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Solar thermal panels
Solar Thermal Panel Technology
As described on the Solar thermal energy page, solar thermal technology collects the suns rays as heat which is then used to do work. The heat generated can be used for a number of things. This page focuses on the application of solar thermal liquid heating panels on the scale of a typical household.
- The above image describes a closed loop active system but contains many of the components used in solar thermal liquid panel technology.
Types of Systems
Systems can be open or closed and active or pump circulating
- Active or Pump
- utilize electric pumps to circulate water or and antifreeze solution through heat-absorbing solar thermal collectors. The picture above is an example of this type of system; which is most common in the United States.
- Thermosyphon or Passive Systems
- Most simple of solar thermal systems
- Thermosyphon principle -
- When water is heated it expands and rises causing the system to circulate if there is little hydraulic resistance
- Water moves through system without use of pumps or controls
- Implemented in areas where winter temperatures do not reach below freezing which could damage the system
- Open or Direct
- Water that flows through the system is the same water you bathe in
- When system is not active water sits in panels and pipes
- Freezing temperatures damage system
- Closed or Indirect
- Aka “closed loop” system
- Pump moves antifreeze solution through solar collector and pipes
- Sun warmed antifreeze solution flows through coils in a heat transfer tank that contains the water being heated
- Antifreeze solution is reused over and over through system and never comes in contact with the water being heated
- Better suited for extended cold season climates
Pros & Cons of Solar Thermal Liquid Systems
|Provide up to 85% of household energy needs||Potentially high initial costs in buying and installing|
|Save $ in the long run||Not very efficient in some climates|
|Use less fossil fuels to heat water||Has to be sunny to work|
|Works great if it is sunny||Has to be maintained|
China and Solar Hot Water Heaters
Here is an example of wide spread use of Solar Thermal Liquid System Technology. China is one of the largest consumers of energy in the world; 70% of their energy comes from coal . The Chinese government is encouraging the use of solar thermal hot water heaters in order to curb residential energy consumption. By Installing a total of 150 million square meters of solar thermal water heaters by 2010, the country could save about 20 million tons of standard coal, according to China's long term plan for developing renewable energy.  Currently 9% of homes in china has some form of solar thermal system.
China's Choice of System
Known as an evacuated tube collector.
- Each tube contains a glass outer tube and metal absorber tube attached to a fin and covered with a coating that absorbs solar energy well, but which inhibits radiative heat loss
- Air is removed to form a vacuum, which eliminates conductive and convective heat loss and allows operation in extreme temperatures
- models start at around 1,500 yuan ($190), although for a luxury home this could rise to 18,000 yuan ($2,250).
- For more information follow this link Solar Energy Group