Alternative-Heating-Info.com
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Solar Hot Water Heater Systems
Indirect Pressurized System (shown above)
The indirect pressurized system is a type of residential solar hot water system referred
to as “indirect” because the sun, through a roof-mounted collector, heats fluid
circulating in a closed-off solar loop which never comes in direct contact with usable
water stored in an insulated tank.
This type of system accommodates climates where freezing weather occurs more
frequently. A differential control senses temperature differences between water
leaving the collector and the coldest water in the bottom of the storage tank. When
the temperature of the water in the collector is hotter than the water in the tank, the
differential control operates the circulating pump.
A heat exchanger is located within the storage tank to maximize the heat transfer from
the antifreeze solution to the coldest water in the storage tank. A small photovoltaic
solar panel option (which generates electricity from the sun) is available to operate the
circulation pump, further reducing traditional energy consumption.
Drainback System
The drainback system is an indirect, non pressurized, closed loop system. When the
hot water controller senses the temperature in the solar collector (panel) is greater
than the temperature at the bottom of the hot water storage tank, water from a
second, reservoir tank, is pumped up to the collector.
The water heated by the collector is then pumped through a heat exchanger which in
turn heats the water in the storage tank for domestic consumption.
The water running through the collector and heat exchanger never comes into contact
with the potable water stored in the solar storage tank.
Once the storage tank reaches the desired temperature, the pump shuts off and the
solar fluid (usually water) drains back into the reservoir leaving only air in the collector.
The drainback method protects the system from freezing, overheating, and panel
corrosion resulting from water with high mineral content.
The indirect pressurized system is a type of residential solar hot water system referred
to as “indirect” because the sun, through a roof-mounted collector, heats fluid
circulating in a closed-off solar loop which never comes in direct contact with usable
water stored in an insulated tank.
This type of system accommodates climates where freezing weather occurs more
frequently. A differential control senses temperature differences between water
leaving the collector and the coldest water in the bottom of the storage tank. When
the temperature of the water in the collector is hotter than the water in the tank, the
differential control operates the circulating pump.
A heat exchanger is located within the storage tank to maximize the heat transfer from
the antifreeze solution to the coldest water in the storage tank. A small photovoltaic
solar panel option (which generates electricity from the sun) is available to operate the
circulation pump, further reducing traditional energy consumption.
Drainback System
The drainback system is an indirect, non pressurized, closed loop system. When the
hot water controller senses the temperature in the solar collector (panel) is greater
than the temperature at the bottom of the hot water storage tank, water from a
second, reservoir tank, is pumped up to the collector.
The water heated by the collector is then pumped through a heat exchanger which in
turn heats the water in the storage tank for domestic consumption.
The water running through the collector and heat exchanger never comes into contact
with the potable water stored in the solar storage tank.
Once the storage tank reaches the desired temperature, the pump shuts off and the
solar fluid (usually water) drains back into the reservoir leaving only air in the collector.
The drainback method protects the system from freezing, overheating, and panel
corrosion resulting from water with high mineral content.
Solar hot water heater systems are available in many different configurations but
basically fall into two categories: Direct and Indirect systems.
Direct Solar Hot Water Systems: The water circulated through, and heated by, the
collector (solar panel) is the same water used for cooking and bathing. Direct systems
are commonly found in the southern United States and tropical climates.
Indirect Solar Hot Water Systems: Water or antifreeze solution is circulated through
the collector and heats your domestic hot water indirectly through a heat exchanger.
Indirect systems are also referred to as "closed loop" systems because the heating
medium never comes in contact with the potable water. Closed loop systems are
either pressurized or non-pressurized. The drainback type water heater is an example
of a non-pressurized system.
Active and Passive Systems
Solar hot water systems are also classified as Active or Passive. An active system
employs electric devices such as a pump and differential control (a type of thermostat)
to operate the system.
Passive systems rely on "natural convection" to move the water back and forth
between the collector and the tank.
basically fall into two categories: Direct and Indirect systems.
Direct Solar Hot Water Systems: The water circulated through, and heated by, the
collector (solar panel) is the same water used for cooking and bathing. Direct systems
are commonly found in the southern United States and tropical climates.
Indirect Solar Hot Water Systems: Water or antifreeze solution is circulated through
the collector and heats your domestic hot water indirectly through a heat exchanger.
Indirect systems are also referred to as "closed loop" systems because the heating
medium never comes in contact with the potable water. Closed loop systems are
either pressurized or non-pressurized. The drainback type water heater is an example
of a non-pressurized system.
Active and Passive Systems
Solar hot water systems are also classified as Active or Passive. An active system
employs electric devices such as a pump and differential control (a type of thermostat)
to operate the system.
Passive systems rely on "natural convection" to move the water back and forth
between the collector and the tank.
Thermosyphon System (shown above)
As a self contained solar water heating system, thermosyphon systems have
collector(s) positioned lower than the tank(s) and operate on the principle of natural
convection.
As the sun heats the water in the collector, it expands slightly and becomes lighter,
causing the water to rise into the tank in the same way that a balloon rises in the air.
The colder, heavier, water in the tank then sinks into the collector. These events
create a continuous natural circulation.
Thermosyphon systems are widely accepted throughout the world today. They are
automatic, simple, and reliable. Thermosyphon systems do not require a pump or
control. There are no moving parts which allows for minimal, if any, maintenance
concerns.
Direct System with Pump and Differential Control
When the sun is shining, a pump circulates water from the bottom of a storage tank
through collectors where it is heated, and then returned to the tank for storage and
eventual use.
A Differential Control senses temperature differences between water leaving the
collector and the coldest water in the bottom of the storage tank. When the
temperature of the water in the collector is hotter than the water in the tank, the
differential control operates the circulating pump.
A small photovoltaic solar panel option (which generates electricity from the sun) is
available to operate the circulation pump, further reducing traditional energy
consumption. Freeze protection includes a thermally operated valve installed at the
collector (where required) or by manually draining.
As a self contained solar water heating system, thermosyphon systems have
collector(s) positioned lower than the tank(s) and operate on the principle of natural
convection.
As the sun heats the water in the collector, it expands slightly and becomes lighter,
causing the water to rise into the tank in the same way that a balloon rises in the air.
The colder, heavier, water in the tank then sinks into the collector. These events
create a continuous natural circulation.
Thermosyphon systems are widely accepted throughout the world today. They are
automatic, simple, and reliable. Thermosyphon systems do not require a pump or
control. There are no moving parts which allows for minimal, if any, maintenance
concerns.
Direct System with Pump and Differential Control
When the sun is shining, a pump circulates water from the bottom of a storage tank
through collectors where it is heated, and then returned to the tank for storage and
eventual use.
A Differential Control senses temperature differences between water leaving the
collector and the coldest water in the bottom of the storage tank. When the
temperature of the water in the collector is hotter than the water in the tank, the
differential control operates the circulating pump.
A small photovoltaic solar panel option (which generates electricity from the sun) is
available to operate the circulation pump, further reducing traditional energy
consumption. Freeze protection includes a thermally operated valve installed at the
collector (where required) or by manually draining.
Direct Solar Hot Water Heater Systems
Indirect Solar Hot Water Heater Systems
| Indirect Pressurized Solar Hot Water System with Auxiliary Heat Source |
| Direct Thermosyphon Solar Water Heater |