scholarly journals Control-oriented model for air-based BIPV/T systems

2021 ◽  
Vol 2069 (1) ◽  
pp. 012221
Author(s):  
A M Sigounis ◽  
E D Rounis ◽  
A K Athienitis ◽  
C Vallianos
Keyword(s):  
Air Conditioning ◽  
Control Strategies ◽  
Simulation Models ◽  
Hvac System ◽  
Flow Rates ◽  
Heat Utilization ◽  
Systems Model ◽  
Air Temperatures ◽  
Building Integrated Photovoltaic ◽  
Mass Flow Rates

Abstract This study presents the development of a control-oriented model for Building Integrated Photovoltaic Thermal (BIPV/T) systems. Model-based control strategies could optimize their coupled operation with the building Heating Ventilation and Air-Conditioning (HVAC) system and maximize the heat utilization. Two transient simulation models (1st order and 2nd order) are developed using Python, validated with experimental data and compered to each other. Finally, simulation results are presented where the range of possible outlet air temperatures for different mass flow rates are identified.

Nonlinear Control of an Air Handling Unit Using Feedback Linearization

2009 ◽  
Author(s):  
Hamed Moradi ◽  
Majid Saffar-Avval
Keyword(s):  
Air Conditioning ◽  
Feedback Linearization ◽  
Hvac Systems ◽  
Pi Controller ◽  
Hvac System ◽  
Flow Rates ◽  
Air Handling Unit ◽  
Transfer Rules ◽  
And Control ◽  
Dynamic Variables

Heating, ventilation and air conditioning (HVAC) systems are equipments used to maintain satisfactory comfort conditions in buildings. Also, energy consumption of ventilated buildings highly depend on the design, performance and control of HVAC systems. In this paper, nonlinear model of a multi-variable HVAC system is considered in which the control inputs are the air and cool water flow rates. Using thermodynamics and heat transfer rules, differential and consequently state space equations of the system are represented. To achieve a good performance, dynamic variables such as output temperature and relative humidity must be controlled. Using input-output feedback linearization, a PI controller is designed. It is shown that by applying the controller, system tracks from one operating point to another with an appropriate specification of time response. In addition, using feedback linearization guarantees robustness of the system against the parametric uncertainties associated with dynamic model.

scholarly journals A Fuzzy Control Strategy Using the Load Forecast for Air Conditioning System

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 530 ◽  
Author(s):  
Jing Zhao ◽  
Yu Shan
Keyword(s):  
Energy Consumption ◽  
Fuzzy Control ◽  
Control Strategy ◽  
Air Conditioning ◽  
Control Strategies ◽  
Hvac Systems ◽  
Hvac System ◽  
Pump System ◽  
Heat Pump System ◽  
Load Forecast

The energy consumption of air-conditioning systems is a major part of energy consumption in buildings. Optimal control strategies have been increasingly developed in building heating, ventilation, and air-conditioning (HVAC) systems. In this paper, a load forecast fuzzy (LFF) control strategy was proposed. The predictive load based on the SVM method was used as the input parameter of the fuzzy controller to perform feedforward fuzzy control on the HVAC system. This control method was considered as an effective way to reduce energy consumption while ensuring indoor comfort, which can solve the problem of hysteresis and inaccuracy in building HVAC systems by controlling the HVAC system in advance. The case study was conducted on a ground source heat pump system in Tianjin University to validate the proposed control strategy. In addition, the advantages of the LFF control strategy were verified by comparing with two feedback control strategies, which are the supply water temperature (SWT) control strategy and the room temperature fuzzy (RTF) control strategy. Results show that the proposed LFF control strategy is capable not only to ensure the minimum indoor temperature fluctuations but also decrease the total energy consumption.

scholarly journals Night air conditioning of buildings by external air ventilation

2018 ◽  
Vol 27 (48) ◽  
pp. 35-47
Author(s):  
Debrayan Bravo-Hidalgo
Keyword(s):  
Energy Demand ◽  
Air Conditioning ◽  
Thermal Mass ◽  
Reliable Prediction ◽  
Flow Rates ◽  
Air Temperatures ◽  
Energy Flows ◽  
Air Ventilation ◽  
Bibliographic Search ◽  
Almost All

Buildings contain the environment in which almost all human activities take place, and therefore, nowadays, they represent a great sink of energy. Establishing thermal comfort conditions within these buildings is responsible for a large portion of their energy demand. This paper aims at providing a theoretical framework of the performance and the trends in research and implementation of night air conditioning by outside air ventilation. The bibliographic search was conducted in the academic directory Scopus, and the information extracted was processed in the VOSviewer software, through which text mining, map of terms and networks of investigative action were carried out. The literature showed that direct ventilation has a more significant cooling potential in regions characterized by a high difference between day and night air temperatures. The effectiveness of night cooling and the reliable prediction of thermal behavior are strongly related to the model adopted for the convection algorithm. A reliable prediction of heat transfer by convection requires an approach based on computational simulations of fluid dynamics, which are much more demanding in terms of computational power, compared to simulations of the variation of energy flows as a function of time. Most studies showed that the position of the thermal mass is not significant, while the amount of ventilation air is of great importance. In particular, the energy demand for cooling a building decreases sharply if the air flow rates increase.

scholarly journals Night air conditioning of buildings by external air ventilation

2018 ◽  
Vol 27 (48) ◽  
Author(s):  
Debrayan Bravo-Hidalgo
Keyword(s):  
Energy Demand ◽  
Air Conditioning ◽  
Thermal Mass ◽  
Reliable Prediction ◽  
Flow Rates ◽  
Air Temperatures ◽  
Energy Flows ◽  
Air Ventilation ◽  
Bibliographic Search ◽  
Almost All

Buildings contain the environment in which almost all human activities take place, and therefore, nowadays, they represent a great sink of energy. Establishing thermal comfort conditions within these buildings is responsible for a large portion of their energy demand. This paper aims at providing a theoretical framework of the performance and the trends in research and implementation of night air conditioning by outside air ventilation. The bibliographic search was conducted in the academic directory Scopus, and the information extracted was processed in the VOSviewer software, through which text mining, map of terms and networks of investigative action were carried out. The literature showed that direct ventilation has a more significant cooling potential in regions characterized by a high difference between day and night air temperatures. The effectiveness of night cooling and the reliable prediction of thermal behavior are strongly related to the model adopted for the convection algorithm. A reliable prediction of heat transfer by convection requires an approach based on computational simulations of fluid dynamics, which are much more demanding in terms of computational power, compared to simulations of the variation of energy flows as a function of time. Most studies showed that the position of the thermal mass is not significant, while the amount of ventilation air is of great importance. In particular, the energy demand for cooling a building decreases sharply if the air flow rates increase.

Simplification of Simulation Models for Air-Conditioning Controlling System

2017 ◽  
Vol 137 (8) ◽  
pp. 1001-1008
Author(s):  
Tadayoshi Kosaka ◽  
Kazuhiko Koyanagi ◽  
Yasutaka Satake ◽  
Isao Kobayashi ◽  
Nobuhiro Matsudaira ◽  
...  
Keyword(s):  
Air Conditioning ◽  
Simulation Models ◽  
Controlling System

scholarly journals A Multi-Timescale Bilinear Model for Optimization and Control of HVAC Systems with Consistency

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 400 ◽  
Author(s):  
Zelin Nie ◽  
Feng Gao ◽  
Chao-Bo Yan
Keyword(s):  
Optimization Model ◽  
Air Conditioning ◽  
State Of The Art ◽  
Hvac Systems ◽  
Practical Significance ◽  
Hvac System ◽  
Bilinear Model ◽  
Optimization And Control ◽  
And Control ◽  
Slow Timescale

Reducing the energy consumption of the heating, ventilation, and air conditioning (HVAC) systems while ensuring users’ comfort is of both academic and practical significance. However, the-state-of-the-art of the optimization model of the HVAC system is that either the thermal dynamic model is simplified as a linear model, or the optimization model of the HVAC system is single-timescale, which leads to heavy computation burden. To balance the practicality and the overhead of computation, in this paper, a multi-timescale bilinear model of HVAC systems is proposed. To guarantee the consistency of models in different timescales, the fast timescale model is built first with a bilinear form, and then the slow timescale model is induced from the fast one, specifically, with a bilinear-like form. After a simplified replacement made for the bilinear-like part, this problem can be solved by a convexification method. Extensive numerical experiments have been conducted to validate the effectiveness of this model.

scholarly journals Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Tobias Blanke ◽  
Markus Hagenkamp ◽  
Bernd Döring ◽  
Joachim Göttsche ◽  
Vitali Reger ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Circular Ring ◽  
Flow Conditions ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Pipe Radius

AbstractPrevious studies optimized the dimensions of coaxial heat exchangers using constant mass flow rates as a boundary condition. They show a thermal optimal circular ring width of nearly zero. Hydraulically optimal is an inner to outer pipe radius ratio of 0.65 for turbulent and 0.68 for laminar flow types. In contrast, in this study, flow conditions in the circular ring are kept constant (a set of fixed Reynolds numbers) during optimization. This approach ensures fixed flow conditions and prevents inappropriately high or low mass flow rates. The optimization is carried out for three objectives: Maximum energy gain, minimum hydraulic effort and eventually optimum net-exergy balance. The optimization changes the inner pipe radius and mass flow rate but not the Reynolds number of the circular ring. The thermal calculations base on Hellström’s borehole resistance and the hydraulic optimization on individually calculated linear loss of head coefficients. Increasing the inner pipe radius results in decreased hydraulic losses in the inner pipe but increased losses in the circular ring. The net-exergy difference is a key performance indicator and combines thermal and hydraulic calculations. It is the difference between thermal exergy flux and hydraulic effort. The Reynolds number in the circular ring is instead of the mass flow rate constant during all optimizations. The result from a thermal perspective is an optimal width of the circular ring of nearly zero. The hydraulically optimal inner pipe radius is 54% of the outer pipe radius for laminar flow and 60% for turbulent flow scenarios. Net-exergetic optimization shows a predominant influence of hydraulic losses, especially for small temperature gains. The exact result depends on the earth’s thermal properties and the flow type. Conclusively, coaxial geothermal probes’ design should focus on the hydraulic optimum and take the thermal optimum as a secondary criterion due to the dominating hydraulics.

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