basic knowlede of swh-1

8/9/2019 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

basic knowlede of swh-1

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