Solar Water Heating Basics


solar water heating basics, green renewable energy, solar heating systems, green electricity.

Solar Water Heating Basics

System types, design information, solar radiance, collector plate locations and collector plate tilt.

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Solar Water Heating Basics:

If you are somewhat new to Solar Water Heating and are eager to learn, you are in the right section.

We will go over the Solar Water Heating Basics for design, sizing and systems overview and how this relates to your green electricity passion.

Solar Collector

Solar Water Heating Definitions: Solar Collector

Solar Water Heating Basics - Why This Is An Important First Step:

If you are new to the solar heating game and are wondering where you should 'jump-in', it would be in the solar water heating market.

The second largest energy consumer in the typical household is the water heater, so this is a very viable candidate in your quest for green renewable energy.

The average life of a typical electric water heater is 7 years. In that time a typical family of 4 will consume between 100 and 200 million btu's of energy.

An investment in solar water heating can be one the the best investments that you make in your home for the following reasons:

The Systems are Proven
They are relatively low-cost, compared to other renewable energy systems.
They are simple systems with low maintenance.
Tax Incentives are high in proportion to the system cost.
The systems can provide up to 80% of the needed hot water.

Solar Water Heating Basics - 3 Basic Systems:

Low-temperature systems (unglazed):
These systems typically operate at about 15 to 20 degrees above the ambient or outside temperature. These systems often made from polypropylene piping that contain UV stabilizers.

These systems are used most often for heating swimming pool water, which is typically below the ambient air temperature and the collector can supply large quantities of water that is 15 degrees or more above the outside air temperature.

Mid-temperature systems:
These systems typically operate from 20 degrees to 130 degrees above the ambient or outside air temperature.

They typically are flat plate collectors with a low iron glazing, housed in an insulated box or enclosure. A copper absorber plate with copper tubes welded to the fins is usually used.

These systems are the workhorse of the domestic hot water systems and this is likely the type you will use to supply your home with hot water. Note that some designers and engineers utilize these systems to supply hot water to 'in-floor' heating systems as well.

High-temperature systems:
These systems use evacuated tubes to surround the collector pipe. They also use focused, curved mirrors to concentrate the sun energy on the collector tube.

This means that the systems need some sort of sun tracking systems, which in turn is very expensive for small, single-family systems, but extremely efficient for large arrays of panels.

These systems are often used for commercial applications or multi-family applications and supply most of the domestic hot water or other green energy for such systems as electricity and hot water heating systems.

Solar Water Heating Basics - Designing the System:

Proper Southern Location Of The Collector Panels:
Systems should be located due south, if at all possible. Any deviation from this orientation will reduce the efficiency of your system.

Remember that due south is different from magnetic south. You should face the panels perpendicular to the line of the equator. You will need to determine what the magnetic deviation or declination is in your area. This can be obtained from this hand Magnetic Declination Map.

Save Ten With Angie's List!

I have seen installation that were as much as 30 to 45 degrees off this ideal angle. If you have no other options, you will a less efficient system and you will need to increase the collector size to make up the difference.

Proper Tilt Angle Of The Collector Panels:
Since domestic hot water is used year around, it makes the most since to design the tilt angle to be advantageous of both the highest and lowest angles of the sun. The best compromise of fixed panels is to set the tilt angle equal to the latitude in which you are located.

In example if you are located at a latitude of 42 degrees north, you should set your tilt angle of the panels at 42 degrees from horizontal.

Solar Radiance Potential:
If you would like, you can view what the potential of capturing solar energy is in your area of the US.

The National Renewable Energy Laboratory (NREL) has solar maps available which indicate the amount of energy that is available in your part of the US. You can accesses these maps at:

NREL Solar maps.

These maps indicate the maximum daily solar radiation that is collectable in KWH/day. In my particular area of the country, I have about 4.5 -5.0 kwh available to me.

Determine What Obstacles Block The Suns Radiation:
This factor is quite often overlooking when designing residential collector systems.

If you live in a woods area or have sun shading from large trees or structures, this can greatly reduce your solar radiance capturing abilities.

Once you determine due south, try to locate the collectors in a area that is least impacted by obstacle shading.

Protect Against Freezing:
One of the biggest design considerations of a solar water collections system involved freeze protection of the system.

Most commonly a solution of propylene glycol is circulated through the piping system to keep the circulation system from freezing. This is quite often used in closed loop system. Even though the piping system is segregated from the actual domestic water, you should never use the toxic ethylene glycol in the closed loop.

Secondly, another system you should consider is the drain back system. This system drains the system completely when the temperatures fall below the freezing level where there is little or no activity in the system. These systems are best used in more temperate climates.

Provide a tempering valve and bypass capability:
The tempering valve is very important to assure consistent temperature water is delivered at the taps. Bypass piping and valves allow the conventional system to provide hot water if the solar heating system is down for any reason.