A solar water heater consists of a collector to collect solar energy and an insulated storage tank to store hot water.One of the popular devices that utilizes the solar energy is Solar water heating system.
The water passing through the risers get heated up and is delivered the storage tank.The circulation of that water through absorber pannel in the collector raises the temperature to 80 C in a good sunny day.The total system with solar collector , storage tank and pipelines is called solar hot water systems.
TYPES OF SOLAR WATER HEATING SYSTEMS:
They are of two types :
1.Closed loop systems
2.Open loop systems
CLOSED LOOP SYSTEMS:
In this heat exchangers are installed to protect the systems from hard water obtained from borewells on from freezing temperatures in the cold regions.
OPEN LOOP SYSTEMS:
In this either thermosyphon or forced circulation system , the water in the systems is open to the atmosphere at one point or other. They are suitable for domestic and small institutional systems , provided the water is treated and portable in quality. The forced circulation systems use electrical pumps to circulate the water through collectors and storage tanks.
FLAT PLATE COLLECTORS SOLAR WATER HEATER:
The solar radiation is absorbed by the flat plate collector which consists of an insulated outer metallic box covered on the top with glass sheet.
Inside there are blackened metallic absorber sheets with built in channels or riser tubes to carry water.There are 60 BIS approved manufacturers of Solar Flat Plate Collectors.
EVACUATED TUBE COLLECTOR SOLAR WATER HEATER:
Evacuated Tube Collector is made of double layer borosilicate glass tubes. The outer wall of the inner tube is coated with selective & good quality absorbing material. It helps absorption of solar radiations and transfers the heat to the water which flows through the inner tube. There are 44 approved ETC based solar water heating suppliers.
FEATURES OF SOLAR WATER HEATER:
As clear by the name, Solar water heater turns cold water into hot water with the help of sun rays.
1.Around 60 deg – 80 deg c temp can be attained depeding on solar radiation , weather conditions and solar collector system efficiently.
2.Hot water for homes , hostels , hotels , hospitals , industries etc.
3.Can be installed on roof tops , building terrace and open ground where there is no shading.
4.Solar water heater system generates hot water on clear sunny days , partially clouded bot not in rainy or heavy overcast day.
5.Only soft and potable water can be used.
6.Stainless steel is used for small tanks whereas Mild Steel tanks with anti-corrosion coating inside are used for large tanks.
7.Solar water heater of 100-300 litres capacity are suited for domestic application.
8.Larger systems can be used in restaurants , guest houses , hotels , hospitals , industries etc.
A 100 liters capacity solar water heater can replace an electric geyser for residential use. capacity and saves 1500 units of electricity annually.
AVOIDED UTILITY COST ON GENERATION:
The use of 1000 solar water heater of 100 liters capacity each can contribute to a peak load shaving of 1 MW.
A solar water heater of 100 liters capacity can prevent the harmful emission of 1.5 tonnes of carbon dioxide per year.
Its price is about Rs 15000-20000 for a 100 liters capacity systems and Rs 110-150 per installed liter for higher capacity systems.