Solar water heating systems are an effective way to harness solar energy for heating water, offering significant savings on electricity bills and reducing carbon emissions. This article provides an overview of solar water heating systems, their components, applications, types, and costs.

Overview of Solar Water Heating Systems

Solar water heating systems (SWHs) utilize solar energy to heat water, making them a cost-effective solution for various applications. These systems can heat water to temperatures between 60-80°C and are suitable for both residential and commercial use. A typical 100-liter solar water heater can replace an electric geyser, saving approximately 1,500 units of electricity annually and preventing the emission of 1.5 tons of carbon dioxide each year.

How the Solar Water Heater Works

solar water heating systems consist of storage tanks and sun collectors. There are two types of solar water heating systems: active, which include circulating pumps and controls, and passive, which do not.

Active Solar Water Heating Systems.

Active solar water heating systems can be classified into two types:

• Direct circulation systems.

Pumps move household water via collectors and into the residence. They do well in places where it rarely freezes.

• Indirect circulation systems.

Pumps move a non-freezing heat-transfer fluid through collectors and a heat exchanger. This heats the water, which flows into the residence. They are popular in areas prone to frigid conditions.

Passive Solar Water Heating Systems

Passive solar water heating systems are normally less expensive than active systems, although they are often less efficient. However, passive systems can be more dependable and endure longer. There are two fundamental types of passive systems:

• Passive systems with integrated collector and storage

These include a storage tank covered in a transparent material that allows the sun to heat the water. Water from the tank then enters the plumbing system. These function well in locations where temperatures are rarely below freezing. They also function effectively in households with high daytime and evening hot water requirements.

• Thermosyphon systems

When a hot water faucet is turned on, water flows through the plumbing system after being heated in a collector on the roof. The bulk of these systems have a 40-gallon capacity.

Key Components of Solar Water Heater

Solar water heaters often combine several key components:

Solar collectors:

These collectors, which serve as the focal point of a solar water heating system, are responsible for catching sunlight and converting it into thermal energy. Flat-plate collectors and evacuated tube collectors are the two most common models. The former is more conventional, with a dark color absorber plate that absorbs solar radiation and a translucent cover that reduces temperature loss. The latter, evacuated tube collectors, use glass tubes with a vacuum layer, which improves insulation and efficiency.

Heat Transfer System:

After the solar collectors capture sunlight and convert it into thermal energy, a heat transfer medium (often a mixture of water and an antifreeze substance) flows through the collectors, absorbing the accumulated heat.

Storage Tanks:

The heated medium from the solar collectors travels to a storage tank. The accumulated heat in this reservoir transfers the temperature of the water stored within it.

Backup heating elements:

Solar water heating systems typically include an extra heating element, such as an electric or gas-powered heater. This ensures a steady supply of hot water even during periods of low sunshine or increased demand.

Solar water heaters operate on the basis of solar thermal energy conversion. At its core, this method involves harnessing sunlight to raise the temperature of a medium, so preparing the water for use in baths, ablutions, and space heating.

Working Principle

1. Absorption of Solar Energ

Applications

Solar water heaters are versatile and can be used in various settings, including:

• Homes
• Community Centers
• Hospitals
• Hotels and Restaurants
• Dairy Plants
• Swimming Pools
• Canteens and Ashrams

Using solar water heaters can significantly reduce electricity or fuel bills, with savings of 70-80% possible compared to conventional systems.

Types of Solar Water Heaters

Solar water heaters are an eco-friendly solution for heating water using solar energy. They can be broadly categorized based on their design and operational mechanism. Here are the main types of solar water heaters:

Flat Plate Collector (FPC) Solar Water Heaters

Flat plate collector (FPC) solar water heaters consist of an insulated outer metallic box covered with a glass sheet on top. Inside, there is a black absorbing surface (absorber) that absorbs solar radiation and transfers the heat energy to water flowing through it. The heated water is collected in an insulated storage tank to prevent heat loss. FPC solar water heaters are suitable for moderate climates and are generally more cost-effective compared to evacuated tube collectors.

Evacuated Tube Collector (ETC) Solar Water Heaters

Evacuated tube collector (ETC) solar water heaters are made of double-layer borosilicate glass tubes that are evacuated to provide insulation. The outer wall of the inner tube is coated with a selective absorbing material that helps absorb solar radiation and transfer the heat to the water flowing through the inner tube. ETC solar water heaters are more efficient, especially in colder climates, and perform better in low-light conditions. However, they are more expensive than flat plate collectors.

Cost of Solar Water Heating Systems

The approximate costs for different capacities of solar water heating systems are as follows:

These costs include essential components such as cold and hot water tanks, support structures, heat exchangers, and installation.

Conclusion

Solar water heating systems offer a sustainable and economical solution for heating water. By utilizing solar energy, these systems not only help in reducing energy costs but also contribute to environmental conservation. As technology advances, the efficiency and affordability of solar water heaters continue to improve, making them an increasingly attractive option for both residential and commercial applications.

FAQ’s