Sundance Power
Systems, Inc.
Phone: 828.645.2080
Fax: 828.680.9798
11 Salem Hill Road
Weaverville, NC 28787
E-mail

» Click here for more information on solar thermal system designs.

Open Loop Systems:

• Open loop systems are very basic and were the first to appear on the market
• More suitable for tropical climates that do not ever drop to freezing temperatures
• The water stored in the solar storage tank is re-circulated directly through the solar collectors where it is heated by the sun and returned to the storage tank in order to maximize solar production
• A pump controller ("differential controller") turns the pump on when the collectors are hotter than the stored water, and shuts it off when they reach the same temperature

Closed Loop Systems:

• Closed Loop systems do not directly heat the water in the storage tank via the solar collectors
• A separate fluid is circulated through the collectors, and a heat exchanger is used to transfer this heat to the water in the storage tank
• Additional components; expansion tank, pressure gages, and fill valves are required
• There are two types of Closed Loop Systems:
  • Glycol Indirect System
    • Uses glycol as the heat transfer fluid
    • Chance of freeze damage is eliminated

• Drainback System
• Uses fewer components than any other system which increases the system reliability factor
• More efficient than the glycol indirect system
• Freeze protection is based on gravity
• Non-pressurized system that uses water as the heat transfer fluid
• A drainback reservoir is installed in the collector loop to store the heat transfer fluid when there is limited solar gain

DC Pumping System:

• Suitable for small residential systems
• Optimum performance achieved in areas of high solar insolation
• Operates independently from the grid