Advanced biomass-based motor fuels and chemicals are becoming increasingly important to replace fossil energy sources within the coming decades. It is likely that the new biorefineries will evolve mainly from existing forest industry sites, as they already have the required biomass handling infrastructure in place. The main objective of this work is to assess the potential for increasing the profit margin from sawmill byproducts by integrating innovative downstream processes. The focus is on the techno-economic evaluation of an integrated site for biomass-based synthetic natural gas (bio-SNG) production. The option of using the syngas in a biomass-integrated gasification combined cycle (b-IGCC) for the production of electricity (instead of SNG) is also considered for comparison. The process flowsheets that are used to analyze the energy and material balances are modelled in MATLAB and Simulink. A mathematical process integration model of a typical Nordic sawmill is used to analyze the... [more]

Wind generation systems require mechanisms that allow optimal adaptation of the generator to varying wind speed and to extract maximum energy from the wind. Robust and affordable high-performance methods are also needed for isolated sites. This paper takes this approach, in which an AC switched reluctance generator is used as a generator with a variable rotor speed. Although the voltage obtained is of insufficient quality to connect the generator directly to the power grid, this kind of generator can be used in isolated sites to charge a battery bank with a simple bridge rectifier. Due to the nonlinear behavior of the machine with the position and current, along with the alternating nature of the current that circulates through its phases, the machine experiences cyclical energy transformations of a mechanical, electrical and magnetic nature. This paper analyzes these transformations for the purpose of providing guidelines for machine design and optimization as a wind turbine in isolat... [more]

For zeotropic mixtures, the temperature varies during phase change, which is opposed to the isothermal phase change of pure fluids. The use of such mixtures as working fluids in organic Rankine cycle power plants enables a minimization of the mean temperature difference of the heat exchangers, which is beneficial for cycle performance. On the other hand, larger heat transfer surface areas are typically required for evaporation and condensation when zeotropic mixtures are used as working fluids. In order to assess the feasibility of using zeotropic mixtures, it is, therefore, important to consider the additional costs of the heat exchangers. In this study, we aim at evaluating the economic feasibility of zeotropic mixtures compared to pure fluids. We carry out a multi-objective optimization of the net power output and the component costs for organic Rankine cycle power plants using low-temperature heat at 90 ∘ C to produce electrical power at around 500 kW. The primary outcomes... [more]

Axial-flow turbines represent a well-established technology for a wide variety of power generation systems. Compactness, flexibility, reliability and high efficiency have been key factors for the extensive use of axial turbines in conventional power plants and, in the last decades, in organic Rankine cycle power systems. In this two-part paper, an overall cycle model and a model of an axial turbine were combined in order to provide a comprehensive preliminary design of the organic Rankine cycle unit, taking into account both cycle and turbine optimal designs. Part A presents the preliminary turbine design model, the details of the validation and a sensitivity analysis on the main parameters, in order to minimize the number of decision variables in the subsequent turbine design optimization. Part B analyzes the application of the combined turbine and cycle designs on a selected case study, which was performed in order to show the advantages of the adopted methodology. Part A presents a... [more]

This paper explores the layout of an optimum process for supplying heat to Russian municipal heating systems operating in a market environment. We analyze and compare the standard cogeneration unit design with two-stage reheating of service water coming from controlled extraction locations and layouts that employ three in-line reheaters with heat the supply controlled by a rotary diaphragm and qualitative/quantitative methods (so-called “uncontrolled extraction”). Cogeneration unit designs are benchmarked in terms of their thermal efficiency expressed as a fuel consumption rate. The specific fuel consumption rate on electricity production is viewed as a key parameter of thermal efficiency.

In this study, two systems are brought forward to recover the waste heat of a proton exchange membrane fuel cell (PEMFC), which are named the organic Rankine cycle (ORC), and heat pump (HP) combined organic Rankine cycle (HPORC). The performances of both systems are simulated on the platform of MATLAB with R123, R245fa, R134a, water, and ethanol being selected as the working fluid, respectively. The results show that, for PEMFC where operating temperature is constantly kept at 60 °C, there exists an optimum working temperature for each fluid in ORC and HPORC. In ORC, the maximal net power can be achieved with R245fa being selected as the working fluid. The corresponding thermal efficiency of the recovery system is 4.03%. In HPORC, the maximal net power can be achieved with water being selected in HP and R123 in ORC. The thermal efficiency of the recovery system increases to 4.73%. Moreover, the possibility of using ORC as the cooling system of PEMFC is also studied. The heat released f... [more]

In power conversion of photovoltaic (PV) energy, a hard-switching buck converter always generates some disadvantages. For example, serious electromagnetic interference (EMI), high switching losses, and stresses on an active switch (metal-oxide-semiconductor-field-effect-transistor, MOSFET), and high reverse-recovery losses of a freewheeling diode result in low conversion efficiency. To release these disadvantages, a buck converter with soft-switching cells for PV panel applications is proposed. To create zero-voltage-switching (ZVS) features of the active switches, a simple active soft-switching cell with an inductor, a capacitor, and a MOSFET is incorporated into the proposed buck converter. Therefore, the switching losses and stresses of the active switches and EMI can be reduced significantly. To reduce reverse-recovery losses of a freewheeling diode, a simple passive soft-switching cell with a capacitor and two diodes is implemented. To verify the performance and the feasibility of... [more]

Wind power generation reduces our reliance on fossil fuels and can thus reduce environmental pollution. However, rapid wind power development has caused various issues related to power grid restructuring. A high proportion of the generating capacity of northeast China is based on combined heat and power (CHP), whose inflexible response to the peak regulation of power grids hinders the ability to accommodate wind power; thus, wind power curtailment is prevalent. Electric boilers can directly consume the excess wind power to supply heat during low load periods and thus mitigate the heat supply stress of CHP units. Therefore, electric boilers improve the power grid’s ability to accommodate additional wind power. From a regional power grid perspective, this paper discussed the feasibility of such a strategy for increasing the ability to accommodate wind power during the heat supply season. This paper analysed the optimum electric boiler capacity configuration of a regional power grid based... [more]

In hybrid electric vehicles with power-split configurations, the engine can be decoupled from the wheel and operated with improved fuel economy, while the entire efficiency of the powertrain is affected by the circular electric power flow. Two planetary gear (2-PG) sets with adding brakes/clutches, namely a type of four shaft elelctric continuously variable transmission (ECVT) can provide multi-mode operation for the powertrain and extend the efficient area. First, a conventional 2-PG AT (Automatic Transmission) architecture is investigated. By analyzing and comparing the connection and operating modes based on the kinematic relationship and lever analogy, a feasible four-shaft ECVT architecture with two brakes and two simplified versions are picked. To make a trade-off between fuel economy and configuration complexity, an instantaneous optimal control strategy based on the equivalent consumption minimization strategy (ECMS) concept is then developed and employed as the unified optimiz... [more]

In this paper the authors compare and contrast open and closed-cycle heat engines. First of all, by way of example and to aid discussion, the performance of proprietary externally heated closed-cycle Stirling engines is compared with that of internally heated open Otto cycle engines. Both types of engine have disadvantages and merits and this suggested that in order to accommodate the best of both engine types an externally-heated open-cycle engine might offer a more satisfactory solution for small-scale combined heat and power (CHP) systems. To investigate this possibility further the paper goes on to compare the performance of externally-heated and recuperated Joule hot-air cycle engines with that of an externally-heated closed Stirling cycle engines. The results show that an externally heated recuperated open Joule cycle engine can exceed that of a closed cycle Stirling engine operating between the same heat source and sink temperatures when a variable temperature heat source is use... [more]

Simultaneous process optimization and heat integration is essential in the optimal design and operation of process plants with high energy efficiency. This document revisits the pinch location method and updates the compact formulation for simultaneous process optimization with heat integration presented by Anantharaman et al at FOCAPD 2014.

A desiccant air-conditioning system was developed as a latent-load-processing air conditioner in a dedicated outdoor air system during the summer. This study investigated the application of this air-conditioning system to humidification during the winter without using make-up water, thereby eliminating the cause of microbial contamination in air-conditioning systems. The experiments were conducted with a system used for summer applications to determine the feasibility of adsorbing vapor from outdoor air and supplying it to an indoor space. The humidification performance, energy efficiency, and operating conditions were examined. Although the conditions were subpar because the experiments were performed with an actual dedicated outdoor air system, the results showed that it is possible to supply air with a minimum humidity ratio of 5.8 g/kg dry air (DA) when the humidity ratio of outdoor air ranges from 1.8 to 2.3 g/kg DA. The minimum humidification performance required for a dedicated... [more]

Tar formation is the main bottleneck for biomass gasification technology. A novel rotary kiln type biomass gasification process was proposed. The concept design was based on air staging and process separation. This concept was demonstrated on a pilot scale rotary kiln reactor under ambient pressure and autothermic conditions. The pilot scale gasifier was divided into three different reaction regions, which were oxidative degradation, partial oxidation and char gasification. A series of tests was conducted to investigate the effect of key parameters. The results indicate that under optimum operating conditions, a fuel gas with high heat value of about 5500 kJ/Nm³ and gas production rate of 2.32 Nm³/kg could be produced. Tar concentration in the fuel gas could be reduced to 108 mg/Nm³ (at the gasifier outlet) and 38 mg/Nm³ (after gas conditioning). The cold gas efficiency and carbon conversion rate reached 75% and 78%, respectively. The performance of this gasification system shows consi... [more]

A procedure based on MATLAB combined with ANSYS is presented and utilized for the aerodynamic and structural integrated optimization design of Horizontal-Axis Wind Turbine (HAWT) blades. Three modules are used for this purpose: an aerodynamic analysis module using the Blade Element Momentum (BEM) theory, a structural analysis module employing the Finite Element Method (FEM) and a multi-objective optimization module utilizing the non-dominated sorting genetic algorithm. The former two provide a sufficiently accurate solution of the aerodynamic and structural performances of the blade; the latter handles the design variables of the optimization problem, namely, the main geometrical shape and structural parameters of the blade, and promotes function optimization. The scope of the procedure is to achieve the best trade-off performances between the maximum Annual Energy Production (AEP) and the minimum blade mass under various design requirements. To prove the efficiency and reliability of... [more]

Waste petcoke can be converted to liquid fuels instead of stockpiling which reduces the net CO2 emission by displacing additional petroleum usage. In this study, three petcoke to liquid fuels designs were compared based on the following performance criteria: conversion efficiency, economics, and environmental impacts. The designs considered were petcoke gasification only, a combination of natural gas reforming and petcoke gasification, and natural gas reforming integrated in the petcoke gasification step. The processes were modeled and simulated using a combination of Aspen Plus v10, ProMax, and gProms software. Each of the configurations were designed to operate with and without carbon capture and sequestration (CCS) technology along with a corresponding carbon emission penalty. Performance metrics analyzed were the net present value, minimum diesel selling price, cost of CO2 avoided, and cradle to plant exit gate life cycle greenhouse gas emissions. From the analysis, the integration... [more]

We conducted a meta-study of CO2 capture processes, examining nearly 100 techno-economic analyses published in the recent open literature. Normally, it is difficult to compare one study to another because each study uses its own set of assumptions, such as plant scale, geography, market parameters, and inconsistent definitions of key metrics such as the cost of CO2 avoided (CCA). In this work, we present normalized versions of these studies using a consistent basis of comparison, such as net power delivered, base year of operation, pipeline CO2 pressure, currency, country of construction, and so on. In so doing, we are able to draw meaningful conclusions and direct comparisons between different classes of CO2 capture technology. The technologies considered include coal and gas-based processes using capture strategies including solvent-based post-combustion carbon capture, gasification-based strategies, membrane-based approaches, oxyfuel combustion, chemical looping combustion, calcium... [more]

Due to the increasing number of wind power plants, several countries have modified their grid codes to include specific requirements for the connection of this technology to the power system. One of the requirements is the ride-through fault capability (RTFC), i.e., the system capability to sustain operation during voltage sags. In this sense, the present paper intends to investigate the behavior of a full-converter wind generator with a permanent magnet synchronous machine during symmetrical and asymmetrical voltage sags. Two solutions to improve the low voltage ride-through capability (LVRT) of this technology are analyzed: discharging resistors (brake chopper) and resonant controllers (RCs). The design and limitations of these solutions and the others proposed in the literature are discussed. Experimental results in a 34 kW test bench, which represents a scaled prototype of a real 2 MW wind conversion system, are presented.

With the penetration of distributed generators (DGs), operation planning studies are essential in maintaining and operating a reliable and secure power system. Appropriate siting and sizing of DGs could lead to many positive effects forthe distribution system concerned, such as the reduced total costs associated with DGs, reduced network losses, and improved voltage profiles and enhanced power-supply reliability. In this paper, expected load interruption cost is used as the assessment of operation risk in distribution systems, which is assessed by the point estimate method (PEM). In light with the costs of system operation planning, a novel mathematical model of chance constrained programming (CCP) framework for optimal siting and sizing of DGs in distribution systems is proposed considering the uncertainties of DGs. And then, a hybrid genetic algorithm (HGA), which combines the GA with traditional optimization methods, is employed to solve the proposed CCP model. Finally,the feasibili... [more]

Biodiesel, or alkyl ester, is an alternative renewable, biodegradable, and non-toxic diesel fuel produced by the catalytic transesterification of vegetable oil. Here we characterize a system for continuous transesterification of vegetable oil using five continuous stirring tank reactors (5CSTRs). We tested residence times of 16⁻43min, stirring speeds of 200⁻800rpm, a catalyst concentration (KOH) of 0.25⁻1 wt% of oil (in gram), different total flow rates of the oil and MeOH, and on the production performance of the 5 stage continuous reactor for transesterification of vegetable oil. Using a molar ratio of oil:methanol of 1:7 and a reaction temperature of 65 °C, we show that a high stirring speed increased the reaction rate, but an excessive stir speed decreased the reaction rate and conversion to biodiesel. Furthermore, a higher catalyst percentage significantly increased the reaction rate and production capacity. A catalyst percentage of 1 wt% of oil gave the best conversion; 99.04 ± 0... [more]

In single-chamber solid oxide fuel cells (SC-SOFCs), both anode and cathode are situated in a common gas chamber and are exposed to a mixture of fuel and oxidant. The working principle is based on the difference in catalytic activity of the electrodes for the respective anodic and cathodic reactions. The resulting difference in oxygen partial pressure between the electrodes leads to the generation of an open circuit voltage. Progress in SC-SOFC technology has enabled the generation of power outputs comparable to those of conventional SOFCs. This paper provides a detailed review of the development of SC-SOFC technology.

The permanent magnet (PM) spherical motor has been subject to growing interest from the scientific community due to its potential for applications in distinct areas, particularly in robotics, prosthetics, satellite control, sensors or camera systems. Motivated by this movement, the current work presents all the steps for the efficient design and construction of a spherical motor model, using compound deposition technology with the aid of a 3D printer. Furthermore, we report comprehensive studies on the accuracy of the positioning system of the proposed motor using only three stator coils, which jointly act to move the rotor axis toward any point in the hemisphere. Unmodeled nonlinear phenomena, such as friction, impair accurate positioning of the motor actuator, but this is solved by means of a visual servo control system, which allows the user to collect input⁻output data to train an artificial neural network model. Details on the construction of the proposed motor are reported, in ad... [more]

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The Free-piston linear generator (FPLG) is a novel energy converter which can generate electrical energy and is regarded as a potential technology for solving the restriction of the short driving range of electric vehicles. Getting rid of the crank and flywheel mechanism, FPLG obtains some advantages of a variable compression ratio, compact size, and highly-efficient power generation. Linear electric machine (LEM) design and piston motion control are two key technologies of FPLG. However, they are currently the main obstacles to the favorable performance of FPLG. LEM being used to drive the piston motion or generate electric energy is an integrated design including a motor/generator. Various types of LEMs are investigated, and suitable application scenarios based on advantages and disadvantages are discussed. The FPLG’s controller is used to ensure stable operation and highly-efficient output. However, cycle-to-cycle variations of the combustion process and motor/generator switching ma... [more]

Wind power is the world’s fastest-growing energy source. More power can be generated from wind energy through the use of new wind machine designs and techniques. The objective of the present work is to encourage people and governments to develop wind energy-based power plants to achieve sustainable energy infrastructures, especially in developing countries. In this paper, a feasibility study of a 100 MW grid-connected wind farm is conducted for five different cities of Saudi Arabia (KSA). The results indicate that the proposed power plant is feasible both technically and economically. All sites are found to be within the profitable range with Dhahran being the most feasible site among the others for the installation of the wind farm. A sensitivity analysis has also been carried out to find out the effects of different incentives on the payback period of the project.

The double-stator permanent-magnet doubly salient (DS-PMDS) machine is an interesting candidate motor for electric vehicle (EV) applications because of its high torque output and flexible working modes. Due to the complexity of the motor structure, optimization of the DS-PMDS for EVs requires more research efforts to meet multiple specifications. Effective multi-objective optimization to increase torque output, reduce torque ripple, and improve PM material utilization and motor efficiency is implemented in this paper. In the design process, a multi-objective comprehensive function is established. By using parametric sensitivity analysis (PSA) and the sequential quadratic programming (NLPQL) method, the influence extent of each size parameter for different performance is effectively evaluated and optimal results are determined. By adopting the finite element method (FEM), the electromagnetic performances of the optimal DS-PMDS motor is investigated. Moreover, a multi-physical field anal... [more]