In expressing this concern as part of our
daily activity and in acting upon this premise, we endeavour to be recognised
as exemplary in this field. We look forward to take this iniatative
forward. We do believe that everyone has the necessary
expertise that we could harness in our endeavours .We are looking at
partners who could with their strengths further the cause of Renewable Energy
What
is Solar Energy ?
Using solar power to produce electricity is
not the same as using solar to produce heat. Solar thermal principles
are applied to produce hot fluids or air. Photovoltaic principles are
used to produce electricity. A solar panel (PV panel) is made of the natural
element, silicon, which becomes charged electrically when subjected to sun light.
How much electricity and money can be saved?
The table below gives approximate likely
electricity and money savings for typical 100 Liters per day solar water
heating systems located in different parts of the country. Likely savings of
electricity and money by use of a 100 liters domestic solar water heater (using
2.0 sq.m collector area)
* The use pattern and savings for
southern region pertains to the typical climate of Bangalore,
while those for western region
relate typically to Pune climate.
REGIONS
|
Northern
|
Eastern
|
Southern
|
Western
|
Region
|
Region
|
Region*
|
Region*
|
Expected
no. of days of use per year
|
200 days
|
200 days
|
250
days
|
250
days
|
Expected
yearly electricity saving with use of full capacity,
kwh
|
950
|
850
|
1200
|
1300
|
Monetary
savings at
different prices of electricity, Rs/year
|
Rs.
4/kwh
|
3800
|
3400
|
4800
|
5200
|
Rs.
5/kwh
|
4750
|
4250
|
6000
|
6500
|
Rs.
6/kwh
|
5700
|
5100
|
7200
|
7800
|
How much sunshine will I need?
Solar panels are directed at solar south in
the northern hemisphere and solar north in the southern hemisphere (these are
slightly different than magnetic compass north-south directions) at an angle
dictated by the geographic location and latitude of where they are to be
installed. Typically, the angle of the solar array is set within a range of
between site-latitude-plus 15 degrees and site-latitude-minus 15 degrees,
depending on whether a slight winter or summer bias is desirable in the system.
Many solar arrays are placed at an angle equal
to the site latitude with no bias for seasonal periods. How many solar panels
you will need based on the amount of sunshine available daily in your area
It is presumed that at "peak sun", 1000 W/mē of power reaches
the surface of the earth. One hour of full sun provides 1000 Wh per mē = 1
kWh/mē -representing the solar energy received in one hour on a cloudless
summer day on a one-square meter surface directed towards the sun.
An eco-friendly electric generator. Solar
panels generate free power from the sun by converting sunlight to electricity
with no moving parts, zero emissions, and no maintenance. The solar panel, the
first component of a electric solar energy system, is a collection of
individual silicon cells that generate electricity from sunlight.
ESTIMATES
OF
REQUIREMENTS OF HOT WATER - SOME USEFUL THUMB RULES
|
Application
|
Typical
Requirement of Hot Water at 60OC.
|
|
Household
bathing using buckets
|
10-20
liters per person per bath.
|
Household
bathing using shower with a mixing tap
|
20-30
liters for 10-15 minute bath
|
Shaving,
while a tap runs
|
7-10 liters
|
Household
bathing in bathtub (one filling)
|
50-75
liters
|
Wash basin
with a mixing tap (hand wash, brushing of teeth, etc.)
|
3-5 liters
per person per day.
|
Kitchen
washing
|
2-3 liters
per person per day.
|
Dishwasher
|
40-50
liters per wash cycle
|
Clothes
washing machine
|
40-50
liters per cycle
|
All the estimates
are given for hot water
at 60OC. This hot water has to be mixed with cold water to bring down its
temperature to endurance limits. Mixing will also increase quantity to actually
required values.
Why
should one go for solar water heating?
Because--
Solar water
heaters save electricity and thus money; electricity is becoming more and more
expensive; they could even turnout to be more reliable than electric power
supply (at least in many parts of our country); they are clean and green and
thus reflect one's commitment for preservation of environment; they are safer
than electric geysers as they are located on the roof; and, if well designed,
may even look good on the house top.
Do they
really work?
Of
course they do. After
all, more than 20,000 domestic systems are being installed every year all over
the country.
Is
their working difficult to understand for a layperson/ How do they work?
The working of solar water heaters is very simple
to understand. Two common phenomena observed in everyday life are the key to
functioning of solar water heaters. These are, first, a black surface heats up
when left in the sun, by absorption of solar radiation; and second, the inside
of a car becomes very hot, if it is left in the sun with windows closed. A car
becomes hot in sun because solar radiation can pass through the glass windows
but cannot come out. It is trapped inside and thus heats up the car. The heat
trapping principle is the famous Green House Effect. The good absorption
property of black surfaces is used to improve solar energy absorption in a
solar heater. These two phenomena are utilized in flat plate collectors of
commonly available solar water heaters. A typical domestic solar water heater
consists of a hot water storage tank and one or more flat plate collectors. The
collectors are glazed on the sun facing side to allow solar radiation to come
in. A black absorbing surface (absorber) inside the flat plate collectors
absorbs solar radiation and transfers the energy to water flowing through it.
Heated water is collected in the tank which is insulated to prevent heat loss.
Circulation of water from the tank through the collectors and back to the tank
continues automatically due to density difference between hot and cold water
(thermosyphon effect).
What is a
flat plate collector?
It
is the heart of a solar
water heating system. It consists of an absorber plate which is coated on its
sun facing surface with an absorbent coating, also called selective coating.
The absorber consists of a grid of metallic tubes and sheets. Water flows
through the tubes. Sheet absorbs the solar radiation falling on it and
transfers it to water. The absorber plate is placed in a top open box to
protect it from weather. The space between back and sides of the absorber and
the box is filled with insulation to reduce heat losses. The front of the box
is covered with a high transmittance glass plate. Flat plate collectors are
specified on the basis of their area and are of commonly 1x2 m size
Are
there any other types of collectors?
Flat plate collectors are the most common type
used in the domestic solar water heating systems, specially in India, in view of their cost economics. Evacuated tube collectors have
also been proposed for domestic solar water heating systems, but are not
commonly available. Concentrating collectors are
likely to be more useful for higher temperature
applications such as power generation and industrial use.
What
should one look for in a good flat plate collector?
Bureau
of Indian standards
has laid down specifications of flat plate collectors for use in solar water
heating systems and thus the IS mark is an assurance on use of proper
materials. The important characteristics are, the materials of construction of
the absorber plate, the type of absorbent coating on it, the quality of the
glass plate used, the material of the box, the insulation thickness, etc.
What are
the desirable characteristics of hot water storage tank?
The
hot water storage tank
in domestic solar water heating systems is typically a double walled tank. The
space between the inner and the outer tanks is filled with insulation to
prevent heat losses. The inner tank is generally made of copper or stainless
steel to ensure long life. The outer tank could be made of stainless steel
sheet, painted steel sheet or aluminum.
Electrical heating elements controlled by
thermostats can be provided as an option in the tank itself to take care of
those days when sun is not there or demand of water has gone up. The capacity
of the tank should be in proportion to the collector area used in the system. A
commonly used thumb rule is to provide 50 liters of storage for every sq. m of
collector area. Too large or too small tanks are both detrimental to efficiency.
How
does one identify a good solar water heater?
First and foremost requirement of a good solar
heater is that it should have sufficient collector area for the capacity
claimed. Collector area used in the system determines the capacity of water heating.
Fox example, in typical north Indian weather conditions, on a sunny winter day,
a sq. m. of collector area can be expected to heat around 50 liters of water by
a temperature of 30-40 C. Typical flat plate collectors made in the
country have an area of around 2 sq. m and are thus capable of heating around
100 liters of water in a day. This proportion serves as a benchmark.
Further, the collectors should use good materials and the absorbers should
carry a good quality coating (BIS approved collectors are being provided by
large number of established manufacturers). The system should be mounted on a
rigid structure and should be firmly fixed with the roof to prevent damage in
high winds.
How
big a system should one purchase?
The fundamental rule is that it is better to buy
a system smaller than your requirement and use back up when you fall short of
hot water, rather than buy a system much bigger than your requirement (because
you can afford it). This will lead to inefficiencies and may even cause operational
problems. The best is to make an actual estimate of daily demand of hot water
by measurements on the main use points. Do remember that the solar system is
capable of heating only an approximately fixed quantity of water and is
designed for typical sunny days. Thus in this characteristic it is unlike an
electric geyser which can supply widely varying quantities of hot water in a
day. Also remember that the temperature of water in the solar system is
determined by the combination of collector area and the tank capacity.
Typically it would be 50 – 60 C, which is much hotter than the bathing water
temperature (around 40 C). Estimation of your demand can also be made with
the help of the table given below. As a typical example on sizing of solar
systems, it may be mentioned that a 100 liters system is considered generally
optimum for family of 4 adult members.
How
much would a solar water heater cost?
The total cost of a solar water heating system is
dependent upon many things. These include, the capacity, the kind of back-up
used, the materials used for the inner and outer tanks, the length of
distribution piping required to take hot water to the bathrooms, and not
insignificantly, the brand value. Typically, for an Indian make system with
single BIS approved flat plate collector of 2 sq. m area, the current market
costs are reported to be in the range of Rs. 15,000-20,000, excluding the
distribution piping. However this range is indicative, and could vary from
manufacturer to manufacturer.
What are
the site requirements for installation of a solar water heating system?
The basic requirement for functioning
of a solar system is availability of unobstructed sunlight for the whole day.
Typically, domestic solar water heating systems are installed on the roof of
the house. The collectors of the system have to face the sun and hence should
be oriented due south for maximum interception of sunlight. Thus there should
be no obstruction to sunlight in the south, west and east directions in that
order of preference (an arc of about 120, 60 both sides of the southern direction should
ideally be shadow free). As a thumb rule, the requirement of shadow free area
is around 3 sq. m for each 1 x 2 m collector used. As far as possible, the area
should be flat, away from rain water drains and as far as possible, close to
the bathrooms where hot water is to be supplied. Cold water should be available
at the height of around 2.5 m from the base of the system
Can
the system be installed somewhere other than on the roof?
The system can also be installed on a bracket on
a south facing wall, close to the bathrooms. However, the installation is
difficult and leads to extra cost. The fixing of the system to the bracket
should be proper. Access to the system for repairs should also be ensured. Cost
of hot water distribution piping could be reduced in such installations as the
system will be close to the use point.
How
can the system be installed in multistoried buildings?
In multistoried buildings even if the space for
installation can be made available on the roof, and the systems are installed
there, the piping from the system to the use point will become long leading to
extra cost as well as to extra heat losses. A better option in such cases could
be installation of the systems on the wall mounted brackets, close to the
bathrooms. However, this has not been practiced frequently in India
What
would happen if water supply is irregular ?
A regular cold water supply, at a height of
around 2.5 m is necessary for functioning of the solar system. In case cold
water is not available continuously, a separate cold water tank may have to be
installed , at least equal in capacity to the capacity of the solar system. In
case cold water supply is interrupted during the day, the heating of water by
the solar system may not be affected significantly, although hot water cannot
be drawn for use till the water supply is restored.
What
would happen on cloudy days?
The heating of water by the solar system will
obviously be affected. If it is so cloudy that energy received from the sun is
almost zero, the output of solar collectors also will be nil. On partially
cloudy days some output can be expected. But, the system can be designed with a
suitable electrical back up heater to take care of hot water demand on cloudy
days.
What is
the expected life of a solar water heater?
Typical solar water heaters made using materials
as per BIS specifications could last for 15 -20 years depending upon the
general upkeep, etc.
Is
any electricity required for operation of the solar water heater?
Domestic solar water heaters work on the
principle of thermosyphonic action in which water circulates through the system
by virtue of density difference between hot and cold streams. No electricity is
required for circulation of water or for any other operation in such systems.
However, in case a back up heater is provided to take care of hot water
requirement during cloudy days, electricity will be required.
How long will the water heated by
solar energy remain hot in the tank? Will one get hot water in early morning
when sun is not there?
Hot water produced by the solar system during the
day is stored in an insulated storage tank. The insulation of the tank is such
that water should remain hot without significant drop in temperature for around
24 hrs. Thus water heated during the previous day should be available for use
in the next morning.
Are there
any financial incentives from the government on these systems?
The Central Government through its Ministry of
Non-Conventional Energy Sources provides soft loans for installation of
domestic solar water heating systems. These loans are being provided through 7
Nationalized banks and the interest rate on the loans is 5%. The details of the
scheme can be obtained from this website under "soft loan programme or
solar water heating systems ".
Will
the solar system match with the building exteriors?
Though aesthetics are a matter of individual
preference, most domestic solar water heating systems can be either designed to
blend with the building exteriors or can be designed so that they are hidden
from view. If systems are well installed and maintained, they might even add to
the aesthetics.
Who are the suppliers of domestic
solar water heating systems?
We Off
Course
What
are the operational requirements?
Domestic solar systems do not require any special
operational skills. However, if following are observed, the efficiency of
the systems will be maintained at a high level:
Try to consume most of the heated
water at one time - either in the morning or in the evening. Frequent on and
off of the hot water tap would lead to reduced electricity savings. If an
electrical back up is provided in the tank, set the thermostat at the lowest
acceptable temperature.
� In the north Indian climate, hot water may not be used for
bathing in summers. If the system is to be put totally out of use, it should be
drained of water and the collector should be covered. Alternatively, if the hot
water requirement remains in summers also, though at a reduced level, cover the
collector partially.
� Dust deposition on the collector would reduce its efficiency.
Try to get it cleaned at least once in a week.
What are
the maintenance requirements?
Domestic solar water heating system do not need
significant maintenance requirements. Occasional leakages in the plumbing could
be easily repaired by common plumbers. In case quality of water is hard, scale
deposition in the collectors may result over the years. This may require
descaling with acids for which it is best to contact the suppliers. Broken
glass may also have to be replaced by the suppliers. If outside exposed
surfaces are painted, the paint may have to be redone every 2-3 years to
prevent corrosion of the surfaces.
Trouble
Shooting Guide for Domestic Solar Water Heaters
|
Problem faced
|
Probable cause and
remedies
|
No water in the tap
|
No cold water supply
Wall at the outlet of the system
Airlock in Pipes
|
Water not heated at all, although cold
water flow is normal
|
Consumption of hot water may be too high;
|
Check use points and use pattern
|
Collector may be shaded
No flow of water through th Collector
as it might be choked due to scaling; Get
it checked from the manufacture
|
Water not hot enough or
sufficient quantity of hot water is not available
|
Cloudy weather
|
Consumption too high
|
Frequent on-off of hot water tap
|
Collector dirty
|
Vapour lock in the collector which can be removed by
|
allowing it to cool and draining the system
|