Air conditioning system is used for various application, in passenger car it gives comfort to the passenger. Now a days huge advancement have been included in the air conditioning system, especially ...automatic air conditioning system plays a vital role in passenger car. These air conditioning systems are performing well and have the capability of maintaining the temperature for long time with energy consumption. However, in some vehicle the performance of these air conditioning system is not achieved, while some vehicle achieved better performance. In later study it is found that, the structure of vehicle body also influence the performance of air conditioning system. In some structure the air conditioning air-flow a long distance in short time and have the capability to enhance the air conditioning performance. It is also found that the air conditioning performance can be improved by the structure of vehicle body. In this paper, we considered an Indian small budget car. The structure of the car is slightly modified and replaced the position of the air conditioning outlet. Then the residual temperature inside the car is analyzed with and without air conditioning. Here the CFD is used to analysis the temperature inside car at various position.
•Various combinations of liquid desiccant air conditioning systems are discussed.•Developments in liquid desiccant dehumidifier and regenerator are reviewed.•Properties and developments of desiccant ...materials are reviewed.•Mathematical models of dehumidifier and regenerator are explained.•Performance control techniques and effect on indoor air quality are discussed.
Air conditioning (AC) systems demand a significant portion of the total energy consumed by the building sector. Conventional AC based on vapor compression refrigeration (VCR) is neither energy efficient nor environment-friendly due to its method of humidity control and use of refrigerants with global warming potential respectively. Liquid desiccant air conditioning system (LDAS) is a promising alternative to VCR. This review provides a comprehensive overview of the developments in LDAS so far. It explains the principle of operation and classification in detail. The various developments in dehumidifier, regenerator, desiccant material, and mathematical modelling are discussed. The various types of performance parameters, and the design criteria and effect of operating parameters are also detailed. Finally, the climate feasibility, performance control strategies and indoor air quality are explained. This communication will be useful to identify the research gaps to explore new pathways for future research to further improve the efficiency of LDAS.
•A transcritical CO2 air conditioning system was developed for use in a railway vehicle.•The model predictive control strategy was used to optimize the system performance.•The proposed control method ...maximized the real-time COP without sacrificing comfort.•The simulation results showed that the proposed control strategy is effective.
This paper presented a model predictive control strategy to optimize the operation of the transcritical CO2 air conditioning system used in railway vehicles, which had to balance the needs of the passengers' comfort with energy-saving effects. In this work, the discharge pressure and evaporator air volume flow rates were optimized while maintaining comfort using a multi-variable control technique called model predictive control strategy. The objective function and the predictive model, which were proposed in this work combining data and physical laws, were the basis for the model predictive controller's ability to foresee future operation-conditions and calculate the optimal inputs. The validation results showed that the prediction error was less than 4.5%. The model predictive controller was adopted in GT-SUITE platform to realize the real-time maximization of the energy efficiency and maintain comfort requirement by adjusting discharge pressure, evaporator air volume flow rate and compressor speed. The simulation was conducted under fixed conditions and realistic conditions. As for the fixed conditions, the coefficient of performance achieved at 2.24, equaling to the maximum value of the map. Under the realistic conditions, the overall energy consumption of the control method using the MPC strategy was lower than that using the PID control strategy, and the average COP was increased by 7.4%. Further, there was a 1% error in coefficient of performance between the extreme value gained by the model predictive control method and the extreme value offered by the map method, which validated that the model predictive control strategy can be an effective control method for the optimal operation of the transcritical CO2 air conditioning system.
The HVAC systems utilizing renewable energy sources are one of the main contributors towards the fossil fuel dependency reduction. Among these, the ground source heat pump systems, especially those ...based on vertical ground heat exchanger, are very attractive, due to their high efficiency.
The size of the systems depends on the building (geometry, construction materials, orientation etc. but also usage and internal gains), on the ground thermophysical characteristics, on the climatology of the area and on the ground heat exchanger design and construction. As a result, the ground heat exchanger length required for heating may result significantly different from the one required for cooling. In this work, the ground heat exchanger lengths required for heating and cooling are calculated for two model-buildings, a residential and an office one, located at 40 different Greek cities, covering a wide range of country’s climate conditions. Assuming that a ratio of these lengths in the 0.8–1.2 range is required for efficient long-term operation of the autonomous GSHP system with minimum installation cost, the results suggest that autonomous systems may be used in areas with the heating degree-days in the 800–950
K-days range. In hotter climates with less than 800 heating degree-days, the GSHP system should be supplemented by a conventional cooling system, while in colder climates with more than 950 heating degree-days a conventional heating system supplement is required.
•For hot and humid climates, development of novel DACS.•Analysis of DACS using complete waste heat from the condenser (Mode-I).•Analysis of DACS using rod (electric heater) heat (Mode ...-II).•Optimization and performance comparison of ACS and DACS using Mode-I and Mode-II.
A desiccant air conditioning system is considered a capable alternative to a conventional air conditioning system because of its independent control of temperature, humidity and being eco-friendly. Also, to resolve the problem of more energy consumption for the restoration of a desiccant, structures comprising of desiccant can utilize thermal energy or complete waste heat to revive desiccant material. Therefore, this research work executes an experimental, optimization and comparative examination for conventional and desiccant air conditioning systems regenerated by two different modes, i.e. firstly using (Mode-I) complete waste heat from condenser and secondly using (Mode-II) rod (electric heater) heat for regeneration at different process air inlet temperatures, i.e. (28, 29.5, 31, 32.5, 34, 35.5 and 37 °C), at different process air inlet velocities, i.e. (1.5, 2.5, 3.5 and 4.5 m/s) and a fix (2.5 m/s) regeneration air inlet velocity. Thus, optimization of performance parameters, i.e. VCOP, ECOP, dehumidification effectiveness, moisture removal capacity (kg/hr), DCOP, regeneration effectiveness and regeneration rate (kg/hr), is identified for achieving maximum efficiency of conventional and desiccant air conditioning systems under the above operating conditions.
Display omitted Cooling based dehumidification, Desiccant based dehumidification
Methodology for Desiccant air conditioning system using Mode-I and Mode-II for regeneration
Natural ventilation is crucial for reducing the energy consumption and carbon emissions of buildings. However, it is often impossible to meet indoor thermal requirements in hot climates. In this ...study, an integrated natural ventilation system with an underground pipe gallery for pre-cooling and a built-in chimney to enhance the thermal pressure was proposed to cool a computer room. A full-scale experimental platform was constructed to confirm the feasibility of the system. The system performance was investigated by comparing two experimental scenarios, thermal pressure-driven natural ventilation and fan-assisted ventilation, during the transition season in a hot outdoor environment. The underground pipe gallery pre-cooled chimney ventilation system effectively provided a suitable indoor environment for the occupied area, with a mean temperature of 29.1 °C and relative humidity of 57.6 %. The proportion of hours in which the hourly average temperature around the server rack meets the Class C level for computer rooms specified in the national standard is 66.7 %. The maximum pre-cooling capacity of the underground pipe gallery was 3.5 kW. When the assisted fan was operated, the environmental stability of the equipment area further improved, and the system had the potential to operate continuously for 24h to provide a suitable indoor environment.This study provides a strategic solution to passive building design by demonstrating the viability of using an underground pipe gallery for pre-cooling in natural ventilation systems.
•It was shown that PV based air conditioner can save about $700.00 in energy consumption with a payback in 3.7 years.•The COP for the PV based air conditioner is about 2.6 while the COP for ...conventional unit is 2.9.•The PV based air conditioner is viable in Piaui, Brazil due to high and stable incident solar radiation.•The PV based air conditioner proved to be stable at times of great cooling demand.•The PV based air conditioner can substitute satisfactorily conventional units in hot regions.
Globally the building sector is responsible for a big share of electric energy consumption and emissions. To alleviate these impacts it is necessary to improve the energy efficiency besides implementing renewable energy sources for building sector sustainability. PV panels for generating electric energy are most preferred by the sector. In the present study, two similar rooms were prepared one with a conventional air conditioner of the window type powered from the grid and the other is powered from PV panels. The heat load was calculated and used to define the conventional air conditioner and also to define the area of photovoltaic solar panels and the associated equipments to install a PV circuit for supplying electric energy to the PV air conditioner. Both rooms were equipped with calibrated instrumentation including thermocouples to measure the temperature distribution in rooms as well as electric energy consumption during the experiments. Ambient temperature, wind speed, temperature in the vicinity of the photovoltaic panels, humidity, solar radiation, voltage, current, flow of energy consumed by the systems were measured and registered by data acquisition system. Experiments were carried out with the systems working simultaneously at pre-defined times. The solar PV-based air conditioner consumed approximately 342 kWh during 30 days of experiments, while the air conditioner connected to the grid, consumed about 330 kWh, which is 5 % less than the solar PV air conditioner confirming that solar PV air conditioner is viable. The COP for the solar-based air conditioner is about 2.6 and the COP for conventional air conditioner is 2.9. The incident solar radiation is high and stable in Teresina, Piauí, Brazil which ensures viability of the solar PV air conditioner. The power supply from CC showed better quality and costs an AC system, and that PV System can save about $700.00 in energy consumption and the payback occurs in 3.7 years.
•A heat pump AC system is designed for the target vehicle.•Evaporation/condensation temps are systematically studied.•Impact of evaporation temp on air outlet temp is analyzed.•Experiments test ...system performance compared with design performance parameters.
This study explores the potential of heat pump air conditioning systems in enhancing the driving range of electric vehicles (EVs) by optimizing evaporator and condenser temperatures to achieve improved system performance and efficiency. A novel methodology is introduced to determine the optimal temperatures for evaporation and condensation within such a system, seamlessly integrated with a primary return system. The validity of this approach is substantiated through rigorous experimental validation. Under New European Driving Cycle (NEDC) conditions, the heat pump air conditioning system demonstrates superior performance and reduced energy consumption, with optimal evaporator temperatures ranging from −2 °C to 2 °C and condenser temperatures between 57.1 °C and 61.8 °C during summer. Winter conditions are optimized with evaporator temperatures from −16 °C to −12 °C and condenser temperatures between 42.4 °C and 48.8 °C. Additional experiments were conducted to validate system performance in both cooling and heating modes. The results highlight a close alignment between the theoretical model for the primary return air system and actual performance, with less than a 10 % discrepancy in calculated outlet temperatures compared to experimental data across various operating conditions. This correlation validates the theoretical model’s capacity to accurately reflect real-world system behavior.
•Challenges of optimal control for active storages for fast DR are addressed.•The linear state-space model is developed for online MPC control.•Simplified parameter identification and self-correction ...for the MPC are developed.•Both expected power reduction and acceptable indoor environment are satisfied.•Cooling discharging rate of storages and chiller power demands are optimized by MPC.
Demand response (DR) can effectively manage electricity use to improve the efficiency and reliability of power grids. Shutting down part of operating chillers directly in central air-conditioning systems can meet the urgent power reduction needs of grids. But during the special events of fast DR, how to optimally control the active cold storage considering the indoor environment of buildings and the needs of grids at the same time is rarely addressed. A model predictive control (MPC) approach, with the features of shrunk prediction horizon, self-correction and simple parameter determination of embedded models, is therefore developed to optimize the operation of a central air-conditioning system integrated with cold storage during fast DR events. The chiller power demand and cooling discharging rate of the storage are optimized to maximize the building power reduction and meanwhile to ensure the acceptable indoor environment. Case studies are conducted to test and validate the proposed method. Results show that the proposed MPC approach can effectively handle the optimal controls of cold storage during DR events for required power reduction and acceptable indoor environment. Due to the feedback mechanism of MPC, the control performance is not negatively influenced by the simplified parameter identification of models, which will be convenient for real applications. While achieving the expected building power reduction for the power grid, the indoor environment is effectively improved in the DR events using the MPC and the maximum indoor temperature is reduced significantly without extra energy consumed.
The purpose of the air conditioning system (A/C system) is to meet the cooling capacity needs of individual rooms. In order to optimize energy-saving in the A/C system, it is essential to conduct a ...study on the operational status of various equipment, considering the comfort demand of the human body and dynamic electricity prices. This feature will enable collaborative control of the A/C system. Consequently, this paper presents a two-stage operational optimization strategy. Firstly, the comfort requirement is taken into consideration, and the room's set temperature is treated as a decision variable. An optimization strategy is proposed to meet real-time electricity prices and indoor cooling demand. Furthermore, by optimizing the cooling demand, the operation of the main equipment in the A/C system is also optimized, leading to the derivation of an optimal cooling strategy at the minute level. According to this strategy, there are significant reductions in the energy consumption and the carbon emission relative to the rated operating conditions at each time period. The energy consumption can be reduced by up to 4.11%, and the carbon emission can be reduced by up to 30.81%.
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