Solar water heating integrated with PCM as thermal

SOLAR WATER HEATING SYSTEM
INTEGRATED WITH PCM AS
THERMAL
ENERGY STORAGE
SALEEM MOHAMMED HAMZA
250873614

OVERVIEW
• INTRODUCTION
• REVIEW TABLE
• EXPERIMENTAL SETUPS
• PERFORMANCE ENHANCEMENTS USING PCM
• TEMPERATURE VS TIME
• EFFECT OF FLOW RATE
• EFFECT OF MASS OF PCM USED
• DRAWBACKS
• CONCLUSION

INTRODUCTION
• Solar energy is the most abundant,
cleanest, renewable energy source
available.
• Main Components:
• Solar Collector
• Storage Tank
• Heat Exchanger
• Heat Transfer Fluid
• Expansion Tank
• Heat is stored by increasing the
temperature of water in the form of
sensible heat.

REVIEW TABLE
S.No Name of
Researcher
PCM Used Objectives
1 Kamil Kaygusuz Calcium Chloride
HexaHydrate
(CaCl2.6H2O)
• The effect of latent heat storage in water based
solar heating system.
• Effect of NTU on performance of SWHS with PCM
2 S. Canbazoglu
et al
Sodium Thiosulphate
Pentahydrate
(Na2S2O3.5H2O)
• Thermal performance of an open loop passive
SWHS (natural circulation) and compared its
performance against the conventional system.
3 L.F Cabeza et al Sodium Acetate
Trihydrate PCM
graphite module
(C2H3NaO2.3H2O)
• Compare performance of PCM SWHS with
conventional.
• To study the performance with different amounts
of PCM.
4 Mettawee &
Ghazy
Paraffin Wax • A parametric experimental study of a compact
PCM solar collector to investigate the effects of
water flow rates on performance.
5 Prakash et al Paraffin Wax • The effect of different flow rates and
• Depth of PCM on the performance of the solar
water heating system and compared it with a

EXPERIMENTAL SETUPS
(1) KAMIL KAYGUZUS [1] (2) CANBAZOGLU ET AL [2]
(3) CABEZA ET AL [3]

EXPERIMENTAL SET UPS CONTD…
(4) METTAWEE & GHAZY [4] (5) PRAKASH ET AL [5]

PERFORMANCE ENHANCEMENTS USING
PCM
• Disodium hydrogen phosphate-dodecahydrate is the best pcm for
solar water heating applications followed by sodium sulfate
decahydrate.
• Due to their higher latent heats & specific heat capacity.
• Maximum of 3.45 times of the energy stored using conventional
can be achieved.

TEMPERATURE VS TIME
• PCM CHARGING:
• Temperature of PCM rises gradually as it
gains heat from the solar heated water.
• At melting point of PCM temperature
remains constant.
• This is due to latent heat absorption at
constant temperature (phase change).
• PCM DISCHARGING:
• Temperature of PCM decreases gradually
as it loses heat to the stored water.
• During solidification of PCM temperature
remains constant.
• This is due to latent heat release at
constant temperature (phase change).

CONTD…
• Canbazoglu et al :
• In conventional system, the storage
water temperature decreases as solar
radiation decreases until the sunrise of
the next day.
• In system with PCM, the temperature of
the water decreases indicating PCM
charging.
• Off sunshine hours, the water in the
tank gains temperature and remains
constant due to latent heat release by
PCM.
• Since no hot water was extracted, the
temperature of water in the storage

EFFECT OF FLOWRATES
• The efficiency of the system decreases with increase in the flow rates. Thus, Time for
which the energy is stored and supplied is less.
• Due to:
• Low thermal conductivity of solid paraffin wax.
• More water carries away more heat from the PCM, thereby generates hotter water but
reduces the time for which the energy is stored in the system.
*Average efficiency with varying flow rates from Prakash et at experiments[5] ** Mettawee & Ghazy
results[4]
System Studied 20 l/hr 30 l/hr
Conventional
Storage water
heater
38.04 33.29
Storage water
heater with 2cm
PCM
50.44 47.46
Storage water
heater with 4cm
PCM
61.36 59.86

EFFECT OF MASS OF PCM
• Increase in the amount of PCM used in the system increases the time for
which the energy is stored.
• More PCM extracts more heat from water. thus, low water temperature during
PCM charging.
• There is an optimal value after which the efficiency would drop.
Effect of Mass of PCM on Storage energy time from Cabeza et al experiment[3]
No. modules PCM mass (kg) Volume occupied (%) Storage Energy Time
(hrs)
2 2.1 2.05 2
4 4.2 4.1 2.30
6 6.3 6.16 2.45

CONTD..
• Kaygusuz graph:
– As NTU increases, fluid outlet temperatures decreases
during charging of
PCM .
– Increase in NTU increases the storage energy time.
• Prakash et al graph:
– The peak temperature of the water in storage tank
decreases as mass of
PCM increases.
– Hot water was generated for longer time as mass of PCM
was increased.
Conclusion:
– Lower fluid outlet temperatures, as PCM extracts more heat
from water
during charging process.

DRAWBACKS
• Kaygusuz considered the PCM to behave ideally, thus neglecting
problems such as phase segregations and super cooling.
• Canbazoglu et al observed that the PCM lost its ability to change
phase after 25-30 cycles of solidifying and melting process.
• Canbazoglu et al could have used a closed system with forced system
using a pump to enhance efficiency rather than using a open loop
passive system.
• Salt hydrates absorb moisture, thereby requiring expensive
encapsulation methods. Increases total cost of the system.
• Storage water temperature of systems with PCM is always less than
60C which leads to legionella growth in the tank. No control
measures where discussed to prevent its growth.
• Thermal losses from the collector where not taken in consideration.

CONCLUSION
• Integrating PCM in solar water heating systems is of great benefit.
• The best salt hydrates among those studied for solar water heating application
is disodium hydrogen phosphate dodecahydrate.
• As high as 3.45 times of mass of hot water was generated using PCM when
compared to the conventional system.
• The PCM stores the energy from the solar heated water during sunshine hours.
During off sunshine hours the water gets heated by the PCM. This is a
isothermal process due to large energy absorbed or released due to latent heat
of PCM.
• Flow rates – decreased efficiency of the system but higher temperature of water
at the outlet. Energy storage time decreased.
• Mass of PCM used – Increased the energy storage time of the system, but lower
temperatures of storage water during charging process.
• The use of PCM reduces the storage tank volume required to store the same

REFERENCES
• Kayugz k, et al. experimental and theoretical investigation of latent heat storage for water
based solar heating systems. energy convers manage 1995;36(5):315–23.
• Canbazoglu S, S¸Ahinaslan A, Ekmekyapar A, Gokhan Aksoy Y, Akarsu F. enhancement of
solar thermal energy storage performance using sodium thiosulfate pentahydrate of a
conventional solar water-heating system. energy build 2005;37:235–42.
• Cabeza LF, Ibanez M, Sole C, Roca J, Nogues M. experimentation with a water tank
including a PCM module. solar energy mater solar cells 2006;90:1273–82.
• Mettawee E-BS, Assassa GMR. experimental study of a compact PCM solar collector.
energy 2006;31:2958–68.
• Prakash J, Garg HP, Datta G. A solar water heater with a built-in latent heat storage.
energy convers manage 1985;25(1):51–6.

Solar water heating integrated with PCM as thermal

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