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The harsh indoor environment in winter in the hot-summer and cold-winter zones of China and the increasing demand for winter heating from residential consumers have prompted more and more researchers to address the energy-efficient heating problem in non-centralized heating areas. A computational fluid dynamics model of a typical building was developed to analyze the dynamic heat transfer characteristics and energy consumption of interior partitions under decentralized heating in this region, of which the accuracy of the established model was proved by the relative error of less than 5% compared with the experimental measurement. Then seven typical kinds of interior partition configurations with different wall thickness, wall material, and insulation layer locations were developed and evaluated through simulation analysis. Transient heat storage ratio and cumulative heat storage ratio were proposed to demonstrate the dynamic heat transfer characteristics of interior partitions. The simulation results showed that 180 mm and 220 mm solid clay bricks can reduce energy consumption by 17.56% and 30.23%, respectively, compared with 120 mm solid clay bricks. The energy consumption of fly ash aerated concrete and solid clay brick partitions were reduced by 10.18% and 19.02%, respectively, compared with porous concrete partitions. The dynamic heat transfer characteristics of internal partitions with internal insulation were similar to those with external insulation due to the reduction in unnecessary energy consumption transferred to adjacent unheated rooms by about 20% compared to that without insulation. And the heat consumption of interior partitions under convective heating was 17.3% higher than under radiant heating. [ABSTRACT FROM AUTHOR]

Reducing carbon footprints and enhancing operational flexibility are crucial for the future development of coal-fired power plants (CFPPs). This necessitates the deployment of post-combustion carbon capture (PCC) and molten-salt heat storage (MSHS) systems. Given the various integration schemes and complex interactions, understanding the comprehensive performance of the integrated CFPP-PCC-MSHS system is important. This paper proposes an integration scheme for 1000MWe ultra-supercritical CFPP, solvent-based PCC and MSHS, achieving cascade energy utilization. A dynamic simulation model for the CFPP-PCC-MSHS system is developed to understand the dynamic couplings between subsystems. Comprehensive performance analyses are conducted to evaluate the thermodynamics, flexibility and safety of the integrated system under various operating conditions. Simulation results indicate that deploying MSHS reduces the thermal and exergy efficiencies of the CFPP-PCC system by 0.18 % and 0.19 %, respectively, but effectively expands the adjustable power load range by 6.08 % under the fixed 90 % CO 2 capture rate mode. Meanwhile, the integration of MSHS offers alternative pathways to improve the power ramping rate to 13.33 MW/min. The heat charging/discharging process of MSHS induces fluctuations in temperature and pressure within the turbine, potentially affecting plant operating safety. This paper provides useful insights for the design, retrofit and operation of new generation of CFPPs. • A dynamic model of the integrated CFPP-PCC-MSHS system is developed. • The integration of MSHS reduces thermal and exergy efficiencies by 0.18 % and 0.19 %. • MSHS enlarges power range of CFPP-PCC by 6.08 % under 90 % CO 2 capture condition. • Deploying MSHS offers effective pathway to improve the power ramping rate of CFPP. • Deploying MSHS induces pressure and temperature variations at each turbine stage. [ABSTRACT FROM AUTHOR]

The industrial sector is one of the biggest oil consumers in Cyprus, corresponding to 20% of the fuel consumption. A parabolic trough collector (PTC) system seems the best option to produce clean thermal energy at higher temperatures than those that can be achieved from the already widely used flat plate collectors on the island. This paper presents a simulation model built to investigate the performance of the first industrial PTC system in Cyprus, installed at the Cyprus biggest soft drinks factory. The simulation model is built in TRNSYS and is validated using data from the real PTC system installed at the factory. The results show a very good fitting between the operating parameters and the power output of the Solar Field (SF), Concrete Thermal Storage System (CTES), and the Steam Generator (SG). The average percentage relative error of the system's contribution to the process is less than 6.32% for the daily steam production and during a week did not exceed 6.45%. The novelty of this study is the development of a design tool that can be used by potential interested industries to identify the suitable system that fits their needs. All data are provided in the form of graphs and allow anyone to use as input data the thermal energy demand and required steam temperature of the industry to retrieve information about the size of a suitable system which satisfies these requirements depending on each case. The payback period for all cases examined varies from 2 to 6 years, depending on the size of the system. • Validated dynamic simulation model of a PTC system working under various operation modes for Industrial Process Heat application. • Evaluation of the operation modes and strategies developed to make the PTC system dispatchable. • A scaled up model for of the validated dynamic simulation model. • Development of a tool for potential interested industries in Cyprus for PTC systems. [ABSTRACT FROM AUTHOR]

Sensible thermal energy storage is the most common solution for small-to-medium solar process heat systems. Hence, it is vital to enhance the thermal stratification and energy utilization of stratified tanks. In this study, four process heat systems are dynamically simulated: 1) S0 with a single outlet port to the load, 2) S1 with a single port and a thermostatic mixing valve, 3) M0 with multiple ports, and 4) M1 with multiple ports and a mixing valve. Two novel models are proposed for the compound parabolic collectors and the stratified tanks. System M1, with annual system efficiency of 47.3% and solar fraction of 0.57, was found to be the best-performing one, followed by S1, M0, and S0. System M1 also reduced the annual energy consumption of the backup heater in S0 by 16.45%. The thermostatic mixing valve reduced the thermocline thickness. The incorporation of both mixing valve and multiple ports delayed the startup of the heater, reduced the system's thermal losses, and slightly improved the collectors' efficiencies. The proposed tank model can be a viable tool for solar energy designers to optimize the number and relative positions of the inlet and outlet ports for maximized system efficiency and solar coverage. [Display omitted] [ABSTRACT FROM AUTHOR]

A nuclear heating system integrated with a heat storage tank (HST-NHS) is a promising technical solution for countries with large-scale heating demand. HST-NHS can greatly curtail carbon dioxide emissions and contribute to sustainable development. Appropriate control strategies are not only crucial to realize the real-time matching between HST-NHS heat supply and heat demand, but also ensure the stable and safe operation of HST-NHS. Until now, control strategies for HST-NHS have received limited attention. A refined dynamic simulation model for HST-NHS is established based on APROS software. The verification of the built model in steady state and transient state is completed. Two basic control strategies for the primary heating network (PHN) of HST-NHS, constant supply water temperature and variable flow rate (CT-VF) and variable supply water temperature and constant flow rate (VT-CF) are presented in detail. Based on various typical working conditions of a central heating region in Liaoyuan City, the control effects of two control strategies are investigated. Additionally, a comprehensive performance comparison between the two strategies is explored. Simulation results indicated that under the two control strategies, the indoor temperature can be effectively controlled at a high comfort level. During the same typical day, the total energy consumption cost under the VT-CF control strategy is 0.5 × 105 yuan lower than that under the CT-VF control strategy. • Dynamic model of nuclear heating system with heat storage is developed. • The verification of the built model in steady and transient state is completed. • Control effects of two basic control strategies during typical days are evaluated. • A performance comparison of two basic control strategies is conducted. [ABSTRACT FROM AUTHOR]

A micro gas turbine (MGT) is a potential option for distributed energy systems driven by fuel and solar energy. The dynamic characteristics of a solar-hybrid microturbine system are essential to its control development and performance assessment. In this paper, a dynamic model is proposed, including an MGT (T100), a tubular air receiver and a sensible thermal energy storage system, which are experimentally validated well. Based on the developed model, the dynamic responses of a solar-hybrid microturbine system in stand-alone mode are studied considering load and Direct Normal Irradiance (DNI) changes. Results show that the fuel consumption is greatly reduced by integrating solar energy, which comes at the cost of system instability; if the investigated system experiences a significant load decrease, heliostats must be oriented away from the air receiver to ensure a stable operation, whereas the load must be increased incrementally to avoid a compressor surge in the case of a significant load increase. Compared to load change, DNI change will cause smaller overshoots of the MGT's rotational speed and surge margin. The system is simulated with measured DNI and shows that the thermal energy storage can reduce the fluctuation of combustor inlet temperature from 130.8 °C to 12.8 °C. • A dynamic model including micro gas turbine, solar receiver and thermal energy storage sub-models is experimentally validated. • Dynamic performance of a solar-hybrid microturbine system is investigated with changing load or solar irradiation. • Control strates are proposed for the investigated system. • The maximum share of solar energy reaches 64.7% for the system with an electrical efficiency of 24.1%. [ABSTRACT FROM AUTHOR]

• A hybrid solar dryer of wood is successfully modeled using TRNSYS software. • Maximum discrepancy between numerical and experimental results does not exceed 10%. • Energetic and environmental performance of the wood dryer system are investigated. • Energy provided by the auxiliary is higher during winter and lower during summer. • 34% of CO 2 emissions are annually avoided by using a solar compound collector. The aim of this work is to develop a numerical model for investigating the performance of an indirect hybrid solar dryer of wood using TRNSYS software. A solar compound parabolic concentrator (CPC) is used to produce thermal energy and the hourly dynamic simulations are conducted under Moroccan meteorological data. A comparative study between our numerical results and experimental results shows a good agreement and the Mean Relative Error (MRE) and the Root Mean Squared Error (RMSE) are 3.9% and 0.024 kg/kg, respectively. The energetic performance of the solar dryer components is investigated and the effect of some design and operation parameters on drying kinetic is presented. An environmental analysis is performed by focusing on the amount of carbon dioxide (CO 2) emissions due to the combustion at the auxiliary heater system. Results show that the integration of the solar collector into the dryer system leads to reduce the energy consumption by the auxiliary heater system and to avoid annually about 34% of CO 2 emissions. [ABSTRACT FROM AUTHOR]

Abstract Integration of a latent heat energy storage into a solar heating system has become a well-known engineering practice that can bridge the mismatch between the heat demand of the served building and heat supply from the solar heating system. However, control schemes, energy performance analysis, characterization and optimization of such a system under the Tibet climatic/altitude conditions still remain a challenge. This research aims to investigate a PCM-integrated solar heating system applicable to Tibet which is unique in terms of the altitude, solar radiation, atmospheric pressure and water boiling temperature etc. The whole process involves (1) identification of the unique features of Tibet climate and altitude and relevant requirements to the solar system; (2) design of a PCM-integrated solar heating system based on a selected building in Lhasa and planning the potential control strategies appropriate to such a system; (3) analysis of the system's energy performance under different operational schemes; and (4) recommendation of the most appropriate system operational scheme and design strategy. A dynamic simulation model was established and applied to study the energy performance of such a system, in which the solar energy usage rate is defined as the performance evaluation index. It is found that the operational scheme 'A' has the best energy saving effect, followed by operational schemes B and C. The system presents a more favorite energy performance between 9:00 h–18:00 h, compared to other time slots in a typical winter day. Change in operational schemes creates a significant impact on the energy saving effect of the system. The results help wide and fast deployment of the PCM-integrated solar heating system and enable the determination of the best performing operational scheme and associated performance data appropriate to Tibet or similar regions in the world, thus making a significant contribution to the saving of fossil fuel energy consumption and reduction of the carbon emission on the regional and global scales. Highlights • Energy performance and operational schemes of a Tibet-focus SHS-PCM was investigated. • Operational scheme A is the best and C is the worst in terms of energy saving rate. • Daytime heating achieved a higher energy efficiency compared to the full day heating. • Energy saving rates for three schemes are 64%, 50% and 46% for the full day heating. • Energy saving rates for three schemes are 92%, 79% and 24% for daytime heating. [ABSTRACT FROM AUTHOR]

• An innovative slim decentralised plug-and-play tank is proposed for DHW production. • Model calibration is performed by experimental data in charge/discharge process. • Retrofit solution cuts required annual energy in half of which 82% is RES quota. • Optimised charging scheme reduces the total annual electrical energy by 5.2 %. • A degree increment in draw-off temperature increases annual CO 2 emission by 103 kg. The present study deals with a multi-objective analysis of an innovative decentralised system to produce and store domestic hot water (DHW), emphasising on the combined effects of the technological aspect, control strategy and user's behaviour. The proposed system, by relying on thermal energy storage, decouples energy production and demand while shaves peaks in the energy demand and, at the same time, provides more autonomy to users through local storages. To identify subtle interactions in components of DHW system, dynamic simulations are carried out by establishing a coupled TRNSYS-MATLAB code, calibrated and validated by experimental measurements. The energy analysis implies that the proposed system cuts the required annual electrical energy in half, of which up to 82% of needed primary energy is supplied from renewable sources, compared to previous electrical-decentralised system. The optimisation of the results through applying control strategies indicates that adopting a three-time charging scheme is advantageous in terms of providing a more stable temperature profile as well as a higher hot water temperature. Compared to an available-by-demand operation, this scheme reduces the required total annual electricity by 5.2 % and enhances total thermal loss from components up to 4.0%. Furthermore, a sensitivity analysis on the results emphasises the striking role of the user behaviour in electrical energy consumption either via draw-off temperature or adjusting the pre-defined temperature for activation of the built-in auxiliary heater. [ABSTRACT FROM AUTHOR]

The aim of this paper is to evaluate optimum design criteria for developing solar thermal integrated membrane distillation system for cogeneration of pure water and heat. The temporal and seasonal variability of the driving variables, such as ambient temperature and solar irradiance requires dynamic simulation of combined system using tools such as TRNSYS. Dynamic simulation and parametric analysis enables to design a functional system and then optimizes the design. In this study, the application of cogeneration system for residential households in United Arab Emirates is considered for per capita production of 4l/day of pure water and 50l/day of domestic hot water. The performance of cogeneration is optimized by varying various design parameters such as collector tilt angle, thermal storage volume and area of the solar collector field. Cogeneration solar fraction and payback period are considered as performance indicators for energetic and economic optimization. Further simulations are extended from small to large family application and for utilizing either flat plate (FPC) or evacuated tubular collector (ETC) systems. Optimized cogeneration system utilizes more than 80% of the available solar energy gain and operates at 45% and 60% collector efficiencies for FPC and ETC systems respectively Also, combined and system efficiencies of the cogeneration system are compared with standalone operational efficiencies for solar heaters and solar membrane distillation systems. Results show that, cogeneration operation reduces 6–16% of thermal energy demand and also enables 25% savings in electrical energy demand. Payback period could be reduced by 2.5–3 years by switching from regular solar water heating to cogeneration systems along with 4-fold increase in net cumulative savings. [ABSTRACT FROM AUTHOR]

• A new energy system is developed and examined using dynamic modelling to meet the needs of a two-story structure. • To decrease the size of the plant, including the PVT size and fuel consumption, the PCM is incorporated into the building. • Fuel consumption and prices are reduced by 17.24% and 8.57%, respectively, using the suggested approach. • Exergy efficiency, unit product cost, and CO 2 emission of 64.3 %, 0.26 $/kWh, and 0.21 kg/kWh are obtained respectively at optimum point. The buildings energy sector is expected to account for 40% of total world energy consumption and 40% participation on total carbon dioxide emissions, according to the International Energy Agency reports. The present study proposes a novel integrated system to meet all loads of the house's energy requirements. The system employs a heat storage tank rather than pricey batteries, which helps to keep the total cost of the system as low as feasible. Also, the system is developed for an on-grid operation, being capable to sell surplus energy to the grid helping to reduce the payback time. Dynamic modeling is conducted to analyze the system performance to provide heating, cooling and power demands of a case study building, for which two scenarios of with and without Phase Change Material (PCM) incorporation is considered. The influence of critical design factors is investigated, after which a tri-objective optimization is carried out. It was found that, the integration of PCM energy storage would reduce the annual heating and cooling demands of the building by 25.6%. As a result, the exergy efficiency of the proposed system increases by 13 % and the product cost is reduced by 8.57%. Based on the obtained yearly average results, the proposed building energy system yields exergy efficiency, unit product cost, and CO 2 emission of 64.3 %, 0.26 $/kWh, and 0.21 kg/kWh, respectively. [ABSTRACT FROM AUTHOR]

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 paper suggests a multi-criteria approach for the energy refurbishment of historical buildings, proposing methodologies for the performance analysis, coupling several experimental and numerical studies. The target consisted in a rigorous evaluation procedure, in order to guarantee the necessary reliability of a numerical model of the system “building envelope/technical plants”, on which testing the technical and economical convenience of energy retrofit solutions. The paper collects the long work carried out by several Institutions during the last years, on Building “Palazzo dell’Aquila Bosco-Lucarelli”, a historical building located in Benevento (Southern Italy), currently analyzed in order to define the technical adoption of possible improving actions. The carried out studies, beyond the proposition of an operational methodology, are aimed to evidence a best-practice specified for the Italian territorial context, which has several historical buildings needing restoration. Carefully applied investigations, based on various methodologies and through several instrumentations, allowed the definition of a numerical model correspondent to the real building, defined also comparing the results with the historical requests of gas and electricity. Moreover, dynamic energy simulations tested the effectiveness, singularly and coupled, of several solutions for the building energy optimization. A significant potentiality of energy and economic optimization has been demonstrated. [Copyright &y& Elsevier]