MECHSOLENERGY

TYPES OF SWH

There are two types of collectors used in a solar hot water service:

• Flat plate collectors (FPC)

• Evacuated tubes (ETC)

Flat plate solar collectors

Flat plate collector’s work on copper pipes running through a glass covered collector, often connected to a water storage tank on the roof. The sun heats the copper pipes and the resulting hot water is thermo-siphoned out of storage tank.

Evacuated tube solar collectors

Evacuated tubes (as the name suggests) consist two glass tubes fused at the top and bottom. The space between the two tubes is evacuated to form a vacuum. A copper pipe (called a heat pipe) running through the center of the tube meets a common manifold that is then connected to a slow flow circulation pump that pumps water to a storage tank below, thus heating the water during the day. The hot water can be used at night or the next day due to the insulation of the tank.

The evacuation tube systems are superior as they can extract the heat out of the air on a humid day and don’t need direct sunlight. Due to the vacuum inside the glass tube, the total efficiency in all areas is higher and there’s better performance when the sun is not at an optimum angle – such as when it’s early in the morning or in the late afternoon.

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SAVING ON SWH AS COMPARED TO ELECTRIC GYSER

A 100-liter per day water heater can save yearly electricity units in various parts of India as per the table mentioned below:

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                                                        Northern Region    Eastern Region    Southern Region    Western Region

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Expected no. of days of

use of hot water per year

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Expected yearly electricity

saving on full use of solar

hot water (units of electricity)

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The units used for water heating depend on the amount of water that is heated, so the number of unit increases proportionately as the size increases.

Annual cost of using hot water = No. of units consumed * (Cost/unit+ Service tax.)

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COST RECOVERY PERIOD

 3-4 years

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LIFE SPAN

 it last for 20-25 years.

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​SIZE OF SWH

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

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The liter per day mentioned above is liters of hot water at (60-70oC).

A 100 liters size is suitable for a family of 4.

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