This document summarizes a student project to build a solar powered water heater. It describes the materials used, which were kept cheap to remain within budget. It details the construction process and testing of the prototype. Testing showed it increased water temperature over 31 degrees, exceeding requirements. Calculations determined the device could save money if used long-term by an individual, but may not be highly profitable to mass produce due to manufacturing costs. Further testing is needed to refine efficiency calculations.

1. Project 2:
Solar Powered Water Heater
Jacob Aucoin
Nicholas Chua
Dijon Hill
Harold Nero
Due Date: 10/24/2014

2. ABSTRACT
This report is about the successful development of a prototype hot water heater using beverage cans and
other materials within the range of a budget. In order to remain in budget, research on possible materials that
can be used to build this prototype cost effectively was necessary. After completing our search, we narrowed
down the best options for the project before proceeding to the building phase. The idea was to make the exterior
box as cheap as possible so we could invest into the performance of the actual system that is within the box. We
discovered hiccups along the way as we began to build this solar powered water heater and wasted no time in
correcting those issues. After everything in the unit was in place, we tested the flow rate and temperature
change various times to ensure our efforts were not in vain. When testing gave back positive results we were
confident that we made a unit that gave us the results necessary to pass the in class testing while managing to
remain within budget
INTRODUCTION
Of the numerous problems that this project brought to the table, we managed to face each one head on
and conquer them one by one. One problem, that remained ever-present, was not exceeding our budget of $75.
The first problem was determining a reasonably sized prototype even though we were given maximum
dimensions of 4ft x 8ft x 1ft. For our purposes, we quickly came to the conclusion of simply halving the
maximum dimensions given to us by our instructor at the height, length, and depth of 2ft x 4ft x 0.5ft. Although
briefly stated in the previous section, part of our analysis for this project was to determine the materials we
would use to build our prototype. We determined many options for different parts of the project to be very
effective but we soon found out that the best route would not always keep us below budget. Keeping the budget
in mind made the selection of materials easy because the majority of the options out there were more than likely
going to take us over our predetermined $75 budget.
We already knew that this budget included the value of cans and all parts, including “found” and
“repurposed” items. Later on in our analysis, the cost of labor and overhead would also have to be considered.
The design is constrained by the flow rate and temperature increase. The minimum flow rate is ½ gallons per
minute and the minimum change in temperature, from entrance to exit, must increase 5 to 12 degrees. Part of
our analysis was realizing that the prototype was mainly constrained by the cost, so the goal was to build a
sufficiently large box that could be cheaply sealed to increase convection within the box heated by black cans.
Ideally, we wanted water touching aluminum for better conduction, but the added cost of sealing cans water
tight or running water through faster to avoid leaking was more trouble than it was worth. Through further
thought, we realized that this would be corrected with the particular type of hosing that was used. So instead, we
relied on the convection within the box to help transfer the heat threw a ½” plastic tube running through rows of
black cans. This added reliability and helped maintain the required flow rate. Our design has a leak-free tube
running through rows of cans. What sets our prototype apart, is the well-sealed box and large number of cans.
An outline of our design will be seen at the end of the report.
EQUIPMENT
For testing we used two five gallon buckets, a thermometer, and a stopwatch. Our box was built out of a
plywood (2ft x 4ft x 0.25in), wood (1x6x12) that was cut down to build the four sides of the box and nailed
together, and sealed with saran wrap after the placement of our system within the box. The cans were lined up
in rows with a ½” vinyl tube running through the cans, all cans were tapped with HVAC Foil Tape and they

3. were spray painted black to absorb the maximum amount of sunlight. Other equipment that was used along the
way included: nails, aluminum foil, reflective tape, a hose connector, package tape, and a funnel.
PROCEDURE
In constructing this unit, we brought all of our materials in front of us to ensure that everything we
needed to make this project would be within our grasp. The device was left good sun light for about 20 minutes
to reach its maximum temperature. The temperature of the prepared water was measured and recorded as 71
degrees Fahrenheit. Water was then poured into the inlet of the tube and when water began flowing out at a
steady state, the stopwatch was started until ½ gallons had flowed through steadily. The change in temperature,
dT, over the change in time gave us a result of ½ gallon per min flow rate, shown as dV in later figures where
you can follow the calculations for the power absorbed by the water. The gal per min flow rate was changed to
gal per second then multiplied by the density of water, rho, in kg per gallon giving the mass flow rate, dm, in kg
per second. (Cengel & Boles, 2011) The mass flow rate was then multiplied by the specific heat of water, Cp, at
71 degrees Fahrenheit and the temperature change in Kelvin giving the power in Watts absorbed by the water.
(Cengel & Boles, 2011) The solar power was assumed to be 500W/m², which after multiplying by the area of
cans, gives the solar power supplied to the prototype. Water is poured through, while flow rate and temperature
are measured at the outlet. The energy being absorbed by the water is calculated from the temperature change
and flow rate. If compared to the energy available from the sun, our design can be evaluated by its efficiency.
The prototype can also be evaluated by its manufacturing cost per unit.
DATA/RESULTS
The manufacturing cost came to $68.29. With a 20% margin, the retail price would be $81.95. After
1000 units a profit of $1660.00 is expected. The overhead and equipment cost are negligible. This is because it
is so easy to assemble and could be done in any workshop or garage with a saw and drill. The 1 hour of
assembly is conservative and could range more between 30-45 minutes. All the costs are shown in , the
manufacturing cost, retail price, & potential cost and profits for 1000 units are shown in a later figure. A plot of
the cost is also shown in later figures.
The solar powered water heater worked as expected and the temperature rose by 31 degrees, 25 degrees
more than the required minimum. The efficiency of a device with an increase of 5 degrees is 87.3% Therefore
there is no reason for improvements, but more testing is needed. The initial temperature of the mass of
aluminum is causing such a large temperature change that the results show that a steady state was never
reached. If it reached steady state, the efficiency would be 641%. In additional testing an initial hot temperature
for calculating the energy lost by the aluminum or longer testing is required to reach the temperature at which
the solar energy balance the energy removed by the water. The power supplied by the sun is 500W/m². The
power removed by the water is calculated from the specific heat at constant
pressure. (Cengel & Boles, 2011) For the more conservative and realistic estimate
with a temperature gain of 5 degrees Fahrenheit see later figures. These figures show not only the efficiency’s,
but also the cost savings and payback period and various other important data.
CONCLUSION
The prototype, as designed now, could save someone money. Although it would take a long time to
make any profits and a lot of man hours to create the amount of units necessary to even make a profit if we
viewed our idea in retrospect to a small startup company. At the conservative 5 degree Fahrenheit increase it

4. could possibly pay for itself in 8 months if a group of brave individuals were willing to go through with this
idea of being economically conscious. Tests of our unit conclude that our choice was highly effective in getting
the end results but calculations seem to show that it is not highly profitable in the long run. Our analysis works
in the since of making only 1 unit and using that same unit over a long period of time (This is how we can get a
large return on our investment). However, the opposite becomes true when we are making several units that
need to be distributed for only a 20% rate of profit. In order to get all of our data to be perfectly unified across
the board, many more tests would have to be conducted to rule out all possible scenarios. This product can be
improved by taking out materials that increase the amount of heat coming to our system and make the unit as
basic as possible (which would also take away from the amount of time needed in making the unit). In closing,
one possible theory that was missing from the theory of this project was the concept of the transfer of heat
between mediums. This is because our heat source that we get from the sun must pass into our box via radiation,
once the box is heated then that heat must in turn heat the cans, and once the cans are heated then the heat in the
cans must be high enough (which it was) to heat the water in the hose. In other words, further calculations could
have been done to show the passage of heat through all of the mediums that made up our unit.

5. Date Account Description Hotel Subtotal 8% Tax 9% Tax 9.75% Tax Misc. Total
10/8/2014 N/A Vinyl Tubing (2) N/A $14.98 $1.20 $16.18
10/9/2014 N/A HVAC Foil Tape N/A $7.98 $0.64 $8.62
10/9/2014 N/A Nails N/A $1.50 $0.14 $1.64
10/9/2014 N/A Aluminum Foil (2) N/A $4.00 $0.36 $4.36
10/9/2014 N/A Black Paint N/A $1.92 $0.15 $2.07
10/9/2014 N/A Wood 1x6x12 N/A $7.48 $0.73 $8.21
10/9/2014 N/A Reflective Tape N/A $3.25 $0.32 $3.57
10/9/2014 N/A Saran Wrap N/A $2.27 $0.22 $2.49
10/9/2014 N/A Package Tape N/A $1.00 $0.09 $1.09
10/9/2014 N/A Connector N/A $2.99 $0.24 $3.23
10/9/2014 N/A Wood 0.25x2x4 N/A $8.52 $0.77 $9.29
10/9/2014 N/A Funnel N/A $4.37 $0.39 $4.76
10/9/2014 N/A Aluminum Cans N/A $2.78 $2.78
$0.00
$0.00
$0.00
$0.00
$0.00
Total $0.00 $63.04 $2.23 $0.50 $2.52 $0.00 $68.29
SUBTOTAL $68.29
APPROVED: NOTES: ADVANCES $0.00
TOTAL $68.29
APPENDIX
Figure 1: Table of Material Costs
Figure 2: Plot of Material Cost

6. Figure 3: Break Even Analysis
Figure 4: Price Estimates
BREAK-EVEN ANALYSIS
Break Even Units:
Retail Price per Unit:
Expected Unit Sales:
Total Variable Unit Costs:
Total Fixed Costs (Overhead):
You will be making profit after 878.48 units.
81,950.00
-7,902.00
-6,536.00
-5,170.00
-3,804.00
-2,438.00
-1,072.00
294.00
1,660.00
8,195.00
16,390.00
24,585.00
32,780.00
40,975.00
49,170.00
57,365.00
65,560.00
73,755.00
66,632.00
73,461.00
80,290.00
52,974.00
68,290.00
59,803.00
6,829.00
13,658.00
20,487.00
27,316.00
34,145.00
40,974.00
47,803.00
54,632.00
61,461.00
12,000.00
12,000.00
12,000.00
12,000.00
12,000.00
12,000.00
12,000.00
12,000.00
12,000.00
12,000.00
1,000
300
878.48
Fixed Cost Variable Cost Total Cost
400
500
600
700
800
900
18,829.00
25,658.00
32,487.00
39,316.00
46,145.00
12,000.00
68.29
1,000
81.95
Revenue ProfitUnits
100
200
-10,634.00
-9,268.00
0
50000
100000
150000
200000
250000
300000
Revenue
Units
Fixed Cost
Variable Cost
Total Cost
Revenue

7. Figure 5: Energy & Efficiency
SUN:
L, m W, m A, m^2 min, W/m^2 max, W/m^2 P_min, W P_max, W P_solar, W
0.6 1.2 0.7 500 700 348.7 488.2 418.5
WATER:
dV, gal/min dV, gal/s rho, kg/gal dm, kg/s Cp, J/kg-K dT,F dT,K P_water, W
0.5 8.33E-03 3.77 0.0315 4.18E+03 5 2.8 365.2
Energy Saved:
η 87.3% Energy, kWh/day 2.9
Avg US Elec.($/kWh) 0.13$
Yearly Savings 136.81$
Monthly Savings 11.40$
Payback (months) 7.8
EFFICIENCY:
Figure 6: Energy and Efficiency
SUN:
L, m W, m A, m^2 min, W/m^2 max, W/m^2 P_min, W P_max, W P_solar, W
0.6 1.2 0.7 500 700 348.7 488.2 418.5
WATER:
dV, gal/min dV, gal/s rho, kg/gal dm, kg/s Cp, J/kg-K dT,F dT,K P_water, W
0.5 8.33E-03 3.77 0.0315 4.18E+03 31 17.2 2264.1
Energy Saved:
η 541.1% Energy, kWh/day 18.1
Avg US Elec.($/kWh) 0.13$
Yearly Savings 848.21$
Monthly Savings 70.68$
Payback (months) 1.3
EFFICIENCY:

8. Figure 7: Hand Written Calculations

9. Figure 8: Hand Written Calculations Continued

10. Figure 9: Hand Written Calculations Continued

11. Figure 10: Receipts

12. Figure 11: Receipts Continued

13. Figure 12: Receipts Continued

14. Figure 13: Dimensional Design and Parts

15. Figure 14: Dimensional Design and Parts Continued
References
Cengel, Y. A., & Boles, M. A. (2011). Thermodynamics: An Engineering Approach (7th ed.). New York, NY, US: McGraw-
Hill. Retrieved 10 22, 2014