Let's Make a Solar Charger! (es)

This Maker Project is part of a unit plan, “Solar, So Good” designed for the Cambridge-Harvard Summer Academy in 2023. In this unit, students analyse the feasibility of solar power as a form of renewable energy in their communities. Students will explore how solar power works at different scales, and look at examples of how the energy of the Sun has been harnessed to support our daily lives.

This unit consists of four Maker projects, each requiring 8-10 hours of classroom time. They are designed to be carried out in order, but work well as standalone projects as well. The four projects are:

Project 1: Building a Solar Oven
Project 2: Building a Solar Lamp
Project 3: Building a Solar Charger (this project)
Project 4 (Summative Assessment): Designing a Solar Powered Home

Projects in this unit plan align with the United Nations Sustainable Development Goals and adopt a pedagogical framework rooted in the Engineering Design Process (EDP) and project-based learning (PBL). By incorporating these principles, these Maker projects aims to foster innovative thinking and practical problem-solving skills among students.

Download the unit overview and full standards alignment here.

An overview of the five lessons involved in this Maker Project is provided below:

Lesson	Learning Objectives	Steps in the Engineering Design Process	Project Details
1	Explore the concept of solar chargers, their function, and their benefits Understand the basics of electricity consumption by appliances and how energy usage can be optimized	Ask	Students read about the energy that is used in charging modern consumer appliances (e.g. handphone, laptop). Wouldn’t it be great if solar power can be used to to charge our appliances? Students are told they will design a portable solar charger with a USB-C outlet which can charge regular consumer appliances. Key criteria: time to charge. Key constraint: budget.
2 - 3	Explore the different types of solar panels Learn how to connect the solar panels in series or in parallel Design a solar charger Plan out what materials to use for their solar chargers	Research	Students explore how solar chargers work, building on their understanding of electrical circuits and solar panels in Project 2. They will also understand how to maximise the efficiency of solar panels by e.g. appropriate positioning of solar panels when charging.
		Imagine	Students work in small teams to brainstorm possible solutions, based on the design brief given.
		Plan	Students develop a decision matrix to evaluate their solutions, and identify a solar charger solution to prototype. They are given an assigned fixed budget which they can ‘spend’ on a range of materials (e.g. solar panels) provided by the instructor. Electrical materials can be ‘bought’ while maker materials will be freely available.
4 - 5	Construct the solar charger electrical parts and the repurposed materials Assess the performance of their solar charger prototypes and identify areas for enhancement	Create	Students prototype their solar chargers, using materials they have obtained from the instructor.
		Test	Students showcase and test their prototypes quantitatively, by e.g judging how long it takes to charge a phone battery by 5%.
		Improve	Students reflect on their experiences and think of ways to improve their solar chargers.

Day	1
Question	How is energy consumed in circuits?
Objective	Explain energy use & utility expense through, e.g. of, charging consumer appliances.

Summary

It’s Day 1! In this lesson, students will explore the concept of solar chargers, their function, and their benefits. They will also gain an understanding of the basics of electricity consumption by appliances and how energy usage can be optimized.

External Resources: NA

Resource	Description	Copies needed
Slides	Projectable slides for Day 1 lesson.	0 (all digital)
Day 1 Worksheet	Student worksheet	1 per student
Exit ticket	Student exit ticket	1 per student

Detailed lesson plan

Slide	Teaching Moves
Introduction to Course
	Welcome, students, to the third unit of the course.
2	Encourage students to reflect on their camping experiences and challenges with powering electronic devices or keeping them charged. Give students a few moments to think about their experiences and challenges. Some possible responses: Limited access to power sources, battery drain, and Incompatibility of chargers. Summarize the key points raised and emphasize the importance of finding practical solutions for powering electronic devices during camping trips.
3	Discuss the environmental impact of traditional power sources during camping trips, such as disposable batteries and fuel-powered generators. Emphasize the increasing popularity of camping activities and the urgent need to transition towards eco-friendly power solutions. Distribute the Design Brief. Introduce the challenge of designing a sustainable charging option while camping.
4	Introduce solar chargers as a safe and sustainable alternative for powering electronic devices during camping trips. How does a solar charger work? (Encourage learners to reflect on what they learned previously) What do you think are the materials needed to create a solar charger? (Encourage learners to think about the essential components and consider the role of each material.)
5	Define design specifications as the specific requirements and characteristics a solar charger should have to fulfill its intended purpose effectively. Emphasize the importance of considering power output, efficiency, portability, durability, and cost-effectiveness.
7	Explain the different parts present in a solar charger Solar panels capture sunlight and convert it into electrical energy; the buck converter regulates the voltage for efficient device charging, and the USB connector facilitates power transfer between the solar charger and electronic devices. Highlight the importance of these components working harmoniously to enable the solar charger to harness solar energy and convert it into usable power for charging devices. Note: Students might ask why the rechargeable battery is not included Solar chargers without rechargeable batteries prioritize direct charging of electronic devices, focusing on portability and simplicity. Including a rechargeable battery in a solar charger adds complexity, size, and weight to the design.
8-9	Revise the concepts taught during previous sessions. Some questions to ask: Ohm's Law: What is the relationship between voltage, current, and resistance according to Ohm's Law? How can we calculate voltage, current, or resistance using Ohm's Law? Series Circuits: What happens to the total resistance in a series circuit? How does the current flow through components in a series circuit? Parallel Circuits: How does the total resistance change in a parallel circuit? How does the current divide among branches in a parallel circuit?
10-12	Instruct the students to solve the numerical problems step by step on their worksheet, encouraging them to show all their calculations and work. Allow the students sufficient time to work on the numerical problems independently. Once the students have completed the worksheet, gather them for a discussion. Go through each problem individually, asking students to share their solutions and explanations.
13-14	Explain the benefits of using a solar charger.
15	Instruct students to complete the exit ticket individually within a specified timeframe. Encourage students to ask any remaining questions or seek clarification on any challenging topics. Share a brief overview of the topics or concepts covered in the next lesson.

Day	2
Question	How to connect solar panels for maximum efficiency?
Objective	Exploring different types of solar panels and how they can be connected.

Summary

It’s Day 2! In this lesson, students will explore the different types of solar panels and will also learn how they can be connected in series or in parallel.

Resource	Description	Copies needed
Slides	Projectable slides for Day 2 lesson.	0 (all digital)
Day 2 Worksheet	Student worksheet	1 per student
Exit ticket	Student exit ticket	1 per student

Detailed lesson plan

Slide	Teaching Moves
2	Welcome students to the class and brief them on the agenda for the day.
3-5	Introduce students to the different types of solar panels. (Monocrystalline and polycrystalline)
6-9	Begin by introducing the topic and explaining the two main types of connections: series and parallel. For the series connection, show a diagram or illustration depicting multiple solar panels connected in series, with the positive terminal of one panel connected to the negative terminal of the next panel. Explain that in a series connection, the voltage of the solar panels adds up, while the current remains the same. Transition to the parallel connection and display a diagram or illustration showing multiple solar panels connected in parallel, with all positive terminals connected together and all negative terminals connected together. Explain that in a parallel connection, the voltage remains the same as that of a single panel, while the current adds up.
10-12	Instruct the students to solve the numerical problems step by step on their worksheet, encouraging them to show all their calculations and work. Allow the students sufficient time to work on the numerical problems independently. Once the students have completed the worksheet, gather them together for a discussion. Go through each problem one by one, asking students to share their solutions and explanations. Encourage students to explain their thought process and reasoning behind their solutions. Clarify any misconceptions or errors that may have arisen during the problem-solving process. Misconception: Solar panels should always be connected in parallel for maximum power output. Explanation: The choice between series and parallel connections depends on the specific requirements and constraints of the solar power system. Both configurations have their advantages and considerations, and the optimal connection depends on factors such as voltage, current, and system design. Misconception: The total power output of a solar charger is solely determined by the number of panels connected. Explanation: The total power output of a solar charger is influenced by various factors, including the efficiency of the panels, solar irradiation levels, and the overall system design. The number of panels alone does not determine the total power output.
13-14	Instruct students to complete the exit ticket individually within a specified timeframe. Encourage students to ask any remaining questions or seek clarification on any topics they found challenging. Share a brief overview of the topics or concepts that will be covered in the next lesson.

Summary

It’s day 3! Students will learn about the design and development of a solar charger. They will also look at different types of solar chargers. Finally, they will plan out what materials to use for their solar chargers.

Resource	Description	Copies needed
Slides for Day 3	For presentation	N/A
Worksheets for Day 3	Student worksheet	1 per group

Detailed Lesson plan

Slide	Teaching Moves
Introduction
2	Share the overview of the lesson for the day (3). Ensure students are seated in their groups of 3-4 per group.
3-5	Begin by introducing the different types of solar chargers the foldable and box type. Some questions that can be asked to students What are the advantages of a foldable solar charger over a box-type charger, and vice versa? In what situations or outdoor activities do you think a foldable solar charger would be more useful? How about a box-type charger? What factors would you consider when choosing between these two types of solar chargers?
6	Invite students to assign roles to each group member, completing Activity 1. If needed, explain that role assignment is helpful to ensure that all group members are equally engaged in the project and that responsibilities are divided amongst all group members.
7	Invite students to complete Activity 2-5 in groups.
8-13	Begin by providing an overview of Tinkercad, highlighting its purpose as a virtual circuit design tool. Instruct students to access Tinkercad on their computers or devices. Guide them through the basic moves and features of Tinkercad, such as dragging and placing components, adjusting sizes, and duplicating. Encourage students to work individually on Tinkercad, allowing them to navigate the platform at their own pace. **Note: Students can watch this video if they need more support on Tinkercad.
14-18	Begin by explaining the purpose of the activity, which is to guide students in designing a 3D model using a step-by-step approach. Introduce the example that will be used to illustrate the design process. Step 1: Construct the base Step 2: Construct the top Step 3: Place the electric components Provide support and guidance as needed, circulating around the classroom to provide individual assistance and feedback. Allocate sufficient time for students to work on their designs, considering the complexity of the example and the skill level of the students.
	How to design a foldable one? Guide students through the following steps for creating a foldable casing in Tinkercad: Start with a base shape: Instruct students to create a rectangular or square shape as the base of the casing. Design the foldable sections: Ask students to add additional shapes or panels that will fold or hinge to allow the casing to fold and unfold. Ensure proper alignment: Guide students to make sure the foldable sections align correctly when folded and unfolded.
19	Brief students on the next day’s plan.

Day	4
Question	How can I create my solar charger?
Objective	Construction of solar charger using electrical parts and recycled material.

Summary

It’s day 4. Students will design and construct solar lamps charger electrical parts and repurposed materials. Students will also get hands on experience with soldering. (Use this presentation for day 4)

Day	5
Question	How can I test and improve my solar charger?
Objective	Students aim to enhance their solar chargers' functionality, efficiency, and effectiveness.

Summary

It’s Day 5! Students will have the opportunity to delve into different methods and strategies to assess the performance of their solar charger prototypes and identify areas for enhancement. By actively engaging in this process, students will develop critical thinking and problem-solving skills while striving to create solar chargers that are efficient, functional, and effective.

External Resources: NA

Resource	Description	Copies needed
Slides	Projectable slides for the Day 5 lesson.	0 (all digital)
Worksheet	Student worksheet	1 per group

Detailed lesson plan

Slide	Teaching Moves
Introduction to Course
2	Introduce the lesson to students. Share the overview of the lesson for the day.
3	Introduce the testing phase to the students. Ask students: How might we test the effectiveness of their solar charger before pushing the design out to mass production? Accept various responses. Break down the difference between quantitative and qualitative indicators used in testing.
4	Share with students the measures that they will be testing the power output, efficiency, portability, and affordability to determine the effectiveness of their solar chargers
Test
5	Brief students on the procedures to test the solar chargers. Guide students to download the necessary applications on their phones. The students must test their solar chargers on power output, efficiency, portability, and affordability. Ask the students to complete Activities 1-4 in their worksheets. Students using ios need only to note the power rating in Activity 1. Some questions that the students might have: Why does the power output fluctuate? Charging Algorithm: Many devices, such as smartphones or laptops, use advanced charging algorithms to optimize charging. These algorithms monitor factors like battery temperature, voltage, and charge level to adjust the charging rate dynamically. Battery Level: When depleted, it can accept a higher charging current, leading to a higher power output from the charger. However, as the battery charges and reaches a higher charge level, the charging current is reduced to avoid overcharging.
Improve
6	Emphasize the importance of critical evaluation and the iterative design process in creating effective solar chargers. Encourage them to record their observations, strengths, and areas for improvement on “Activity 5: Reflections and Improvement.” Based on their findings, ask them to start working on improvements. For the educators To improve power output Increase the Number of Solar Cells: Students can connect multiple solar cells in series or parallel to increase the total power output of their solar charger. Series Connection: Connecting solar panels in series increases the total voltage output while keeping the current constant. Parallel Connection: Connecting solar panels in parallel increases the total current output while keeping the voltage constant. This configuration is useful when charging devices that require a higher current. The power output of solar chargers depends on various factors beyond the series/parallel connection, including solar panel quality, charge controller efficiency, wiring losses, and the overall design of the charging system. To improve portability Compact design: Students can use smaller and lighter by using smaller parts and arranging them in the most efficient way to reduce their overall size and weight. Integrated Carry Handle: Students can incorporate a built-in handle or strap that makes it easy to carry the solar charger, allowing users to transport it comfortably. Durable and Lightweight Materials: Students can use lightweight and durable materials.
	Closing
8	Summarize the solar charger project. Mention that the next project will be the final summative assessment.

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