What is Solar water Heating?

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Using solar water heating systems, saves money on utility bills and is absolutely pollution free. Solar water heater domestically termed as "hot water system" is most preferred for its cost effectiveness. It operates on minimal maintenance and after the initial installation cost, there is hardly any other costs involved. The Energy Saving Trust of UK conducted a field trial and concluded that 55% of total utility bills could be saved per year if gas or electricity based heating systems are completely replaced with solar heating systems. According to Energy Star,"STAR qualified solar water heaters can cut your carbon dioxide emissions in half. Installing a qualified solar water heater will reduce the load of your electric water heater by almost 2,500 kWh per year, preventing 4,000 pounds of carbon dioxide from entering the atmosphere annually. This is the equivalent of not driving your car for four months every year".

How does a Solar Water Heating System work?

When a black surface is exposed to direct sunlight it absorbs maximum amount of heat. Similarly, when the sunlight enters any closed  space through glass windows, the heat energy is trapped inside. This is termed as "Green House Effect". These two natural phenomenon have been clubbed together to design solar water heating systems. The solar water heating system is divided into two compartments:

1. Heat collector 
2. storage tank.

A black surface (absorber) is used for absorbing maximum amount of solar heat. It is always kept in the direction to receive maximum amount of sunlight. This heat is transferred to the water present in the collector. The heated water is stored in the tank that is adequately insulated to control heat loss. The density difference between the hot and cold water helps the hot water to rise above. Hence, the hot water is circulated immediately when the tap is opened. There are the one tank systems and the two tank systems. While the  two tank heater preheats the water with the solar heater before it goes into the conventional heater, in the one tank systems both backup heater and solar heater have water in the same tank.

What are the different Solar Water Heating Systems?

Basically, there are two types of solar water heating systems.

• Direct or Active circulation system: In this solar water heating system, pumps are used for circulating household water via collector into the house. This system is good for places where the temperature is usually warm and never freezes.
• Indirect or Passive circulation system: This type of system is most preferred in cold regions. In this system, water is heated by introducing heat transfer fluid via collectors along with a heat exchanger. These passive systems are further divided into two types namely integral collector storage passive system (used in areas where temperature never goes below freezing point) and thermosyphon systems. This system makes use of heavy storage tank. This allows enough space for the warm water to rise above and circulate freely. These solar water heating systems are comparatively expensive but are more reliable than direct circulation system.

What are the Different Types of Solar Collectors?

Solar Batch Heater: Integral Collector storage systems (ICS) or Solar Batch Heater is one of the cheapest and simplest way of producing hot water from solar energy.  The do-it-yourself-community had nicknamed it as the "breadbox water heater".  This type of water heaters are made up of insulated glazed box that are painted black to absorb optimum solar energy. Plastic or glass cover is used to acquire glaze effect so that the heat of the Sun's rays enters into the tank and is trapped inside to warm the water in the insulated tank. These water heaters are known to provide hot water with temperature sometimes exceeding 160 degrees.  Cold water is mixed with this hot water by using tempering valve so that the temperature of the hot water you receive by tap is controlled.

Batch heaters: Batch solar heaters use the technique of passive solar heating are an ideal option for households with 3 to 4 people. For a large family multiple batch heaters can be installed.  While installing these heaters one should always take into consideration the strength of the roof and temperature. These heaters work well in sunny and mild freezing conditions otherwise the outdoor pipes or the collector can get freezed. Nowadays, these outdoor pipes are being replaced by freeze-tolerant pipes to combat the  effect of freezing temperature.

Flat plate collectors: A flat collector is a big and shallow metal box covered with plastic or glass at the top and an abosorber plate at the bottom that is usually painted black. It uses sunlight to heat water.  So as to ensure minimum loss of  heat, the sides and the bottom of the flat plate collectors are insulated.  When the sunlight passes through the glazed surface it hits the absorber plate which converts the solar energy into heat energy and warms up the water inside.  It is ideal water heating solution for large families or places where huge amount of hot water is required for laundry washing.  Some of its commercial applications include car washes, laundromats, eating establishments and military laundry facilities. 

What size Solar water heater is required for home use?

Temperature and the size of the family decides the type of solar water heater to be used in a particular household. Batch heaters with a capacity of 80 to 100 gallons are ideal for a small neutral family (2 to3)  living in temperate climate where freezing is very rare.  Thermospyn water heater holding a capacity of 100 to 120 gallons of water is good for a family wiht more than 3 to 4 members, especially when there is no scope for installing multiple batch heater tanks. Solar water heaters must be SRCC (Solar Rating Certification Corporation) certified and should be installed in accordance to the building codes for the city. It costs around $5000 for a family and higher for commercial applications but the later costs are almost minimal.

Do you know: From October 2012 onwards, the UK government will be paying Renewable Heat Incentive to the citizens who are using solar water heating systems.

For additional information on Solar Technology, click on the links below:

Uses of Solar Dish 

Interesting Facts About Solar Energy 

Electricity from Solar Energy

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