Seminar

ACKNOWLEDGEMENT
I would like to thank respected MRS. RITU YADAV for giving me such a
wonderful opportunity to expand my knowledge for my own branch and giving
me guidelines to present a seminar report. It helped me a lot to realize of what
we study for.
Secondly, I would like to thank my parents who patiently helped me as

went through my work and helped to modify and eliminate some of the
irrelevant or un-necessary stuffs.
Thirdly, I would like to thank my friends who helped me to make my work

more organized and wellstacked till the end.
Next, I would thank Microsoft for developing such a wonderful tool like MS
Word. It helped my work a lot to remain error-free .
Last but clearly not the least , I would thank The Almighty for giving me
strength to complete my report on time.
PREFACE
I have made this report file on the topic SOALAR REFRIGERATION. I

have tried my best to elucidate all the relevant detail to the topic to be included
in the report. While in the beginning I have tried to give a general view about
this topic. My efforts and wholehearted co-corporation of each and everyone
has ended on a successful note. I express my sincere gratitude to MRS. RITU
YADAV who assisting me throughout the preparation of this topic. I thank him
for providing me the reinforcement, confidence and most importantly the track
for the topic whenever I needed it.
INTRODUCTION
• Need refrigeration in areas not connectedto power grid

• Need to minimize environmental impactand fuel cost
• Evaluate potential of solar energy to meetthese needs
• Evaluate efficiencies of three types ofsolar refrigeration
• Refrigeration systems that use environment-friendly refrigerants provide
a sustainability advantage when compared to other refrigerant selections.
• However, the energy use associated with refrigeration system operation
and the environmental impacts associated with its generation and
distributions often outweigh the choice of refrigerant.
• To minimize environmental impacts associated with refrigeration system
operation, it is reasonable to evaluate the prospects of a clean source of
energy.
CONVENTIONAL REFRIGERATION
Vapor Compression Cycle

Prior to discussing how solar energy could potentially provide refrigeration, it is
appropriate to review the basic principles of operation for vapor compression refrigeration
cycles that form the foundation for nearly all conventional refrigeration.
A schematic of the vapor compression cycle is shown in Figure 1a and a corresponding
enthalpy-pressure diagram for the refrigerant.
In the vapor compression cycle, cooling is provided in the evaporator as low
temperature refrigerant entering the evaporatet or as a mixture of liquid and vapor at State 4
is vaporized by thermal input from the load.
The remaining equipment in the system reclaims the refrigerant and restores it to a
condition in which it can be used again to provide cooling. The vapor exiting the evaporator
at State 1 in a saturated (1a) or slightly superheated condition enters a compressor that raises
the pressure and, consequently, the temperature of the refrigerant. The high pressure hot
refrigerant at State 2 enters a condenser heat exchanger that uses ambient air or water to
cool the refrigerant to its saturation temperature prior to fully condensing to a liquid at State.
The high-pressure liquid is then throttled to a lower pressure, which causes some of the
refrigerant to vaporize as its temperature is reduced. The low temperature liquid that
remains is available to produce useful refrigeration. The major energy input to a vapor
compression refrigeration system is the mechanical power needed to drive the compressor.
The minimum compressor power is given in Equation 1.
The compressor power requirement is substantial because the specific volume of the
refrigerant vapor, v, is large. Additional power is needed to operate the fans or pumps to
move the external fluids. (1) The figure of merit for a vapor compression refrigeration
system is its coefficient of performance (COP) defined as the ratio of the cooling capacity to
the total electrical power required. The COP for a system providing refrigeration at –10°C
(14°F) while rejecting heat to a temperature at 30°C (86°F)
TYPES OF SOLAR REFRIGERATION :-
• Photovoltaic Operated Refrigeration Cycle

• Solar Mechanical Refrigeration
• Absorption Refrigeration
Efficiency metric:
PV REFRIGERATION
• Vapor compression cycle with power inputfrom Photovoltaic cells

• DC electric power output from PV runs thecompressor of a conventional
cycle
• Considerations
– Must match voltage imposed on PV array tothe motor
characteristics and power requirements of the refrigeration cycle
PV
• For given operating condition (solar radiation and module temperature),

single voltage provides maximumpower output
• Must find compressor motor closely matched to theelectric
characteristics of the PV module
SOLAR MECHANICAL REFRIGERATION :-
• Vapor compression cycle with power input fromsolar Rankine cycle

• Considerations
– Efficiency optimization based on delivery temperature
 Efficiency of Rankine cycle increases withincreased heatexchanger
temperature
 Efficiency of solarcollector decreases with increase in temperature

SOLAR MECHANICAL
ABSORPTION REFRIGERATION :-
• Condenser, throttle, evaporator functionexactly the same way

• Replaces compressor with “thermalcompression system”
– Ammonia is working fluid
– Minimal mechanical power input (pumpinstead of
compressor)
– In this regard, significantly different and less
ABSORPTION
Thermal Compression System:-
 Absorption into water solution allows it to be pumped

 Desorbed in generator(rectifier required to separate out water)
 Heat into generatorprovided by solar collectors
 This system greatly increases complexity
The innovation uses a variable speed, direct current (DC) vapor compression cooling
system, connected to a solar photovoltaic (PV) panel via novel electronic controls.
This environmentally friendly system is ideal for use in commercial or household
refrigerators, freezers, vaccine coolers, or solar ice-makers. It is particularly ideal for
off-grid applications.
BENEFITS
 Environmentally friendly:- Harnesses the energy of the sun to reduce dependence on

fossil fuels and eliminates the need for batteries that can be damaging to the Earth
upon disposal.
 Longevity: - Operates continuously for years as proven by prototype units tested at

various locations around the world.
 Scalable:- Suits applications in a wide range of sizes, from portable 50-liter coolers to
building-size air-cooling
Applications
1. Refrigerators
2. Freezers
3. Ice-makers
4. Coolers
5. Building air-cooling systems
Technology Details
How it Works:-
Johnson Space Center's solar-powered refrigeration system employs a PV panel, vapor

compressor, thermal storage and reservoir and electronic controls. The process that makes the
refrigeration possible is the conversion of sunlight into DC electrical power, achieved by the PV
panel. The DC electrical power drives the compressor to circulate refrigerant through a vapor
compression refrigeration loop that extracts heat from an insulated enclosure. This enclosure
includes the thermal reservoir and a phase change material. This material freezes as heat is
extracted from the enclosure. This process effectively creates an "ice pack," enabling
temperature maintenance inside the enclosure in the absence of sunlight.
Proper sizing of the highly insulated cabinet, phase change thermal storage, variable speed
compressor, and solar PV panel allow the refrigerator to stay cold all year long. To optimize the
conversion of solar power into stored thermal energy, a compressor control method fully
exploits the available energy. Other power optimization measures include:-
 Smoothing the power voltage via a capacitor, providing additional current during compressor
start-up
 Monitoring the rate of change of the smoothed power voltage using a controller to determine
if the compressor is operating below or above the available power maximum, enabling
adjustment of the compressor speed if necessary.
 Replacing the capillary tube in the refrigerator system with an expansion valve, improving
energy efficiency in certain operating conditions
These adjustments to the compressor operation contribute to the conversion of the majority of
the available solar power into stored thermal energy. Applications may include a cold side water
loop or incorporation of the evaporator into the thermal storage. Electronic controls also can be
added.
Why it is Better
The standard use of AC electricity supplied by the electric utility to power a single-
speed vapor compression cooling system in a moderately insulated cabinet ties
refrigerators to an electric grid and limits where they can be used. This prohibits their
use in off-grid applications and maintains a dependence on fossil fuels for power. For
these reasons, the demand for solar appliances of all kinds is increasing. However,
other existing solar refrigerators use batteries, presenting a number of disadvantages.
Batteries add expense, and their use and disposal cause undesirable maintenance and
environmental consequences. Heat-driven cooling systems, such as absorption cycle,
can also be solar powered, but their thermodynamic efficiency is not as good as vapor
compression, they require more complex solar collectors, and they do not scale down
in size as well.
In contrast, the solar-powered refrigeration system developed at Johnson Space Center
is environmentally friendly because it eliminates the need for an electric grid or
batteries and provides enough reserve thermal storage for cooling in the absence of
continual sunlight.
Conclusion
• COP for solar refrigeration systems is low
– Better metrics: size, cost
– Complexity of solar ref. systems requiresmore size, bulkiness
– Low operating costs do not outweigh highinitial investment
• Advantage is that they don’t rely on powergrid (PV is most practical for
small scale).

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ACKNOWLEDGEMENT

Secondly, I would like to thank my parents who patiently helped me as

Thirdly, I would like to thank my friends who helped me to make my work

I have made this report file on the topic SOALAR REFRIGERATION. I

• Need refrigeration in areas not connectedto power grid

Vapor Compression Cycle

• Photovoltaic Operated Refrigeration Cycle

• Vapor compression cycle with power inputfrom Photovoltaic cells

• For given operating condition (solar radiation and module temperature),

• Vapor compression cycle with power input fromsolar Rankine cycle

 Efficiency of solarcollector decreases with increase in temperature

• Condenser, throttle, evaporator functionexactly the same way

Thermal Compression System:-

 Absorption into water solution allows it to be pumped

 Environmentally friendly:- Harnesses the energy of the sun to reduce dependence on

 Longevity: - Operates continuously for years as proven by prototype units tested at

Johnson Space Center's solar-powered refrigeration system employs a PV panel, vapor

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