Hybrid Distributed Energy System Research Articles

Flexible Operation of Hybrid Distributed Energy System Based on Reliability Redundancy

This paper establishes a reliable-economic power sharing scheme of distributed energy system (DES) consists of Li-ion storage battery and photovoltaic (PV) source connected to the utility grid through a distribution feeder. The system is intended to supply a vehicle charging station that requires dense energy production for efficient and short time charging process. Therefore, the issue of battery state-of-charge (SOC) optimal scheduling and power routing among the sources are considered as a technical-economic problem from system dynamic reliability point of view. In the developed optimization framework, the required energy reserve, the optimal SOC scheduling, and the impact of the station on the utility grid are considered and investigated. A new PSO based optimization is proposed to optimize the power sharing of the sources using reliability based optimal power flow scheduling. The proposed methodology quantifies the reliability redundancy of the system to reliably dispatch the power between the sources. The reliability redundancy concept is proposed as a tool to dynamically schedule the battery SOC and updates the power dispatching among the sources in order to: (1) establish a flexible reserve margin, (2) increase the overall number of battery charging/ discharging cycles, (3) economically dispatch the power, and (4) provide an indirect grid service by decreasing the impact of the charging station on the utility grid. The results show that the system reliability is maintained and the number of accumulated cycles is increased by 134 cycles. Furthermore, the maximum imported grid power is decrease from 40.0 kW to 28.3 kW.

Energy, Environmental and Economic Performance of an Urban Community Hybrid Distributed Energy System

Energy systems face great challenges from both the supply and demand sides. Strong efforts have been devoted to investigate technological solutions aiming at overcoming the problems of fossil fuel depletion and the environmental issues due to the carbon emissions. Hybrid (activated by both renewables and fossil fuels) distributed energy systems can be considered a very effective and promising technology to replace traditional centralized energy systems. As a most peculiar characteristic, they reduce the use of fossil sources and transmission and distribution losses along the main power grid and contribute to electric peak shaving and partial-loads losses reduction. As a direct consequence, the transition from centralized towards hybrid decentralized energy systems leads to a new role for citizens, shifting from a passive energy consumer to active prosumers able to produce energy and distribute energy. Such a complex system needs to be carefully modelled to account for the energy interactions with prosumers, local microgrids and main grids. Thus, the aim of this paper is to investigate the performance of a hybrid distributed energy system serving an urban community and modelled within the framework of agent-based theory. The model is of general validity and estimates (i) the layout of the links along which electricity is distributed among agents in the local microgrid, (ii) electricity exchanged among agents and (iii) electricity exported to the main power grid or imported from it. A scenario analysis has been conducted at varying the distance of connection among prosumers, the installed capacity in the area and the usage of links. The distributed energy system has been compared to a centralized energy system in which the electricity requests of the urban community are satisfied by taking electricity from the main grid. The comparison analysis is carried out from an energy, environmental and economic point of view by evaluating the primary energy saving, avoided carbon dioxide emissions and the simple payback period indices.

Stochastic optimal integration of decentralized heat pumps in a smart thermal and electric micro-grid

Heat pumps represent a link between different energy vectors and their application in thermal and electrical grids can improve the overall operational flexibility of the system. In this work, the optimal integration of electrically driven heat pumps within a hybrid distributed energy system is investigated. A multi-objective stochastic optimization methodology is proposed to evaluate the integrated optimal sizing and operation of the energy systems under uncertainties in climate, space occupancy, energy loads, and fuel costs. A case study is considered, namely a University campus, and two different configurations, with and without heat pumps, are compared. Both configurations include a cogeneration system, photovoltaic and solar thermal panels, and a wind turbine. The results show how the integration of heat pumps can reduce the operational cost of the system, increase the renewables share, provide a more robust design of the system, and moderate the risk of the investment. Indeed, the configuration with heat pumps entails a 50% higher expected value of the energy savings, a 28% increase of the renewable energy production, and higher energy savings in the worst-case scenario (13% vs. 5%).

Optimization of AC / DC Hybrid Distributed Energy System with Power Electronic Transformer

This paper presents a new method of optimizing the distributed energy of AC/DC hybrid microgrids with power electronic transformer. Firstly, the steady state model of power electronic transformer in normal operation mode is proposed. Subsequently, for the AC/DC hybrid system with power electronic transformer, optimizing the scheduling model in order to achieve the full disposition of distributed energy in AC/DC hybrid system and economic optimization. Ultimately, with the case to verify the AC/DC power system model with power electronic transformer, the results show that: as the application of power electronic transformer in AC/DC hybrid system, the power transfer between the AC network and the DC network is controlled by the power regulation function of the power electronic transformer, which can effectively realize the full disposition of distributed generation. In addition, through the rational distribution power generation application, the operating costs of the system is reduced, which can achieve the economic operation of hybrid AC/DC system.

Three-phase seven-level SFO PWM inverter with high gain voltage multiplier for hybrid distributed energy systems

ABSTRACT– In this paper, seven-level cascaded asymmetrical H bridge inverter of reduced DC source with reduced switches is developed. Effort has been made to involve the renewable energy sources such as PV and the PEM fuel cell to take part in the energy harnessing process. A high gain P/O SL Luo Relift circuit is incorporated to boost and stabilise the distributed energy source voltages which produce a dual DC link for the developed modified inverter. The enhancement of fundamental voltage at lower modulation indices is realised using the modulation strategy of switching frequency optimal pulse width modulation of variable frequency which enables balanced switching actions, reduced switching losses and minimal THD for the developed inverter. Simulation model developed using Matlab/Simulink is presented to validate the performance of high gain P/O SL Luo Relift three-phase asymmetrical cascaded H-bridge seven-level inverter and to indicate the effectiveness of the proposed modulation strategy for the inverter. The obtained FFT spectral analysis for the three-phase multi-level inverter output voltage is well below the IEEE harmonic limits.

Natural Gas Improves Economic Feasibility of Hybrid Distributed Energy Systems

Facing concerns over climate change, energy security, and local air pollution, state governments have moved increasingly over the past few decades to “decarbonize, decentralize, and diversify” the electricity‐generation sector.

Multi-objective optimization of a hybrid distributed energy system using NSGA-II algorithm

In this paper, a multi-objective optimization model is established for the investment plan and operation management of a hybrid distributed energy system. Considering both economic and environmental benefits, the overall annual cost and emissions of CO2 equivalents are selected as the objective functions to be minimized. In addition, relevant constraints are included to guarantee that the optimized system is reliable to satisfy the energy demands. To solve the optimization model, the non-dominated sorting generic algorithm II (NSGA-II) is employed to derive a set of non-dominated Pareto solutions. The diversity of Pareto solutions is conserved by a crowding distance operator, and the best compromised Pareto solution is determined based on the fuzzy set theory. As an illustrative example, a hotel building is selected for study to verify the effectiveness of the optimization model and the solving algorithm. The results obtained from the numerical study indicate that the NSGA-II results in more diversified Pareto solutions and the fuzzy set theory picks out a better combination of device capacities with reasonable operating strategies.

Performance of U.S. hybrid distributed energy systems: Solar photovoltaic, battery and combined heat and power

Until recently, the relatively high levelized cost of electricity from solar photovoltaic (PV) technology limited deployment; however, recent cost reductions, combined with various financial incentives and innovative financing techniques, have made PV fully competitive with conventional sources in many American regions. In addition, the costs of electrical storage have also declined enough to make PV+battery systems potentially economically viable for a mass-scale off-grid low-emission transition. However, many regions in the U.S. (e.g. Northern areas) cannot have off-grid PV systems without prohibitively large battery systems. Small-scale combined heat and power (CHP) systems provide a potential solution for off-grid power backup of residential-scale PV+battery arrays, while also minimizing emissions from conventional sources. Thus, an opportunity is now available to maximize the use of solar energy and gain the improved efficiencies possible with CHPs to deploy PV+battery+CHP systems throughout the U.S. The aim of this study is to determine the technical viability of such systems by simulating PV+battery+CHP hybrid systems deployed in three representative regions in the U.S., using the Hybrid Optimization Model for Electric Renewable (HOMER) Pro Microgrid Analysis tool. The results show that the electricity generated by each component of the hybrid system can be coupled to fulfill the residential load demand. A sensitivity analysis of these hybrid off grid systems is carried out as a function capacity factor of both the PV and CHP units. The results show that conservatively sized systems are technically viable in any continental American climate and the details are discussed to provide guidance for both design and deployment of PV+battery+CHP hybrid systems to reduce consumer costs, while reducing energy- and electricity-related emissions.

Conceptual Design and Performance Analysis of SOFC/Micro Gas Turbine Hybrid Distributed Energy System

A numerical model has been developed for the performance analysis of solid oxide fuel cell (SOFC)/micro gas turbine (MGT) hybrid systems with prereforming of natural gas, in which a quasi two-dimensional model has been built up to simulate the cell electrochemical reaction, heat and mass transfer within tubular SOFC. The developed model can be used not only to predict the overall performance of the SOFC/MGT hybrid system but also to reveal the nonuniform temperature distribution within SOFC unit. The effects of turbine inlet temperature (TIT) and pressure ratio (PR) on the performance of the hybrid system have been investigated. The results show that selecting smaller TIT or PR value will lead to relative higher system efficiency and lower CO2 emission ratio; however, this will raise the risk to destroy SOFC beyond the limitation temperature of electrolyte.

Application and Analysis of Multi-Source Hybrid Distributed Energy System

Under the background of the global energy crisis and environmental issues, the efficient utilization of renewable energy as a kind of distributed energy resources, is paid more and more attention. However, the intermittency and unpredictability of the renewable energies limit its development and penetration. To deal with such a big challenge, the multi-source hybrid distributed energy system has been proposed. In this paper, the concept and characteristics of the multi-source hybrid distributed energy system are discussed. In addition, three main forms of the proposed innovation energy system are presents and compared.