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1
المصدر: Energy and Buildings. 199:47-61
مصطلحات موضوعية: business.industry, 020209 energy, Mechanical Engineering, Airflow, 0211 other engineering and technologies, 02 engineering and technology, Building and Construction, 7. Clean energy, Plenum space, Automotive engineering, Energy storage, Mechanical room, Setpoint, Peak demand, 021105 building & construction, HVAC, Heat exchanger, 0202 electrical engineering, electronic engineering, information engineering, Environmental science, Electrical and Electronic Engineering, business, Civil and Structural Engineering
الوصف: This paper presents a simulation study of an active energy storage device intended to enhance building operation. This device –which is designed for installation in the ceiling plenum of an office, a mechanical room or in other convenient locations– consists of an arrangement of several panels of a phase-change material. It may be charged or discharged as required with an air stream passing between the panels, thus operating as a PCM-air heat exchanger (PCM-HX). The first part of the paper focuses on the design of the PCM-HX. Several design configurations are evaluated; investigated parameters include the PCM-HX dimensions, the number of air channels and airflow rates. The paper also includes an experimental validation of the PCM model. Performance criteria that were considered in the parametric study include the amount of stored heat, the time needed to charge/discharge the PCM storage and the overall energy density of the device. The second part of the paper evaluates different control strategies aimed at reducing peak demand and the size of HVAC system. The impact on peak load of a linear ramp for the temperature setpoint is investigated: it was found that a two hour linear ramp in temperature setpoint –together with a PCM-HX configuration with six air channels– can reduce the peak heating load by 41% as compared to a benchmark case without the PCM-HX.
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2
المصدر: Energy and Buildings. 196:214-226
مصطلحات موضوعية: 020209 energy, Mechanical Engineering, 0211 other engineering and technologies, 02 engineering and technology, Building and Construction, Energy consumption, Thermal energy storage, Automotive engineering, law.invention, Model predictive control, Solar air conditioning, Backup, law, Storage tank, Solar Resource, 021105 building & construction, 0202 electrical engineering, electronic engineering, information engineering, Absorption refrigerator, Electrical and Electronic Engineering, Civil and Structural Engineering
الوصف: This work presents the benefits of using a model predictive control (MPC) approach for controlling a high efficiency absorption chiller-based solar cooling system with thermal energy storage, incorporating perfect solar resource and load forecasting information. A dynamic physics-based model of the solar air-conditioning system has been built for studying the system behavior. A genetic algorithm based predictive controller is utilized to minimize backup energy consumption while satisfying the cooling demand. The simulations have been carried out using the open-source programming language Python. Detailed investigation of the role of the predictive controller and its decision strategy have been carried out using ten and fifty days simulations. Effect of storage tank heat losses has been investigated. For the simulated example case pertaining to a building, results show the model predictive controller usage delivers about 10% reduction in auxiliary energy use in the system. This is achieved through reduction in tank heat losses, better utilization of heat stored in the tank. It is seen that the MPC based controller enables new system operational capabilities by running the solar collector pump in variable flow mode and allowing the simultaneous heat delivery from storage and backup devices. Opportunities to improve the MPC benefits have been identified. The benefits of the MPC are seen to be sensitive to the system parameters and specific constraints. In summary, this paper provides valuable insights into solar cooling system design and control.
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3
المؤلفون: Joonbyum Kim, Yujun Jung, Hoseong Lee
المصدر: Energy and Buildings. 193:201-215
مصطلحات موضوعية: 020209 energy, Mechanical Engineering, 0211 other engineering and technologies, Building model, 02 engineering and technology, Building and Construction, TRNSYS, Thermal energy storage, Prime mover, Automotive engineering, Boiler (water heating), Micro combined heat and power, Heating system, 021105 building & construction, 0202 electrical engineering, electronic engineering, information engineering, Environmental science, Electrical and Electronic Engineering, Operating cost, Civil and Structural Engineering
الوصف: In this study, a medium-sized residential building is analyzed when an internal combustion engine-based combined heating and power (CHP) system is applied. The multi-family building with a floor heating system is selected to represent typical Korean residential situation. Simulation models are developed for the building, prime mover, thermal storage system, and cooling and heating systems. The validated CHP model is integrated to the building, and it is operated with a thermal load following method. The CHP applied residential building model is compared to the baseline model with a grid power and a gas fired boiler system, in terms of energy, environment, and economics. When the CHP system is applied to the residential building in South Korea, total primary energy consumption is decreased by 18.4%, CO2 emissions by 11.8%, and operation cost by 9.6%, respectively. Based on the facility and operating cost, the payback year is calculated as 10.2. In addition, the building performance is further discussed in terms of weather conditions, utility fee change and energy utilization method.
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المؤلفون: Junhee Hong, Junho Lee, Sang Min Lee, Dongsoo Har, Jintae Cho, Sangkeum Lee, Heedae Jung
المصدر: Energy and Buildings. 191:174-186
مصطلحات موضوعية: Power management, Computer science, 020209 energy, Mechanical Engineering, 0211 other engineering and technologies, Technical information, 02 engineering and technology, Building and Construction, Multi-objective optimization, Automotive engineering, Energy storage, Scheduling (computing), Power (physics), Demand response, Software deployment, 021105 building & construction, 0202 electrical engineering, electronic engineering, information engineering, Electrical and Electronic Engineering, Civil and Structural Engineering
الوصف: A novel power management for nanogrids is presented. In this paper, effect of resident location in residence is taken into account for evaluation of power consumption in nanogrids. Depending on the resident location, operating conditions of heater, ventilation fan, and air-conditioner are adjusted. Electric appliances that allow delayed use, i.e., shiftable, are scheduled for efficient power management. Considering massive deployment of energy storage system (ESS) as a supplementary power source, effect of the ESS on power management is investigated. Demand response program for reduced electricity cost is also considered for power management. As a result, an objective consisting of power consumed by non-shiftable and shiftable electric appliances, power supplied/consumed by the ESS during discharging/charging, and time-varying electricity cost is formulated. Another objective for power management is a function of delays in scheduling of shiftable electric appliances. Variation of resident location combined with temporal use of electric appliances according to the resident location are considered as the resident behavior and incorporated into these two objectives. Using these two objectives, a multi-objective optimization is performed for nanogrids at each time interval. It is demonstrated by simulations that leveraging resident behavior is beneficial for power management of nanogrids. In addition, effects of the number of residents in each apartment and combined activity of each resident on the power management are presented with related simulation results.
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المؤلفون: Attila Balint, Hussain Kazmi
المصدر: Energy and Buildings. :286-296
مصطلحات موضوعية: Flexibility (engineering), 020209 energy, Mechanical Engineering, 0211 other engineering and technologies, 02 engineering and technology, Building and Construction, Automotive engineering, Electrification, 021105 building & construction, Available energy, Air source heat pumps, 0202 electrical engineering, electronic engineering, information engineering, Environmental science, Operational planning, Grid energy storage, Electrical and Electronic Engineering, Energy source, Energy (signal processing), Civil and Structural Engineering
الوصف: With increasing proliferation levels of variable energy sources, flexible energy loads will become increasingly important to help stabilize the energy grid. Increasing electrification of heating systems means that the thermal inertia of buildings and hot water vessels can provide a ubiquitous, low cost alternative to electrical storage for providing this energy flexibility. However, it is unclear how this flexibility fluctuates with various factors such as occupant behaviour and ambient conditions in the real world. This paper quantifies the effect of different influencing factors on the energy flexibility of residential hot water systems using data from a large scale real world pilot. All the houses considered in this analysis feature identical air source heat pump hot water systems, along with 200 l storage vessels. It is shown that ambient conditions, control algorithm and occupant behaviour, all influence the available energy flexibility of the hot water system, albeit in different ways. Available capacity for energy flexibility and the corresponding recovery periods can differ by as much as two to four times for identical storage, meaning that these differences should be taken into account during operational planning with flexible loads. Additionally, it is shown that the implemented control strategy provides a meaningful avenue to alter the available energy flexibility. The paper also highlights key differences in the way these factors influence the overall energy demand when compared to available flexibility.
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المؤلفون: Alain Moreau, Gino Lacroix, Hélène Thieblemont, Fariborz Haghighat
المصدر: Energy and Buildings. 172:442-458
مصطلحات موضوعية: Computer science, 020209 energy, Mechanical Engineering, 0211 other engineering and technologies, Building model, 02 engineering and technology, Building and Construction, 7. Clean energy, Electrical grid, Automotive engineering, Energy storage, Load management, Model predictive control, Supervisory control, Peak demand, 13. Climate action, Control theory, 021105 building & construction, 0202 electrical engineering, electronic engineering, information engineering, Electrical and Electronic Engineering, Civil and Structural Engineering
الوصف: In cold climates, the electrical power demand for space conditioning during certain periods of the day becomes a critical issue for utility companies from an environmental and financial point of view. Shifting a portion or all the demand to off-peak periods can help in reducing the peak demand and stress on the electrical grid. To predict the required energy that needs to be stored, predictive supervisory control strategies such as Model Predictive Control (MPC) have been developed, by which the future operating modes of storage systems can be preplanned. However, control strategies like MPC requires a building model and an optimization algorithm. Their development is time-consuming and also requires high implementation cost. This paper is aimed at developing a new simplified predictive controller to manage an electrically heated floor for shifting and/or shaving the building peak energy demand. The function of the developed controller is to increase the rate of energy storage during off-peak hours and to decrease it during peak periods, while maintaining occupants’ thermal comfort. To achieve this goal without using a detailed building model, a simplified solar predictive model, using available online weather data has been proposed. The controller approach is based on a learning process; it takes building responses of previous days into consideration. The developed algorithm was applied on two models of a single-storey building, with and without basement. Results show a significant decrease in thermal discomfort, average applied powers during peak periods and mid-peak periods. The approach has also proven to be financially attractive to both supplier and consumer.
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المؤلفون: Yanfeng Liu, Guannan Li, Qianjun Mao, Zhifan Wang, Dengjia Wang, Li Tao
المصدر: Energy and Buildings. 254:111624
مصطلحات موضوعية: Mechanical Engineering, Process (computing), Mode (statistics), Building and Construction, Energy consumption, Thermal energy storage, Automotive engineering, Degree (temperature), Terminal (electronics), Thermal, Environmental science, Electrical and Electronic Engineering, Energy (signal processing), Civil and Structural Engineering
الوصف: Previous experimental studies have shown that the alternating operation of the combined floor and Kang heating terminal has obvious advantages in satisfying the differentiated thermal demands, but it is still difficult to meet the indoor air temperature and bed temperature at the same time. For better use of the combined heating terminal, more in-depth simulation and optimization research are carried out. Firstly, based on the experimental research, an analysis model of heat dissipation performance of the combined heating terminal with alternating operation is established, and the accuracy of the model is verified by the experimental data. Secondly, by setting up the meteorological data of typical building and typical day, the heat storage/release performance of the combined heating terminal and its influence on thermal environment in the alternating operation process are simulated and analyzed. The design parameters, operation parameters and strategies are explored based on the temperature response time and the satisfaction degree of differentiated thermal demands. The influence characteristics of each parameter of the combined heating terminal on the thermal environment are obtained. Finally, the energy consumption under two different working conditions of the combined heating terminal temporal-spatial partitioned and the traditional comprehensive heating mode is compared and discussed. The results show that the energy saving rate of the combined heating terminal temporal-spatial partitioned heating mode can reach to 27.3%. The research results can provide a design basis for the application of combined floor and Kang heating terminal in the rural buildings in northwest China.
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المؤلفون: Alice Mugnini, Fabio Polonara, Alessia Arteconi
المصدر: Energy and Buildings. 253:111335
مصطلحات موضوعية: Flexibility (engineering), business.industry, Mechanical Engineering, Building and Construction, Thermal energy storage, Automotive engineering, Fan coil unit, law.invention, Demand response, Air conditioning, law, Peaking power plant, Water cooling, Environmental science, Electrical and Electronic Engineering, business, Civil and Structural Engineering, Heat pump
الوصف: Space cooling of buildings shows an increasing trend in energy use worldwide. The exploitation of the energy flexibility reserve obtainable from buildings cooling-loads management can have an important role to improve the security and the reliability of the electricity power grid. Many studies in literature assess the energy flexibility potential of air conditioning systems; however, the role of the specific cooling technology is always scarcely explored. The objective of this work is to provide an evaluation of the operational energy flexibility that can be obtained involving the most common residential space cooling technologies, paying particular attention to the distribution system (e.g., all-air system, fan-coil units with and without the addition of a thermal energy storage and hydronic massive systems). The analysis is carried out with dynamic simulation models for the various cooling systems involved. Results show a great influence of the adopted distribution system in the implementation of a flexibility request. In particular, all-air systems (i.e. split systems) show the lower flexible behavior (they require up to 10 h of precooling to be off during a peak hour). Whereas the adoption of fan coil units coupled with a thermal energy storage allows to implement different peak shaving strategies without compromising the indoor air temperature with low drawback effects in terms of anticipated electricity overconsumptions (no precooling of the air is required and a maximum of 23 % increase in electricity consumed in the time before the event occurs, with a reduction of 16 % in subsequent hours). In case of ceiling cooling systems, results highlight that as the thermal inertia of the system increases, the indoor conditions are less affected, but the anticipated overconsumption of the heat pump increases (for the same Demand Response event the electricity overconsumption goes from + 67 % to +116 %, passing from ceiling panels to concrete ceiling). The results obtained from this analysis are then used to draw flexibility curves, which aim at providing a characterization of the flexibility of a cooling system. They can be used to predict, for typical installations, the system behavior in presence of a peak power reduction strategy in terms of pre-cooling duration, energy use variation and modification of the temperature comfort bandwidth. Such predictions are important because they can provide insights on the design and operation of space cooling systems in demand side management strategies.
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المؤلفون: Ahmad Mojiri, Gary Rosengarten, Yuanyuan Li, Cameron Stanley
المصدر: Energy and Buildings. 250:111234
مصطلحات موضوعية: Electrical load, business.industry, Mechanical Engineering, Building and Construction, Thermal energy storage, Solar energy, Automotive engineering, law.invention, law, Photovoltaics, Water cooling, Environmental science, Electricity, Electrical and Electronic Engineering, business, Building energy simulation, Civil and Structural Engineering, Heat pump
الوصف: Due to the mismatch between rooftop solar energy generation and residential electrical demand, considerable solar energy is exported into electricity networks causing a range of issues such as voltage instability and connection overload. To address these problems, we propose and analyse a residential hot water, heating and cooling system, which features a heat pump combined with thermal energy storage to align peak thermal loads with output from a rooftop solar system. This work quantifies the impacts of thermal storage on residential space-conditioning peak load reduction. Annual hourly thermal and domestic hot water loads were determined for a representative Australian house, located in Brisbane, using building energy simulation software and verified using measured data. Combined with the measured sub-metered electrical loads of other electrical appliances, this data was used to simulate the solar system export, heat pump demand, and thermal storage system performance. Results show that by combining a 5-kW solar system, the proposed system can reduce annual grid-electricity demand by approximately 76% compared with a conventional non-thermal storage system. Peak electrical load was also observed to undergo a temporal shift and reduce by approximately 45%. Furthermore, the solar fraction for air-conditioning and domestic hot water loads reached 84%, while solar self-consumption increased to about 56%. This study demonstrates that the proposed system is an effective means of managing electricity demand, shifting peak load and improving solar utilization, thus relieving stress on electricity networks from high penetration of solar photovoltaics.
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المؤلفون: Li Ning, Zhao Yang, Gao Yide, Feng Rui, Qiang Zhang
المصدر: Energy and Buildings. 167:136-151
مصطلحات موضوعية: Primary energy, 020209 energy, Mechanical Engineering, Cooling load, Mode (statistics), 02 engineering and technology, Building and Construction, Automotive engineering, Energy storage, law.invention, 020401 chemical engineering, Approximation error, law, 0202 electrical engineering, electronic engineering, information engineering, Gas engine, Environmental science, 0204 chemical engineering, Electrical and Electronic Engineering, Energy (signal processing), Civil and Structural Engineering, Heat pump
الوصف: The objective of this study is to improve the applicability and efficiency of the gas engine driven heat pump with energy storage system when supplying heating and cooling to the different types of buildings. The physical models of four types of buildings, including residential, hotel, office and university building, were sampled and simulated by the DesignBuilder software using the weather data of typical weather year in Tianjin. The building cooling and heating load characteristics of the typical air-conditioning day (17/07/2016) and the typical heating day (07/01/2017) was chosen as the research data. It was found that the four types of buildings had different load demand due to the different function and characteristics of the buildings. The control strategy of the gas engine driven heat pump with energy storage system with four modes, such as Mode L, Mode P, Mode F and Mode O, was developed to meet the various building heating and cooling load demand. The simulation results showed that the annual primary energy ratio of the gas engine driven heat pump with energy storage system is about 21.4% (residential), 35.2% (hotel), 23% (office)and 26.6% (university) higher than traditional gas engine heat pump system. And a compared experiment was given, which demonstrated that the simulation relative errors of the university building cooling load, the cooling/heating capacity of the gas engine driven heat pump with energy storage system, fuel-consumption and primary energy ratio were lower than 12%, except the heating load with the relative error of 35.6%. From these results, the gas engine driven heat pump with energy storage system could be used in different types of buildings with a more stable operation characteristic, higher primary energy ratio and more suitable performance. The results presented in this paper is of some reference basis for optimizing the gas engine driven heat pump with energy storage system and developing a new route for raising cooling/heating quality, energy saving and consumption reducing.
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