How Do Solar Hot Water Heaters Work

You will likely have seen solar hot water systems popping up on the rooftops in your neighborhood.  Solar water heating systems have been available for many years.  Today we are looking at how solar hot water heaters work, the types of heaters, and how they will save you money.


What Are The Benefits Of Solar Hot Water

Installing a solar hot water system has several benefits for your home.  Here are some of the top benefits:

  1. Reduction in Energy Bills: Your solar hot water system can provide you with up to 80% of your hot water needs.  Because water heating can account for almost 20% of your total electric bill, you will save around 15% on your total energy bill.   
  2. Reducing Your Carbon Footprint:  It is still a fact that most of the world’s energy comes from non-renewable resources like coal and natural gas. Moving to solar will help reduce these emissions while saving you money.
  3. Improving Air and Water Quality:  By reducing fossil fuel burning for our energy requirements, we reduce the air and water pollutants.  Solar Energy does not produce these dangerous by-products, so it is clean and safe.
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How Do Solar Hot Water Systems Work

All solar hot systems work by using the sun’s solar energy to heat water.  A solar collector is used to absorb the sun’s energy, which heats the water in a heat exchanger.  This solar water heating system replaces the use of traditional electricity to heat the water.

The three types of systems use heat transfer from the sun to warm water for use in your home. 

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The Three Types of Solar Hot Water Heaters

There are three solar systems, Flat Plate Collector, Integral Collector Storage, and Evacuated Tube Collectors.

Flat Plate System

The flat plate collector consists of a large heat-absorbing plate with copper pipes running through it.  A transfer fluid  (a mixture of water and glycol) is pumped up the plate and is warmed by the solar heat.  This heated transfer fluid is pumped into the solar storage tank and heats the cold water for your home.

The heat exchanger is enclosed in tempered glass.

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Benefits of Flat plate System

The flat plate system is a simple, low-cost hot water system.  They are particularly popular in warmer climates as they work best where the difference between outdoor temperature and the required water temperature is small.

Cost of Flat Plate Systems

Flat plate systems cost between $1000 and $2500 depending on your hot water needs. Adding a tank will cost between $1000 and $1500.

Integral Collector Storage

An integral collector storage system combines the solar panel and water storage into one unit.  The absorber plate is combined with a larger heat tube.  Cold water flows into the solar collector, and the heated water is then stored in the hot water tank.

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Benefits of Integral Collector Storage

The main benefit of the ICS is that it does not require any pumps.  Water flow is by natural convection circulation system and via the natural water pressure.  

Cost of Integral Collector Storage

An Integral collector storage system will cost between $1000 and $3000.  If you are installing on your roof, you need to consider the extra weight the water tank will add.

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Evacuated Tube Collectors

Evacuated tube collectors are made up of rows of glazed glass tubes connected to a head pipe.  These glass tubes contain an absorber plate and a heat pipe.  The sun heats the tube via the absorber plate, and the heat is transferred to the header pipe by the heat pipe.  Coldwater is pumped through the header pipe and is heated and collected in a hot water storage tank.

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Benefits of Evacuated Tube Collectors

The efficiency of evacuated tubes makes them ideal for colder climates and lower light areas.  Because the tubes are cylindrical, they absorb more solar energy even on cloudy days.

Made from soda-lime glass, the tubes are robust and can withstand very high temperatures.  Air is removed (or evacuated) from the tubes, forming a vacuum, and this acts as a heat insulator.

With the high efficiency, this hot water system is suitable for cold climates and will keep your water hot into the evening.

Cost of Evacuated Tube Collectors

A 30 tube vacuum heat pipe will cost around $2500.  

How to Size Your Solar Hot Water System

The size of your solar system depends on your hot water usage.  However, you can get a good estimate of the number of people in your household.  

You will need 20 square feet of roof space for the first two people in your house for the solar collectors.  For each subsequent person, an additional 12 square feet is needed.  Therefore, you will need 64 square feet of roof space for a family of four to supply 100% of your hot water needs. 

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Normally each person will use, on average, 20 gallons of hot water per day.  Therefore our family of four will need an 80-gallon tank.

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Will My Solar Hot Water System work At Night.

At night there is no sun, so you will not be able to use solar radiation to heat your water.  The solar collectors in all systems are designed to be insulated against heat loss to keep heating water for a short time after sundown.  If you require a lot of hot water use at night, you may still use your conventional backup water heater at night. 

How Much Money Will I Save With Solar Hot Water

With around 15 to 20% of your energy bill spent on heating your hot water, you can expect to save most of this after installing the solar water heating system.  If you heat a swimming pool, you can save even more if you use the solar pool heating.

Are rebates available for solar hot water systems?

There are state and federal rebates available for installing solar water heating systems.  The best way to find out about these rebates is to ask the supplier before buying.

Replacing your conventional water heater with a solar system that uses renewable energy from the sun has many benefits.  As we move away from fossil fuels to more clean energy solutions, solar power is the most accessible.  Solar water systems provide a reliable source for domestic hot water needs.