Abstract
To date, most of the indoor environment control is based on the dry-bulb air temperature, which is one of the simplified control methods having the limitation to truly represent the thermal comfort of individual occupants. A variety of factors affect the thermal comfort such as dry-bulb air temperature, humidity, air movement, radiation, clothing insulation, and metabolic activity level. In this circumstance, this study investigated the effects of considering hourly metabolic rate variations for predicted mean vote (PMV) control on the actual thermal load, energy usage, and life cycle cost (LCC). The case adopting PMV control taking the hourly metabolic rate into account was comparatively analyzed against the conventional dry-bulb air temperature control, using a detailed simulation technique after the validation process. As a result, when the activity state of the occupant is house cleaning in the summer, the indoor temperature decreases rapidly due to the high amount of activity. It requires a temperature that is 11.7 °C and 9.7 °C lower than the conventional dry-bulb air temperature control method, respectively, and generally forms a higher indoor air temperature than the conventional control method after 7 p.m. This means the difference in temperature to satisfy the comfort of the occupant according to the amount of activity, and during winter as opposed to summer, was found to form a lower indoor air temperature than the conventional temperature control. In case of annual boiler gas consumption, PMV control showed 7.3% less energy consumption than the dry-bulb air temperature control and showed 28.8% less energy consumption than the dry-bulb air temperature control for annual cooling electricity consumption. Considering the cooling and heating energy reduction rate and the initial installation cost of measuring equipment for real-time metabolic rate and PMV measurement, a payback period of approximately 4.15 years was required.
Highlights
In order to solve the limitations of such prior studies, the purpose of this study is to evaluate the thermal comfort of the occupant and the cooling and heating energy saving effect through predicted mean vote (PMV) control considering the actual metabolic rate of the occupant and to enhance the applicability of measuring the metabolic rate for PMV control in Korea through economic analysis (Lifecycle cost)
In case of PMV control, PMVs of the time period in which the occupant is active in the corresponding zone are all located within the comfort zone
The annual cooling and heating energy saving effect of PMV control taking hourly metabolic rate variations into account was evaluated in comparison with dry-bulb temperature control for the indoor environment of a 15-story residential apartment equipped with a radiant floor heating system and window air conditioner, and the life cycle cost (LCC) analysis was performed through the capitalization factor of annuity considering the annual cost, present value of future cash, and discount value
Summary
Many countries regulate indoor space based on dry-bulb air temperature or recommend proper room temperature compliance to reduce energy consumption in buildings. These national policies may have a positive effect on reducing heating and cooling energy consumption, they are fragmentary policies and regulations that do not consider the thermal comfort experienced by the occupants [3]. The thermal comfort conditions of the human body as a whole can be evaluated by means of the PMV index [5,7] which integrates the influence of the thermal comfort factors (air temperature, air velocity, mean radiant temperature, humidity, clothing insulation, and activity) into a value on the well-known ASHRAE
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