Use of solar energy- design and construct solar cookers, solar panels, etc.

Introduction: (Initial Observation)

Energy is an inseparable part of our lives. Energy provides for our basic survival and gives shape to our aspirations and dreams. Our resources of energy, like fossil fuel reserves and natural gas, are decreasing day by day; while at the same time, the demand for energy in our country and across the globe is increasing. Therefore, it is extremely important to understand, develop and explore other forms of energy resources.

Renewable energy resources like the sun and wind play a major role in the development of a sustainable future. The younger generation, especially, have to understand that the issue of energy has a major impact on their future lives. For this reason, there is a great need for education about renewable energy options, such as solar energy. As well, many of the environmental concerns of the earth are due to pollution from the burning of fossil fuels. The “Greenhouse Effect” is an important example of an environmental problem caused by pollution.

Solar energy is an excellent form of renewable energy available to us, today. The objective of this project is to identify and examine different ways that solar energy can be integrated as a part of our everyday lives.

Also Click Here to see another version of this project.

Information Gathering:

Find out about Solar Energy. Read books, magazines or ask professionals who might know in order to learn about different ways that solar energy can be collected, stored and used. Keep track of where you got your information from.

Select your project and make a project plan:

Solar energy can be the subject of many different experimental and engineering projects. You cannot mix all these subjects in one science project. You must select your focus and skip additional or unrelated experiments that are suggested in this project guide. Please note that engineering projects aim on design and construction of a working machine or a system while experimental projects study the factors that affect functionality of such systems.

Samples of engineering projects related to solar energy:

1. 1. Design and construct a solar cooker
   2. Design and construct a solar hot water heater
   3. Design and construct a photovoltaic cell

Note that engineering projects do not require question, hypothesis, and experiments using the scientific method. As a result, they will not have a data table, charts, graphs and conclusions.

Samples of experimental projects related to solar energy are:

1. 1. How does the angle of sunlight affect the amount of solar energy delivered to a flat horizontal surface?
   2. How does the angle of a solar panel affect the amount of solar energy that can be collected.
   3. How does the color of a solar panel affect the amount of solar energy that can be collected.

Please read the following information and then select an specific subject for your engineering or experimental project.

Solar Heating

Solar heating starts with solar collectors which are divided into two basic groups:
flat plate and focusing collectors. The flat plate collector absorbs the sun’s energy and converts it into heat, while the focusing collector concentrates the sunlight either by reflecting or refracting to achieve higher temperatures.

Solar Cookers

Cooking with the sun can be fun by building your own solar cooker. A solar box cooker works on the same principle as all solar heating systems; by absorbing the sun’s radiant energy directly through glazed surfaces, or indirectly from reflectors.

A solar cooker usually consists of a well-insulated box for storing energy, a glazing surface of plastic or glass for collecting energy, and reflectors, like aluminum foil or
a mirror, to increase the amount of heat energy collected. To increase the absorption of the solar radiation, the box is painted a dark color on the inside. Solar absorption can also be increased by using dark-colored pots for cooking.

What is glazing surface?

The pipe or the tank that is receiving heat is usually painted black or any other dark color. Dark colors will collect the most heat. Part of this heat may tend to exit in the form of radiation. To prevent heat loss in the form of radiation, the black surface is covered with a clear coating called glaze. Glaze may be made of plastic (polymers) or glass. (Most ceramic and china products are glazed in order to have a smooth shiny surface.)

You are strongly encouraged to design your own solar cooker by using the instructions described in this page. Try different material and design options and, using the testing procedure, determine why they increased or decreased the cooker performance.

Solar Water Heaters

Solar water heating is an important area for renewable energy development. Heating water is one of the basic needs in our everyday life. Solar hot water systems can be used to heat swimming pools and to provide hot water in homes and industry. You are strongly urged to design your own models by using the one given below as an example.

Solar Electricity

Solar energy can be converted directly into electricity, which can then be used in many applications such as powering houses, offices, satellites, solar cars and charging batteries. Because fuel is not burned while using solar energy, pollution is eliminated. A photovoltaic cell is the basic component of a solar electric system.

A photovoltaic cell is made up of thin semiconductor material, like silicon wafers. The actual silicon wafer is negatively charged. When light shines upon it, photons strike the solar cell and electrons are knocked loose from the deeper layer to the surface layer from the atoms in the semiconductor material. The electrons can be captured in the form of an electric current by attaching the positive and negative wires from the photovoltaic panel to your application.

The power or wattage of the electric current is determined by the equation: Power (watts) = Voltage (volts) x Current (amperes). Voltage is the potential or pressure of the electricity being produced, and current is the rate of flow of the electrons. Current is measured in Amperes.

Individual silicon-based PV cells have a characteristic potential of about half a volt. The amount of current delivered by a cell is directly proportional to the intensity of light (the number of photons arriving per unit area per unit time). In bright noon sunshine, the solar cell listed in this activity produces approximately 1.5 watts of electricity.

Shadows and angle of incidence are important factors affecting the intensity of light. On a cloudy day, the rate of arrival of photons is greatly reduced. The light intensity is also affected by the angle of incidence of light striking the surface of the solar cell. By adjusting the angle of the cell so that it faces the sun directly, the light intensity can be increased.

A number of solar cells can be connected together to form a module. The cells can be connected in series or parallel arrangements, to achieve the required combination of current and voltage. To produce more voltage, the cells are connected in series and, to produce more current, the cells are connected in parallel.

The photovoltaic modules produce direct current (DC) electricity. By using a voltmeter or millimeter, the electric output of the cell can be measured directly.

Solar Cars

Powering a car with solar energy is one of many rapidly developing ideas for using alternative forms of energy. A panel of solar cells, instead of gasoline, is used to run the car. An electrical charge generated from the solar panel is stored in a battery; this stored energy is used for driving the vehicle. Energy can be stored and drawn from batteries at night or on cloudy days.

This following activity will illustrate various concepts such as speed, friction, inertia, gravity, momentum and drive and propulsion mechanisms. It also gives the experience of using hand tools for different applications. The basic materials required for building a solar car include:

• • A solar panel for generating power to run the car. Make sure that no shadows from the mounting material fall on the solar cell.
  • A small DC electric motor to transfer the generated power to the propulsion system.
  • A lightweight material, such as balsa wood or foam core, for the body of the car and mounting the solar cell. Use materials that are light and easy to work with. The weight is a very important factor to be considered when designing and building a solar car. Small solar cells do not provide enough power to move heavy car bodies.
  • Aerodynamics is also an important factor while building a car. Crosswinds, drag and other forces that act on the body of the car when it is in motion have to be considered while designing the body of the car.
  • Propulsion system for rotating the wheels. Options include a system of pulleys and rubber bands, or gears, or a propeller. The electric motor transfers the power generated by the solar panel to the propulsion system, which is then used to rotate the wheels.
  • Wheels and axles. You can use parts from old toys or car kits. Use your imagination and find materials around the house. Make sure that there is minimum rolling resistance by choosing the right kind of material for the wheels and watch the wheel alignment. Take care to reduce friction as much as possible. Think of ways to attach the wheel assembly to the car body. For example—using a straw with the axle running through it. Wheels are connected to the axle and the straw can then be glued to the body of the car.

Solar car kits are available from companies like Kelvin Electronics or Fisher Scientific. These kits provide you with the basic materials required for a solar car.

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to construct a solar cooker and determine how does the amount of available (or collected) energy change in different hours of the day.

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

Independent variable is the time of the day.

Dependent variable is the amount of available (or collected) energy

Controlled variables are weather temperature and wind

Constants are the size, design, location and orientation of our solar cooker. To keep the orientation a constant, either do not change the orientation in different times of the day or continuously change it to be faced to the sun. In the first example orientation is constant in relation to the earth. In the second example it is constant in relation to the sun.

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

Following are two sample hypothesis:

1. 1. My hypothesis is that the amount of solar energy varies in different times of the day. I expect to get the highest amount of energy at noon time.
   2. My hypothesis is that the amount of available solar energy will remain constant as long as sunlight is available and our solar cooker is faced to the sun.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Procedure to make a solar cooker

1. 1. Cut down the cardboard boxes so that the smaller box fits inside the larger one.
   2. Paint the inside of the small box black, for greater heat absorption.
   3. Insulate the box on the bottom and sides by placing insulating material in the gap between the two boxes. (Common insulation materials include Styrofoam boards, polyurethane boards, mineral wood boards, fiberglass boards.)
   4. Cut a large hole in the cover of the larger box. Cover the hole with plastic food wrap or place glass in the cut-out portion. The escape of longer wavelengths of heat energy is prevented by the glazing.
   5. Glue the tin foil or mirror to a big piece of recycled corrugated cardboard. It should be approximately the same size as the cover of the box.
   6. Hinge the reflector to the box with tape.
   7. Hold up the reflector with the help of props and string (see Figure 1).

Figure 1. Solar Cooker

Using the Solar Cooker

Place the solar cooker facing the sun without any shade falling over it. Move the box until the shadow of the prop falls directly behind, parallel to the edge of the box. Adjust the position of the reflector, until the reflected sunlight lights up the inside bottom and front of the solar cooker. Tighten the strings in this position and adjust the props to hold the reflector in this position.

Use dark-colored cookware for cooking. This helps increase the heat absorption. This solar cooker should be able to reach temperatures between 200º and 300º F. Place a thermometer inside to read the temperature. Preheat the cooker for about half an hour.

Testing Procedure

1. 1. Place your solar cooker in the sun.
   2. Use an oven thermometer and record the temperature at regular time periods (e.g. every 5 minutes).
   3. Calculate the amount of heat energy gained in one hour by using the formula:

Repeat the experiment once every hour from the sunrise to the sunset (or as long as you can. Record your results in a table like this:

Listed below are some interesting variations that you can experiment with to find out which cooker design results in the highest temperature. Determine the reason why the changes increased or decreased the performance of the cooker.

Other experimental Options

• Use only one box lined with foil-faced insulated sheathing inside.
• Paint the inside of the foil-faced sheathing black.
• Use glass instead of plastic wrap for the glazing.
• Use Plexiglas instead of plastic wrap.
• Try using the cooker without a reflector.

Precautions

Be sure the cookware is fully covered; otherwise, the escaping moisture will condense on the glass and block the sunlight. Be careful when removing food from the cooker. It’s hot inside!

Additional Experiments:

Materials and Equipment:

Materials Required for Solar Cooker

• • Two cardboard boxes with covers (e.g. copy paper box, packing box, cardboard file boxes)
  • Insulation for the box (e.g. fiberglass insulation, foam insulated sheathing, or other kind of insulation)
  • Reflecting mirror-like material or tin foil, for reflector, and corrugated cardboard
  • Glass, Plexiglas or plastic food wrap
  • Sticks for props
  • Scissors and tape
  • Black paint
  • String or cord

Materials Required for Solar Battery Charger

• • Silicon Solar Cells (3)
  • Two “AA” rechargeable batteries
  • 2 Single Battery Holders for “AA” battery
  • Wire for connecting the cells and holder (preferably #26 gauge or less)
  • Small soldering iron (less then 50 watts)
  • Solder material (e.g. Rosin Core solder)
  • Flat board for mounting the cells and battery holder (e.g. perfboard)
  • Self-sticking fasteners like Velcro

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Calculations:

Description

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

Visit your local library and find books about solar energy. If you need to do more search on the Internet, in addition to solar energy you may search for solar panels and solar cells.