The use of VRF system and insulation in building envelope are both considered as promising option to reduce energy consumption of a building. This study analysis energy saving potential of VRF system and building insulation using modelling and simulation of a typical office building. The model office building is simulated with the weather of Hyderabad, Sindh, Pakistan using EnergyPlus building simulation software. The simulation cases include conventional and VRF air conditioning systems with and without insulation to evaluate and compare the annual cooling and energy savings and payback period. Results showed that by replacing conventional air conditioner with VRF AC electrical power can be reduced by 42-45%. It is also noted that Cellulose, expanded polystyrene, extruded polystyrene and polyurethane insulations can save around 49.5, 51.4, 51.6, and 54.54% of electricity, respectively. In the case VRF air conditioner used with Cellulose, expanded polystyrene, extruded polystyrene and polyurethane insulation may reduce electricity consumption by 66.5, 67.4, 67.5 and 68.9 %, respectively. The payback period varies from 7 to 15 months. However, cellulose with VRF air conditioner has the least payback period of around 7 months. The longest payback period of around 15 months was noted for the un-insulated office building with VRF air conditioner. Despite having longer payback period, the combination of polyurethane insulation with VRF air conditioning system is the most efficient combination.
This study presents a detailed energy analysis of a Combined Cooling and Power (CCP) plant operated by Parabolic Trough Solar Collectors (PTSCs). The integrated cycles; Vapor Absorption Refrigeration Cycle (VARC) and Organic Rankine Cycle (ORC) are used to produce cooling and power, respectively. Six organic working fluids, namely, R113, R141b, R123, R245fa, R142b, and isobutane were selected for ORC, while LiBr-H2O solution used in VARC. Four key energetic parameters, useful heat gain, work output, cooling rate, and energy utilization factor (EUF) were examined during varying direct normal irradiance (DNI). A parametric study was carried out in three modes of operation, power only, combined power and cooling and cooling only under the limits of DNI from 0.6 kW/m2to 0.88 kW/m2recorded on the yearly-average basis in two cities of Pakistan, Lahore, and Quetta respectively. Results enunciated that R113 given the highest thermal efficiency of 17.12%, while isobutane gave the least thermal efficiency of 7.88%, hence R113 was chosen as organic working fluid for further study. The maximumEUF was found in the cooling mode of operation which increased from 63.95% to 66.79% at 0.6 kW/m2 and 0.88 kW/m2 respectively. During the combined cooling and power mode, maximum cooling rate, power output, and EUF were 3456 kW, 822.5 kW, and 41.34% respectively at 0.88 kW/m2.
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