In this issue:
Every morning the sun rises, bringing light and heat to the earth, and every evening it sets. It seems so commonplace that we rarely spare a thought for that bright object in the sky. Yet without it, we wouldn't exist!
Deep in the core of our local star, hydrogen atoms react by nuclear fusion, producing a massive amount of energy that streams in all directions at the speed of light (that's the mind-boggling speed of more than 186,000 miles per second). In just eight minutes, that energy travels 93 million miles to earth.
We use many different forms of energy here on earth, but here's the thing: almost all of them originate with the sun, not just light and heat (thermal) energy! The law of conservation of energy says that energy can't be created or destroyed, but can change its form. And that's what happens with energy from the sun —it changes into lots of different forms:
The sun sends more energy to the earth in one hour than the whole planet needs in a year. Imagine if we could capture that energy directly and convert it to a form that could power our cities, homes, and cars! Many scientists around the world are researching how we can improve our use of the sun's energy. One way is to use solar thermal panels to collect thermal energy to heat air and water. Another way is to use photovoltaic (PV) cells, also called solar cells, to convert sunlight directly into electricity. ('Photovoltaic' essentially means 'light electricity'.)
PV cells use a material such as silicon to absorb energy from sunlight. The sunlight energy causes some electrons to break free from the silicon atoms in the cell. Because of how the solar cell is made, these free electrons move to one side of the cell, creating a negative charge and leaving a positive charge on the other side. When the cell is hooked up in a circuit with wires, the electrons will flow through the wires from the negative side to the positive side, just like a battery. This electron flow is electricity, and it will power a load (light bulb, motor, etc.) you connect to its path.
PV cells today are still only able to capture a small fraction of the sun's energy, so acres of them are necessary to collect enough light to create electricity on a large scale. A lot more scientific work needs to be done to make them more efficient and take up less space. Despite the challenges, solar panels are used to power many things such as emergency signs, school crossing lights, and more. Many people are also able to power their homes by mounting solar panels on the roof, and this will only get easier as the technology continues to advance.
We may never drive cars covered in photovoltaic cells, but building a miniature solar car is a fun way to see how solar energy can be used for power. In this project you will need creativity and experimentation to design and build a car powered by two solar cells and a small electric motor. Get some design ideas from the pictures on this website. The National Renewable Energy Laboratory has a PDF curriculum that will also give you ideas and help you learn about the scientific and engineering principles behind building a solar car.
Designing and building a car from scratch involves a lot of perseverance and trial and error, so don't be discouraged if yours doesn't work perfectly right away. Experiment to see if you can improve the design of your solar car. How fast does it go? Does it drive straight? How would it perform with only one solar cell? What if you used smoother wheels for less friction? Keep testing new ideas to make your car work better.
Once you've perfected your car, think about other ways you could experiment with solar power. Could you build a solar boat or water pump? Could you perform electrolysis to divide water into hydrogen and oxygen using a solar panel? How can we harness the amazing power of the sun? Maybe you'll be the next scientist to help find out!
For more solar science fun, check out these projects:
On Tuesday, July 22, 2008, Continuum finished its 2400 mile journey from Plano, Texas to Calgary, Alberta. This solar-powered car built by students from the University of Michigan won the 2008 North American Solar Challenge using only power from the sun! The Challenge is a competition for college students to design, build, and drive solar-powered cars in a cross-country race. This year teams competed from universities in the US, Canada, England, and Germany.
After months of hard work designing, building, and testing their futuristic-looking solar cars, nearly two dozen teams arrived in Texas for a week of 'scrutineering.' During scrutineering each car goes through multiple checkpoints that evaluate its solar array and its electrical, battery, and mechanical systems, among others, to make sure it meets regulations and safety standards. After passing through all checkpoints, each driver must complete a certain number of laps around a track in order to qualify for the race. There's a lot of engineering in action during scrutineering week, as teams creatively make adjustments and fix problems on their cars in order to pass the checkpoints.
The 15 teams who qualified started their journey to Calgary on July 13th, traveling at times through challenging clouds and rain, thankful for the scheduled stage stops and a chance to point their solar arrays at the sun to recharge their batteries. Repairs were made on the run, often with tools borrowed from other teams. After ten days and four stage stops, the teams rolled into Calgary for the finish.
Though the future of alternative energy cars isn't solar cars like the Continuum, the North American Solar Challenge is a great opportunity for developing new engineers and scientists who may go on to design even better energy solutions. The Challenge also demonstr3ates the potential of the sun - it can power a car on a 2400 mile journey even with fairly inefficient photovoltaic cells. Most likely, solar power will play a part in the future of transportation, perhaps by collecting sun on your garage roof to charge the batteries of your electric car.
Check out this video to see some of the solar cars in action during the race! Fabulous Facts
Long-Distance Light: A bright light bulb can provide enough power to a solar cell to run a small motor, but only if the solar cell is a few inches from the bulb. Even though the sun is 93 million miles away, it provides more power to a solar cell than a light bulb less than a foot away!
Hairdryer on the Highway: The solar arrays that power the cars in the North American Solar Challenge produce only as much power as a typical hairdryer! (About 1000-1800 watts.)
Solar-Powered Space: Solar cells were originally developed in the 1950s for use in the space program. Satellites and the international space station are powered with solar cells.
Learn how solar cars work in this video interview with a student from the University of Michigan solar car team.
Watch Missouri S&T's solar car travel around the track before the start of the 2008 North American Solar Challenge.
Explore our local star with this animated introduction to the sun (requires Flash).