| The diversified forms of indoor ventilation in northern areas of severe cold climate have become a worldwide hotspot in recent years.Based on traditional solar fresh air ventilator,this paper designed and created phase change energy storage-solar photovoltaic solar thermal integration(PVT)system which combined the solar fresh air system,the phase change energy storage system,the PV system,solar domestic hot water systems.When the sunlight is adequate in winter,the fresh air heated by the PVT system transferred heat with phase change energy storage system and then transported into indoor air.However,when sunlight is not adequate and fresh air heated by the PVT system cannot reach the set point of supply air temperature,the material in the phase change energy storage system heated fresh air by solidification.Besides,the electricity consumption by the PVT system can totally be provided by itself through photovoltaic power generation,which can save energy and reduce the operating cost.There are some other advantages:the high integrated level of system,the simple process of production and installation.The PVT experimental platform was built up by following processes.Firstly,the monocrystalline silicon solar panels by size of 1650mmx992mm were chose as heat collector and the capillary network by interval of 20mm was combined with thermal grease and rubber insulation cotton to establish the solar heat water system.Secondly,the PV system was constituted by 110Ah battery and 12V controller.Thirdly,Pure decanoate was used as the phase change material and the pumice was added to improve the thermal conductivity of the material.The materials are packaged by 200mm diameter PE pipes and plexiglass cover in which 24 holes with diameter of 20mm were shocked and inserted the PET tubes of same diameter.Then the solar radiation and hot water circulation loop temperature of summer condition has been tested.When the max solar radiation is 996.7w/m2,the max temperature of water is 42.1β.By controlling the flow of water at the outlet and water temperature of inlet to test the water temperature of outlet,when the flow of water was respectively at 1 L/minγ3 L/min and 5 L/min,the average absorption efficiency of the solar system was 32.06%,44.46%and 53.03%and the system power generation efficiency was 6.37%,7.27%and 7.67%.In winter,the test period was from 9:00 to 20:00 and the outlet velocity of fresh air was 1.5m/s,the outdoor fresh air was heated at maximum of 33 β.After getting through the phase change energy storage device,the temperature became stable at around 22β and the fluctuation was small.The 3-D simulation model of the phase change energy storage and the PVT system was established.By compiling the transient UFD of solar radiation and inlet temperature,the test conditions were simulated in 3-dimension.It turned out that the simulating experimental results have the consistent trend and similar values within a deviation of 5%.The calculating method was proper and the simulating results were reliable.By changing the ways of package and the numbers of internal heat-exchanging tubes of the phase change energy storage model,the simulation was optimized.It is found that the melting rate of inside package is 45.37%more as fast as that of outside package.When the number of heat-exchanging tubes increased from 1 to 24,the complete melting time reduced from 6500s to 1500s.Compared to traditional fresh air heat exchange system,phase change energy storage-solar photovoltaic and solar thermal integrated system has more functions.And it can provide with the fresh air and domestic hot water with stable and suitable temperature which can satisfy the demand of comfort.Besides,the system does not require an external power supply and has a good energy-saving effects.It can solve the incompatibility between the demand of comfort,energy saving and environment protecting and provide new ideas and directions on providing the fresh air and domestic hot water in in northern areas of severe cold climate. |
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