How It Works

Solar thermal energy has been used for over a century in California, and started out in a simple form; heating domestic water using large black tanks left out in the sun.  Today the technology has become much more advanced, and solar thermal energy can be used for domestic water heating, pools and spas, space heating and cooling, and industrial applications.

Solar thermal energy has been used for over a century in California, and started out in a simple form, heating domestic water using large black tanks left out in the sun.  Today the technology has become much more advanced, and solar thermal energy can be used for domestic water heating, pools and spas, space heating and cooling, and industrial applications. Because of the now increased incentives for solar water heating specifically, it is our main focus.  Here are the basic principles behind the main types of solar water heating systems:

Closed_Loop_DiagramClosed Loop Antifreeze – Indirect active circulation system using a pressurized closed loop of antifreeze solution to transfer the heat from the solar system.  Existing tanks or solar storage tanks are used as storage, and internal or external heat exchangers are used to transfer the heat from the antifreeze solution to the potable water.  A circulating pump and a differential controller are used, and a second pump may be used for potable water depending on system configuration.  The controller pumps the heat transfer fluid through the collectors when enough solar energy is available to heat the potable water, then transferring the heat in a heat exchanger.  Being a pressurized loop also requires the use of an expansion tank to maintain a constant pressure.  Closed loop antifreeze systems are the most versatile type of solar water heating systems and the most commonly used worldwide.  They are suitable for residential and commercial applications in all climates, offering complete freeze protection by using an antifreeze solution.  They are the most well-suited design for commercial systems, although may experience collector stagnation problems with an

Drainback_Diagram


Heat Exchanger Drainback
– Indirect active  circulation system designed to allow the collectors to completely drain when hot water load has been met.  A solar drainback tank is used to allow the heat transfer fluid, usually just water, to be completely drained out of the collectors.  Existing tanks or solar storage tanks are used as storage, and internal or external heat exchangers are used to transfer the heat from the drainback tank to the potable water.  A high head pump and a differential controller are also used, and a second pump may be used for potable water depending on system configuration.  The controller pumps the heat transfer fluid through the collectors when enough solar energy is available to heat the potable water, then transferring the heat in a heat exchanger.  Heat exchanger drainback systems provide complete freeze and overheat protection, and are suitable for residential and commercial applications in all climates.  Commercial heat exchanger drainback systems will not encounter problems with an inconsistent hot water load.

ICS_System_DiagramIntegral Collector Storage (ICS) – Direct passive circulation system combines thermal collection and storage in a single unit.  Designed using no pumps, controllers, or moving parts.  Uses city pressure to move water through the system, with all the solar storage integrated into the collector.  The water is heated in the collector on the roof, where it remains until used in the building.  Typically used in a pre-heat configuration to an existing water heating system.  Excellent for residential applications in mild climates that do not experience hard freeze conditions.  May require structural engineering due to increased weight load.

 
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