Design Calculations for Solar Water Heating System

Chapter 1 City of Residence
Chapter 2 Estimation of Available Solar Resources
Chapter 3 Site Survey
Chapter 4 Load Estimation
Chapter 5 Estimation of Required Absorber Area
Chapter 6 Market Survey & Estimation of No. of Tubes for ETC
Chapter 7 Economical Analysis & Estimation of Payback Period
Chapter 8 Conclusion

1. Report
on
Design Calculations for Solar Water Heating
System for Domestic Application

This report is submitted in fulfilment of the requirements of the Seventh
semester B.E. in Mechanical Engineering.

Submitted By
Roll No. Name of Student
60 Sangeet Khule


Under the guidance of
Dr. Sandeep S. Joshi
(Dept. of Mechanical Engg.)

DEPARTMENT OF MECHANICAL ENGINEERING
SHRI RAMDEOBABA COLLEGE OF ENGINEERING &
MANAGEMENT , KATOL ROAD, NAGPUR, INDIA-440013
2020-2021

2. CONTENTS
Chapter Topic Page No.
LINK OF EXCEL i
Chapter 1 City of Residence 1
Chapter 2 Estimation of Available Solar Resources 2
Chapter 3 Site Survey 4
Chapter 4 Load Estimation 6
Chapter 5 Estimation of Required Absorber Area 8
Chapter 6 Market Survey & Estimation of No. of Tubes for ETC 11
Chapter 7 Economical Analysis & Estimation of Payback Period 15
Chapter 8 Conclusion 18

3. i

LINK OF EXCEL

(https://onedrive.live.com/edit.aspx?cid=8c4817d6aab2fed0&page=view&r
esid=8C4817D6AAB2FED0!8767&parId=8C4817D6AAB2FED0!103&app
=Excel)

 Arrangement in excel is rough.

 Proper presentation is in the below report.

4. 1

CHAPTER 1

CITY OF RESIDENCE


Fig 1.1. Location

Address:
Hindustan Colony, Amravati Road, Nagpur, 440033

Latitude: 21 ° 08’ 47.4’’ N ( 21.14639° )

Longitude: 79 ° 02’ 46.0’’E ( 79.04611° )

(Location was found out using Google Maps)

5. 2

CHAPTER 2

ESTIMATION OF AVAILABLE SOLAR RESOURCES

Visited the following website for estimation of All-Sky Surface Shortwave
Downward (https://power.larc.nasa.gov/data-access-viewer/)


Fig 2.1. Step 1



Fig 2.2. Step 2

6. 3


Fig 2.3. Step 3

After the completion of steps 1, 2, and 3 we got the excel. With help of it, the
following average value of solar radiation and its graph throughout the year
2020 was generated.

AVERAGE VALUE: 4.908634 kW-hr/m
2
/day


Fig 2.4. Graph of solar energy

7. 4

CHAPTER 3

SITE SURVEY

Now we will see the following
Available shade-free area in m
2
(With actual photographs, shading analysis,
shade-free area)

As there is very little shade-free area, we will assume that the following area is
a shade-free area

Total Area = 80.321 + 80.321 + 55.741 m
2

Total Area = 216.383 m
2




6.096 X 13.176 m
80.321 m
2

(a) Terrace 1

8. 5


6.096 X 13.176 m
80.321 m
2

(b) Terrace 2



55.741 m
2

(C) Garden
Fig 3.1. Site survey at 4:00 pm

9. 6

CHAPTER 4

LOAD ESTIMATION

Now we will see the following

( All the calculations and graphs is done using excel )

 Hot water requirement in Liters/day. (150 LPD)
 Hot water consumption pattern for a typical day.
 Required temperature. (49°C)

Table 4.1 Hot water requirement in Liters/day
MEMBERS REQUIREMENT TOTAL
1 20 1 20
2 40 1 40
3 30 1 30
4 30 2 60
150 LPD

LPD = Litres Per Day

Table 4.2 Hot water consumption pattern for a typical day
TIME REQUIREMENT IN LITRES
6:00 AM 0
7:00 AM 0
8:00 AM 40
9:00 AM 30
10:00 AM 20
11:00 AM 0
12:00 PM 30
1:00 PM 0
2:00 PM 0

10. 7

3:00 PM 0
4:00 PM 0
5:00 PM 0
6:00 PM 0
7:00 PM 30
8:00 PM 0
9:00 PM 0
10:00 PM 0
11:00 PM 0
12:00 AM 0
1:00 AM 0
2:00 AM 0
3:00 AM 0
4:00 AM 0
5:00 AM 0
6:00 AM 0
150


Fig 4.1. Graph of hot water consumption pattern for a typical day

Required Temperature of Hot Water = 49°C

11. 8

CHAPTER 5

ESTIMATION OF REQUIRED ABSORBER AREA

Now we will see the following

Estimation of required absorber area for (FPC and ETC)

Energy balance equation:
m * Cp * (Th-Ta) = Efficiency * Average Radiation * Area of collector

Ab = m x Cp x dt

η x Rad

Symbol Meaning Values Unit
Ab Absorber Area ? m
2
M Mass of Water 150 Kg
Cp Specific Heat Capacity 4186 J/Kg°C
Δt Temperature Difference 23 °C
η Efficiency 0.4[FPC(40%)]
0.6[ETC(40%)]
-
Rad Solar Energy 4.908634 kW-hr/m
2
/day

So, let us assume Hot water temperature to be 49 degrees Celsius as it is the
ideal hot water temperature for the human body and normal tap water
temperature to be 26 degrees Celsius. As the temperature difference is 23
degrees Celsius which means the increase in the temperature generated by the
solar water heater should be 23 °C.
Hot water temperature = 49 °C
Normal tap water temperature = 26 °C
Change in temperature (Δt) = 23 °C

Solar Energy - Rad - kW-hr/m
2
/day should be converted into the W-Sec/m
2
So, kW-hr/m
2
= 1000 x 3600 W-Sec/m
2


After all the unit conversions and then putting the value in the above equation.

12. 9

We get the following,
Absorber area for flat plate collector solar water heater and evacuated tube
collector solar water heater.
FPC Ab = 14441700 FPC 2.043126119 m
2


7068432.96

ETC Ab = 14441700 ETC 1.362084079 m
2


10602649.44

Absorber area for flat plate collector solar water heater = 2.043126119 m
2

Absorber area for evacuated tube collector solar water heater = 1.362084079 m
2


EXTRA
Optimum Tilt angle in Nagpur ( According to each month )
Table 5.1 Optimum Tilt angle in Nagpur
January February March April May June
37 ° 29 ° 21 ° 13 ° 5 ° 180 °

July August September October November December
5 ° 13 ° 21 ° 29 ° 37 ° 44 °
β = 21.1666 °

As the optimum tilt angle for the application of the solar water heater should be
taken in the winter months as this will ensure the proper utilization of the solar
water heater.

The value is being as follow
βwinter = 35.2 °
Assumed winter months consist of October, November, December, January &
February.

Both the above value of optimum tilt angle satisfies the thumb rule of
calculation of optimum tilt angle, as well.

13. 10



Fig 5.1. 36 ° of flat plate solar collector

The above photo shows the existing flat plate solar water heater in my building.

The angle is equal to 36 °.

But the optimum tilt angle for my system is 35.2 degrees which are optimized in
such a way that it is more useful in the winter months.

14. 11

CHAPTER 6

MARKET SURVEY & ESTIMATION OF NO. OF TUBES FOR ETC

Now we will see the following

 Market survey for available solutions
 Estimation of no. of tubes required for ETC collectors

First, we will see the estimation of the number of tubes required for ETC
collectors.

From we got the evacuated tube having the following product description

( https://www.tradeindia.com/products/1500mm-solar-vacuum-tube-
557997.html )


Fig 6.1. 1500 mm Solar vacuum tube with product description

PRODUCT DESCRIPTION

Length(nominal): 1500mm
Inner tube diameter: 47mm

15. 12

Absorber area for evacuated tube collector solar water heater = 1.362084079 m
2

Area of tubes = Length x Inner Tube Diameter = 0.0705 m
2

No. of tubes =
Absorbe area for evacuated tube collector solar water heater
Area of tubes

No. of tubes = 19.32034155
No. of tubes required = 20

Now we will see a market survey for available solutions

FLAT PLATE COLLECTOR ( FPC )

Flat Plate Collector (FPC) Stainless Steel 150 Lpd FPC Solar Water Heater
( https://www.indiamart.com/proddetail/150-lpd-fpc-solar-water-heater-
21796743330.html )
( ₹ 15,000 )

Fig 6.2. Flat Plate Collector (FPC) Solar Water Heater
NO. OF TUBE

19.32034155
APPROXIMATE

20

16. 13


Fig 6.3. Flat Plate Collector (FPC) Solar Water Heater Product Specification

EVACUATED TUBE COLLECTOR ( ETC )

SOLERO PRIME 150 L White ETC Solar Water Heater
( https://www.havells.com/en/consumer/water-heater/solar/solar-water-
heater/solero-prime-150-l-white.html )
( ₹ 30,095 )


Fig 6.4. Evacuated Tube Collector (ETC) Solar Water Heater

17. 14


Fig 6.5. Evacuated Tube Collector (ETC) Solar Water Heater Product
Specification

We have seen a flat plate collector solar water heater as well as an evacuated
tube collector tube solar water heater.

The market survey was done in such a way that good quality was the priority.

18. 15

CHAPTER 7

ECONOMICAL ANALYSIS & ESTIMATION OF PAYBACK PERIOD

Now we will see the following

For economical analysis and estimation of the payback period

 Step 1: Know the expense of the current system.

 Step 2: Know the initial investment in the solar water heater.

STEP 1: ENERGY USAGE

So, the current system for water heating application in my house is the electric
geyser.



Fig 7.1. 2000 W Electric geyser

19. 16

For, accurate calculation of time required for heating the 150 Kg of water the
below link formulae was used.

( https://www.shaalaa.com/question-bank-solutions/calculate-time-required-
heat-20-kg-water-10-c-35-c-using-immersion-heater-rated-1000-w-anomalous-
expansion-of-water_68196 )

ie.
Power rating, P = 2000 W
Specific heat of water, S = 4186 J/Kg°C
Mass of water, M = 150 Kg
Change in temperature, Δt = 23 °C

Q is also equal to Time * Efficiency * Power rating ( P )

Assume, Efficiency = 95 % = 0.95
After substituting the values, we get time equal to
14441700
1900

After calculation
we get Time =



ENERGY USAGE = 2.111359649 * 2000

4222.719298 4.222 Units/Day


Fig 7.1. Electricity Bill’s Unit Cost

7600.894737 SEC
126.6815789 MIN
2.111359649 HRS

20. 17

The expense of electric geyser in rupees


14.52368 /Day
RUPEES 435.7104 /Month

5228.5248 /Year

STEP 2: PAYBACK PERIOD

Now we will calculate the payback period

In this case

The payback period is equal to the initial investment divided by the
expenses of the previous system.

Table 7.1 Payback Period
Initial investment (ETC) 30095 Rupees
Payback Period (ETC) 5.755925648 Years
Initial investment (FPC) 15000 Rupees
Payback Period (FPC) 2.868878044 Years

This concludes the economical analysis and estimation of the payback
period.

21. 18

CHAPTER 8

CONCLUSION

We will now conclude the report with the help of the following table.

Table 8.1 Conclusion Table
Type FPC ETC
Collector Area 2.04 m
2


1.36 m
2

No of Tubes - 20

Total System Cost ₹ 15000.00

₹ 30095.00
Best Suitable Systems Available in
Market
150 LPD 150 LPD
Annual Electricity Savings (Yearly
in Rs)
₹ 5228.52 ₹ 5228.52
Payback Period (in Years) 2.87
2 Years 11 Months
5.76
5 Years 9 Months