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With more variable and uncertain patterns of electricity production and consumption, the need for flexibility in the power grid is becoming increasingly crucial. Industrial energy systems have the potential to contribute to providing such flexibility. Yet, there is still a lack of effective methods to quantify the magnitude of available flexibility from industrial energy systems that can be optimally dispatched to support the operation of the power grid. This paper studies the flexibility provision from steam systems, which exist in many energy-intensive industries. A generic model of industrial steam systems with turbine-generators is presented to reflect its interactions with the power grid. Then, a hybrid physics-based and data-driven approach is developed to approximate the boundaries of the flexibility domain at different operating conditions of the steam systems. The proposed flexibility quantification method is applied to two real industrial steam systems in a paper mill and a steel mill. The results show that the proposed method can approximate the flexibility boundaries under uncertainty steam states and reflect key factors that affect the boundaries. Also, it is shown that neglecting the limits imposed by the steam network leads to an overestimation of flexibility boundaries at certain operating conditions.

Understanding the future of multi-vector energy networks in the context of the transition to net zero and the energy trilemma (energy security, environmental impact and social cost) requires novel interdisciplinary approaches. A variety of challenges regarding systems, plant, physical infrastructure, sources and nature of uncertainties, technological in general and more specifically Information and Communication Technologies requirements, cyber security, big data analytics, innovative business models and markets, policy and societal changes, are critically important to ensure enhanced flexibility and higher resilience, as well as reduced costs of an integrated energy system. Integration of individual energy networks into multi-vector entities opens a number of opportunities, but also presents a number of challenges requiring interdisciplinary perspectives and solutions. Considering drivers like societal evolution, climate change and technology advances, this paper describes the most important aspects which have to be taken into account when designing, planning and operating future multi-vector energy networks. For this purpose, the issues addressing future architecture, infrastructure, interdependencies and interactions of energy network infrastructures are elaborated through a novel interdisciplinary perspective. Aspects related to optimal operation of multi-vector energy networks, implementation of novel technologies, jointly with new concepts and algorithms, are extensively discussed. The role of policy, markets and regulation in facilitating multi-vector energy networks is also reported. Last but not least, the aspects of risks and uncertainties, relevant for secure and optimal operation of future multi-vector energy networks are discussed.

The flexibility of energy systems in industrial plants will play an important role in helping bulk energy systems to deal with the various challenges brought by the net-zero carbon transition. The emerging digital twins, which have attracted rapidly increasing interests with some industrial applications, have the potential to facilitate the flexibility service provision from industrial energy systems. This potential is identified in this paper by matching the key features of digital twins and key issues and needs of providing flexibility services from industrial energy systems. The study presented in this paper preliminarily frames this new research area, with potential aspects and directions identified for future research.

Heat consumption management and effective temperature control strategies to meet heat demand in residential and office buildings have become an important aspect within energy management. A thermal dynamic model of a building is not only necessary to estimate the energy consumption under different operating conditions but also to design effective controllers. This paper presents a classical control approach for the indoor temperature regulation of buildings. State-space and transfer function models of house thermal behaviour are developed. These are obtained from first principles of heat transfer and their analogy with electrical systems. To capture a realistic behaviour of heat transfer, the proposed models consider parametric uncertainties. A frequency response-based approach is used to obtain a reduced order system that facilitates control system design. The models have been implemented in MATLAB/Simulink and a PI controller has been designed to maintain a comfortable indoor temperature in the building. Simulation results show that the controller effectively regulates temperature despite system disturbances. An energy saving of around 8% comparing the proposed controller to a traditional on/off controller is achieved.

Due to the increasing use of intermittent renewable generation, the power grid requires more flexible resources to balance supply and demand of electricity. Steam systems with turbine-generators, which are widely used in industries, can be operated flexibly to support the power grid. Yet, the available amount of flexibility of industrial steam systems is still not clearly quantified. This study presents the method to quantify electricity generation flexibility of a typical industrial steam system with a steam turbine-generator and process heat demands. The proposed method is introduced based on a real case of an integrated pulp and paper mill in Austria. An integrated mathematical model representing the combined electricity and steam system is developed to simulate the behaviour of the on-site energy system to quantify the potential flexibility provision. Flexibility is represented as the maximum upward and downward changes in the imported electricity from the public power grid. The results demonstrate that it is possible to aggregate the flexibility of the industrial facility as a lookup table. Also, the results reflect key factors that limit the flexibility at different operating points of the turbine-generator.

An increasing amount of low carbon technologies (LCT) such as solar photovoltaic, wind turbines and electric vehicles are being connected at medium and low voltage levels to electric power networks. To support high-level decision-making processes, the impacts of the LCTs on large numbers of different types (e.g., rural, suburban, urban) of distribution networks need to be fully understood and quantified. However, detailed modeling of large numbers of real-world networks is challenging for two reasons. First, access to real-world network data is limited, and second, cleaning the data requires a significant amount of time, even before modeling of the networks. This paper offers a novel systematic methodology aimed at identifying and quantifying the key electrical properties of medium-voltage level distribution networks. The methodology allows for characterizing different types (e.g., suburban, urban) of distribution networks and obtaining 'depth' dependent electrical properties of the models of the networks. Two key sets of (electrical) data were used for the study. The first set was installed capacities of distribution substations; and the second set was the conductor cross sections of the distribution lines. In the graph models of real-world networks, 'nodes' represent the distribution sub­stations, switchgears, busbars and consumers locations of the network. 'Links/edges' stand for the connections between the nodes through distribution lines. The results of the investigation of the real-world networks showed that, the substation capacities and the conductor cross sections could characterize the electrical properties of suburban and urban type distribution networks. The resulted probability density functions (PDF) of the electrical properties of suburban and urban type distribution networks have the potential to be directly used in generating realistic distribution network models.

The rapid development of intermittent renewable energy has caused emerging demand of flexibility for power systems. This paper quantifies operational flexibility from heating networks to enable the flexibility to participate in power system operation and markets. Concepts and physical meaning of the flexibility are discussed. Quasi-dynamic models are used to describe temperature propagation and transport delay in heating networks. Then two flexibility models are proposed to quantify the flexibility. Parameters of the flexibility models are coupled and determined by properties, operation strategies and baseline scenarios of the heating networks, as well as flexibility demand.

This paper presents the development of a mathematical model for the analysis of a ground source heat pump unit combined with photovoltaic-thermal panels and an earth energy storage system. Each sub-system was modelled in MATLAB and then merged to form an overall model of the energy system. The model was used to analyse the performance of the energy system using several test scenarios. The test scenarios saw input data for winter, spring, summer and autumn conditions across the periods of 24 hours. The model was used to simulate the system with differing refrigerants, PV/T module sizes and earth energy bank storage sizes. The heat pump shows a Coeffient of Performance of approximately 5.0 throughout the test scenarios. It was observed that the summer conditions produce an increase in the energy stored within the ground, whilst the winter operation shows a reduction due to increased thermal demand in the building and reduced solar irradiance. The model was shown to be simple and effective to capture the operational characteristics of the combined energy system.

Nowadays energy systems should be considered as integrated energy systems (IESs), where interactions between different energy vectors affect each other. A good performance of the whole system depends on the adequate behaviour of each individual element as undesired dynamics may propagate from one element to another. Due to the system complexity, a common practice is to employ steady-state models. Although such an approach is valuable as it provides significant insight into the system behaviour, it may hide\ud inherent coupling characteristics as the dynamics are not considered. To ensure the satisfactory performance of each component,dynamic models are not only required, but essential. With a truly dynamic model it is possible to clearly understand how the system is affected by different operating conditions, load variations and disturbances over time, which in turn enables an effective control\ud system design. Following this line, this paper presents a mathematical model, based on the mean value approach, of a reciprocating engine, which is used in combined heat and power units – key component of an IES. Although the system is non-linear, it is shown that a single-input single-output linear system can be derived and, thus, a frequency domain representation suitable for control system design can be obtained. The system has been developed in MATLAB/Simulink. Simulation results show that the designed linear controller is capable of ensuring a good performance of the reciprocating engine non-linear model.

An intraday, multi-objective, hierarchical and coordinated operation scheduling method for a multi-energy system (MES), which uses 15-min and 5-min scheduling intervals for different energy subsystems, is proposed. According to the characteristics of MES and the response time of energy conversion equipment, energy subsystems are dispatched on different dispatch intervals instead of unified dispatch intervals to dispatch energy subsystems. In a case study, the prediction error rate for a load is 5% and 2% when the dispatch interval is 15 min and 5 min, respectively; the prediction error rates for wind and solar energy output are 10% and 5%, respectively. Dispatching different subsystems with different intervals according to their characteristics reduces the impact of source and load uncertainties, which improves energy management. Multi-energy power dispatch considers exergy efficiency and the operation cost to improve the utilization energy efficiency. The Tchebycheff method, which considers the fuzzy entropy weight, is employed to balance the objectives between highest exergy efficiency and lowest operation cost. Numerical studies demonstrate that the operation cost of a multi-objective system is ¥500.8877 higher than that of a system with the objective of lowest operation cost. The exergy efficiency is increased by 3.94%, and the operation cost, which is reduced by ¥1706.9606, is 2.13% lower than that for the objective of highest exergy efficiency. Thus, the proposed method can balance the objectives between highest exergy efficiency and lowest operation cost. These findings provide a multi-dimensional dispatch scheme for dispatchers and highlight the development potential of an MES.

A heat exchanger is an essential component in district heating and cooling networks as it transfers thermal energy from energy centers to substations or customers. Thermal loads are typically supplied by regulating the temperature output of one stream of the heat exchanger and by modifying the mass flow rate of the other one. The availability of dynamic models suitable for control design can aid this process to be performed in an efficient way. In this paper, thermal dynamic models of counter-flow heat exchangers are developed. The models encapsulate key heat exchanger characteristics and consider the dynamic calculation of heat transfer coefficients—which includes the hydraulic behavior of the streams. Although heat exchangers are non-linear systems, linearized models are obtained to design simple yet effective and robust controllers in the frequency domain. These are validated in an advanced process simulation software. It is shown that a good temperature control performance in heat exchangers can be achieved for a wide range of operating conditions with a simple PI controller.

The growing use of renewable energy for generating electricity in those countries that have relied on gas-fired power stations to meet the bulk of their electricity demand is affecting gas consumption. In this Chapter, the impacts of a substantial capacity of wind generation on gas demand and consequently on the operation of gas networks are discussed.

Natural gas is a fossil fuel that was formed over millions of years from decomposing organic matter, which was subject to intense heat and pressure as successive layers of sand and rock were laid down. It is a mixture of hydrocarbon and non-hydrocarbon gases and is usually found in porous material underneath an impervious rock layer that prevents the gas from reaching the surface and escaping into the atmosphere. Conventional natural gas deposits are commonly found in association with oil reservoirs, with the gas either mixed with the oil (associated gas) or floating on top of it (non-associated gas).

European countries intend to reduce their emissions of Greenhouse Gases (GHG) up to 100% by 2050 compared to 1990 levels [1] and many other countries around the world have similar ambitions. Achieving these targets requires a substantial transformation of the energy systems in those countries that are reliant on fossil fuels to meet their energy needs. In particular, a reduction of the emissions from generating electricity and providing heat is expected to play a vital role in decarbonising energy systems worldwide.

The global drive towards a low carbon and sustainable energy supply system has led to an increase in research and development of low carbon alternatives to fossil based natural gas in the gas grids.

Thermal energy storage (TES) is a critical element in district heating systems and having a good understanding of its dynamic behaviour is necessary for effective energy management. TES supports heat sources in achieving a steady power supply. Achieving heat and electric load demand translates into a discharging and charging control problem in terms of stored heat energy. To this end, an accurate dynamic model is essential to design effective controllers to improve district heating performance. A thermal dynamic model of a water tank, together with controllers for energy charging and discharging processes, are presented in this paper. The model is based on a computational fluid dynamics approach. It is developed using thermal stratification. The hot or cold-water stream which vertically crosses each tank section is considered to describe heat transfer. This is a non-linear process represented by partial differential equations, which are linearised to obtain a suitable model for control system design. State-space and transfer function representations of the system are obtained. The non-linear model is implemented in MATLAB/Simulink to design a linear controller that regulates the mass flow rate of cold and hot water to fill or empty the tank’s energy according to performance specifications. The design of regulation and tracking controllers is explained. Simulation results show that a good performance in terms of the mass flow rate input demands is achieved with the proposed controllers.

Coupling between electricity systems and heating systems are becoming stronger, leading to more flexible and more complex interactions between these systems. The operation of integrated energy systems is greatly affected, especially when security is concerned. Steady-state analysis methods have been widely studied in recent research, which is far from enough when the slow thermal dynamics of heating networks are introduced. Therefore, an integrated quasi-dynamic model of integrated electricity and heating systems is developed. The model combines a heating network dynamic thermal model and the sequential steady-state models of electricity networks, coupling components, and heating network hydraulics. Based on this model, a simulation method is proposed and quasi-dynamic interactions between electricity systems and heating systems are quantified with the highlights of transport delay. Then the quasi-dynamic interactions were applied using security control to relieve congestion in electricity systems. Results show that both the transport delay and control strategies have significant influences on the quasi-dynamic interactions.

Integrated energy systems have become an area of interest as with growing energy demand globally, means of producing sustainable energy from flexible sources is key to meet future energy demands while keeping carbon emissions low. Hydrogen is a potential solution for providing flexibility in the future energy mix as it does not emit harmful gases when used as an energy source. In this paper, an integrated energy system including hydrogen as an energy vector and hydrogen storage is studied. The system is used to assess the behaviour of a hydrogen production and storage system under different renewable energy generation profiles. Two case studies are considered: a high renewable energy generation scenario and a low renewable energy generation scenario. These provide an understanding of how different levels of renewable penetration may affect the operation of an electrolyser and a fuel cell against an electricity import/export pricing regime. The mathematical model of the system under study is represented using the energy hub approach, with system optimisation through linear programming conducted via MATLAB to minimise the total operational cost. The work undertaken showcases the unique interactions the fuel cell has with the hydrogen storage system in terms of minimising grid electricity import and exporting stored hydrogen as electricity back to the grid when export prices are competitive.

Electricity, gas and heat network infrastructure are anticipated to facilitate the delivery of low carbon energy-carriers to decarbonise the future use of energy. Co-ordinated design and operation of these traditionally separate systems has the potential to bring forth numerous benefits to the energy sector. This paper presents a method developed for the simultaneous assessment of power flows in an interdependent electricity, gas and heat network system. A case study demonstrates an application of the method in a simple example. The advantages and disadvantages of the method and possible improvements are discussed.

Power-to-gas (PtG) converts electricity into hydrogen using the electrolysis process and uses the gas grid for the storage and transport of hydrogen. Hydrogen is injected into a gas network in a quantity and quality compatible with the gas safety regulations and thereby transported as a mixture of hydrogen and natural gas to demand centres. Once integrated into the electricity network, PtG systems can provide flexibility to the power system and absorb excess electricity from renewables to produce hydrogen. Injection of hydrogen into the gas network reduces gas volumes supplied from terminals. In order to investigate this concept, hydrogen electrolysers were included as a technology option within an operational optimisation model of the Great Britain (GB) combined gas and electricity network (CGEN). The model was used to determine the minimum cost of meeting the electricity and gas demand in a typical low and high electricity demand day in GB, in the presence of a significant capacity of wind generation. The value of employing power-to-gas systems in the gas and electricity supply system was investigated given different allowable levels of hydrogen injections. The results showed that producing hydrogen from electricity is capable of reducing wind curtailment in a high wind case and decreasing the overall cost of operating the GB gas and electricity network. The northern part of GB was identified as a suitable region to develop hydrogen electrolysis and injection facilities due to its vicinity to a significant capacity of wind generation, as well as the existence of gas network headroom capacity, which is expected to increase as a result of depletion of UK domestic gas resources.

The world has faced many natural and man-made disasters in the past few years, resulting in millions of people living in temporary camps across the globe. The energy and clean water needs of the relief operators in such emergency situations are primarily satisfied by diesel engine based generators and importing clean water to the site, in certain cases even for several years after the emergency. This approach results in problems such as low security of supply and high costs. Especially targeting the prolonged displacement situations, this paper presents an alternative solution – the Energy and Water Emergency Module. The proposed solution aims towards reducing the dependency on fossil fuel in prolonged emergency situations to a minimum while including local energy sources in the energy supply in a flexible and reliable way. The proposed module is built in a standard 20 ft container, and encompasses hybrid generation from solar, wind and biomass, with the possibility of using fossil sources too thanks to a dual fuel gas engine. The module can work both in grid connected and stand-alone mode. In addition the module includes a water purification unit to meet the water needs of displaced population. A demonstration unit was assembled at the Royal Institute of Technology in Stockholm during the year 2012 as a ‘concept proof’, and is now being tested and optimized for future deployment on the field. Preliminary testing and modelling shows that the proposed solution can reliably support emergency situations, and is already cost competitive with the current water and energy supply solutions for emergency situations.

Electricity systems and heating systems are more coupled than before. Interactions between systems become stronger and influence the performance of integrated energy systems greatly, especially when security is the concern. Steady state analysis methods were usually used in recent research of integrated electricity and heating systems, which are not able to accurately evaluate the interactions due to the slow dynamics of heating systems. This paper studies quasi-dynamic interactions between electricity systems and heating systems in normal operation. Interaction mechanism is analyzed, and transport delay is emphasized as an important feature of quasi-dynamic analysis in time dimension. The transport delay comes from the temperature propagation in heating networks and has significant influences on the quasi-dynamic interactions. The transport delay is quantified by quasi-dynamic models. Electricity systems and heating systems can influence each other when disturbances or actions occur. Control strategies also have great effects on the interactions.

Heat exchangers have a predominant role in heat transfer and constitute a key component of integrated energy systems. For instance, heating and cooling of fluids are the cornerstone of district heating systems. Thus, it is fundamental to understand the heat exchanger's dynamic behavior to design controllers which are robust to temperature variations. Following this line, this paper presents a dynamic model of a plate type heat exchanger. The model is obtained from first principles of energy transfer and fluid mechanics and describes the thermal behavior of fluids involved in the heat transfer process. Although the system is non-linear, system linearization is performed to obtain a frequency domain model suitable for control system design. The linear model is implemented in MATLAB to design a controller that regulates the cold stream outlet temperature. To assess its effectiveness, the controller is discretized, programmed in Python and implemented in Apros — an advanced process commercial simulation software. Simulation results show that the controller is capable of tracking reference temperatures while ensuring a good performance of the heat exchanger system.

Understanding the impact of injecting substitute fuels in the gas distribution network is important in the transition to a low carbon energy supply. A model was developed to identify the effects of decentralized, alternative fuel injections on the steady state operation of the low pressure gas network. A case study was designed to investigate the impact of hydrogen injection on the network compared to the normal operation. The results show the sensitivity of the network pressure distribution and the penetration of hydrogen to the amount and location of hydrogen injection. The study shows that the impact of hydrogen injection can be localized and managed by appropriately choosing the location of injection.

The carbon constrained design of energy supply infrastructure for new build schemes was investigated. This was considered as an optimization problem with the objective of finding the mix of on-site energy supply technologies that meet green house gas emissions targets at a minimum build cost to the developer. An integrated design tool was developed by combining a social cognitive optimisation solver, an infrastructure model and a set of analysis modules to provide the technical design, the evaluation of greenhouse gas emissions and the financial appraisal for the scheme. The integrated design tool was applied to a new build scheme in the UK with a 60% target reduction of regulated emissions. It was shown that the optimal design and corresponding cost was sensitive to the year of build completion and to the assumptions applied when determining the emissions intensity of the marginal central generators.

The domestic building sector accounts for 13% of the total UK greenhouse gas emissions. In order to curtail the emissions, implementation of higher insulation materials in building envelopes and integrated low carbon technologies within buildings becomes an alternative solution. Space heating energy demand in different types of domestic dwellings was modelled. Based on the occupancy pattern, the appliance and lighting schedule were obtained for calculating electrical demand. Two new build homes in Corby representing current and future dwellings were investigated to compare the difference of energy demand.

Industrial multi-energty-systemslike paper mills can provide flexibility services to existing ancillary servicemarkets or to the intra-day market. The paper presents a precise model of the CHP andsteam system of a paper mill. By means of this model the possible flexibility provision of theMES depending on the state of operation could be quantified as operational boundaries forupward and downward regulations. The result show that the steam system has more capacitiesfor downward regulations than upward regulations, which indicates different capabilities inproviding services like aFRR and mFRR to the market. In the next step the improvement of thesteam system by the installation of a steam accumulator will be investigated in terms of steam losses, network cost savings, and additional flexibility provision. While the technologies of steam systems and steam accumulators seem to be well proven,some tariffs for system utilisation and renewables contribution might yet be improved to bettersupport the participation of industrial (net) consumers of electricity in markets for electricalflexibility.In particular, provision of negative balancing energy will result in an increase of consumption and may cause additional consumption peaks. The operator of the industrial facility will becharged for additional peak consumption on monthly basis according to the Austrian Electricity SystemCharges Ordinance Section 5. Section 5 (9) regulates the system utilisation charge forbalancing service providers at a fairly reduced rate. Unfortunately, this reduced rate is only available for balancing service provision but does not apply for any schedules related to dayahaed or intraday markets. &nbsp

Industrial multi-energty-systems like paper mills can provide flexibility services to existing ancillary service markets or to the intra-day market. The paper presents a precise model of the CHP and steam system of a paper mill. By means of this model the possible flexibility provision of the MES depending on the state of operation could be quantified as operational boundaries for upward and downward regulations. The result show that the steam system has more capacities for downward regulations than upward regulations, which indicates different capabilities in providing services like aFRR and mFRR to the market. In the next step the improvement of the steam system by the installation of a steam accumulator will be investigated in terms of steam losses, network cost savings, and additional flexibility provision. While the technologies of steam systems and steam accumulators seem to be well proven, some tariffs for system utilisation and renewables contribution might yet be improved to better support the participation of industrial (net) consumers of electricity in markets for electrical flexibility. In particular, provision of negative balancing energy will result in an increase of consumption and may cause additional consumption peaks. The operator of the industrial facility will be charged for additional peak consumption on monthly basis according to the Austrian Electricity System Charges Ordinance Section 5. Section 5 (9) regulates the system utilisation charge for balancing service providers at a fairly reduced rate. Unfortunately, this reduced rate is only available for balancing service provision but does not apply for any schedules related to dayahaed or intraday markets.