Solar Water Heater – For Home

A solar water heater is a solar device that heats water using solar energy. It use the sunlight to heat the water during the day. This hot water is stored inside an insulated solar hot water tank for use whenever required. It is among the most cost-effective uses of solar energy.

The solar energy from the sun is utilized for heating water very easily to a temperature of 55-70° C. And hence, if you replace your conventional water heater with a solar water heater, you can save up to 70-80% on electricity. Besides, it operates at low costs and is eco-friendly. This is the reason why thousands of people are installing solar water heaters every year.

With no maintenance requirement, solar heaters provide a low cost long term solution to getting hot water. For cloudy days, solar water heaters have an inbuilt electric heating element for backup. Basically, solar water heaters do conversion of sunlight into renewable energy for water heating using a solar thermal collector.

How does a solar water heater work?

In the daytime, the sun rays fall on the collectors. The absorbers present inside the collectors consume the solar radiation. As a result heat energy is produced. The solar collectors transmit this energy to the water streaming through them. This hot water is stored inside an insulated solar hot water tank for use whenever required. As the tank is insulated, it prevents heat loss. The flow of water from solar collectors to the tank continues due to the thermosiphon principle.

Types of Solar Water Heater : 

To provide outcomes in different climates and latitudes and to satisfy your budget, a variety of solar water heater configurations are available in the market. The different types allow you to choose the one that matches your preferred efficiency, capacity, functionality and price. Although choosing the right one is slightly complicated, we are here to help you find out the heater that can serve you with the utmost benefits. Solar water heater comes in two major technologies.

• ETC Solar Water Heater
• FPC Solar Water Heater

FPC type solar water heater performs better in hot climatic conditions, while ETC type solar water heater performs better in cool climatic conditions. Both the types differ by the type of collector used to absorb the solar radiation. These are discussed below in detail.

ETC Solar Water Heater – 

In ETC Solar Water Heater, the collector is designed to provide insulation using double layer borosilicate glass tubes. Each evacuated tube consists of two glass tubes having vacuum in between which is an excellent insulator. The outer wall of the inner tube is made to absorb maximum solar radiation. And that is why the wall is coated with demanding absorbing material.

Evacuated Tube Collector (ETC) acts as an absorber in the solar water heater. The incident solar radiation falling on the tube passes through the outer transparent tube and strikes the outer of inner tube. It absorbs heat energy and then passes to the cold water flowing in the tube. Hence, the heat gets transferred to the cold water resulting in heating the water.

An evacuated tube technology based solar water heating system is most energy efficient and cost effective that are best suitable for home use.

A Sun-facing collector heats a working fluid that passes into a storage system for later use. SWH are active (pumped) and passive (convection-driven). They use water only, or both water and a working fluid. They are heated directly or via light-concentrating mirrors. They operate independently or as hybrids with electric or gas heaters. In large-scale installations, mirrors may concentrate sunlight into a smaller collector.

Components – 

Solar thermal collectors capture and retain heat from the sun and use it to heat a liquid. Two important physical principles govern the technology of solar thermal collectors:

• Any hot object ultimately returns to thermal equilibrium with its environment, due to heat loss from conduction, conviction and radiation. Efficiency (the proportion of heat energy retained for a predefined time period) is directly related to heat loss from the collector surface. Convection and radiation are the most important sources of heat loss. Thermal insulation is used to slow heat loss from a hot object. This follows the Second law of thermodynamics (the ‘equilibrium effect’).
• Heat is lost more rapidly if the temperature difference between a hot object and its environment is larger. Heat loss is predominantly governed by the thermal gradient between the collector surface and the ambient temperatures. Conduction, convection and radiation all occur more rapidly over large thermal gradients (the delta-effect).