How can a solar water heater heat without the sun?

When there is no sun, we can use electric heating. Now solar water heaters have been equipped with electric heating function. When there is no sun, we can set the manual heating and automatic heating modes through the instrument.

The advantage of this is to save electricity, especially for single-cabin solar energy on the market at present, but the big disadvantage is that the capacity of single-cabin solar energy is too large, and the capacity is basically above 150L, so the heating time is too long, and the hot water may take 1 hour or even 2 hours to be used, and if it is not used up, it will be cold the next day, which is a serious waste.

Extended data:

There are two main ways to use solar energy to generate electricity:

① Optical-thermal-electrical conversion. That is, using the heat energy generated by solar radiation to generate electricity. Generally, solar collectors are used to convert the absorbed heat energy into working medium steam, and then the steam drives the gas turbine to drive the generator to generate electricity. The former process is photothermal conversion, and the latter process is thermoelectric conversion.

② photoelectric conversion. Its basic principle is to directly convert solar radiation energy into electric energy through photovoltaic effect, and its basic device is solar cell.

Photochemical utilization: This is a photoelectrochemical conversion method that uses solar radiation energy to directly decompose water to produce hydrogen.

Photobiological utilization: the process of converting solar energy into biomass through photosynthesis of plants. There are mainly fast-growing plants (such as firewood forests), oil crops and giant algae.

Baidu encyclopedia-solar water heater