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How Does Solar Water Heating Work?

June 25, 2015 by

The sun is a powerful energy source that does more than give us a tan. It heats our planet and it can heat your home. The sun provides a clean, limitless energy source that with the use of photovoltaic technology converts its fuel into electricity to power your home.

Solar Water Heater

When it comes to solar water heating there are two types: active and passive.


Active systems have collectors that are mounted on the roof or south-facing wall of your home. The role of these collectors is to absorb the sun’s radiation through a heat transfer liquid. Once absorbed, the radiation is converted into energy by pumping the heat transfer liquid through a heat exchanger that harnesses this energy in your hot water system. The heat exchanger works hard to pre-heat the water as it enters your conventional water heater system. In doing so, it reduces the amount of energy needed to bring the water up to the temperature you want.

There are direct circulation systems which use pumps to circulate household water through the installed collector, moving them into the home. These are best suited for warmer climates that don’t experience below-freezing temperatures.

Additionally, there are indirect circulation systems in which pumps circulate a heat transfer fluid that can withstand freezing temps, through the collectors and heat exchanger allowing the water to heat up before it flows into your home.


Passive solar water heating systems use heat-driven convection to circulate water or heating fluid within the system. These systems tend to be less expensive because they are not suited for climates that experience freezing temperatures.

Like active systems, passive models also have two kinds. Integral collector-storage passive systems are usually used in households where the residents need hot water throughout the day. On the other hand, thermosyphon systems allow water to flow through the system when warm water rises and cooler water sinks. In order to properly function, the collector has to be installed below the storage tank otherwise when the water rises it can cause serious damage to your home.

All solar water heaters require storage tanks and collectors that are insulated. Some systems come with two tanks, others only one. No matter what kind of system you have, you will need a backup for cloudy days. However, your home is probably already equipped with a conventional storage water heater, which can act as a backup in a pinch. Tankless water heaters can also be used for that purpose, or a backup system can be installed as part of the solar collector system for your roof.

For more information, contact Green City Plumbers today!

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