scholarly journals Can a Wastewater Treatment Plant Power Itself? Results from a Novel Biokinetic-Thermodynamic Analysis

J ◽  
2021 ◽  
Vol 4 (4) ◽  
pp. 614-637
Author(s):  
Mustafa Erguvan ◽  
David W. MacPhee
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Energy Demand ◽  
Treatment Plant ◽  
Developed Countries ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet ◽  
Energy And Exergy

The water–energy nexus (WEN) has become increasingly important due to differences in supply and demand of both commodities. At the center of the WEN is wastewater treatment plants (WWTP), which can consume a significant portion of total electricity usage in many developed countries. In this study, a novel multigeneration energy system has been developed to provide an energetically self-sufficient WWTP. This system consists of four major subsystems: an activated sludge process, an anerobic digester, a gas power (Brayton) cycle, and a steam power (Rankine) cycle. Furthermore, a novel secondary compressor has been attached to the Brayton cycle to power aeration in the activated sludge system in order to increase the efficiency of the overall system. The energy and exergy efficiencies have been investigated by varying several parameters in both WWTP and power cycles. The effect of these parameters (biological oxygen demand, dissolved oxygen level, turbine inlet temperature, compression ratio and preheater temperature) on the self-efficiency has also been investigated. It was found here that up to 109% of the wastewater treatment energy demand can be produced using the proposed system. The turbine inlet temperature of the Brayton cycle has the largest effect on self-sufficiency of the system. Energy and exergy efficiencies of the overall system varied from 35.7% to 46.0% and from 30.6% to 33.55%, respectively.

scholarly journals Performance Analysis of the Supercritical Carbon Dioxide Re-compression Brayton Cycle

2020 ◽  
Vol 10 (3) ◽  
pp. 1129 ◽  
Author(s):  
Mohammad Saad Salim ◽  
Muhammad Saeed ◽  
Man-Hoe Kim
Keyword(s):  
Carbon Dioxide ◽  
Performance Analysis ◽  
Supercritical Carbon Dioxide ◽  
Mass Fraction ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Exergy Destruction ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet ◽  
Compressor Inlet

This paper presents performance analysis results on supercritical carbon dioxide ( s C O 2 ) re-compression Brayton cycle. Monthly exergy destruction analysis was conducted to find the effects of different ambient and water temperatures on the performance of the system. The results reveal that the gas cooler is the major source of exergy destruction in the system. The total exergy destruction has the lowest value of 390.1   kW when the compressor inlet temperature is near the critical point (at 35 °C) and the compressor outlet pressure is comparatively low ( 24   MPa ). The optimum mass fraction (x) and efficiency of the cycle increase with turbine inlet temperature. The highest efficiency of 49% is obtained at the mass fraction of x = 0.74 and turbine inlet temperature of 700 °C. For predicting the cost of the system, the total heat transfer area coefficient ( U A T o t a l ) and size parameter (SP) are used. The U A T o t a l value has the maximum for the split mass fraction of 0.74 corresponding to the maximum value of thermal efficiency. The SP value for the turbine is 0.212 dm at the turbine inlet temperature of 700 °C and it increases with increasing turbine inlet temperature. However the SP values of the main compressor and re-compressor increase with increasing compressor inlet temperature.

scholarly journals Thermal Performance Analysis of a Direct-Heated Recompression Supercritical Carbon Dioxide Brayton Cycle Using Solar Concentrators

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4358 ◽  
Author(s):  
Jinping Wang ◽  
Jun Wang ◽  
Peter D. Lund ◽  
Hongxia Zhu
Keyword(s):  
Incidence Angle ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Beam Radiation ◽  
Solar Concentrators ◽  
Cooling Temperature ◽  
Turbine Inlet ◽  
Cycle Efficiency

In this study, a direct recompression supercritical CO2 Brayton cycle, using parabolic trough solar concentrators (PTC), is developed and analyzed employing a new simulation model. The effects of variations in operating conditions and parameters on the performance of the s-CO2 Brayton cycle are investigated, also under varying weather conditions. The results indicate that the efficiency of the s-CO2 Brayton cycle is mainly affected by the compressor outlet pressure, turbine inlet temperature and cooling temperature: Increasing the turbine inlet pressure reduces the efficiency of the cycle and also requires changing the split fraction, where increasing the turbine inlet temperature increases the efficiency, but has a very small effect on the split fraction. At the critical cooling temperature point (31.25 °C), the cycle efficiency reaches a maximum value of 0.4, but drops after this point. In optimal conditions, a cycle efficiency well above 0.4 is possible. The maximum system efficiency with the PTCs remains slightly below this value as the performance of the whole system is also affected by the solar tracking method used, the season and the incidence angle of the solar beam radiation which directly affects the efficiency of the concentrator. The choice of the tracking mode causes major temporal variations in the output of the cycle, which emphasis the role of an integrated TES with the s-CO2 Brayton cycle to provide dispatchable power.

Thermodynamic and Economic Analysis and Multi-Objective Optimization of Supercritical CO2 Brayton Cycles

2015 ◽  
Author(s):  
Hang Zhao ◽  
Qinghua Deng ◽  
Wenting Huang ◽  
Zhenping Feng
Keyword(s):  
Supercritical Co2 ◽  
Exergy Efficiency ◽  
Temperature Cycle ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Multi Objective Optimization ◽  
Turbine Inlet Temperature ◽  
Multi Objective ◽  
Turbine Inlet ◽  
Thermodynamic Performance

Supercritical CO2 Brayton cycles (SCO2BC) offer the potential of better economy and higher practicability due to their high power conversion efficiency, moderate turbine inlet temperature, compact size as compared with some traditional working fluids cycles. In this paper, the SCO2BC including the SCO2 single-recuperated Brayton cycle (RBC) and recompression recuperated Brayton cycle (RRBC) are considered, and flexible thermodynamic and economic modeling methodologies are presented. The influences of the key cycle parameters on thermodynamic performance of SCO2BC are studied, and the comparative analyses on RBC and RRBC are conducted. Based on the thermodynamic and economic models and the given conditions, the Non-dominated Sorting Genetic Algorithm II (NSGA-II) is used for the Pareto-based multi-objective optimization of the RRBC, with the maximum exergy efficiency and the lowest cost per power ($/kW) as its objectives. In addition, the Artificial Neural Network (ANN) is chosen to establish the relationship between the input, output, and the key cycle parameters, which could accelerate the parameters query process. It is observed in the thermodynamic analysis process that the cycle parameters such as heat source temperature, turbine inlet temperature, cycle pressure ratio, and pinch temperature difference of heat exchangers have significant effects on the cycle exergy efficiency. And the exergy destruction of heat exchanger is the main reason why the exergy efficiency of RRBC is higher than that of RBC under the same cycle conditions. Compared with the two kinds of SCO2BC, RBC has a cost advantage from economic perspective, while RRBC has a much better thermodynamic performance, and could rectify the temperature pinching problem that exists in RBC. Therefore, RRBC is recommended in this paper. Furthermore, the Pareto front curve between the cycle cost/ cycle power (CWR) and the cycle exergy efficiency is obtained by multi-objective optimization, which indicates that there is a conflicting relation between them. The optimization results could provide an optimum trade-off curve enabling cycle designers to choose their desired combination between the efficiency and cost. Moreover, the optimum thermodynamic parameters of RRBC can be predicted with good accuracy using ANN, which could help the users to find the SCO2BC parameters fast and accurately.

Recent Advances of Internal Cooling Techniques for Gas Turbine Airfoils

2013 ◽  
Vol 5 (2) ◽  
Author(s):  
Minking K. Chyu ◽  
Sin Chien Siw
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Energy Demand ◽  
Major Elements ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Performance Goal ◽  
Turbine Inlet Temperature ◽  
Air Breathing ◽  
Turbine Inlet

The performance goal of modern gas turbine engines, both land-base and air-breathing engines, can be achieved by increasing the turbine inlet temperature (TIT). The level of TIT in the near future can reach as high as 1700 °C for utility turbines and over 1900 °C for advanced military engines. Advanced and innovative cooling techniques become one of the crucial major elements supporting the development of modern gas turbines, both land-based and air-breathing engines with continual increment of turbine inlet temperature (TIT) in order to meet higher energy demand and efficiency. This paper discusses state-of-the-art airfoil cooling techniques that are mainly applicable in the mainbody and trailing edge section of turbine airfoil. Potential internal cooling designs for near-term applications based on current manufacturing capabilities are identified. A literature survey focusing primarily on the past four to five years has also been performed.

scholarly journals Parametric Investigation and Thermoeconomic Optimization of a Combined Cycle for Recovering the Waste Heat from Nuclear Closed Brayton Cycle

2016 ◽  
Vol 2016 ◽  
pp. 1-12
Author(s):  
Lihuang Luo ◽  
Hong Gao ◽  
Chao Liu ◽  
Xiaoxiao Xu
Keyword(s):  
Mass Fraction ◽  
Waste Heat ◽  
Combined Cycle ◽  
Cycle Performance ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet ◽  
Overall Efficiency ◽  
Economic Analyses

A combined cycle that combines AWM cycle with a nuclear closed Brayton cycle is proposed to recover the waste heat rejected from the precooler of a nuclear closed Brayton cycle in this paper. The detailed thermodynamic and economic analyses are carried out for the combined cycle. The effects of several important parameters, such as the absorber pressure, the turbine inlet pressure, the turbine inlet temperature, the ammonia mass fraction, and the ambient temperature, are investigated. The combined cycle performance is also optimized based on a multiobjective function. Compared with the closed Brayton cycle, the optimized power output and overall efficiency of the combined cycle are higher by 2.41% and 2.43%, respectively. The optimized LEC of the combined cycle is 0.73% lower than that of the closed Brayton cycle.

Testing of a New Turbocompressor for Supercritical Carbon Dioxide Closed Brayton Cycles

2018 ◽  
Author(s):  
Jim Pasch ◽  
David Stapp
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Maximum Pressure ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Development Platform ◽  
Cycle System ◽  
Turbine Inlet ◽  
Supercritical Carbon

Sandia National Laboratories (SNL) has recently purchased a supercritical carbon dioxide (sCO2) turbocompressor that operates at 118,000 rpm, 750 °C turbine inlet temperature, and 42.9 MPa compressor discharge pressure, and is sized to pressurize the flow for a 1 MWe closed Brayton cycle. The turbocompressor is a line replaceable unit designed by Peregrine Turbine Technologies (PTT) located in Wiscasset, Maine, as part of their closed Brayton electric power genset rated at 1 MWe. Both this machine and a 6MW variant are intended for commercial applications burning a variety of aircombustible fuels including biomass materials. Sandia purchased this turbocompressor as the first phase of a program to construct a 1 MWe commercially viable sCO2 recompression closed Brayton-cycle system. During this phase, the development platform resident at the SNL Brayton Lab was reconfigured to support testing of the PTT turbocompressor to moderate, or idle, conditions. The testing infrastructure at the Brayton Lab limited maximum pressure to 13.8 MPa. This pressure limitation consequently limited turbocompressor operations to a speed of 52,000 rpm and a turbine inlet temperature of 150 °C. While these conditions are far removed from the machine design point, they are sufficient to demonstrate a range of important features. Numerous testing objectives were identified and researched, most notably: the development of a reliable cycle bootstrapping process for a motorless turbocompressor; the demonstration of consistent start, steady state, and shutdown performance and operations; performance demonstration of the numerous internal seals and bearings designs that are new to this environment; demonstration of controllability via turbine back pressuring and turbine inlet temperature; and turbomachinery performance map validation. This paper presents the design and development of the testing platform, the PTT turbocompressor and progress achieved on each of the objectives.

Energy and Exergy Performance Comparative Analysis of Solar Driven Organic Rankine Cycle Using Different Organic Fluids

2021 ◽  
pp. 1-38
Author(s):  
Md. Tareq Chowdhury ◽  
Esmail M. A. Mokheimer
Keyword(s):  
Energy Efficiency ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Exergy Efficiency ◽  
Optimum Operating ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet ◽  
Energy And Exergy ◽  
Organic Fluids

Abstract In this study, the performance of Parabolic Trough Collector (PTC) integrated with Organic Rankine Cycle (ORC) is investigated to find the optimum operating scenarios and to assess the exergy destruction at different components of the system. Commercial PTC LS-2 model with Therminol VP-1 as heat transfer fluid was integrated with an organic Rankine cycle that was examined for its thermal and exergetic performance using different organic fluids. It was found that every fluid has an optimum pressure and temperature level at which it works better than other fluids. R134a (Tetrafluoroethane, CH2FCF3) showed the best performance for the turbine inlet temperature range from 340 K — 440 K regarding the achieved energy and exergy efficiencies. At a temperature of 362.8 K and a pressure of 2750 kPa, R134a showed the highest energy efficiency of 8.55% and exergy efficiency of 21.84% with the lowest mass flow rate required in ORC. Energy efficiency of other fluids namely, R245fa (Pentafluoropropane, CF3CH2CHF2), n-pentane and Toluene were less than 5%. On the other hand, Toluene exhibited thermal efficiency of 23.5 % at turbine inlet temperature of 550 K and pressure of 2500 kPa, while the exergy efficiency was 62.89 % at solar irradiation of 1 kW/m2.

Experimental Investigation of an Inverted Brayton Cycle for Exhaust Gas Energy Recovery

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Ian Kennedy ◽  
Zhihang Chen ◽  
Bob Ceen ◽  
Simon Jones ◽  
Colin D. Copeland
Keyword(s):  
Experimental Investigation ◽  
Pressure Drop ◽  
Test Facility ◽  
Inlet Temperature ◽  
Specific Work ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Exhaust Gases ◽  
Turbine Inlet ◽  
System Pressure

Exhaust gases from an internal combustion engine (ICE) contain approximately 30% of the total energy released from combustion of the fuel. In order to improve fuel economy and reduce emissions, there are a number of technologies available to recover some of the otherwise wasted energy. The inverted Brayton cycle (IBC) is one such technology. The purpose of this study is to conduct a parametric experimental investigation of the IBC. The hot air from a turbocharger test facility is used. The system is sized to operate using the exhaust gases produced by a 2 l turbocharged engine at motorway cruise conditions. A number of parameters are investigated that impact the performance of the system such as turbine inlet temperature, system pressure drop, and compressor inlet temperature. The results confirm that the output power is strongly affected by the turbine inlet temperature and system pressure drop. The study also highlights the packaging and performance advantages of using an additively manufactured heat exchanger to reject the excess heat. Due to rotordynamic issues, the speed of the system was limited to 80,000 rpm rather than the target 120,000 rpm. However, the results show that the system can generate a specific work of up to 17 kJ/kg at 80,000 rpm. At full speed, it is estimated that the system can develop approximately 47 kJ/kg, which represents a thermal efficiency of approximately 5%.

scholarly journals Experimental Investigation of an Inverted Brayton Cycle for Exhaust Gas Energy Recovery

2018 ◽  
Author(s):  
Ian Kennedy ◽  
Zhihang Chen ◽  
Bob Ceen ◽  
Simon Jones ◽  
Colin D. Copeland
Keyword(s):  
Experimental Investigation ◽  
Pressure Drop ◽  
Test Facility ◽  
Inlet Temperature ◽  
Specific Work ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Exhaust Gases ◽  
Turbine Inlet ◽  
System Pressure

Exhaust gases from an internal combustion engine (ICE) contain approximately 30% of the total energy released from combustion of the fuel. In order to improve fuel economy and reduce emissions, there are a number of technologies available to recover some of the otherwise wasted energy. The inverted Brayton cycle (IBC) is one such technology. The purpose of the study is to conduct a parametric experimental investigation of the IBC. Hot air from a turbocharger test facility is used. The system is sized to operate using the exhaust gases produced by a 2 litre turbocharged engine at motorway cruise conditions. A number of parameters are investigated that impact the performance of the system such as turbine inlet temperature, system pressure drop and compressor inlet temperature. The results confirm that the output power is strongly affected by the turbine inlet temperature and system pressure drop. The study also highlights the packaging and performance advantages of using a 3D printed heat exchanger to reject the excess heat. Due to rotordynamic issues, the speed of the system was limited to 80,000 rpm rather than the target 120,000 rpm. However, the results show that the system can generate a specific work of up to 17 kJ/kg at 80,000 rpm. At full speed it is estimated that the system can develop approximately 47 kJ/kg, which represents a thermal efficiency of approximately 5%.

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