2. Motivation
• Solar Energy is “clean”
• It saves the money
• Solar-assisted water heat becomes more and
more popular in low-latitude country
• It is quite safe
3. Background
• It heats water by solar energy
• It works during day time &with enough sun
light
• Domestic
• Hotel
• School
• Other use
5. Solar Collector
Two main kinds of solar collector
1. Flat-plate collectors
2. Evacuated tube collectors
6. Glazed Flat Plate Solar Collectors
• Moderate cost
• Higher temperature
operation
• Can operate at mains
water pressure
• Heavier and more
fragile
Photo Credit: NRCan
7. Evacuated Tube Collectors
• Higher cost
• No convection losses
• High temperature
• Cold climates
• Fragile
• Installation
can be more Photo Credit: NRCan
complicated
• Snow is less of
a problem Tube Developed and Manufactured in China
Photo Credit: Nautilus
8. Solar Collectors
Pros Cons
•Capable to deliver moderate •Heavier collector weight
temperature hot water •Large wind load under wind
Flat-plate •Lower cost when compared condition
collectors with the evacuated tube •More susceptible to
collectors blockage and leakage
•More complicated in
maintenance issue
Evacuated •Lower heat loss to the •Higher capital cost
surrounding compared with flat-plate
tube •Capable to deliver to high collector
Collectors temperature water
•Lighter support structure
•Simplicity in maintenance
9. Model Assumptions
• Steady State
• Close & Open Loop
• Consider Pressure Drop Loss
• Isolation in the tank
• Qin is averaged
14. Results
• Efficiency is about 45-55%, which is close to
the solar collector efficiency
• Outlet temperature is over 40C,which is
enough for domestic use (34 C)
15. Conclusion
• System performance highly depends on solar input (isolation level)
• System efficiency mostly depends on solar collector efficiency
• Ambient temperature is influential to thermal efficiency of the system
• Inlet flow rate is related to outlet temperature
• Pump works against the pressure drop
• Pressure drops is not important to system efficiency
• Good business model may help this industry grow faster
• The cost of the product is important to costumers due to electric bill they
may save after several years
• Control engineering is also important to this system
17. Reference
• http://www.pipeflowcalculations.com/pressur
edrop/index.htm
• http://www.builditsolar.com/References/Calc
ulators/Collector/ColEfic.htm
• Solar water heating project analysis,
Retscreen international
• Solar thermal collector for water heating,
Energy Efficiency Office, Electrical and
Mechanical Services Department, HK
