Energy System Integration

An integrated energy system (IES) is responsible for aggregating various energy carriers, such as electricity, gas, heating, and cooling, with a focus on integrating these components to provide an efficient, low-carbon, and reliable energy supply. This paper aims to review the modeling methods, tools, and service modes of IES in China to evaluate opportunities for improving current practices. The models reviewed in this paper are classified as demand forecasting or energy system optimization models based on their modeling progress. Additionally, the main components involved in the IES modeling process are presented, and typical domestic tools utilized in the modeling processes are discussed. Finally, based on a review of several demonstration projects of IES, future development directions of IES are summarized as the integration of data-driven and engineering models, improvements in policies and mechanisms, the establishment of regional energy management centers, and the promotion of new energy equipment.

Guest Editorial: Situational awareness of integrated energy systems

The integrated energy system (IES) has gained rapid development in recent years for achieving higher energy efficiency. While the coupling between different kinds of energy carriers limits the operational flexibility of the integrated energy system, which contradicts with the increasing penetration of variable wind power. Fortunately, the integration of multiply-energy carries on the other hand provides customers with multiply options for fulfilling their energy demand. With the development of demand response (DR) technologies and energy net-work systems being increasingly flexible, it has become a realistic possibility for encouraging customers to adjust their energy demands in response to system operation conditions. Based upon the concept of energy hub which is a unit that provides the conversion and storage of different energy carriers, the flexibility of customers' energy demand is analyzed. Moreover, a two-step sequential dispatch framework is proposed for the incorporation of customers' demand response. In the proposed technique, the energy production constraints are relaxed via the demand response, which allows a better utilization of wind power and a reduction of the energy costs. An integrated energy system is developed to illustrate the effectiveness and benefits of the proposed technique.

The construction of integrated energy systems (IES) based on traditional energy systems that operate separately ensures higher efficiency and reliability of energy supply to consumers. IES are complex objects for design. The digital twin is a tool that allows one to integrate all the tools necessary for design in a single information space. Software tools that implement the digital twin of IES and are developed for their design require high flexibility in organizing calculations, which is due to the need to simulate a variety of equipment and involve a wide set of methods and mathematical models. Automating the construction of the computing subsystem is an effective solution to overcome the above difficulties. The article proposes a methodological approach to automating the construction of the computing subsystem of the digital twin of the IES. In accordance with the proposed approach, automated construction is performed on the basis of a software platform using modern metaprogramming tools. When building, the concept of Model-Driven Engineering is implemented and knowledge formalized in the form of ontologies is used. The article outlines the components of the proposed methodological approach to automating the construction of the computing subsystem of the digital twin of the IES, which include the following: principles of software platform development; software platform architecture; technique for automated construction of the digital twin computing subsystem; principles for ensuring the universality of software components. The digital twin obtained as a result of the practical application of the proposed methodological approach makes it possible to carry out computer and mathematical modeling of the IES in the virtual space, exploring various configurations of its construction. The implementation of modeling within the framework of the digital twin of IES makes it possible to implement flexible and efficient approaches to solving the problems of designing IES and to obtain design recommendations that can be implemented when building real IES. Keywords: methodological approach, digital twin, automation of computing, automation of programming, Model-Driven Engineering, metaprogramming, ontology, integrated energy system

This paper investigates the formulation of a general optimal energy flow (OEF) problem for integrated energy systems, paying particular attention to economy issues, i.e. production, distribution and utilization of hydrogen, as well as considering the impact of energy storage devices. Based on the concept of energy hubs, the optimal conversion and transmission of multiple energy sources and energy carriers, in particular natural gas, electricity, district heat and hydrogen, considering energy storage devices are discussed. A 3 energy-hub system with electricity, gas, heat and hydrogen production, distribution, demand and storage capabilities is used to illustrate some of the proposed concepts and analysis techniques. The results illustrate some of the advantages of combining different energy sources and carriers, particularly if hydrogen is considered as an integral part of the energy system, given its storage characteristics.

This paper presents possibilities to improve flexibility for integrated energy systems using optimization techniques in a capacity market. Long-term planning of the energy system is considered. Meeting the rapidly growing demand for electricity requires a complete integrated power system solution that must support consumers, stakeholders, and regional operations. The rapid change in the global economy is creating an energy transition towards the strategic future of power systems and energy markets - a new era of flexible grids, or the era of energy flexibility. The proposed capacity market model improves the competitiveness of the energy market system in accordance with the assessment and flexibility of electricity security. It also presents recommendations for evaluating the dimensions of the integrated energy system. All participants in the energy market can accept it as a useful tool to support decision-making and increase the sustainability of the energy system. The smart grids provide the reliability of power supply in an increasingly complex operating environment, achieved through observability, digitalization, and an increase in the number of measurements. Power supply and grid companies remain the main drivers of change.

The offshore micro integrated energy system is closely related to the production process of marine engineering and operates independently. It is difficult to save the cost and minimize CO2 emissions of the system while considering the effect of production process or the uncertainty of external environment. From the perspective of optimization planning for integrated energy system, this paper establishes an electricity-heat-CO2 coupling model of the offshore micro integrated energy system based on the concept of energy hub. Considering the effect of production process and external environment uncertainty, this paper develops a multi-objective stochastic planning model with the target of minimizing the total cost and CO2 emission, which is constrained by electricity and heat network balance. Then a multi-objective evolutionary algorithm is used to solve the model. As a result, the multi-objective optimization planning which combines cost and environmental protection is realized. Through the optimal planning for micro integrated energy systems of a group of offshore oil and gas platforms and an all-electric vessel, the effectiveness and feasibility of the proposed method are verified.

Under the “carbon peak and carbon neutrality” goal, the construction of an efficient, low-carbon, and economical energy supply system is of great significance for advancing a dual carbon strategy. In allusion to the integrated energy systems (IES) with hydrogen energy coupling, a hydrogen energy coupling IES low-carbon optimization operation strategy that took account of green certificate and ladder-type carbon joint trading and dual-incentive demand response was proposed in this paper. First, a hydrogen energy multiuse system composed of an electrolyzer, a hydrogen fuel cell, a methane reactor, and hydrogen energy storage was constructed to make full use of the low-carbon cleaning characteristics of hydrogen energy. Besides, a combined model of hydrogen mixed with natural gas was established to improve the utilization efficiency of hydrogen energy. Second, a dual-incentive demand response model including price incentives and subsidy incentives was constructed to fully use the ability to adjust demand-side resources. Next, in view of the carbon emission reduction mechanism of the green certificate, a green certificate and ladder-type carbon joint trading mechanism was constructed. In addition, a green certificate trading mechanism and a reward and punishment tiered carbon trading mechanism had been introduced separately in the IES optimization operation model to reduce carbon emissions of the system. The calculation simulation sets up different scenarios for comparative analysis. As shown by the results, the proposed model could effectively improve renewable energy consumption capacity and energy utilization efficiency. The effectiveness of hydrogen energy utilization, demand respond, and green certification carbon trading mechanism in improving system economy and low-carbon efficiency is verified.

Regarding the fact that the key characteristic variables of the coordinated operation of the cooling, heat, power, (natural) gas, and steam subsystems (CHPGSS) are not fully considered in the integrated energy system (IES), the day-ahead dynamic economic dispatch (DED) for IES considering these variables of CHPGSS is studied. In order to analyze the interactive influence of CHPGSS, a hybrid CHPGS energy flows model and calculation method are developed in this paper, coupling parts of CHPGSS are concerned with the core concept of energy hub (HB). Firstly, considering the well-known principle of temperature matched and cascade utilization based on the concept of thermal energy level, coupled modes of different energy qualities and energy levels are designed in HB. Secondly, based on HB, the model architecture of the energy station with CHPGSS is designed and the steady state operation model of CHPGSS is proposed, respectively. Then, based on time-of-use (TOU) power price power price mechanism, the influence of power storage, heat storage and cold storage on day-ahead DED of IES is analyzed. Finally, a 0-1 mixed integer nonlinear programming (MINLP) for day-ahead DED is established under different load structures with CHPGSS. The numerical results verify the validity of DED calculation and steady state operation analysis for IES. The models and methods are suitable for day-ahead DED analysis of IES containing CHPGSS, which can reasonably reflect the operation characteristics of the IES.

Integrated Energy Systems (IES) combine on-site power or distributed generation technologies with thermally activated technologies to provide cooling, heating, humidity control, energy storage and/or other process functions using thermal energy normally wasted in the production of electricity/power. IES produce electricity and byproduct thermal energy onsite, with the potential of converting 80 percent or more of the fuel into useable energy. IES have the potential to offer the nation the benefits of unprecedented energy efficiency gains, consumer choice and energy security. It may also dramatically reduce industrial and commercial building sector carbon and air pollutant emissions and increase source energy efficiency. Applications of distributed energy and Combined heat and power (CHP) in ''Commercial and Institutional Buildings'' have, however, been historically limited due to insufficient use of byproduct thermal energy, particularly during summer months when heating is at a minimum. In recent years, custom engineered systems have evolved incorporating potentially high-value services from Thermally Activated Technologies (TAT) like cooling and humidity control. Such TAT equipment can be integrated into a CHP system to utilize the byproduct heat output effectively to provide absorption cooling or desiccant humidity control for the building during these summer months. IES can therefore expand the potential thermal energy services and thereby extend the conventional CHP market into building sector applications that could not be economically served by CHP alone. Now more than ever, these combined cooling, heating and humidity control systems (IES) can potentially decrease carbon and air pollutant emissions, while improving source energy efficiency in the buildings sector. Even with these improvements over conventional CHP systems, IES face significant technological and economic hurdles. Of crucial importance to the success of IES is the ability to treat the heating, ventilation, air conditioning, water heating, lighting, and power systems loads as parts of an integrated system, serving the majority of these loads either directly or indirectly from the CHP output. The CHP Technology Roadmaps (Buildings and Industry) have focused research and development on a comprehensive integration approach: component integration, equipment integration, packaged and modular system development, system integration with the grid, and system integration with building and process loads. This marked change in technology research and development has led to the creation of a new acronym to better reflect the nature of development in this important area of energy efficiency: Integrated Energy Systems (IES). Throughout this report, the terms ''CHP'' and ''IES'' will sometimes be used interchangeably, with CHP generally reserved for the electricity and heat generating technology subsystem portion of an IES. The focus of this study is to examine the potential for IES in buildings when the system perspective is taken, and the IES is employed as a dynamic system, not just as conventional CHP. This effort is designed to determine market potential by analyzing IES performance on an hour-by-hour basis, examining the full range of building types, their loads and timing, and assessing how these loads can be technically and economically met by IES.

Handling the variability and uncertainty associated with integrating large capacities of renewable energy sources (RES) into the power grid is a challenge that is increasingly influencing the power systems operation. At the same time, the growing need for desalinated water in arid areas increases the importance of suitable energy sources for sustainable operation of water desalination plants. However, as power and water system operators have traditionally operated their systems in isolation, there is a lack of understanding of the interdependence and interactions between these two systems. This paper addresses this gap by proposing a risk-based two-stage stochastic co-optimization framework that coordinates the operation of a renewable-rich power system with the operation of grid-connected reverse-osmosis water desalination plants (RO-WDP) to minimize their combined operational costs while increasing the utilization of RES. From the power system operation standpoint, the RO-WDPs are considered as controllable demand, and the proposed model integrates the energy flexibility of RO-WDPs in the day-ahead power system operation. The proposed model considers the operational constraints of both power and water desalination systems, thus co-optimizing their operation without compromising the reliable supply of power and water to end-users, while taking into account the uncertainty of the demands and RES. Simulation results demonstrate the benefits of the proposed coordination on enhancing the power system efficiency, facilitating RES integration, and minimizing the combined operational costs of both systems while minimizing their operating risk using conditional value at risk.

The use of information and communication technology (ICT) and control systems in power systems has led to the creation of a concept called the smart grid. The development of this concept in power networks leads to optimal network control, optimal use of equipment, increased quality and reliability of power supply, facilitation of the integration of renewable energy sources (RES), optimal planning of the transmission and distribution systems, the development of the use of distributed generation (DG) and reduced system’s costs. However, in the past years, this concept has only been developed on the power grid and does not provide an accurate understanding of real energy systems. In real energy systems, different energy carriers and technologies interact, and a real energy system is a collection of these carriers and technologies. Therefore, the models presented for future sustainable energy systems should consider the integration of different energy infrastructure and the interaction of different energy carriers. In this regard, the concept of energy hub, in which the production, conversion, storage, and consumption of different energy carriers are considered in an intelligent framework, can provide a comprehensive model of future smart energy systems (SES). The main purpose of this chapter is to introduce the concept of smart energy hub (SEH). In this regard, an introduction to the concept of the smart grid, its definitions, features, and main challenges are presented. Finally, it discusses the framework of SEHs and their potential role in achieving a comprehensive model of SES in the future.

With the development of energy intelligent technology, integrated energy system (IES) has been widely used in the field of energy supply. While the IES significantly improves energy efficiency, the interaction between different energy systems may also bring multiple operational risks to the reliability of the energy supply, which necessitates an effective IES reliability assessment technique. Considering the dynamic characteristics of gas and heat systems can reduce energy losses during contingencies, which provides an instrument to improve the IES reliability. This paper for the first time contributes to a novel emergency dispatch formulation based on the IES dynamic optimal energy flow (OEF). A reliability assessment framework for IES is proposed by combining the IES dynamic OEF and Monte Carlo simulation (MCS). By taking into account the emergency dispatch formulation, the unreliability degree of IES can be mitigated. The IES dynamic OEF model is transformed into a linear programming problem under reasonable assumptions and simplifications due to its high degree of nonlinearity. Several novel reliability indices for heat system are proposed by incorporating the impacts of the IES dynamic characteristics on the reliability. The proposed model and method are validated by using an integrated gas, power and heat testing system.

Review and prospect of data-driven techniques for load forecasting in integrated energy systems

Owing to a higher energy supply efficiency and operational flexibility, integrated energy system (IES), including the power, heating, and gas systems, will be the primary form of energy supply in the future. However, with the increase of large-scale stochastic wind power integration, the IES planning will face a significant challenge as the traditional power system. Therefore, a probability-interval-based IES planning considering wind power integration is proposed in this article. First, a conditional value-at-risk (CVaR) based probability-interval method is developed to describe the uncertain wind power. Second, beside traditional facilities, electricity storage system is introduced to improve the flexibility of IES. Then, an expansion planning model for IES is established to minimize the total cost including investment, operation, CVaR cost, and unserved energy cost. Moreover, the piecewise linearization method is used to deal with the nonlinear integral terms of the proposed model to improve the solution efficiency. Finally, IEEE14-NGS14 and IEEE118-NGS40 systems are constructed and the planning model is solved by GAMS/CPLEX. The numerical results illustrate the correctness and effectiveness of the proposed method.