Stand-alone Power Generation Research Articles

4-1-1 簡易なモデルを用いた小規模独立風力発電システムの負荷の最適化に関する検討

4-1-1 簡易なモデルを用いた小規模独立風力発電システムの負荷の最適化に関する検討

ELatrine: Lessons Learned from the Development of a Low-Tech MFC Based on Cardboard Electrodes for the Treatment of Human Feces

The aim of the study was to provide experimental proof-of-concept that stand-alone power generation based on microbial fuel cells (MFCs) operated using human feces as the substrate can be achieved. A pit latrine that is typically employed for decentralized treatment of human feces e.g. in regions without access to centralized wastewater infrastructures was installed as sampling site. It was the philosophy that the components, i.e. anodes and cathodes, used in the MFCs had to be based on low-cost precursors. This was achieved by recycling common household materials or waste products and a low-tech/cost production method was developed to convert them into usable electrodes. It is demonstrated that i) pre-tests on using an equivalent to vent-air from ovens or fire-places allowed a low-tech carbonization of e.g. corrugated cardboard to electrode materials; ii) that anodes based on corrugated cardboard can be operated using real human feces as substrate, nevertheless, providing only low current densities (15.09 ± 5.18 μA cm−2) and iii) cathodes – with nitrogen functionalities derived from (artificial) urine – based on corrugated cardboard or as an alternative jeans cloth show a good oxygen reduction reaction (ORR) activity. Introducing nitrogen containing surface moieties to the cathode surface increased the ORR up to factor 5 (chronoamperometry at 0 V vs. Ag/AgCl sat. KCl) compared to the untreated reference. Most importantly, highly valuable lessons for exploiting real and highly heterogeneous and dense substrates like human feces in microbial electrochemical technologies were learned.

Techno-economic feasibility of photovoltaic, wind, diesel and hybrid electrification systems for off-grid rural electrification in Colombia

Electrification to rural and remote areas with limited or no access to grid connection is one of the most challenging issues in developing countries like Colombia. Due to the recent concerns about the global climatic change and diminishing fuel prices, searching for reliable, environmental friendly and renewable energy sources to satisfy the rising electrical energy demand has become vital. This study aims at analyzing the application of photovoltaic (PV) panels, wind turbines and diesel generators in a stand-alone hybrid power generation system for rural electrification in three off-grid villages in Colombia with different climatic characteristics. The areas have been selected according to the “Colombia’s development plan 2011–2030 for non-conventional sources of energy”. First, different combinations of wind turbine, PV, and diesel generator are modeled and optimized to determine the most energy-efficient and cost-effective configuration for each location. HOMER software has been used to perform a techno-economic feasibility of the proposed hybrid systems, taking into account net present cost, initial capital cost, and cost of energy as economic indicators.

Performance Analysis of a VPV/FC Hybrid System for Generating Electricity in Iraq's Remote Areas

A reliable electrical energy supply is a prerequisite for improving the standard economic and quality of life levels in a country. As is the case in many countries, Iraq is home to a collection of remote villages. Since it is uneconomical to connect these villages to the existing grid, the installation of stand- alone electrical power generators has become common practice. As a result, diesel stand-alone power generators see widespread use in these remote locales, which, whilst fit for their intended purpose, unfortunately suffer from several drawbacks, including instability in regards to everyday oil prices and a number of environmental issues. The implementation of a PV/FC hybrid power system could be one potential alternative to help solve these problems. Therefore, this paper will present PV/FC system control strategies alongside information relating to the performance of such system components, based on a case study that was conducted in Al-Gowair, Iraq. This study is especially important in terms of envisioning the future energy supply needs of Iraq. The HOMER simulation results showed that by using the proposed control strategies and suggested components of a PV/FC system, it was able to produce a satisfactory outcome.

Integrated DC ‑ AC Converter as Power Conditioner for Fuel Cell Based System

This paper presents a new integrated power conditioner topology for power supply systems based on fuel cells. The proposed converter is based in the ZVS active clamp full bridge boost converter but controlled with sinusoidal pulse width modulation technique. The proposed fuel cell power conditioner is intended for stand-alone ac power generation and low voltage fuel cell input. The main characteristic of the proposed topology is the use of fewer components when compared to the conventional two-stage power conditioners approach, so the cost is lower. In addition, the total efficiency is increased by reducing the power processing stages. Therefore, it is expected that the proposed integrated power conditioner topology could be effectively utilized for fuel cells applications. The paper presents a compressive analysis of the main characteristics of the fuel cell which will determine the design parameters for the power conditioner. Also, detailed operations of the integrated topology is introduced. In order to validate the proposed approach a 900 watts prototype was implemented. The paper presents experimental results under several operating conditions.

High Resolution Trichromatic Road Surface Scanning with a Line Scan Camera and Light Emitting Diode Lighting for Road-Kill Detection.

This paper presents a road surface scanning system that operates with a trichromatic line scan camera with light emitting diode (LED) lighting achieving road surface resolution under a millimeter. It was part of a project named Roadkills—Intelligent systems for surveying mortality of amphibians in Portuguese roads, sponsored by the Portuguese Science and Technology Foundation. A trailer was developed in order to accommodate the complete system with standalone power generation, computer image capture and recording, controlled lighting to operate day or night without disturbance, incremental encoder with 5000 pulses per revolution attached to one of the trailer wheels, under a meter Global Positioning System (GPS) localization, easy to utilize with any vehicle with a trailer towing system and focused on a complete low cost solution. The paper describes the system architecture of the developed prototype, its calibration procedure, the performed experimentation and some obtained results, along with a discussion and comparison with existing systems. Sustained operating trailer speeds of up to 30 km/h are achievable without loss of quality at 4096 pixels’ image width (1 m width of road surface) with 250 µm/pixel resolution. Higher scanning speeds can be achieved by lowering the image resolution (120 km/h with 1 mm/pixel). Computer vision algorithms are under development to operate on the captured images in order to automatically detect road-kills of amphibians.

(Science for Solving Society’s Problems Challenge Grant Winner) eLatrines: Development of a Fully Cardboard based Microbial Fuel Cell for Pit Latrines

The aim of the project was to provide full experimental proof-of-concept that stand-alone power generation based on microbial fuel cells (MFCs) operated on human feces from pit latrines as substrate can be achieved. Thereby, the establishment of these eLatrines was based on MFC-technology and the components were to be gained from low-cost materials and through low-tech approaches. For the latter the system was to be developed so as to utilize as many components as possible that can be produced by non-trained persons in decentralized areas for example in developing countries, e.g. the cardboard based electrodes. This presentation summarizes achievements and the lessons learned for i) electrodes gained from corrugated cardboard to be used as anodes and cathodes; ii) anodes being operated using real human feces as substrate; iii) cathodes – with nitrogen functionalities derived from (artificial) urine and based on corrugated cardboard - for oxygen reduction reaction activity; iv) pre-tests on using vent-air from ovens/ fireplaces for allowing low-tech carbonization of corrugated cardboard, v) the operation of the described components in a combined approach under potentiostatic control as well as in fuel cell mode. In summary, we will show that the overall concept of a stand-alone power generation from human feces in urine can become technically feasible as well as economically and societal relevant. However, the achieved current densities of less than 100 µA/ cm2 (geometric surface area) as well as challenges due to the operation with real, highly inhomogeneous substrates like clogging of electrodes’ pores, formation of insulating fat layers at cathodes, etc. highlight the need for a thorough process engineering.

Performance evaluation of self-excited DSIG as a stand-alone distributed energy resources

Multi-phase induction generators which may be operated in grid or self-excited mode, are found to be successful machines for wind energy conversion. Out of these two, self-excited mode is gaining importance due to its ability to convert the wind energy into electrical energy for large variations in operating speed. For this purpose, in this paper modelling and analysis in an isolated self-excited mode of dual-stator induction generator (DSIG) with a new algorithm have been done. We develop the steady-state model of a DSIG, for stand-alone renewable generation dispenses with the segregating of real and imaginary components of the complex impedance of the induction generator. Steady-state performances and characteristics of different configurations are clearly examined and compared. Simulated results as found using proposed “FZERO” algorithm are verified using experimental results on a test machine. Results obtained show that the system has sufficient capability for practical use in stand-alone power generation.

Economic and policy evaluation of SPCC (solar-assisted post-combustion carbon capture) in Australia

This paper evaluates the economic feasibility of SPCC (solar-assisted post-combustion carbon capture) at a coal power plant near Sydney, Townsville and Melbourne for implementation in 2020. A review of Australia's carbon and renewable energy policy is performed first, after which the merits of application of each incentive for SPCC are compared. Incentives such as subsidies, preferential discount rate, carbon tax and RECs (renewable energy certificates) are evaluated. No single incentive on its own, and within reasonable limits, is able to provide a favourable economic performance for power plant based renewable powered CCS (carbon capture and storage). However, once the compounded effect of carbon tax and electricity price increase is taken into account, a carbon price as low as A$ 25/tonne-CO2 and a REC price as low as A$ 35/MWhe is able to produce a positive net benefit in Townsville, while a slightly higher carbon price and REC price is required for Sydney. Melbourne performs poorest amongst the three locations, where substantially higher incentives would be needed for economic feasibility. The level of incentives required for SPCC to become feasible are found to fall in the range of current Australian policy incentives accessible to renewable energy technologies for stand-alone power generation.

An optimized Fuzzy Logic Controller by Water Cycle Algorithm for power management of Stand-alone Hybrid Green Power generation

This paper aims to improve the power management system of a Stand-alone Hybrid Green Power generation based on the Fuzzy Logic Controller optimized by the Water Cycle Algorithm. The proposed Stand-alone Hybrid Green Power consists of wind energy conversion and photovoltaic systems as primary power sources and a battery, fuel cell, and Electrolyzer as energy storage systems. Hydrogen is produced from surplus power generated by the wind energy conversion and photovoltaic systems of Stand-alone Hybrid Green Power and stored in the hydrogen storage tank for fuel cell later using when the power generated by primary sources is lower than load demand. The proposed optimized Fuzzy Logic Controller based power management system determines the power that is generated by fuel cell or use by Electrolyzer. In a hybrid system, operation and maintenance cost and reliability of the system are the important issues that should be considered in studies. In this regard, Water Cycle Algorithm is used to optimize membership functions in order to simultaneously minimize the Loss of Power Supply Probability and operation and maintenance. The results are compared with the particle swarm optimization and the un-optimized Fuzzy Logic Controller power management system to prove that the proposed method is robust and effective. Reduction in Loss of Power Supply Probability and operation and maintenance, are the most advantages of the proposed method. Moreover the level of the State of Charge of the battery in the proposed method is higher than other mentioned methods which leads to increase battery lifetime.

Bifurcation Analysis and Experimental Study of a Multi-Operating-Mode Photovoltaic-Battery Hybrid Power System

Stand-alone hybrid renewable power generation systems have gained popularity in recent years. However, due to the intermittent nature of the renewable resources, hybrid renewable power generation systems are often designed to operate with multiple structures and multiple operating modes. The design for stable operation of such systems requires consideration of the stability conditions for all possible structures and operating modes. A stand-alone photovoltaic-battery hybrid power system is studied for illustrating the possible complex behavior in this paper. We reveal smooth bifurcation, including slow-scale Neimark–Sacker bifurcation, fast-scale period-doubling bifurcation as well as coexisting bifurcation. Under certain conditions, when the system switches its operating mode, a nonsmooth bifurcation, manifested as a jump between stable and unstable behavior, can also be observed. Moreover, a detailed analysis based on a discrete-time mapping model is performed to evaluate the stability boundaries of the system. Extensive experiments verify the analysis and simulated results.

Research of Voltage Amplitude Fluctuation and Compensation for Wound Rotor Brushless Doubly-Fed Machine

This paper presents an unexpected fluctuation of voltage for a 30-kW wound rotor brushless doubly-fed machine (BDFM) in a standalone power generation system. To address this issue, an improved method of harmonic injection is introduced. A voltage and current double closed-loop control strategy, based on control winding (CW) current decoupling, is applied through the entire experiment. Consequently, the experimental outcomes are fairly aligned with the dynamic simulations in most conditions. However, the voltage fluctuation in the power winding (PW) can be observed for a certain speed range. Harmonic analysis is then carried out on experimental data of PW voltage and CW current. A pair of interharmonic waves, which are symmetric with respect to the fundamental wave, is demonstrated to exist in PW voltage and CW current. Due to the analysis, these harmonic conjugate waves are caused by the high-order magnetomotive force tooth harmonics and current harmonics within a specific speed range. Accordingly, the control strategy of harmonic injection is employed to effectively eliminate these harmonic conjugate waves. The experimental results further highlight that the voltage amplitude can be maintained with less harmonic contents by our tailored control scheme. In addition, the formation and presence of harmonic conjugate waves may lead to the voltage amplitude fluctuation of BDFM in the standalone power generation system.

Standalone Portable SOFC Power Generator for Autonomous Operation

Since 2002 AVL is working on fuel cells with the focus on mobile and stationary SOFC systems. In 2014 the first completely standalone mobile SOFC power generator fueled with diesel was demonstrated. The system is equipped with all required additional components for autonomous operation like a battery pack and power electronics. During startup, the internal auxiliaries (e.g. the air blower), are consuming energy from the battery pack to heat the stack up to operating temperature. At a certain point the SOFC system starts to produce electricity which is used to recharge the batteries. An external consumer can draw a power of up to 5kW from the system. Short term power peaks (positive or negative) are buffered by a super cap. The operation is automatically controlled by the control unit implementing an energy management system. This enables a very user-friendly operation where the control system takes care of an always sufficient state-of-charge level of the battery pack. The presentation will also give a general status report and outlook of the AVL APU power generator development program.

Standalone Portable SOFC Power Generator for Autonomous Operation

Since 2002 AVL is working on fuel cells with the focus on mobile and stationary SOFC systems. In 2014 the first completely standalone mobile SOFC power generator fueled with diesel was demonstrated. The system is equipped with all required additional components for autonomous operation like a battery pack and power electronics. During startup, the internal auxiliaries (e.g. the air blower), are consuming energy from the battery pack to heat the stack up to operating temperature. At a certain point the SOFC system starts to produce electricity which is used to recharge the batteries. An external consumer can draw a power of up to 5kW from the system. Short term power peaks (positive or negative) are buffered by a super cap. The operation is automatically controlled by the control unit implementing an energy management system. This enables a very user-friendly operation where the control system takes care of an always sufficient state-of-charge level of the battery pack.

Process analysis of pressurized oxy-coal power cycle for carbon capture application integrated with liquid air power generation and binary cycle engines

In this paper, the thermodynamic advantage of integrating liquid air power generation (LAPG) process and binary cycle waste heat recovery technology to a standalone pressurized oxy-coal combustion supercritical steam power generation cycle is investigated through modeling and simulation using Aspen Plus® simulation software version 8.4. The study shows that the integration of LAPG process and the use of binary cycle heat engine which convert waste heat from compressor exhaust to electricity, in a standalone pressurized oxy-coal combustion supercritical steam power generation cycle improves the thermodynamic efficiency of the pressurized oxy-coal process. The analysis indicates that such integration can give about 12–15% increase in thermodynamic efficiency when compared with a standalone pressurized oxy-coal process with or without CO2 capture. It was also found that in a pressurized oxy-coal process, it is better to pump the liquid oxygen from the cryogenic ASU to a very high pressure prior to vapourization in the cryogenic ASU main heat exchanger and subsequently expand the gaseous oxygen to the required combustor pressure than either compressing the atmospheric gaseous oxygen produced from the cryogenic ASU directly to the combustor pressure or pumping the liquid oxygen to the combustor pressure prior to vapourization in the cryogenic ASU main heat exchanger. The power generated from the compressor heat in the flue gas purification, carbon capture and compression unit using binary cycle heat engine was also found to offset about 65% of the power consumed in the flue gas cleaning and compression process. The work presented here shows that there is a synergistic and thermodynamic advantage of utilizing the nitrogen-rich stream from the cryogenic ASU of an oxy-fuel power generation process for power generation instead of discarding it as a waste stream.

Generating Electricity using PV/FC Hybrid System

A reliable electrical energy supply is a prerequisitefor improving the standard economic and quality of life levels in acountry. As is the case in many countries, it is uneconomical toconnect these villages to the existing grid, the installation of standaloneelectrical power generators has become common practice. Asa result, diesel stand-alone power generators see widespread use inthese remote locales, which, whilst fit for their intended purpose,unfortunately suffer from several drawbacks, including instabilityin regards to everyday oil prices and a number of environmentalissues. The implementation of a PV/FC hybrid power system couldbe one potential alternative to help solve these problems. Therefore,this paper presents PV/FC system control strategies. This study isespecially important in terms of envisioning the future energysupply needs. By using HOMER the proposed control strategiesand suggested components of a PV/FC system would be able toproduce a satisfactory outcome.

A numerical analysis of unsteady inflow wind for site specific vertical axis wind turbine: A case study for Marsabit and Garissa in Kenya

Most of the wind analysis studies have been conducted under steady wind conditions. The study of real unsteady wind environment, however, is still an open-ended research question. This is attributable to the existing aerodynamic complexities under such conditions. In this paper, therefore, a numerical approach to investigate wind energy potential under unsteady conditions was proposed. In carrying out the study, the wind characteristics for two rural-urban towns in Kenya, namely Marsabit (2°19′N, 37°58′E) and Garissa (0°28′S,39°38′E), were selected. A CFD analysis method was used to evaluate both unsteady wind inflow performance and the flow physics that affects the performance on a Vertical Axis Wind Turbine (VAWT). Using the validated CFD model, unsteady wind simulations were performed and the results obtained compared with empirical methods. Compared to the prevailing methods, the proposed numerical approach is not only computationally inexpensive, but also robust in both steady and unsteady wind conditions. The numerical method demonstrates that Garissa station is unsuitable for grid-connected power generation, while Marsabit station is suitable for both grid-connected and stand-alone power generation activities. The study results will hopefully be of importance to the wind industries that require designs for wind turbines reflecting real unsteady wind environment.

Wind-driven stand-alone six-phase self-excited induction generator transients under different loading conditions

This paper present the transient performance of an isolated six-phase self-excited induction generator (SPSEIG) driven by a fixed-pitch wind turbine. The approach is based on a wind-turbine model, SPSEIG model and detailed transient behaviour of an SPSEIG for stand-alone power generation, when subjected to sudden switching of balanced/unbalanced R, RL and RLC load for both three-phase winding sets. The computer model has been developed in an arbitrary reference frame. In the d–q axis model, the effects of common mutual leakage inductance between the two three-phase winding sets have been included. The simulation results show a good performance from the system under different loading conditions. While the interaction between the two windings is inevitable and variation of load at one winding set changes the operating conditions at the other winding, the situation is still satisfactory for a wide range of rural resistive loads.

Optimal load sharing strategy for a wind/diesel/battery hybrid power system based on imperialist competitive neural network algorithm

In this study, optimal load sharing strategy for a stand-alone hybrid power generation system that consists of wind turbine, diesel generator and battery banks is presented. The diesel generator is used to complement the intermittent output of the wind source whereas the battery is used to compensate for part of the temporary peak demand, which the wind and diesel generator cannot meet thus avoiding oversizing of the diesel generator. To optimise the performance of the system, imperialist competitive algorithm (ICA), ant colony optimisation (ACO) and particle swarm optimisation (PSO) are used to optimal load sharing. These algorithms are used to select the best available energy source so that the system has the best performance.To verify the system performance simulation studies have been carried out using forecasted data (load demand and wind speed). Accordingly, ICA, ACO and PSO are used to train a three-layer feed forward neural network. This trained artificial neural network is applied to short-term wind speed and load demand forecasting on a specific day in the Qazvin. The results show that the proposed control methods can reduce fuel consumption and increase the battery lifetime and battery ability to respond to real-time load turbulences simultaneously.

Stand‐alone excitation synchronous wind power generators with power flow management strategy

This study presents a stand-alone excitation synchronous wind power generator (SESWPG) with power flow management strategy (PFMS). The rotor speed of the excitation synchronous generator tracks the utility grid frequency by using servo motor tracking technologies. The automatic voltage regulator governs the exciting current of generator to achieve the control goals of stable voltage. When wind power is less than the needs of the consumptive loading, the proposed PFMS increases motor torque to provide a positive power output for the loads, while keeping the generator speed constant. Conversely, during the periods of wind power greater than output loads, the redundant power of generator production is charged to the battery pack and the motor speed remains constant with very low power consumption. The advantage of the proposed SESWPG is that the generator can directly output stable alternating current (AC) electricity without using additional DC–AC converters. The operation principles with software simulation for the system are described in detail. Experimental results of a laboratory prototype are shown to verify the feasibility of the system.