2. What is Refrigeration?
Refrigeration is a process in which work is done to move heat from one
location to another.
Where it is uses:
To provide refrigeration for food and medicine preservation.
To provide comfort cooling.
Solar Refrigeration:
Refrigerator which runs on electricity provided by Solar Energy is
known as solar refrigeration.
Solar-powered refrigerators may be most commonly used in the future
generation.
Developing the world to help mitigate poverty and climate change.
3. Types of Refrigeration:
Refrigeration systems is broadly classified into two
types:
โข Vapour Compression Refrigeration (VCR)
(uses mechanical energy).
โข Vapour Absorption Refrigeration (VAR)
(uses thermal energy).
4. Vapour Compression Refrigeration:
โข Highly compressed fluids tend to get colder when
allowed to expand.
โข If pressure high enough,
Compressed air hotter than source of cooling
Expanded gas cooler than desired cold temperature
6. Type of refrigerant:
โข Refrigerant determined by the required cooling temperature.
โข Chlorinated fluorocarbons (CFCs) or freons: R-11, R-12, R-
21, R-22 and R-502.
Two advantages:
โข Lot of heat can be removed (lot of thermal energy
to change liquid to vapour)
โข Heat transfer rate remains high (temperature of
working fluid much lower than what is being
cooled)
7. Vapour absorption Refrigeration:
โข The vapor absorption refrigeration system comprises of all
the processes in the vapor compression refrigeration system like
compression, condensation, expansion and evaporation.
โข In the vapor absorption system the refrigerant used is
ammonia, water or lithium bromide.
โข The refrigerant gets condensed in the condenser and it gets
evaporated in the evaporator.
โข The refrigerant produces cooling effect in the evaporator and
releases the heat to the atmosphere via the condenser.
9. Advantages of vapour absorption cycle:
(i) Moving part is pump
(ii) Reduced vaporization pressure & temperature
(iii) Load variation does not affect performance
(iv) Capacity > 1000 T, 30TR 91% electricity saves.
Disadvantages of vapour absorption cycle:
(a) Efficiency is low
(b) Takes long time to produce cooling effect
(c) Kerosene/oil/gas flame gives bad smell.
10. Solar Refrigeration:
Refrigerator which runs on electricity provided by Solar Energy is
known as solar refrigeration.
Solar-powered refrigerators may be most commonly used in the
future generation.
Need of solar refirgeration:
โข Need refrigeration in areas not connected to power grid
โข Need to minimize environmental impact and fuel cost
โข Evaluate potential of solar energy to meet these needs
โข Evaluate efficiencies of three types of solar refrigeration
11. Types of solar refrigeration:
โข Photovoltaic Operated Refrigeration Cycle
โข Solar Mechanical Refrigeration
โข Absorption Refrigeration
Solar cooling can be considered for two related processes:
To provide refrigeration for food and medicine
preservation and
To provide comfort cooling.
12. Photovoltaic Operated Refrigeration Cycle:
Vapor compression cycle with power input from
Photovoltaic cells.
DC electric power output from PV runs the compressor of a
conventional cycle
Considerations:
Must match voltage imposed on PV array to the motor
characteristics and power requirements of the refrigeration cycle
For given operating condition (solar radiation and module
temperature), single voltage provides maximum power output.
Must find compressor motor closely matched to the electric
characteristics of the PV module.
13. Schematic view of a conventional vapor compression cycle driven by solar
photovoltaic:
14. Solar Mechanical Refrigeration
Vapor compression cycle with power input from solar
Rankine cycle.
Considerations:
โข Efficiency optimization based on delivery temperature
โข Efficiency of Rankinecycle increases with increased heat
exchanger temperature
โข Efficiency of solar collector decreases with increase in
temperature.
16. Absorption Refrigeration:
โข Condenser, throttle, evaporator function exactly the same way.
โข Replaces compressor with โthermal compression systemโ.
โข Ammonia is working fluid
โข Minimal mechanical power input (pump instead of
compressor).
โข Absorption into water solution allows it to be pumped.
โข Desorbed in generator (rectifier required to separate out water).
17. โข Heat into generator provided by solar collectors.
โข The pressurisation is achieved by dissolving the
refrigerant in the absorbent, in the absorber section.
โข Subsequently, the solution is pumped to a high pressure
with an ordinary liquid pump.
โข In this way the refrigerant vapour is compressed
without the need of large amounts of mechanical energy
that the vapour-compression air conditioning systems
demand.
โข This system greatly increases complexity.
18. Schematic view of a absorption refrigerator driven by heat from solar
radiation:
19. Benefits:
โข Environmentally friendly
โข Longevity
โข Scalable
Application of solar refrigeration:
โข Solar energy should be given a chance if we want to
protect the environment.
โข We own it to our children, our grandchildren and
the generations to come.
โข Refrigerators
โข Freezers
โข Ice-makers
โข Coolers
โข Building air-cooling systems
20. Conclusion:
โข COP for solar refrigeration systems is low
โข Better metrics: size, cost
โข Complexity of solar ref. systems requires
more size, bulkiness
โข Low operating costs do not outweigh high
initial investment
โข Advantage is that they donโt rely on power
grid (PV is most practical for small scale)
21. Thank you for your attention,
any questions pleaseโฆ.....
