Our Solar Thermal Heating System is designed as a drain-back system

...meaning when the system turns off all the fluid drains back to a storage tank located in a heated area. This allows us to eliminate the use of an antifreeze such as Glycol.  Water is a much better heat storage medium than antifreeze and antifreeze needs to be replaced every 6-7 years... too much waste for us.

A brief overview of our solar thermal heating system:

Seven 4'X10' solar collectors are mounted on our barn, sitting approximately 100 feet away and about 60 feet higher than a 500 gallon stainless steel insulated storage tank located in the house (you don't need this kind of distance for a drain-back system to work).  As a temperature difference is sensed by two thermostats connected to a differential controller, sensing the solar collectors are hotter than the water at the bottom of the storage tank, a pump kicks on to start circulating the water from the bottom of the tank up through the sun-baked 4'X10' solar collectors.  To complete the solar loop this beautiful sun heated water is now returned to the top of the insulated storage tank. If the sun stays out this wonderful circulation continues all day creating one nice warm/hot solar tank.  This water remains separate from the house water.  This is what we call the "solar loop".  A coil of copper tube acting as a heat exchanger is bathing inside and near the top of the storage tank, sitting in it's hottest water.  Cold water from our cistern (well water) is then pushed through this copper coil heat exchanger and comes out warm or hot.  The heat from the solar heated water is exchanged / transferred to the homes need for hot water. This heated water can then be distributed through the concrete floors as demanded by regular home thermostats and/or to the domestic hot water needed at the faucets and showers.

Radiant floor heating is a most pleasant way to heat a house.  Concrete holds heat for long periods of time (wonderful thermal mass) and also feels nice on the feet warming the whole human body. House heat is not lost easily when an outside door opens or the sun goes down.

When the sun does go down or becomes hidden by dense clouds for a period of time, the solar collectors cool triggering the solar loop pump to shut off.  All the water returns to storage tank safe in the house leaving no water in the buried outdoor insulated copper tubes to freeze during winter nights. At today's (2009) electric rates the pump cost about .60 cents per day if it runs all day.  This will raise the 500 gallon tank of water about 50 degrees. In other words... if the water at the bottom of the solar tank is at 80 degrees in the morning by the afternoon it will be about 130 degrees. The temp at the top of the tank, where the heat exchange coil is located, will be about 160 degrees.  All this for .60 cents. Do you see how HUGE this is?  We have been absolutely blown away by the performance of this solar thermal system.  Do not install a forced hot air home heating system until you've done your research.  I'm sure glad we did ours.

What does it cost to heat water???...

Let us compare Solar Thermal, Electric, Heating Oil, Propane, and Natural Gas as different fuels to heat water...