This document provides information about solar water heaters produced by the Centre for Application of Renewable Energy. It discusses the environmental benefits of solar water heaters including reducing carbon dioxide emissions. It provides details on the typical costs, payback periods when replacing electricity, furnace oil or coal, and estimated fuel savings. Solar water heaters can generate hot water using sunlight even on partially cloudy days using heat retained in the storage tank.

1. HOT WATER @ ZERO ENERGY CONSUMPTION
HOT WATER @ ZERO COST
HOT WATER @ LIFE
a solar water heater projection by centre for application of renewable energy
EMAIL : CARE@CARE‐INDIA.COM WEBSITE : HTTP://WWW.CARE‐INDIA.COM

2. SOLAR WATER HEATERS a solar water heater projection by centre for application of renewable ene
HOT WATER @ ZERO ENERGY CONSUMPTION
HOT WATER @ ZERO COST
HOT WATER @ LIFE
ergy

3. a solar
Environmental benefits
A SWH of 100 litres capacity can prevent emission of 1.5 tonnes of carbon dioxide per
year .a Life : 15‐20 years
water heater pro
y 5 y
Approximate cost :
Rs.15000‐ 20,000 for a 100 litres capacity system and Rs.110‐150 per installed litre for
higher capacity systems
ojection by centr
Payback period :
when electricity is replaced 3‐4 years
when furnace oil is replaced 4‐5 years
when coal is replaced 5‐6 years
re for application
5 Fuel Savings :
A 100 litres capacity SWH can replace an electric geyser for residential use and saves
1500 units of electricity annually.
n of renewable ene
Avoided uitility cost on generation
The use of 100 SWHs of 100 litres capacity each can contribute to a peak load saving of
100 KW.
ergy

4. AVERAGE SOLAR INSOLATION DATA a solar
Insolation (from Latin insolare, to expose to
the sun) is the total amount of solar
radiation energy received on a given surface
d i i i I i l ll d l
water heater pro
area during a given time. It is also called solar
irradiation and expressed as "hourly
irradiation" if recorded during an hour or "daily
irradiation" if recorded during a day. The unit
d d b th W ld M t l i l
ojection by centr
recommended by the World Meteorological
Organization is the megajoule per square metre
(MJ/m2) or joule per square millimetre
(J/mm2)
re for application
An alternate unit of measure is the Langley (1
thermochemical calorie per square centimeter
or 41,840 J/m2). Practitioners in the business
f l th it tt h
n of renewable ene
of solar energy may use the unit watt-hour per
square metre (Wh/m2). If this energy is divided
by the recording time in hours, it is then a
density of power called irradiance, expressed in
tt t (W/ 2)
ergy
watts per squaremetre m2).

5. a solar
¾ Solar Hot Water System turns cold water into hot water with the help of
sun’s rays.
¾ Around 60 deg. – 80 deg. C temperature can be attained depending on solar
radiation weather conditions and solar collector system efficiency
water heater pro
radiation, ¾ Hot water for homes, hostels, hotels, hospitals, restaurants, dairies,
industries etc. Can be installed on roof‐tops, building terrace and open
ground where there is no shading, south orientation of collectors and over‐h
dt k b SWH t
ojection by centr
head tank above system
¾ SWH system generates hot water on clear sunny days (maximum), partially
clouded (moderate) but not in rainy or heavy overcast day
¾ Only soft and potable water can be used Stainless Steel is used for small
k h MildS l k i h i i i i id d
re for application
tanks whereas Mild Steel tanks with anticorrosion coating inside are used
for large tanks
¾ Solar water heaters (SWHs) of 100‐300 litres capacity are suited for
domestic application.
b d h h l h l
n of renewable ene
¾ Larger systems can be used in restaurants, guest houses, hotels, hospitals,
industries etc.
ergy

6. a solar
• A Solar Water Heater comprises of an array of solar
collectors to collect solar energy and an insulated
t kt t h t t B th t d t h
water heater pro
tank to store hot water. Both are connected to each
other.
• During the day time, water in solar collectors gets
heated which is either pumped or flown
i ll h h i i l h
ojection by centr
automatically on thermo syphon principle to the
storage tank.
• Hot water then stored in the tank can be used for
various applications.
re for application
• Either by gravity flow or forced circulation, water
from the cold‐water tank enters the solar tank and
fills it up The cold water from the solar tank in turn
flows in the bottom header pipe of the absorber,
n of renewable ene
and into the copper tubes , until all the absorber
tubes and the header at the top of the absorber are
full. The heated water being lighter than the cold
water rises and via the top header pipe of the
ergy
p p p
absorber, flows into the top of the solar tank.

7. a solar water heater projection by centre for application of renewable energy

8. a solar water heater projection by centre for application of renewable energy

9. a solar
• Two types of Solar Water Heaters
are available; one based on flat plate
collectors and the other based on
t d t b ll t Fl t l t
water heater pro
evacuated tube collectors. Flat plate
collector (FPC) based systems are of
metallic type and have longer life as
compared to Evacuated tube
ojection by centr
p
collector (ETC) based system
because ETCs are made of glass
which are of fragile( can be easily
b k d t d) i t
re for application
broken or destroyed) in nature.
• Both these systems are available
with and without heat exchanger.
They can also work with and without
n of renewable ene
y
pump. Systems without pump are
known as thermo syphon systems
and those with pump are known as
f d i l ti t
ergy
forced circulation systems.

10. a solar
• The solar radiation is absorbed by Flat Plate Collectors which consist of an insulated
outermetallic box covered on the top with glass sheet.
• Inside there are blackened metallic absorber (selectively coated) sheets with built in
water heater pro
channels or riser tubes to carry water.
• The absorber absorbs the solar radiation and transfers the heat to the flowing water.
ojection by centre for application of renewable energy

11. a solar water heater projection by centre for application of renewable ene
• Evacuated Tube Collector is made of
double layer borosilicate glass tubes
evacuated for providing insulation.
• The outer wall of the inner tube is coated
ergy
with selective absorbing material.

12. a solar
Purpose‐ To transport fluid to the lower header of the collector (cold water) to the top
of the storage tank (hot water).
Material‐ Galvanized Iron sheet.
water heater pro
Properties‐>This material is tough and strong,
> It can be fairly easily worked (bent or formed),
> It lasts a long time, too, because the zinc coating (the galvanizing)
inhibits corrosion quite well.
ojection by centr
q
PROPERTIES OF GLASS WOOL
USED as insulation material for pipe connection
• Density : 10‐100 kg/m³
• Average fiber dia. : 5.5 μm
re for application
g 5 5 μ
• Water content : ≤ 1%
• Shrinking temperature: ≥ 250 °C
• Thermal conductivity: 0.038–0.06 w/mºK
• Non combustible in nature
n of renewable ene
ergy

13. a solar
FIBERGLASS VINYL
water heater pro
• Lightweight;
• Tight Structure ;
ƒ Resistance To Corrosive Attacks;
•Vinyl is resistant to moisture
and humidity;
•It is a very strong and durable
ojection by centr
;
• Superior ShockAndWear Resistance;
• CheapMaintenance In Service;
• Damage And Breakage Resistance;
l
plastic material
•Vinyl can be manufactured in
variety of colors, both
re for application
• At Temperatures Below Zero It Doesn’t
Become Slippery Or Covered With Ice;
• Hardly Bendable Material;
LowThermal Conductivity
transparent and solid;
•It is low cost material
•It can easily be recycled.
n of renewable ene
• .
ergy

14. a solar
• On cloudy days also, if it is for a day or
two, you still get warm water as water
t h t d d t diff d di ti
water heater pro
gets heated due to diffused radiation
available in the atmosphere.
• The system, however, is either
connected to an electric geyser in the
ojection by centr
g y
house or an electrical back‐up is
provided in the storage tank of the
system which is switched on when
ater is not s fficientl re for application
water sufficiently hot
• So, you get hot water all the time even
on rainy days.
ƒ An auxiliary heater is attached in the
n of renewable ene
y
tank to provide supplement heat
during cloudy days.
ƒ Freezing protection during winter
season
ergy
season.
ƒ Act as heat exchanger.

15. Collector Area
a solar
Where, Q= Heat storage in water ( watt)
Average solar insolation: 5000 kcal/m² day
Collector efficiency: 30 %
Hot water demand per day: 100 litres
Tape water temperature: 15 °C
water heater pro
, g )
m= mass flow (kg/second)
c = Specific heat of water(1 kcal/kg °C or
4.187 KJ/kg ° k)
T1= Hot water temperature (°C)
ape ate te pe atu e 5 Hot water temperature: 55 °C
ojection by centr
( )
T2= Cold water temperature (°C)
ACTUAL AVG.INSOLATION AVAILABLE = SOLAR AVG. INSOLATION* COLLECTOR EFFICIENCY
Specific of water = 1 kg°c
re for application
heat kcal/kg = 1500 kcal/m² day= 5000×30/100
Q= 100×1×(55‐15)
40 10² k l
n of renewable ene
= 40×10kcal
ergy

16. a solar
Purpose: A hot water storage
tank (also hot water tank, thermal
t t k h t t th l
water heater pro
storage tank, hot water thermal
storage unit, heat storage tank) is a
water tank that is used for storing
hot water for space heating or
ojection by centr
p g
domestic use
Material: Mild steel or
Steel(Density:7850 kg/m³,
cond cti it 6 /m ºc)
re for application
Thermal conductivity: 47.6 w/Insulation:The most common type of
water heater blanket is fiberglass
insulation with a vinyl film on the
n of renewable ene
y
outside.
ergy

17. a solar water heater projection by centr
MATERIAL PROPERTIES
Epoxy, air dry Cost-effective, corrosion resistant coating
re for application
Epoxy, thermal cure Excellent impact resistance, plus corrosion and
abrasion resistance
Inorganic zinc Corrosion and weathering protection for steel
n of renewable ene
Molybdenum disulfide Friction protection for high pressure loads
ergy

18. a solar
• Best suited for colder climates, an indirect system pumps heat‐transfer fluids ( usually a non‐
water heater pro
, y p p y
toxic propylene glycol‐water antifreeze mixture) through collectors, and then transfers the
heated fluid from the collectors to a storage tank. Heat exchangers transfer the heat from the
fluid to the household water stored in the tanks. Water stored within the tank is then heated
h th fl id th h h t h l tdi id th t t k A tif
ojection by centr
when the fluid passes through a heat exchanger located inside the storage tank. Antifreeze
fluid is used to prevent collector piping from freezing and allow for the maximum transfer of
heat from the solar collector to the storage tank. Many indirect system designs also
incorporate an external heat exchanger
re for application
p g
• in warmer climates, direct systems are more commonly used. The direct system circulates
potable water directly through the solar collector into the storage tank. In other words, the
water that is used in the house is the same water that has circulated through the solar
ll t Th t i t i t t i t t l th ti f th
n of renewable ene
collector. These systems incorporate various strategies to control the operation of the
circulating pump, which can include photovoltaic or differential controllers.
• Passive direct systems are also used in warmer climates. The unique characteristic of these
systems is that they do not use pumps or other electrical components, thereby providing a
ergy
y y p p p , yp g
simple and reliable system. The most common passive systems are the thermosiphon (see
diagram below) and integral collector storage systems. Indirect thermosiphon systems could
also be used in colder climates.

19. a solar water heater projection by centre for application of renewable energy

20. a solar water heater projection by centre for application of renewable ene
A thermosiphon solar water heater requires neither pump nor controller. Cold water from
the city water line flows directly to the tank on the roof. Solar heated water flows from the
f k h l k ll d dl l h d h
ergy
rooftop tank to the auxiliary tank installed at ground level whenever water is used within
the residence.

21. a solar water heater projection by centre for application of renewable ene
Purpose: To protect the system from damage and for efficient working.
•Sensor ( In case of forced circulation system)
• Control valve
ergy
•Maintain the height between top of the collector to the bottom of the storage tank
0.3 ‐0.4 m to avoid reverse flow during night( in case of natural convection system).

22. a solar
• Simple to construct and install.
water heater pro
p
• No or negligible running cost.
• Almost maintenance free.
• Cost is low and economically competitive with electric water heating system.
It ti d hi h d f f l t i
ojection by centr
• saves time and high grade form of electric energy.
• Required low temperature up to 100o C can be achieved by simple flat plate
collector.
Disadvantages
re for application
g
Freezing problem
• No big problems related to this.
n of renewable energy

23. a solar
Environmental benefits
A SWH of 100 litres capacity can prevent emission of 1.5 tonnes of carbon dioxide per
year a Life : 15‐20 years
water heater pro
.15 Approximate cost :
Rs.15000‐ 20,000 for a 100 litres capacity system and Rs.110‐150 per installed litre for
higher capacity systems
ojection by centr
g p y y
Payback period :
when electricity is replaced 3‐4 years
when furnace oil is replaced 4‐5 years
when coal is replaced 5 6 years
re for application
5‐Fuel Savings :
A 100 litres capacity SWH can replace an electric geyser for residential use and saves
1500 units of electricity annually.
n of renewable ene
Avoided uitility cost on generation
The use of 100 SWHs of 100 litres capacity each can contribute to a peak load saving of
100 KW.
ergy

24. a solar
• A 100 lpd system (2 sq m of collector area) installed in a home can save 4‐6 units of
water heater pro
sq.electricity/day depending on the place of installation & hot water use. On an
average it could be taken as 5 units/day. Maximum average saving with 300 clear
days, therefore, could be taken as 1500 units/year.
ojection by centr
• Assuming 300 days of solar hot water use in Bangalore and 150 days in Delhi, the
savings could be 1500 & 750 units per year respectively i.e. replacement of a 2 KW
electric geyser working for 2 ½ hours in a day. Considering all parts of the country
andmaximum installations in areas where hot water requirement is more during the
year average saving could be taken as 1200 units/year/100 lpd system
re for application
year, system.
• 1 million such systems installed will be able to save 1200 million units of
electricity/year A 100 lpd system (2 sq.m of collector area) installed in an industry
can save around 140 litres of in a year.
n of renewable ene
diesel ergy

25. a solar water heater pro
• 1 system of 100 lpd can replace an electric geyser of 2 KW capacity in a home. 1 million
such systems will replace 1 million geysers of 2 KW capacity each in homes.
Assuming that at least 50%of geysers are switched on at a time this will have a
ojection by centr
time, peak load shaving of 1000MW.
CO2 Reduction
• A 100 lpd system on an average saves up to 1500 units of electricity/yr. To generate that
much of electricity from a coal based power plant 1 5 tone of CO2 /year is released in
re for application
plant, 1.5 atmosphere. One million solar water heating systems installed in homes will , therefore,
also result in reduction of 1.5 million tone of CO2 emission in atmosphere.
n of renewable energy

26. a solar water heater proojection by centre for application of renewable energy