Understanding Solar Hot Water Systems
What are the different types of solar hot water systems available?
There are five types of
solar hot water systems today. We will explain their operation along
with their advantages and disadvantages below.
Open System (the most
efficient)
The same water that is used
to supply your house, or business, is used in this type of system.
The water from the tank circulates to the collectors, then back to the tank and
on to the faucets. Circulation is accomplished via a water pump
(DC or AC).
Closed Antifreeze
System
Here, antifreeze
circulates from a coil of pipe submerged in the water of the tank to the
collector. The antifreeze coil provides heat to the water reserve
in the tank. This system is protected against freezing weather.
Closed Drainback System (the least efficient)
Here, water in an outer
tank is circulated to the collector. The water level drops back to
the tank when the pump stops circulating. The inner tank holds the
pressured water from the house. There are three efficiency losses
present in
this system:
- The loss in the heat
transfer between the two tanks.
- The outer tank with higher
temperature looses more heat to the air.
- The air in the panel loop
reduces heat transfer of the water, which will create the need to
double the number of panels.
Closed Antifreeze
system with internal heat exchanger
Additional losses over
2nd best system (closed antifreeze). In this system, there are double heat exchangers
present with
double the losses. These two tanks lose heat to the air, and
demand higher
initial costs due to an additional pump that is required.
Closed drainback system with separate heat exchanger tank
Additional losses over
the third best system above. We now have introduced a
fourth loss associated with an additional heat exchanger. This
heat exchanger is of course less efficient than the built-in heat
exchanger. This system includes a second tank that is loosing
heat to the ambient. This system also has two additional pumps
that will require maintenance.
