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Solar Water Heater System Basics:
How do Active and Passive Systems Work?
Solar Water Heater System Basics: Here's examples of what works for active solar heating and passive solar heating systems.
Selecting the right active or passive solar heating system is undoubtedly your key to success. Some solar water heater systems are suited for cold climates and others for warm climates. This page gives you the basics of how solar home heating works.
Here's What Works For Solar Home Heating
Join in and write your own page! It's easy to do. How? Share your story about your solar water heater system.
What was the reason your purchased a solar heater?
What do you like about your solar heater?
Why did you buy your solar heater?
What is your location climate?
What percentage of your hot water does your solar heater provide?
Has your solar heater lowered your heating bill?
What about the aesthetics of solar panels?
You do not need to answer all the questions, they are intended to give you some guidance to get your creative juices flowing.
A solar water heating system captures solar heat and transfer that heat to household potable water. They perform five basic functions:
Solar heat panels collect, absorb, and transfer solar energy to a working fluid like water or a non-toxic antifreeze.
See how solar panels works.
Transfer: Move heated circulating fluids from the solar heating panel to the storage tank and back to the panel to begin the process over again. Circulation can be natural or with pumps.
Solar Storage: Stores heated water in a well-insulated tank often with a conventional storage tank as a backup source of hot water.
Controller: At the appropriate time in active solar heating a controller operates a circulating pump to move the fluid through the solar panel on demand. Controls are not required in passive solar heating because they circulate heated fluids naturally.
Active and Passive Solar Water Heater Systems
Solar water heater systems are classified as either active or passive.
Active solar heating
use pumps and controls to circulate fluids through the system.
Passive solar heater
rely on gravity or natural convection to circulate fluids through the system.
Active and passive are further characterized by the method fluids are transferred from the solar panel to the storage tank.
Direct or open-loop solar heating system uses water as the fluid that circulates through a solar panel then goes to the storage tank. They are ideal in climates where it rarely freezes.
Indirect or closed-loop solar heating system uses independent piping and heat exchanger to isolate non-freezing heat transfer fluid from household water. The heat transfer fluid is typically propylene glycol, a non-toxic antifreeze.
A heat exchanger transfers heat to household water in the storage tank. Indirect systems are required in freezing climates and for preventing scaling from mineralized water.
How Solar Water Heater Systems Work
In a very basic way, this is how solar hot water systems works. There are obviously several different combinations to illustrate how solar water heating works.
I will use two examples, first an active direct system than a passive indirect system.
Active Indirect Solar Heating System
The example below shows an active or closed loop solar hot water system.
Don't let the terminology bog you down.
You know... the system uses pumps, controllers and sensors and other valves, vents, sensors and gages.
Take a look... can you find them on the graphic below?
The graphic below shows an Active Indirect (Closed Loop) Solar Water Heater System. Courtesy EERE
solar heating panels
could be one of two types, a flat plate or evacuated tube solar panel. The Graphic does not indicate the type of panel.
Starting at the solar panel follow the (red line) representing the flow of the non-freezing heat transfer fluid into the heat exchanger.
The heat exchanger transfers the heat from the heat transfer fluid to household water in the storage tank.
Now... the heat transfer fluid returns (blue line) to the bottom of the panel to start the heating process again.
Imagine now that the household water has been heated all you have to do is turn the faucet on to enjoy your solar heated water.
How A Sunward Solar Heating System Works. The video demonstrates how a Sunward Solar Heating active indirect system works. The video is excellent. For more information about Sunward solar heating systems go to
Sunward... Solar Hot Water Made Simple
Passive Solar Heating System
The graphic below shows a passive direct or open loop solar hot water system.
This system uses pumps to move water. Heated water rises naturally in the solar heating panel.
Water is heated directly in the solar panel and moves to the storage tank. The beauty of a passive system is its simplicity.
Passive Direct or Open Loop Solar Water Heater System. Courtesy EERE
Take the next step and dig a little deeper... go to
Active Solar Heating
... Advanced and Dependable Solar Hot Water Systems and
Passive Solar Heating
... Solar Water Heating Systems.
Related Topics To Solar Water Heater System Basics:
Home Solar Power Hour
An excellect site describes why solar water heaters are becoming the new hot home improvement among homeowners.
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