Contents

SEMINAR REPORT ON SOLAR COOLING

UNDER THE GUIDENCE: SUBMITTED BY:

MR. DEEPAK AWASTHI RUDRA PRATAP SINGH

(A. PROFESSOR) 071640048

ME 3rd

ACKNOWLEDGEMENTNo task however can be completed without proper guidance and encouragement. I take this opportunity to express my deep thanks and gratitude to all the people who helped me to transform an idea to reality.

First of all I will like to express my heartfelt thanks and gratitude to Assistant professor Mr. Deepak Awasthi.

Last but not the least I will like to thanks my parents, friends who blessed me to encouraging for preparation of seminar.

RUDRA PRATAP SINGH (0716440048)

CERTIFICATE

This is to certify that a seminar report entitled SOLAR COOLING being submitted by RUDRA PRATAP SINGH to Mechanical Engineering Department PSIT Kanpur in partial fulfillment for the award of degree Of Bachelor of Technology, is a record of bonafide work carried out by him under my supervision and guidance.

Mr. Nitin Srivastava(H.O.D.)

Department of Mechanical Engineering

( )

CERTIFICATE

This is to certify that a seminar report entitled SOLAR COOLING being submitted by RUDRA PRATAP SINGH to Mechanical Engineering Department PSIT Kanpur in partial fulfillment for the award of degree Of Bachelor of Technology, is a record of bonafide work carried out by him under my supervision and guidance.

Mr. DEEPAK AWASTHI

(Asst. Professor)

Department of Mechanical Engineering

Contents

Introduction: Why & what is Solar Cooling 1. Solar cooling. 2. Thermodynamic Basics 3. Conventional Cooling Cycle 4. Thermal Solar Cooling Techniques

4.1. Absorption Cooling

4.2. Adsorption Cooling

4.3. Desiccant refrigeration5. Coefficient of Performances.

6. Solar Cooling Path

7. Refrigerants.

8. Electricity-driven systems.

8.1. Stirling engine.

8.2. Thermoelectric cooling.

9. Comparisons.

10. Consumption, performances and costs

10.1. Comparative assessment

10.2. Solar collectors used

10.3. Investment cost

10.4. Performance data

10.5. Consumption of auxiliary equipment 11. Review from the ISES congress.

Introduction:-What is Solar Cooling:-The core idea is to use the solar energy directly to produce chilled water. The high temperature required by absorption chillers is provided by solar troughs. The system doesnt require strategic materials (like in PV systems) and has peak production in the moment of peak demand. Why Solar Cooling?Dramatic increase of air conditioning since the early 80ies

Cost of energy. Issues related to environmental pollution.-Due to energy production.-Due to the use of CFCs and HCFCs. Matches demand with source availability. Crucial for improving life standards in developing countries.Solar Cooling

Solar cooling refers to any cooling system that uses solar power. This can be done through passive solar, solar thermal energy conversion and photovoltaic conversion (sun to electricity). The U.S. Energy Independence and Security Act of 2007 created 2008 through 2012 funding for a new solar air conditioning research and development program, which should develop and demonstrate multiple new technology innovations and mass production economies of scale. Solar air conditioning will play an increasing role in zero energy and energy-plus buildings design. Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available renewable energy on earth. Only a minuscule fraction of the available solar energy is used.Solar powered electrical generation relies on heat engines and photovoltaic. Solar energy's uses are limited only by human ingenuity. A partial list of solar applications includes space heating and cooling through solar architecture, potable water via distillation and disinfection, day lighting, solar hot water, solar cooking, and high temperature process heat for industrial purposes. To harvest the solar energy, the most common way is to use solar panels.

Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.

Thermodynamic Basics:Underlying Physics

Thermodynamics1st Law: The change of internal energy (U) of a system is equal to the heat absorbed (Q), plus the external work (W) done on the system W, Q related to the changes the system experiences when going from an initial to a final state.Thermodynamic Cycle:- EntropyThe concept of entropy was originally introduced in 1865 by Rudolf Clausius. He defined the change in entropy of a thermodynamic system, during a reversible process in which an amount of heat Q is applied at constant absolute temperature T, as

S = Q / T

Clausius gave the quantity S the name "entropy", from the Greek word,, "transformation". Since this definition involves only differences in entropy, the entropy itself is only defined up to an arbitrary additive constant.Thermodynamics - 2nd LawThe most probable processes that can occur in an isolated system are those in which entropy increases or remains constant. In other words:

In an isolated system there is a well-defined trend of occurrence of process and this is determined by the direction in which entropy increases. In other words:

Heat flows naturally from a system of higher temperature to a system of lower temperature.Ideal Carnot Refrigeration Cycle

Conventional Cooling Cycle

Compression

Condensation

Expansion Evaporation

Thermal solar cooling techniques

Absorption cooling techniques: Energy is transferred through phase-change processes.

Adsorption cooling techniques Energy is transferred through phase-change processes.Desiccant Cooling Energy is transferred through latent heat processes.The cooling capacity is based on the physical properties of the cooling fluid that will change phases

At different temperatures, depending on its pressure.Absorption Cooling

Heat Driven Systems

Absorption Refrigerator-

The absorption refrigerator is a refrigerator that uses a heat source (e.g., solar, kerosene-fueled flame) to provide the energy needed to drive the cooling system. Absorption refrigerators are a popular alternative to regular compressor refrigerators where electricity is unreliable, costly, or unavailable, where noise from the compressor is problematic, or where surplus heat is available (e.g., from turbine exhausts or industrial processes). Absorption refrigerators powered by heat from the combustion of liquefied petroleum gas are often used for food storage in recreational vehicles.

Both absorption and compressor refrigerators use a refrigerant with a very low (less than 0F/18C) boiling point. In both types, when this refrigerant evaporates or boils, it takes some heat away with it, providing the cooling effect. The main difference between the two types is the way the refrigerant is changed from a gas back into a liquid so that the cycle can repeat. A compressor refrigerator uses an electrically-powered compressor to increase the pressure on the gas, and then condenses the hot high pressure gas back to a liquid by heat exchange with a coolant (usually air). Once the high pressure gas has cooled, it passes through a pressure release valve which drops the refrigerant temperature to below freezing. An absorption refrigerator changes the gas back into a liquid using a different method that needs only heat, and has no moving parts. The other difference between the two types is the refrigerant used. Compressor refrigerators typically use an HCFC, while absorption refrigerators typically use ammonia.

\

NH3 systems Improved reliability, at low cost, independent control of the cooling medium

Improved pump reliability at low cost

Improved reliability of the fluid level sensors

Increased performance of the various heat transfer processes in the machine

Simplified system concepts

Properties of H2O NH3

LiBr systems

- Increased performance and reduction of cost of solar collectors

- Increased performance and reduction of cost of storage systems (e.g. thermochemical)

Development of low capacity absorption machines

- Development of low capacity air-cooled absorption machines

- Increased performance of the various heat transfer processes in the machine

Properties of LiBr H2O

Absorption machine

Single effect Yazaki machine(10 ton LiBr)

ADSORTION COOLING:-Adsorption is the use of solids for removing substances from gases and liquids the phenomenon is based on the preferential partitioning of substances from the gaseous or liquid phase onto the surface of a solid substrate. The process is reversibleAdsorption Phase 1

Heating and pressurization

The adsorbent temperature increases, which induces a pressure increase, from the evaporation pressure up to the condensation pressure. This period is equivalent to the "compression" phase in compression cycles.

Adsorption Phase 2Heating and desorption +CondensationDuring this period, the absorber continues receiving heat while being connected to the condenser, which now superimposes its pressure. The adsorbent temperature continues increasing, which induces desorption of vapour. This desorbed vapour is liquefied in the condenser. The condensation heat is released to the second heat sink at intermediate temperature.

This period is equivalent to the "condensation" in compression cycles.

Phase 2 Phase 3 Adsorption Phase 3:-

Cooling and depressurization

During this period, the adsorber releases heat while being closed.The adsorbent temperature decreases, which induces the pressure decrease from the condensation pressure down to the evaporation pressure.

This period is equivalent to the "expansion" in compression cycles.Adsorption Phase 4Cooling and adsorption + Evaporation

During this period, the absorber continues releasing heat while being connected to the evaporator, which now superimposes its pressure. The adsorbent temperature continues decreasing, which induces adsorption of vapor. This adsorbed vapour is

Evaporated in the evaporator. The evaporation heat is supplied by the heat source at low temperature.

This period is equivalent to the "evaporation" in compression cycles.

Adsorption Cooling Summary:-

The cycle is intermittent because production of cooling energy is not continuous: it occurs only during part of the cycle When there are two adsorbers in the unit, they can be operated separately and production of cooling energy can be quasicontinuous. When all the energy required for heating the adsorber(s) is

supplied by the heat source, the cycle is termed single effect.Typically, for domestic refrigeration conditions, the COP of single effect adsorption cycles is of about 0.3-0.4. When there are two adsorbers or more, other types of cycles can be designed.

Adsorption Refrigeration

Adsorption refrigeration and heat pump cycles rely on the adsorption of a refrigerant gas into an adsorbent at low pressure and subsequent desorption by heating. The adsorbent acts as a "chemical compressor" driven by heat and is, from this point of view, the "pump" of the system. It consists of a solar collector, a condenser or heat-exchanger and an evaporator that is placed in a refrigerator box. The inside of the collector is lined with an adsorption bed packed with activated carbon adsorbed with methanol. The refrigerator box is insulated filled with water. The activated carbon can adsorb a large amount of methanol vapours in ambient temperature and desorb it at a higher temperature (around 100 degrees Celsius). During the daytime, the sunshine irradiates the collector, so the collector is heated up and the methanol is desorbed from the activated carbon. In desorption, the liquid methanol adsorbed in the charcoal heats up and vaporizes. The methanol vapour condenses and is stored in the evaporator.Helium gas can also be 'pumped' by thermally cycling activated carbon 'sorption pumps' between 4 kelvins and higher temperatures. An example of this is to provide the cooling power for the Oxford Instruments AST series dilution refrigerators. 3He vapour is pumped from the surface of the dilute phase of a mixture of liquid 4He and its isotope 3He. The 3He is adsorbed onto the surfaces of the carbon at low temperature (typically