Course: REEC 220 Solar Thermal Systems

Unit 3 Overview

Unit 3 Overview

There are a wide variety of types of systems in use today.  The focus of this section is on drainback and pressurized glycol.  The fluid used in solar thermal systems is water mixed with propylene glycol.  The systems need a controller to operate the system.  Technical detail and correct sizing is required when deciding what size of pipe and type of pump to use on the system.  There are specific GPM flow rates for the pipes run and in the case of a pressurized system, an expansion tank.

The Stiebel Eltron system has been design with an expansion tank and to operate at a determined pressure.  A rough rule of thumb is to set the pressure in the loop around 20-60PSIg.  The higher the pressure of the fluid, the higher the boiling point of the fluid.  It will lower the problem of having vapor bubbles in the system.  However, it lowers the life expectancy of the system.

The video and materials are for the proper sizing of an expansion tank in a pressurized system.
Important Terms | Definition
Expansion Tank | A small tank used to protect closed water heating systems and domestic hot water systems from excessive pressure.
HTF | Heat Transfer Fluid
PSIG Pressure | Pounds Square Inch Gauge
PSIA Pressure | Pounds Square Inch Absolute