Design When planning our design, we focused on how

we could heat copper tubing and maximize heat

transfer to the water traveling through the

tubing, and minimize heat loss to the

surroundings. The challenge was to build this in a

cost-effective way with the resources we had. We

went through the following 3-step process to

funnel proposed ideas into a final design:

We decided to build an insulated “box” collector

that sheltered the copper tubing, and used plastic

tubing connected to the copper to feed the water

in and out of the collector. The goal was to

insulate the inside of the box to maximize the heat

inside the box and direct that heat to the copper

tubing.

Solar Water HeaterBy Sarah Bailey Glasgow, Cameron Goodman, DeLys Valentine, & Nick Wadsworth Problem Statement

We were presented with the challenge of making a

solar water heater that maximized the temperature

of the water, while minimizing cost and the use of

resources.

The water heater would be tested using a 500 Watt

halogen lamp, which served as a simulated “sun.”

We were given a 1 gallon plastic bucket filled with 2

liters of water and 5 minutes with the device under

the halogen lamp to increase the temperature of the

water as much as possible.

Additionally, we had to meet the following

requirements:

•  The device must maintain a minimum distance of

12 in away from the halogen lamp (mounted 3 ft.

above the floor) during testing.

•  Any basins or collectors can be no larger than

2’x2’x2’

•  All 2 L of water must be returned to the bucket by

the end of the 5-minute testing period.

•  Once the heating process starts it must be self-

operating.

•  The plastic bucket cannot be directly under the

lamp.

Results & Conclusion

ΔT = 0.8 °CWhen tested, our solar heater raised the temperature

of 2 L of water 0.8 °C in 5 minutes. The solar heater

was effective, just not as effective as we had hoped.

The change in temperature was minimal possibly

because of heat escaping from the inside of the

collector. We could improve our heater by ensuring

that the inside of the collector was sealed tightly.

Another improvement we could make is to paint the

copper tubing black to increase the heat absorbed

by the copper and thus the heat transfer to the water.

Is it efficient

and reliable?

Does it minimize the use of resources?

Is it cost-effective?

Bill of MaterialsMaterial Quantity Cost ($) Purpose

18”x 24” sheet of Plexiglas

1 10.76 The Plexiglas provides a top for the collector that seals heat in without interfering with light entering the collector.

Assorted Styrofoam 8 0 Styrofoam helps insulate the sides of the collector to maximize heat gained and maintained inside the collector.

Assorted plywood 5 2.20 Plywood forms the frame of the collector.5’ of 3/8” copper tubing 1 3.50 Copper is considered a good thermal conductor, which made it an ideal material

to use for heating water. 5’ of plastic tubing 1 0.75 The plastic tubing attaches to the copper tubing and to the water pump to make

a route for the water to and from the bucket of water.5 oz. of wood glue 1 1.00 Wood glue holds the pieces of plywood together that make up the frame.1 yd. of duct tape 1 0.20 Duct tape secures the pieces of Styrofoam to the outside of the frame.

Silicone gel - 0 We used silicone to adhere the sheet of Plexiglas to the frame of the collector and to provide a seal that aims to minimize heat loss to the surroundings.

5’ of aluminum foil 5 ft. 0.15 The covering of aluminum foil on the bottom of the collector provides a reflective surface that directs the light from the lamp to the copper tubing,

allowing it to gain more heat.Water pump 1 10.00 We used the water pump to move the water through the collector as we did not

have any differences in height to utilize gravity.Push on fittings 2 6.00 Push on fittings attach the copper tubing to the plastic tubing.

Total Cost: $34.56

References: •  “Cheap and Easy Passive Solar Water Heater…” http://

www.instructables.com/id/Cheap-Solar-Water-Heater-for-your-Home-300/

•  “How to Build a Soda Can Heater” http://www.instructables.com/id/How-to-Build-a-Soda-Can-Heater/

CalculationsTotal cost estimate $34.56

Heat transfer to water 6.698 kJ

Heat transfer from “sun” 28.646 kJ

Work done on system by pump 0.005 kJ

Energy efficiency 23.38%

Total cost per degree change $43.20/°C

Heat transfer to water per dollar 0.194 kJ/$

Total cost per percent efficiency $147.81/%

Right: A view of the collector from above.

Engineering Fundamentals 152

Section 3d