Abstract
Indoor solar-heating systems that use ventilated roofs have drawn attention in recent years. The effectiveness and efficiency of such air-heating systems vary depending on the design and operation methods. In Japan, by introducing outside air into a ventilated roof cavity and circulating the air indoors, systems that simultaneously obtain ventilation, solar heating, and heat-storage effects have been actively developed. The conventional systems intake a large volume of outside air to increase the solar heat collection effect. However, there is a risk of heat loss and over-drying when a large amount of cold dry air during winter is introduced. In this paper, plans are presented for improving these solar heating and heat-storage effects by preventing over-drying using indoor air circulation via ventilated cavities in the roof and indoor wall. By comparing the results of the proposed system with those of the conventional system via numerical simulation, the heating load is found to be reduced by 50% or more by circulating indoor air to the ventilated roof and storing the heat in the indoor wall. Moreover, an increased relative humidity of approximately 10% was confirmed by reducing the intrusion of the outside air and keeping the moisture indoors.
Highlights
The use of renewable energy is urgently needed to conserve energy use in homes.Technology using air circulation in ventilated cavities has been actively researched to directly utilize solar heat for indoor heating and hot water
(3) the indoor air receives the heat stored in the indoor heat-storage wall from the daytime heat collection operation, and (4) the air is returned to the room
Addithe heat-storage effect was reduced via heat loss when the air was blown into the space tionally, the heat-storage effect was reduced via heat loss when the air was blown into the under the floor to store heat
Summary
The use of renewable energy is urgently needed to conserve energy use in homes. Technology using air circulation in ventilated cavities has been actively researched to directly utilize solar heat for indoor heating and hot water. The authors have reported a novel system capable of passive dehumidification and radiative cooling during hot and humid summer months alongside solar heat collection and humidity control during cold and dry winter months using roof-ventilated cavities and indoor air circulation [14,15]. Research on design and performance evaluation, which can be effectively applied to an actual building in combination with other architectural elements, such as floor spaces and storage methods of heat collected by solar heat, should be continued. A conventional system that collects solar heat by introducing a large amount of outside air into the roof ventilation layer and collects solar heat to store it in the space under the floor is referred to as a Type N system, and one that reduces the volume of outdoor air and introduces it into a ventilated cavity is a Type A system.
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