Solar Water Heaters

Shankara is on one of the leading manufacturers of Solar Water Heater. Solar Water Heater is a viable alternative to the electric geyzer for meeting the daily hot water needs of households and commercial institutions across various cities. Unlike electric geyzers that use conventional electricity, solar water heaters are environment friendly as they capture the heat energy available in the Sun's rays and transfer it to the water that needs to be heated

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Detailed Description for Solar Water Heaters

Solar water heater is a system that utilizes solar energy (or the energy from sunlight) to heat water. It has a system that is installed on a terrace or open space where it can get sunlight and the energy from the sun is then used to heat water and store it in an insulated tank. The system is not connected to electricity supply and thus does not have an on-off switch, but it uses the sunlight throughout the day to heat the water and store it in the storage tank. Water from the storage tank can then be used for any application as desired.

 

HOW THEY WORK

Solar water heating systems include storage tanks and solar collectors. There are two types of solar water heating systems: active, which have circulating pumps and controls, and passive, which don't.

ACTIVE SOLAR WATER HEATING SYSTEMS

There are two types of active solar water heating systems:

·         Direct circulation systems
Pumps circulate household water through the collectors and into the home. They work well in climates where it rarely freezes.

·         Indirect circulation systems
Pumps circulate a non-freezing, heat-transfer fluid through the collectors and a heat exchanger. This heats the water that then flows into the home. They are popular in climates prone to freezing temperatures.

·          


PASSIVE SOLAR WATER HEATING SYSTEMS

Passive solar water heating systems are typically less expensive than active systems, but they're usually not as efficient. However, passive systems can be more reliable and may last longer. There are two basic types of passive systems:

·         Integral collector-storage passive systems
These work best in areas where temperatures rarely fall below freezing. They also work well in households with significant daytime and evening hot-water needs.

·         Thermosyphon systems
Water flows through the system when warm water rises as cooler water sinks. The collector must be installed below the storage tank so that warm water will rise into the tank. These systems are reliable, but contractors must pay careful attention to the roof design because of the heavy storage tank. They are usually more expensive than integral collector-storage passive systems.

 

 

Different types of solar water heaters available in market

There are 2 types of solar water heaters that are available in Indian market:

1) FPC (Flat Plate Collectors) system: These are metallic type systems and have a longer life. Glazed flat-plate collectors are insulated, weatherproofed boxes that contain a dark absorber plate under one or more glass or plastic (polymer) covers. Unglazed flat-plate collectors -- typically used for solar pool heating -- have a dark absorber plate, made of metal or polymer, without a cover or enclosure.

 

2) ETC (Evacuated Tube Collectors) system: These systems are made up of glass and are fragile. They feature parallel rows of transparent glass tubes. Each tube contains a glass outer tube and metal absorber tube attached to a fin. The fin's coating absorbs solar energy but inhibits radiative heat loss. These collectors are used more frequently for U.S. commercial applications

Both these type of water heaters come with or without pump. Pump is used to move water from collectors to the storage tank. Those without pump use thermosyphon principle to move water from collectors to storage tank automatically.

How to decide on which type to buy

ETC systems are fragile but are cheaper. They are also very good for colder regions where the temperature is sub zero. In place where the water is salty, these systems require regular cleaning due to deposition of salt on the inner surface of glass tubes.

FPC systems are long lasting, as they are metallic. But they are expensive than ETC systems. They can work in colder regions with sub zero temperature but will need an anti freeze solution making the system expensive. In places with salty water a heat exchanger is required with FPC system to avoid scale deposition that can impact the heating capability of the system.

System without pump (thermosyphon) is ideal for domestic and small application users (as it is cheaper) provided water does not have high chlorine content. Those with pumps are good for industries.

How does the system perform on rainy/overcast days

Many people have concerns that solar systems will not work on overcast days. Well a system can still work if the overcast is not long (less than a day or two) as the system works on diffused radiation in the atmosphere. A solar system can also be integrated with an existing electric system that can act as a backup during the days when the overcast is long. The electric system can switch on if the water temperature from the solar water heater goes down below 40oC. Electric backup is not required in solar system if you have an existing electric water heater. In case you do not have an existing water heater, you can install an electric backup. You can also keep the two systems separate and use the electric system only when needed.

Maintenance requirements of solar water heater

1.       If you have ETC system then glass can break, as it is fragile. So the glass may need occasional replacement.

2.       Scaling happens on solar water heaters regularly especially if the water is hard. So the collectors need regular cleaning using acid.

3.       If the outside surface of water heater is painted, then it may need a repaint every 2-3 years to prevent corrosion.

4.       Occasional leakages could happen in the system and local plumbers can repair those.

Sizes of solar water heaters are available in the market

Solar water heaters available in market start from size of 100 ltr per day. The other sizes that are available are 200, 250, 300 and 500 lts per day. The maximum area required for the collectors to be installed on terrace/open area is:

Capacity (liters per day)

Area in sq. m. for ETC system

Area in sq. m. for FPC system

100

1.5

2

200

3

4

250

3.75

5

300

4.5

6

350

7.5

10

 

Using solar water heater is a win-win situation for consumers, utilities and the environment. Renewable energy is future and embracing the same makes a lot of economic and environmental sense.


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