Solar water heating
How to Heat Water With Solar Energy, Solar water heaters are called household water heating systems, and they can be used at any time regardless of the climate, and they depend on the sun for their fuel, and there are two types of these solar systems They are the active systems that contain a rotating pump and a controller, and passive systems that do not.  The solar water heater consists of three parts
- Solar collector: It is a device through which solar radiation is absorbed, and this energy is converted into liquid or materials that pass through the collector.
- Medium for the transfer of absorbed energy: The absorbed energy is transferred to the water by means of a thermal conductor, and the quality of this material varies according to the different target to be used.
- Thermal insulated tank: which is coated with an inner layer of copper or steel, and it is worth noting that there are solar heating systems that work at low pressure, and others that work at high pressure ranging from 100 to 600 kPa.
Solar water heating systems
Active Solar Water Heating Systems, there are two types of this system as follows: 
- Direct circulation system: The pump in this system moves the household water in a circular motion through the collector, and it works in a non-freezing climate.
- Indirect circulation system: The pump in this system moves the water that has been transferred to heat in a circular motion through the collector and the heat exchanger. In this process, the water is heated before it flows into the house, and is suitable for use in the freezing climate.
Passive solar water heating systems,
which is less expensive than an active system and more reliable, and may last longer, but it is less effective, and there are two types of it as well. 
The concept of solar energy
solar energy is defined as the radiation from the solar system, through which it can obtain heat and produce electricity, as it is sufficient to cover the world’s energy needs, and it is expected that in the twenty-first-century solar energy will become one of the most important sources of renewable energy As it is inexhaustible and non-polluting to the air, unlike fossil fuels such as coal, natural gas, and petroleum.