Solar Pool Heater

Question

A pool owner is building a solar heater to keep her pool a comfortable 85°F. So far, she has a design that consists of piece of wood with black drip irrigation tubing coiled around and secured. This part of the design is shown in the picture.

The pool owner is making a few choices in the design of the solar heater. She is deciding whether to leave the wood plain or paint it, either white or black. She wants to choose the option that will help the solar heater warm the pool quickest. To make her decision, she cuts three pieces of wood that are one foot by one foot. Then, she paints one of them white and one of them black. She leaves the third piece of wood its original color. She places the three pieces of wood into the sunlight for 30 minutes and records their temperatures every five minutes. The table shows this data.

Wood Color Temperatures (in °F)
0 minutes 5 minutes 10 minutes 15 minutes 20 minutes 30 minutes
Plain Wood 75 75 76 76 77 77
White Paint 75 75 75 75 76 76
Black Paint 75 76 78 80 81 82
The second decision the pool owner would like to make is whether she should use 100 feet of drip irrigation tubing or 200 feet of drip irrigation tubing. She would also like to connect the design to a small programming device that will turn the water pump for the pool on and off based on the pool's temperature. When the pump is on, water will be pumped out of the pool and through the black tubing. Then, the water will flow back into the pool as it exits the tubing. When the pump is off, no water will be pumped out of the pool and through the black tubing. The pool owner needs to decide how to program the device so that the temperature of the pool is as
The following question has two parts. First, answer Part A. Then, answer Part B.

Part A:

After the pool owner finalizes her design, she runs the solar heater. The graph shows the data she collects during a 24-hour period.

Use the data to identify how the design has failed.

A.
The solar heater causes the pool to heat up to above average temperatures at night.

B.
The solar heater causes the pool to cool down below average temperatures at night.

C.
The solar heater causes the pool to heat up to above average temperatures during the day.

D.
The solar heater causes the pool to cool down below average temperatures during the day.

Multiple Choice Question
Part B:

How could the design be updated to address this failure of the design?

A.
The solar heater can be programmed to stay off at night.

B.
The solar heater can be programmed to stay on at night.

C.
The solar heater can have longer tubing to cool the pool more during the day.

D.
The solar heater can have longer tubing to warm the pool more during the day.

Answer 1

Part A:

To determine how the design has failed, we need to consider how the solar heater affects the pool temperature over the course of a day and through the night.

Based on the options given:

• Option A: "The solar heater causes the pool to heat up to above average temperatures at night." This would imply the heater is still working at night, which is usually not the case.

• Option B: "The solar heater causes the pool to cool down below average temperatures at night." This could indicate that the heater is not providing any heat during the night, and the pool is not retaining heat effectively.

• Option C: "The solar heater causes the pool to heat up to above average temperatures during the day." This would be a desired outcome of the solar heater.

• Option D: "The solar heater causes the pool to cool down below average temperatures during the day." This would indicate that the heater is not functioning as desired, as it should be heating the pool.

Considering typical solar heater behavior, if pools are losing heat at night, the correct answer seems to be:

B. The solar heater causes the pool to cool down below average temperatures at night.

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Part B:

To address the identified failure from Part A, we should consider options that would help maintain or stabilize the pool temperature, particularly at night when the temperatures drop.

• Option A: "The solar heater can be programmed to stay off at night." This would not address the cooling issue; instead, it would allow the pool temperature to drop.

• Option B: "The solar heater can be programmed to stay on at night." This is unlikely for a solar heater, as it typically relies on sunlight.

• Option C: "The solar heater can have longer tubing to cool the pool more during the day." This would be counterproductive since the goal is to heat the pool, not cool it.

• Option D: "The solar heater can have longer tubing to warm the pool more during the day." This option addresses the issue of maximizing heating during the day, which could lead to higher heat retention.

The most suitable option here appears to be:

D. The solar heater can have longer tubing to warm the pool more during the day.

This option helps increase the volume of water heated during sunny periods, which may aid in retaining the pool temperature, making it warmer during the day and potentially affecting the amount of heat lost at night.