Ch 5. SOLAR THERMAL ENERGY CONVERSION SYSTEMS

SOLAR WATER HEATINGSOLAR DISTILLATIONSOLAT THERMAL POWER PLANT Low Temperature Solar Power Plant Medium Temperature Solar Power Plant High Temperature Solar Power Plant CENTRAL RECEIVER POWER PLANTSOLAR PONDSSOLAR PUMPINGSOLAR AIR HEATERSSOLAR FURNACESOLAR COOKERSSOLAR PASSIVE TECHNIQUES

SOLAR WATER HEATING(Thermosiphon System)

• Flat plate collector with transport glass

• Bottom of the tank at least 0.3m top of the collector

• Circulation occurs through natural convection or thermo siphoning

• Heated water with low density rises and flows into the top of the storage tank. The higher density cold water tends to sink and flows lower heater of flat plate

• The density difference provides driving effect

SOLAR DISTILLATION• Converting saline water into distilled

water in solar still.• Blackened basis containing saline

water on which a transparent glass covers.

• Solar radiation passes through cover and energy is absorbed by blackened surface.

• Water is heated and vapor produced is condensed to purified water on cooler interior of roof.

• Condensed water is flowing down the sloping roof and is collected.

Efficiency =W (h2-h1)/H where W = weight of distillated

water per m2 per day h2 - h1 enthalpy change from vapor

to water and H = solar intensity.15-20 liters per day per 10 m2

SOLAR PUMPING:• Utilization of power generated by

solar energy for water pumping, useful for irrigation

• It consists of:• Solar collector- there are two

kinds Flat plate and concentrator collector

• Heat transport system • Boiler or heat exchanger• Heat engine- there are two-

Rotary piston engine and Reciprocating engine.

• Condenser• Pump – Reciprocating and Rotary

pump

Solar Air Heaters

• Getting high temperature by concentrating solar radiation onto a specimen .

• Heliostat: optically flat , polished flat plate

• Spherical reflecting collectors: highly polished aluminum or silver coated surface.

• It produces 2800 0c or maximum heat flux:16000 Kw/m2

• Advantages • Heating is carried out without any

contamination • Temp can be controlled by changing

the position of material in focus• Gives extremely high temp • Provides rapid heating• Limitations• It is limited to sunny days (4-5hrs)• High cost

SOLAR FURNACE

Solar Cooker

SPACE PASSIVE HEATING PASSIVE HEATING SYSYTEMS• Direct gain• (Indirect Gain)Thermal storage wall

• Solar radiation is collected by some elements of structure or admitted directly into building through large south facing windows.

• Which operates without pumps, blowers or any other mechanical devices• Air is circulated past a solar heated surface and through the building by

convection.

THERMAL STORAGE WALL

• A large wall which absorbs solar radiation and stores heat which is placed behind south facing windows

• The air is heated between glass cover and wall. The heated air rises and enters the adjacent room through vents at the top of the wall and air circulates by natural convection

BASIC HOT WATER SYSTEM• Flat plate collector located on the roof

of the building• Heat is transmitted to water in the

storage tank• When the temperature falls below, the

water will pass through auxiliary heater• During normal operation through air

heat exchanger, air is heated and passes through 3 way valve then to the distribution system.

• During cloudy days, air passes through the auxiliary heater then to the distribution system

Advantages:• No temperature drop during transfer of

energy• Requires relatively smaller storage

volume• It can be used in absorption air

conditioner Disadvantages:• Water heater may operate at excessive

high temperature, care must be taken to avoid boiling and pressure build up

• Care must be taken to avoid corrosion problems

BASIC HOT AIR SYSYTEM Advantages:• No freezing problem• Minimum corrosion problem• Since working fluid is air, warm

air heating system is in common Disadvantages:• Relatively higher power cost for

pumping air through storage medium

• Large storage volume

Air Distribution

Electric Power Generation Using Thermal Storage