Energy Efficiency Of Plant Research Articles

Application of Anammox-Based Processes in Urban WWTPs: Are We on the Right Track?

The application of partial nitritation and anammox processes (PN/A) to remove nitrogen can improve the energy efficiency of wastewater treatment plants (WWTPs) as well as diminish their operational costs. However, there are still several limitations that are preventing the widespread application of PN/A processes in urban WWTPs such as: (a) the loss of performance stability of the PN/A units operated at the sludge line, when the sludge is thermally pretreated to increase biogas production; (b) the proliferation of nitrite-oxidizing bacteria (NOB) in the mainstream; and (c) the maintenance of a suitable effluent quality in the mainstream. In this work, different operational strategies to overcome these limitations were modelled and analyzed. In WWTPs whose sludge is thermically hydrolyzed, the implementation of an anerobic treatment before the PN/A unit is the best alternative, from an economic point of view, to maintain the stable performance of this unit. In order to apply the PN/A process in the mainstream, the growth of ammonia-oxidizing bacteria (AOB) should be promoted in the sludge line by supplying extra sludge to the anaerobic digesters. The AOB generated would be applied to the water line to partially oxidize ammonia, and the anammox process would then be carried out. Excess nitrate generated by anammox bacteria and/or NOB can be removed by recycling a fraction of the WWTP effluent to the biological reactor to promote its denitrification.

Life cycle energy-economy-environmental evaluation of coal-based CLC power plant vs. IGCC, USC and oxy-combustion power plants with/without CO2 capture

Coal-based chemical looping combustion (CLC) power plant presents itself as a promising technology due to its low energy penalty which is associated with its inherent CO2 capture process. However, most evaluations and comparisons (energy efficiency, economic, and environmental aspects) of the CLC power plant generally were focused on the power plant operation stage. Life cycle assessment (LCA) method with a “cradle to gate” model involving power plant construction, operation, and decommissioning stage,of coal-based power plants was established. Following that the resource consumption, energy consumption, environmental impact potential, and economic performance in the life cycle, were comprehensively compared between the coal-based CLC power plant and other plants such as IGCC, USC and oxy-combustion power plants with and without (w/o) CO2 capture, to find out the potential and deficiency of the coal-based CLC power plant in a life cycle perspective. Results showed that energy resource consumption accounts for the largest proportion of the total resource consumption (81.88–91.89%) in six coal-fired power plants. Among the environmental impact potentials, smoke and dust potential (SAP) has the highest value while eutrophication potential (EP) resulted in the lowest in six coal-based power plants. CLC presented resource depletion indicator, energy payback ratio and the total life cycle costs, at 4.79 × 10−6 kWh/person/day, 3.22, and 0.138 $/kWh, respectively. These power plants were ranked from highest to lowest according to their sustainability as the following USC, CLC, IGCC, oxy-CCS, USC-CCS, and IGCC-CCS. However, CLC presents the best sustainability in all coal-based power plants with CO2 capture. The CLC power plant will be one of the most attractive options for carbon reduction in coal-based power systems, as the development of CLC technology further improves energy efficiency and economic performance. The results further demonstrated that the coal-based CLC power plant can solve the issues involving CO2 emission reduction and energy utilization in coal to power generation process from lifecycle viewpoint.

Industrial agglomeration effect for energy efficiency in Japanese production plants

Improving energy efficiency is a highly effective policy for protecting the environment and preserving resources. Previous studies have measured energy efficiency in the industrial sector. We further contribute to understanding the factors that affect energy efficiency changes. This study measures energy efficiency based on plant-level data in Japan's paper/pulp and cement industries as representative energy intensive sectors. We analyze the relationship between the industrial agglomeration effect and the energy efficiency of each studied industry. Our results reflect several important findings. First, energy efficiency has improved in the paper and pulp industry as well as the cement industry between 2000 and 2010. However, the factors for improving energy efficiency differ between the industries. Second, industrial agglomeration affects energy efficiency. In the paper and pulp industry, the same industry agglomerations contribute to improvements in energy efficiency. However, the agglomeration effect is negative for energy efficiency in the cement industry. Our results indicate that one must consider regional circumstances more carefully when seeking to improve energy efficiency.

Increasing the energy efficiency of combined heat power plants by reducing the temperature of the additional feed water of power boilers

The article discusses a fundamentally new technology for increasing the specific generation of electricity based on thermal consumption, and also calculates the effectiveness of the proposed solution. The main distinguishing feature of this solution is a decrease in the temperature of the additional feed water of the boilers of thermal power plants. As a result, a method was developed to increase the specific power generation based on heat consumption by reducing the temperature of the additional feed water of power boilers. The authors have developed a technical solution for the use of gas entering the burners to cool additional feed water through a heat exchanger-cooler; a study of the economic and energy efficiency of the proposed technical solution has been carried out.

Proposal of a Pilot Plant (2T/day) for Solid Fuel Conversion of Cambodian Mango Waste Using Hybrid Hydrothermal Carbonization Technology

하이브리드수열탄화 (Hybrid HTC) ê¸°ìˆ ì€ 2가지 이상의 ìœ ê¸°ì„±íê¸°ë¬¼ì„ 혼합한 특허 받은 열역학 ê³µì •ìœ¼ë¡œ ê³µì •ì˜¨ë„ 180~250oC, ì••ë ¥ 20~40 bar에서 반응시간이 2시간 이내이며 에너지 소비가 ì ê³ , 폐기물의 부피감소 및 ì• ì·¨ ì €ê°íš¨ê³¼ê°€ 크다. 폐기물 중 대부분의 탄소가 ìµœì¢ ìƒì„±ë¬¼ì— ì¶•ì ë˜ë¯€ë¡œ ìœ ê¸°ì„± 폐기물 ê³ í˜•ì—°ë£Œí™”ì— 가장 ì í•©í•œ ê¸°ìˆ ë¡œ í‰ê°€ë°›ê³ ìžˆë‹¤. 본 연구에서는 하이브리드 ìˆ˜ì—´íƒ„í™”ê¸°ìˆ ì„ 활용하여 캄보디아 ë§ê³ íê¸°ë¬¼ì„ 대상으로 온도 및 반응시간의 변화에 따라 발열량 및 수율 등에 미치는 영향에 대하여 평가하였다. 본 연구를 통해 ê³µì •ë³€ìˆ˜ë¥¼ ìµœì í™”í•˜ê³ , ì „ ê³µì •í”ŒëžœíŠ¸ì˜ 에너지 효율성을 향상시킬 수 있으며, ìˆ˜ì—°íƒ„í™”ê¸°ìˆ ì—ì„œ 분해되어 가스가 생성되는데 이때 수소(H2) 및 메탄(CH4) 등 ì œì¡° 및 ìƒì‚°ê¸°ìˆ ê°œë°œì„ í• ìˆ˜ 있다. 본 연구 결과를 í† ëŒ€ë¡œ ë§ê³ íê¸°ë¬¼(2t/day)실증 물질수지 및 에너지 수지 도출과 함께 ê²½ì œì„±ë„ 평가하였다. Hybrid hydrothermal carbonization (Hybrid HTC) technology is a proprietary thermochemical process for two or more organic wastes.The reaction time is less than two hours with temperature range 180~250℃ and pressure range 20~40bar. Thanks to accumulation of the carbon of the waste during Hybrid HTC process, the energy value of the solid fuel increases significantly with comparatively low energy consumption. It has also a great volume reduction with odor removal effect so that it is evaluated as the best solid fuel conversion technology for various organic wastes. In this study of the hybrid hydrothermal carbonization, the effect on the calorific value and yield of Cambodian mango waste were evaluated according to changes in temperature and reaction time. Through the study, parameter optimization has been sought with improving energy efficiency of the whole plant. It is decomposed in the Hydro-Carbonation Technology to Generate Gas. At this time, it is possible to develop manufacturing and production technologies such as hydrogen (H2) and methane (CH4). Based on the results of the study, a pilot plant (2t/day) has been proposed for future commercialization purpose along cost analysis, mass balance and energy balance calculations. Keywords: Hybrid Hydrothermal Carbonization, Cambodia Mango Waste, Pilot Plant, Bio-SRF, Energy Saving, Reduction

Teaching-learning self-study approach for optimal retrofitting of dual mixed refrigerant LNG process: Energy and exergy perspective

This study unfolds the advanced process configuration modification in the evolution of a dual mixed refrigerant (DMR) process for natural gas liquefaction, followed by its optimization through a unique approach i.e., teaching–learning self-study optimization (TLSO). The DMR process is improved by replacing Joule Thomson valves with the isentropic cryogenic turbines. To ensure the maximum possible thermodynamic performance of the retrofitted DMR process, the TLSO paradigm is used and evaluated. The energy, exergy, coefficient of performance, and figure of merit are determined and compared with conventional bench-scale DMR process to find the performance improvement opportunities in the proposed cryogenic turbine-retrofitted DMR process. The performance analysis revealed that the proposed optimal retrofitted DMR process could produce LNG using 28.57% less energy than the base case. The detailed thermodynamic evaluation revealed that the proposed DMR process has 64.68% exergy efficiency, 2.42 coefficient of performance, and 41.6% figure of merit, which are 13.37%, 19%, and 11.9%, higher than the conventional DMR process, respectively. This study would significantly help process engineers overcome the challenges of relating energy efficiency of the LNG plants for both onshore and offshore applications.

Decarbonization of Fossil Energy-intensive Industrial Processes Using Innovative Calcium Looping Technology

Mitigation of fossil carbon dioxide emissions from the main industrial sectors is a key element in the fight against global warming and climate change. In this respect, the main fossil energy-intensive processes (e.g., heat and power generation, cement, iron and steel, chemical applications etc.) are to be decarbonized for the future low-carbon economy. This paper is evaluating the post-combustion carbon capture based on innovative Calcium Looping (CaL) technology to be applied for decarbonization of various fossil-based industrial applications e.g., power generation, cement, iron and steel production. As illustrative cases, relevant industrial size systems are considered (e.g., 1,000 MW power plants, 4 Mt/year steel mills, 1 Mt/year cement plants). As benchmarks, similar processes without carbon capture as well as ones using chemical gas-liquid absorption for carbon capture are considered to assess the energy penalty for decarbonization. The decarbonized systems have 90 % carbon capture rate. As assessment tools a wide range of process systems engineering elements are used as follow: mathematical modelling and simulation using ChemCAD software, model validation based on experimental data, thermal integration analysis using pinch method for optimization of overall energy efficiency, technical and environmental evaluation to quantify the key performance indicators. As the results show, the innovative calcium looping technology for post-combustion carbon capture has significant advantages in comparison to the chemical gas-liquid absorption in term of higher overall plant energy efficiency (by about 2 net energy efficiency percentage points), lower CO2 capture energy penalty (7 - 8 vs. 10 net energy efficiency percentage points), reduced specific CO2 emissions etc.

Thermodynamic performance and economic feasibility of Kalina, Goswami and Organic Rankine Cycles coupled to a polygeneration plant using geothermal energy of low-grade temperature

Low-temperature geothermal energy is an abundant and renewable resource, but with technical and economic limitations for the generation of electricity. Currently, the polygeneration systems are an alternative for effective use of energy resources, geothermal energy included. In this paper a comparative analysis of the thermodynamic and economic performance of Kalina (KAC), Goswami (GOC) and Organic Rankine (ORC) cycles coupled to a polygeneration plant that uses geothermal energy of low-grade temperature to produce electricity, refrigeration and dehydrated products, simultaneously, is presented. It is proposed that the system design operates sequentially at different thermic levels under the concept of cascade utilization. The KAC, GOC and ORC cycles are analyzed as candidates for electricity generation, placed in a first thermal level. In a second thermal level, a cooling technology activated with thermal energy for fresh product conservation is included. Finally, a fresh product dehydrator is included in the last thermal level. To carry out the analysis, a standard structure has been proposed, to which the laws of mass and energy conservation apply. In addition, an exergy analysis is performed to know the performance of the system from the perspective of the second law of thermodynamics. The results indicate that the KAC and ORC cycles are more flexible to integrate, since the systeḿs products can adjust to the predefined needs. However, a better energy and exergetic efficiency of the polygeneration plant is obtained with the ORC, having 30.68 and 27.43%, respectively. From economic perspective the ORC has also the lowest Simple Payback Period (3.36 years) and the highest NPV (1.684 × 106 USD) among power cycles studied.

A framework of energy-consumption driven discrete manufacturing system

Because of big data on energy consumption, there is a lack of research on the discrete manufacturing system. The discrete manufacturing system has plenty of multi-source and heterogeneous data; it was challenging to collect real-time data. Recently, low carbon and green manufacturing is a hot field; especially, it can save electrical energy. This paper proposes a significant energy consumption data of a data-driven analysis framework, which promoting the energy efficiency of discrete manufacturing plant, equipment, and workshop production process. Firstly, put forward the evaluation standards of energy efficiency for discrete manufacturing shops. Then make energy-consumption data preprocessing. Efficiency optimization of big data mining method is put forward based on grid computing function. Design the discrete manufacturing system energy-consumption parameter values, then summarizes prediction algorithms and models in order to predict the results and the trends. Finally, introduce the application of a mobile phone shell manufacturing shop to verify the proposed framework. Further research will focus on energy-consumption data mining processing.

Experimental investigation of the microclimate effects on floating solar power plant energy efficiency

Experimental investigation of the microclimate effects on floating solar power plant energy efficiency

Retrofit design of an industrial natural gas liquids recovery process based on the pinch technology concept

Energy consumption is increasing very rapidly, especially in the high-energy consuming industries such as oil, gas, and Natural Gas Liquids refineries. Pinch analysis as a well-established and successful technique is used to improve the energy efficiency of the above-mentioned plants. However, the limitations on ΔTmin and those related to the technical and economic aspects result in the lack of capability by the pinch analysis in reducing the utility beyond a specific amount. Also, this analysis only uses the existing process streams and cannot identify and develop high potential streams reducing the external utility consumption. Opportunities for saving energy consumption would increase through the self-refrigeration methods, and they further decrease the utility consumption. Moreover, for minimizing the process changes, the Heat Exchanging Network should be optimized by pinch analysis and then, the opportunities for self-refrigeration of the process should also be challenged. Thus, the present study was conducted to consider the opportunities for reducing the energy consumption and the required utility in a real-life case study of a Natural Gas Liquids plant. Finally, the heat exchanging network redesigned by the grass root plant was revamped with side streaming from the demethanizer column by changing the ΔTmin to 3 °C resulting in the provision of an additional refrigeration stream for inlet feed instead of external utility. This scheme resulted in saving 3671 kW of refrigeration compressors shaft work and saving 6100 kW of the needed energy for the reboiler and condenser. As the result, 546 kW (53 %) of the plant's total energy consumption will be saved by the pinch and self-refrigeration scheme. The total savings in the purchased equipment costs and operating costs saving of the NGL plant are equal to 3,891,560 (USD) and 3,757,451 (USD/year), with 378 days' payback period.

Evaluating the energy efficiency of wastewater treatment plants in the Yangtze River Delta: Perspectives on regional discrepancies

With priorities to reach a carbon emission peak and integrated development involving ecological demonstration, a systematic evaluation on the energy efficiency and internal discrepancies of wastewater treatment plants in the Yangtze River Delta region is needed. In this study, a slacks-based measure data envelopment analysis model was applied to quantify the relative energy efficiency of 270 regional wastewater treatment plants. Based on the score of relative energy efficiency, the internal discrepancies of the region were identified through a method combining spatial and sensitivity analysis. Although the wastewater treatment plants had met the pollutant limits of discharge standards, the result of data envelopment analysis showed that 253 wastewater treatment plants were inefficient (with efficiency scores less than 1) due to input excess or output shortfall, indicating substantial potential for improving the energy efficiency. Besides, binary logistic regression demonstrated the significant impact from explanatory factors including designed capacity (104 m3/d), loading rate (%), influent ratio of chemical oxygen demand to total nitrogen, and influent concentration (mg/L) of chemical oxygen demand. Moreover, with regards to regional discrepancies, proportion of efficient wastewater treatment plants for Shanghai, Jiangsu, Zhejiang, and Anhui differs significantly. The area surrounding Taihu Lake was recognized as the trough of the Yangtze River Delta region in terms of the relative energy efficiency of wastewater treatment plants. This paper would give a reference for optimization of wastewater treatment plants in the study area and the evaluation framework on internal discrepancies might also be useful for other regions worldwide.

Development of Co3-xNixO4 materials for thermochemical energy storage at lower red-ox temperature

Heat storage technologies are subject of great research efforts aimed at improving the energy efficiency of power plants and heat recovery processes. In this context, the development of highly efficient and low-cost materials for thermal energy storage is imperative for a large use of this technology. The storage of thermal energy using reversible thermo-chemical reactions can provide large storage capacities especially at high temperatures. Within this class of materials, the red-ox reactions have particular interest due to the low cost of the materials involved (metal oxides) and the use of air both as reacting gas and heat transfer fluid. Therefore, many efforts are doing to improve the efficiency and reversibility of this type of reactions. In this work the synthesis and thermal performances of a novel mixed metal oxide based on cobalt/nickel metals with spinel structure Co3-xNixO4 is reported. A deep study was carried out in order to find the best synthesis conditions and optimum relative metal content in the structure with the objective of decreasing as much as possible the red-ox temperature. The study allowed to determine the optimum Ni content in the oxide structure in order to minimize the reaction temperature. In particular, a linear relationship of the red-ox temperature as a function of the Ni content was observed, enabling reaching red-ox temperature below 700 °C. These results are very promising and open the perspective of using of these types of materials to a wider field of application.

Increased Plant Quality, Greenhouse Productivity and Energy Efficiency with Broad-Spectrum LED Systems: A Case Study for Thyme (Thymus vulgaris L.).

A light-emitting diode (LED) system covering plant-receptive wavebands from ultraviolet to far-red radiation (360 to 760 nm, “white” light spectrum) was investigated for greenhouse productions of Thymus vulgaris L. Biomass yields and amounts of terpenoids were examined, and the lights’ productivity and electrical efficiency were determined. All results were compared to two conventionally used light fixture types (high-pressure sodium lamps (HPS) and fluorescent lights (FL)) under naturally low irradiation conditions during fall and winter in Berlin, Germany. Under LED, development of Thymus vulgaris L. was highly accelerated resulting in distinct fresh yield increases per square meter by 43% and 82.4% compared to HPS and FL, respectively. Dry yields per square meter also increased by 43.1% and 88.6% under LED compared to the HPS and FL lighting systems. While composition of terpenoids remained unaffected, their quantity per gram of leaf dry matter significantly increased under LED and HPS as compared to FL. Further, the power consumption calculations revealed energy savings of 31.3% and 20.1% for LED and FL, respectively, compared to HPS. In conclusion, the implementation of a broad-spectrum LED system has tremendous potential for increasing quantity and quality of Thymus vulgaris L. during naturally insufficient light conditions while significantly reducing energy consumption.

Comprehensive numerical model for the analysis of potential heat recovery solutions in a ceramic industry

Abstract Heat recovery opportunities and total plant energy efficiency improvements need to be evaluated before manufacturing the real components when addressing the energy and economic effectiveness in industrial applications. Numerical modelling of the complete energy systems can be a key design tool in order to investigate the potential solutions to improve the performance of the considered system. In this study, a 0D/1D numerical analysis and transient system simulation analysis are adopted to investigate the energy efficiency enhancement given by the application of a heat pipe-based heat exchanger in the ceramic industry. The thermal power is recovered from the exhaust gases of the kilns used to fire the tiles. The numerical model includes all the main components of the heat recovery system: the primary side of the exhaust gases, the heat exchanger, the secondary circuit of the heat transfer fluid and the heat sink where the thermal power is exploited. Particular care is devoted to the modelling of the heat pipe-based heat exchanger and the necessary control strategy of the system; a specific model for the simulation of the secondary side pump is also accounted for in the analysis. The numerical results of the primary circuit are validated against experimental measurements carried out on the real ceramic facility. The good agreement between the numerical and experimental results demonstrates that the numerical model is an appropriate tool for investigating the energy efficiency enhancement of an industrial plant and for evaluating different configurations and solutions in order to fulfil the industry requirements.

A thermodynamic platform for evaluating the energy efficiency of combined power generation and desalination plants

In seawater desalination, the energy efficiency of practical processes is expressed in kWh_electricity or low-grade-heat per m3 of water produced, omitting the embedded energy quality underlying their generation processes. To avoid thermodynamic misconceptions, it is important to recognize both quality and quantity of energy consumed. An unmerited quantitative apportionment can result in inferior deployment of desalination methods. This article clarifies misapprehensions regarding seeming parity between electricity and thermal sources that are sequentially cogenerated in power plants. These processes are represented by heat engines to yield the respective maximum (Carnot) work potentials. Equivalent work from these engines are normalized individually to give a corresponding standard primary energy (QSPE), defined via a common energy platform between the adiabatic flame temperature of fuel and the surroundings. Using the QSPE platform, the energy efficiency of 60 desalination plants of assorted types, available from literature, are compared retrospectively and with respect to Thermodynamic Limit.

Features of using gas turbine units as a source of electricity and heat at mini - thermal power plants

This article discusses the problem of introducing more resource-intensive methods of generating electricity and heat, the main of which is the use of small-sized gas turbine units (GTU). The creation of a Mini-Thermal Power Plant on the basis of the GTU allows solving the problem of the shortage of heat and electric energy in certain regions, ensuring uninterrupted power supply to the housing and communal sector and industrial enterprises. This is due to the possibility of combined production of heat and electric energy, as well as products and services required in the municipal services of the city. This article presents ways to improve the energy efficiency of thermal power plants through the use of GTU.

Dependence of energy consumptions on the type of mechanical mixer used in the biogas reactor

Purpose. Investigation of the dependence of the energy consumption of mechanical mixers and determination of an energy-efficient type of mixing device to increase the energy efficiency of the biogas formation process and the profitability of further processing into thermal and electrical energy. Methodology. Determination and analysis of energy costs for mechanical mixers, comparison and determination of their energy consumption in the process of biogas formation, generalization of the results. Findings. Biogas technologies play an important role in the formation of a modern energy system. The profitability of which directly depends on the energy efficiency of the processes of intensification of anaerobic fermentation. The process of anaerobic fermentation of waste is long, so one of the main methods of intensification of biogas production is the mixing of waste during anaerobic fermentation. Despite the large number of different types of mixing devices and systems, the main task of mixing is to create a homogeneous substance with the same temperature, acidity and other physicochemical components at any point in the volume of the substance. There is a need to increase the energy efficiency of the processes of intensification of anaerobic fermentation and the profitability of further processing of biogas into heat and electricity. Ways to improve energy efficiency are in certain dependences of the energy consumption of mechanical mixers, the choice of an energy-efficient type of mixer, certain criteria that significantly affect the consumption of electrical energy for mixing, the study of the vectors of propagation of flows created by the mixer. The implementation of these actions will allow you to establish the optimal geometric dimensions of the mixer and significantly increase the energy efficiency of biogas plants and further processing of the resulting biogas into thermal and electrical energy. Originality. The analysis of the reasons for different values of the Euler criterion for mechanical mixers is carried out with the same mode of the substance motion, its level and volume in the tank and other equal parameters. A comparative analysis of energy costs for the most common types of mechanical mixers in biogas reactors is carried out. It has been established that the use of a two-tier paddle mixer, which has two blades per tier, requires the least amount of energy to mix waste in a biogas reactor with a volume . Practical value. The data presented in this paper can be used in the design, construction and modernization of biogas plants. The direction of necessary further scientific researches is determined, the realization of which will increase the energy efficiency of biogas production and the profitability of further processing of biogas into thermal and electric energy.

Benchmarking, Standard Setting and Energy Conservation of Olefin Plants in Iran

Olefin plants are one of the most energy intensive petrochemical plants in the world [1, 2]. In Iran more than 15% of petrochemical products are olefins and it will increase rapidly during next future, so improvement of energy efficiency in olefin plants is key element in NPC (Iranian National Petrochemical Company) plan for cost reduction and sustainable development. In this paper the energy consumption of existing olefin plants are compared with design condition and also world best technology. This comparison indicates the meaningful gap between operational and best condition. In this study the opportunities of energy saving in olefin plants are investigated using process integration tools and benchmarking. The result of this study indicates there is potential for energy consumption reduction up to 25% in Iranian olefin plants.

Energy efficiency of power plants meeting multiple requirements and comparative study of different carbon tax scenarios in Thailand

The most recent power generation policy adopted by the government of Thailand focusses on three different areas: security, to ensure a stable power supply; economy, to ensure that the costs associated with implementation of facilities is appropriate; and ecology, to reduce environmental emissions and social impacts. In order to address these requirements, this study proposes a practical model modification for assessing the energy efficiency of power plants. Specifically, stochastic frontier analysis (SFA) with inefficiency effects was applied to both renewable energy and fossil fuel-fired power plants in Thailand. The empirical results showed that power plant capacity was positively correlated with plant efficiency, and that plant age was negatively correlated with efficiency. In addition, in terms of efficiency scores, renewable power plants tended to be 7.13% more efficient than fossil-fuel plants, and base-load power plants were 9.44% more efficient than peak-load plants. In addition, the efficacy of four different carbon tax scenarios and their effects on the technical efficiency of power plants were evaluated. The results of the tax-rate analysis demonstrated that even low carbon taxes (e.g., 1 USD/tCO2e) can encourage the notable cleaner energy system.