Various forms of combining parts of the invention , by which water in multi - stage recirculating water - heating tank for collector and / or multi - stage confluent water - heating tank , as a whole or separately , can be heated by solar energy collector , or a heat pump , or an electrical heater , fall into the following categories : on sunny day , it ' s enough to use the solar energy collector to heat water , then hot water is stored ; in confrontation with off - peak electricity at night , use the heat pump or the electrical heater to heat water , then hot water is stored ; during the time of a cloudy day without off - peak electricity , use the heat pump to instantly heat water according to the storage capacity of predetermined amount of produced hot water , then hot water is stored 所述的经太阳能集热器、或热泵、或电加热装置同时或分别对集热器循环加热水箱、分级加热式汇流热水箱中的水进行分级加热的组合包括:阳光天可全部采用太阳能集热器进行加热和储存热水，夜间峰谷电时段可采用热泵或电加热装置进行补充加热和储存热水，无阳光的非峰谷电时段可根据定量的热水储量设置需求采用热泵进行即时加热和储存热水。
Similarly , the net radiation on a cloudy day is mainly used up evaporation of soil . the integrated value of soil heat flux is negative on a cloudy day and that shows the soil emits the heat , which is different on a clear day . in short , average latent , sensible and soil heat flux is 67 % , 21 % and 6 % of net radiation respectively 在裸地下垫面时，晴天潜热占到净辐射的60 ，显热交换只占到19 ，在阴天净辐射同样主要消耗于土壤蒸发，与晴天不同的是在阴天土壤热通量积分值小于零，表明土壤在向外释放热量；平均状况下，潜热、显热和土壤热通分别占到净辐射的67 、 21和6 。
