J.M. Smith, Hendrick Van Ness, Michael Abbott, Mark Swihart - Introduction to...
Heating & Cooling of Building
1. Power Plant Engineering
Electrical Engineeering
University of Engineering and technology,
Lahore
Mudasser rahim
2013-EE-36
January 15th, 2017
2. Power Plant Engineering
.
Acknowledgement
I am grateful to the well known Dr. prof. Imran Shiekh whose guidence helped
me a lot in making of this report. I have learned different steps and techniques
with the help of slides he provided to me. These things helped me in making my
assignment succesful. May Allah always bless him for the support he always
provide us during the study of the course.
Page 1
3. Abstract
Everyday electricity plays a key role in keeping our homes and businesses to run
smoothly. It allows people to do work at school and other places, and supplies
energy to appliances in all sectors but as our non-renewable sources are declining,
the price of electricity is increasing. As our non-renewable resources are set to de-
cline further in the years to come, it is important for us to move towards renewable
sources of energy like wind, hydro power, biomass and tidal. In this report our
main purpose is to move from non-renewable source of energy to renewable like
solar energy. Solar energy i.e. energy from the sun provide consistent and steady
source of solar power throughout the year. The main benefit of solar energy is
that it can be easily deployed by both home and business users as it does not
require any huge set up like in case of wind or geothermal power. Solar energy
not only benefits individual owners, but also benefit environment as well. So we
are converting our load to solar energy.
7. Chapter 1
Background
1.1 Introduction
The house is located in Gulshan Iqbal, Rahim Yar khan. It is located in southern
Punjab. The city geographical coordinates are 28 25’ 0” North, 70 18’ 0” East.
It is a double story building having 6 bed rooms 2 kitchen and 5 washrooms. Its
total area is 3321.51ft2
. Three people are living in the house.
1.2 Total Load Calculation
The Electrical base load of the house is 17.87kW, which include the following
equipments.
Equipment Load Yearly hours
1. Air conditioner 2x2500W = 5000W. 1080 hrs
2. Electric heater 1x2000W = 2000W. 100 hrs
3. Energy Savers 50x25W = 1250W. 1500 hrs
4. Smart Tv 1x75W = 75 W. 1800 hrs
5. Ceiling fans 15x75W = 1125W. 1600 hrs
6. Desktop Computer 1x200W = 200W. 500 hrs
7. Electric Kettle 1x1200W = 1200W. 50 hrs
8. Fridge 2x200W = 400W. 8000 hrs
9. Electric Iron 1x1000W =1000W. 300 hrs
10. Microwave 1x2000W =2000W. 150 hrs
11. Table Fan 1x100W =100W. 100 hrs
12. Toaster 1x1000W =1000W. 20 hrs
13. Washing Machine 1x500W =500W. 100 hrs
14. Water pump 1x2000W =2000W. 1000 hrs
15. Charging devices 4x5W = 20W. 5000 hrs
16. Exhaust Fans 2x200W=400W. 6000hrs
17. Printer 1x100W=100W. 1000hrs
18. Laptop Computer 2x50W=100W. 6000hrs
19. Exhaust Hood 1x150W=150W. 4000hrs
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8. Power Plant Engineering
Total Base Load= 18.62kW
According to formula for energy calculation
Energy= (Power in kW) x (number of hours)
Total consumption will be 6,500kWh/year
1.3 Map of Building
The house is 3321 sq. feet and having double story, its map of both stories are
shown here:
Figure 1.1: House Map
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9. Chapter 2
Heating and Cooling of Building
2.1 Introduction
Heating and cooling of building is needed to provide thermal comfort and accept-
able indoor air quality for the residents. Heating can be accomplished by heating
the air with in the space or heating the occupants directly by radiation. Cooling
is of two types sensible and latent cooling. Sensible cooling involves the control
of air temprature while latent cooling involves the control of air humidity.
2.2 Average Outdoor Temprature
We don’t know what will be the weather in future. Therefore, we turn to the past
instead of the future and bet that the past weather data averaged over several
years will be representative of a typical year in the future.
Figure 2.1: Average Temprature per month
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10. Power Plant Engineering
The average temprature during differnt month of the year in tebular form is
given as follows:
Figure 2.2: Tebular form of Average Temprature
The temperature normals are measured in the period 1985 to 2015.
Source:WMO (World Meteorological Organization)
For ordinary building we are designing that the economics and comfort meet at
the 97.5 percent level in winter. That is, the heating system will provide thermal
comfort 97.5 percent of the time but may fail to do so during 2.5 percent of the
time. For example the 97.5 percent winter design temperature for Rahim Yar
khan is 6o
C, and thus the temperatures in Rahim Yar Khan may fall below 6o
C
about 2.5 percent of the time during winter months in a typical year.
The winter percentages are based on the weather data for the months of
December, January, and February. The three winter months have a total of
31+31+28=90 days and thus 2160 hours. Therefore, the conditions of a house
whose heating system is based on the 97.5 percent level may fall below the com-
fort level for 2160x2.5%=54 hours during the heating season of a typical year.
Most people will not even notice it because everything in the house will start
giving off heat as soon as the temperature drops below the thermostat setting.
The minimum temperatures usually occur between 6:00 AM and 8:00 AM so-
lar time.While the Summer percentages are based on the four months June
through September The maximum temperatures usually occur between 2:00 PM
and 4:00 PM solar time.
2.3 Design Conditions for Heating and Cooling
of Building
The size of a heating or cooling system for a building is determined on the basis
of the desired indoor conditions that must be maintained based on the outdoor
conditions that exist at that location. The desirable ranges of temperatures, hu-
midity, and ventilation rates (the thermal comfort zone) constitute the typical
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11. Power Plant Engineering
indoor design conditions, and they remain fairly constant. For example, the rec-
ommended indoor temperature for general comfort heating is 22o
. The outdoor
conditions at a location, on the other hand, vary greatly from year to year, month
to month, and even hour to hour. The set of extreme outdoor conditions under
which a heating or cooling system must be able to maintain a building at the
indoor design conditions is called the outdoor design conditions.
When designing a heating, ventilating, and air-conditioning (HVAC) system,
perhaps the first thought that comes to my mind is to select a system that is
large enough to keep the indoors at the desired conditions at all times even under
the worst weather conditions. But sizing an HVAC system on the basis of the
most extreme weather on record is not practical since such an oversized system
will have a higher initial cost, will occupy more space, and will probably have a
higher operating cost because the equipment in this case will run at partial load
most of time and thus at a lower efficiency. We would not mind experiencing
an occasional slight discomfort under extreme weather conditions if it means a
significant reduction in the initial and operating costs of the heating or cooling
system. But I will try to make a good compromise between economics and comfort.
2.3.1 Heating or Cooling load
The heating or cooling loads of a building represent the heat that must be
supplied to or removed from the interior of a building to maintain it at the desired
conditions. A distinction should be made between the design load and the actual
load of heating or cooling systems. The design (or peak) heating load is usually
determined with a steady-state analysis using the design conditions for the indoors
and the outdoors for the purpose of sizing the heating system . This ensures that
the system has the required capacity to perform adequately at the anticipated
worst conditions. But the energy use of building during a heating or cooling
season is determined on the basis of the actual heating or cooling load, which
varies throughout the day.
The internal heat load (the heat dissipated off by people, lights, and appli-
ances in a building) is usually not considered in the determination of the design
heating load but is considered in the determination of the design cooling load.
This is to ensure that the heating system selected can heat the building even
when there is no contribution from people or appliances, and the cooling system
is capable of cooling it even when the heat given off by people and appliances is
at its highest level.
2.3.2 Wind Speed
Wind increases heat transfer to or from the walls, roof, and windows of a building
by increasing the convection heat transfer coefficient and also increasing the infil-
tration. Therefore, wind speed is another consideration when determining the
heating and cooling loads. The average values of wind speed to be considered are
6 km/h for winter and 18 km/h for summer.
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12. Power Plant Engineering
The corresponding design values recommended by ASHRAE for heat trans-
fer coefficients for combined convection and radiation on the outer surface of a
building are
ho,Winter = 34.0W/m2
.C
ho,Summer = 22.7W/m2
.C
The recommended heat transfer coefficient value for the interior surfaces of a
building for both summer and winter is
hi = 8.0W/m2
.C
For well-insulated buildings, the surface heat transfer coefficients constitute a
small part of the overall heat transfer coefficients, and thus the effect of possible
deviations from the above values is usually insignificant.
2.3.3 Moisture Level
In summer, the moisture level of the outdoor air is much higher than that of
indoor air. Therefore, the excess moisture that enters a house from the outside
with infiltrating air needs to be condensed and removed by the cooling system.
But this requires the removal of the latent heat from the moisture, and the cooling
system must be large enough to handle this excess cooling load. To size the cooling
system properly, we need to know the moisture level of the outdoor air at design
conditions. This is usually done by specifying the wet-bulb temperature, which
is a good indicator of the amount of moisture in the air. When the wet-bulb and
ambient temperatures are available, the relative humidity and the humidity ratio
of air can be determined from the psychrometric chart. The moisture level of
the cold outside air is very low in winter, and thus normally it does not affect the
heating load of a building.
PSYCHROMETRIC CHART
A psychrometric chart is a graphical representation of the psychrometric pro-
cesses of air. Psychrometric processes include physical and thermodynamic prop-
erties such as dry bulb temperature, wet bulb temperature, humidity, enthalpy,
and air density. Every psychrometric chart includes vertical lines that represent
the dry bulb temperatures. Air temperature increases from left to right.
Figure 2.3: Dry bulb temperature lines on a psychrometric chart
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13. Power Plant Engineering
Every psychrometric chart also includes wet bulb temperatures. These lines
are indicated at diagonals, and like dry bulb temperatures they increase from left
to right.
Figure 2.4: Wet bulb temperature lines on a psychrometric chart
The comfort zone is typically indicated by shading a portion of the psychro-
metric chart. This shaded area is highly variable per climate and project. The
comfort zone is either populated by a software system, or manually by a designer,
based upon the activity to take place in the building and the level of anticipated
clothing to be worn by the occupants.
Figure 2.5: Comfort zone in a psychrometric chart
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14. Power Plant Engineering
2.3.4 Solar Radiation
Solar radiation plays a major role on the heating and cooling of buildings, and
we may think that it should be an important consideration in the evaluation of the
design heating and cooling loads. Well, it turns out that peak heating loads usually
occur early in the mornings just before sunrise. Therefore, solar radiation does
not affect the peak or design heating load and thus the size of a heating system.
However, it has a major effect on the actual heating load, and solar radiation can
reduce the annual heating energy consumption of a building considerably.
2.4 SOLAR AIR TEMPRATURE
The sun is the main heat source of the earth, and without the sun, the environ-
ment temperature would not be much higher than the deep space temperature
of −270o
C. The solar energy stored in the atmospheric air, the ground, and the
structures such as buildings during the day is slowly released at night, and thus
the variation of the outdoor temperature is governed by the incident solar radia-
tion and the thermal inertia of the earth. Heat gain from the sun is the primary
reason for installing cooling systems, and thus solar radiation has a major effect
on the peak or design cooling load of a building, which usually occurs early in the
afternoon as a result of the solar radiation entering through the glazing directly
and the radiation absorbed by the walls and the roof that is released later in the
day.
For opaque surfaces such as the walls and the roof, on the other hand, the
effect of solar radiation is conveniently accounted for by considering the outside
temperature to be higher by an amount equivalent to the effect of solar radiation.
This is done by replacing the ambient temperature in the heat transfer relation
through the walls and the roof by the sol-air temperature, which is defined as the
equivalent outdoor air temperature that gives the same rate of heat transfer to a
surface as would the combination of incident solar radiation, convection with the
ambient air, and radiation exchange with the sky and the surrounding surfaces.
Heat flow into an exterior surface of a building subjected to solar radiation can
be expressed as
Qsurface = hoAs(Tsol−air − Tsurface)
2.4.1 Effect of Solar Heated Walls on Design Heat Load
The west wall of a house which is the only wall which faces the sun is made of
100-mm thick brick its heat transfer coefficient is 1.65 W/m2
. The exposed surface
area of the wall is 19.5 m2
.
Its cooling system is to be sized on the basis of the heat gain at 15:00 hour (3 PM)
solar time on July 21, the design ambient air temperature at that time at that
location will be 32o
C, and the interior of the house is to be maintained at 24o
C.
According to our calculations temprature on July 21 will be 50o
C heat gain
through that wall will be
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15. Power Plant Engineering
Qsurface=(1.65)x(19.5)x(50-24)
=836.55W
The fraction of heat gain will be
Solar Fraction = TT otal
Tsolar
= 16
26
= 0.69
Two third of the heat gain is due to this wall.
The outer layer of the wall is made of red brick, which is dark colored.The value
of α is 0.90 for dark and ho is 17 W/m2
.o
C . Therefore, the value of α
ho
=
0.052m2
.o
C/W.
Solar Fraction Transferred = (1.65)(0.052)=0.086
So, less than 10% of energy will be transferred to house from this red brick
wall.
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16. Chapter 3
Heat Gain from People, Lights
and Equipments
The conversion of chemical or electrical energy to thermal energy in a building
constitutes the internal heat gain or internal load of a building. The primary
sources of internal heat gain are people, lights, appliances, and miscellaneous
equipment such as computers, printers, and copiers. Internal heat gain is usually
ignored in design heating load calculations to ensure that the heating system
can do the job even when there is no heat gain, but it is always considered in
design cooling load calculations since the internal heat gain usually constitutes a
significant fraction of it.
3.1 PEOPLE
The average amount of heat given off by a person depends on the level of activity,
and can range from about 100 W for a resting person to more than 500 W for
a physically very active person. Typical rates of heat dissipation by people are
given in fig.6 for various activities in various application areas. Note that latent
heat constitutes about one-third of the total heat dissipated during resting, but
rises to almost two-thirds the level during heavy physical work. Also, about 30
percent of the sensible heat is lost by convection and the remaining 70 percent
by radiation. The latent and convective sensible heat losses represent the instant
cooling load for people since they need to be removed immediately. The radiative
sensible heat, on the other hand, is first absorbed by the surrounding surfaces and
then released gradually with some delay. It is interesting to note that an average
person dissipates latent heat at a minimum rate of 30 W while resting. Noting
that the enthalpy of vaporization of water at 33o
C is 2424 kJ/kg, the amount of
water an average person loses a day by evaporation at the skin and the lungs is
Daily Water loss = Latentheatlossperday
heatofvaporization
= (0.030kJ/s)(24x3600s/day)
2424kJ/kg
= 1.07kg/day
which justifies the sound advice that a person must drink at least 1 L of water
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17. Power Plant Engineering
every day. Therefore, a family of three will supply 3 L of water a day to the air in
the house while just resting. This amount will be much higher during heavy work.
Figure 3.1: Heat Gain from People in Conditional Space
Heat given off by people usually constitutes a significant fraction of the sensible
and latent heat gain of a building, and may dominate the cooling load in high
occupancy buildings such as theaters and concert halls. The rate of heat gain
from people given in fig 2.6 is quite accurate, but there is considerable uncertainty
in the internal load due to people because of the difficulty in predicting the number
of occupants in a building at any given time. The design cooling load of a building
should be determined assuming full occupancy.
3.2 LIGHTS
Lighting constitutes about 7 percent of the total energy use in residential build-
ings. Therefore, lighting can have a significant impact on the heating and cooling
loads of a building. Not counting the candle light used for emergencies and ro-
mantic settings, and the kerosene lamps used during camping, all modern lighting
equipment is powered by electricity. The basic types of electric lighting devices
are incandescent, fluorescent, and gaseous discharge lamps.
The amount of heat given off per lux of lighting varies greatly with the type
of lighting, and thus we need to know the type of lighting installed in order to
predict the lighting internal heat load accurately. Incandescent lights are the least
efficient lighting sources, and thus they will impose the greatest load on cooling
systems. So it is no surprise that practically all office buildings use high-efficiency
fluorescent lights despite their higher initial cost. Note that incandescent lights
waste energy by (1) consuming more electricity for the same amount of lighting
and (2) making the cooling system work harder and longer to remove the heat
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18. Power Plant Engineering
given off. Office spaces are usually well lit, and the lighting energy consumption
in office buildings is about 20 to 30 W/m2
of floor space.
The energy consumed by the lights is dissipated by convection and radiation.
The convection component of the heat constitutes about 40 percent for fluorescent
lamps, and it represents the instantaneous part of the cooling load due to lighting.
The remaining part is in the form of radiation that is absorbed and reradiated by
the walls, floors, ceiling, and the furniture, and thus they affect the cooling load
with time delay. Therefore, lighting may continue contributing to the cooling load
by reradiation even after the lights have been turned off. Sometimes it may be
necessary to consider time lag effects when determining the design cooling load.
The ratio of the lighting wattage in use to the total wattage installed is called
the usage factor, and it must be considered when determining the heat gain due
to lighting at a given time since installed lighting does not give off heat unless it
is on.
3.3 EQUIPMENTS and APPLIANCES
Most equipment and appliances are driven by electric motors, and thus the heat
given off by an appliance in steady operation is simply the power consumed by
its motor. The power rating Wmotor on the label of a motor represents the power
that the motor will supply under full load conditions. But a motor usually oper-
ates at part load, sometimes at as low as 30 to 40 percent, and thus it consumes
and delivers much less power than the label indicates. This is characterized by
the load factor fload of the motor during operation, which is fload = 1.0 for full
load.Also, there is an inefficiency associated with the conversion of electrical energy
to rotational mechanical energy. This is characterized by the motor efficiency
ηmotor which decreases with decreasing load factor. Another factor that affects
the amount of heat generated by a motor is how long a motor actually operates.
This is characterized by the usage factor fusage with fusage=1.0 for continuous
operation. Motors with very low usage factors are usually ignored in calculations.
Then the heat gain due to a motor inside a conditioned space can be expressed as
Qmotor = Wmotor.fload. fusage
ηmotor
Heat generated in conditioned spaces by electric, gas, and steam appliances
such as a range, refrigerator, freezer, TV, dishwasher, washing machine, drier,
computers, printers are significant, and thus they are being considered when de-
termining the peak cooling load of a building. The exhaust hoods in the kitchen
complicate things further. Also, some equipment such as printers, laptops and
desktop computers consume considerable power in the standby mode. A 350-
W laser printer, for example, may consume 175 W and a 600-W computer may
consume 530 W when in standby mode.
A more realistic approach is to take 50 percent of the total nameplate ratings
of the appliances to represent the maximum use. Therefore, the peak heat gain
from appliances is taken to be
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19. Power Plant Engineering
Qunhooded−appliances = 0.5.Qappliance,input
regardless of the type of energy or fuel used. For cooling load estimate, about
34 percent of heat gain can be assumed to be latent heat, with the remaining 66
percent to be sensible. In hooded appliances, the air heated by convection and the
moisture generated are removed by the hood. Therefore, the only heat gain from
hooded appliances is radiation, which constitutes up to 32 percent of the energy
consumed by the appliance. Therefore, the design value of heat gain from hooded
electric or steam appliances is simply half of this 32 percent.
3.3.1 USEFUL ENERGY CONSUMPTION
The efficiency of different equipments affects the internal heat gain from them
since an inefficient appliance consumes a greater amount of energy for the same
task, and the excess energy consumed shows up as heat in the living space. The
efficiency of different devices are written
Equipment Efficiency Efficient Load
1. Air conditioner 0.5 0.5x5kW = 2.5kW
2. Electric heater 0.2 0.2x2kW = 0.4kW
3. Energy Savers 0.9 0.9x1.25kW = 1.125kW
4. Smart Tv 0.9 0.9x0.075kW = 0.0675kW
5. Ceiling fans 0.8 0.8x1.125kW = 0.9kW
6. Desktop Computer 0.5 0.5x0.2kW = 0.1kW
7. Electric Kettle 0.4 0.4x1.2kW = 0.48kW
8. Fridge 0.7 0.7x0.2kW = 0.14kW
9. Electric Iron 0.5 0.5x1kW = 0.5kW
10. Microwave 0.5 0.5x2kW = 1kW
11. Table Fan 0.7 0.7x0.1kW = 0.07kW
12. Toaster 0.5 0.5x1kW = 0.5kW
13. Washing Machine 0.8 0.8x0.5kW = 0.4kW
14. Water pump 0.6 0.6x2kW = 1.2kW
15. Charging devices 0.8 0.8x0.02kW = 0.016kW
16. Exhaust Fans 0.8 0.8x0.1kW = 0.08kW
17. Printer 0.6 0.6x0.1kW = 0.06kW
18. Laptop Computer 0.8 0.8x0.1kW = 0.08kW
19. Exhaust Hood 0.7 0.7x0.15kW = 0.105kW
Out of the total base load which was equal to
18.63 kW useful energy is 9.72 kW.
The remaining energy is wasted as a heat during the running of these appliances
and it should be kept in mind while designing our cooling system.
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20. Chapter 4
Heat Loss due to Appliances
4.1 FANS
Three fans which are used frequently during the year have fload = 0.6,
fusage = 1.0, ηfans = 0.8 and the heat gains due to these fans are
Q=3 x 75 x 0.6 x 1
0.8
= 168.75 W
Remaining twelve fans emits heat equal to
Q=12 x 75 x 0.1 x 1
0.8
= 112.5 W
The heat gain due to cieling fans per year is equal to
Qtotal= 168.75+112.5=281.25 W
4.2 Air Conditioner
Air conditioners which are used frequently during summer season fload = 0.11,
fusage = 1.0, ηAC = 0.5. The heat gain due to air conditioners per year is equal to
Qtotal= 2 x 2500 x 0.11 x 1
0.5
=1100 W
4.3 Electric Heater
Electric Heater which is used frequently during winter season fload = 0.01,
fusage = 1.0, ηheater = 0.2 and the heat gain due to electric heater per year is equal
to
Qtotal= 2000 x 0.01 x 1
0.2
=100 W
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21. Power Plant Engineering
4.4 Energy Savers
Ten Energy savers which are used frequently during the year have fload = 0.2,
fusage = 1.0, ηsavers = 0.9 and the heat gains due to these energy savers are
Q= 10x25 x 0.2 x 1
0.9
=55.5 W
Forty Energy savers which are used rarely during the year have fload = 0.05,
fusage = 1.0, ηsavers = 0.9 and the heat gains due to these energy savers are
Q= 40x25 x 0.05 x 1
0.9
=55.5 W
The heat gain due to energy savers per year is equal to
Qtotal= 55.5 + 55.5=111 W
4.5 Smart TV
Smart Tv which is used frquently during the year has fload = 0.42,
fusage = 1.0, ηTV = 0.9 and the heat gains due to this smart TV is
Qtotal= 75 x 0.42 x 1
0.8
=39.37 W
4.6 Desktop computer
Desktop computer which is used rarely during the year has fload = 0.05,
fusage = 1.0, ηcomputer = 0.5 and the heat gains due to this desktop computer is
Qtotal= 200 x 0.05 x 1
0.5
=20 W
4.7 Electric Kettle
Electric Kettle which is used very rarely during the year has fload = 0.005,
fusage = 1.0, ηkettle = 0.4 and the heat gains due to this electric kettle is
Qtotal= 1200 x 0.005 x 1
0.4
=15 W
4.8 FRIDGE
Fridges which are used very frequently during the year has fload = 0.91,
fusage = 1.0, ηfridge = 0.7 and the heat gains due to these fridges is
Qtotal= 2 x 200 x 0.91 x 1
0.7
=580 W
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22. Power Plant Engineering
4.9 Electric Iron
Electric Iron which is used rarely during the year has fload = 0.03,
fusage = 1.0, ηiron = 0.5 and the heat gains due to this iron is
Qtotal= 1000 x 0.03 x 1
0.5
=60 W
4.10 Microwave
Microwave which is used rarely during the year has fload = 0.017,
fusage = 1.0, ηmicrowave = 0.5 and the heat gains due to this microwave is
Qtotal= 2000 x 0.017 x 1
0.5
=68 W
4.11 Table Fan
Table fan which is used rarely during the year has fload = 0.011,
fusage = 1.0, ηfan = 0.7 and the heat gains due to this table fan is
Qtotal= 100 x 0.011 x 1
0.7
=1.57 W
4.12 Toaster
Toaster which is used very rarely during the year has fload = 0.002,
fusage = 1.0, ηtoaster = 0.5 and the heat gains due to this toaster is
Qtotal= 1000 x 0.002 x 1
0.5
=4 W
4.13 Exhaust Fans
Exhaust Fans which are used very frequently during the year has fload = 0.68,
fusage = 1.0, ηExhaust = 0.8 and the heat gains due to these exhaust Fan is
Qtotal= 2 x 200 x 0.68 x 1
0.8
=340 W
4.14 Washing Machine
Washing Machine which is used very rarely during the year has fload = 0.011,
fusage = 1.0, ηMachine = 0.8 and the heat gain due to this Washing Machine is
Qtotal= 500 x 0.011 x 1
0.8
=6.875 W
4.15 Water Pump
Water pump which is used frequently during the year has fload = 0.5,
fusage = 1.0, ηPump = 0.6 and the heat gain due to this Water Pump is
Qtotal= 2000 x 0.5 x 1
0.6
=1666.67 W
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23. Power Plant Engineering
4.16 Charging Devices
Charging Devices which are used frequently during the year has fload = 0.68,
fusage = 1.0, ηdevices = 0.8 and the heat gain due to these Charging Devices is
Qtotal= 5x4 x 0.68 x 1
0.8
=17 W
4.17 Printer
Printer which is used rarely during the year has fload = 0.114,
fusage = 1.0, ηprinter = 0.6 and the heat gain due to this Printer is
Qtotal= 100 x 0.114 x 1
0.6
=19 W
4.18 Laptop Computers
Laptops which are used frequently during the year has fload = 0.685,
fusage = 1.0, ηLaptop = 0.8 and the heat gain due to these Laptops is
Qtotal= 2 x 50 x 0.685 x 1
0.8
=85.625 W
4.19 Exhaust Hood
Exhaust hood which is used frequently during the year has fload = 0.45,
fusage = 1.0, ηhood = 0.7 and the heat gain due to this exhaust hood is
Qtotal= 150 x 0.45 x 1
0.7
=96.42 W
TOTAL HEAT LOSS
The total heat loss during year and for a single month is as follows:
Heat loss for a year Q(KWh) = 1500
Heat loss for a month Q(KWh) = 125
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24. Chapter 5
Solar Power Generation
5.1 Introduction
When we capture solar energy it can be either used as heat or electrical energy.
for this two systems are used.
5.1.1 Thermal Systems
In this system sunlight is captured by falling it on the solar collector and this
is used in heating of water or for space heating, but the heat can also used to
generate electricity by focusing the heat on the heat absorber in which working
fluid is present which is used to raise steam which in turn drives a generator and
turbine in a separate circuit.
5.1.2 Photovoltaic Systems
In Photovoltaic Systems radiant energy of sunlight is used and converted to elec-
trical energy by focusing sunlight on the photovoltaic cells.
The amount of energy produced is directly proportional to the area of the
collector which is facing the sun.
5.2 Solar Collectors
It is the heat collecting surface on which sunlight falls and this radiant energy of
sun is used to heat up the thermal working fluid.
5.2.1 Concentrators
In concentrators all the sun light is focused on the small receiver so that we can
attain higher temperature easily and early for the working fluid.
The unit of solar concenterator is suns. It have different types which are explained
below.
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25. Power Plant Engineering
• Parabolic Trough.
It consists of rows of parabolic-shaped mirrors that reflect and concentrate
sunlight onto linear receivers located along the foci of the parabolas. The receivers,
or heat collection elements , consist of a stainless steel absorber tube surrounded
by a glass envelope with the vacuum drawn between the two to reduce heat losses.
A heat transfer fluid circulates through the receivers, delivering the collected solar
energy to a somewhat conventional steam turbine/generator to produce electricity.
Figure 5.1: Parabolic trough
• Power Tower.
In this large number of plates are present and all the sunlight which falls on
these plates is concenterated on the tower on which solar furnance is present and
this solar furnance is used to make steam to run steam turbine in return.In this
solar plates are fixed on their axis.
Figure 5.2: Power Tower
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26. Power Plant Engineering
• Heliostat.
It is similar to power tower but in this all the plates which focus all the sunlight
on the tower are basically sun tracking mirrors which moves with the direction of
sun and falls all the sunlight to the tower in return.
Figure 5.3: Heliostat
• Parabolic Dish.
In it heat absorber is present at the focus of the parabolic shaped dish. When
sunlight falls, all the light is used to rise the temperature which is proportional
to the area of the dish such that by increasing the area of the dish we can get
more temperature on the absorber of the parabolic dish. It is used for the systems
between 20kW to 40kW.
Figure 5.4: parabolic dish
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27. Chapter 6
Production of Electricity through
Sunlight
6.1 Introduction
During night when there will be no sun and hence no power will be provided by
the solar system so there must be a system that generate amount of energy so that
it can fulfill the day time requirement and has ability to store enough energy for
nights or if there is no sunlight available due to bad weather. We will use batteries
to provide electrical energy during night and during bad weather when there is no
sunlight, but it is not possible for us to store large amount of energy.
6.2 Thermal Power
Electricity in a solar thermal plant is produced in two steps.
• Heat energy from the sun is captured and is used to heat the working fluid.
• This working fluid is used to generate electrical energy.
Thermal power plant have set of mirrors on which sunlight is focused and is used
to heat the absorber which run the turbine for electricity production. On large
scale, the heat engine is usually a turbine driven by steam or some other working
fluid. In small scale systems the heat engine may be a Stirling engine.
6.2.1 Large Scale production
In large scale production solar plates are present which capture sunlight and focus
all of it on the single concentrator which transfers heat to heat exchanger. This
heat exchanger further transfer heat to run steam turbine and steam turbine along
with steam generator gives electrical energy which is used further for other pur-
poses .Each module requires large area of land and need very accurate engineering
and control. The type of system used in large scale is shown below.
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28. Power Plant Engineering
Figure 6.1: Large scale production
6.2.2 Small Scale production
There are more than one technique in Small scale production.
• Photovoltaic Systems
The simplest technique used in domestic purpose is the solar panels which cap-
ture the sunlight and then it is converted into DC after passing through regulator
transfers to DC control unit. This control unit is attached with battery bank and
with the inverter. DC control unit gives its DC supply to inverter which converts
it to AC. After the conversion it is used to lighten our houses.
Figure 6.2: Photovoltaic System
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29. Power Plant Engineering
• Voltaic System
In this solar power is directly converted into electricity. The light falls on the
solar panel this light is converted into electricity for direct usage but this only
happens when sunlight is present. This system will not work when there is no
sunlight. This system is used in watches, calculators and mobile chargers.
Figure 6.3: Voltaic System
• Solar Stirling
In this solar energy is converted to thermal and used to run stirling engine
which is further used to run generator to produce AC supply. When there is no
external use the energy is stored in battery after the conversion of AC to DC.
These batteries are used as a backup power when needed.
Figure 6.4: Solar Stirling
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30. Chapter 7
Heating from Solar Power
7.1 Introduction
In many cases solar power is used only to heat up the water. This is done in such
a way that solar plates heat up the heat exchanger in which working fluid is water
which we have to heat up. This water is passed through heat exchanger which
consists of coiled pipe and then enters to hot water storage tank so that it can be
used. In such a way we heat up our water indirectly through solar system. This
is called solar water heating system.
7.2 Solar Water Heating
Solar water heating systems include storage tanks and solar collectors. There are
two types of solar water heating systems:
• Types of Solar Water Heating
There are two types of solar water heating system
Active Solar Water Heating System
Passive Solar Water Heating System
but we are using active solar heating system as it is less complicated and easy to
design.
7.2.1 Active Solar Water Heating System
There are furthur two types of active solar water heating systems:
• Direct Circulation System
Pumps circulate household water through the collectors and pass it into the
home for usage. They work well in weather conditions where it rarely freezes.
• Indirect Circulation System Pumps circulate a non-freezing, heat-transfer
fluid through the collectors and a heat exchanger. This heats the water that flows
into the home. They are popular in climates prone to freezing temperatures.
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31. Power Plant Engineering
Methodology
In this system we use flat plate collectors which captures sunlight and this
sunlight is used to heat the working fluid which is water and this water when
heats up due to sunlight is sent to heat exchanger which consists of coiled pipe
and this heat exchanger is linked with hot water storage tank and the portion of
hot water storage tank is also present in kitchen of our house when this hot water
storage tank gets heated due to heat exchanger in which warm water flows then
the water present in hot water storage tank is used in house and the body of hot
water storage tank is used for cooking purpose carefully.
Figure 7.1: Active Solar Water Heating
7.3 Storage Tanks And Solar Collectors
Most solar water heaters require a well-insulated storage tank. Solar storage tanks
have an additional outlet and inlet connected to and from the collector. In one-
tank systems, the back-up heater is combined with the solar storage in one tank.
Three types of solar collectors are used for residential applications:
• Flat Plate Collector
• Integral collector-storage systems
• Evacuated-tube solar collectors
7.3.1 Flat Plate Collector
Glazed flat-plate collectors are insulated, weatherproofed boxes that contain a dark
absorber plate under one or more glass or plastic (polymer) covers. Unglazed flat-
plate collectors – typically used for solar pool heating – have a dark absorber plate,
made of metal or polymer, without a cover or enclosure.
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32. Power Plant Engineering
7.3.2 Integral collector-storage systems
Also known as ICS or batch systems, they feature one or more black tanks or tubes
in an insulated, glazed box. Cold water first passes through the solar collector,
which preheats the water. The water then continues on to the conventional backup
water heater, providing a reliable source of hot water. They should be installed
only in mild-freeze climates because the outdoor pipes could freeze in severe, cold
weather.
7.3.3 Evacuated-tube solar collectors
They feature parallel rows of transparent glass tubes. Each tube contains a glass
outer tube and metal absorber tube attached to a fin. The fin’s coating absorbs
solar energy but inhibits radiative heat loss. These collectors are used more fre-
quently for U.S. commercial applications.
In our house we are using flat plate collector for heating purpose.
7.4 Room Air Heaters
Air collectors can be installed on a roof or an exterior (south-facing) wall for heat-
ing one or more rooms. Although factory-built collectors for on-site installation
are available, do-it-yourselfers may choose to build and install their own air collec-
tor. A simple window air heater collector can be made for a few hundred dollars.
The collector has an airtight and insulated metal frame and a black metal plate
for absorbing heat with glazing in front of it. Solar radiation heats the plate that,
in turn, heats the air in the collector. An electric fan or blower pulls air from
the room through the collector, and blows it back into the room. Roof-mounted
collectors require ducts to carry air between the room and the collector. Wall-
mounted collectors are placed directly on a south-facing wall, and holes are cut
through the wall for the collector air inlet and outlets.
7.4.1 Methodology
In our house we are installing Air collectors on a roof for heating the house and
the thermostat is present between the Air collector and the internal temperature
of the house when the temperature of the internal temperature is 10 times less
than the temperature of air collector then the thermostat allows the fan which is
present along with the air collector and which runs with the thermal energy for
which separate plate is attached to turn on and allow the cold air of internal house
to circulate from the air collector to heat up and enters in the house again.During
summer season this thermostat can be tripped manually.
7.5 Installing The System
The proper installation of solar water heaters depends on many factors. These
factors include solar resource, climate, local building code requirements, and safety
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33. Power Plant Engineering
issues
For our house we use 50 gallons of hot water storage tank and in its thermostat
plays the key role for heating system and this thermostat can be tripped manu-
ally.The heart of the control system is a differential thermostat, which measures
the difference in temperature between the collectors and storage unit. When the
collectors are 15 to 25o
F (7 degree to 15 o
C) warmer than the storage unit, the
thermostat turns on a pump or fan to circulate water or air through the collector
to heat the storage medium or the house.
7.6 Calculation of Heat Energy from Hot Water
The required temprature of water is 75o
C.
The temperature of Source Water = 25o
C.
The desity of water is =1000kg/m3
.
The Specific heat of water = 4.18 KJ/Kgo
C.
The water supply for family of three is 3x 70L/day = 210Liter/day
The energy for heating water is
qhw(t) = pw.Q(t).cpw.[Td − Ts]
putting values in equation we get 71450kJ/day
for one month value of energy is 71450 x 30 = 2.1MJ/month
• System Design
Figure 7.2: Open loop Water Heating
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34. Chapter 8
Cooling From Solar power
Many of us will wonder after seeing this cooling from solar power but it is possible
and there are different methods
8.1 Flat Plate Collector
Flat-plate collectors are the most widely used kind of collectors for domestic water-
heating systems and solar space heating/cooling. A typical flat plate collector con-
sists of an absorber, transparent cover sheets, and an insulated box. The absorber
is usually a sheet of high thermal conductivity metal such as copper or aluminium,
with tubes either integral or attached. Its surface is coated to maximise radiant
energy absorption and to minimise radiant emission. The insulated box reduces
heat loss from the back or the sides of the collector. The cover sheets, called
glazing, allow sunlight to pass through the absorber but also insulate the space
above the absorber to prevent cool air to flow into this space.
8.2 Desiccant cooling system
Desiccant cooling systems are basically open cycle systems, using water as a re-
frigerant in direct contact with air. The thermally driven cooling cycle is a com-
bination of evaporative cooling with air dehumidification by a desiccant. For this
purpose, liquid or solid materials can be employed. The term open is used to indi-
cate that the refrigerant is discarded from the system after providing the cooling
effect, and new refrigerant is supplied in its place in an open-ended loop. The
common technology applied today uses rotating desiccant wheels, equipped either
with silica gel or lithium-chloride as sorption material. For the choice of the type
of chillers, the following parameters have to be evaluated in advance:
• The operating temperatures of the absorption machine, as they affect the choice
of solar collector.
• The values of the coefficient of performance (COP) of the chiller, as they
change according to the above mentioned temperatures and also according to the
heat distribution system installed (e.g. fan-coils or radiant floor).
The choice of the type of solar collectors is not a difficult task. The function-
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35. Power Plant Engineering
ing temperature of the absorption chiller determines the most suitable typology
of collectors for different layouts. Dimensioning of the panels surface follows the
same rules of domestic solar plants for hot water production, even though the fact
that a solar cooling plant operates at higher temperatures has to be taken into
account.
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