Multi-objective particle swarm optimization of flat plate solar collector using constructal theory

In this study, the design and thermo-economic assessment of a flat plate solar collector has been explored by considering two scenarios. A conventional flat plate collector (FPC) is selected as the first scenario and multi-objective particle swarm optimization (MOPSO) algorithm has been applied to improve the thermal efficiency and total annual cost (TAC) simultaneously. In the second scenario, the constructal concept is implemented for the FPC by considering the same range of variations for the selected decision variables in the conventional FPC. Six design parameters including the system specifications are selected for the conventional FPC and for the constructal FPC in which is analyzed in two parts, hence twelve design parameters are selected for its optimization. The Pareto optimal front is obtained and compared for these two scenarios. In the thermal efficiencies higher than 0.54, the constructal Pareto optimal front is dominated over the results related to the conventional FPC

An overview of renewable hydrogen production from thermochemical process of oil palm solid waste in Malaysia

Hydrogen is one of the most promising energy carriers for the future of the world due to its tremendous capability of pollution reduction. Hydrogen utilization is free of toxic gases formation as well as carbon dioxide (CO2) emission. Hydrogen production can be implemented using a wide variety of resources including fossil fuels, nuclear energy and renewable and sustainable energy (RSE). Amongst various RSE resources, biomass has great capacity to be employed for renewable hydrogen production. Hydrogen production from palm solid residue (PSR) via thermochemical process is a perfect candidate for waste-to-well strategy in palm oil mills in Malaysia. In this paper, various characteristics of hydrogen production from thermochemical process of PSR includes pyrolysis and gasification are reviewed. The annual oil palm fruits production in Malaysia is approximately 100 million tonnes which the solid waste of the fruits is capable to generate around 1.05 × 1010 kgH2 (1.26 EJ) via supercritical water gasification (SCWG) process. The ratio of energy output to energy input of SCWG process of PSR is about 6.56 which demonstrates the priority of SCWG to transform the energy of PSR into a high energy end product. The high moisture of PSR which is the most important barrier for its direct combustion, emerges as an advantage in thermochemical reactions and highly moisturized PSR (even more than 50%) is utilized directly in SCWG without application of any high cost drying process. Implementation of appropriate strategies could lead Malaysia to supply about 40% of its annual energy demand by hydrogen yield from SCWG of PSR. ©2015 Elsevier Ltd. All rights reserved

Effects of duct burner on bottoming cycle in a combined cycle power plant

In this study, thermodynamic modeling and exergoeconomic assessment of a Combined Cycle Power Plant (CCPP) with a Duct Burner (DB) was performed. Obtaining an optimum condition for the performance of a CCPP, using a DB after gas turbine was investigated by various researchers. DB is installed between gas turbine cycle and Rankine cycle of a CCPP to connect the gas turbine outlet to the Heat Recovery Steam Generator (HRSG) in order to produce steam for bottoming cycle. To find the irreversibility effect in each component of the bottoming cycle, a comprehensive parametric study is performed. In this regard, the effect of DB fuel flow rate on cost efficiency and economic of the bottoming cycle are investigated. To obtain a reasonable result, all the design parameters are kept constant while the DB fuel flow rate is varied. The results indicate that by increasing DB fuel flow rate, the investment cost and the efficiency of CCPP are increased. T-S diagram reveals that by using a DB, higher pressures steam in heat recovery steam generator has higher temperature while the low pressure is decreased. In addition, the exergy of flow gases in heat recovery steam generator increases. So, the exergy efficiency of the whole cycle was increased to around 6 percent, while the cost of the plant reduced by one percent

Genetic algorithm for optimization of energy systems: Solution uniqueness, accuracy, Pareto convergence and dimension reduction

Genetic algorithm (GA) is widely accepted in energy systems optimization especially multi objective method. In multi objective method, a set of solutions called Pareto front is obtained. Due to random nature of GA, finding a unique and reproducible result is not an easy task for multi objective problems. Here we discuss the solution uniqueness, accuracy, Pareto convergence, dimension reduction topics and provide quantitative methodologies for the mentioned parameters. Firstly, Pareto frontier goodness and solution accuracy is introduced. Then the convergence of Pareto front is discussed and the related methodology is developed. By comparing two different best points (optimum points) selection method, it is shown that multi objective methods can be reduced to single objective or lower dimensions in objective functions by using ratio method. Our results establish that our proposed method can indeed provide unique solution of satisfactory accuracy and convergence for a multi-objective optimization problem in energy systems

Modelling and exergoeconomic-environmental analysis of combined cycle power generation system using flameless burner for steam generation

To have an optimum condition for the performance of a combined cycle power generation, using supplementary firing system after gas turbine was investigated by various researchers. Since the temperature of turbine exhaust is higher than auto-ignition temperature of the fuel in optimum condition, using flameless burner is modelled in this paper. Flameless burner is installed between gas turbine cycle and Rankine cycle of a combined cycle power plant which one end is connected to the outlet of gas turbine (as primary combustion oxidizer) and the other end opened to the heat recovery steam generator. Then, the exergoeconomic-environmental analysis of the proposed model is evaluated. Results demonstrate that efficiency of the combined cycle power plant increases about 6% and CO2emission reduces up to 5.63% in this proposed model. It is found that the variation in the cost is less than 1% due to the fact that a cost constraint is implemented to be equal or lower than the design point cost. Moreover, exergy of flow gases increases in all points except in heat recovery steam generator. Hence, available exergy for work production in both gas cycle and steam cycle will increase in new model

Thermodynamic assessment of integrated biogas-based micro-power generation system

In this paper, a thermodynamic modelling of an integrated biogas (60%CH4 + 40%CO2) micro-power generation system for electricity generation is reported. This system involves a gas turbine cycle and organic Rankine cycle (ORC) where the wasted heat of gas turbine cycle is recovered by closed ORC. The net output power of the micro-power generation system is fixed at 1.4 MW includes 1 MW power generated by GT and 0.4 MW by ORC. Energy and exergy assessments and related parametric studies are carried out, and parameters that influence on energy and exergy efficiency are evaluated. The performance of the system with respect to variation of design parameters such as combustion air inlet temperature, turbine inlet temperature, compressor pressure ratio, gas turbine isentropic efficiency and compressor isentropic efficiency (from the top cycle) and steam turbine inlet pressure, and condenser pressure (from bottoming cycle) is evaluated. The results reveal that by the increase of gas turbine isentropic efficiency, the outlet temperature of gas turbine decreases which incurs negative impacts on the performance of air preheater and heat exchanger, however the energy and exergy efficiency increases in the whole system. By the increase of air compressor pressure ratio, the energy and exergy of the combined cycle decreases. The exergy efficiency of ORC alters by the variation of gas turbine parameters which can be attributed to the variation of temperature discrepancy between gas turbine exhaust temperature and ORC working fluid. Both first and second law efficiency of the combined cycle increases with the enhancement of inlet pressure of ORC turbine due to the mitigation of exergy destruction in heat exchanger. The rate of power generation in ORC increases by the enhancement of ORC turbine inlet pressure, however overall exergy destruction of the cycle decreases slightly

On the optimization of energy systems: Results utilization in the design process

This paper proposes a new methodology to provide a flexible optimum design tool for the multi-objective optimization of energy systems. There are many articles published on the optimization of energy systems, which use a multi-objective evolutionary algorithm for different cases. However a general method for optimization results utilization in design process is not presented to the authors’ knowledge and usually equilibrium point concept is used to select the optimal solution. Here a new method is proposed to improve the optimization results utilization in the design process. This method is applied on a simple energy system to consider the correlations between the design parameter and objective functions. The proposed method is flexible and easy to implement in any design problem. Results provide a neat process of optimum design includes cost limited maximum efficiency and components parameters selection like the condenser pressure and sub cool and superheat degrees. Results also show that compressor efficiency is the most powerful parameter in the case, which has the most significance effects on the optimization results