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Improving energy efficiency and reducing environmental impacts have become essential goals in today’s world. Finding ways to utilize waste heat for generating both power and cooling is a meaningful step toward more sustainable energy use and better resource management. In this research, the aim is to enhance the basic efficiency of diesel engines by harnessing the waste heat. By merging the diesel engine cycle with the ORC and the ejector-heat pipe cooling process, we can simultaneously generate power and cooling. This study focuses on tapping into the unused heat from a specific marine diesel engine to produce both power and cooling. The primary motivation is to cut down on fossil fuel usage due to its adverse environmental impact. To put it another way, this research focuses on increasing the base efficiency of diesel engines by recycling waste heat. By systematically integrating the diesel engine cycle with the organic Rankine cycle and the ejector-heat pipe cooling system, we can produce both power and cooling. Ultimately, 2-archive multi-objective cuckoo search algorithm-based optimization (MOCS2arc algorithm) establishes the optimized conceptual design. The system offers an electrical output of 72.01 kW and cooling capabilities of 56.83 kW, achieving an exergy efficiency of 60.4%. Moreover, economic metrics, including the facility’s unit cost of the product ($1259/GJ) and annual exergy destruction costs ($386,670), were ascertained. Under the optimization, exergy efficacy and SUCP of 64.9% and $902.21/GJ are achievable.

This research aims to assess the integration of different fuel cell (FC) options with battery and waste heat recovery systems through a mathematical modelling process to determine the most feasible retrofit solutions for a marine electricity generation plant. This paper distinguishes itself from existing literature by incorporating future cost projection scenarios involving variables such as carbon tax, fuel, and equipment prices. It assesses the environmental impact by including upstream emissions integrated with the Energy Efficiency Existing Ship Index (EEXI) and the Carbon Intensity Indicator (CII) calculations. Real-time data have been collected from a Kamsarmax vessel to build a hybrid marine power distribution plant model for simulating six system designs. A Multi-Criteria Decision Making (MCDM) methodology ranks the scenarios depending on environmental benefits, economic performance, and system space requirements. The findings demonstrate that the hybrid configurations, including solid oxide (SOFC) and proton exchange (PEMFC) FCs, achieve a deduction in equivalent CO2 of the plant up to 91.79% and decrease the EEXI and the average CII by 10.24% and 6.53%, respectively. Although SOFC-included configurations show slightly better economic performance and require less fuel capacity, the overall performance of PEMFC designs are ranked higher in MCDM analysis due to the higher power density.

Nearly 70% of the energy produced from automotive engines is released to the atmosphere in the form of waste energy. The recovery of this energy represents a vital challenge to engine designers primarily when a thermoelectric generator (TEG) is used, where the availability of a continuous, steady-state temperature and heat flow is essential. The potential of semi-truck engines presents an attractive application as many coaches and trucks are roaming motorways at steady-state conditions most of the time. This study presents an analytical thermal design and an experimental validation of the TEG system for waste heat recovery from the exhaust of semi-truck engines. The TEG system parameters were optimized to achieve the maximum power output. Experimental work was conducted on a specially constructed setup to validate the analytically obtained results. Both analytical and experimental results were found to be in good agreement with a marginal deviation, indicating the excellent accuracy of the effective material properties applied to the system since they take into account the discrepancy associated with the neglection of the contact resistances and Thomson effect.

Reactive dyeing is primarily used in the textile industry to achieve a high level of productivity for high-quality products. This method requires heating a large amount of freshwater for dyeing and cooling for the biological treatment of discharged wastewater. If the heat of the wastewater discharged from the textile industry is recovered, energy used for heating freshwater and cooling wastewater can be significantly reduced. However, the energy efficiency of this industry remains low, owing to the limited use of waste heat. Hence, this study suggested a cost-optimal heat exchanger network (HEN) in a heat pump-assisted textile industry wastewater heat recovery system with maximizing energy efficiency simultaneously. A novel two-step approach was suggested to develop the optimal HEN in heat pump-assisted textile industry wastewater heat recovery system. In the first step, the system was designed to integrate the heat exchanger and heat pump to recover waste heat effectively. In the second step, the HEN in the newly developed system was retrofitted using super-targeted pinch analysis to minimize cost and maximize energy efficiency simultaneously. As a result, the proposed wastewater heat recovery system reduced the total annualized cost by up to 43.07% as compared to the conventional textile industry lacking a wastewater heat recovery system. These findings may facilitate economic and environmental improvements in the textile industry.

This paper aims to present the real improvement opportunities of a simple organic Rankine cycle (ORC) as waste heat recovery system (WHRS) from the exhaust gases of a natural gas engine using toluene as the working fluid, based on the exergy and environmental point of view. From the energy and exergy balances, the advanced exergetic analysis was developed to determine the irreversibilities and opportunities for improvement. Since the traditional exergo-environmental analysis, it was found that the component with the greatest potential environmental impact associated with exergy (bF = 0.067 mPts/MJ) and per unit of exergy (ḂD = 8.729 mPts/h) was the condenser, while the exergy-environmental fraction was presented in the turbine (52.51%) and pump-2 (21.12%). The advanced exergo-environmental analysis showed that the environmental impact is more associated with the operational behavior of the components, with 75.33% of the environmental impacts being of endogenous nature, showing that the environmental impacts are generated to a reduced magnitude through the interactions between components. However, it was identified that much of the environmental impacts in ITC 1 could be reduced, with 81.3% of these impacts being avoidable. Finally, the sensitivity analysis results revealed that steel is the material of the components with the least environmental impact.

Background Reducing energy consumption and greenhouse gas emissions is a crucial issue in the cassava starch processing industry. In this study, the integrated system combining livestock, cassava cultivation and cassava production in the same area leads to both a zero emission goal and economic efficiency, a typical example of an effective agro-industrial symbiosis. A heat exchange/recovery system was applied including the economizer, heat exchanger tank, biogas tank, and boiler. The economizer attached to the boiler’s chimney transfers heat from exhaust gases for pre-heating feed water entering the boiler. The biogas tank recovers energy from the wastewater of starch production and livestock, and the generated biogas was used as fuel for the boiler. Results The energy and exergy efficiency, energy losses, and exergy destruction for the heat recovery system were analyzed. The specific energy consumption was used to evaluate the overall energy efficiency for a cassava starch factory with a capacity of 20 tons/day. The results show that there is a high potential to recycle waste into energy in the cassava starch industry. The total energy saving and reduced greenhouse gas emissions per year of the cassava starch factory were 0.054%/year and 123,564 kgCO 2 /per year, respectively. Conclusions Cassava starch factories can save energy and reduce emissions when applying a heat recovery system in the integrated agro-industrial system. Excess heat from the production was used for evaporating (removal of) NH 3 in wastewater flow from the biogas tank, and for heating the biogas system to enhance the efficiency of methane production. A biochar filter was attached to the economizer for adsorption of released ammonium, and the biochar after adsorption was combined with sludge from the biogas tank to produce a solid biofertilizer.

To achieve carbon neutrality and address global energy supply issues by 2050, there is active progress in the industrial sector for waste energy recovery and commercialization projects. It is necessary to consider both the energy recovery efficiency and economic feasibility based on the production volume for the resource utilization of waste energy, along with eco-friendly processing methods. In this study, a waste heat recovery system was designed to recover a large amount of thermal energy from high-temperature exhaust gases of gas engines for power generation by using biogas produced from organic waste in industrial complexes. Types and sizes of components for a waste heat recovery system that were suitable for various engine sizes depending on biogas production were designed, and the energy recovery efficiency was analyzed. The waste heat recovery system consisted of a smoke tube boiler that generated superheated steam at 161 °C under 490 kPa of pressure from the exhaust gas as the heat source, along with two economizers for heating both supply water and hot water. Heat exchangers that were suitable for three different engine sizes were configured, and their performance and energy flow were calculated. In particular, when operating two engines with a power output of 100 kW, the boiler showed the highest steam production efficiency, and the superheated steam production from high-temperature exhaust gas at 600 °C was designed to be 191 kg/h, while hot water at 58 °C was designed to be produced at 1000 kg/h. In addition, further research on the heat exchanger capacity ratio confirmed that it was within a certain range despite the difference in heat exchanger capacity and efficiency depending on the engine size. It was confirmed that the heat exchange capacity ratio of the boiler was important as an optimal-capacity design value for the entire system, as it ranged from 46% to 47% of the total heat exchanger size.

The decarbonization and decentralization of district heating networks lead to the shared use of on-site resources by multiple stakeholders. The optimal design of prospective equipment in such contexts should take into account the preferences and objectives of each stakeholder. This article focuses on the adaptation of a 4E multicriteria model (the criteria being energy, exergy, economic, and exergoeconomic) to include and compare the stakeholders’ performance criteria around the technical design. In addition, two graphical supports are proposed that represent and cross-analyze the different stakeholders’ preferred optima. A preliminary implementation of the methodology is illustrated through a study case in France, which features waste heat recovery for district heating utilization. After presenting the results, a discussion is offered on how to complete the methodology with an iterative negotiation procedure to determine the most suitable design. It was concluded, among other considerations, that the relaxation of the stakeholders’ optimality requirements can greatly enable the project’s feasibility. Such a relaxation could be implemented in the form of a joint consortium. In addition, the results showed that stakeholder relaxations of requirements can lead to new solutions that may outperform the best solutions pre-relaxation. Lastly, perspectives are suggested toward verifying whether relaxed requirements from upstream stakeholders might be more impactful than those of downstream stakeholders.

This study considers incentive provisions for investment decisions related to waste heat recovery system (WHRS) installations on ships to reduce CO2 emissions and improve ships’ engine efficiency. The economic assessment of WHRS installations in the shipping sector is not widely covered in the literature. A reason for this might be that the conventional financial evaluation of sensitive choices is commonly done through capital budgeting methods, which are not flexible enough to integrate future changes in fuel prices and long-term aspects of other costs. Thus, this work evaluates the WHRS investment using the classical budgeting instruments as well as the real-options approach (a more sophisticated approach) to accommodate the presumed expected future changes in the volatile maritime markets. Following the methodology of triangulation, three case studies of ships with varying operational conditions empirically validate the result to depict the practical use of the real-options evaluation method in investment assessment. The capital budgeting analysis reveals that the investment in maritime WHRS technology is only economically favorable under certain frame conditions projected in the work that shows a more realistic assessment of the project.

This manuscript presents an advanced exergo-economic analysis of a waste heat recovery system based on the organic Rankine cycle from the exhaust gases of an internal combustion engine. Different operating conditions were established in order to find the exergy destroyed values in the components and the desegregation of them, as well as the rate of fuel exergy, product exergy, and loss exergy. The component with the highest exergy destroyed values was heat exchanger 1, which is a shell and tube equipment with the highest mean temperature difference in the thermal cycle. However, the values of the fuel cost rate (47.85 USD/GJ) and the product cost rate (197.65 USD/GJ) revealed the organic fluid pump (pump 2) as the device with the main thermo-economic opportunity of improvement, with an exergo-economic factor greater than 91%. In addition, the component with the highest investment costs was the heat exchanger 1 with a value of 2.769 USD/h, which means advanced exergo-economic analysis is a powerful method to identify the correct allocation of the irreversibility and highest cost, and the real potential for improvement is not linked to the interaction between components but to the same component being studied.