Feasibility Study On The Application Of Temperature-Regulating Module Based On Radiative Cooling In Buildings

In recent years,building energy has increased year by year,accounting for about one third of the total energy consumption in China,and about 12% of the energy consumption in building operation comes from refrigeration.With the aggravation of global warming,extreme weather appears more and more frequently,and there is a growing demand for refrigeration.Traditional refrigeration technology not only consumes a lot of primary energy,but also causes a series of environmental problems.The new refrigeration technology driven by renewable energy is relatively complex and the application scope is limited.The recently emerging radiative cooling technology takes outer space as cold source and 8-13 um atmospheric window as channel to discharge heat from the surface of the earth in the form of thermal radiation,which does not require any energy input,but can mitigate the trend of global warming.The combination of radiative cooling technology and buildings generally adopts indirect ways.This method relies on air conditioning system,which still needs a lot of energy and can not make full use of the energy saving potential of radiative cooling.However,the direct combination of radiative cooling and buildings has not been explored yet.Aiming at the problem of increasing indoor heat load,this paper presents a temperature-regulating module which combines PVDF-HFP,a graded porous cooling material reported recently by Science,and solar heat absorption coating.Furthermore,this module was used to build the radiative cooling experimental devices.The cooling experiments in summer and heating experiments in winter are carried out respectively.Finally,the model was built with Energy Plus and Matlab software and the energysaving analysis of the actual buildings with this module in Tianjin,Xi’an and Haikou in summer and winter is carried outThe results show that the infrared emissivity in the atmospheric window and solar reflectivity of the prepared cooling material are 97% and 95% respectively,and the temperature drop below 7 °C can be obtained at high humidity seashore.The net cooling power is about 50 W/m2 in the environment with a temperature of 23 °C and a humidity of about 80%.In summer experiment,when the solar irradiation is 750 W/m2 and the maximum daytime temperature is 33 °C,the maximum air temperature in the building is only 27.5 °C.In addition to providing part of the cooling capacity from noon to afternoon when the solar intensity is high,air conditioning is not needed for the rest of the time.In winter experiment,the temperature-regulating module adopts the solar absorption mode.The indoor temperature can meet the heating requirement during the period of high solar intensity in the daytime,without additional heat supply.The temperature at night is also higher than the indoor temperature under the cooling mode of the temperature-regulating module.In the five-day experiment of simulated heating,the average energy-saving rate of the experimental group with temperature-regulating module in winter is about 18.6% compared with the control group.The simulation results show that in summer,when Tianjin,Xi’an and Haikou adopt the whole roof area temperature-regulating module,the direct energy-saving rate is 39.6%,43.9% and 22.1% respectively,and the theoretical energy-saving rate with cold storage is 86%,83.8% and 74.5% respectively.When 60% of the roof area is used,the direct energy-saving rate is 42.4%,31.9% and 17.9% respectively,and the theoretical energy-saving rate with cold storage is 60.3%,56% and 52.5% respectively.In winter,the theoretical energy-saving rate with heat storage in Tianjin is 21% and 10.1% respectively when using the temperature-regulating module of the whole roof area and 60% of the roof area,while that in Xi’an is 5.7% and 3.7% respectively.The energysaving effect in summer is better than that in winter.