Autonomous Generation System Research Articles

Photo-driven autonomous hydrogen generation system based on hierarchically shelled ZnO nanostructures

A quantum dot semiconductor sensitized hierarchically shelled one-dimensional ZnO nanostructure has been applied as a quasi-artificial leaf for hydrogen generation. The optimized ZnO nanostructure consists of one dimensional nanowire as a core and two-dimensional nanosheet on the nanowire surface. Furthermore, the quantum dot semiconductors deposited on the ZnO nanostructures provide visible light harvesting properties. To realize the artificial leaf, we applied the ZnO based nanostructure as a photoelectrode with non-wired Z-scheme system. The demonstrated un-assisted photoelectrochemical system showed the hydrogen generation properties under 1 sun condition irradiation. In addition, the quantum dot modified photoelectrode showed 2 mA/cm2 current density at the un-assisted condition.

Voltage and frequency control of an autonomous hybrid generation system based on linear model predictive control

This paper presents an adaptive control for voltage and frequency regulation of a stand-alone hybrid wind-diesel power system based on constrained linear model predictive control (MPC). The proposed system mainly consists of a wind turbine driving a self-excited induction generator (SEIG) connected via a DC link to a synchronous generator (SG) driven by a diesel engine. The SG is equipped with a voltage regulator and a static exciter. The wind generator and the synchronous generator together cater for the local load and power requirement. However, the load bus voltage and frequency are governed by the SG. To extract maximum available wind power, it is assumed that the wind generation system operates free without control. The control objective aims to control the load voltage and frequency. This is achievement via controlling the field voltage and rotational speed of the SG. The MPC controller is based on the minimization of a cost function of voltage and rotor speed errors while respecting the given constraints. The hybrid wind-diesel energy system with the proposed MPC has been tested through a turbulent and step change in wind speed and load impedance respectively. Simulation results show that accurate tracking performance of the system has been achieved.

GA based frequency controller for solar thermal–diesel–wind hybrid energy generation/energy storage system

Wind, Solar photovoltaic and solar thermal power systems are emerging renewable energy technologies and can be developed as viable options for electricity generation in future. In this paper, autonomous hybrid generation systems consisting of wind turbine generators (WTGs), solar thermal power system (STPS), solar photovoltaic (PV), diesel engine generators (DEGs), fuel cells (FCs), battery energy storage system (BESS), flywheel (FW), ultra capacitors (UCs) and aqua electrolyzer (AE) have been considered for simulation studies. The power system frequency deviates for sudden changes in load or generation or the both. The comparative performance of the controllers installed to alleviate this frequency deviation for different hybrid systems, is carried out using time domain simulation. In practice, controllers (PI or PID) are tuned manually which is difficult and time consuming. The computational intelligence has opened paths to a new generation of advanced process control. Here, GA is used for optimization of controllers’ gains of the proposed hybrid systems. The simulation results demonstrate the effectiveness of the GA based controllers in terms of reduced settling time, overshoot and oscillations. The results are compared with conventional controllers.

Optimum sizing of photovoltaic-energy storage systems for autonomous small islands

The electrification of autonomous electrical networks is in most cases described by low quality of electricity available at very high production cost. Furthermore, autonomous electrical networks are subject to strict constraints posing serious limitations on the absorption of RES-based electricity generation. To by-pass these constraints and also secure a more sustainable electricity supply status, the concept of combining photovoltaic power stations and energy storage systems comprises a promising solution for small scaled autonomous electrical networks, increasing the reliability of the local network as well. In this context, the present study is devoted to develop a complete methodology, able to define the dimensions of an autonomous electricity generation system based on the maximum available solar potential exploitation at minimum electricity generation cost. In addition special emphasis is given in order to select the most cost-efficient energy storage configuration available. According to the calculation results obtained, one may clearly state that an optimum sizing combination of a PV generator along with an appropriate energy storage system may significantly contribute on reducing the electricity generation cost in several island electrical systems, providing also abundant and high quality electricity without the environmental and macroeconomic impacts of the oil-based thermal power stations.

An Optimum Sizing Methodology for Combined Photovoltaic-Energy Storage Electricity Generation Configurations

The electrification of autonomous electrical networks is in most cases described by low quality of electricity available at very high production cost. Furthermore, autonomous electrical networks are subject to strict constraints posing serious limitations on the absorption of renewable energy sources (RES)-based electricity generation. To bypass these constraints and also to secure a more sustainable electricity supply status, the concept of combining photovoltaic (PV) power stations and energy storage systems comprises a promising solution for small scaled autonomous electrical networks, increasing the reliability of the local network as well. In this context, the present study is devoted in developing a complete methodology, able to define the size of an autonomous electricity generation system, based on the maximum available solar potential exploitation at minimum electricity generation cost. In addition special emphasis is given in order to select the most cost-efficient energy storage configuration available. According to the calculation results obtained, one may clearly state that an optimum sizing combination of a PV generator along with an appropriate energy storage system may significantly contribute on reducing the electricity generation cost in several island electrical systems, providing also abundant and high quality electricity without the environmental and macro-economic impacts of the oil-based thermal power stations.

A new computational algorithm for the calculation of maximum wind energy penetration in autonomous electrical generation systems

The entirety of Aegean Sea Islands, including Crete, is characterized during the last decade by a considerable annual increase of the electrical power demand exceeding the 5% in annual basis. This continuous amplifying electricity consumption is hardly fulfilled by several outmoded internal combustion engines usually at a very high operational cost. On the other hand most of the islands possess high wind potential that may substantially contribute in order to meet the corresponding load demand. However, in this case some wind energy absorption problems related with the collaboration between wind parks and the local electricity production system cannot be neglected. In this context, the present study is devoted to realistically estimating the maximum wind energy absorption in autonomous electrical island networks. For this purpose a new reliable and integrated numerical algorithm is developed, using the available information of the corresponding electricity generation system, in order to calculate the maximum acceptable wind power contribution in the system, under the normal restrictions that the system manager imposes. The proposed algorithm is successfully compared with existing historical data as well as with the results of a recent investigation based almost exclusively on the existing wind parks energy production.

Some results on the autonomous trajectory generation and adaptive control of industrial robots

Part I of this paper presents a study of an autonomous trajectory generation system (ATGS) which is useful for industrial robots carrying out mechanical operations. It is a very simple job with such an ATGS to generate planar curved trajectories f(x, y) = 0, an attractive factor in such applications. Two alternative variations of the ATGS are presented which possess particular characteristics. Part II deals with the trajectory control problem and uses the ATGS as a first stage of a model reference adaptive control loop of a robot. The theoretical results are illustrated by simulation examples worked out using the software packages developed for this purpose.

Autonomous system expansion planning considering renewable energy sources-a computer package

The authors describe the interactive package ASP (Autonomous System Planning), which determines the optimal expansion plan of an autonomous generation system including diesel units, wind generators, and photovoltaic generators. Utilizing meteorological data, load demand data and estimated economical parameters, the package finds the optimal system expansion policy for a period of N years. The solution algorithms implemented in the package recognize planning and operational constraints and take into consideration the stochastic nature of the meteorological conditions, loads, and the availability of the diesel units. >