Energy Efficiency Of Plant Research Articles

Enhancement of energy and cost efficiency in wastewater treatment plants using hybrid bio-inspired machine learning control techniques

Global population growth drives demand for clean water, energy, and wastewater production in urban areas. Most existing wastewater treatment plants (WWTPs) are energy- and cost-intensive. To achieve the UN Sustainable Development Goals (SDGs) by 2030, many regions have implemented strict policies for energy consumption and contaminated water discharge, promoting environmental sustainability. This paper attempts to enhance the achievement of SDGs in the wastewater treatment industry by proposing a novel method for hierarchical control of wastewater treatment plants to ensure energy and cost efficiency with less knowledge of the process model, fewer measurements, and fewer control loops. This controller is the combination of a machine learning control technique with a bio-inspired computational algorithm. To evaluate and validate the performance of the proposed controller on the WWTP, the benchmark simulation model no. 1 (BSM1) has been used. The most significant contributions of this paper show that 488.96 KWh/d, 3620.08 Kg/d, and 3454.55 KWh/d of aeration energy cost index, sludge production cost index, and operational cost index are respectively saved when compared to the default control strategy (DCS). Also, 893.69 Kg pollution units per day of effluent fine-related costs have been successfully recovered when compared to the DCS. The experimental results illustrate that the proposed control yields significant amelioration of the energy and cost profile of the WWTP with no effluent violation in dry, rain, and storm weather conditions.

Performance evaluation and operation optimization of a combined heat and power plant integrated with molten salt heat storage system

Combined heat and power is an effective way to enhance the energy efficiency of thermal power plants. The solar and wind power are intermittent, and dispatchable power sources are critical to balance the supply and demand sides. To facilitate the high penetration of renewable energy, combined heat and power (CHP) plants should provide more and more peak shaving services for the power grid. The thermal energy can be stored in and released from the molten salt heat storage system (MSHSS). The integration of MSHSS can enlarge the adjustable range of the power load of CHP plants, so it is a potential way to enhance the operational flexibility of CHP plants supplying industrial steam and power. In this study, the MSHSS integrated within CHP plants are proposed, which store a part of sensible heat energy carried by extraction steam before supplying to industrial users. The heat storage capacity dominates the flexibility enhancement, and indicators to evaluate energy performances of the proposed system are defined. Moreover, models for the operation optimization of CHP plants integrated with the MSHSS are developed, and a case study of a 350 MW CHP unit is conducted. When the reheat steam is extracted to supply to industrial steam, the maximum and minimum adjustable power loads can be increased and decreased by 17.13 and 12.01 MW, respectively with the integration of the MSHSS. Moreover, during the peak, flat, valley time of reference day, the heat supply coal consumption rates are 73.94, 74.19 and 81.03 kg t−1,respectively. With the operation scheduling of CHP plant integrated with MSHSS, the MSHSS with reheat steam as heat source show the lowest coal consumption rate as 1553.79 ton/day.

Analysis of factors influencing the energy efficiency in Chinese wastewater treatment plants through machine learning and SHapley Additive exPlanations

Wastewater treatment plants (WWTPs) contribute significantly to the control of pollution in water. However, they are significant energy consumers. Identifying the factors influencing energy consumption is crucial for enhancing the energy efficiency of WWTPs. To address this, the unit energy consumption (UEC) of WWTPs was predicted using machine learning models. In order to accurately evaluate WWTPs' energy utilization efficiency, a comprehensive energy evaluation indicator, UEC (kWh/kg TODremoved) was utilized in this study. Among the prediction models, the eXtreme Gradient Boosting (XGBoost) achieves the highest prediction accuracy. SHapley Additive exPlanations (SHAP) was adopted as the model explanation system, and the results revealed that UEC was negatively affected by TN concentration, which was the most influential factor. The stoichiometry-based model calculation result indicates that the nitrification consumes average 77 % of the overall oxygen demand. SHAP analysis illustrated that the UEC of main technologies decreases with increasing influential factors. Partial dependence plot (PDP) compared average UEC of these technologies and SBR consumed the least amount of energy. The research also indicated that low influent TN concentration is the main problem in China. Consequently, it is imperative to exert efforts in ensuring the influent TN concentration while simultaneously making appropriate adjustments to the treatment process. This study provides valuable implications and methods for retrofitting and upgrading WWTPs.

Development of separation and recovery technology of cultured Euglena gracilis using activated sludge for anaerobic digestion

The combination of microalgae cultivation and anaerobic co-digestion of sewage sludge and microalgae is a promising system for increased energy efficiency in sewage treatment plants. This study proposed an innovative separation and recovery technology for microalgae from liquid media after culturing using combined heating and co-sedimentation with activated sludge. Sedimentation and anaerobic digestion experiments were conducted using Euglena gracilis cultures and activated sludge. Combining heating at 40 °C and co-sedimentation resulted in a maximum recovery of 92 %. Activated sludge adsorbed E. gracilis at a ratio of 0.644 μg-Chl. a/mg-MLSS. In anaerobic digestion experiments, no adverse effects such as fermentation inhibition were caused by mixing the activated sludge and E. gracilis. Total energy balance was evaluated assuming a sewage treatment plant with a capacity of 50,000 m3/day. The proposed system is shown to be energy efficient, and increase methane recovery by 24 %.

Improving energy efficiency in ammonia production plants using machine learning

Energy efficiency is becoming increasingly important nowadays due to the need for energy conservation and environmental sustainability. An existing ammonia plant was simulated using Aspen Hysys software, the simulated plant was used to produce large volumes of data to train and test our machine-learning model. In this work a benchmark methodology is proposed through machine-learning (ML) techniques to identify patterns and anomalies in energy consumption. Our ML model was developed in Python programming language using a multiple linear regression algorithm. Microsoft Power BI was used to build interactive visualizations to illustrate insights to users. The ML model was able to predict energy consumption by developing equations that relate the energy consumption and the operating variables for each significant energy user in the ammonia plant. In this study, actual versus optimum energy consumption was analyzed for four ammonia production plants. The ML model identified the ammonia plant operating costs and potential savings by adjusting operating conditions. An annual saving of up to 3.9 million dollars was reached in one of the ammonia production plants operating costs. A reduction in carbon dioxide emissions of up to 4.7 ton per hour was achieved due to energy efficiency adjustment.

Opportunities to Increase the Energy Efficiency of Reservoirs and Hydroelectric Power Plants Using Wind Energy Technologies

The development of technology to stabilize and increase the energy efficiency of hydroelectric power plants in water reservoirs using wind energy technologies represents a significant advancement in renewable energy integration. This study explores the synergistic use of wind turbines and hydroelectric systems to enhance energy production and operational stability. The methodology involved the integration of wind turbines with the existing hydroelectric power infrastructure in water reservoirs. Computational models were used to simulate the combined energy output and assess the performance under various environmental conditions. Additionally, field tests were conducted in a controlled environment to validate the computational models and determine the optimal configuration for maximum efficiency. The stabilization of energy production was also observed, reducing the variability caused by fluctuations in water flow. These results were consistent across different test sites, demonstrating the robustness of the integrated system. By leveraging wind energy to complement hydroelectric power, the proposed technology not only increases energy efficiency but also contributes to a more stable and resilient power grid. This advancement supports the global transition towards cleaner energy sources and offers a viable solution to the challenges faced by standalone renewable energy systems.

An Increase in the Energy Efficiency of Vortex Micro HPP with a Flexible Outlet Siphon by Self-Adjustment of Flows in the Pressure Chamber

The article aims to increase the energy efficiency of the vortex micro-power plant, which would be achieved due to its compatibility with the terrain. In particular, the inlet channel connected to the water intake of the pressure chamber and the water collector placed in the upper pool by transverse joints, and the flexible siphon connected by vertical and horizontal joints to the diffuser of the same chamber with a telescopic end. The boundary conditions were selected with parameters such as the water flow acceleration according to the river bed’s slope angle and the inclination angle of the upstream channel near the vertical pressure cone chamber. The level difference between the upper and lower pools was adjusted. Inside the pressure chamber, the inclined guides of the small wings were hinged to its wall and were adjusted by ballasts. The reactive forces generated by the upward reflection of the incoming flow from the surfaces on the inclined small guide wings of the pressure chamber were a factor in curbing the said flow (compensating for the insufficient volume flow) and ensuring the continuity of the water supply to the turbine in shallow water. The mentioned circumstances allowed for improving the synchronization of incoming and outgoing flows. As a result of the above improvements, an increase in the energy efficiency (i.e., annual electricity generation) of 15–20 % was achieved.

Calculation of geometric dimensions and hydrodynamic characteristics of venturi pipes of a self-draining solar circuit

This research paper provides an increase in the energy efficiency and reliability of self-draining solar plants by optimizing their hydrodimatic operating modes. Based on this goal, the objectives of the study were to analyze the existing methods of protecting solar collectors of water heating and hot water supply systems from freezing and to identify the most promising methods. Also, the identification of the regularities of the hydrodynamics of a self-draining solar circuit.

Thermo-Economic Analysis of Organic Rankine Cycle with Different Working Fluids for Waste Heat Recovery from Coal-based Power Plant

The utilization of waste heat from power plants, which is generally lost to the atmosphere, can reduce energy waste significantly. Heat recovery systems can be integrated with power plants to utilize the waste heat, improving plant energy efficiency and reducing fossil fuel consumption and carbon emissions. The current study is focused on harnessing waste heat through the Organic Rankine Cycle (ORC) from 500 MWe supercritical power plant with CO2 capture. The simulation flow sheet program “Cycle-Tempo” models and simulates different plant layouts. This study considered five different working fluids for ORC, such as R245fa, Benzene, Methanol, Ethanol, and Acetone. The ORC generates additional electricity of 9.91 MWe for R245fa, 14.11 MWe for Benzene, 13.71 MWe for Methanol, 14.04 MWe for Ethanol and 13.97 MWe for Acetone. The thermodynamic study concludes that ORC based on benzene is the best, and the economic analysis discloses that ORC based on ethanol is the best among all working fluids with a payback period of 0.869 years and cost of electricity of Rupees 1.101 per kWh. This study also concludes that the novel technique used in the present study is economically viable, contributing to a more energy-efficient and environmentally friendly power generation system.

The Exergy and Energy Analysis of Change Phase Steam in Patuha Geothermal Well Production

A Geothermal Power Plant Company in West Java Indonesia have capacity around 55MW. It company have increased the well production quality to keep up the Indonesia's energy demands. The power plant has been operated around ten years, it has ten geothermal production wells and two injection wells. The either of it wells has an abnormality. It wells has water dominated condition so, the separator equipment is required to separate the steam from water and vapor. Previous study indicated that subsurface water entering the broken reservoir pipe. That leaks in reservoir pipe was repaired in 2020. The impact after the pipe have been repaired it made the fluid characteristic of reservoir be vapor dominated. After that a separator as a steam separator is no longer required. The study compares the value energy and exergy power of the power plant. The calculations are performed from the well reservoir and all power plant equipment. According to the results of the energy study, the plant's energy efficiency after the transformation increased by 0.03%, from 19.48% to 19.52%. The exergy value of the brine in either wells (separated steam cycle) is also known to be 2.512,52 kW, beyond which the value will become zero.

Can China's regional carbon market pilots improve power plants' energy efficiency?

Power plants are facing huge climate change and policy risks. This paper identifies the effect of China's carbon emissions trading system (ETS) on plants' energy efficiency. For this purpose, we use a two-step approach. In the first stage, we apply a Meta-frontier Stochastic Frontier Analysis (MSFA) method to estimate the total-factor energy efficiency of China's large coal power plants. In the second stage, we use a bootstrapped truncated difference-in-differences (BT-DID) estimator to investigate the ETS' impact on power plants. Results show that the ETS trading policy significantly improves participating plants' energy efficiency by 0.043, compared to non-ETS plants, while the announcement policy doesn't. Besides, several other methods are introduced to solve the potential autocorrelation and heteroskedasticity problems in the second-stage regression. Further, we unveil that the trading policy improves plants' energy efficiency by reducing coal consumption without affecting power generation. Finally, the heterogeneity analysis proves that China Southern Power Grid, local plants, and plants with high carbon prices benefit more from ETS.

Heat Storage as a Way to Increase Energy Efficiency and Flexibility of NPP in Isolated Power System

This paper considers a thermal accumulator using phase transition materials as a way to increase the energy efficiency and maneuverability of nuclear power plants. A low-power nuclear power plant is the object of this study. Such nuclear power plants have a great potential for widespread implementation as sources of thermal and electrical energy for facilities of mineral and raw material as well as fuel and energy complexes located in distant regions. The main principles of development of low-power nuclear power plants are revealed. So, in the development of low-power nuclear power plants, experience in the creation and operation of shipboard nuclear power installations is widely used. The problems of NPP operation in daily maneuvering modes within an isolated power system are revealed. A method for improving the energy efficiency and maneuverability of nuclear power plants is proposed, in particular, through the use of thermal accumulators with a phase change material directly in the NPP circuit. A method of assessment of the dimensions of the heat accumulator and the amount of heat accumulating material is presented. A method of assessment of the efficiency of the accumulator application scheme is presented. The thermal scheme of a promising low-power nuclear power plant with an RITM-200 reactor is compiled. A scheme for switching on a heat accumulator with a phase change material to a scheme for regenerative heating of a turbine is proposed. The heat storage material selection is made, the main elements and characteristics of such an accumulator are determined, and the parameters of the heat transfer fluid’s movement through the accumulator are determined. A mathematical model of the heat exchange in an accumulator based on the finite difference method is compiled, and the simulation results are presented. The results of the experimental verification of the model are presented. As a result of the calculation of NPPs’ thermal schemes in the standard version and the version with a heat accumulator, the power increase in the turbine plant due to the application of accumulated heat in the accumulator discharge mode is determined.

Pumps as HPRTs

Using centrifugal pumps as hydraulic power recovery turbines (HPRTs) to maximize plant energy efficiency, profitability, and sustainability.

A comparative study of polyamine and piperazine as promoter for CO2 absorption performance in aqueous methyldiethanolamine blend system: 430 MW power plant data simulation and economic assessment

Fossil fuel power plants play a significant role in fulfilling global energy demands but are also responsible for high CO2 emissions. Amine-based post-combustion CO2 capture (PCC) is one of the technologies used in such power plants to reduce CO2 emissions. However, high energy consumption in amine-based PCC technology causes a reduction in the overall energy efficiency of power plants. The energy consumption significantly depends on the solvents used in the PCC process. Therefore, in this work, we performed CO2 absorption in the piperazine (PZ), triethylenetetramine (TETA), and N-methyldiethanolamine (MDEA) blend and tri-blend solvents. For the absorption performance and energy consumption calculation, a simulation is performed for the 430 MW power plant data in the DWSIM software. Initially, solvent screening was done, and four solvents are selected based on the optimum energy consumption of various solvents. Further, the solvents’ performance in terms of energy consumption is done based on the effect of different temperatures, CO2 composition in feed, and %CO2 recovery. Overall, the TETA+PZ MDEA tri-blend solvent showed optimum energy consumption for most of the conditions. Additionally, a techno-economy assessment was done considering annual capital cost and annual operating cost, and results revealed that the cost per ton of CO2 capture in 5 %TETA+ 5 %PZ+ 20 %MDEA solvent is 27.33 % lesser than industrial MEA solvent, and 1.56 % lower than 10 %PZ+ 20 %MDEA.

Comprehensive energy efficiency optimization algorithm for steel load considering network reconstruction and demand response

Industrial loads are usually energy intensive and inefficient. The optimization of energy efficiency management in steel plants is still in the early stage of development. Considering the topology of power grid, it is an urgent problem to improve the operation economy and load side energy efficiency of steel plants. In this paper, a two-level collaborative optimization method is proposed, which takes into account the dynamic reconstruction cost, transmission loss cost, energy cost and demand response benefit. The upper level objective is the optimization of topology in the grid structure to optimize the power loss and dynamic reconstruction costs of the grid. The lower level is the energy cost considering demand response, real time price and dynamic demand response price. Firstly, the mathematical models of stable load, impact load and the steel production line load are built. The key parameters are identified by the Back Propagation neural network algorithm according to the actual production data. Secondly, considering the constraints of grid structure and load operation capacity, the impact of dynamic grid loss and real-time dynamic electricity price on the energy efficiency of the whole grid are analyzed in depth. The optimal operation model considering the dynamic reconfiguration and grid tramission loss of distribution network is built. Taking a steel plant park in Northeast China as an example, it is proved that the optimization model can improve energy efficiency on the load side by optimizing energy consumption and demand response participation time on load side. The energy cost is reduced by 17.77% on the load side, the network loss is reduced by 1.8%, and the operating cost of the power grid is reduced by 26.2%, which has a positive effect on improving energy utilization efficiency, reducing distribution network loss, and improving overall economic efficiency.

Study of the possibilities of using natural gas for cooling various coolant flows at combined heat and power plant

The article discusses the application of two technologies for cooling different coolant flows at the CHP and makes a comparative assessment of their impact on the energy efficiency of the turbine plant. The first technology consists in cooling the feed water flow of the heating system, and the second technology is implemented by cooling the additional feed water of boilers. The technology of cooling the make-up water of the heating system provides for introducing a heat exchanger that would cool the make-up water before mixing it with the water of the heating system. The technology of cooling the additional feed water of boilers is implemented by introducing a heat exchanger downstream the deaerator, before feeding the water into the main condensate path. In both cases, in the heat exchanger, the cooling medium is natural gas supplied to the burners of boilers, and the heating medium is make-up or additional feed water. A comparative calculation of the energy efficiency indicators of technologies is performed using the method of specific electricity generation based on thermal consumption. During the calculations, the data obtained at an operating CHP plant and the temperature schedule of a heating network for the 2021 – 2022 heating season were used. Calculations were performed for a thermal power plant with a T-100-130 turbine. For the most accurate comparison of the effectiveness of the technologies under consideration, the source data were taken as close as possible, and the value of the make-up water and additional feed water consumption correspond to each other — for this reason, the heating season period was considered. The outdoor temperature values for the specified period were taken from the weather archive of a weather station. Comparative results of calculations of the efficiency indicators of the use of these technologies are presented, expressed in additional heating generation of electricity, in the economy of conventional fuel and in monetary terms over the heating period.

Повышение эффективности использования твердого топлива на промышленных ТЭЦ

Currently, in this country solid fuel at industrial thermal power plants, as a rule, is burned by a layer or flaring method in boilers with generation of steam which is directed to a steam turbine. This technology of generating thermal and electrical energy is characterized by relatively low efficiency and significant emissions of pollutants into the atmosphere. At the same time, the use of solid fuel in industrial energy with its preliminary gasification can significantly increase the efficiency of electricity generation and at the same time reduce the negative impact on the environment. The results of an analytical comparison of two schemes to use solid fuel in industrial energy are used as the material of the research. These two schemes are a traditional scheme and an alternative one based on its preliminary gasification. In this paper, to assess the effectiveness of the schemes under consideration, the scientific methodology of system analysis is applied. It allows us to consider any energy object as a unified system consisting of interrelated elements. The system analysis is carried out based on mathematical modeling of the technological process to obtain thermal and electrical energy. A complex balance mathematical model of an industrial thermal power plant with preliminary coal gasification is developed. The results of calculation using a mathematical model have shown that the construction of industrial combined‒cycle thermal power plants with preliminary coal gasification instead of traditional steam turbine ones will increase the key indicator of the energy efficiency of thermal power plants, coefficient of fuel utilization from 60 to 74 %. Based on the methodology of system analysis, an optimal thermal scheme of an industrial combined-cycle thermal power plant with preliminary coal gasification has been developed. Numerical values of the basic operating conditions of the thermal power plants and energy efficiency indicators have been determined using a mathematical model. The use of solid fuel at industrial thermal power plants with its preliminary gasification is a very promising direction to develop industrial energy in Russia since this method to extract the bound chemical energy of solid fuel can significantly increase the fuel utilization coefficient and the production of electrical energy and at the same time reduce emissions of contamination material into the atmosphere

Design and energy, exergy, and exergoeconomic analyses of a novel biomass-based green hydrogen and power generation system integrated with carbon capture and power-to-gas

The conversion of thermal energy into electrical power through combustion in combined cycle power plants is a prevalent method of energy conversion. Sustainable energy management requires effective energy storage, and power-to-gas (P2G) technology is a recent solution to this problem. In this research work, a novel biomass-based power plant is proposed, this specific type of biomass is composed of industrial wood chips and wheat straw chopped wood with a 3.48:1 mass ratio and 19 wt% moisture. Detailed energy, exergy, and exergoeconomic analyses are performed for each component, considering various ambient and system conditions. This power plant is also equipped with a carbon capture and storage system, by which combustion's carbon dioxide is separated, and a power-to-gas energy storage system, by which hydrogen and oxygen gases are produced, allowing it to produce synthetic natural gas by the methanation process with various industrial applications and reduce carbon emissions. The energy and exergy analyses show that the overall energy efficiency and exergetic efficiency of the plant are 56.49 % and 35.48 %, respectively, which are highly acceptable and feasible. The combustion chamber is the primary location of exergy destruction, accounting for 52 % of the total exergy destruction in the cycles, followed by the methanation unit (15 %) and the turbine (12 %). Furthermore, the effect of modified ambient and manual operational parameters on the overall performance of the plant is analyzed, increasing the gas turbine inlet temperature improves the plant's energy efficiency to 57 %; but leads to a negative impact on its exergy efficiency (32 %), which manufacturing barriers make it difficult to increase beyond 1600 °C. Building the plant in a warmer geographic location barely impacts the energy efficiency; however, it may cause a decline as high as 1 % in the exergy efficiency.

Energy and exergy assessment of 750 MW combined cycle power plant: A case study

As global energy demand continues to rise, the imperative to explore and enhance energy generation from existing resources intensifies. Combined cycle power plants (CCPPs) have emerged as a promising solution to improve efficiency and electricity production. In this study, we present a comprehensive analysis of the thermodynamic performance of a 750 MW CCPP located in Assiut, Egypt, with a focus on its energy and exergy efficiency. Our investigation reveals critical insights into the CCPP's operational dynamics. Notably, the combustion chambers emerge as the primary contributors to exergy destruction, accounting for 53.3 % of the total exergy loss. Heat recovery steam generators (HRSGs) follow closely at 32 %, while compressors, steam turbines, gas turbines, and cooling systems contribute 5.3 %, 5 %, 2.3 %, and 1.7 %, respectively. These findings pinpoint specific areas where exergy losses are most significant, offering valuable guidance for targeted improvements in CCPP performance. Furthermore, we report that the overall energy efficiency of the entire plant stands at 34.6 %, with an exergy efficiency of 33.5 %. In summary, our study provides a comprehensive scientific assessment of the thermodynamic performance of a 750 MW CCPP. The specific insights into exergy destruction and efficiency metrics not only contribute to our understanding of CCPPs but also offer actionable recommendations for optimizing the operation of gas turbine based CCPPs. These findings hold significance in the broader context of energy sustainability and environmental considerations.

Economic feasibility of retrofitting blowdown heat recovery system using steam dryer to lignite-fired power plant for reduced fuel consumption

Blowdown is responsible for heat losses in boiler systems. The main objective of this paper is to propose a system to recover blowdown heat using steam dryer. The system consists of a flash tank, a steam dryer, and an air preheater. The flash tank is used to produce flash steam that is supplied to the steam dryer. Fuel moisture is removed in the steam dryer, resulting in fuel with lower moisture content and exhaust vapor. Exhaust vapor is supplied to the air preheater to increase air temperature before combustion. Due to lower fuel moisture content and higher air temperature, exhaust flue gas temperature can be decreased by adding air heater area. An analysis was performed to determine the payback period for the investment cost of the proposed heat recovery system. It was demonstrated that retrofitting a power plant with this system led to increased energy efficiency of the power plant. A case study of 250-MW existing power plant operating at the boiler pressure of 12.34 MPa was considered. Simulation results indicate that the power plant retrofitted with this blowdown heat recovery system consumes 0.87% less fuel than the power plant without this system. The payback period or the investment in this system is 7 years.