LPDI). Electronic ignition timing was adjusted for maximum brake torque (MBT) while the air-fuel ratio (AFR) was adjusted by injection duration, such that both rich and lean combustion were examined. In addition, start of injection (SOI) was adjusted to balance maximum fuel trapping and combustion stability. Full energy and exergy distribution analyses were completed, as engine operating regimes changed. Exergy was divided into work (available), lost (recoverable), and destructed availabilities. It was found that fuel loss and heat transfer contributed the most to exergy losses, accounting for around 15% and 9% of fuel exergy, respectively. Propane with the highest density, showed the highest in-cylinder trapped energy, heat transfer and, peak utilization factor (UF) of 85.3%. Due to fuel presence in the exhaust, lower 1st law efficiency did not necessarily result into a lower 2nd law efficiency. Higher mixture stratification with propane operation increased carbon monoxide (CO) emissions and hydrogen (H2) content due to rich operation. CO oxidation could recover up to around 5% and 4% of injected fuel energy as heat for CHP system with propane and NG, respectively. Peak 2nd law efficiencies were around 60.5% while peak 1st law indicated efficiency was around 29%. This discrepancy was due to both exhaust hydrocarbon (HC from fuel slip and incomplete combustion) content, exhaust CO content, and heat loss availabilities.