Flat plate collectors for solar water heat were population in Florida and southern California in the 1920s.
Photo type Israeli solar water heater, the first commercial company to
manufacture solar water heater due to abundance of sunlight is it used
by 20% of the population by year 1967.
1.2 SOLAR ENERGY
Solar energy is the light which come in
form of electromagnetic radiation. Electromagnetic radition is a wave
like phenomenon that move energy across distance.
Solar energy is the most abundant
continuing source of energy available to the human race. Solar energy is
not being used as primary sources of fuel energy but a large research
and development effort has being underway to develop economical systems
to harness solar energy as a major source of energy particularly for the
heating and cooling of buildings.
Solar has the following advantage
i) It is very attractive
ii) It is non polluting
iii) It is non deflectable (not quickly use)
iv) It is reliable and free.
On the other hand, solar energy has this disadvantage
It is not constant for terrestrial application.
Solar energy can be converted directly into other form of energy in their separate conversion process, they are:
1) THE HELIOTHERMAL PROCESS :
This is absorption of solar radiation and conversion of the energy into
thermal energy is the only solar conversion that has a theoretical
conversion efficiency of 100%
2) THE HELIOCHEMICAL PROCESS: This is the photosynthetic reaction. The reaction is the sources all biomass and fossil fuel.
3) THE HELIOELECTRICAL PROCESS: This is the production of electricity by photovoltaic or solar cells.
It is estimated that the rate at which
solar energy arrives at the earth is about 1.72 x 10MW. The amount of
solar energy incident on a horizontal surface range from 3.5 to 7kwh/m2/day.
About 30% of the total amount is reflected to space, 47% is converted
to low temperature heat and reradiated to space and 23% powers the
evaporation/ precipitation cycle of the biosphere. Less than 1/2 % is represented in the kinetic energy of the wind and waves and in photosynthetic storage in plant.
1.3 USE OF SOLAR ENERGY
Over the years solar energy has been put
to several uses ranging from drying of cloth and agricultural product
to sun tanning the body and of course for food preservation. Other areas
of solar energy use is air conditioning for cooling and heating of a
building for human comfort using absorption cooling system.
Other area of uses of solar energy is
solar cooler, warming pools, operating engine pumps, solar furnace and
generating of electricity.
1.4 PRINCIPLE OF APPLICATION
Energy received from the sun comes in
form of light but not all the rays are visible to human eye. When the
sun radiation hits an object, solid or liquid, these rays are absorbed,
refracted and reflected. The absorbed rays are transformed into thermal
energy which aids the object to get warm and heat is stored in the
When the sun rays strike the mirror or
the glass, it reflects the rays back to other material in its
surroundings obeying the laws of optics, if the mirror or glass is shape
in form of a cylinder or parabola.
The Edge ray principle states that “If a
ray of light is perpendicular to a parabolic surface, it reflects the
rays back to the focal point. If a material for example, absorbent pipe
is placed at the focus, there will be increase of solar energy resulting
to an increase in temperature and if this is done, the rays are said to
be concentrated. This is the principle employed in this project.
1.5 STORAGE OF SOLAR ENERGY
Storage is impedance in the research and
use of solar energy since it cannot be stored in its original form. In
order to use solar energy effectively. The thermal storage systems
incorporate the use of fluid. .Also steam accumulator rocks which are
capable of storing both sensible and latent heat, while chemical energy
storage uses the output of the solar collector to provide a chemical
that can be used until the energy is required like the photovoltaic cell
in the generation of electrical energy from solar radiation.
1.6 ENVIRONMENTAL IMPACTS OF SOLAR SYSTEM
Solar systems are usually considered to
be rather beneficial. One of the reasons for the use of solar energy is
to reduce environmental pollution and associated costs for its control.
However they are a negative impact which has been identified. These are
some of the impacts of solar usage.
1) AIR POLLUTION: The replacements of fossil fuel combustion with solar heat with reduce the emission of pollutants like CO2 NO, SO2,
particulates, and unnamed hydrocarbons. However, certain solar systems
using chemical reactants for storage or organic fluid for heat transport
pose the threat of release of CO, SO2, SO3,
hydrocarbon vapour and other noxious gases. A fire hazard may exist if
overheated, organic working fluids are present near an ignition source
form of air “pollution” exist near focus of larger solar reflectors or
refractors. Human tissue would be destroyed upon only a short contact.
2) LAND USE: One
of the largest impacts of solar collection is the requirement of
relatively large amounts of land. This represents a severe problem in
industrialized area such as the North East of the United States. The
land intensiveness of solar plant is offset to some extent because they
do not generate solid or liquid waste requiring land for disposal.
Collector fields producing shading not normally represented over large
areas. Impacts on the local ecosystem include an increase of shade –
seeking flora, which may impair collector function.
3) THERMAL POLLUTION:
Solar system elumiciate the local thermal pollution produced by fossil
fuel combustion solar flux, formerly reflected or absorbed by the local
environment, is partially collected and transported to a nearby solar-
thermal conversion facility. Hence the thermal effects of solar plant
are minor. If electric power by a solar plant is used hundreds of miles
away in a city, some reductions in the local environment heat budget
1.7 CONCEPT OF HEATER
Solar hot water is water heat by the use
of solar radiation energy. Solar heating systems are generally composed
of solar radiation collector to its point of usage. The systems may be
used to heat water for a wide variety of uses including home, business
and industrial uses.
Most solar water heater require a well
insulated storage tank, solar storage tanks have an additional outlet
and inlet connected to from the collector. The pressure at which all the
water in the heater has been converted to steam.
1.8 STEAM RAISING
Many ways are used to raise steam for
domestic and industrial uses. The chemical energy, which is contained in
a heater fuel, is converted into heat energy when the fuel is burned.
However, if a heating element is used, electrical energy is converted
into heat energy. This heat is transmitted by conduction through the
wall of the heater furnace to the water.
In another way, energy from the sun can
be used to produce steam by focusing the rays on an absorber when water
passes through the absorber. This is the focus of this project.
Heat energy, which produces a rise in
temperature when it is passed into the water, is known as the specific
enthalpy of water (hf). As more heat passes through the water the
temperature of the water does not rise so long as the water is at
atmospheric pressure but the heat is used in vaporizing the water and
converting it into steam and the heat energy is called the specific
enthalpy of evaporation (latent heat of vaporization) denoted as hfg.
The water change to steam as long as heat is added.
The specific enthalpy of dry “saturated” steam at any pressure denoted as hg is given as:
Hg = hf + hfg.
1.9 SOLAR WATER HEATER FOR DOMESTIC USE
- The utilization of solar energy for domestic hot water.
- They can be used in any climate and the fuel they use sunshine is free
- Solar water heating systems use free heat from the sun to warm domestic hot water.
- Solar water heating can now reduce your domestic water.
1.10 THE BENEFIT OF SOLAR WATER HEATER
- HOT WATER THROUGHOUT THE YEAR:
The system works all year round though you will need to heat the water
further with a boiler or immersion heater during the winter months.
- CUT YOUR BILL: Sunlight is free, so once you have paid for the initial installation your hot water cost will be reduced.
- CUT YOUR CARBON FOOTPRINT: Solar hot water is a green renewable heating system and doesn’t release any harmful carbon dioxide or other pollutants.
1.11 SOLAR WATER HEATING TECHNOLOGY
Solar water heating is a simple technology that uses free energy from the sun of heat water generally in collector mount.
There are two type of solar water heater
(Active and Passive). Active system use electric pumps valves and
controller to circulate water or they are more expensive than passive
systems. Passive system move household water or a heat transfer liquid
through the system without pumps.
1.12 WORKING PRINCIPLE OF THE SOLAR WATER HEATER
Solar water heater system use solar
panel glass/mirror called collectors fitted to your tank. These collects
heat from the sun and use it to warm water which is stored in a hot
water tank (cylinder). This is when light ray from the sun strikes the
solar collector and heats the black metal sun strip absorber underneath
the glass cover.
A boiler or immersion heater can then
heat this water further until reaches the temperature set by the
cylinder thermostat this should be set at 60oc.
Larger solar panels can also provide
energy to heat your home as well. Through usually only in the summer
months when home heating is unnecessary.