Noor Shazliana Aizee bt Abidin
SOLAR ENERGY
SOLAR HEATING
Solar heating harnesses the power of the sun
to provide solar thermal energy for solar hot
water, solar space heating, and solar pool
heaters. A solar heating system saves energy,
reduces utility costs, and produces clean
energy.
 Solar water heaters and solar space heaters
are constructed of solar collectors, and all
systems have some kind of storage, except
solar pool heaters and some industrial systems
that use energy "immediately."


The systems collect the sun's energy to heat air
or a fluid. The air or fluid then transfers solar
heat directly to a building, water, or pool.
These solar
collectors are part
of the solar
domestic hot water
system.
SOLAR WATER HEATING
One of the most cost-effective ways to include
renewable technologies into a building is by
incorporating solar hot water.
 A typical residential solar water-heating system
reduces the need for conventional water
heating by about two-thirds.
 It minimizes the expense of electricity or fossil
fuel to heat the water and reduces the
associated environmental impacts.


Most solar water-heating systems for buildings
have two main parts:
(1) a solar collector and
 (2) a storage tank.


The most common collector used in solar hot
water systems is the flat-plate collector.
Flat-plate collectors are used for residential water
heating and hydronic space-heating installations
Solar water heaters use the sun to heat either
water or a heat-transfer fluid in the collector.
 Heated water is then held in the storage tank
ready for use, with a conventional system
providing additional heating as necessary.
 The tank can be a modified standard water
heater, but it is usually larger and very well
insulated.
 Solar water heating systems can be either
active or passive, but the most common are
active systems.

ACTIVE SOLAR WATER HEATERS
Rely on electric pumps, and controllers to
circulate water, or other heat-transfer fluids
through the collectors.
 Types of active solar water-heating systems:

 Direct-circulation
systems use pumps to circulate
pressurized potable water directly through the
collectors. These systems are appropriate in areas
that do not freeze for long periods and do not have
hard or acidic water.
 Indirect-circulation
systems pump heat-transfer
fluids through collectors. Heat exchangers transfer
the heat from the fluid to the potable water. Some
indirect systems have "overheat protection," which
is a means to protect the collector and the glycol
fluid from becoming super-heated when the load is
low and the intensity of incoming solar radiation is
high.
 The two most common indirect systems are:
 Antifreeze.
The heat transfer fluid is usually a glycolwater mixture with the glycol concentration depending on
the expected minimum temperature. The glycol is usually
food-grade propylene glycol because it is non-toxic.
 Drainback
systems, a type of indirect system, use pumps
to circulate water through the collectors.
 The water in the collector loop drains into a reservoir
tank when the pumps stop.
 This makes drainback systems a good choice in colder
climates.
 Drainback systems must be carefully installed to assure
that the piping always slopes downward, so that the
water will completely drain from the piping. This can be
difficult to achieve in some circumstances.
PASSIVE SOLAR WATER HEATERS
Rely on gravity and the tendency for water to
naturally circulate as it is heated. Because they
contain no electrical components, passive
systems are generally more reliable, easier to
maintain, and possibly have a longer work life
than active systems.
 The two most popular types of passive systems
are:

 Integral-collector
storage systems consist of one or
more storage tanks placed in an insulated box with
a glazed side facing the sun. These solar
collectors are suited for areas where temperatures
rarely go below freezing. They are also good in
households with significant daytime and evening
hot-water needs; but they do not work well in
households with predominantly morning draws
because they lose most of the collected energy
overnight.
 Thermosyphon
systems are an economical and
reliable choice, especially in new homes. These
systems rely on the natural convection of warm
water rising to circulate water through the collectors
and to the tank (located above the collector). As
water in the solar collector heats, it becomes lighter
and rises naturally into the tank above. Meanwhile,
the cooler water flows down the pipes to the bottom
of the collector, enhancing the circulation.
SOLAR POOL HEATING

Solar water heaters can be used to heat
swimming pools and spas.
This pool, is
heated by solar
thermal collectors.
The existing pool filtration system pumps pool
water through the solar collector, and the
collected heat is transferred directly to the pool
water.
 Solar pool-heating collectors operate just
slightly warmer than the surrounding air
temperature and typically use inexpensive,
unglazed, low-temperature collectors made
from specially formulated plastic materials.
 In residential applications where the goal is
usually to extend the swimming season into
spring and fall, heating a swimming pool with
solar energy requires a solar collector that is
50% to 100% of the surface area of the pool.


Maintenance of solar pool-heating systems is
minimal. The systems are pre-engineered and
can be sized for any pool by simply adding
additional solar panels to obtain an adequate
solar collector area.
SOLAR SPACE HEATING

A solar space-heating system can consist of a
passive system, an active system, or a
combination of both. Passive systems are
typically less costly and less complex than
active systems.
PASSIVE SOLAR SPACE HEATING
Passive solar space heating takes advantage of
warmth from the sun through design features,
such as large south-facing windows, and
materials in the floors or walls that absorb
warmth during the day and release that warmth
at night when it is needed most.
 A sunspace or greenhouse is a good example
of a passive system for solar space heating.

PASSIVE SOLAR DESIGN SYSTEMS USUALLY
HAVE ONE OF THREE DESIGNS:
Direct gain (the simplest system) stores and
slowly releases heat energy collected from the
sun shining directly into the building and
warming materials such as tile or concrete.
Care must be taken to avoid overheating the
space.
 Indirect gain (similar to direct gain) uses
materials that hold, store, and release heat; the
material is located between the sun and living
space (typically the wall).


Isolated gain collects solar energy remote from
the location of the primary living area. For
example, a sunroom attached to a house
collects warmer air that flows naturally to the
rest of the house.
ACTIVE SOLAR SPACE HEATING
Consist of collectors that collect and absorb
solar radiation combined with electric fans or
pumps to transfer and distribute that solar
heat.
 Active systems also generally have an energystorage system to provide heat when the sun is
not shining. The two basic types of active solar
space-heating systems use either liquid or air
as the heat-transfer medium in their solar
energy collectors.

Liquid-based systems heat water or an
antifreeze solution in a hydronic collector. Airbased systems heat air in an air collector. Airbased solar heating systems usually employ an
air-to-water heat exchanger to supply heat to
the domestic hot water system, making the
system useful in the summertime.
 Both of these systems collect and absorb solar
radiation, then transfer the solar heat directly
to the interior space or to a storage system,
from which the heat is distributed.

SPACE COOLING
Cooling and refrigeration can be accomplished
using thermally activated cooling systems
(TACS) driven by solar energy.
 These systems can provide year-round
utilization of collected solar heat, thereby
significantly increasing the cost effectiveness
and energy contribution of solar installations.
 These systems are sized to provide 30% to 60%
of building cooling requirements using solar,
with the remainder usually dependent on TACS
fueled by natural gas.

The TACS available for solar-driven cooling include
absorption systems and desiccant systems.
 Generally, solar cooling is not used because of the
high initial costs of TACS and the solar fields
needed to drive them.
 Solar absorption systems use the thermal energy
from a solar collector to separate a binary mixture
of an absorbent and a refrigerant fluid. The
refrigerant is condensed, throttled, and
evaporated to yield a cooling effect, which is then
re-absorbed to continue the cycle.

Double-effect absorption systems (which use
the heat twice in series) are about twice as
efficient as single-effect systems, but require
significantly higher input temperatures.
 Because of the high temperature requirements
of absorption cooling systems, evacuated-tube
or concentrating collectors are typically used.


Solar desiccant systems use thermal energy
from the solar collector to regenerate
desiccants that dry ambient air; they then use
that dry air in indirect and/or direct evaporative
stages to provide cooled air to the load.

The solar heat is used to regenerate the
desiccant, driving off the absorbed water. Some
systems use flat-plate collectors at
intermediate temperatures.
SOLAR ELECTRIC SYSTEMS
Solar electric systems, also known as photovoltaic
(PV) systems, convert sunlight into electricity.
 Solar cells—the basic building blocks of a PV
system—consist of semiconductor materials.
 When sunlight is absorbed by these materials, the
solar energy knocks electrons loose from their
atoms.
 This phenomenon is called the "photoelectric
effect." These free electrons then travel into a
circuit built into the solar cell to form electrical
current.

Only sunlight of certain wavelengths will work
efficiently to create electricity. PV systems can
still produce electricity on cloudy days, but not
as much as on a sunny day.
 The basic PV or solar cell typically produces
only a small amount of power. To produce more
power, solar cells (about 40) can be
interconnected to form panels or modules.
 PV modules range in output from 10 to 300
watts. If more power is needed, several
modules can be installed on a building or at
ground-level in a rack to form a PV array.

PV arrays can be mounted at a fixed angle
facing south, or they can be mounted on a
tracking device that follows the sun, allowing
them to capture the most sunlight over the
course of a day.
 Because of their modularity, PV systems can be
designed to meet any electrical requirement,
no matter how large or how small. You also can
connect them to an electric distribution system
(grid-connected), or they can stand alone (offgrid).

SOLAR CELLS
A solar cell consists of semiconductor
materials. Silicon remains the most popular
material for solar cells, including these types:
 Monocrystalline or single crystal silicon
 Multicrystalline silicon
 Polycrystalline silicon
 Amorphous silicon

The absorption coefficient of a material
indicates how far light with a specific
wavelength (or energy) can penetrate the
material before being absorbed.
 A small absorption coefficient means that light
is not readily absorbed by the material. Again,
the absorption coefficient of a solar cell
depends on two factors:

 the
material making up the cell, and
 the wavelength or energy of the light being
absorbed.
CONCENTRATING SOLAR POWER
Concentrating solar power (CSP) technologies
use mirrors to reflect and concentrate sunlight
onto receivers that collect the solar energy and
convert it to heat.
 This thermal energy can then be used to
produce electricity via a steam turbine or heat
engine driving a generator.
 One way to classify concentrating solar power
technologies is by how the various systems
collect solar energy.

This solar concentrator
has a fixed-focus
faceted dish with a
concentration of about
250 suns. This system
can be used for large
fields connected to the
utility grid, hydrogen
generation, or water
pumping.
Credit: Science Applications International Corporation
/ PIX 13464

4 types of CSP systems
 Linear
Concentrator Systems
 Dish/Engine Systems
 Power Tower Systems
 Thermal Storage

Smaller CSP systems can be located directly
where the power is needed. Single dish/engine
systems can produce 3 to 25 kilowatts of power
and are well suited for such distributed
applications.
Larger, utility-scale CSP applications provide
hundreds of megawatts of electricity for the
power grid.
 Both linear concentrator and power tower
systems can be easily integrated with thermal
storage, helping to generate electricity during
cloudy periods or at night.
 Alternatively, these systems can be combined
with natural gas, and the resulting hybrid power
plants can provide high-value, dispatchable
power throughout the day.

SOLAR DRYERS
Simple solar
dryer

Every solar drier is constructed using the same
basic units, namely:
A
transparent cover which admits sunlight and
limits heat loss (glass or plastic)
 An absorbent surface, made dark in colour, which
takes up sunlight and converts it to warmth, then
giving this warmth to the air within; this can also be
the product that needs drying itself
 An insulating layer underneath
 An air intake and an outlet, by which means the
damper air can be replaced with fresh drier air

In choosing a certain type of drier account
must be taken of the following six criteria:
 the
use of locally available construction materials
and skills
 the investment of the purchase price and
maintenance costs
 drying capacity, holding capacity
 adaptability to different products
 drying times
 (fall in) quality of the end product
Solar drier
directly employed
Solar driers can be constructed out of ordinary,
locally available materials, making them well
suited for domestic manufacture.
Solar driers can be divided into two categories:
1. driers in which the sunlight is directly
employed; warmth absorption occurs here
primarily by the product itself. These are further
divisible into three sorts:
· traditional drying racks in the open air
· covered racks (protecting against dust and
insects)
· drying boxes provided with insulation and
absorptive material
2. Driers in which the sunlight is employed
indirectly. In this method, the drying
air is warmed in a space other than that
where the product is stacked. The
products, then, are not exposed to direct
sunlight. Various sorts of construction are
possible; this design can also be provided
with powered fans in order to optimize the
air circulation.
ADVANTAGES AND DISADVANTAGES OF THE
VARIOUS DESIGNS
Direct drying
 Tradition open-rack drying enjoys four
considerable advantages:
 · it demands a minimum of financial investment
 · low running costs
 · it is not dependent on fuel
 · for certain products the drying time is very
short

On the other hand the products are exposed to
unexpected rain, strong winds and the dust
they carry, larvae, insects and infection by,
amongst others, rodents.
 Moreover, certain sensitive products can
become overheated and eventually charred.
Dried fruit so spoiled necessarily loses its sale
value.

Solar drier indirectly employed
Indirect drying
 The advantages if the indirect system are that:

 the
product is exposed to less high temperatures,
whereby the risk of charring is reduced
 the product is not exposed to ultraviolet radiation,
which would otherwise reduce the chlorophyll levels
and whiten the vegetables.
Faulty stacking of the product to be dried can
lead to condensation;
 rising hot air in the lowest layers becomes
saturated, but cools so quickly as it rises that
the water condenses out again in the upper
layers


This problem can be overcome by
 stacking
the product less high
 stacking it less close together
 a larger collector, higher working temperature,
faster circulation of more air, or
 a deeper collector, the same working temperature
and speed of circulation but more volume.

The higher cost and the complexity of the
indirect method drier are also disadvantages.