Single Generation System Research Articles

Near-zero emission trigeneration system coupling molten salt methane pyrolysis with solid oxide fuel cell based on carbon capture and utilization: Thermodynamic and exergoenvironmental evaluation

Natural gas-based energy systems have garnered widespread attention for their potential to facilitate the transition from traditional to renewable energy sources. Among these, methane pyrolysis technology stands out as a promising pathway. Consequently, a novel methanol-electricity-carbon trigeneration system featuring methane pyrolysis coupled with chemical looping combustion, methanol synthesis, and solid oxide fuel cell unit was designed. To validate this innovative concept, thermodynamic model of the process was developed. Compared to conventional single-generation system, the proposed system demonstrated superior thermodynamic performance, with energy efficiency of 69.51 %, representing improvement of 28.78 %. Sensitivity analysis indicated that optimal carbon utilization-to-storage ratio of 0.68 effectively balanced environmental benefits with energy conversion efficiency. Additionally, the CO2 capture rate and emission of the proposed system reached impressive 99.24 % and 2.15 kg/MWh, respectively, confirming its carbon mitigation potential. Based on this, exergoenvironmental analysis demonstrated that rb,k of the novel system was 21.14 %, indicating room for further environmental impact reduction. Moreover, due to the high rb,k of 16.61 % for the preheater-2 identified as a key component for optimization. Finally, the economic analysis verified the system’s feasibility, showing the annual net income of 6774.06 k$. This novel concept highlights the potential of natural gas-based systems in optimizing carbon utilization and energy efficiency, contributing to a more environmentally sustainable energy infrastructure.

Techno-economic Optimization of an Offshore Hybrid Power System: Argentine Basin Case Study

Ocean observation and monitoring relies on data gathered from multiple sources including gliders, cabled observatories, underwater vehicles, and moored buoys. Moored buoys, augmented by resident autonomous underwater vehicles, are potentially well-suited to long-term oceanographic data collection with the resolution and scope of data collection increased by utilizing in-situ power generation. While power needs could be provided by a single generation source (e.g., diesel generator, solar photovoltaics, or wave energy converter) with battery backup, a hybrid power system can potentially smooth seasonal variations that would otherwise require large generation and storage capacities, and be tailored to a locations’ resource availability. By reducing system size through hybridization, we have the potential to reduce overall system cost. To this end, we developed an optimization model that defines the generator and storage capacities of the cost-optimal hybrid power system for a given location and load profile. The model considers generation by wave energy converters, wind turbines, solar photovoltaics, diesel generators, and current turbines with a battery for energy storage. The model uses the defined load profile and location specific time series of resource availability for a time-domain simulation of the power generated and battery state of charge. Based on the power system size, mooring, and mission specific maintenance schedule, the model calculates capital and operating costs for each potential combination of generation and storage capacities. The optimization model searches the 6-dimensional design space to find the lowest cost system that can satisfy the load requirements. In this paper, we focus on a case study of a hybrid power system serving an ocean observation buoy with a resident autonomous underwater vehicle located at the Mid-Atlantic Shelf Break. Diagnostic metrics such as the cost-breakdown and generator capacity factors are evaluated to understand cost drivers and draw comparisons to the costs of single generation systems. Additionally, the model sensitivity to key assumptions such as battery life, maintenance vessel cost, survival loads, and required persistence are discussed.

A new solar and wind integrated sodium fast reactor with molten salt to generate multiple useful outputs with hydrogen

The current study proposes the integration of renewable and nuclear energy systems in a hybridized manner to produce multiple useful outputs with synergetic benefits compared to single-generation systems. The proposed integrated energy system is designed to fully meet the power, heating, cooling, freshwater, and transportation requirements of communities and balance the grid, which consists of an offshore wind farm, a floating photovoltaic plant, a sodium-cooled fast nuclear reactor, a molten salt storage system, a steam-based power generation unit, a lithium-bromide absorption chiller, an anion exchange membrane (AEM) electrolyser, a multi-effect desalination unit and a district energy system. The proposed system is also analyzed from the energy and exergy aspects of thermodynamics. Additional modelling and simulations are carried out with time-dependent analysis in a case study for a residential community, which consists of approximately 275,000 of people in California, the United States. The proposed system with 345 MWe, 1,000 MWth sodium-cooled fast nuclear reactor, 100.8 MWe offshore wind farm and 100 MWp floating PV plant is analyzed with changing parameters throughout the year. Furthermore, the overall system is found to be fully sufficient to meet 1,551.4 GWh of non-thermal electricity load, 820.3 GWh of cooling load, and 2,324.8 GWh of heating load. Moreover, to exploit the excess energy and recover the waste energy, to produce more than the triple amount of the freshwater requirement of the community with 39,575,634 tonnes of fresh water and exceeds the transportation fuel requirement of the community with a total of 28,713 tonnes of hydrogen. The highest monthly average energy efficiency is found for the month of December as 72.54%. On the other hand, the highest monthly average exergy efficiency is found for the month of October as 61.11%. The average energy and exergy efficiencies for the overall system are found 63.36% and 52.42%, respectively.

Memetic SSA tuned fractional PSS for low frequency power system oscillations

Memetic salp swarm algorithm (MSSA) is proposed in the present work to optimally set the gains of fractional power system stabilizer (FPSS) for damping angular speed variation in power system. The optimization is based on the objective of minimizing variation in rotor angular frequency subject to disturbance which is change in reference voltage applied to generator. A single generator system connected with infinite bus has been experimented in this work for sudden and random variations in reference voltage applied to generator. The power system stabilizer (PSS) is based on fractional lead-lag control actions and MSSA is employed to tune the controller gains. Eigen values are analyzed with proposed control and MSSA has been compared with PSO (Particle swarm optimization) and salp swarm algorithm (SSA). It is observed from system response that MSSA can effectively tune the PSS parameters for oscillation damping subject to critical disturbances like random reference voltage variations.

Evaluation of the Symmetrically Switched Converter Structures on the Frequency Regulation of Standalone Micro Hydro Power Plants

Micro hydro power plants (µHPP) are typically used to supply electric energy to microgrids outside the national power grids taking care of the frequency control of the isolated system. A conventional way to maintain the load balance in the system is to use thyristor switched AC-AC converters controlled dump loads. A disadvantage of the AC-AC converters is their reactive power consumption decreasing the power factor at the generator output. To avoid this problem the authors have earlier proposed two converter topologies utilizing symmetrical switching scheme resulting to zero reactive power consumption. The objective of this paper is to evaluate the frequency regulation loop performance of the dump load controlled single generator system by using the symmetrically switched converter structures. Evaluation is carried out by analyzing the performances of different converter structures in a simulator representing the operation of a Cuban µHPP “Los Gallegos”. The results showed that the frequency regulation loop performance using each proposed converter structure satisfied the Cuban standard of frequency regulation, but with the symmetrically switched structures reactive power consumption was reduced resulting to reduced losses and improved effective current delivery capacity of the generator.

A novel multigeneration system driven by a hybrid biogas-geothermal heat source, Part I: Thermodynamic modeling

Hybrid renewable energy heat sources provide more sustainable energy resources with high maintenance for high-efficient power plants. Multigeneration systems driven by a hybrid renewable source are proved as cutting-edge technologies in recent studies. In this study, a novel multigeneration system driven by a hybrid biogas-geothermal heat source is proposed and simulated. To demonstrate the feasibility of the proposed multigeneration system, first and second laws analysis are employed as the most effective tools for performance assessment of the systems. It is found that the proposed multigeneration system can produce overall heating capacity, overall cooling capacity, net output power, hydrogen production rate, and freshwater production rate of 538.1 kW, 1799 kW, 443.4 kW, 0.2583 kg/s, and 367.92 lit/h, respectively. Under this circumstance, the thermal efficiency, exergy efficiency, and total exergy destruction of the system are calculated 62.28%, 74.9%, and 2036.19 kW, respectively, showing a considerable improvement compared to the single-generation system. In addition, the results indicated that the condenser is the most destructive component, whereas the absorption refrigeration cycle is accounted as the most destructive sub-system. Moreover, a comprehensive parametric study is carried out to give more information about the behavior of the proposed system.

Development and analysis of an integrated gas turbine system with compressed air energy storage for load leveling and energy management

This paper develops and studies the performance of Compressed Air Energy Storage (CAES) system in a newly developed integrated gas turbine power plant which is considered a promising technology for energy management and load leveling. The proposed integrated system includes two sub-systems which are single effect absorption cooling system and water heater which are integrated with the intercooler and after-cooler recovering the heat rejected from the compressed air. Comprehensive energy and exergy analyses are thermodynamically performed for the system. In addition, a parametric investigation is conducted to study the effect of different key parameters on the overall system performance and component performance. The present study results show that the overall energy efficiency for the multigenerational system reaches 53% whereas the overall exergy efficiency for the system remains at 41.7%. The performance results of this multigenerational system show an increase of 11% in energy efficiency in comparison to a conventional single generation system. Moreover, the exergy efficiency of the proposed system is 6.2% higher than the conventional single generation system.

Analysis and performance assessment of a new solar-based multigeneration system integrated with ammonia fuel cell and solid oxide fuel cell-gas turbine combined cycle

In the present study, a new solar-based multigeneration system integrated with an ammonia fuel cell and solid oxide fuel cell-gas turbine combined cycle to produce electricity, hydrogen, cooling and hot water is developed for analysis and performance assessment. In this regard, thermodynamic analyses and modeling through both energy and exergy approaches are employed to assess and evaluate the overall system performance. Various parametric studies are conducted to study the effects of varying system parameters and operating conditions on the energy and exergy efficiencies. The results of this study show that the overall multigeneration system energy efficiency is obtained as 39.1% while the overall system exergy efficiency is calculated as 38.7%, respectively. The performance of this multigeneration system results in an increase of 19.3% in energy efficiency as compared to single generation system. Furthermore, the exergy efficiency of the multigeneration system is 17.8% higher than the single generation system. Moreover, both energy and exergy efficiencies of the solid oxide fuel cell-gas turbine combined cycle are determined as 68.5% and 55.9% respectively.

Analysis and evaluation of a new renewable energy based integrated system for residential applications

In this study, a solar based Rankine cycle and geothermal based system for multigeneration is designed and developed. It consists of a Rankine cycle with reheating for power generation, an absorption chiller cycle for cooling, a drying process to dry wet products, useful heat from the condenser of the Rankine cycle, and other useful heat out from heat exchangers. The overall energy and exergy efficiencies of the single generation and multigeneration systems are studied, and it is observed that the energy efficiency of the multigeneration system is higher than the single generation system. The energy efficiency of the single and multigeneration systems are 7% and 37%, respectively. Similarly, the overall exergy efficiencies for the single generation and multigeneration systems are also studied and presented in this paper. In addition to this, parametric studies are performed to observe the effects of different substantial parameters, namely inlet pressure and temperature of the turbine, and reference environment temperature in order to investigate the variations in the system performance in terms of the energy and exergy efficiencies.

Research on Shaft Subsynchronous Oscillation Characteristics of Parallel Generators and SSDC Application in Mitigating SSO of Multi-Generators

Subsynchronous oscillation (SSO) of generators caused by high voltage direct current (HVDC) systems can be solved by applying supplemental subsynchronous damping controller (SSDC). SSDC application in mitigating SSO of single-generator systems has been studied intensively. This paper focuses on SSDC application in mitigating SSO of multi-generator systems. The phase relationship of the speed signals of the generators under their common mechanical natural frequencies is a key consideration in SSDC design. The paper studies in detail the phase relationship of the speed signals of two generators in parallel under their shared mechanical natural frequency, revealing regardless of whether the two generators are identical or not, there always exists a common-mode and an anti-mode under their common natural frequency, and the phase relationship of the speed signals of the generators depends on the extent to which the anti-mode is stimulated. The paper further demonstrates that to guarantee the effectiveness of SSDC, the anti-phase mode component of its input signal should be eliminated. Based on the above analysis, the paper introduces the design process of SSDC for multi-generator systems and verifies its effectiveness through simulation in Power Systems Computer Aided Design/Electromagnetic Transients including Direct Current (PSCAD/EMTDC).

Experimental investigation of CI engine operated Micro-Trigeneration system

A Micro-Trigeneration system based on a CI engine has been designed and realized in laboratory. Experimental investigations have been carried out to evaluate the performance and emissions of the original single generation system and the Trigeneration system developed. Test results of the two generations are also compared. The test results show that the total thermal efficiency of Trigeneration reaches to 86.2% at full load where as it is only 33.7% for original single generation, at the same load. The CO2 emission from Trigeneration is 0.1211 kg CO2/kWh compared to that of 0.308 kg CO2/kWh from single generation at the engine full load. The reduction of CO2 emission in kg per unit (kWh) of useful energy output is 60.71% compared to that of single generation at full load. The experimental results show that the idea of realizing a Micro-Trigeneration suitable for a small remote home of a developing country like India is feasible and it is very effective technique to utilize the resources efficiently.

The impact of closed-loop power flow control strategies on power system stability characteristics in a single-generator system

This paper presents a theoretical study into the influence of closed-loop control of ac power flow on the small-signal and transient stability characteristics of a single-generator study system. Both the constant power and constant angle modes of power flow control are examined for a range of controller response times. The results indicate that the effect of a power flow controller on system stability is dependent on both the mode of the controller and its response time.

SWITCHING FEEDBACK CONTROL OF NON-HOLONOMIC SYSTEMS WITH MULTI-GENERATORS

In this paper, we propose a switching state feedback control algorithm for a class of non-holonomic symmetric affine systems with multi-generators. The controllability Lie algebra of a multi-generator system is structurally different from that of single-generator systems, such as conventional chained form systems. A multi-generator dynamics is partially considered a single-generator system and each subsystem can be stabilized by any existing controller proposed for chained systems. We propose a switching control algorithm, in that each generator is chosen in sequence and corresponding sub-controllers are applied, where each sub-controller is designed by existing methods for chained systems. The efficiency of the proposed strategy is evaluated via numerical simulations.

Quasi-Continuous Exponential Stabilizers for Nonholonomic Systems

In this paper, stabilizing controllers with exponential rates of convergence are proposed for different examples of nonholonomic systems. First, some examples of driftless kinematic systems, i.e. underwater vehicle and m-chains single generator systems are considered, followed by systems including drift. In particular we consider the case of mobile robots with cascade integrators.

Overvoltage detection in single and multigenerator aircraft A-C systems

OVERVOLTAGES resulting from fault conditions in aircraft a-c electric systems being designed at present can cause extensive utilization equipment damage. Until such time as aircraft power generating and regulating equipment design results in reduced overvoltage possibilities, it is likely that an overvoltage control relay will be installed in many single-generator systems.

Parallel operation of aircraft A-C generators

In military aircraft, the growth of electric power consumption has been very large. The load requirements have led to the desirability of developing a-c systems rather than producing power as direct current and then converting to meet the a-c load requirements. For the most part, single-generator systems or combinations of single-generator systems using split-bus arrangements have been used. Need for higher-reliability systems, having greater reserve capacity, and making higher utilization of generator capacity through the diversification of load equipment leads to the conclusion that parallel systems should be used in future aircraft.

Parallel operation of aircraft A-C generators

THE ELECTRIC POWER requirements for aircraft have shown an increased demand for a-c power. Repeatedly, weight studies made by airframe manufacturers have shown a saving through the generation and distribution of a-c power directly rather than the generation of d-c power and the ultimate conversion to meet the a-c power requirements. In addition, the over-all efficiency of the a-c system is higher than that of a d-c system with conversion to a-c power. For the most part, the a-c power requirements have been met through the use of single-generator systems or combinations of single-generator systems using split bus arrangements. However, the need for higher reliability systems having greater reserve capacity and making better utilization of generator capacity through the diversification of load equipment leads to the conclusion that parallel systems should be used in future aircraft. Reliable parallel operation of a-c machines requires the proper integration of many components.