Low Power Generation Research Articles

Two-Switch Boost Converter With Improved Voltage Gain and Degree of Freedom of Control

The use of renewable resources for low power generation has led to extensive research on power converters for reliable and efficient power conversion. Though conventional boost converter (CBC) remains the widely used topology, its operating range is limited due to constraints on voltage gain and degree of freedom of control (DoFoC). This paper presents a two-switch boost converter (TSBC) which improves the voltage gain and DoFoC by cascading an additional switch-diode pair to the CBC circuit. The additional switch enhances the range of voltage gain without operating CBC at high duty ratios. Additionally, TSBC offers more choices to adjust voltage gain, which enhances DoFoC. The switching interval selection is detailed considering the voltage gain and constraints on circuit variables. The design formulations of TSBC are examined to facilitate optimal choice of components. The features of TSBC are theoretically established with mathematical derivations and are validated by simulations and experiments. The experimental results indicate that for a duty ratio of 0.7 for the existing switch of CBC, an increase in voltage gain from 3.2 to 4.3 is achieved when the duty ratio of the additional switch in TSBC is varied from 0 to 0.1. Similarly, improved DoFoC is demonstrated with inductor current control as well as with constant ripple ratios while maintaining the required output voltage. The proposed converter can easily replace the commonly CBC to improve the gain and DoFoC by simply cascading a switch-diode pair at the input-side of CBC.

Command Value Determination Considering Generation Cost and Control Performance Using Model Predictive Control in Load Frequency Control

This paper deals with load frequency control (LFC) problem for power system. The control is conducted to retain power demand supply balance by controlling output of generators in power network. In order to realize LFC with low power generation cost while maintaining control performance, this paper proposes frequency control method using Moving Horizon Estimation (MHE) and Model Predictive Control (MPC). First, MHE is used to estimate the state of the system. Next, optimization calculation is performed using MPC to determine the command values for each generator. Finally, simulation of load frequency control is carried out to verify the effectiveness of the proposed method.

Design and Analysis of an Offshore Wind Power to Ammonia Production System in Nova Scotia

Green ammonia has potential as a zero-emissions energy vector in applications such as energy storage, transmission and distribution, and zero-emissions transportation. Renewable energy such as offshore wind energy has been proposed to power its production. This paper designed and analyzed an on-land small-scale power-to-ammonia (P2A) production system with a target nominal output of 15 tonnes of ammonia per day, which will use an 8 MW offshore turbine system off the coast of Nova Scotia, Canada as the main power source. The P2A system consists of a reverse osmosis system, a proton exchange membrane (PEM) electrolyser, a hydrogen storage tank, a nitrogen generator, a set of compressors and heat exchangers, an autothermal Haber-Bosch reactor, and an ammonia storage tank. The system uses an electrical grid as a back-up for when the wind energy is insufficient as the process assumes a steady state. Two scenarios were analyzed with Scenario 1 producing a steady state of 15 tonnes of ammonia per day, and Scenario 2 being one that switched production rates whenever wind speeds were low to 55% the nominal capacity. The results show that the grid connected P2A system has significant emissions for both scenarios, which is larger than the traditional fossil-fuel based ammonia production, when using the grid in provinces like Nova Scotia, even if it is just a back-up during low wind power generation. The levelized cost of ammonia (LCOA) was calculated to be at least 2323 CAD tonne−1 for both scenarios which is not cost competitive in this small production scale. Scaling up the whole system, reducing the reliance on the electricity grid, increasing service life, and decreasing windfarm costs could reduce the LCOA and make this P2A process more cost competitive.

Dynamic Process Modeling of Topside Systems for Evaluating Power Consumption and Possibilities of Using Wind Power

Norwegian offshore wind farms may be able to supply power to offshore oil and gas platforms in the near future thanks to the expeditious development of offshore wind technology. This would result in a reduction in CO2 emissions from oil and gas offshore installations, which are currently powered predominantly by gas turbines. The challenge with using wind power is that offshore oil and gas installations require a fairly constant and stable source of power, whereas wind power typically exhibits significant fluctuations over time. The purpose of this study is to perform a technical feasibility evaluation of using wind power to supply an offshore oil and gas installation on the basis of dynamic process simulations. Throughout the study, only the topside processing system is considered, since it is the most energy-intensive part of an oil and gas facility. An offshore field on the Norwegian Continental Shelf is used as a case study. The results indicate that, when the processing system operates in steady-state conditions, it cannot be powered solely by wind energy, and another power source is required to compensate for low wind power generation intervals. An alternative would be to store wind energy during periods of high generation (e.g., by producing hydrogen or ammonia) and use it during periods of low generation. Utilizing energy storage methods, wind energy can be continuously used for longer periods of time and provide a suitable constant power source for the studied case. Higher constant power can also be provided by increasing the efficiency of energy recovery and storage processes. Alternatively, these two technologies may be integrated with gas turbines if the required storage cannot be provided or higher power is required. It was estimated that the integration of wind energy could result in noticeable reductions in CO2 emissions for the case study. Additionally, according to the results, the production, storage, and reuse of hydrogen and ammonia on-site may be viable options for supplying power.

Stern-Gerlach effect of vector light bullets in a nonlocal Rydberg medium.

We show that stable (3+1)-dimensional vector light bullets with ultraslow propagating velocity and extreme low generation power can be realized in a cold Rydberg atomic gas. They can also be actively controlled by using a nonuniform magnetic field; especially, trajectories of their two polarization components can have significant Stern-Gerlach deflections. The results obtained are useful for revealing the nonlocal nonlinear optical property of Rydberg media and for measuring weak magnetic fields.

Improvement of Voltage Collapse of MPPT Single-stage Photovoltaic Grid-connected based on Conductance Increment Method

In order to make the supply of resources meet the rapidly developing world situation, it is of great practical significance to further develop and apply renewable resources. PV power system has many advantages, such as cleanness, environmental protection, high efficiency, etc., and shows great application potential in the field of new energy. At present, solar cells are easily affected by external factors such as light intensity, temperature, etc., and can't work at the maximum power point continuously and stably, resulting in low power generation efficiency. Therefore, the introduction of Maximum power point tracking (MPPT) technology is particularly important. In this paper, a variable step conductance increment method is proposed, which can identify the current distance from the maximum power point by observing algorithm, change the tracking step and quickly identify the maximum power point, so as to solve the voltage collapse problem of single-stage photovoltaic grid-connection. Simulation results show that the new algorithm can optimize both dynamic response and steady-state oscillation, and improve the accuracy and speed of MPPT.

Characterization of Spirogyra sp. Using Thermogravimetric/ Derivative Thermogravimetric (TG/DTG) Analysis and Bomb Calorimeter for Energy Application

Biomass is usually considered as different types of lignocellulosic materials having varied composition potential to utilize in the useful forms of energy as a substitute of conventional fossil fuels. Algal biomass has multi facet application in research and development such as source of nutrients, biochemical, cosmetics and biofuels. However, this newly developed energy source met the requirement of low and medium scale power generation due to low thermal efficiency. In present study, freshwater algae Spirogyra sp. taken as source of biomass and analyzed for Thermogravimetric (TG) and calorific values analysis. We found the calorific value is 2129.4 Kcal/Kg and TGA results show that algal biomass decrease rapidly after reaching the temperature over 300°C. The result obtained in this paper may be used in future as reference material for algae based biomass for energy application.

Experimental study on medium and low temperature geothermal ammonia power generation system based on vertical tube falling film

China’s geothermal energy resources are mainly low and medium temperature, the process of ammonia solution generation and absorption is introduced to simplify the condensation heat transfer of Karina cycle, and the vertical tube falling film structure is adopted for the generator and absorber in the system, which makes the system more suitable for medium and low temperature geothermal resources. A 5 kW ammonia water power cycle power generation experimental platform based on vertical tube falling film was built. The experimental results show that under typical working conditions, the maximum heat transfer coefficient of generator and absorber can reach 1034 w/(m2 K) and 563 w/(m2 K), respectively, and the maximum output power of the system is 3 kW.

Development of low power and high voltage RF signal generator

Ion confinement technology can be widely used in quantum computation and precision measurement. In ion trapping system, ions are stably trapped in ion trap by the action of external forces.Multi-ion confinement requires the joint action of electric field and magnetic field to make the trapped ions overcome the interaction force between ions and be stably confined in the same specific space. Therefore, the stability of the electric force and the magnetic force determines the stability of ion confinement. Although the electric field and magnetic field provided by traditional commercial instruments is stable, it is not conducive to the miniaturization of the device. According to the previous experiment of ion confinement, we have designed a radio frequency(RF) signal generator that can provide continuous low power and stable high voltage RF electric field for multi-ion confinement system to guarantee the stability of trapped ions in quadrupole linear ion trap, also to improve the tapped ions density.

The preparation of PANI-doped Co-Ni-ZIF carbonized derivatives and the exploration of EET process by the DFT calculation and the prediction of related functional genes

As a green conversion/energy storage device, the practical application of microbial fuel cell (MFC) was limited with its low power generation. The extracellular electron transfer efficiency was one of the key factors affecting the power generation performance of MFC. This paper reported the carbonized derivative Co-Ni-ZIF@NC derived from PANI-doped Co-Ni-ZIF with conductivity, biocompatibility and high electrocatalytic activity. Density functional theory (DFT) confirmed the strong interaction between the electrode surface and microorganisms. The maximum power density of the MFC with Co-Ni-ZIF@NC anode (8.67 W/m3) was 1.47 time higher than that of Co-Ni-ZIF@C-800 (5.96 W/m3). High-throughput sequencing revealed that Co-Ni-ZIF@NC catalyst facilitated the screening of relevant functional microbial communities in microbial membranes, leading to the reinforcement of power generation in MFC. PICRUSt predicted the relative abundance of functional genes, confirmed the spontaneous enrichment behaviour of functional microorganisms to the electrode surface, and identified cytochrome c552 as the dominant role in the EET process. The above foregoing mainly due to the doping of PANI, improved the content of pyrrolic N on the surface of derivatives, protected the original crystal morphology, promoted the approaching behaviour of conductive flagella to the anode surface and shortened the electron transport distance, thus Co-Ni-ZIF@NC exhibited superb bioelectrocatalytic activity.

Research on medium–low temperature geothermal power generation system

In order to make full use of the medium and low temperature geothermal resources and industrial waste heat resources, a power cycle system using ammonia–water mixed solution as the working fluid is proposed. The system can use medium and low temperature geothermal resources with a temperature of 350–450 K, and the basic circulating working fluid is ammonia aqueous solutions. Simulation calculations show that the Carnot cycle efficiency of the circulation system is 14.01%, and the theoretical cycle thermal efficiency of the circulation system is 10.28%. The article further analyzes the influence of steam turbine outlet pressure and heat source temperature on the thermal efficiency of the circulation system. This research provides a reference for the effective utilization of medium and low temperature waste heat resources.

Thermodynamic analysis and optimization of a hybrid power system using thermoradiative device to efficiently recover waste heat from alkaline fuel cell

Low-grade waste heat released from alkaline fuel cells (AFCs) contains enormous useful energy, which can be recycled for energy cascade utilization. However, the traditional heat energy harvesting techniques are limited by low power generation and conversion efficiency. In this work, an alkaline fuel cell/thermoradiative device hybrid system is proposed to address this challenge, where the thermoradiative device (TRD) recycles the waste heat from an AFC, thereby providing additional electrical power. A comprehensive mathematical model of the hybrid system is developed to investigate its general performance characteristics and optimal parameter designs. The hybrid system possesses better output performance than other previously proposed AFC-based hybrid systems, which indicates that the TRD can more efficiently harvest the waste heat produced from AFC than other conventional cogeneration devices. The maximum power density of the hybrid system can be as much as 1.75 times that of the single AFC, and hence, the hybrid system can offer a significant performance boost. Additionally, the optimal operating regime and the critical parameter designs are determined, offering theoretical guidance for improving system performance. The presented work shall pave new routes and provide essential guidelines for designing high-performance waste heat recycling devices.

A Review of Recent Advances in Microbial Fuel Cells: Preparation, Operation, and Application.

The microbial fuel cell has been considered a promising alternative to traditional fossil energy. It has great potential in energy production, waste management, and biomass valorization. However, it has several technical issues, such as low power generation efficiency and operational stability. These issues limit the scale-up and commercialization of MFC systems. This review presents the latest progress in microbial community selection and genetic engineering techniques for enhancing microbial electricity production. The summary of substrate selection covers defined substrates and some inexpensive complex substrates, such as wastewater and lignocellulosic biomass materials. In addition, it also includes electrode modification, electron transfer mediator selection, and optimization of operating conditions. The applications of MFC systems introduced in this review involve wastewater treatment, production of value-added products, and biosensors. This review focuses on the crucial process of microbial fuel cells from preparation to application and provides an outlook for their future development.

Characterizing the variability and meteorological drivers of wind power and solar power generation over Africa

AbstractSub‐Saharan Africa (SSA) has the lowest energy access rates in the world, which poses a key barrier to power system development. Deployment of renewables, including wind and solar power, will play a key role in expanding electricity supply across SSA: distributed generation (enabling access for remote communities), cost‐effectiveness and low emissions are key advantages. However, renewable generation is weather dependent; therefore, including more renewables increases the amount of meteorologically driven variability in the power system. Two countries in SSA are chosen for detailed investigation of this meteorologically driven variability: Senegal in West Africa and Kenya in East Africa. These are chosen due to being areas of dense population, where there is operational wind and solar power, and plans for regional expansion. In Senegal, solar generation is fairly consistent throughout the year, while wind generation exhibits strong seasonality, with a peak in the boreal spring. Low wind and solar power generation days during the boreal summer are found to be related to the passage of African Easterly Waves. Over Kenya, both wind and solar generation exhibit seasonal variability, with wind generation peaking during boreal autumn, and solar generation at a minimum during boreal summer. Inter‐annual variability in generation is greater over Kenya than over Senegal; the El Nino Southern Oscillation is found to impact wind and solar generation over Kenya. El Nino phases are associated with lower wind and solar generation in October–December over Kenya, but higher generation in July–September. This improved understanding of variability will assist system planners in designing reliable future energy systems.

Modeling and optimization of a novel Oxy-fuel/Solar/Wind/Battery power generation system

• The optimized combined system can perfectly meet the needs of electricity grid. • The cold energy of LNG is used to condense CO 2 and nearly zero CO 2 emissions is achieved. • The optimal model is obtained by considering various wind-solar ratios and scales of battery storage capacity. • The LCOE of the combined system is reduced by 3% to 6% with the employment of solar-wind energy. It is proposed and built a novel oxy-fuel/solar/wind/battery power generation system. It consists of a solar-wind renewable system (SWRS) with battery bank and a liquefied natural gas-fueled oxy-fuel combined cycle (OFCC). The work is unique in that it uses SWRS to power OFCC’s main energy-consuming equipment, such as the recycled CO 2 compressor (RCC) and air separation unit (ASU). SWRS power is consumed locally, avoiding the negative effects of SWRS intermittency and variability on the electricity grid. CO 2 is compressed, cooled and then condensed by evaporating the cold LNG. MATLAB/Simulink and Aspen Plus were used to create the SWRS and OFCC, respectively. In order to find the optimal model of the combined system in terms of economic factors, various wind-solar ratios, scales of SWRS and OFCC, and battery storage capacity have been considered and combined. The results show that the optimized combined system can perfectly meet the needs of the electricity grid while having a high renewable energy utilization efficiency, no negative impact on power grid stability, low power generation costs, and low CO 2 emissions. This work will serve as a guide for the combined power system’s power supply planning.

Stable High‐Dimensional Weak‐Light Soliton Molecules and Their Active Control

AbstractBound states of solitons, alias soliton molecules (SMs), are well known in 1D systems, while making stable bound states of multidimensional solitons is a challenging problem because of the underlying instabilities. Here, a scheme for the creation of stable (2+1)D and (3+1)D optical SMs in a gas of cold Rydberg atoms is proposed, in which electromagnetically induced transparency (EIT) is induced by a control laser field. It is shown that, through the interplay of the EIT and the strong long‐range interaction between the Rydberg atoms, the system gives rise to giant nonlocal Kerr nonlinearity, which in turn supports stable (2+1)D spatial optical SMs, as well as ring‐shaped soliton necklaces, including rotating ones. They feature a large size, low generation power, and can be efficiently manipulated by tuning the nonlocality degree of the Kerr nonlinearity. Stable (3+1)D spatiotemporal optical SMs, composed of fundamental or vortex solitons, with low power and ultraslow propagation velocity, can also be generated in the system. These SMs can be stored and retrieved through the switching off and on of the control laser field. The findings reported here suggest applications to data processing and transmission in optical systems.

Electrospun PA66/Graphene Fiber Films and Application on Flexible Triboelectric Nanogenerators.

Triboelectric nanogenerators (TENGs) are considered to be the most promising energy supply equipment for wearable devices, due to their excellent portability and good mechanical properties. Nevertheless, low power generation efficiency, high fabrication difficulty, and poor wearability hinder their application in the wearable field. In this work, PA66/graphene fiber films with 0, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt% graphene and PVDF films were prepared by electrospinning. Meanwhile, TENGs were prepared with PA66/graphene fiber films, PVDF films and plain weave conductive cloth, which were used as the positive friction layer, negative friction layer and the flexible substrate, respectively. The results demonstrated that TENGs prepared by PA66/graphene fiber films with 2 wt% grapheme showed the best performance, and that the maximum open circuit voltage and short circuit current of TENGs could reach 180 V and 7.8 μA, respectively, and that the power density was 2.67 W/m2 when the external load was 113 MΩ. This is why the PA66/graphene film produced a more subtle secondary network with the addition of graphene, used as a charge capture site to increase its surface charge. Additionally, all the layered structures of TENGs were composed of breathable electrospun films and plain conductive cloth, with water vapor transmittance (WVT) of 9.6 Kgm−2d−1, reflecting excellent wearing comfort. The study showed that TENGs, based on all electrospinning, have great potential in the field of wearable energy supply devices.

Electrochemical impedance spectroscopy applied to microbial fuel cells: A review.

Electrochemical impedance spectroscopy (EIS) is an efficient and non-destructive test for analyzing the bioelectrochemical processes of microbial fuel cells (MFCs). The key factors limiting the output performance of an MFC can be identified by quantifying the contribution of its various internal parts to the total impedance. However, little attention has been paid to the measurement conditions and diagrammatic processes of the EIS for MFC. This review, starting with the analysis of admittance of bioelectrode, introduces conditions for the EIS measurement and summarizes the representative equivalent circuit plots for MFC. Despite the impedance from electron transfer and diffusion process, the effect of unnoticeable capacitance obtained from the Nyquist plot on MFCs performance is evaluated. Furthermore, given that distribution of relaxation times (DRT) is an emerging method for deconvoluting EIS data in the field of fuel cell, the application of DRT-analysis to MFC is reviewed here to get insight into bioelectrode reactions and monitor the biofilm formation. Generally, EIS measurement is expected to optimize the construction and compositions of MFCs to overcome the low power generation.

A contextual framework development toward triboelectric nanogenerator commercialization

The world is experiencing the third wave of electronic commerce, in which battery-free electronics dominate the market share. Additionally, the wide distribution of the sensors and high maintenance costs make batteries an insufficient solution, especially for remote or inaccessible areas. Powering the internet of things (IoT) would be impossible without making the sensors self-powered by harvesting energy from the working environment to ensure long-term operation. Besides, self-powering is a significant advancement for wireless sensing and the emerging IoT trend, where nanogenerators emerge as a compelling platform technology. However, nanogenerator-enabled self-powered systems still introduce a slew of new challenges, including the grand challenge of relatively low power generation in most energy-harvesting modalities. Therefore, it is crucial to alleviate various technical, operational, and social barriers of nanogenerator-based devices and present their potential mitigation solutions. Here, ten significant barriers are scrutinized in terms of the market adoption of triboelectric nanogenerator (TENG)-based technologies, and interrelationships among them are examined using a total interpretive structural modeling (TISM) approach and cross-impact matrix multiplication applied to classification (MICMAC) analysis. The findings of this study can help key players in this field understand the most significant impediments to TENG market adoption, which can revolutionize wireless and distributed electronics without batteries.

An ANN based switching network for optimally selected photovoltaic array with battery and supercapacitor to mitigate the effect of intermittent solar irradiance

ABSTRACT Power fluctuation at the PV panel output is caused by variation of input irradiance. Several optimization techniques have been used for selecting the Global Maximum Power Point (GMPP) from different Local Maximum Power Point (LMPP) that are caused due to variable irradiance. Reconfiguring the PV array by various combination based on the available irradiance is used to overcome the effects of partial shading. In these methods, system complexity increases and efficiency reduces as the size of PV array increases. Hence, in this paper Artificial Neural Network (ANN) based switching network of optimum number of PV panel with battery and supercapacitor is formed. Genetic Algorithm (GA) is used to optimize the number of PV panels, battery and supercapacitor. Battery and supercapacitors are used as energy back up to support the load during low power generation from PV panels. Size of supercapacitors is calculated to support the system during instant power fluctuation caused either due to sudden increase in load or unexpected variation in irradiance. Power enhancement of optimized PV array is performed by ANN based switching and numerically analyzed, and compared with other reconfiguration methods. Optimization is carried out for a system having 245 kW load which led to 1281 number of PV panels, 161 number of batteries and 8 supercapacitors for minimum cost of energy sources. Results of optimization are used for switching of 1281 PV array to form 16 × 81 strings. Out of which 16 × 9 strings are selected for Month Ahead Scheduling (MAS) and string of 16 × 1 PV panels for Real Time Scheduling (RTS). Considering variations at the input irradiance while load is constant. For the selected value of irradiance 16 × 45 strings remain ON which is selected as the base value.