me165-1_week-2. solar energy_2015-16_3t_2844925

8/17/2019 ME165-1_Week-2. Solar Energy_2015-16_3T_2844925

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ME165-

1

ALTERNATIVE ENERGY RESOURCES

2.Week-2. Solar Energy2015-2016 / 3T


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SOLAR POWER

Solar power is the conversion of sunlight int

electricity, either directly using photovoltaics

indirectly using concentrated solar power (C

Photovoltaics (also known as solar cell) convert

into electric current using the photoelectric effeConcentrated solar power systems use lenses o

and tracking systems to focus a large area of su

into a small beam. (Solar Thermal Conversion).


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PHOTOVOLTAICS CONVERSION SYSTEM

Photovoltaics or Solar Cells

Brief History & Overview

Solar power dates back to the mid 1800s.

Photovoltaic Cells

Alexandre Edmond Becquerel discovered in 1839

photovoltaic effect.

Photovoltaic cells were used mainly for the purpos

measuring light.

Russell Ohl invented the solar cell in 1941.


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Brief History & Overview . . . . .

Currently, solar power is a rapidly developing

source around the world due to the developm

technology such as the solar panel, which uti

energy channelling capacity of the photovolta


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A solar cell, also called a photovoltaic cell (PV

cell), is an electrical device that converts the

energy of light directly into electricity by the

photovoltaic effect.

It is a form of photoelectric cell (in that its

electrical characteristics—e.g. current, voltage,or resistance—vary when light is incident upon

it) which, when exposed to light, can generate

and support an electric current without being

attached to any external voltage source.


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Introduction

The term "photovoltaic" comes from the Greek φῶς (phō

"light", and from "Volt", the unit of electro-motive force, th

which in turn comes from the last name of the Italian ph

Alessandro Volta, inventor of the battery (electrochemica

The term "photo-voltaic" has been in use in English since Photovoltaics is the field of technology and research rela

practical application of photovoltaic cells in producing el

from light, though it is often used specifically to refer to t

generation of electricity from sunlight.


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Introduction . . . . .

Cells can be described as photovoltaic even whe

source is not necessarily sunlight (lamplight, art

light, etc.).

In such cases the cell is sometimes used as a

photodetector (for example infrared detectors), d

light or other electromagnetic radiation near the

range, or measuring light intensity.


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The operation of a photovoltaic (PV) cell requires 3 basic

1. The absorption of light, generating either electron-hole

excitons.

2. The separation of charge carriers of opposite types.

3. The separate extraction of those carriers to an externa


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In contrast, a solar thermal collector collects heat by

sunlight, for the purpose of either direct heating or in

electrical power generation.

"Photoelectrolytic cell" (photoelectrochemical cell), on

hand, refers either a type of photovoltaic cell (like thadeveloped by A.E. Becquerel and modern dye-sensitiz

cells) or a device that splits water directly into hydroge

oxygen using only solar illumination.


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How a solar cell works:

The solar cell works in three steps:

1. Photons in sunlight hit the solar panel and are absorbed by

semiconducting materials, such as silicon.

2. Electrons (negatively charged) are knocked loose from their a

causing an electric potential difference.

Current starts flowing through the material to cancel the po

this electricity is captured.

Due to the special composition of solar cells, the electrons

allowed to move in a single direction.


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SOLAR CELL

The diagram above illustrates the operation of a basic photovoltaic cell, also called a sola

Solar cells are made of the same kinds of semiconductor materials, such as silicon, used

microelectronics industry.

For solar cells, a thin semiconductor wafer is specially treated to form an electric field, po

and negative on the other.

When light energy strikes the solar cell, electrons are knocked loose from the atoms in th

material.

If electrical conductors are attached to the positive and negative sides, forming an electr

electrons can be captured in the form of an electric current -- that is, electricity.

This electricity can then be used to power a load, such as a light or a tool.


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Building block of a solar panel

Assemblies of photovoltaic cells are used to m

solar modules which generate electrical power

sunlight.

Multiple cells in an integrated group, all oriente

one plane, constitute a solar photovoltaic pane

"solar photovoltaic module," as distinguished f

"solar thermal module" or "solar hot water pan


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PHOTOVOLTAIC CELL


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BUILDING BLOCK OF SOLAR PANEL


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Building block of a solar panel . . . . .

The electrical energy generated from solar modu

referred to as solar power , is an example of sola

A group of connected solar modules (such as pri

installation on a pole-mounted tracker system) is

an "array."


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PV System Related Equipment

Photovoltaic modules can be mounted on the ground obuilding roof or can be included as part of the building

structure, usually façade. Related equipment includes

charge controllers, inverters, and peak-power trackers

Batteries. They are required in many PV systems to

power at night or when the PV system cannot meet

demand.

Main types of batteries currently available in the ma

Lead-acid, Nickel-Cadmium, Nickel-Hydride, Lithium


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PV System Related Equipment (cont’d.)

Inverters. Used to convert the direct current i

alternating current electricity. The output of t

inverter can be single or three phase.

Charge Controllers. Regulate the power from

modules to prevent the batteries from overcha

The controller can be a shunt type or series ty

also function as a low-battery voltage disconn

prevent the battery from over-discharge.


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PV System Related Equipment (cont’d.)

Peak-Power Trackers. PV cells have a single operati

where the values of the current (I) and the voltage (V

cell result in maximum power output. These values c

to a particular resistance, which is equal to V/I, as s

Ohm’s law. A PV cell has an exponential relationship

current & voltage, and there is only one optimum op

power point also called a maximum power point (MP

changes according to the radiation intesity and the c

temperature. Maximum power point trackers (MPPT

for this point, thus, allow the converter circuit to extr

maximum power available from a cell.


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PV CELL SYSTEM - APPLICATIONS

Remote Site Electrification

Photovoltaic systems can provide long-term power at

from utility grids.

The loads include lighting, small appliances, water pu

communication equipment.

The load demand can vary from few watts to tens of kPV systems are preferred to fuel generators, since th

depend on a fuel supply, and they do avoid maintena

environmental pollution problems.


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Communications

Photovoltaics can provide reliable power for communsystems, especially in remote locations, away from th

Examples include communication relay towers, travel

information transmitters, cell phone transmitters, rad

stations, emergency call units, and military communic

facilities.

These systems are stand-alone units in which PV-cha

batteries provide a stable DC voltage that meets the v

current demand.


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Remote Monitoring

Because of their simplicity, reliability, and capacity for

unattended operation, photovoltaics are preferred in p

power at remote sites to sensors, data loggers, and as

meteorological monitoring transmitters, irrigation cont

monitoring highway traffic.

The batteries required are often located in the same w

resistant enclosure as the data acquisition or monitor

equipment.


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Water Pumping

Stand-alone photovoltaic systems can meet the need

to intermediate-size water-pumping applications.

These include irrigation, domestic use, village water s

livestock watering.

Advantages of using water pumps powered by photovsystems include low maintenance, ease of installatio

reliability.

Most pumping system do not use batteries but store

pumped water in holding tanks.


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Building-Integrated Photovoltaics (BIPV)

BIPV is a special application in which PVs are installed

the façade or roof of a building and are integral part o

building structure, replacing in each case the particula

component.

To avoid an increase in the thermal load of the buildin

created between the PV and the building element, wh

behind the PV. In this gap, ambient air is circulated so

remove the produced heat.


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Building-Integrated Photovoltaics (BIPV) . . . . . .

A common example where these systems are installecalled zero-energy houses, where the building is an e

producing unit that satisfies all its own energy needs.


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Charging Vehicle Batteries

Photovoltaic chargers keep the battery at a high state

by providing a trickle charging current.

The module can be installed on the roof of a building

or on the vehicle itself.

Another important application in the this area is the umodules to charge the batteries of electric vehicles.


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PV SOLAR PANEL & SOLAR THERMAL PANEL

PV solar panel

A PV solar panel is a packaged, connected asse

photovoltaic cells.

The solar panel can be used as a component of

photovoltaic system to generate and supply elec

commercial and residential applications.

Each panel is rated by its DC output power unde

standard test conditions, and typically ranges fro

to 320 watts.


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PV solar panels

Photovoltaic PanelsConcentrated


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Solar thermal panel

Solar thermal panels transfer the sun's heat, as opposgenerating electricity.

Their most popular application is to heat water.

Subsequently, solar thermal is a great technology to of

usage for your water heater or for heating an outdoor p

Solar thermal power can also be used to heat or cool a

depending on the specific solar thermal technology.

Since most residential heating systems use gas, this s

technology primarily offsets gas usage.


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Solar thermal panel (cont’d.)

Characteristics

One popular type of solar thermal heating system u

filled with water in conjunction with solar thermal

The sun's heat is conducted through the solar therm

to heat the water in the pipes.There are generally two types of these solar therma

active and passive systems.


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Solar thermal panel (cont’d.)

Characteristics

Active systems use pumps and controls to regula

water. Passive systems do not, and they are typic

feasible in mild climates where risks from extrem

temperatures (like freezing) aren't present.There are also solar thermal heating systems tha

homes by radiating the heat from the pipes to w

air.


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Solar thermal panels

Solar Thermal Panels


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Useful Characteristics of Solar Panels

Solar panels can generate electricity without any

pollution, or dependence on the Earths natural

Solar panels have no moving parts so they are v

reliable and have a long life span.Solar panels are relatively easy to install and are

maintenance.



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Useful Characteristics of Solar Panels . . . . .

A useful characteristic of solar photovoltaic powergeneration is that it can be installed on any scale a

opposed to conventional forms of power generatio

require large scale plant and maintenance.

Solar panels can be installed to generate power whneeded which removes the need to transport and d

power over long distances to remote areas.

SO CO S O S S


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SOLAR THERMAL CONVERSION SYSTEM

Solar thermal conversion systems use reflectors

to concentrate sunlight to extremely intense leve(Solar means “of the sun,” thermal means “of he

conversion means “changing something from one

another.”)



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Solar thermal conversion systems use mirrors or

to concentrate sunlight onto containers full of liqSometimes water is used. Sometimes other liqui

used, which retain heat better than water.

The liquids are heated up to high temperatures, and

produces steam.

The steam is used to turn a turbine.

The turning motion of the turbine is used to create el

SOLAR CONCENTRATION CONCENTRATED


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SOLAR POWER (CSP) SYSTEM

Why Use Concentrating Solar Energy Systems?

Solar concentration allows “higher-quality” enebe collected because higher temperatures, an

thereby greater capacity for generating mecha

work, can be achieved.

According to the second law of thermodynamic

higher the operating temperature is, the better

efficiency of a heat engine (for example, the on

CSP plant).



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Why Use Concentrating Solar Energy Systems . . .

The heat engine operating temperature is direcdependent on the solar receiver, or absorber, o

temperature.



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Types of Concentrating Collectors Parabolic Trough Collector

Linear Fresnel Reflector

Parabolic Dish

Central Receiver



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Parabolic Trough Collectors (PTCs)

Parabolic trough power plants use a

curved, mirrored trough which

reflects the direct solar radiation

onto a glass tube containing a fluid

(also called a receiver, absorber or

collector) running the length of the

trough, positioned at the focal point

of the reflectors.

The trough is parabolic along one

axis and linear in the orthogonal

axis.



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Parabolic Trough Collectors (cont’d.)

For change of the daily position of the sun perpendicular to

receiver, the trough tilts east to west so that the direct radi

remains focused on the receiver. However, seasonal chang

angle of sunlight parallel to the trough does not require adj

the mirrors, since the light is simply concentrated elsewhe

receiver.

The receiver may be enclosed in a glass vacuum chamber. significantly reduces convective heat loss.

A fluid (also called heat transfer fluid) passes through the r

becomes very hot.

Common fluids are synthetic oil, molten salt and pressurize



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Parabolic Trough Collectors (cont’d.)

The fluid containing the heat is transported to a heat ewhere about a third of the heat is converted to electric

PTCs are high performance collectors that could delive

temperatures with good efficiency.

They can effectively produce heat at temperatures bet

50oC and 400oC.

PTCs are made by bending a sheet of reflective materi

parabolic shape.

A black metal tube, covered with a glass tube to reduc

losses is placed along the focal line of the receiver.



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How PTCs work:

When the parabola is pointed toward

the sun, parallel rays incident on thereflector are reflected to the receiver

tube (absorber).

The concentrated radiation reaching

the receiving tubes heat the fluid that

circulates through it, thus transforming

the solar radiation into useful heat. Parabolic Trough Collectors(PTCs)

The collector can be oriented in the east-west direction, tracking

from north to south, or in north-south direction, tracking the sun

to west.



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Linear Fresnel Reflector

A linear Fresnel reflectorpower plant uses a series of

long, narrow, shallow-

curvature (or even flat)

mirrors to focus light onto

one or more linear receiverspositioned above the mirrors.

Fresnel Lens Reflector: Made

material and shaped in the w

focus the solar rays to a point



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Linear Fresnel Reflector . . . . .

On top of the receiver a small parabolic mirror c

attached for further focusing the light.

These systems aim to offer lower overall costs b

a receiver between several mirrors (as compare

trough and dish concepts), while still using the line-focus geometry with one axis for tracking.

This is similar to the trough design (and differen

central towers and dishes with dual-axis).




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Linear Flesner Reflector . .

The mirrors also do not need

to support the receiver, so

they are structurally simpler.

When suitable aiming

strategies are used (mirrors

aimed at different receivers

at different times of day), this

can allow a denser packing of

mirrors on available land

area.Fresnel reflect




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Linear Flesner Reflector . .

The mirrors also do not need to support the re

they are structurally simpler.

When suitable aiming strategies are used (mir

aimed at different receivers at different times

this can allow a denser packing of mirrors on aland area.




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Linear Fresnel Reflector . . . .

Relies on an array of linear mirror

strips that concentrate light onto a

linear receiver.

The LFR collector can be imagined

as a broken-up parabolic trough

reflector, but unlike parabolic

troughs, the individual strips need

not be of parabolic shape.

LFRs are mounted close to the

ground, thus minimizing structural

requirements

Fresnel solar power plant P

SOLAR CONCENTRATION & CONCENTRATED



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Parabolic Dish Reflectors (PDRs)

PDR is a point-focus collector that tracksthe sun in two axes, concentrating solar

energy onto a receiver located at the

focal point of the dish.

The dish structure must fully track the

sun to reflect the beam into the thermalreceiver.

Parabolic D

+ Because the receivers are distributed throughout a collector field

parabolic troughs, parabolic dishes are often called distributed r

system.



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Parabolic Dish Reflectors . . . . . .

PDR important advantages:

1. Because they are always pointing at the

sun, they are the most efficient of all

collector system.

2. They typically have concentration ratios

in the range of 600 to 2000 and thus

are highly efficient at thermal-energyabsorption and power conversion

systems.

3. They are modular collector and receiver units that can function

independently or as a part of a larger system of dishes.



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How PDRs work:

1. The receiver absorbs the radiant solar

energy, converting it into thermal

energy in a circulating fluid.

2. The thermal energy can then be

either converted into electricity using

an engine-generator coupled directly

to the receiver or transported throughpipes to a central power conversion

system.

3. PDRs can achieve temperatures in

excess of 1500oC



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Central Receiver Collectors or Helliostat Field

Collectors (HFCs)

For extremely high inputs of radiant energy, amultiplicity of flat mirrors, or heliostats, using

altazimuth mounts can be used to reflect their

incident direct solar radiation onto a common target.

By using slightly concave mirror segments on the

heliostats, large amount of thermal energy can be

directed into the cavity of a steam generator toproduce steam at high temperature and pressure.

The concentrated heat energy absorbed by the

receiver is transferred to a circulating fluid that can

be stored and later used to produce power.

Schematic of

Photo of a




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Advantages of Central Receivers

1. They collect solar energy optically and transfer it to a sreceiver, thus minimizing thermal transport requireme

2. They typically achieve concentration ratios of 300 to 1

are highly efficient, both in collecting energy and in co

to electricity.

3. They can conveniently store thermal energy.

4. They are quite large (generally more than 10 MW) and

benefit from economies of scale.



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Schematic of a Solar Central Receiver Collector (Heliosta




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How it works?

Power from sunlight is generated by focusing energy from a field

tracking mirrors called heliostats onto a central receiver. Liquid on nitrate salt (HTF), which flows similarly to water when

circulated through the receiver, collecting the energy gathered f

The heated salt is then routed to an insulated storage where it i

minimal energy losses.

When electricity is to be generated, the hot salt is routed to heato produce steam used to generate electricity in a conventional

turbine cycle.

The salt is then sent to the cold salt storage tank, ready to be h

sun and reused the following day.




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Schematic of a Parabolic Trough Central Receiver Collect




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How it works?

1. The system operates with two tanks. The storage medhigh-temperature heat storage is molten salt.

2. The excess heat of the solar collector field heats up th

salt, which is pumped from the cold to the hot tank.

3. If the solar collector field cannot produce enough hea

the turbine, the molten salt is pumped back from the

cold tank, and heats up the heat transfer fluid.

SOLAR HEATING COOLING SYSTEM


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Solar heating System

Active solar heating systems use solar energy to heat aeither liquid or air -- and then transfer the solar heat dir

interior space or to a storage system for later use. If the

system cannot provide adequate space heating, an aux

back-up system provides the additional heat.

Liquid systems are more often used when storage is incand are well suited for radiant heating systems, boilers

water radiators, and even absorption heat pumps and c

Both liquid and air systems can supplement forced air s

TYPES OF SOLAR HEATING SYSTEM


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Liquid Base Active Solar

Heating

Solar liquid collectors

are most appropriate for

central heating. They are

the same as those used

in solar domestic water

heating systems.



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Flat-plate collectors are the

most common, but

evacuated tube and

concentrating collectors are

also available.

In the collector, a heat transfer

or "working" fluid such aswater, antifreeze (usually non-

toxic propylene glycol), or

other type of liquid absorbs

the solar heat.



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Flat-plate collectors (cont’d.)

At the appropriate time, a controller operates a circulating puthe fluid through the collector.

The liquid flows rapidly, so its temperature only increases 10

(5.6° to 11°C ) as it moves through the collector.

Heating a smaller volume of liquid to a higher temperature in

heat loss from the collector and decreases the efficiency of t The liquid flows to either a storage tank or a heat exchanger

immediate use.

Other system components include piping, pumps, valves, an

tank, a heat exchanger, a storage tank, and controls.



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Solar Air Heating Systems

Solar air heating systems use airas the working fluid for absorbing

and transferring solar energy.

Solar air collectors can directly

heat individual rooms or can

potentially pre-heat the airpassing into a heat recovery

ventilator or through the air coil of

an air-source heat pump.



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Solar Air Heating Systems (cont’d.)

Air collectors produce heat earlier and later in the day thsystems, so they may produce more usable energy over

season than a liquid system of the same size.

Also, unlike liquid systems, air systems do not freeze, an

leaks in the collector or distribution ducts will not cause

problems, although they will degrade performance. However, air is a less efficient heat transfer medium tha

solar air collectors operate at lower efficiencies than so

collectors.

SOLAR HEATING COOLING SYSTEM


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Solar Cooling Sytem

A typical solar cooling system consists of a common solar therma

up of solar collectors, a storage tank, a control unit, pipes and pu

thermally driven cooling machine, as seen in figure below.

Most collectors used in solar cooling systems are high efficiency c

available in the market today (often double-glazed flat plate collec

tube collectors). A typical layout of a solar cooling plant is shown i

TYPES OF SOLAR COOLING SYSTEM


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Absorption Cooling

Uses solar thermal

energy to vaporize the

refrigerant

In absorption cooling,

heat drives the system,

instead of electricity.



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Two basic types of absorption cooling systems.

The single-stage systems are driven by any warm fluid (nnecessarily water) heated to around 100 degrees Celsiu

The two-stage systems work at around 120 degrees Cel

can use low temperature solar energy to "pre-heat" the a

• A high-temperature energy source (e.g. natural gas or

used in the second cooling stage.



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Dessicant Coolers

Desiccant coolers are the other very popular stylecooling.

Desiccant coolers remove moisture from air.

This does not actually cool the air but reduces th

humidity, making it seem cooler.

These are often used in combination with other t

solar coolers such as vapour compression or eva

which really do lower temperature.



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Dessicant Cooler



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Vapor Compression Cooling

Vapor compression cooling uses solar thermal enoperate a Rankin cycle heat engine, whilst the

evaporative cooling method uses a mechanical d

that takes the heat from the outside air and uses

evaporate water held in pads inside the cooling u

This 'sucks' heat out of the air and the cooled air

into the home by a fan.



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Vapor Compression Cooling



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Passive & Solar Assisted Cooling (cont’d.)

Passive cooling for buildings is mostly relevant to hot clim

zones.

The prime intent of passive cooling is to prevent heat (or

heat flux) from entering the building or remove heat onc

entered.

These concepts use solar energy or other natural cooling(radiative cooling, evaporative cooling, natural ventilatio

The applicability of these depends to a large extent on th

prevailing climatic conditions, for instance, evaporative c

effective in hot and dry climates only.



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Passive & Solar Assisted Cooling

Passive cooling techniques maximize building envelope efficienc

minimizing heat gain from the external environment and by facili

loss to the external environment.

Some commonly used passive cooling concepts are:

a) evaporative cooling,

b) nocturnal radiation cooling,

c) passive desiccant cooling,

d) earth sheltering / berming,

e) earth- cooling



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Nocturnal and Convective Cooling

Ventilation to cool the thermal mass of the building dunight in order to improve comfort during the day is noc

convective cooling.

Givoni’s rule of thumb for nocturnal convective cooling

indoor temperature is less than the outdoor maximum

temperature by nearly half the diurnal range in outdootemperature, providing the envelope and internal gains

modest and thermal capacity is high.



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Nocturnal and Convective Cooling (cont’d.)

Nocturnal convective ventilation is applicable if tmaximum ambient temperature is too high for co

ventilation and the diurnal range is sufficiently la

bring the indoor maximum temperature down int

comfort range.

• For example, if the minimum outdoor temperat

24oC, the threshold value of the maximum out

temperature is 40oC if the indoor temperature

exceed 32oC.



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Evaporative Cooling

Evaporative cooling is a process that uses the effect of evaporatio

natural heat sink.

• Sensible heat from the air is absorbed to be used as latent he

to evaporate water.

• The amount of sensible heat absorbed depends on the amoun

that can be evaporated.


http://en.wikipedia.org/wiki/File:Evaporative_cooler_annotated.svghttp://en.wikipedia.org/wiki/File:Evaporative_cooler_annotated.svg


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Evaporative Cooling (cont’d.)

Evaporative cooling can be direct or indirect; passive

In direct evaporative cooling, the water content of the

increases because air is in contact with the evaporat

• Since high evaporation rates might increase relati

and create discomfort, direct evaporative cooling c

applied only in places where relative humidity is ve



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Evaporative Cooling (cont’d.)

In indirect evaporative cooling, evaporation occurs insid

exchanger and the water content of the cooled air remaunchanged.

Where evaporation occurs naturally it is called passive

evaporation.

• A space can be cooled by passive evaporation where

surfaces of still or flowing water, such as basins or fo

Where evaporation has to be controlled by means of so

mechanical device, the system is called a hybrid evapor

system.

THERMAL STORAGE SYSTEM


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Thermal Storage System is a system that stores thermal en

energy storage reservoirs for later use.

They can be employed to balance energy demand betwe

time and night time.

The thermal reservoir may be maintained at a temperatu

(hotter) or below (colder) that of the ambient environme

The applications today include the production of ice, chior eutectic solution at night, or hot water which is then u

/ heat environments during the day.



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Thermal Storage System (cont’d.)

Thermal energy is often accumulated from activecollector or more often combined heat and powe

and transferred to insulated repositories for use

various applications, such as space heating, dom

process water heating.



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Types of Thermal Storage

Air System Thermal Storage• Although some early systems passed solar-hea

through a bed of rocks as energy storage, this

is not recommended because of the inefficienc

involved, the potential problems with condensa

mold in the rock bed, and the effects of that m

and mold on indoor air quality.



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Air System Thermal Storage (cont’d.)

• Other Storage options for air systems include phachange materilas (PCMs) and water.

oA PCM is a substance with a high heat of fusio

melting and solidifying at a certain temperatur

capable of storing and releasing large amount

energy. Heat is absorbed or released when the

changes from solid to liquid and vice versa; thu

are classified as latent heat storage (LHS) unit



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Air System Thermal Storage (cont’d.)

•

Water can also be used as a storage medium focollectors through the use of a conventional wat

heat exchanger to transfer heat from the air to th

in the storage tank.



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Air System Thermal Storage



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Liquid System Thermal Storage

Liquid systems store solar heat in tanks of water or in th

mass of a radiant slab system. In tank type storage systems, heat from the working flui

to a distribution fluid in a heat exchanger exterior to or w

tank.

Tanks are pressurized or unpressurized, depending on o

system design. Specialty or custom tanks may be necessary in systems

large storage requirements.• They are usually stainless steel, fiberglass, or high temperatur

• Concrete and wood (hot tub) tanks are also options




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Solar Ponds

A solar pond is a pool of saltwater which acts as scale solar thermal energy collector with integra

storage for supplying thermal energy.

It can act both as collector and storage.

A solar pond can be used for various applicationprocess heating, desalination, refrigeration, dryi

solar power generation.



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Schematic of a Solar ond



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How solar pond works (cont’d.):

In a typical freshwater pond, when the sun penetwater the layers that are heated up rise to the to

pond and release the heat into the atmosphere.

• This is how a pond maintains a constant temp

The oxygen in warm water is greater than cold

• This causes warm water to rise to the top of th

body and this heat is then released.



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However, in a solar pond this process does not hInstead the water that is warmed is unable to ris

top due to the salt concentration.

• Therefore, the warm water stays at the bottom

pond and gets hotter and hotter with the more

it receives.

• The bottom layer of a solar pond can reach 17

degrees farenheit.



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What allows a solar pond to be used as an energis that a pipe is placed at the bottom of the pond

draws the warm/ hot water out of the pond by a

is circulated through a piping system that utilizes

It is similar to how radiant heat, or solar hot wate

use the warm water.




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How solar pond works (cont d.):

Once the water has run through the pipe it is deposited

the pond in the storage zone so this water can be heate

This system is a close system so is quite efficient in term

retention. Typically this is how a solar pond is used for h

purposes.

Solar ponds can be used in all climates as Long as ther

of sun. Even when a pond is frozen over, a salient gradiepond still produces hot water.

Therefore, they can be used all over the United States a

world.



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Aerial Picture of a Solar Pond



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Advantages of using solar ponds:

It produces heat or electricity with little to no carbon em

• The emission depends on the type of pump used to

through a turbine or piping.

It is unique in its capability in acting both as collector a

The cost of solar pond per unit area is less than any act

collectors available today. When used for desalinization, no energy is required to p

potable water, instead the clean water is a result of the

of water according to salt concentration.



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Heat Storage Media

Steam accumulator

• The PS10 solar power tower stores heat in tanks as

steam at 50 bar and 285 °C.

• The steam condenses and flashes back to steam, wh

pressure is lowered. Storage is for one hour.

• It is suggested that longer storage is possible, but thbeen proven yet in an existing power plant.


Heat Storage Media (cont’d )


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Heat Storage Media (cont’d.)

Molten salt storage

•

A variety of fluids have been tested to transport the sincluding water, air, oil, and sodium, but Rockwell Int

selected molten salt as best.

• Molten salt is used in solar power tower systems bec

liquid at atmospheric pressure, provides a low-cost m

store thermal energy, its operating temperatures arecompatible with today's steam turbines, and it is non

flammable and nontoxic.

• Molten salt is used in the chemical and metals indus

transport heat, so industry has experience with it.



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Heat Storage Media (cont’d.)

Graphite heat storage

Direct

• The proposed power plant in Cloncurry Australia w

heat in purified graphite. The plant has a power to

The graphite is located on top of the tower. Heat f

heliostats goes directly to the storage. Heat for en

production is drawn from the graphite. This simpli

design.




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Heat Storage Media (cont d.)

Graphite heat storage

Indirect• Molten salt coolants are used to transfer heat fro

reflectors to heat storage vaults. The heat from th

transferred to a secondary heat transfer fluid via

exchanger and then to the storage media, or alter

the salts can be used to directly heat graphite. Grused as it has relatively low costs and compatibili

liquid fluoride salts. The high mass and volumetri

capacity of graphite provide an efficient storage m




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Heat Storage Media (cont d.)

Phase-change material (PCMs)

• PCMs offer an alternative solution in energy storage.

• Using a similar heat transfer infrastructure, PCMs ha

potential of providing a more efficient means of stora

• PCMs can be either organic or inorganic materials.

•

Advantages of organic PCMs include no corrosives, loundercooling, and chemical and thermal stability.

• Disadvantages include low phase-change enthalpy, lo

conductivity, and flammability.

ENVIRONMENTAL IMPACTS OF SOLAR

POWER GENERATION

Climate Change


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Climate Change

The burning of fossil fuels for energy remains the world'

source of carbon dioxide emissions. Solar power is sometimes described as a zero emission

emissions-free form of energy, and it is true that greenh

emissions from solar are negligible.

However, the construction of new utility scale solar ener

is bound to result in some greenhouse gas emissions.

This fact is acknowledged in the Final Environmental Im

Statement for one proposed solar farm in California*1.

*1 Bureau of Land Management: Desert Sunlight Farm Project California Desert Conservation Area Plan Am

Environmental Impact Statement


POWER GENERATION

Water


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Creating energy is a water intensive process.

In the U.S., electricity production accounts for more thapercent of all daily freshwater withdrawals.

Solar photovoltaic systems do not require any water to

electricity . Some solar thermal systems use water, but t

can be reused.

Utility scale parabolic and central tower solar energy syssteam plants to produce power, often relying on water fo

There is some concern that these types of systems, whe

in arid environments, could put a strain on local water r


POWER GENERATION

L d


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Land

When placed on existing structured, such as the rooftop

or office building, solar energy systems require negligiblof land space.

Utility scale solar farms, on the other hand, do require laamounts of land to produce electricity on a commercial

This fact raises concerns about the potential impact of s

projects on natural habitats, concerns the EPA is workinaddress by siting renewable energy projects on contamilands and mine sites.


POWER GENERATION

H d W t


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Hazardous Waste

Solar photovoltaic panels may contain hazardous

materials that could be released when a panel is

or disposed of improperly.

Concentrating solar energy systems may also use

potentially hazardous materials like oils and molt

creating the potential for spills.


POWER GENERATION

Vi l


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Visual

One person's beauty is another person's eyesore

For some, solar panels evoke positive feelings, ev

set in a natural landscape.

For others, the sight of a solar panel invading a p

desert environment is gut wrenching. It's largely a

of opinion.

REFERENCES


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Textbook: Renewable Energy Technologies, Jean-Claude Sabonnadiere, 2009

Web http://en.wikipedia.org/wiki/Solar_hot_water

http://en.wikipedia.org/wiki/Solar_energy

http://en.wikipedia.org/wiki/Solar_power

http://en.wikipedia.org/wiki/Solar_panel

http://www.energymatters.com.au/renewable-energy/solar-power/solar-panels.php

http://www.solcoproject.net/docs/SOLCO_TECHNICAL_FINAL.pdf

http://en.wikipedia.org/wiki/Solar_thermal_energy

http://climatelab.org/Solar_Ponds

http://en.wikipedia.org/wiki/Evaporative_cooler

http://greenliving.nationalgeographic.com/positive-negative-effects-solar-energy-2684.html

Youtube http://www.youtube.com/watch?v=rO5rUqeCFY4&feature=player_embedded

http://www.youtube.com/watch?v=x2zjdtxrisc
http://en.wikipedia.org/wiki/Solar_hot_waterhttp://en.wikipedia.org/wiki/Solar_hot_waterhttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/Solar_panelhttp://en.wikipedia.org/wiki/Solar_panelhttp://www.energymatters.com.au/renewable-energy/solar-power/solar-panels.phphttp://www.energymatters.com.au/renewable-energy/solar-power/solar-panels.phphttp://www.energymatters.com.au/renewable-energy/solar-power/solar-panels.phphttp://www.solcoproject.net/docs/SOLCO_TECHNICAL_FINAL.pdfhttp://www.solcoproject.net/docs/SOLCO_TECHNICAL_FINAL.pdfhttp://en.wikipedia.org/wiki/Solar_thermal_energyhttp://en.wikipedia.org/wiki/Solar_thermal_energyhttp://climatelab.org/Solar_Pondshttp://climatelab.org/Solar_Pondshttp://en.wikipedia.org/wiki/Evaporative_coolerhttp://en.wikipedia.org/wiki/Evaporative_coolerhttp://greenliving.nationalgeographic.com/positive-negative-effects-solar-energy-2684.htmlhttp://greenliving.nationalgeographic.com/positive-negative-effects-solar-energy-2684.htmlhttp://greenliving.nationalgeographic.com/positive-negative-effects-solar-energy-2684.htmlhttp://www.youtube.com/watch?v=rO5rUqeCFY4&feature=player_embeddedhttp://www.youtube.com/watch?v=rO5rUqeCFY4&feature=player_embeddedhttp://www.youtube.com/watch?v=x2zjdtxrischttp://www.youtube.com/watch?v=x2zjdtxrischttp://www.youtube.com/watch?v=x2zjdtxrischttp://www.youtube.com/watch?v=rO5rUqeCFY4&feature=player_embeddedhttp://greenliving.nationalgeographic.com/positive-negative-effects-solar-energy-2684.htmlhttp://en.wikipedia.org/wiki/Evaporative_coolerhttp://climatelab.org/Solar_Pondshttp://en.wikipedia.org/wiki/Solar_thermal_energyhttp://www.solcoproject.net/docs/SOLCO_TECHNICAL_FINAL.pdfhttp://www.energymatters.com.au/renewable-energy/solar-power/solar-panels.phphttp://en.wikipedia.org/wiki/Solar_panelhttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Solar_hot_water

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