Renewable Energy Resources and Technologies
Hadi Farzan
Abstract
Recently, novel techniques have been developed in building industries to use solar heating and cooling systems. The current study develops a Solar-powered Heating and Cooling (SHC) system for an office building in Kerman and assesses the transient dynamics of this system and office indoor temperature. ...
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Recently, novel techniques have been developed in building industries to use solar heating and cooling systems. The current study develops a Solar-powered Heating and Cooling (SHC) system for an office building in Kerman and assesses the transient dynamics of this system and office indoor temperature. To this end, TRNSYS simulation software is utilized to simulate system dynamics. The developed system comprises Evacuated-Tube solar Collectors (ETCs), heat storage tank, heat exchanger, circulating pumps, axillary furnace, cooling tower, single-effect absorption chiller, and air handling unit. The office indoor temperature is assessed in two scenarios, including commonly-insulated and well-insulated envelopes, while window awnings are used to prevent the sun from shining directly through the windows. The results illustrate that the SHC system can meet the thermal loads and provide thermal comfort in line with ASHRAE standards. The indoor temperature reaches 21 °C and 24 °C on cold winter and hot summer days by using the SHC system; however, without the SHC system, the indoor temperature experiences 15 °C and 34 °C on cold and hot days, respectively. The SHC system provides 45 °C and 15 °C supply air on cold and hot days to keep the indoor temperature in the desired range. A thermostat monitors the indoor temperature and saves energy by turning off the system when no heating or cooling is required. Furthermore, the ETCs can run the SHC system for a long time during daytime hours, but the axillary heater is still essential to work at the beginning of the morning.
Advanced Energy Technologies
Ehsan Hasan Zaim; Hadi Farzan
Abstract
Utilizing thermal storage units such as Phase Change Materials (PCMs) is a suitable approach to improving Solar Air Heaters (SAHs). The present study tries to assess the effects of PCM mass values on the heat dynamics and thermal performance of SAHs. To this aim, an analytical thermodynamic model was ...
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Utilizing thermal storage units such as Phase Change Materials (PCMs) is a suitable approach to improving Solar Air Heaters (SAHs). The present study tries to assess the effects of PCM mass values on the heat dynamics and thermal performance of SAHs. To this aim, an analytical thermodynamic model was developed and validated by available experimental data. This model provides a robust numerical framework to model the phase change phenomenon and analyze the heat dynamics and thermal performance of SAH using various PCM masses. Four scenarios were considered using the developed analytical model including SAHs using 0, 30, 60, 90 kg PCM. The obtained results illustrated that the maximum outlet temperature was reduced, approximately near 20 %, by increasing the PCM mass between 0 and 90 kg; however, heating time was extended to periods when solar energy availability was inadequate. The thermal performance improved by nearly 14.5 % in the SAH using 90 kg PCM mass compared to the SAH without using PCM. The thermal performance of the SAH with 90 kg PCM was slightly higher than the SAH using 30 kg of PCM; hence, a significant portion of stored thermal energy was lost during nighttime through heat exchange with ambient surroundings. The obtained results also showed that despite available latent thermal energy, the outlet air temperature profiles for the SAHs using different PCM mass were close after sunset due to the low thermal conductivity of paraffin.
Renewable Energy Resources and Technologies
Hadi Farzan
Abstract
The present study investigates the effectiveness of thermostat control strategy in cooling energy consumption in residential buildings. To evaluate the energy consumption, two scenarios including a residential zone with and without the thermostat control system are assumed. The TRNSYS software provides ...
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The present study investigates the effectiveness of thermostat control strategy in cooling energy consumption in residential buildings. To evaluate the energy consumption, two scenarios including a residential zone with and without the thermostat control system are assumed. The TRNSYS software provides an efficient numerical tool to model and evaluate a cooling system. Furthermore, since solar-powered cooling systems for residential air-conditioning are receiving growing and significant interest, a hot-water fired absorption chiller coupled with evacuated tube collectors is considered as the cooling system. The results reveal that the cooling systems consume a large amount of energy in hot climate zones without employing the thermostatic control. Therefore, cooling energy has great potential for a significant saving in hot climates. It is illustrated that the thermostat strategy has an obvious impact on such energy saving. In the current study, employing the thermostat in 90m2 residential building results in saving energy by up to 36%.