Automatic cycle in cold weather. Because the pipeline temperature is too low, lower than the set defrost temperature. This temperature is the self-protection temperature of solar energy. If it is less than 3 degrees, the pipeline will start to circulate to ensure that the pipeline is working. The pipeline does not freeze or block. A blockage can easily slow down the water supply or slow or even block pipeline flow. If it is frozen and blocked for a long time, it will also cause the pipeline to freeze and block. crack. Therefore, the solar water heater will work automatically when the weather is cold.
Earth's gravity does not increase the gravitational potential energy of water.
For example: ocean water directly or indirectly absorbs energy from the sun, transforms into water vapor and rises to high altitudes to form clouds, leading to increasedation of the gravitational potential energy of water. (i.e. the gravitational potential energy of solar energy converted to water)
Clouds are blown from the ocean towards the land by the wind, and eventually fall to the ground when it rains and return to the sea. Wind forms due to the uneven heating and cooling of the air when exposed to sunlight. Wind energy is therefore also converted from solar energy.
Thus, the energy necessary for the water cycle comes from the sun. The British BBC made a documentary specifically to showcase the solar system. It shows that changes in a river's water flow over the past hundred years are consistent with the cycle of solar activity (such as sunspots and solar flares). I can check it.