A passive night-sky radiation system

[摘要] ENGLISH ABSTRACT: A passive night-sky radiation cooling system consists of a radiation panel anda cold water storage tank. The stored cold water may be used to cool a roomduring the day time, particularly in summer. In this thesis a theoretical andmathematically sound simulation model is developed. An experimental set-upwas constructed and subsequently used to show that the theoretical modeleffectively simulates the transient heating or cooling response of the system.It is shown that under South African conditions the typical heat emitting rateduring the night is 55 W/m2. After the heat has been removed from the water,it is stored in a cold water tank from where it is circulated through a naturalconvector during the day time to absorb heat from the room. The experimentextracted a minimum of 102 W/m3 of heat from a 1.87 m3 galvanized steel roomwhile a brick room with a volume of 120 m3 requires 22.7 W/m3. Additionalto cooling, the system during the day, absorbed an average of 362 W of energyand heated 68 l of water from 24 °C to 62 °C within an 8-hour period. Thesystem achieved similar results during winter conditions and the experimentconfirms that the system is capable of operating without a control system.Therefore it is recommended that renewable energy-conscious designers paymore attention to the use of night-sky radiation cooling in future.

[发布机构] Stellenbosch University