Autonomous Renewable Energy System Research Articles

Оценка потенциала Российской Федерации и Узбекистана для внедрения солнечных систем возобновляемой энергетики

The main drawback of the modern power supply system is centralization. Renewable energy is a promising alternative for supplying electricity to remote settlements. Solar energy is more preferable, since it is least dependent on the geographical location. (Research purpose) The research purpose is in studying the possibilities of creating an autonomous renewable energy system based on solar photoconvertors for remote villages. (Materials and methods) Authors examined small rural settlements in various climatic regions of the Russian Federation and Uzbekistan, identified promising regions for solar-powered systems similar in climatic and socio-economic parameters – the Krasnodar Territory and the regions of Uzbekistan. There was used data from the NASA POWER project for analysis. (Results and discussion) The article presents the comparison of a diesel generator and a renewable solar-diesel system as an autonomous source of electricity for small settlements. Due to the lack of sun in winter and due to lower temperatures, there is a need for an additional source of energy. (Conclusions) The article presents the methodology for assessing the technical and economic potential of renewable energy sources in the regions under consideration. Due to the high solar activity and geographical location, the cost of energy in the regions of Uzbekistan was 0.153, 0.155, 0.166 dollars per kilowatt-hour for hybrid renewable energy systems and 0.387, 0.371, 0.401 dollars per kilowatt-hour for a diesel generator. In the Krasnodar Territory these costs are 0.138 dollars per kilowatt-hour for a hybrid system and 0.316 dollars per kilowatt-hour for a diesel generator. It is possible to create fully autonomous power supply stations in these regions based on solar energy stations. For this purpose it is necessary to add an energy source that will be used during periods of insufficient solar activity. The most promising solution is the use of a wood gas source.

Assessment of the feasibility of hybrid renewable power for supply pumping system for irrigation

Crop identification is vital to make an inventory of the crops grown in a given area and their cultivation period. The Remote sensing (RS) techniques can provide information on the distribution of cultivated land, crop types, and areas for the agricultural sector's effective management.
 In remote sensing, various vegetation indices (VI) can analyze and evaluate multiple phenomena and themes. The Normalized Difference Vegetation Index (NDVI) is an essential and highly significant remote measurement widely used in agriculture for phenological monitoring and crop health (Ray and Dadhwal, 2001).
 In this work, we present a methodology for the contribution of NDVI from Landsat 7 (TM) and (ETM+) images to crop mapping in the Gharb region using a classification based on the pixel approach and estimating rice crop coefficient from NDVI.
 The classification results concern six main types of crops planted in this region (beet, maize, sugar cane, market gardening, cereals, and rice). The classification map showed differences in agricultural practices adopted by farmers in crop spatial distribution. The classification results showed the ability of this methodology to discriminate between crops.
 Crop coefficients were deduced from the NDVI extracted from the images. Due to meteorological data collected from the meteorological station TCSC of SK Tlet, the estimation of the reference evapotranspiration was made and subsequently the potential evapotranspiration of each crop during the agricultural season 2019-2020.
 The highest values for ETC were obtained when the crop was in its full development when water was mainly lost through transpiration after a slight decrease in the ratio values observed during the phase of the vegetative cycle (maturity).
 The water requirements (daily, monthly and annual) for the crops were determined and their electrical energy consumption.
 Renewable energy can be an effective solution to meet the energy needs of plots , greenhouses and large farms.
 A technical-economic study of different combinations of autonomous hybrid renewable energy systems (HRES) in order to meet the power supply needs of the above mentioned crops in the Gharb region. The renewable energy sources considered are solar, wind and biomass. The results show that for an average energy requirement of 92 kWh/day and a peak load of 6.5 kW, the unit energy cost of the optimal configuration scenario A (PV-wind-biomass-battery) is 0.19 $/kWh. Therefore, the design, development and implementation of the proposed system is a promising solution for the security of energy supply. For a 100% integration of renewable energy, the HRES produces electricity according to the following distribution: 11% from wind, 41% from solar and 48% from biomass.

Assessment of autonomous renewable energy system operability under extreme events and disasters

Autonomous, hybrid renewable energy systems (HRES) are increasingly being deployed in geographically challenging terrains, often lacking adequate resilience planning for natural disasters. An assessment framework is developed to evaluate sustainable HRES design for remote off-grid application, ensuring its operability under an extreme event, i.e. its ability to absorb the shock event and continue operating. Optimal HRES configurations are obtained for different extreme events, applying Pareto optimality with key criteria of minimising the number of black outs constrained by Net Present Cost (NPC). The framework is demonstrated for a remote location in Chile. Operability of an HRES under an extreme event is found to involve a trade-off between the investment decision to reduce the vulnerability of RET components and to enhance its energy storage. The optimised HRES is found to be cost-effective for resilience against seasonal events (for flooding and snowstorm the additional NPC is 4.6%, 7.4% respectively) but unsustainable for low probability-high impact events (for earthquakes the additional NPC of 20.5% largely from increase investment in storage capacity). The study also highlights the role of the dispatch strategy in enabling a micro hydro as a secondary storage component for both fulfilling the unmet loads and for charging batteries.

A Demand-Supply Matching-Based Approach for Mapping Renewable Resources Towards 100% Renewable Grids in 2050

Recently, many renewable energy (RE) initiatives around the world are based on general frameworks that accommodate the regional assessment taking into account the mismatch of supply and demand with pre-set goals to reduce energy costs and harmful emissions. Hence, relying entirely on individual assessment and RE deployment scenarios may not be effective. Instead, developing a multi-faceted RE assessment framework is vital to achieving these goals. In this study, a regional RE assessment approach is presented taking into account the mismatch of supply and demand with an emphasis on Photovoltaic (PV) and wind turbine systems. The study incorporates mapping of renewable resources optimized capacities for different configurations of PV and wind systems for multiple sites via test case. This approach not only optimizes system size but also provides the appropriate size at which the maximum renewable energy fraction in the regional power generation mix is maximized while reducing energy costs using MATLAB’s ParetoSearch algorithm. The performance of the proposed approach is tested in a realistic test site, and the results demonstrate the potential for maximizing the RE share compared to the achievable previously reported fractions. The results indicate the importance of resource mapping based on energy-demand matching rather than a quantitative assessment of anchorage sites. In the examined case study, the new assessment approach led to the identification of the best location for installing a hybrid PV / wind system with a storage system capable of achieving a nearly 100% autonomous RE system with Levelized cost of electricity of 0.05 USD/kWh.

Autonomous renewable energy systems in Russia. Critical review of the current situation

This paper presents the current situation in Russia’s autonomous renewable energy system. The main challenges facing regional authorities and project-implementing companies are described. The current tender procedure detailing main issues resulting in project failure is given. The paper also outlines current interactions between companies and relevant research centers. Special attention is given to issues in renewable energy project appraisal.Ongureny, an autonomous energy system located in Irkutsk Oblast (Eastern Siberia, Russia), is cited as a notable and sad example of all the shortcomings in the present-day autonomous renewable energy sector in Russia.To conclude, the author makes a list of measures intended to rectify this situation and highlights the importance of energy service agreements which remain underdeveloped in the Russian renewable energy sector.This paper aims to present key issues relating to autonomous renewable energy in Russia and suggestions on how to address them.

Settling of rural population as the economy-geographical background for efficiency of small-scaled autonomous renewable energy systems

Settling of rural population as the economy-geographical background for efficiency of small-scaled autonomous renewable energy systems

Energy Management for an Autonomous Renewable Energy System

In this paper a controller and an management of production systems focusing on energy from renewable sources is presented. The main result is optimize the energy extracted from renewable sources to and effectively control the charging and discharging of the battery. An algorithm based on fuzzy logic is developed to determine the degree of involvement of each source. Then we develop the controls in power converters installed in the system to properly manage and respond to instructions from the management algorithm. To validate this technique, simulation results are presented.

Prospects of Wind-Diesel Generator-Battery Hybrid Power System: A Feasibility Study in Algeria

The present work analyses the feasibility of a wind-diesel generator-battery hybrid system. The wind energy resource data are collected from the weather station at the Renewable Energy Development Center of Bouzareah in Algeria. The recorded values vary from 5.5 m/s to 7 m/s at 25 m. The hybrid system analysis has shown that for a household consuming 1,270 kWh/yr, the cost of energy is 1.205 USD/kWh and produces 2,493 kWh/yr in which 93% of electricity comes from wind energy. From this study, it is clear that the optimized hybrid system is more cost effective compared to the diesel generator system alone where the NPC and COE are equal, respectively, to 19,561 USD and 1.205 USD/kWh and 47,932 USD and 2.952 USD/kWh. The sensitivity analysis predicts that the grid extension distance varies from 1.25 to 1.85 km depending on wind speed and fuel price which indicate a positive result to implement a stand-alone hybrid power system as an alternative to grid extension. In addition to the feasibility of this system, it can reduce the emission of the CO2, SO2, and NOx, respectively, from 4758 to 147, from 9.45 to 0.294, and from 105 to 3.23 kg/yr. Investments in autonomous renewable energy systems should be considered particularly in remote areas. They can be financed in the framework of the National Energy Action Plan of Algeria.

04/02455 Can photovoltaic technologies help attain sustainable rural development in Bangladesh?: Biswas, W. K. et al. Energy Policy, 2004, 32, (10), 1199–1207

The Hydrogen Research Institute (HRI) has developed a stand-alone renewable energy (RE) system based on energy storage in the form of hydrogen. When the input devices (wind generator and photovoltaic array) produce more energy than is required by the load, the excess energy is converted by an electrolyzer to electrolytic hydrogen, which is then stored after stages of compression, purification and filtration. Conversely, during a time of input energy deficit, this process is reversed and the hydrogen produced earlier is reconverted to electrical energy through a fuel cell. The oxygen which has been produced by the electrolyzer during the hydrogen production is also stored at high pressure, after having gone through a purification and drying process. This stored oxygen can be re-utilized as oxidant in place of compressed air in the fuel cell. The modifications of the electrolyzer for oxygen storage and re-utilization of it as oxidant for the fuel cell are presented. Furthermore, the HRI has designed and developed the control system with power conditioning devices for effective energy management and automatic operation of the RE system. The experimental results show that a reliable autonomous RE system can be realized for such seasonal energy sources, using stored hydrogen as the long-term energy buffer, and that utilizing the electrolyzer oxygen by-product as oxidant in the fuel cell increases system performance significantly.

Electrolytic hydrogen based renewable energy system with oxygen recovery and re-utilization

The Hydrogen Research Institute (HRI) has developed a stand-alone renewable energy (RE) system based on energy storage in the form of hydrogen. When the input devices (wind generator and photovoltaic array) produce more energy than is required by the load, the excess energy is converted by an electrolyzer to electrolytic hydrogen, which is then stored after stages of compression, purification and filtration. Conversely, during a time of input energy deficit, this process is reversed and the hydrogen produced earlier is reconverted to electrical energy through a fuel cell. The oxygen which has been produced by the electrolyzer during the hydrogen production is also stored at high pressure, after having gone through a purification and drying process. This stored oxygen can be re-utilized as oxidant in place of compressed air in the fuel cell. The modifications of the electrolyzer for oxygen storage and re-utilization of it as oxidant for the fuel cell are presented. Furthermore, the HRI has designed and developed the control system with power conditioning devices for effective energy management and automatic operation of the RE system. The experimental results show that a reliable autonomous RE system can be realized for such seasonal energy sources, using stored hydrogen as the long-term energy buffer, and that utilizing the electrolyzer oxygen by-product as oxidant in the fuel cell increases system performance significantly.

Analysis of battery current microcycles in autonomous renewable energy systems

Battery currents in autonomous renewable energy systems (RES) are generally predicted or measured in terms of mean values over intervals of 1 min or longer. As a result, battery charge–discharge cycles with periods less than the averaging period are ignored, and the actual battery ampere hour (A h) throughput and resulting battery wear may be seriously underestimated, leading to optimistic prediction of battery lifetime. This paper considers short charge–discharge cycles or microcycles, arising from the characteristics of autonomous renewable energy systems, including generators, regulators, loads, and load inverter. Simulation results are used to show that inverters operating directly from the battery can cause microcycles, resulting in significantly increased battery throughput. Initial experimental results of the effects of microcycles on battery capacity and charging characteristics, and the contributing processes, are discussed.

Distributed load control of autonomous renewable energy systems

Autonomous renewable energy systems such as wind, solar, and micro-hydro require control methods to maintain stability, due to the real time variation of input energy and load, while maximizing the use of renewable energy. This paper describes the application of load control using a novel frequency and voltage-sensing device. The device uses a low cost microcontroller to monitor the system frequency and voltage. Load switching is carried out based on this information. Software was developed for frequency and voltage measurements and tested on a 18 kW, single phase, 50 Hz, micro-hydro system. A fuzzy control system was then developed which makes intelligent load switching decisions using inputs from the measurement algorithms coupled with expert knowledge expressed in the form of control rules. This load control system was then tested on the same micro-hydro system and on a site powered by a 60 kW, 3 phase, 50 Hz wind turbine only.

‘ARES’—A refined simulation program for the sizing and optimisation of autonomous hybrid energy systems

This article outlines several enhancements made to autonomous renewable energy systems (ARES)-I, the Cardiff School of Engineering's hybrid photovoltaic and wind energy simulation program. The resulting program, ARES-II, unlike the majority of other hybrid simulation programs, predicts the battery state of voltage (SoV) rather than its state of charge (SoC). Loss of load (LoL) occurs when the battery voltage drops below the low voltage cut off limit. Given load and weather profiles, ARES-II is able to predict the occurrence of loss of load thus giving a direct measure of the system autonomy. The enhanced model also predicts the effect of different battery temperatures on the LoL. Experimental work has shown a significant change in storage battery resistance and capacity with temperature. Incorporating battery temperature effects into the battery algorithm is a novel advancement in hybrid system voltage simulation. Further refinements have also been made to the voltage controller algorithms. Accurate modelling of the non-linear action of the low voltage controller is of paramount importance when predicting loss of load probability for hybrid systems. Combining all the above features and incorporating them into ARES-II produces a simple, accurate and reliable method for hybrid system design and LoL prediction as a function of the combined variability in the weather and load.

Optimization and control of autonomous renewable energy systems

Recently, there has been a growing interest in harnessing renewable energy resources particularly for electricity generation. One of the main concerns in the design of an electric power system that utilizes renewable energy sources, is the accurate selection of system components that can economically satisfy the load demand. This depends on the load that ought to be met, the capacity of renewable resources, the available space for wind machines and solar panels, and the capital and running costs of system components. Once size optimization is achieved, the autonomous system must be controlled in order to correctly match load requirements with instantaneous variation of input energy. In this paper, a new formulation for optimizing the design of an autonomous wind-solar-diesel-battery energy system is developed. This formulation employs linear programming techniques to minimize the average production cost of electricity while meeting the load requirements in a realiable manner. The computer program developed reads the necessary input data, formulates the optimization problem by computing the coefficients of the objective function and the constraints and provides the optimum wind, solar, diesel, and battery ratings. In order to study the effect of parameters predefined by the designer on the optimum design, several sensitivity analysis studies are performed, and the effects of the expected energy not served, the load level, the maximum available wind area, the maximum available solar area, and the diesel engines' lifetime are investigated. A controller that monitors the operation of the autonomous system is designed. The operation of this controller is based on three major policies; in the first, batteries operate before diesel engines and hence the storage system acts as a fuel saver, while in the second diesel engines are operated first so that the unmet energy is lower but the fuel cost is high. According to the third policy, the supply is made through diesel engines only. This is done for the purpose of making a performance comparison between the isolated diesel system and the hybrid renewable energy system. The proposed optimization and control techniques are tested on Lebanese data. Although three different control policies have been adopted in this work, the software is able to accommodate other policies.

Batteries for autonomous renewable energy systems

Now that the Coconut Island plant has been running successfully for three years, it is appropriate to review the design decisions that were made with regard to the battery and to consider how these might be changed for future systems. The following aspects are discussed: type, package, energy storage, voltage, parallel operation, installation, charging, watering, life and quality assurance.