Energy

Using solar energy wisely

When is the optimal time to use solar panels?

Grade

Duration

40 mins

Type

Group work

Overview

Students graph monthly quadratic data on solar radiation and use the evidence from the graphs to advise a homeowner about the times of day and months when the use of solar panels would provide the greatest reduction in electricity usage.

Instructions

What you'll need

Digital projector and screen
"Predicting a pattern" worksheet
"The relationship between time and total solar radiation" handout
"Gathering important mathematical evidence" worksheet
"Monthly graphs" handout

Organize your students into small groups and provide each student with a copy of the "Predicting a pattern" worksheet. Review the scenario described on the worksheet with your students, and invite them to suggest the times of day and months of the year the homeowner should use the solar panels to reduce electricity usage the most. Invite groups to share their decisions and thinking with the class.
Direct students’ attention back to the worksheet, and ask groups to now create a graph to show their initial thinking about the relationship between time of day and the intensity of sunlight.
Provide each group with a copy of the "The relationship between time and total solar radiation" handout, and each student with a copy of the "Gathering important mathematical evidence" worksheet. Assign each group one of the months.
Ask groups to graph the monthly data from their assigned month using appropriate graphing technology. After groups have graphed their data, ask them to record the information for their assigned month on the "Gathering important mathematical evidence" worksheet.
Invite groups to share their graphs and worksheets with the class using one of the following methods:
- Transfer their graphs and worksheet data on whiteboard or chart paper
- Share their electronic graphs and worksheet data using a projector

Provide time for students to view and record the information for other months on their "Gathering important mathematical evidence" worksheet.

Encourage students to identify any patterns that might be noticed across the monthly representations and the data. Invite students to revisit their initial graphs and advice to the homeowner: what would they change given these patterns?
Working as a class, name the graphs as quadratics and discuss the general features of a quadratic function, introducing key mathematical vocabulary (e.g., vertex, max/min, x-intercepts, symmetry).
Guide students’ attention to bottom of "Predicting a pattern" worksheet. Invite students to note their final advice to the homeowner using their new learning and the mathematical evidence they have gathered. Invite students to share their advice with the class: What stayed the same? What changed?

Modify or extend this activity

Provide students with the equations for each quadratic function and ask them to match the equations to the most appropriate graph. Remind students that the properties of a quadratic are simply any characteristics that hold true across a given set of examples.
Provide students with the graphs of each function with and without restrictions and ask them which is most appropriate given the context of the problem.
Invite students to sketch a graph using the tables of value so that they pay closer attention to numerical values and are better able to identify the emerging patterns.
Your students’ final advice to the homeowner could be offered as an “exit slip” and evidence of learning.

Curriculum Fit

Foundations of Mathematics 11

Big idea

Optimization informs the decision-making process in situations involving extreme values

Content

Graphical analysis (using technology only)
- Quadratic functions (characteristics including end behaviour, max/min; vertex; symmetry and intercepts)
- Optimization (maximizing and minimizing quantities in authentic contexts)

Curricular competencies

Reasoning and modelling

Explore, analyze, and apply mathematical ideas using reason, technology, and other tools
Estimate reasonably and demonstrate fluent, flexible, and strategic thinking about numbers
Model with mathematics in situational contexts
Think creatively and with curiosity and wonder when exploring problems

Understanding and solving

Develop, demonstrate and apply mathematical understanding through inquiry and problem-solving
Visualize to explore and illustrate mathematical concepts and relationships

Communicating and representing

Use mathematical vocabulary and language to contribute to discussions in the classroom
Explain and justify mathematical ideas and decisions in many ways
Represent mathematical ideas in concrete, pictorial, and symbolic forms

Connecting and reflecting

Reflect on mathematical thinking
Connect mathematical concepts with each other, other areas, and personal interests

Teaching Notes

Ensure students recognize the necessary restrictions placed on graphs, tables of value, and equations within real world contexts.
The "Monthly graphs" handout shows 12 graphs of quadratic functions (with and without restrictions), along with the equations in x-intercept form--y = a (x-b) (x-d), that align to the tables of value given above.

Solar power in B.C.

Solar energy is an affordable alternative energy that can be used to help heat and power your home, school, or business. However, there are some important considerations around the use of both solar photovoltaic and solar thermal systems in British Columbia that you should be aware of. Check out bchydro.com for more information regarding the practicality of solar energy in our province.

Assessment

Throughout the activity, consider how well students:

Identify general patterns to construct understanding of the properties of the given set of quadratic functions.
Identify more specific patterns to construct understanding of the availability of solar energy.
Analyze graphs to provide sound mathematical advice to the homeowner.
Determine the potential solar radiation output, solar radiation start and end points and patterns.
Use appropriate vocabulary (max/min; x-intercepts; vertex; symmetry) to make recommendations.
Refine and extend their thinking throughout the lesson
Pay close attention to appropriate details.

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