Multi-objective planning framework for stochastic and controllable distributed energy resources

The amount of distributed energy resources (DER) in the grid is continually increasing, and the potential benefits and drawbacks are becoming clearer. However, there is still a lack of clarity in how these multiple effects interact and which trade-offs should be made in the integration of new DER. There is a clear need for appropriate DER planning tools in the current market environment, in which both DER operators and distribution system operators (DSOs) may have multiple, often conflicting objectives and where uncertainty remains present as to which targets can be reached with a high amount of DER in the grid. A novel multi-objective planning framework is presented for the integration of stochastic and controllable DER in the distribution grid. A case study that illustrates the proposed framework is presented. Active DER management in terms of curtailment as well as dispatch of units is studied using the proposed multi-objective approach. Additionally, the extent to which active DER can be used as an alternative for grid reinforcements is analysed. The results show that the proposed multi-objective approach permits a better evaluation of the potential of active DER to support system operation.     

A review on distributed energy resources and MicroGrid

The distributed energy resources (DER) comprise several technologies, such as diesel engines, micro turbines, fuel cells, photovoltaic, small wind turbines, etc. The coordinated operation and control of DER together with controllable loads and storage devices, such as flywheels, energy capacitors and batteries are central to the concept of MicroGrid (MG). MG can operate interconnected to the main distribution grid, or in an islanded mode. This paper reviews the researches and studies on MG technology. The operation of MG and the MG in the market environment are also described in the paper.     

A practical eco-environmental distribution network planning model including fuel cells and non-renewable distributed energy resources

This paper presents a long-term dynamic multi-objective planning model for distribution network expansion along with distributed energy options. The proposed model optimizes two objectives, namely costs and emissions and determines the optimal schemes of sizing, placement and specially the dynamics (i.e., timing) of investments on distributed generation units and network reinforcements over the planning period. An efficient two-stage heuristic method is proposed to solve the formulated planning problem. The effectiveness of the proposed model is demonstrated by applying it to a distribution network and comparing the simulation results with other methods and models.     

Design for distributed energy resources

The blackout experiences have demonstrated the vulnerability of the interconnected electric power system to grid failure caused by natural disasters and unexpected phenomena. Changes in customer needs, additional stress due to liberalized electricity markets, and a high degree of dependency of today's society on sophisticated technological services also intensify the burden on traditional electric systems and demand for a more reliable and resilient power delivery infrastructure. This paper discusses the design of a restructured electric distribution network that employs a large number of small distributed energy resources (DER) units, which can improve the level of system reliability and provide service differentiations.     

Optimal distributed energy resources planning in a competitive electricity market: Multiobjective optimization and probabilistic design

This paper presents a probabilistic multiobjective framework for optimal distributed energy resources (DERs) planning in the distribution electricity networks. The proposed model is from the distribution company (DISCO) viewpoint. The projected formulation is based on nonlinear programming (NLP) computation. The proposed design attempts to achieve a trade-off between minimizing the monetary cost and minimizing the emission of pollutants in presence of the electrical load as well as electricity market prices uncertainties. The monetary cost objective function consists of distributed generation (DG) investment and operation cost, payment toward loss compensation as well as payment for purchased power from the network. A hybrid fuzzy C-mean/Monte-Carlo simulation (FCM/MCS) model is used for scenario based modeling of the electricity prices and a combined roulette-wheel/Monte-Carlo simulation (RW/MCS) model is used for generation of the load scenarios. The proposed planning model considers six different types of DERs including wind turbine, photovoltaic, fuel cell, micro turbine, gas turbine and diesel engine. In order to demonstrate the performance of the proposed methodology, it is applied to a primary distribution network and using a fuzzified decision making approach, the best compromised solution among the Pareto optimal solutions is found.     

Recent trends in power management strategies for optimal operation of distributed energy resources in microgrids: A comprehensive review

The current era in sustainable development is focused on the rapid integration of renewable energy sources driven by a wide range of socio-economic objectives. Due to the inherent property of time-varying weather conditions, the intermittent sources, that is, Solar PV and Wind Energy, are considered as variable energy resources. The uncertainty and variability problem of these sources has brought many complications to distributed network operators to operate and control the complex or multi-microgrids with limited fast-ramping resources in order to maintain the power system flexibility. It led many researchers to find an alternative strategy since the conventional approaches are no longer adequate to handle the economic implications of operational decision making. At first, the brief review of various deterministic and probabilistic approaches, stochastic programming and robust optimisation strategies to address the uncertainty of variable energy resources are discussed. Furthermore, in the energy management point of view, the optimal scheduling problem of distributed sources of the microgrid is considered, and a brief review of optimisation models, advanced control strategies and demand response strategies to maximise economic benefits of microgrids are also elaborately presented. Finally, the multiagent-based distributed and decentralised control strategies for seamless integration of distributed generator units are reviewed under various configurations of the power grid along with communication network topologies.     

Optimal planning of distributed generation systems in distribution system: A review

This paper attempts to present the state of art of research work carried out on the optimal planning of distributed generation (DG) systems under different aspects. There are number of important issues to be considered while carrying out studies related to the planning and operational aspects of DG. The planning of the electric system with the presence of DG requires the definition of several factors, such as: the best technology to be used, the number and the capacity of the units, the best location, the type of network connection, etc. The impact of DG in system operating characteristics, such as electric losses, voltage profile, stability and reliability needs to be appropriately evaluated. For that reason, the use of an optimization method capable of indicating the best solution for a given distribution network can be very useful for the system planning engineer, when dealing with the increase of DG penetration that is happening nowadays. The selection of the best places for installation and the preferable size of the DG units in large distribution systems is a complex combinatorial optimization problem.This paper aims at providing a review of the relevant aspects related to DG and its impact that DG might have on the operation of distributed networks. This paper covers the review of basics of DG, DG definition, current status of DG technologies, potential advantages and disadvantages, review for optimal placement of DG systems, optimizations techniques/methodologies used in optimal planning of DG in distribution systems. An attempt has been made to judge that which methodologies/techniques are suitable for optimal placement of DG systems based on the available literature and detail comparison(s) of each one.     

A state-of-the-art review of the sustainability and energy efficiency of buildings in Saudi Arabia

Sustainable buildings have an important role in achieving sustainable development by improving energy utilization and environmental performance. Buildings are considered as the biggest single contributor to world energy consumption and greenhouse gas emissions. In Saudi Arabia, the significance of the building sector can be described on the basis of per capita electricity consumption, per capita carbon dioxide emissions, and the increasing number of buildings because of economic and population growth. Therefore, the country should consider establishing energy-efficient buildings to promote sustainable development. Efforts in developing energy-efficient technologies should increase for the national energy policy. This article comprehensively describes the current challenges and opportunities of energy consumption and various energy conservation options that are viable for the Saudi building sector. Current policy efforts for improving energy efficiency in Saudi buildings have been analyzed to enhance the sustainable development in the country. The study reveals that the energy conservation policy of the country has fairly improved in the past decades. However, the country has to focus on this area and perform urgent measures to adopt energy-efficient technologies in the building sector.     

An updated review of energy storage systems: Classification and applications in distributed generation power systems incorporating renewable energy resources

The demand of electric energy is increasing globally, and the fact remains that the major share of this energy is still being produced from the traditional generation technologies. However, the recent trends, for obvious reasons of environmental concerns, are indicating a paradigm shift towards distributed generation (DG) incorporating renewable energy resources (RERs). But there are associated challenges with high penetration of RERs as these resources are unpredictable and stochastic in nature, and as a result, it becomes difficult to provide immediate response to demand variations. This is where energy storage systems (ESSs) come to the rescue, and they not only can compensate the stochastic nature and sudden deficiencies of RERs but can also enhance the grid stability, reliability, and efficiency by providing services in power quality, bridging power, and energy management. This paper provides an extensive review of different ESSs, which have been in use and also the ones that are currently in developing stage, describing their working principles and giving a comparative analysis of important features and technical as well as economic characteristics. The wide range of storage technologies, with each ESS being different in terms of the scale of power, response time, energy/power density, discharge duration, and cost coupled with the complex characteristics matrices, makes it difficult to select a particular ESS for a specific application. The comparative analysis presented in this paper helps in this regard and provides a clear picture of the suitability of ESSs for different power system applications, categorized appropriately. The paper also brings out the associated challenges and suggests the future research directions.     

含可响应分布式电源的智慧能源配网多目标优化调度

分布式电源增加了配电网的灵活性,但同时也给配网调度带来一定挑战。文章针对含有可响应分布式电源的配网多目标优化调度进行研究。首先分析了居民智慧能源的特征以及居民用户、分布式电源、运行商三者的关系;然后考虑了分布式电源的不确定性,建立了风机和光伏的出力模型,从经济性、环保和配网可靠性角度建立了居民智慧能源配网多目标调度优化模型;针对配网负荷多样化的特点,提出了负荷因数模型,计及到多目标优化模型中;最后利用决策算法求解该模型,并在IEEE33节点系统中进行仿真,说明了所提模型和算法的有效性。     

A literature review on integration of distributed energy resources in the perspective of control,protection and stability of microgrid

The concept of integration of distributed energy resources for formation of microgrid will be most significant in near future. The latest research and development in the field of microgrid as a promising power system through a comprehensive literature review is presented in this paper. It shows a broad overview on the worldwide research trend on microgrid which is most significant topic at present. This literature survey reveals that integration of distributed energy resources, operation, control, power quality issues and stability of microgrid system should be explored to implement microgrid successfully in real power scenario.     

Lignocellulosic biomass pyrolysis mechanism: A state-of-the-art review

The past decades have seen increasing interest in developing pyrolysis pathways to produce biofuels and bio-based chemicals from lignocellulosic biomass. Pyrolysis is a key stage in other thermochemical conversion processes, such as combustion and gasification. Understanding the reaction mechanisms of biomass pyrolysis will facilitate the process optimization and reactor design of commercial-scale biorefineries. However, the multiscale complexity of the biomass structures and reactions involved in pyrolysis make it challenging to elucidate the mechanism. This article provides a broad review of the state-of-art biomass pyrolysis research. Considering the complexity of the biomass structure, the pyrolysis characteristics of its three major individual components (cellulose, hemicellulose and lignin) are discussed in detail. Recently developed experimental technologies, such as Py-GC–MS/FID, TG-MS/TG-FTIR, in situ spectroscopy, 2D-PCIS, isotopic labeling method, in situ EPR and PIMS have been employed for biomass pyrolysis research, including online monitoring of the evolution of key intermediate products and the qualitative and quantitative measurement of the pyrolysis products. Based on experimental results, many macroscopic kinetic modeling methods with comprehensive mechanism schemes, such as the distributed activation energy model (DAEM), isoconversional method, detailed lumped kinetic model, kinetic Monte Carlo model, have been developed to simulate the mass loss behavior during biomass pyrolysis and to predict the resulting product distribution. Combined with molecular simulations of the elemental reaction routes, an in-depth understanding of the biomass pyrolysis mechanism may be obtained. Aiming to further improve the quality of pyrolysis products, the effects of various catalytic methods and feedstock pretreatment technologies on the pyrolysis behavior are also reviewed. At last, a brief conclusion for the challenge and perspectives of biomass pyrolysis is provided.     

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 nondominated 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.     

Trends in design of distributed energy systems using hydrogen as energy vector: A systematic literature review

Currently, a significant transformation for energy systems has emerged as a result of the trend to develop an energy framework without fossil fuel reliance, the concerns about climate change and air quality, and the need to provide electricity to around of 17% of world population who lacks the service. Accordingly, the deployment of power plants located close to end-users and including multiple energy sources and carriers, along with the growing share of renewable energies, have suggested changes in the energy sector. Despite their potential capabilities, the design of distributed energy systems (DES) is a complex problem due to the simultaneous goals and constraints that need to be considered, as well as to the high context dependence of this kind of projects. For these reasons, in this work a systematic literature review of DES including hydrogen as energy vector, was made analyzing 106 research papers published between the years 2000–2018, and extracted from Scopus^® and Web of Science databases. The aim was to identify how hydrogen is employed (technologies, uses) and the criteria that are evaluated (economic, technical, social and environmental) when these systems are designed, planned and/or operated. The results constitute a baseline information covering the type of technologies, equipment sizes and hydrogen applications, that could be valuable for the preliminary stages of research or project planning of DES involving hydrogen. Furthermore, other factors have also been identified, such as the focus on techno-economic issues, and the lack of considering socio/political aspects and the uncertainty about input data like weather conditions, energy prices and demands. Additionally, a more integrated approach is needed including all the hydrogen supply chain stages and project stakeholders, to tackle issues like safety of the energy systems that could produce consumer rejections.     

Multi-objective optimization for the operation of distributed energy systems considering economic and environmental aspects

Along with the continuing global warming, the environmental constraints are expected to play more and more important role in the operation of distributed energy resource (DER) systems, besides the economic objective. In this study, a multi-objective optimization model is developed to analyze the optimal operating strategy of a DER system while combining the minimization of energy cost with the minimization of environmental impact which is assessed in terms of CO₂ emissions. The trade-off curve is obtained by using the compromise programming method. As an illustrative example, the DER system installed in an eco-campus in Japan has been selected for case study. The distributed technologies under consideration include photovoltaics (PV), fuel cell and gas engine for providing electrical and thermal demands. The obtained results demonstrate that increasing the satisfaction degree of economic objective leads to increased CO₂ emissions. The operation of the DER system is more sensitive when environmental objective is paid more attention. Moreover, according to the sensitivity analysis, the consideration of electricity buy-back, carbon tax, as well as fuel switching to biogas, has more or less effect on the operation of DER systems.     

Virtual power plant and system integration of distributed energy resources

A concept is presented along with the overarching structure of the virtual power plant (VPP), the primary vehicle for delivering cost efficient integration of distributed energy resources (DER) into the existing power systems. The growing pressure, primarily driven by environmental concerns, for generating more electricity from renewables and improving energy efficiency have promoted the application of DER into electricity systems. So far, DER have been used to displace energy from conventional generating plants but not to displace their capacity as they are not visible to system operators. If this continues, this will lead to problematic over-capacity issues and under-utilisation of the assets, reduce overall system efficiency and eventually increase the electricity cost that needs to be paid by society. The concept of VPP was developed to enhance the visibility and control of DER to system operators and other market actors by providing an appropriate interface between these system components. The technical and commercial functionality facilitated through the VPP are described and concludes with case studies demonstrating the benefit of aggregation (VPP concept) and the use of the optimal power flow algorithm to characterise VPP     

Employing cost sharing to motivate the efficient implementation of distributed energy resources

We consider the design of cost-sharing policies to motivate electricity distribution utilities to manage the costs of distributed energy resource (DER) projects. The optimal share of realized cost savings (s) that is awarded to the utility takes a relatively simple form in certain settings. More generally, s can vary with the prevailing environment in subtle and sometimes counterintuitive ways. For instance, s may increase as cost savings become less onerous for the utility to secure. Gains from affording the utility a choice among cost-sharing policies typically are minimal.     

Multi-objective optimization of a stand-alone hybrid renewable energy system by using evolutionary algorithms: A review

Hybrid renewable energy system has been introduced as a green and reliable power system for remote areas. There is a steady increase in usage of hybrid renewable energy units and consequently optimization problem solving for this system is a necessity. In recent years, researchers are interested in using multi-objective optimization methods for this issue. Therefore, in the present study, an overview of applied multi-objective methods by using evolutionary algorithms for hybrid renewable energy systems was proposed to help the present and future research works. The result shows that there are a few studies about optimization of many objects in a hybrid system by these algorithms and the most popular applied methods are genetic algorithm and particle swarm optimization.     

Evaluating potential renewable energy resources in Poultney,Vermont: A GIS-based approach to supporting rural community energy planning

The current electricity infrastructure in the United States relies on a centralized distribution network that carries a heavy carbon footprint and is susceptible to disruption and failure. Rural communities are more susceptible to longer term interruption and should strive towards a local distributed energy model. This transition will require municipalities to engage with and seek input from community stakeholders. This paper describes a possible model for supporting rural community energy projects using a Geographic Information System (GIS), which was used to develop an inventory of energy resource potential in a rural Vermont town for biomass, wind, and solar technologies.     

Uncertainties in the design and operation of distributed energy resources: The case of micro-CHP systems

Large-scale diffusion of distributed energy resources (DERs) will have a profound impact on electricity infrastructure functioning: it will bring radical changes to the traditional model of generation and supply as well as to the business model of the energy industry. DERs comprise distributed power generators, distributed energy storages and controllable loads. There are, however, many uncertainties that influence the design and operation of DERs. This paper clarifies these uncertainties by proposing and applying a comprehensive framework for uncertainty analysis. We thereby adopt an integrated approach that considers not only the technical, but also the economic and institutional uncertainties. A delineation of the work is a focus on residential DERs and on micro-CHP systems specifically. After the proposed framework for uncertainty analysis is explained the uncertainties pertaining to the design and operation of residential DERs and micro-CHP systems are identified. In a case study system a selection of the uncertainties are quantitatively analysed. The case study system consists of a household that intelligently applies a micro-CHP unit in conjunction with energy storages and that interacts with its energy supplier. With a sensitivity analysis of the system model the salient impacts of the uncertainties on system behaviour and performance are enunciated.