How to build your own solar water heater

A solar water heater is a device for capturing solar energy for providing hot water for various uses: health, extra heating, pool, etc..

This type of heating can usually complete your water heating needs if you are using other energy sources (electricity, heating oil or gas), and under certain conditions, it can replace them completely.

Solar energy is completely renewable, replacement is effective in limiting emissions of greenhouse gas emissions or nuclear waste, this is why the installation of such devices is strongly encouraged.

The solar water heater

Solar water heating system

Solar water heating system

A solar water heater is a device for heating water, which can replace or supplement the electric and other energy systems for heating water to provide users with substantial savings on their energy bills on their hot water needs.

In Western Europe, a solar water heater allows for approximately two thirds (66%) saving on hot water needs.

It is also a system to respond effectively to limit emissions of greenhouse gas emissions or nuclear waste, which contributes to safeguarding the global environment.

Capturing solar energy

A solar collector (1) includes:

• a plate and black metal tubes. They are the absorber. It is the heart of the “solar system”, which receives solar radiation and heats up;
• a rigid and thermally insulated container around the solar absorber. Its upper part is made of glass or heavy plastics, it is sort of like windows, it lets in the sun and retains heat like a small greenhouse.
This assembly is usually placed on a roof.

Heat transportation

It is the role of the primary circuit (2).

Waterproof and insulated, it contains water mixed with antifreeze. This liquid is heated by passing through the sensor tube, and goes to a storage tank.

Give solar heat to the cold water

There, through a heat exchanger (coil), it transfers its solar heat to the water (3).

The primary liquid, once it has been cooled, moves towards the solar collector (4), where it is heated again as long as the sun is still effective.

Storing hot water

The solar tank (5) is a well-insulated metal tank. It is your hot water reserve. When the hot water is drawn off, it is immediately replaced by the same amount of cold water from the network (6), that cold water is then heated by the solar water heater system.

Circulation of the primary liquid

The liquid circulation can be natural or forced:

• In the first case, the liquid coolant circulates through the density difference with the water tank. As long as the water is warmer and therefore less dense, it moves up naturally by thermoregulation. The hot water tank must therefore be placed above the solar collector. It is on this principle are designed the “thermosiphon” solar water heaters;
• In the second case, a small electric pump, the pump circulator (7), moves the coolant when it is warmer than what is in the water tank. Its operation is controlled by a regulator device (8) exploiting the differences in temperature if the probe (10) in the reservoir is warmer than the hot water sensor (9), the regulator cuts the water circulation. Otherwise, the circulation is restarted and the primary liquid heats the domestic water tank.

The shortage of sunshine

Everywhere, one must cope with bad weather (winter-season, long period of cloudy weather). Under those conditions solar energy cant provide all the hot water needs. The water tank therefore must be equipped with a second source of water heating that takes over when needed. These may include:

• resistance (electric boost), often placed at mid-height of the solar tank;
• a coil (11) (hydraulic booster) connected to a secondary tank (12), heated by gas, oil, or wood, located downstream of the main water reservoir.
A second tank equipped with an electric heater can also used as booster.

For more information on how to build your own solar water heater, click here.

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