Reliability Of Energy Systems Research Articles

Multi-criteria PSO-based optimal design of grid-connected hybrid renewable energy systems

ABSTRACT Human-induced climate change through the over liberation of greenhouse gases, resulting in devastating consequences to the environment, is a concern of considerable global significance which has fuelled the diversification to alternative renewable energy sources. The unpredictable nature of renewable resources is an impediment to developing renewable projects. More reliable, effective, and economically feasible renewable energy systems can be established by consolidating various renewable energy sources such as wind and solar into a hybrid system using batteries or back-up units like conventional energy generators or grids. The precise design of these systems is a critical step toward their effective deployment. An optimal sizing strategy was developed based on a heuristic particle swarm optimization (PSO) technique to determine the optimum number and configuration of PV panels, wind turbines, and battery units by minimizing the total system life-cycle cost while maximizing the reliability of the hybrid renewable energy system (HRES) in matching the electricity supply and demand. In addition, by constraining the amount of conventional electricity purchased from the grid, environmental concerns were also considered in the presented method. Various systems with different reliabilities and potential of reducing consumer’s CO2 emissions were designed and the behavior of the proposed method was comprehensively investigated. An HRES may reduce the annualized cost of energy and carbon footprint significantly.

Experimental rig investigation of a direct interconnection technique for airborne wind energy systems

Airborne wind energy is a new approach to reach the stronger and more consistent winds at higher altitudes. In this paper, the interconnection of pumping mode airborne wind energy systems inside an energy farm is investigated. An experimental rig hardware setup has been designed and built to model an AWE farm in small scale. A direct interconnection system has been developed and examined on the experimental test rig. The direct interconnection technique (DIT) is a new method developed for the interconnection of marine wind energy systems within an energy farm, without requiring offshore-based power electronic converters. DIT relocates power electronic converters from the offshore site to the shore substation by interconnecting marine generators directly to a common bus. This method makes possible significant improvements to the economy and reliability of marine renewable energy systems. In this paper, for the first time, the direct interconnection technique is investigated experimentally for physically emulated pumping mode airborne wind energy systems. The construction of the experimental rig hardware setup is described, and the laboratory test results for the direct interconnection of airborne wind energy systems are presented and discussed.

Experimental evaluation of thermal performance of two different finned latent heat storage systems

Enhancing the reliability and acceptability of solar-based thermal energy system requires efficient thermal storage to enable the storage of surplus energy collected during day time for use during non-day light hours. However, most phase change materials (PCMs) used with thermal storages suffer from low thermal conductivity. Fin geometry has a major impact on the heat transfer rates of thermal storage. For this purpose, a comparative thermal performance assessment during charging is achieved for a shell-and-tube-type latent heat storage unit (LHSU) using different fin geometries. An experimental analysis is conducted on three LHSU geometries: non-finned LHSU, longitudinal finned (LF) LHSU (LF-LHSU) and circular finned (CF) LHSU (CF-LHSU). In addition, a visual observation of liquid fraction fronts is applied to confirm the completion of phase change cycles. Experimental results showed that the total charging time reduced by up to 70% and 55% using CF-LHSU and LF-LHSU, respectively. In comparison with the non-finned LHSU, the highest cumulative energy stored enhancement using CF-LHSU was approximately 52%. The experimental comparative assessment suggests that CF-LHSU provides improved charged thermal load operations by a factor of 1.2 as compared with LF-LHSU.

Resilience framework and metrics for energy master planning of communities

Changes in the nature, intensity, and frequency of climate-related extreme events have imposed a higher risk of failure on energy systems, especially those at the community level. Furthermore, the evolving energy demand patterns and transition towards renewable and localised energy supply can affect energy system resilience. How can an energy system be planned and reconfigured to address these challenges without compromising the system’s resilience against chronic stresses and extreme events? Unlike energy system reliability, resilience is neither a common nor an explicit consideration in energy master planning at the community level. In addition, there is no universally agreed-upon method or metrics for measuring or estimating resilience and defining mitigation strategies. This paper introduces a multi-layered energy resilience framework and set of metrics for energy master planning of communities, including the new generation of district energy systems. The potential system disturbances and their short and long-term impacts on various components of the energy system are discussed for commonly expected and extreme events. Three layers of energy resilience are discussed: engineering-designed resilience, operational resilience, and community-societal resilience. A starting set of energy resilience metrics to support engineering design and energy master planning for communities is identified. Implications for future research and practice are noted.

Multi-timescale Forecast of Solar Irradiance Based on Multi-task Learning and Echo State Network Approaches

Solar irradiance forecast is closely related with efficiency and reliability of renewable energy systems. Multi-timescale irradiance forecast is a new and efficient way to simultaneously predict solar energy generation on different timescales for hierarchical decision making. This article newly adopts the multi-task learning mechanism to study the multi-timescale forecast for improving accuracy and computational efficiency. A novel multi-timescale (MTS) prediction framework is presented to fulfill the multi-task application, and echo state network (ESN) is studied in the proposed MTS framework. The multi-timescale ESN (MTS-ESN) is proposed to enhance the information sharing among correlated tasks. Simulation results of hourly solar data demonstrate that the proposed MTS-ESN could achieve promising performance at both hourly and daily level in parallel. The MTS-ESN outperforms the single-timescale ESN (STS-ESN), which indicates the information sharing in the multi-task learning is effective in this application.

Electricity System Assessment and Adaptation to Rising Temperatures in a Changing Climate Using Washington Metro Area as a Case Study

AbstractIncreasing temperatures due to global climate change and the urban heat island effect pose a rising threat to the reliability and security of energy systems. To support climate preparedness...

Optimization of Solar Energy Utilization, System Reliability and Utility Savings using a New Framework

The relevance of focusing on SPV systems with storage to meet the user specific requirement is discussed}. Existing Solar Photovoltaic (SPV) systems are studied and the need for introducing new classification based on the interaction with utility grid, solar module and battery backup, based on load types and end user application is proposed. In order to represent the entire SPV systems a generic framework is introduced known as the three-switch model. All the SPV systems under the new classification can be represented using the framework by changing the switch states. Using this framework, a method to convert existing backup systems into a grid-interactive system is proposed. The ways to enhance maximum solar utilization, utility savings and system reliability are discussed. The states of the grid-interactive systems are discussed and simulated using Typhoon HIL 600.

Operating reserve investigation for the integration of wave, solar and wind energies

The power balance is considered a key requirement for designing a reliable power system that depends on renewable energy sources. To keep the stability of the electrical system and mitigate the power imbalances, an additional generating capacity called the operating reserve should be scheduled to meet the real-time demand. This paper deals with the feasibility of integrating several renewable energies with different nature, considering the operating reserve resulting from the integrating process. The operating reserve increases the efficiency and reliability of the hybrid renewable energy system. Three renewable energy sources are used to feed a residential building near the shore with electricity. Wind, wave and solar energies are used in this study because of the variability in the factors affecting the energy production process. This variability makes the power system more reliable due to the availability of energy at any time because of the different nature of energy production from the three proposed sources. A microcontroller is designed to combine the three sources together with the possibility of determining the operating reserve for each of the three sources. This controller based on the Buck-Boost converter technology. It reduces the fluctuations in the output voltage of each source and integrates them together. It operates through 4 scenarios depending on surrounding weather conditions. The controller shows high efficiency reached about 99.5% in adjusting the voltage to be connected to the battery bank or the inverter to feed AC loads. It takes only 0.18 s to reach the desired voltage. In addition to the high accuracy in determining the operating reserve resulting from feeding a residential building for 10 continuous hours during the winter.

Modifications of probabilistic models of states evolution for reliability analysis of district heating systems

The analysis and synthesis of reliability of energy systems, particularly district heating systems (DHS), is based on probabilistic modeling of different system states and events connecting these states (usually, these are failures and restoration of system components). The paper deals with the problem of modeling the probabilities of DHS states based on a Markov random process under conditions that can be characteristic for actual systems: joint and dependent failures of several components. For this purpose, it probabilistic models of the evolution of events in DHS taking into account non-ordinary events and dependent between them are developed. The methodology is based on the theory of Markov random processes and the basic laws of probability theory. The formation principles of developed models are illustrated by the state graphs. Numerical studies were carried out, the results of which allows determine some properties and application limits of developed models.

Review on solar thermal energy storage technologies and their geometrical configurations

Because of the unstable and intermittent nature of solar energy availability, a thermal energy storage system is required to integrate with the collectors to store thermal energy and retrieve it whenever it is required. Thermal energy storage not only eliminates the discrepancy between energy supply and demand but also increases the performance and reliability of energy systems and plays a crucial role in energy conservation. Under this paper, different thermal energy storage methods, heat transfer enhancement techniques, storage materials, heat transfer fluids, and geometrical configurations are discussed. A comparative assessment of various thermal energy storage methods is also presented. Sensible heat storage involves storing thermal energy within the storage medium by increasing temperature without undergoing any phase transformation, whereas latent heat storage involves storing thermal energy within the material during the transition phase. Combined thermal energy storage is the novel approach to store thermal energy by combining both sensible and latent storage. Based on the literature review, it was found that most of the researchers carried out their work on sensible and latent storage systems with the different storage media and heat transfer fluids. Limited work on a combined sensible-latent heat thermal energy storage system with different storage materials and heat transfer fluids was carried out so far. Further, combined sensible and latent heat storage systems are reported to have a promising approach, as it reduces the cost and increases the energy storage with a stabilized outflow of temperature from the system. The studies discussed and presented in this paper may be helpful to carry out further research in this area.

Reliability evaluation of stand-alone hybrid photovoltaic energy system for rural healthcare centre

This paper presents two methods for evaluation of reliability indices of stand-alone hybrid photovoltaic (PV) energy system. Markov model and frequency-duration (F-D) reliability techniques have been used for evaluation of reliability indices. Hybrid energy system is design and evaluated reliability indices for its configurations (Diesel only, PV/Battery and PV/Diesel/Battery). The system reliability is based on the system failure rate, interruption duration, unavailability, loss of load probability (LOLP), expected energy not supplied (EENS) mean downtime (MDT) indices, which are computed and compared different energy generation system configurations. This paper also presented hybrid energy system reliability analysis is based on monthly solar radiation and load demand data. It is observed that hybrid energy system failure rate, interruption duration, system unavailability, EENS, MDT and LOLP are least as compared to other configuration. The results show that hybrid PV/Battery/Diesel system is more efficient and reliable system as compared to other configurations. This research work will be useful for policymakers and system designers to determine optimal system in remote areas before installation.

Reliability-aware fixed priority energy management with shared resources in real-time system

In this paper, we focus on preemptive rate monotonic scheduling and comprehensively consider energy consumption and system reliability about scheduling periodic tasks with shared resources. Firstly, a static scheme for fixed priority periodic tasks with shared resources is proposed, which executes with a uniform speed and ignores the system reliability. Secondly, the problem of energy consumption and system reliability for scheduling fixed priority periodic tasks with shared resources is proved to be NP-hard and a maximum execution time first (MF) algorithm is proposed. Finally, a dynamic scheme for fixed priority periodic tasks with shared resources (DA) is proposed. The DA algorithm exploits the dynamic slack time to save energy while preserving the system reliability. The experimental results show that the DA algorithm saves about 19.28% energy compared with the MF algorithm.

Synthetic evaluation of integrated energy system based on AHP- fuzzy comprehensive assessment method

Integrated energy system (IES) is an essential ingredient of energy reform. The construction of IES can promote the coupling utilization of multiple energy sources, and improve the reliability and flexibility of energy system. Based on amounts of literature study and experts’ recommendations, 9 first- class indexes, 13 second-class indexes and 11 third-class indexes are confirmed to assess the integrated energy system from three dimensions of technology, economy, and environmental protection. Analytic Hierarchy Process (AHP) and fuzzy comprehensive assessment method are adopted to assess the overall quality of chosen integrated energy system. An industrial park is chosen to be an example and examine the evaluation condition of IES.

An Intelligent Fault Diagnosis Method for Open-Circuit Faults in Power-Electronics Energy Conversion System

Applying the fault diagnosis techniques to power electronic equipments is beneficial to improve the stability and reliability of renewable energy system, because power electronic equipments are a key component of renewable energy system that largely defines their performance. This paper presents a novel intelligent fault diagnosis method for a three-phase power-electronics energy conversion system based on knowledge-based and data-driven methods. Firstly, the three-phase AC currents of the power-electronics energy conversion system are collected and used to analyze. Secondly, the feature transformation, a knowledge-based method, is utilized to preprocess the fault data. After feature transformation, the slopes of current trajectories (transformed features) are not affected by different loads. And then random forests algorithms (RFs), a data-driven method, are adopted to train the fault diagnosis classifier with the processed fault data. Finally, the proposed method is implemented online on an actual three-phase PWM rectifier platform. The results show that the proposed fault diagnosis method can successfully detect and locate the open-circuit faults in IGBTs of the three-phase PWM rectifier. In addition, the proposed method is suitable for most of three-phase power-electronics energy conversion systems.

Concept of Integrity, Reliability and Safety of Energy and Transport Systems for Cold Climate Regions

The concepts of providing the integrity, reliability and safety of the energy and transport systems in the Arctic zone are considered. The inadmissibility of using the concept of acceptable, or tolerable, risk to ensure the operational safety of potentially hazardous facilities used in extreme environment has been validated by the history and reasons of risk analysis reviewing. The new concept for transport and energy systems operating in cold climates has been proposed to include in the security concept flexible information monitoring and control systems that take into account the state of environment, the engineering system and the operator himself. The promptness of implementation of the new concept of renewable development is dictated by the modern transitional state of society from thoughtless consumption of resources to the minimization of environmental damage and the inadmissibility of human casualties, called Industry 5.0.

Exploiting wind-solar resource complementarity to reduce energy storage need

Resource complementarity carries significant benefit to the power grid due to its smoothing effect on variable renewable resource output. In this paper, we analyse literature data to understand the role of wind-solar complementarity in future energy systems by evaluating its impact on variable renewable energy penetration, corresponding curtailment, energy storage requirement and system reliability. Results show that wind-solar complementarity significantly increases grid penetration compared to stand-alone wind/solar systems without the need of energy storage. However, as capacity increases, the capability of complementarity to increase grid penetration approaches its limit due to the reduced matching of output to the load profile and pursuant increase in excess generation. Thus, achieving very high penetration requires appropriately designed energy storage and curtailment. Yet, even at higher grid penetration, complementarity carries significant multidimensional benefits to the power system. The most important observation was the achievement of very high grid penetration at reduced energy storage and balancing requirements compared to stand-alone systems. Researchers reported that using the same energy storage capacity, wind-solar complementarity led to significantly higher penetration of up to 20% of annual demand compared to stand-alone systems. In addition, by coupling to curtailment as an enabler, and related dispatch flexibility that comes with storage application, lower balancing capacity need was reported at higher penetration. Wind-solar complementarity was also found to reduce ramping need while contributing to improved system adequacy. Complementarity from other dispatchable renewable resources further reduces storage need and curtailment and improve system reliability, whereas power grid integration and relative cost changes allow for further optimisation while transitioning to 100% renewable energy.

Research on Equipment Optimization Configuration Method of Distributed Integrated Energy System Considering Reliability

In order to meet the requirements of economy and reliability, based on the traditional optimization method of equipment allocation only aiming at the optimization of economy, this paper selects two points of integrated demand response and distributed integrated energy system reliability evaluation to participate in the construction of DIES equipment optimization configuration model.

Improving reliability and safety of airborne wind energy systems

AbstractAirborne wind energy systems use tethered flying devices to harvest wind energy beyond the height range accessible to tower‐based wind turbines. Current commercial prototypes have reached power ratings of up to several hundred kilowatts, and companies are aiming at long‐term operation in relevant environments. As consequence, system reliability, operational robustness, and safety have become crucially important aspects of system development. In this study, we analyze the reliability and safety of a 100‐kW technology development platform with the objective of achieving continuous automatic operation. We first outline the different components of the kite power system and its operational modes. In the next step, we identify failure modes, their causes, and effects by means of failure mode and effects analysis (FMEA) and fault tree analysis (FTA). Potentially hazardous situations and mechanisms which can render the system nonoperational are identified, and mitigation measures are proposed. We find that the majority of these measures can be performed by a failure detection, isolation, and recovery (FDIR) system for which we present a hierarchical architecture adapted from space industry.

Mathematical Principles for Predicting Reliability Control Parameters of Pipe Armature for Transport Energy Systems

When assessing the reliability of transport energy systems, such calculation methods and sources of information about changes in the performance of its elements are required, which would allow predicting behavior, including pipefittings in various operating conditions. The question of the mathematical apparatus application and involvement of already known methods for assessing the quality and efficiency of transport energy systems is of particular importance for the science of reliability. These systems and their structural elements, including pipefittings, cannot be isolated from the influence of the environment and the processes that occur in themselves in the case of residual effects that accelerate wear and reduce their initial characteristics

Design, optimisation and reliability allocation for energy systems based on equipment function and operating capacity

Designers of energy systems often face challenges in balancing the trade-off between cost and reliability. In literature, several papers have presented mathematical models for optimizing the reliability and cost of energy systems. However, the previous models only addressed reliability implicitly, i.e., based on availability and maintenance planning. Others focused on allocation of reliability based on individual equipment requirements via non-linear models that require high computational effort. This work proposes a novel mixed-integer linear programming (MILP) model that combines the use of both input-output (I-O) modelling and linearized parallel system reliability expressions. The proposed MILP model can optimize the design and reliability of energy systems based on equipment function and operating capacity. The model allocates equipment with sufficient reliability to meet system functional requirements and determines the required capacity. A simple pedagogical example is presented in this work to illustrate the features of proposed MILP model. The MILP model is then applied to a polygeneration case study consisting of two scenarios. In the first scenario, the polygeneration system was optimized based on specified reliability requirements. The technologies chosen for Scenario 1 were the CHP module, reverse osmosis unit and vapour compression chiller. The total annualized cost (TAC) for Scenario 1 was 53.3 US$ million/year. In the second scenario, the minimum reliability level for heat production was increased. The corresponding results indicated that an additional auxiliary boiler must be operated to meet the new requirements. The resulting TAC for the Scenario 2 was 5.3% higher than in the first scenario.