solarthermal applications

8/12/2019 SolarThermal Applications

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SOLAR THERMAL

APPLICATIONS


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SOLAR THERMAL APPLICATIONS

Water Heating

Space Heating

Space Cooling & RefrigerationDistillation

Drying

Cooking and

Power Generation


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Solar Water Heating Systems

Most attractive solar thermal application from an economicstandpoint.

Most of the systems use flat plate collectors.

The hot water is used for domestic purposes or for meetingthe needs of the industries and commercial establishments.

Can be classified into two categories:

a) Natural circulation (Thermosyphon) systems

b) Forced circulation systems


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Natural Circulation System

(Thermosyphon) Main ComponentsLiquid Flat plate collector and Storage tank.

Tank is located above the level of the collector.

As water is heated by solar energy, it flows automatically to the top

of the tank and it is replaced by cold water from the bottom of the

tank.

Hot water for use is withdrawn from the top of the tank.


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Forced Circulation System

When a large amount of hot water is required, forcedcirculation system is used.

Large arrays of FPCs are used. The restriction to use the

storage tank at higher levels are removed.

Water from the storage tank is pumped through the collectorarray, where it is heated and then flow back into the storage

tank.


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Ball float control valve OnOff controllerSenses the temperature difference

between the tank and water at exit and operate the pump.

Provision for Auxiliary Heater

Well suited for offices, industries, hospitals. hotels., etc.


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Forced CirculationOpen loop

system

Water flows from the cold water tank thro the collectorsto an insulated hot water tank from where it is withdrawn

for use.

The control system adjusts the flow rate to meet the temp.requirement.


8/24TEI Patra: 3-18 Intensive ro ram: ICT tools in PV-

Force circulation system-1


9/24TEI Patra: 3-18 Intensive ro ram: ICT tools in PV-

Force circulation system-2


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Large solar water heating

system


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Space HeatingWater system

It is of particular relevance to in colder countries where a significant energy isrequired for this purpose.

In India, northern region in winter.

Heated in solar collector (A) and stored in storage tank (B).

Energy is transferred to the air circulating in the house by means of water-to-

air heat exchanger (E). Two pumps (C ) provide forced circulation between collectors and the tank &

tank and the heat Exchanger.


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Space Heating using Solar Air Heaters

Heat air directly in the collectors.

Heat is then stored in the tank packed with rock, gravel or

pebbles.


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Space Heating (Passive Method)

Thermal energy flow by natural means. The south facing wall of the house is double glazed.

Behind, it is a black concrete wall, which absorbs the suns

radiation and serves as a thermal storage.


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Solar Cooling and

Refrigeration


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Solar Refrigeration

Solar cooling can be considered for two related processes:

to provide refrigeration for food and medicine preservation and

to provide comfort cooling.

Absorption systems are similar to vapour-compression airconditioning systems but differ in the pressurisation stage.

The most usual combinations of fluids include lithium

bromide-water (LiBr-H2O) where water vapour is therefrigerant and ammonia-water (NH3-H2O) systems whereammonia is the refrigerant.


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Space Cooling and Refrigeration


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Absorption systems

The pressurisation is achieved by dissolving the refrigerantin the absorbent, in the absorber section.

Subsequently, the solution is pumped to a high pressure

with an ordinary liquid pump.

The addition of heat in the generator is used to separate thelow-boiling refrigerant from the solution.

In this way the refrigerant vapour is compressedwithout the need of large amounts of mechanicalenergy that the vapour-compression air conditioningsystems demand.


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Solar Distillation


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Solar DistillationConventional basin type still is used. Consists of shallow air tight basin lined with a black, impervious

material which contains saline water.

A sloping transparent cover is provided at the top.

Solar radiation heats up the water and causes it to evaporate.

Resulting vapour rises, condenses as pure water and flows into

condensate channel on the sides.


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SOLAR DRYING

Natural Circulation Dryer

Forced Circulation Dryer


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Solar Drying (natural circulation)

Used for drying of agricultural products. Removes moisture and helps in preservation of the products.

Cabinet type air dryer 50 to 80oC 2 to 4 days dates,

chillies, grapes, apricots, etc.


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Forced Circulation Dryer

used for large scale drying like timbers.


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Solar Cooking

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