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Selection Guides

How to choose the right solar water heater capacity

Solar Water Heaters are widely used for water heating purposes. They have become a common appliances in many hostels, hospitals, canteens, etc. This article helps you in choosing the right solar water heater capacity.

Read: Solar Water Heaters – An introduction

Capacity Selection

Commercial Solar Water Heaters starts from 500 LPD (Liters Per Day) and can be increased in multiples of 500 LPD. The capacity can chosen based on the application of the solar water heater.

Bathing Application

In the case of bathing applications, the capacity is chosen based on the number of person bathing per day and number of times, each person is bathing per day. On average 25 liters of hot water per person is assumed per bath. Taking all these in to consideration, the required capacity of solar water can be calculated with the following formula

Required Solar Water Heater Capacity = 25 x No. of persons bathing x Average No. of baths by each person per day

For example, if there are 100 inmates in an hostel and 70 of them are using hot water once in the morning and 30 of them are using hot water once in the evening, then the total capacity of the required solar water heater will be 25*(70+30)*1 = 2500 LPD.

In an other instance, if 60 inmates are using hot water once and 40 inmates are using hot water twice a day, then the calculation for 60 inmates and 40 inmates has to be done separately and finally added. The calculation will be (25*60*1)+(25*40*2)= 1500+2000=3500LPD.

Cooking Application

In the case of cooking application, the capacity can be calculated based on the number of liters of hot water required for cooking.

Required Solar Water Heater Capacity = 1.5 x Liters of hot water required for Cooking

Here 1.25 is a constant factor, that helps in keeping a minimum quantity in storage apart from the required hot water.

For instance, if 1000 liters of hot water is required per day for cooking, then the required solar water heater capacity will be 1.5*1000=1500LPD.

Technology Selection

If the bottom of the cold water tank, the source of the cold water is placed at a height of at least 6 feet from the floor level, where the solar water heater is placed, then non pressurized solar water can be used. However, if the destination of hot water is too far or the hot water flow path has too many bends, then pressurized solar water can be used.

If the bottom of the cold water tank, the source of the cold water is placed at a height less than 6 feet from the floor level, where the solar water heater is placed, then pressurized solar water can be used.

Difference between Pressurized and Non Pressurized Solar Water Heater

Pressurized Solar Water HeaterNon Pressurized Solar Water Heater
Suitable when cold water tank is not above 6 feet from the floor level where the solar water heater is placedThe distance between the cold water tank and solar water heater does not matter
Cold water tank is the source of cold water Pressure Pump is the source of cold water
Suitable if the hot water flow path towards the destination does not have too many pumpsNumber of bends does not matter.

Read: Solar Water Heaters – An introduction

 

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