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Solar water heating

About Solar Water Heating

Solar Water Heating System is very commonly used in Hotels, Hospitals, and Industrial Canteens and in Boiler Pre Heating application. It is possible to design Solar Water Heating System to provide hot water upto 80°C. There is no limitation in the capacity of the system.

Normally, we design for Hotel, Hospital requirements, the system as either THERMOSIPHON OR CLOSED LOOP CIRCULATION SYSTEM. In the case of Thermosiphon, there is no pump and the circulation between the solar panel and the tank is due to density difference. Normally, such systems are designed upto 3000 liter capacity. In the case of closed loop system, a pump is provided and activated by a control panel for circulating the water between the solar tank and solar collectors. In these types of system, the cold water from the over head tank is connected directly to the solar tank and the hot water from the solar tank to the usage point is taken from the top of the tank. These systems are ideal for bathing requirements of hot water during non Sunny hours.

For canteen and Boiler Pre Heating applications, system is designed as OPEN LOOP SYSTEM. In this case, the cold water is pumped directly to the solar collectors and the hot water is collected in the solar tank. In such case, the temperature of hot water from the solar collector can be pre fixed. There is no mixing of cold water with the hot water at the time of usage. These systems are preferred in places, where the usage of the hot water is during the day time and also required at very high temperature.

Excepting in the case of thermosiphon system, the collectors can be located separately and the tank can be at convenient location. The number of solar collectors required depends on the capacity of the system and temperature to be heated up from the system.

The solar tank is made of stainless steel material and insulated to retain hot water for 48 hours. Generally, to arrive at the capacity of the system, we assume 25 liters per person per bath or 5 litres per food prepared per person. From this calculation the capacity of the system is arrived at. For bathing purpose, 60°C systems are advisable and for other purposes 80°C systems are preferred. The outlet from the solar system to the usage point should be with GI Pipe of class B and of suitable sizes.

It is advisable to contact us before carrying out the hot water pipelines. Generally, hot water pipelines are insulated in order to retain loss in temperature of hot water while flowing. For 1000 litres system for example, we use 8 solar collectors of 2 sq.m. area each, totally occupying 240 sq.ft. and for 1000 litres 80°C , 10 solar collectors occupying 280sq.ft is used.

Generally the solar systems have a life span of 15 years and maintenance cost is as low as 5% of the plant cost, per annum. It is preferable to use potable water for the system.

The investment in Solar Water Heating System is eligible for 100% depreciation in the first year and also loan assistance at concessional interest rate is available from financial institutions.

We also prepare feasibility study report at a cost.

solar water heater details solar water heater comparision

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.

solar water heater working

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.

Thermo-syphon 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.

Storage Tanks and Solar Collectors

Most solar water heaters require a well-insulated storage tank. Solar storage tanks have an additional outlet and inlet connected to and from the collector. In two-tank systems, the solar water heater preheats water before it enters the conventional water heater. In one-tank systems, the back-up heater is combined with the solar storage in one tank.

Three types of solar collectors are used for residential applications:

Flat-plate collector

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.

Integral collector-storage systems

Also known as ICS or batch systems, they feature one or more black tanks or tubes in an insulated, glazed box. Cold water first passes through the solar collector, which preheats the water. The water then continues on to the conventional backup water heater, providing a reliable source of hot water. They should be installed only in mild-freeze climates because the outdoor pipes could freeze in severe, cold weather.

Evacuated-tube solar collectors

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.

Solar water heating systems almost always require a backup system for cloudy days and times of increased demand. Conventional storage water heaters usually provide backup and may already be part of the solar system package. A backup system may also be part of the solar collector, such as rooftop tanks with thermosyphon systems. Since an integral-collector storage system already stores hot water in addition to collecting solar heat, it may be packaged with a tankless or demand-type water heater for backup.

Selecting a Solar Water Heater

Before you purchase and install a solar water heating system, you want to do the following:

Also understand the various components needed for solar water heating systems, including the following:

Installing and Maintaining the System

The proper installation of solar water heaters depends on many factors. These factors include solar resource, climate, local building code requirements, and safety issues; therefore, it's best to have a qualified solar thermal systems contractor install your system.

After installation, properly maintaining your system will keep it running smoothly. Passive systems don't require much maintenance. For active systems, discuss the maintenance requirements with your system provider, and consult the system's owner's manual. Plumbing and other conventional water heating components require the same maintenance as conventional systems. Glazing may need to be cleaned in dry climates where rainwater doesn't provide a natural rinse.

Regular maintenance on simple systems can be as infrequent as every 3–5 years, preferably by a solar contractor. Systems with electrical components usually require a replacement part or two after 10 years. Learn more about solar water heating system maintenance and repair.

When screening potential contractors for installation and/or maintenance, ask the following questions:

Improving Energy Efficiency

After your water heater is properly installed and maintained, try some additional energy-saving strategies to help lower your water heating bills, especially if you require a back-up system. Some energy-saving devices and systems are more cost-effective to install with the water heater.