Basic Knowlede of SWH-1
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Transcript of Basic Knowlede of SWH-1
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Basic Knowledge on Solar Hot water
Systems
Tri Ratna Bajracharya
Institute of Engineering
Tribhuvan University
Email: [email protected]
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colle
ctor
heat storage
heattransportsystem
heat
exchanger
cold water supply
connection tohot water tap
pump
control unit
powersupply
with insulation
expansion
vessel
backup heater
thermostatair releasevalve
(blockable)
pressurereleasevalve
(8 atm)
ch
ec
k
va
lve
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Forced-flow versus natural circulation
SHW systemsforced flow+ better performance+ can be installed in large systems+ allows independent location of collector and hot water tank requires more components
needs electrical energy for pumping and control is more expensive
natural circulation (thermosiphon)+ simple and require less components+ work without active control equipment+ cheaper not suitable for large systems less efficient storage tank must be located above the collec
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Flat-plate collectors
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SWH System Locally Made
Collector
Storage tank
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Open- versus closed-loop SHW
systemsClosed loop+ better performance avoids air bubbles+ Prevents siltation of the collectors+ allows use of antifreeze Some temperature loss needs significantly more components more expensive more difficult to manufacture
Open loop+ simple and require less components
+ Requires less tecnical skill+ Cheaper and less sensitive to flaws not suitable for frost area not suitable for poor quality water
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Energy flow in the collector from the radiation to the
hot water:
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collectorarea reservoir size
4.5 m (3 panels) 250 lreservoir
7.5 m (5 panels) 400 l
reservoir10.5 m (7 panels) 600 l
reservoir
Collector Area sizing Thumb Rule
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The evacuated tube collector - examples
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Evacuated tube collectors - examples
Compound parabolic concentrator (CPC) combined with
evacuated tube
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Conclusions
Characteristics of a good collector:
selective absorber coating
low heat capacity, high heat transfer coefficients
iron-free glass cover
stiff and light casing
sufficient insulation of the back side
no thermal bridges at the connecting pipes
Two options available:flat-plate collectors
evacuated tube collectors
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Application of SolarThermal Energy
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What do we understand by solar thermal technologies?
Solar thermal collectors
Thermal storage and storage materialsSolar assisted space heating
Solar building / solar architecture
Windows and facades
Solar air conditioning
Material researchComplex thermal network systems
Solar thermal power generation
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Use of solar thermal Energy -
Technologies
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Large size collectors - Solar roofs
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Solar roofs
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Solar space heating
Private house,
Kathmandu
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Solar district heating
boilerhouseGttingen,Germany
solar field,
Denmark solar roofs
seasonal
solarstorage
industrialpre-heating
i l
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passive solarheating
passive solar
heating - scheme
HeliotropFreiburg,Germany
transparentinsulation
aircollector
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Solar thermal electricity
parabolictrough
Heliostat
parabolicdish
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Solar desalination &purification