# Lab Report

Name:

Lab 8 Report Part 1

**Purpose/ Question**

**Hypothesis**

**Data Tables**

Data Table 1

Mass of 50mL of water (g) | Density of water (g/mL) | Beginning temp of water | Ending temp of water | Beginning Air temp | Ending Air temp |

Data Table 2

Time (min) | Temperature ( C) | Weather Changes |

0 | ||

5 | ||

10 | ||

15 | ||

20 | ||

25 | ||

30 | ||

35 | ||

40 | ||

45 | ||

50 | ||

55 | ||

60 |

**Graph**: Use Excel/Googlesheets to create the graphs below. Copy and paste the picture below.

Graph the data from Data Table 2. Place temperature on the Y-axis and time on the X-axis.

**Part 1 Analysis Questions**:

A, (you already completed this question by creating the graph above)

B. Calculate the amount of energy the water absorbed. To do this, you will use the following equation: Q = ΔTmcp. Q is the amount of energy absorbed by the water, ΔT is the change in water temperature, m is the mass (g) of the water heated, and cp is the specific heat capacity of water, which is 4.184 joules/g/ºC. You will need to use the density calculation to determine the mass of the liter of water by multiplying density by mL. Finally, convert this to watt-hours. One joule is equal to 0.00028 watt-hours.

C. Determine the percent efficiency of your solar collector. To do this, use one of the appropriate values for solar insolation (how much solar energy strikes a square meter in an hour):

Sunny, summer: 800 watt-hours per m2 (Wh/m2)

Sunny, winter: 400 Wh/m2

Partly cloudy, summer: 400 Wh/m2

Partly cloudy,winter: 200 Wh/m2

Next, multiply the appropriate value above by the area of your solar collector (0.07 m2) to determine the watt-hours received by your collector over the course of one hour. For example, on a sunny summer day, a 0.5 m2 solar collector would receive 400 watt-hours of solar energy in one hour, 0.5 m2 x 800 Wh/m2. Divide the energy that the water absorbed by the watt-hours the collector received in one hour and multiply by 100 to determine percent efficiency.

D. What are the sources of error that exist for calculating the percent efficiency of your solar water collector?

E. How would you make the collector more efficient?

**Part 1: Conclusion (1-2 paragraphs):**

-Was your hypothesis correct / incorrect? Why?

-What evidence from the lab shows that the water is absorbing energy and the solar collectors efficiency?

Lab 8 Report Part 2

**Purpose/Question**

**Hypothesis**

**Data Tables**

Data Table 3

Solar Cell parallel to Earth | Solar Cell perpendicular to Earth | Solar Cell perpendicular to Sun’s rays | |

Voltage | |||

Amperage | |||

Wattage |

Data Table 4

Maximum Wattage/Power (W) | Area of PV cell in m2 | Power Density (W / m2) |

**Graph**: Use Excel/Googlesheets to create the graphs below. Copy and paste picture of graph below.

Graph 1: Create a bar graph of your data in Table 3 to compare the different angles of the solar cell.

**Part 2 Analysis Questions:**

A. What difference, if any, was there among the different positions of the solar cell? What does this tell you about the optimal way to position solar panels for highest electricity production?

B. How many solar cells of the type you worked with would it take to light a 100 W bulb for one hour? (Assume that the bulb is used during the middle of the day, or that you have a way to store the energy the solar cell produces during the day for use at night or when it is cloudy.) How many square meters would that require?

C. How much does it cost a homeowner to use electricity for 30 years if the electricity is purchased from the electric power company? Hint: An average house in the United States uses 31.5 kilowatt hour (kWh)/day and electricity costs $0.10/kWh. This does not account for the rises in electricity prices that will occur over the next 30 years.

D. An average house in the United States uses 31.5 kWh/day. How may square meters of solar cells are need to supply all of the electricity? Use the average solar insolation of 4.2 kWh/ m2 per day and an efficiency of 15% for the solar panels, which means that they are able to convert 15% of the solar radiation that strikes them into electricity.

E. What are the limitations and advantages of using solar systems to providing electricity?

**Part 2: Conclusion (1-2 Paragraphs)**

-Was your hypothesis correct / incorrect? Why?

-What evidence from the lab shows the best angle for the silicon solar cell?

**Reflection (2-3 Paragraphs)**:

-What can you conclude about what you learned in this lab in relation to solar cells and solar energy and how much energy they produce and the efficiency?

-How does this lab relate to what you have been learning about in the Module and in your chapter readings?

**3 APA sources**