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Dynamic urban simulations often face three main challenges: 3D digital city generations, building archetype creations, and inclusions of urban microclimate impacts due to limited data and computing resources available. This study introduces a new approach for the 3D city generation by integrating publicly available data sets (OpenStreetMap and Microsoft footprints) and a free program (Google Earth). These data sets provide 2D building footprints, whereas Google Earth provides digital surface models of terrains and buildings. The building archetype library of non-geometrical properties was created based on building types and years of constructions in the form of shapefiles joined with the 3D city data through QGIS. The proposed workflow also includes the dynamic integration of urban microclimate (CityFFD) and building thermal/energy models (CityBEM). The dynamic simulations were achieved using weather station data as boundary conditions, including air temperature, solar radiation, and wind speed and direction, instead of typical meteorological year data. The transient microclimate results were validated using local weather station data, and dynamic energy simulation results were validated using measured power consumption data. The study provides a solution to dynamic urban building energy and microclimate modeling by publicly available data sets and tools. • 3D city model generation from Google Earth, Microsoft Footprints and OpenStreetMap. • Two-way dynamic integration of urban microclimate and building energy simulations. • Urban microclimate simulations were validated by local weather station data. • Urban building energy simulations were validated by measured power consumption data. • Urban microclimate contributes to > 20% difference of cooling load when considered. [ABSTRACT FROM AUTHOR]

High CO 2 purity products can be obtained from oxy-combustion power plants through a CO 2 CPU (compression and purification unit) based on phase separation method. To ensure that CPU (with double flash separators) can be operated under optimal conditions, this paper focuses on single variable analysis, multi-variable optimization, dynamic simulation and control system design for CPU in oxy-combustion power plants. It is found that optimal operating conditions are 30 bar, 30.42 °C, −24.64 °C, and −55 °C for multi-stage CO 2 compressor discharge pressure, flue gas temperature after compression, first flash separator temperature, and second flash separator temperature, respectively. The designed double temperature control structure based on a systematic top-down analysis and bottom-up design method is more suitable than the single temperature control structure under different operating scenarios (load change and flue gas composition ramp change). To bear operating disturbances, operating strategies like elevating temperature, manipulating valves and adjusting setpoints are proposed. Influence of SOx would be more obvious than that of NOx, whilst the k ij mixing parameters in Peng–Robinson property method affects little on process optimization and control system design. Comprehensive dynamic model with specified control system provides possibility to integrate CPU with full-train oxy-combustion power plants. [ABSTRACT FROM AUTHOR]

The newly established Shanghai crude oil futures market provides a natural experimental setting for studying the price cointegration and causal relationships between the Chinese domestic benchmark (Daqing) and international benchmarks (West Texas Intermediate and Brent). We find a significant change in the relationships between domestic and global oil prices before and after the launch of the Shanghai market. Moreover, using a Johansen cointegration test and a vector error correction model, we find long-term equilibrium and short-term relationships between the Shanghai market and global benchmarks. Shanghai crude oil futures prices also play a leading role in the price discovery of domestic crude oil spot prices, reflecting their dominant influence on the domestic market. The prices of the domestic crude oil market are thus becoming less influenced by global benchmarks but more influenced by the Shanghai crude oil futures market. The examined results of dynamic ARDL simulations model support the long run and short run relations between the Shanghai market and global benchmarks. The results also shows that the Shanghai crude oil futures market has response lags relative to those benchmarks. • Study the change of the price cointegration and causal relationships. • A natural experimental setting to study the price discovery in a closed economy. • Show an influential oil price change from the launch of the Shanghai market. • Study long-term and short-term relationships among Shanghai and different markets. • Dynamic ARDL simulation model is applied in the study. [ABSTRACT FROM AUTHOR]

Rising climate change and global warming issues highlight the potential role of research and development in the energy sector. By considering this critical role, the current study outlines the impact of energy innovation on carbon dioxide (CO 2) emissions for China. For this, the study produces empirical outputs by conducting a newly developed, dynamic autoregressive distributed lag simulation method. The study discloses robust findings that point out a mitigating effect of energy innovation on carbon dioxide emissions and validate the Environmental Kuznets Curve hypothesis. Empirical results highlight the significant role of energy innovation to decrease environmental pollution and inspire policymakers to increase the spending of the public budget on energy research development and demonstration as well as supporting innovative attempts and enterprises. On the other hand, empirical findings do not provide concrete evidence to support the pollution haven hypothesis in China. • Follows an EKC model structure extended with control variables. • Investigates the role of energy innovation in reducing pollution. • Performs a novel dynamic simulation method. • Obtains an inverted U-shaped relationship for the nexus income-pollution. • Confirms the significant role of innovation to decrease pollution. [ABSTRACT FROM AUTHOR]

Rising climate change and global warming issues highlight the potential role of research and development in the energy sector. By considering this critical role, the current study outlines the impact of energy innovation on carbon dioxide (CO 2) emissions for China. For this, the study produces empirical outputs by conducting a newly developed, dynamic autoregressive distributed lag simulation method. The study discloses robust findings that point out a mitigating effect of energy innovation on carbon dioxide emissions and validate the Environmental Kuznets Curve hypothesis. Empirical results highlight the significant role of energy innovation to decrease environmental pollution and inspire policymakers to increase the spending of the public budget on energy research development and demonstration as well as supporting innovative attempts and enterprises. On the other hand, empirical findings do not provide concrete evidence to support the pollution haven hypothesis in China. • Follows an EKC model structure extended with control variables. • Investigates the role of energy innovation in reducing pollution. • Performs a novel dynamic simulation method. • Obtains an inverted U-shaped relationship for the nexus income-pollution. • Confirms the significant role of innovation to decrease pollution. [ABSTRACT FROM AUTHOR]

Operational flexibility of thermal power plants is urgently needed to maintain balance between supply and demand in power grids with high penetration of intermittent renewable energy generation. A new coordinate control strategy based on dynamic simulations was proposed and evaluated in this study to enhance the operational flexibility of thermal power plants. The dynamic simulation model of the control object, a double-reheat coal-fired power plant, was developed and validated. The operational flexibility of the power plant was examined using the original control strategy, and results indicated that the reheat steam is seriously overheated when the power ramp rate increases. A new coordinated control strategy assisted by high-pressure extraction steam throttling was proposed to address the issue of reheat steam overtemperature and further increase the power ramp rate. The proposed control strategy obviously improved the control performance of thermal parameters, especially the reheat steam temperature. The change magnitude of reheat steam temperature decreases by 3.0 °C. Moreover, power ramp rate increases from 1.5% to 4.5% Pe0 min−1, which significantly enhances the operational flexibility. Furthermore, the proposed control strategy is compared with previous ones from the aspects of the flexibility and efficiency. • Dynamic models of a power plant coupled with control strategy are developed. • Reheat steam overtemperature is found to restrict the power ramp rate. • Coordinate control strategy assisted by steam extraction throttling is proposed. • The power ramp rate is increased from 1.5% to 4.5% Pe0 min−1. [ABSTRACT FROM AUTHOR]

This paper considers different cooling systems and investigates the most promising alternatives when solar energy is to be used to supply the cooling demand. All the systems are evaluated during a summer cooling season by the energetic and economic point of view by dynamic simulation for two different climates. For Milan (Cfb climate) the highest OSE (overall system efficiency) is reached by LiBr (lithium-bromide) double effect absorption chiller driven by parabolic through collector (0.53). In terms of the collecting surface area, the best systems for Milan feature 0.08 m2 MJ−1 per day both for electric system (mono-crystalline photovoltaic coupled to water cooled chiller) and thermal system (PTC (parabolic trough collectors) coupled to double effect water-LiBr absorption chiller). Southern latitudes like Trapani (Csa climate) allow a quite better performance for thermal solar cooling solutions. The NPV (net present worths) of electric solar cooling solutions are favorable with respect to the traditional solution and the DPV (discounted payback periods) are all lower than the period of economic analysis above all for water cooled chillers. Finally a sensitivity analysis of the specific investment cost (€ MJ−1 per day) is carried out regarding the investment cost of collectors, the solar ratio and the interest rate. [ABSTRACT FROM AUTHOR]

Abstract: The desiccant wheel is a key component of open desiccant air-conditioning systems. Development of a simplified method of assessing their dynamic performance would assist the growth of the industry. Important errors can occur when constant values of the effectiveness parameters are assumed in the effectiveness method. The present work investigates the feasibility of using different interpolation methods to predict the influence of the inlet states of the process and regeneration airflows on the global behaviour of a desiccant wheel. The procedures require a set of reference operating cases. One approach considers interpolation on a grid of known reference points, in a triangular arrangement, for each inlet state domain. The second approach is based on the radial basis function, where all points of the reference grid influence the estimated values. The reference cases are simulated by a validated numerical model. Comparison of the methods shows that the second approach requires fewer reference cases and so is more suitable for the development of a generic simplified tool that takes into account the influence of variable airflow rates and rotation speed on the performance. [Copyright &y& Elsevier]

Abstract: The paper investigates the integration of renewable energy sources and water systems, presenting a novel solar system producing simultaneously: electrical energy, thermal energy, cooling energy and domestic water. Such system is designed for small communities in European Mediterranean countries, rich in renewable sources and poor in fossil fuels and water resources. The polygeneration system under analysis includes PVT (photovoltaic/thermal solar collectors), a MED (multi-effect distillation) system for SW (seawater) desalination, a single-stage LiBr–H2O ACH (absorption chiller) and additional components, such as storage tanks, AHs (auxiliary heaters) and BOP (balance of plant) devices. The PVT produces simultaneously electrical energy and thermal energy. The electrical energy is delivered to the grid, whereas the thermal energy may be used for space heating and/or domestic HW (hot water) production. As an alternative, the solar thermal energy can be used to drive an ACH, producing CHW (chilled water) for space cooling. Finally, the solar energy, in combination with the thermal energy produced by an auxiliary biomass-fired heater, may be used by the MED system to convert SW into potable water. The system is dynamically simulated by means of a zero-dimensional transient simulation model. A thermo-economic analysis is also presented, aiming at determining the optimal values of the most important design variables. [Copyright &y& Elsevier]

Abstract: This paper presents a dynamic simulation model to predict the performance of an ASHPWH (air source heat pump water heater). The developed model is used to assess its performance in the Lebanese context. It is shown that for the four Lebanese climatic zones, the expected monthly values of the average COP (coefficient of performance) varies from 2.9 to 5, leading to high efficiencies compared with conventional electric water heaters. The energy savings and GHG (greenhouse gas) emissions reduction are investigated for each zone. Furthermore, it is recommended to use the ASHPWH during the period of highest daily ambient temperatures (noon or afternoon), assuming that the electricity tariff and hot water loads are constant. In addition, an optimal management model for the ASHPWH is developed and applied for a typical winter day of Beirut. Moreover, the developed dynamic model of ASHPWH is used to compare the performance of three similar systems that differ only with the condenser geometry, where results show that using mini-condenser geometries increase the COP (coefficient of performance) and consequently, more energy is saved as well as more GHG emissions are reduced. In addition, the condenser “surface compactness” is increased giving rise to an efficient compact heat exchanger. [Copyright &y& Elsevier]

Abstract: The share of renewable energies in electricity and heat supply besides the conventional energy resources gains more importance. Accordingly, the efficiency and flexibility of modern thermal power plants should be further improved. To design such a system, it is necessary to generate detailed computer models that can accurately predict the power plant behaviour during fast transients, part loads and start-up procedures. In this work, a dynamic simulation model for a subcritical three-pressure-stage HRSG (heat recovery steam generator) is built, employing the advanced processing simulation software Aspen Plus Dynamics®. The simulation results obtained from the HRSG model are validated towards the dynamic measurements during warm start-up procedure. The capability of processing simulation software used to estimate the dynamic behaviour of real HRSG is demonstrated. The HRSG model shows high accuracy at different part loads with a maximum relative error of about 5%. The good agreement suggests that the HRSG model is very reliable and is capable to predict the operational processes. [Copyright &y& Elsevier]

Abstract: The Ericsson engine is an external combustion engine suitable for the use of certain energy sources such as solar energy, biomass and waste gases at high temperature, and thus contributes to the fight against global warming. Its open cycle configuration considered in this study can achieve good performance in low power range, most particularly in micro-cogeneration applications. The dynamic model of this engine which is the purpose of this study, takes into account both the pressure losses and the variation of the thermophysical properties of the working fluid as a function of the temperature in the system. The coded models are implemented on a Matlab/Simulink platform where the start-up dynamics and performance simulations are conducted. The optimal settings of the expansion cylinder valves, as well as the characteristic parameters of the engine are thus determined. In this configuration the engine develops a power output of 1.72 kW and reacts well when subjected to a selected perturbation. [Copyright &y& Elsevier]

Abstract: The paper is focused on the dynamic simulation of a Photovoltaic/Thermal collector (PVT) integrated in a high-temperature Solar Heating and Cooling (SHC) system. The system is based on the following main components: concentrating parabolic PVT (photovoltaic thermal) collectors, a double-stage LiBr-H2O absorption chiller, storage tanks, auxiliary heaters, balance of plant devices. The PVT is made-up by a parabolic dish concentrator and a triple-junction receiver. The polygeneration system provides electricity, space heating and cooling and domestic hot water for a given building, whose simulation is also included in the model. In particular, PVT produces electric energy, which is in part consumed by the building loads (lights and equipments), in part by the system parasitic loads, whereas the eventual excess is sold to the public grid. Simultaneously, the PVT provides the heat required to drive the absorption chiller. The system was simulated by means of a zero-dimensional transient model, that allows the evaluation of temperature profiles and also heat/electrical energy flows for whatever period of the year. It is also possible to evaluate the overall energetic and economic performance on whatever time basis (day, week, month, year, etc.). The economic results show that the system under investigation can be profitable, if a proper funding policy is available. The paper also includes an extensive parametric analysis aiming at evaluating the set of design and operating parameters (solar field area, tank volumes, set point temperatures, etc.) that maximize the energetic and/or economic performance of the system. [Copyright &y& Elsevier]

Considering the steam generator startup process and its dynamic response to the stimulations applied in the downstream and upstream cycles is crucial for predicting the system performance. In the present work, a novel hybrid once–through and natural circulation Heat Recovery Steam Generator (HRSG) is numerically simulated to demonstrate how it may improve the performance of a power plant. Dynamic numerical simulation is carried out to show the advantages of hybrid HRSG over natural circulation type. The main focus is to reduce the steam generation startup period via a hybrid once-through and natural circulation HRSG. Results showed that the system reaches the steady-state condition after 60 min for the once-through section compared to the 180 min for the natural circulation section. In other words, the hybrid HRSG can reach 50% of its nominal capacity utilizing only the once-through section just 60 min after startup. After 120 min, the natural circulation section also comes fully online. Additionally, steady-state simulation results showed that in the hybrid HRSG, the drum wall thickness, drum diameter, and weight decreased by 54, 30, and 65% compared to the drum of a natural circulation type. • Performance of a hybrid OT-NC HRSG is studied using a numerical approach. • A combination of control volume approach and nodal model is used for the simulation. • HRSG startup and its dynamic response to up and downstream stimulations are studied. • Hybrid HRSG startup period is reduced up to 120 min compared to NC type. • In a hybrid HRSG, drum size and weight decrease significantly, compared to NC type. [ABSTRACT FROM AUTHOR]

The European Union introduced the concept of "Net Zero Energy Building" (NZEB) to promote competitive, sustainable, eco-friendly, and "decarbonised" cities. To these aims, mainly with reference to highly urbanized places, it is necessary to renovate existing buildings to achieve the NZEB target. Thus, this paper analyses the energy retrofit of an existing building considering two low enthalpy geothermal systems in the HVAC plants: the Ground-to-Air Heat eXchanger (GAHX) and the Ground Source Heat Pump (GSHP). These two plants are used in different retrofit strategies and compared from an energy, environmental and economic point of view. A dynamic simulation software based on EnergyPlus calculation engine is used. The results are very interesting and demonstrate how by using a low enthalpy geothermal plant, a very low value of primary energy requirement can be obtained (about 60 kWh/m2, i.e., −71% compared to the existing building, characterized by a gas boiler). Moreover, substantial savings on annual energy bills and reduction of CO 2 emissions are obtained. • Retrofit strategies of an existing building to obtain a NZEB are proposed. • Two low enthalpy geothermal energy systems are analysed (GAHX, GSHP). • A technical-economic evaluation is made by using dynamic energy simulation. • The performances of the GAHX and the GSHP are evaluated in order to obtain a NZEB. [ABSTRACT FROM AUTHOR]

Integrated collector storage units are typically affected by convective and radiative heat losses which significantly reduce their energy performance. To enhance solar collection and heat retention, innovative techniques and novel design of such units are being more and more developed. In this framework, this paper focuses on the design and optimization of a prototypal high-vacuum integrated collector storage solar water heater. The proposed unit allows for reaching high temperatures of the stored water and for reducing the temperature drop during non-collection periods. This goal is achieved by suppressing the convective heat losses into the system by keeping the pressure into the related enclosure below 0.01 Pa and by applying a special selective coating to the solar absorber surface to drastically reduce radiative losses as well. In this paper, details about the system design and the conducted experimental tests are reported. In addition, a new mathematical model able to assess the energy performance of the innovative prototype is presented. This tool, based on a detailed 3-D transient finite-difference thermal network, was validated against the gathered experimental data. By such a tool the optical properties of the adopted selective coating are optimized for maximizing the system thermal efficiency. Finally, with the twofold aim of showing the potentiality of the developed code, as well as the effectiveness of the presented innovative solar collector prototype, a comprehensive case study referred to three different European weather zone is presented. Promising results in terms of energy savings (0.73 MWh/y) and CO 2 emission reduction (149 kg CO2 /y) are achieved. • A prototypal high-vacuum Integrated Collector Storage Solar Water Heater is presented. • To cut thermal losses a high-vacuum level is achieved by a non-evaporable getter pump. • A 3D thermal model of the prototypal unit is developed and experimentally validated. • A case study analysis is conducted to show the potentials of the proposed collector. • The collector exhibits remarkable primary energy savings ranging from 33 to 62%. [ABSTRACT FROM AUTHOR]

The aircraft temperature control system (TCS) with multiple temperature zones can provide personalized thermal regulation for crews and passengers, and it also increases the nonlinearity and coupling of the system dynamic responses. For predicting the dynamic response of the TCS with multiple temperature zones and optimizing the control effect, this paper presents a general dynamic simulation model of the TCS. A flow network consisting of pressure nodes and throttling units is developed to describe the system architecture for arbitrary temperature zones, and has the capability to compute pressure and flowrate transients in the system. Based on the flow network, component level sub-models are developed, and a simulation framework is developed incorporating the PID control algorithm. The model predictions show good agreement with the pull-down test data under hot day condition, with average deviations of 0.55 °C, 0.83 °C, and 0.91 °C for the cockpit, cabin and mixing chamber temperatures, respectively. The dynamic performance of a TCS with multiple temperature zones are further investigated for typical cooling/heating conditions and an entire flight process. The results indicate that the present model can sufficiently acquire the dynamic characteristics of TCS that provide industrial sight towards full understanding and control design of the TCS. • A dynamic model for aircraft TCS with multiple temperature zones is proposed. • Pressure and flowrate transients in TCS are reflected by flow-network based method. • Model predictions show good agreements with pull-down test data. • TCS control effect is examined for cooling/heating conditions and an entire flight. • Diverse thermal comfort requirements increase fuel consumption and regulation time. [ABSTRACT FROM AUTHOR]

This paper presents an innovative Concentrating Glazing system to be adopted in smart building façades: The Concentrating Photovoltaic Glazing system (CoPVG). The device consists of a double-glazing panel integrating a series of concentrating lenses. A thin layer of PV cells is then placed at the lenses' focus. The peculiar lens design can produce, by using the Total Internal Reflection (TIR), a seasonal effect with more light entering the building at low incidence angles (i.e. in the winter months) and higher electricity production at high incidence angles (i.e. in the summer months). To investigate this device's performance, a suitable dynamic simulation tool has been developed in MATLAB environment. Furthermore, to investigate active (electric energy production) and passive (building insulation and solar gains variations) effects related to the building integrated devices, the developed CoPVG simulation tool is implemented in a building energy performance simulation one (DETECt). To show the potential of the innovative device, a case study relative to a multi-floor office building integrating the innovative CoPVG prototype is investigated. Conventional and semi-transparent PV windows are also investigated for comparative purposes. By using the novel façade system, interesting energy savings ranging from 30 to 60 % for the investigated weather zones can be obtained. • Novel building integrated concentrating photovoltaic glazing system. • Modelling and dynamic simulation of smart building facades. • Analysis of photovoltaic yield of concentrating and standard solar windows. • Analysis of passive effects of building integrated glazing systems. [ABSTRACT FROM AUTHOR]

Abstract: The discontinuous nature of the solar energy forces to study the dynamic behavior of solar plants to characterize their operations, to deepen their process understanding and to improve the performance and maintenance. The present paper focuses on the dynamic simulation and control of concentrating solar plants with the aim to define a reasonably simplified layout as well as to highlight the main issues to characterize the process dynamics of these energy systems and their related energy storages. Detailed first-principles mathematical models of key unit operations are developed, implemented, and integrated into commercial codes to improve the reliability of the plant dynamic simulation as well as the prevision accuracy. The case of Archimede concentrating solar power plant with the related two-tanks direct thermal energy storage technology is investigated. [Copyright &y& Elsevier]

Abstract: This paper studies dynamic behaviour and control design of a hydrogen membrane reforming (HMR) power cycle based on economic measures. The HMR power cycle is a novel pre-combustion capture power cycle for electrical power production which incurs less of an energy penalty than current post combustion technologies. However, the HMR power cycle consists of a novel reformer and complex heat integration. For this type of power cycle to be competitive, it is important to have a thorough understanding of the system dynamics including robust control design which secures reasonable rejection of all important disturbances and tracking of desired outputs like load and CO2 capture flow rates. First, a new dynamic model of the HMR power cycle aimed at control design is developed based on first principles. It is further validated against existing knowledge. Dynamic behaviour of the critical components as well as the whole plant is investigated based on the model. Then, control structures of the power cycle are designed by a systematic approach. To determine the control structures, an economic objective is chosen, the degrees of freedoms and constraints are found, and appropriate disturbances are assumed. To handle the constraints systematically, model predictive control (MPC) is used in some parts of the power cycle. Finally, the control structures with well-tuned MPC controllers, PI controllers and feedforward controllers are simulated and evaluated. [Copyright &y& Elsevier]

Abstract: High-temperature superconducting magnetic energy storage systems (HTS SMES) are an emerging technology with fast response and large power capacities which can address the challenges of growing power systems and ensure a reliable power supply. China Electric Power Research Institute (CEPRI) has developed a kJ-range, 20 kW SMES using two state of art HTS conductors, BSCCO and YBCO tapes. This SMES system is used to compensate a power drop and a fluctuation in order to damp low frequency oscillations to increase stability of a power system. This paper presents an optimized design of the SMES system to achieve a maximum energy capacity. A voltage source converter using IGBTs is built and can be used to control the power flow between the SMES system and external circuits. A control system using a digital signal processor (DSP) and micro-programmed control unit (MCU) is constructed. SVPWM pulse modulation is used as a control strategy. The whole system was experimentally tested for compensation of power fluctuation within milliseconds in a dynamic power system simulation laboratory. The result validates the design and control circuit, and more importantly, the application capability of SMES systems in a power grid. [Copyright &y& Elsevier]

Abstract: In this paper an integrated fuel cell/household model is developed in order to assess the capability of fuel cells to fulfil different tasks in the energy market. The dynamic properties of two stationary combined heat and power (CHP) fuel cell systems were determined experimentally and serve as a basis for the development of the model. Based on this model, the possible contributions of fuel cell systems to a decentralized supply structure are investigated. The results show that if more than 24 households with a fuel cell are interconnected, the fuel cells are able to cover 99.6% of the entire household electricity demand. Additionally, German wind energy feed-in compensation is modelled. Here the results show that the influence on the wind power feed-in is limited because only for a small number of days with wind power production above median level the virtual fuel cell power plant can compensate the wind power feed-in by reducing its output. Thirdly, the potential use of excess electrical capacity from larger fuel cell populations sold at an energy exchange is examined. Here the simulation results show that trading can generate contribution margins of between 140 and 200 Euros per year. Consequently, fuel cells could be significant at the energy exchange, if fuel cell investment costs decreased in the future. [Copyright &y& Elsevier]

Abstract: In this study, an entire simulation model is developed to investigate the influence of fast gas turbine start-up (within 20 min) on the dynamic behavior of a Benson heat recovery steam generator. The model includes a new high pressure feedwater control concept that considers a large number of live plant parameters and derivative functions. The advanced feedwater control circuit offers the possibility to operate the high pressure system in level mode (nature circulation) or Benson mode (once-through). Furthermore, it provides a rapid response and ensures a save operation to Benson HRSG (heat recovery steam generator) during the GT (gas turbine) abrupt transients and fast start-up procedures. A set of enhanced steam bypass control circuits are also implemented in the model. The developed HRSG model and its advanced control circuits are validated toward the design data at different part loads. The obtained results demonstrate very good physical agreement with relative error less than 3% and cite as evidence that the Benson model represents the real power plant. Finally, different fast start-up procedures (hot, warm, cold) are assessed with the validated Benson model, which provides adaptable operation demands to meet the gas turbine fast start-up requirements. [Copyright &y& Elsevier]

Abstract: A thermoeconomic analysis has been applied to the annual operation of a micro-cogeneration installation in a tertiary sector building combining the capabilities of dynamic simulation with the thermoeconomic analysis. The SenerTec’s DACHS micro-cogeneration unit is considered integrated in a heating and domestic hot water installation, meeting the electric and thermal loads of a residential building. A six minute-based exergy analysis has been implemented in the TRNSYS v.16 thermal simulation software, while the Life Cycle Analysis (LCA) has been developed to determine the cumulative exergy consumption of the different components of the plant. The thermoeconomic analysis of the micro-CHP installation is performed for its annual operation which includes the analysis of the entire system, considering the costs and exergy content of both flows and components. The relationship between the annual contribution to the costs of the components and the energy consumption has resulted equal to 34.2%. A combined production cost value has been defined and has been compared with the micro-CHP unit and the conventional production system, being 34.6 and 45.42 c€/kWhex respectively, underlying the opportunity that micro-CHP units provide in residential installations. [Copyright &y& Elsevier]

Abstract: With a view towards better efficiency in renewable energy utilisation, particularly solar energy, the authors study a long-term solar thermal energy storage based on water absorption by a lithium bromide aqueous solution. After a description of the process, the system dynamic simulation model is detailed and used to investigate the influence of certain parameters (heat exchanger size, solution flow rate, absorption percentage) and operating conditions (heat supply temperature to the building, crystallisation ratio, heat need) on the system performance (storage density, thermal efficiency, etc.). The analysis of simulations made for a low-consumption building in Chambéry shows that the solution flow rate is a critical parameter in the process performance. It also appears that crystallisation in the solution storage tank increases the storage density more than three times. The simulation results are used in the design of a prototype that is under experimentation for validation of the model. [Copyright &y& Elsevier]

Solar-aided coal-fired power generation is a hybrid technique to generate power with the coal and solar energy. The performance of solar-aided coal-fired power plant (SACFPP) with solar irradiance fluctuations received little attention in previous studies. Dynamic and exergy analysis models of SACFPP are developed to evaluate the SACFPP performance in transient processes caused by solar irradiance disturbances and the consequent system regulation. An SACFPP integrating the trough collector system (TCS) in parallel with HP2 and HP3 heaters of a 660 MW coal-fired power plant is simulated. Influences of solar irradiance and feedwater ratio to TCS disturbances on SACFPP performance are analyzed, including step cases and typical solar days. The solar-to-power exergy efficiency fluctuates sharply in the dynamic process. It increases from 32.62% to 57.25% and decreases to 28.1% when solar irradiance step decreases from 700 to 400 W m−2. Accumulations of additional power and exergy destruction are the highest in Autumn Equinox. Then, control strategies of feedwater flow to TCS are proposed and compared to obtain maximal solar-to-power exergy efficiency during transients. Results indicate that the feedwater flow to TCS should follow the solar irradiance decrease with a dynamic period of less than 200 s; otherwise, extra exergy destruction occurs. • Dynamic exergy analysis models of solar-aided coal-fired power plant are developed. • Exergy destructions are analyzed with solar irradiance disturbances in transients. • Solar-to-electricity efficiency is determined by solar irradiances and power loads. • Feedwater flow to TCS should be adapted rapidly to solar irradiance disturbances. [ABSTRACT FROM AUTHOR]

In order to solve the safety problem caused by the abnormal load shedding of the liquefied air energy storage (LAES) system during expansion process, the dynamic simulation model of the 500 kW expansion unit was established. The model is used to simulate normal shutdown and emergency shutdown of the unit, and the changes of parameters such as unit load, valve opening, and rotor speed during the expansion process are analyzed. By studying the influence of valve closing time and rotor time constant on rotor speed and rotor downtime when the unit is shut down due to accident, the value range of valve closing time and rotor time constant which can meet the safety requirements of the unit was proposed. The simulation results show that during the process of shutdown, the highest rotor speed increases first and then decreases with the increase of valve closing time when the rotor time constant remains unchanged, and the valve closing time when the highest speed reaches the maximum value is related to the rotor time constant. When the valve closing time remains unchanged, the highest rotor speed decreases gradually with the increase of the rotor time constant, but the downtime increases. The rotor time constant should be set not less than 7s, and the closing time of the control valve should not exceed 1.5s to ensure the safe operation of the expansion process of the liquefied air energy storage system. • A dynamic model of liquefied air energy storage expansion unit was established. • The influence of valve and rotor parameters when unit break down were obtained. • The range of valve and rotor parameters meeting safety requirements were proposed. [ABSTRACT FROM AUTHOR]

In order to achieve the targets of the EU climate protection strategy, the household sector with its overall high energy consumption offers great potential for efficiency improvements. Better insulated buildings and efficient heating and ventilation technologies can reduce the demand for energy regarding space heating and cooling. Efficiency improvements in domestic appliances can only be achieved with great effort. This paper presents an innovative system concept in which domestic appliances are thermally connected to the heating and ventilation system via the energiBUS, using a heat pump as the central heating and cooling device. The system benefits from the replacement of internal heating and cooling devices of the respective domestic appliances and the simultaneous utilization of both energy flows – warm and cold – of the heat pump. The system is analyzed by means of a detailed dynamic simulation model using MATLAB/Simulink®. The component models included are experimentally validated and have deviations of less than 5%. The results show that a reduction of 35 kWh/a in total energy consumption is achieved and the COP of the heat pump can be improved from 3.3 to 3.5. In this context, the integrated design of the system control still has potential for optimization. • Description of an integrated system concept for low-energy buildings. • Connecting domestic appliances with the heat pump and ventilating system. • Analysis of the system by means of a detailed dynamic simulation model. • The energiBUS system saves approximately 35 kWh/a. • The coefficient of performance increases from 3.3 to 3.5. [ABSTRACT FROM AUTHOR]

This paper proposes a novel approach in order to accurately calculate the savings due to heat metering. The approach is based on a detailed dynamic simulation of building-plant systems. The building is geometrically modelled in Google Sketchup and linked to the TRNSYS environment, including an extremely detailed model for the simulation of building thermo-physical behavior. All the models are validated using the data provided by the occupants. The model allows one to evaluate the yearly energy demand, energy supplied by radiators, heat gains, etc. A specific case study is developed for a residential building located in Naples (South Italy). The developed model is used to calculate the building energy demand for 3 scenarios: centralized heating system not equipped with heat metering; centralized heating system with thermostatic valves and not equipped with heat metering; centralized heating system with thermostatic valves and equipped with heat metering. Results show that in case of centralized heating systems equipped with thermostatic valves and heat metering devices, thermal energy savings up to 64% can be reached mainly when the system operates for many hours per day, leading to discounted pay back periods lower than 4 years. • Dynamic analysis of energy performance of building adopting thermostatic valves. • Dynamical analysis of heat metering devices for a residential building. • Dynamic analysis of building energy performance. • Thermostatic valves and heat metering devices are able to reduce by 64% building thermal energy demand. [ABSTRACT FROM AUTHOR]

Integrating a regenerative turbine (RT) is a significant modification to improve the Rankine cycle efficiency by reducing the superheat degree of extraction steam. This work evaluates the short-term operational flexibility of the modified cycle, emphasizing the evaluation of recuperative heater shutdown as a method to rapidly increase the power generation. A number of scenarios were modeled that included a shutdown of recuperative heaters, and the power change was observed. Results indicate that the utilization of an RT decreases the operational flexibility of the power plant with the high-pressure recuperative heater (HPH) shutdown. It shows that the adjusting time of total power generation increases by 492.9–550.6 s and the maximal output power increment reduces by 6.0–28.1 MW compared to that of the conventional Rankine cycle (CRC). Control strategies are proposed and evaluated to improve response performance and limit the deaerator (DTR) pressure. The results reveal that the adjusting time of the total power and maximum negative overshoot value could be reduced by 342.8 s and 7.79 MW, respectively, with a normal DTR pressure under the condition of No.3 and No.4 HPH shutdowns. • The dynamic model of a Rankine cycle with a regenerative turbine is developed. • The flexibility of the Rankine cycle declines with a regenerative turbine. • The power output performance could be improved with control strategies. • The deaerator pressure could be limited to the normal value with control strategies. [ABSTRACT FROM AUTHOR]

In this paper, an experimental analysis and validation of a simple reconfigurable photovoltaic (PV) array is carried out. An assessment of a new reconfiguration method based on fuzzy logic (FL) under partial shading conditions is introduced. Furthermore, a recursive least squares based irradiance estimator is proposed aiming to reduce the investment cost of the dynamic PV array. An experimental comparison with other estimators showed the high precision of the proposed estimator. The estimation error has decreased by an average of 10% compared to the first estimator (based on the PV current and voltage measurement) and by 4.28%compared to the second estimator(based on the PV current measurement). On the other hand, the results validated the FL Controller ability to switch to the appropriate configuration under prevailing shading conditions. The method was tested for a simple configuration, however it could be generalized for small-scale configurations as residential house (average power output equal to 5 kWh). To evaluate the performance of the FL method an extended simulation of dynamic PV array of 16 PV modules is also realized. The mismatch loss is mitigated by nearly 50% compared to fixed Total-Cross-Tied and 8% compared to basic Irradiance Equalization techniques. • Experimental assessment of a reconfigurable small-scale photovoltaic array is performed. • Reconfiguration method based on fuzzy logic under partial shading conditions is proposed. • A new irradiance estimator based on recursive least squares is proposed. • Real time comparison showed the high accuracy of the proposed estimator. • Energy loss in the experienced reconfigurable photovoltaic array is significantly reduced. [ABSTRACT FROM AUTHOR]

Abstract: A solar deep-freezing process has been designed. It aims at cooling down a cold box to about −20°C, using simple flat plate solar collectors operating at 70°C. This original process involves two cascaded thermochemical systems based on the BaCl2/ammonia reaction. Its working mode is discontinuous as it alternates between a regeneration mode during daytime and a cold production mode during nighttime. A global dynamic model involving the various system components allows the simulation of the process; it predicts the evolution of the components temperatures and the rates of chemical reactions of the system. It also allows the dimensioning of the system components to maintain a 500l cold box at −20°C during the 6 sunniest months of the year under typical Mediterranean weather conditions and provide over 80% of the total yearly cooling needs of this box. This requires a solar collector area of 5.8m2 and 39kg of reactive salt. The predicted coefficient of performance (COP) is about 0.1 over the year, and the net solar COP, taking into account the collector efficiencies, is 0.05. [Copyright &y& Elsevier]

This study is motivated by the insufficient studies on the dynamic simulation, operation control optimization, and operation strategies for small-scale old plants. In such small power plants, there is a need for cautions and stability during various troubleshoots. This study aims at developing a simulation model that accurately predicts the behavior of small-scale real plants under various part loads and troubleshoots. The actual operation of a 110-MW steam power-plant was modeled using Aspen Plus Dynamics, which employs a single-input single-output proportional integral (PI) controller. The controller tuning constants, K and IT, were optimized, and operation strategies for handling five troubleshoots are proposed. The simulation results are in good agreement toward the measured values, with a maximum relative error of 2%. The recommended operation strategies could prevent plant trip and return to steady state in a maximum of 5 min when two different halts are mimicked. Full-load thermal efficiencies of 94%, 97.9%, 92.6% were achieved when four burners were shutdown, high-pressure feedwater heaters tripped, and all the heaters tripped, respectively. The simulation presents the possibility of stabilizing the old power plants operation with maximum possible efficiency under various conditions. An updated operation and troubleshoot manual can be provided for various circumstances. • Comprehensive study of an old thermal power-plant dynamic simulation model. • Three real dynamic transient operations were realized. • The PI controller tuning constants, K and IT, were optimized. • Operation strategies for handling five troubleshoots are recommended. • Updated operation and troubleshoot manual can be provided for various conditions. [ABSTRACT FROM AUTHOR]

Liquefied natural gas has recently received much attention due to the tightened environmental regulations associated with sulfur oxide and nitrogen oxide. LNG is generally stored in liquid form below its saturation temperature of −162 °C. During the storage process at the floating storage regasification unit, LNG continuously evaporates, and it results in the pressure build-up inside the tank leading to potential hazards unless the pressure is controlled properly. In this study, the variation in the pressure and temperature inside the storage tank was estimated by conducting a dynamic simulation of the mathematical model of a non-equilibrium LNG tank. For this, different initial filling ratios (i.e., 10, 50, and 94 vol%) were applied to the modeling and its analysis. First, the model was divided into three zones to enhance its accuracy: vapor, upper and lower LNG zones. Then, two scenarios (i.e., "sealed tank mode" and "venting mode") were adopted for simulation. Finally, the evaporation rate of LNG was estimated based on its initial filling ratio. As a result, we could estimate the change of pressure and temperature accurately during the operation of the LNG storage and develop an operating strategy based on the different initial filling ratios. [Display omitted] • A non-equilibrium LNG tank model is developed for large scale LNG tank. • Three separate zones inside the LNG storage are considered for modeling. • Two scenarios are considered: sealed tank and vapor venting condition. • The pressure and temperature increase relatively fast at low filling ratio. [ABSTRACT FROM AUTHOR]

Pakistan has been confronting economic challenges for two decades due to many factors such as the electricity crisis, among others. It is therefore essential to identify such factors that may play a constructive role in economic growth. In doing so, this study investigates the determinants of economic growth in Pakistan from 1972 to 2018. The dynamic autoregressive distributed lag (ARDL) simulations approach is applied to analyze positive and negative changes in energy consumption, industrial growth, urbanization, and carbon emissions on economic growth in Pakistan. The frequency-domain causality (FDC) test is utilized to check long-, medium-, and short-run relationships. Our empirical evidence reveals that electricity consumption and industrial value-added have a short- and long-run impact on economic growth. However, carbon emissions and urbanization have positive effects on economic growth in the short run. Consequently, we conclude that energy consumption, industrial growth, urbanization, and CO 2 emissions positively impact economic growth in Pakistan. The FDC also confirms the long-, medium-, and short-run causality hypothesis. The study suggests a requirement to integrate better electricity generation and management with the planning of economic policies. The government is advised to invest more in renewable energy to protect the environment from degradation, ban the import of low-efficiency electrical appliances, and evaluate the refugee reception policy. • The study examines the determinants of economic growth in Pakistan from 1972 to 2018. • This study employs a newly developed, dynamic ARDL simulation model. • The study also applied the frequency-domain causality (FDC) test. • Empirical results show long and short-run significant impacts on economic growth. • However, the FDC evidence revealed the short, medium, and long-run relationship. [ABSTRACT FROM AUTHOR]

We introduced a 1-dimensional dynamic model to study the thermodynamic parameter evolution process of the recuperator in a S–CO 2 Brayton cycle, in which we considered the dependency between the S–CO 2 's physical properties of and its temperature/pressure as well as the distribution of the thermodynamic parameters along flow direction. We simulated the start-up process of the recuperator and calculated the changes of thermodynamic parameter fields with time. The thermodynamic parameters at the nodes or elements near hot end took the lead in changing and achieving a stable state. And the thermodynamic parameters such as heat transfer coefficient violently changed along flow direction, especially near the cold end. We calculated the dynamic response process of thermodynamic parameters in recuperator, when generation load ratio gradually decreased from 100% to 50%. It is found that there was an intersection between the hot/cold fluid temperature curves under different generation loads. And the temperature change ranges of cold and hot fluids at recuperator outlets are respectively 730.64–778.82 K and 386.52–384.79 K. The introduced 1-dimensional dynamic model of recuperator and the calculated results may lay foundations for the dynamic simulation and the control system design of the S–CO 2 Brayton cycle. [ABSTRACT FROM AUTHOR]

A gas flare is a safety device in oil, gas and petrochemical plants, but excessive flaring causes remarkable material and energy losses as well as environmental and economic problems. In the current study, the optimal start-up procedures for an olefin dynamic operation are presented. The flaring locations that have been identified showed that the most important flaring locations are compressor inlet suction and C2/C3 separation column overhead. The key parameter to reduce flaring in the olefin plant is the rapid start-up of compressors. For better performance of compressors, two alternative procedures have been suggested that can reduce flare amounts during start-up operation. The best start-up scenario showed 27% reduction in released off-specification gases as well as 16% reduction in CO 2 emission comparing to the existing amount. • A method for flaring reduction during olefin plants start-up was presented. • Two alternative start-up procedures introduced for the olefin plants. • Appropriate modifications were suggested to reduce flaring. • Economic analysis was performed for each start-up procedure. [ABSTRACT FROM AUTHOR]

The surface equipment design for a binary cycle geothermal power plant including facilities required for the power cycle and the complete reinjection process of two-phase geothermal fluid (H 2 O + non-condensable gases (NCGs)) in the Castelnuovo area of Larderello are modelled. The proposed scheme includes the configuration of closed-loop power plant, NCGs compression train and reinjection process at the wellhead. Steady-state and dynamic simulations are performed. The steady-state model is developed to find the correct operating solutions and conditions, while the dynamic model investigates the unsteady behaviour of the system. The study includes a sensitivity analysis of surface equipment design, demonstrating the effect of internal and external variables on the system performance, including power cycle, compression train and reinjection process. The maximum compressor power consumption (at 60 bar reinjection pressure) is 176 kW at 8% CO 2 mass fraction into the geothermal fluid. The unsteady system behaviour at startup and its response to step-changes of flow stream condition is assessed: it is found that the average response-time is about 20 min. Also, the system requires a drain pressure higher than the saturation level for effective reinjection. A new Antoine – based correlation for water-CO 2 mixture is proposed for geothermal applications. • For a 5 MW power plant, the CO 2 compressor train consumes up to 176 kW. • The friction loss for the downward flow in the reinjection well is about 7.5 mbar/m. • The start-up of the reinjection takes about 20 min achieving the steady-state. • The CO 2 -dependent saturation pressure of the drain is the reinjection process limit. • Previously dissolved CO 2 /H 2 S in water reduce the well capacity of receiving extra NCG. [ABSTRACT FROM AUTHOR]

To solve aerodynamic performance deterioration caused by dynamic stall, a large eddy simulation numerical calculation based on dynamic grid and sliding grid technology was conducted and the dynamic flow control mechanism of unsteady pulsed plasma was explored. The results showed that plasma aerodynamic actuators can effectively control the airfoil's dynamic stall, improve the mean and transient aerodynamic forces, and reduce the negative peak value of the pitch moment and hysteresis loop area. A negative pressure "bulge" appears in the plasma application areas, and the peak suction of the airfoil's upper surface obviously increases. Two unsteady control parameters, the pulsed frequency and duty cycle, significantly influence the flow control. When the dimensionless pulsed frequency is 1.5, plasma control improves, and when the duty cycle is 0.8, it is close to the aerodynamic benefits under the continuous working mode. In the deep stall state, plasma impels the flow separation position to obviously move backward, resisting large-scale dynamic stall vortices. The structure of the separation vortices is broken, dissipated, and reattached to the airfoil by the plasma, and the influence area of the vortices is reduced. In the light stall state, the plasma actuator easily controls the shear layer, inducing the transition of the airfoil's boundary layer and promoting the momentum mixing with the main flow. "Vortex clusters" near the airfoil's leading edge induced by plasma actuation play a role in the virtual aerodynamic shape. The harmonic oscillation of aerodynamic force/moment is caused by the nonlinear and strong coupling effect between dynamic vortex structures with different scales and frequencies and plasma aerodynamic actuation. The amplitude of low-order mode energy concentration is relatively large, which is mainly caused by the pitching motion. The high-order fluctuation energy concentration is caused by the evolution process of starting vortices and derived secondary vortices with different frequencies induced by plasma. • Large eddy simulation based on dynamic grid and sliding grid technology. • Enhancement of aerodynamic lift and efficiency by plasma actuation. • "Vortex clusters" near the airfoil's leading edge induced by plasma actuation. • Negative pressure "bulge" appears in the plasma application areas. • Strategy to solve aerodynamic performance deterioration caused by dynamic stall. [ABSTRACT FROM AUTHOR]

District heating and cooling (DHC) systems are considered cornerstones of a future heat and cold supply due to their ability to integrate renewable and waste heat sources as well as long and short-term storage technologies and their flexibility for integration of other infrastructures. Therefore, DHC systems may represent the central hub of an interlinked overall energy system. These options nevertheless lead to a more complex system if implemented as the number of technical components and potential interactions increase and as the energy demands on the network grow. The transportation of the heat supplied to the consumers through water flow involves both time and temperature-dependent changes based on the mass flow rates and the heat losses to the surrounding from the pipes. The dynamic properties of the consumers and the distribution pipes strongly influence the operation of the district heating systems. Dynamic modeling tools are required to cope with the increasing complexities and to optimize the operation of the DHC systems by using the knowledge of time delay in the heat transport, temperature distribution and flow characteristics. Nevertheless, it is computationally challenging to simulate large-scale DHC networks dynamically. One proposed method for improvement in this context is aggregation, which simplifies the topological complexities of the original network by reducing the number of pipe junctions (branches) and pipes. This paper focuses on the analysis and evaluation of the application of two aggregation methods, the Danish and the German method, in a dynamic modelling environment and comparing the aggregation to the monitoring data of a virtual district heating network with 146 consumers and an existing district heating network with 66 consumers. These evaluations are based on comparison of the simulation results of the aggregated network with fewer consumers than the original network in terms of accuracy, information loss and computational time. The results show that the CPU time in the simulation of this network can speed up approximately more than 95% by aggregating the network down to 3 consumers without significant information loss. We will highlight the current potentials and limitations of both aggregation methods in terms of integrating them in the planning, modelling and operation of DHC systems, including the 4th generation district heating systems. Image 1 • Workflow of translation of the district heating network from CAD to simulation software. • Evaluating the aggregation methods on an existing district heating network in Austria. • Performing dynamic simulation of the original and aggregated network in Modelica. • 95% computational time reduction in fully dynamic simulation by aggregation methods. • Discussion on the potentials and limitations of aggregation methods on 4th generation district heating networks. [ABSTRACT FROM AUTHOR]

An innovative adsorber plate heat exchanger (APHE), which is developed for application in adsorption heat pumps, chillers and thermal energy storage systems, is introduced. A test frame has been constructed as a representative segment of the introduced APHE for applying loose grains of AQSOA-Z02. Adsorption kinetic measurements have been carried out in a volumetric large-temperature-jump setup under typical operating conditions of adsorption processes. A transient 2-D model is developed for the tested sample inside the setup. The measured temporal uptake variations with time have been fed to the model, through which a micro-pore diffusion coefficient at infinite temperature of 2 E−4 [m2s−1 and an activation energy of 42.1 [kJ mol−1 have been estimated. A 3-D model is developed to simulate the combined heat and mass transfer inside the APHE and implemented in a commercial software. Comparing the obtained results with the literature values for an extruded aluminium adsorber heat exchanger coated with a 500 μm layer of the same adsorbent, the differential water uptake obtained after 300 s of adsorption (8.2 g/100 g) implies a sound enhancement of 310%. This result proves the great potential of the introduced APHE to remarkably enhance the performance of adsorption heat transformation appliances. • An innovate stainless steel adsorber plate heat exchanger (APHE) is introduced. • Representative APHE-segment is experimentally tested with AQSOA–Z02 loose grains. • 2-D and 3-D Simulations carried out on the representative segment and the APHE. • Diffusion coefficient at infinite temperature (D ∞) and (E a) are obtained. • Performance of the introduced APHE outreaches coated aluminium heat exchangers. [ABSTRACT FROM AUTHOR]

The waste heat recovery system (WHRS) is a critical part of the combined cooling, heating, and power (CCHP) system and can evidently improve its primary energy utilisation rate. However, few researchers have investigated the operation performance of the WHRS with the entire CCHP system to reveal its effects on the CCHP system efficiency. Therefore, dynamic simulation models of an entire CCHP system with a novel cascade WHRS named 'electricity-cooling cogeneration system (ECCS)' and a dual-effect absorption refrigeration system (DARS) are established in this study. The operation performances of the CCHP system–ECCS and CCHP system–DARS are compared based on dynamic simulations, thereby focusing on the effects of different WHRSs. In addition, the dynamic simulation results are compared with the results of operation optimisation and static simulation to reveal the applicability of the different methods. The optimisation and dynamic simulation results of the CCHP system operation agree well when the off-design performance is considered. Furthermore, the dynamic simulation results enable a more detailed analysis, thereby showing that the CCHP system–ECCS requires 0.29% less primary energy. Besides, under slow variations in load, the simulation results of the static and dynamic models have no evident difference, and the maximal error is only approximately 0.5%. • The simulation model of a CCHP with cascade waste heat recovery is developed. • The operation optimisation of CCHP agrees well with dynamic simulation. • CCHP–DARS costs slightly more energy (0.29%) than CCHP–ECCS. • The simulation results by the static and dynamic models have no obvious difference. [ABSTRACT FROM AUTHOR]

Nowadays, the growing availability of renewable energy resources is an opportunity to reduce carbon emissions but also a challenge, as advanced control technologies are required. The new generation of smart district heating and cooling networks, for instance, pledges efficient energy distribution, flexibility and low-carbon energy integration. However, in the literature it is hard to find comprehensive frameworks for the integrated setup and testing of smart control strategies. This paper defines and demonstrates a framework that involves all steps of the controller development for small-scale district heating networks: from conceptualization to prototype testing. The innovative controller prototype, which relies on Model Predictive Control and aims to minimize operating costs and/or energy, is demonstrated in three original case studies, one in a simulation environment and two in real systems of different complexity in operational conditions. Compared to the control approaches previously adopted, based on predefined rules and operator experience, the smart solution achieves 6% reduction in cost and up to 34% reduction in energy consumption while meeting user requirements. The fast replicability of the proposed integrated methodology can foster the transition toward the next generation of smart heating networks. [ABSTRACT FROM AUTHOR]

The increase and accumulation of the CO 2 greenhouse gases emissions raises the society's concern and has become a stringent environmental problem. Flue gases released by thermal power plants are important contributors to these emissions and the scientific research community firmly engaged to find efficient carbon capture solutions. The post-combustion CO 2 capture using amines is a leading technology, striving to continuously increase its efficiency and reduce its associated costs. Achieving these aims is progressively dependent on the flexibility of the carbon capture plant to cope with changes in its operation due to the power plant variable loading. Control systems have the potential and are responsible for fulfilling this task. The paper presents the design and assesses the performance of a 4 × 4 proposed decentralized control system intended to reject the most challenging CO 2 influent flow rate and concentration disturbances emerging from the power plant, but also to satisfy the setpoint tracking ability demand. A previously developed complex model for the absorber and desorber columns was extended with a buffer tank and a cross heat exchanger meant to reduce the interacting effects between the columns and support the control system efficiency. The model was then scaled-up with the aim of building a novel simulation tool for an industrial scale carbon capture plant. Carbon Capture rate and Energy Performance indices have been selected as main metrics for evaluating the capture plant performance. Selection of the controlled and manipulated variables was based on a process analysis and the pairing of the control loops was conducted according to the Relative Gain Array matrix. The control system disturbance rejection performance was investigated considering the influent flow rate and CO 2 concentration major disturbances, either with positive and negative slope ramp signals or with periodic changes and considering different testing scenarios. Setpoint tracking of the Carbon Capture rate ability was also examined. Simulation results revealed the capability of the decentralized control system to successfully reject disturbances, demonstrating zero steady state offset, reduced overshoot and short settling time control performance. Setpoint tracking also proved to be efficient. The synergic contribution of all control loops succeeded to achieve flexible control against the action of both ramp, constant or periodic disturbances. The proposed decentralized control system showed promising perspectives for the industrial implementation. • Scaling-up the mathematical model of the carbon capture process developed and validated in a prior studies. • Designing a new 4 × 4 decentralized control system. • Assessing performance of the proposed control system aimed to achieve the desired CO 2 capture rate and energy performance. [ABSTRACT FROM AUTHOR]

Efficient numerical simulation of thermo-hydraulic coupled conditions is critical for analysis and control of DH network. However, for most of meshed DH network, the flow directions of its pipelines may change, which will lead to difficulties in effective numerical calculation of the thermo-hydraulic conditions. This paper established an efficient thermo-hydraulic coupled calculation method, which utilizes the topology sorting algorithm to obtain the calculation sequence of all pipelines during numerical thermal transient calculation, according to the flow directions and flow rates of all pipelines. The flow directions and flow rates are solved by hydraulic condition calculation at each time step. The proposed method is applied to a real meshed DH network for thermal dynamic simulation. Independence analysis of hydraulic computation frequency is conducted, and convergences of the simulated temperature variations are observed when hydraulic computation frequency gets larger. Thermal dynamics of the meshed DH network are analyzed with 10-min hydraulic computation interval. Results show that the temperature decay and time delay can be up to 2.7 °C and 210 min for the simulated network. Thermal dynamic characteristics of supply temperature waves are various considering the distance from heat source, fluctuations of outdoor temperature and the variations of substation flow rate. • Topology sorting based thermo-hydraulic calculation of district heating network. • Independence analysis of hydraulic computation frequency on thermal dynamics. • Thermal transient analysis of a real meshed district heating network. • Influence of substation flow rate on district heating network thermal dynamics. [ABSTRACT FROM AUTHOR]

Nowadays, due also to high hygrothermal comfort requirements, the energy consumption for heating/cooling of modern trains can reach 30% of the related overall electricity demand. Energy-saving of train Heating, Ventilation and Air Conditioning systems can be suitably assessed through dynamic simulation approaches. Specifically, the weather solicitation has to be dynamically accounted for by considering the actual moving train location and orientation. Through such methodology different innovative actions for energy efficiency, environmental impact reduction and comfort enhancement can be analysed by also assessing their economic feasibility. In this paper, a novel simulation tool for the complete performance analysis of trains was developed in TRNSYS environment. To show the capabilities of the considered approach, a novel case study referred to an existing medium-distance train operating in South Italy is presented. Heating/cooling loads and demands, and the related electricity requirements, are dynamically assessed for the standard and revamped train. Several energy saving actions are considered for the coupling between the envelope and the Heating, Ventilation and Air Conditioning systems enhancement. The obtained results return significant benefits in terms of energy saving, avoided CO 2 emissions and comfort. Paybacks depend on operating conditions. Useful design and operating criteria for trains manufacturers and users are provided. • Dynamic simulation for train HVAC system energy performance analyses using TRNSYS. • Customized weather data files for accounting real train locations and orientations. • Innovative energy efficiency solutions for trains with saving up to 6.0 MWh e /y. • Economic feasibility of energy efficiency solutions for trains. • Reduction up to 50% of the train environmental impact. [ABSTRACT FROM AUTHOR]

Biomass combined heat and power plants (CHPPs) can operate target-specifically because of their controllability while supporting decarbonization in district heating. The transition from the German Renewable Energies Act funding, which has promoted biomass CHPPs but is now about to expire, to direct marketing, is a major economic challenge for many biomass-heating grids. To successfully accomplish it, the flexible operation of biomass CHPPs, compared to the previous baseline-operation, is becoming an increasingly important requirement if participation in the electricity markets is to remain profitable. This paper presents a techno-economic assessment of flexible CHPP operation in a modeled district heating system with a CHPP, a peak load boiler and a thermal heat storage. The simulation model compares two cases - a natural gas and a wood-chip gasifier CHPP. The analysis of the results investigates the parameters that need to be adapted to make biomass-fired CHPP heating grids more efficient compared to fossil-fired CHPP heating grids in a flexible operating scenario. It highlights the technical and economic superiority of a fossil-fired CHPP in flexible operation in comparison to the wood gasifier system. The introduction of a CO 2 -tax on natural gas as a fuel, currently under discussion in Germany, would increase the competitiveness of the wood gasifier. • Simulation model of a district heating system. • Model units are wood or natural CHP plant, peakload boiler and heat storage. • Three scenarios for CHP plant dispatch under consideration of electricity prices. • Focus on dynamic differences of the CHP plant operation strategy. • Results show limitations in operational flexibility of the wood gas CHP plant. [ABSTRACT FROM AUTHOR]

Double reheat is a potential technique to increase the efficiency of coal-fired power plants. Large penetration of renewable power requires coal-fired power plants to operate flexibly. The thermal inertia of a double-reheat boiler is extremely high due to its complicated flow, strong coupling and numerous devices, which seriously restrict the operational flexibility of double-reheat coal-fired power plants. In this study, dynamic simulation models and temperature control systems of a double-reheat boiler are developed via GSE software and then validated to understand the heat storage change law. An improved control model considering heat storage changes is proposed. The flexibility of original and improved control strategies is compared. It turns out that steam temperatures in the boiler system with the original control exceed the allowable ranges when the load cycling rate is 1.5% Pe0 min−1. By contrast, steam temperatures in the boiler system with the improved control remain within the allowable ranges when the load cycling rate is 3.0% Pe0 min−1. The response time with the improved control is shorter than that with the original control. This study is expected to provide a detailed reference for improving the flexibility of double-reheat power plants. • Dynamic models and control system of a tower double reheat boiler are developed. • Heat storage characteristics of the double reheat boiler are studied. • An improved control considering heat storage is proposed. • The response time shortens after the improved control is applied. • Load-cycling rate with the improved control increases to 3.0% Pe0 min−1. [ABSTRACT FROM AUTHOR]

Combined heat and power generation traditionally allows for higher energy performance than separate production of heat and electricity. However, the significant increase of the renewable energy sources contribution in electricity production has spatially and temporally modified the context in which polygeneration systems operate and the energy and environmental profitability of these technologies could be undetermined. In such a situation it seems interesting to investigate the influence of the power grid efficiency variation on the polygeneration systems performance. For this purpose energy and environmental performance of a proposed system based on combined production are compared to those achieved by a conventional system based on separate production. The primary energy demand of conventional and proposed systems due to electricity depends on the efficiency of the national electric energy system features. In this paper, this efficiency is considered to be time-varying (hour-by-hour) and it is further taken into account that the electric system efficiency changes in different regions of the same Country. According to Italian day ahead market of electricity the national territory is divided in 6 zones; two of them (Centre-North zone and Centre-South zone) will be specifically considered and compared hereinafter. The differences that arise in results are also assessed with respect to the case in which national and local average efficiency is taken into account. The environmental analysis is performed considering the average and the time-varying Italian and local electricity emission factors. The results have highlighted that the cogeneration system feasibility depends upon the variability of these factors. Indeed, referring to thermoelectric-based power grid efficiency, only in Centre-North zone is more energetically convenient to produce heat and power by separate production systems. The environmental analysis outcomes have showed the same trend of energy analysis results in all the considered zones underlining that the evolution towards sustainability in Smart Grids requires an integrated approach. • Separate and combined production of heat and power systems are compared. • Dynamic simulations are conducted to perform energy and environmental analyses. • Time-varying power grid efficiency and emissions factors are considered. • Variable energy and environmental indices in electricity market zones are defined. • Sensitivity analysis is performed considering the indicators provided by regulation. [ABSTRACT FROM AUTHOR]

Thermal energy storage system in concentrating solar power plants can guarantee sustainable and stable electricity output in case of highly unstable solar irradiation conditions. In this paper, the lumped parameter method is used to develop the models of different thermal energy storage systems. In order to improve the reliability as well as the prediction accuracy of developed models, the charging/discharging process is firstly simulated, and then the dynamic characteristics of thermal energy storage systems are fully tested by imposing 15% step disturbance of mass flow. The results show that the charging/discharging characteristics of the three different thermal energy storage systems are almost the same, which have little to do with the storage mediums used in the systems. Besides, for the representative 1MWe solar parabolic trough power plant, a 15% step up disturbance of oil mass flow will result in a small increase (1.8% and 1.3% respectively) on the outlet temperature of oil and molten salt. On the other side, a 15% step down disturbance of oil mass flow will lead a 2.7% and 2.2% decrease on the outlet temperature of oil and molten salt respectively. In order to verify the validity of the proposed models, the simulation results are compared with both the design points and representative experimental data from the 1MWe solar parabolic trough power plant. The results show that the maximum relative error is not more than 1% when comparing with the design points and the maximum relative error is not more than 12% when comparing with the representative experimental data. Conclusions of this paper are good references for system design, control and commissioning of concentrating solar power plants. • Thermal energy storage can provide sustainable and stable electricity output. • Lumped parameter method is used to build the model of thermal energy storage. • The dynamic characteristics are tested by a 15% step disturbance of mass flow. • A 15% step-up will result in a 1.3% increase in molten salt outlet temperature. • A 15% step down will result in a 2.2% decrease in molten salt outlet temperature. [ABSTRACT FROM AUTHOR]