With a neat diagrams, explain solar water heating system

Solar Water Heating Systems

Most solar water heating systems consist of two main components:

a solar collector and a storage tank.

1. Solar Collector

The most common type is the flat plate collector, a rectangular box with a transparent cover. It contains tubes that carry a heating fluid (water or antifreeze) attached to an absorber plate, which maximizes heat absorption from sunlight.

2. Storage Tank

This insulated tank holds the heated water and is larger than conventional water heaters. Heat is transferred from the fluid to the water through a coil of tubes.

3. Types of Solar Water Heating Systems

Solar water heating systems can be classified as either active or passive systems:

• Active Systems: These systems rely on pumps to circulate the liquid between the collector and the storage tank. Active systems are the most common in residential applications.
• Passive Systems: rely on gravity and the tendency for water to naturally circulate as it is heated.

Active Solar Water Heating Systems

Active solar water heating systems are designed for domestic hot water and can also be utilized for space heating applications. A typical active water heating system includes the following major components:

Parts of Water Heating Systems

1. Collector(s): To capture solar energy.
2. Circulation System: To move fluid between the collectors and the storage tank.
3. Storage Tank: For holding heated water.
4. Backup Heating System: To provide additional heat when needed.
5. Control System: To regulate overall system operation.

A typical active water heating system that exhibits effectiveness, reliability, and low maintenance is shown in Figure.

This system primarily utilizes distilled water as the circulating fluid in the collector.

1. Collector Operation

• The collectors contain water only when the pump is operating.
• In cases of power failure or during the night, the absence of fluid in the collector prevents freezing or cooling down, ensuring efficient startup when sunlight returns.

2. System Reliability

• This design is widely used due to its reliability.
• Collector Positioning: The collectors must be mounted higher than the drain-back tank or heat exchanger, which may pose challenges if collectors are ground-mounted.

3. Heat Exchanger Function

• A double-walled heat exchanger separates the fluids circulated through the collectors from the household water. This design prevents contamination of the potable water.
• The heat exchanger transfers heat from the circulating fluids to the water used in the home.

4. Circulating Fluids: The circulating fluids can include:  Water, Oil, Antifreeze solution, Refrigerant

5. Control System: The system’s controller activates the pumps for the collectors and heat exchanger when the designated temperature differences are reached.
The heat exchanger can be:

• Separated from the storage tank
• Integrated into the tank

6. Maintenance Considerations

• Systems using antifreeze solutions require inspection every two years to verify the solution’s effectiveness.
• Oil or refrigerant systems are typically sealed, requiring less maintenance.
• Refrigerant systems can be more costly and need careful handling to avoid leaks.

7. Applications

• This hot water system is versatile and can be used for heating swimming pools and spas.
• Lower-cost unglazed collectors (without a glass cover) are available for specific applications.