Clearly energy is an important topic. We all like to live with stuff that uses energy: driving, computers, the internet, lights, heating and cooling. So, where does all our energy come from? First an important note. What do I mean by “come from”? We always see energy being conserved. This means that the total energy before something happens is the same as the total energy after something happens. Suppose I drop a ball of clay onto the ground and it goes “splat”. Right before it hits the ground, the ball has kinetic energy. However, after the “splat” the ball is stopped. The total energy is still the same, it is just in a different form. In this case, the clay changed shaped, warmed up and the collision made a sound. If you could measure all of these values, you would see it is the same as the initial kinetic energy. So, let me look at some of the common power production sources (see, I just implied that the energy is produced – which it isn’t). Solar There are a couple of ways solar energy can work. The common method is a device that produces an electric potential difference when light hits it – you know, solar panels? There are other ways to use solar energy though. One such way takes mirrors and focuses the sunlight to a particular point (like a solar oven). At this point, you can increase the temperature of something and use that to generate electricity in a similar manner to fossil fuel power (see below). So, where does this solar energy come from? For now, let me just say “the Sun”. Duh.

Wind One of the easiest ways of generating electricity is to rotate a coil of wire in a magnetic field. If you would like to know more about magnets and generators – these demos might be useful. For the wind generator, it seems clear that the wind pushes these fan blades to make them turn. This then powers a normal electrical magnetic-coil generator. Great, but where does the energy in the wind come from? The Sun. The thing is that the Sun warms up different parts of the Earth at different rates. This means that the air is warmer at different parts of the Earth. When you have air of different temperatures, it starts to move around. Oh sure – this isn’t the best explanation of wind. It is just a simple one. Also, there are other things that influence the wind – such as the rotation of the Earth and land features. However, I think it is safe to say that mostly the energy from the wind comes from the Sun.

Fossil Fuels Take some stuff. Burn it. Poof, you get some energy (thermal energy). That is the basic idea behind fossil fuels. What do you do with the thermal energy? You boil water. That makes steam. The steam can then turn a turbine that turns a coil-magnet system just like the wind generator. The real question: why does burning fossil fuels give you energy? How about I say that in the burning process, chemical bonds are broken in such a way that you get energy. There are lots of things you can burn to get energy – like food or wood. Fossil fuels are essentially the same thing, just old. Real old. Fossil old. Get it? And where do the fossil fuels (as well as food and stuff) get the energy for their chemical bonds? Yep. The Sun. So basically, fossil fuels are stored energy from the Sun long ago. Some people like to say that fossil fuels are not renewable energies. In the short term, they are correct. But if you wait long enough (really really really long time) there will be more fossil fuels from the plants that we have today.

Hydroelectric Yes. That is a diagram of a dam. Really. How does a hydroelectric dam work? It is very similar to the wind generator and the fossil fuel plant in that it produces electricity by turning a coil in a magnetic field. In this case the coil is turned from water flowing over turbine-type thing. So, falling water instead of rising steam. Since the falling water turns the generator, does this mean gravity is the source of energy? Not really. Think about it this way, if gravity was the energy source, wouldn’t there have to be less gravitational energy at the end? You could argue your point by saying there is a decrease in gravitational potential energy and I would probably let you win. However, the hydroelectric dam keeps running because it has an essentially endless supply of falling water. But where does this water come from? There actually isn’t an endless supply of water – it just seems that way because the water from the lower parts moves to the higher part. We call this rain. And how does the rain get up in the sky? Yep. The Sun. The Sun gives enough energy to water to make it evaporate. Ok. Let me pause for a moment and draw a diagram of the energies listed above. Yes. The Sun is the Kevin Bacon of energy sources. Oh, there is more than the Sun you say? Where does the Sun get its energy? Yes, there is more. So let me look at some energies that don’t lead back to the Sun.

Geothermal The center of the Earth is hot. Super hot. The basic idea behind a geothermal plant is to use this thermal energy in the Earth to somehow make steam (you can do this even if the part of the Earth is less that 100 Celsius). The steam is then used to turn a turbine and your basic coil-magnet generator. But where does this thermal energy in the Earth come from? Global warming. No, I am kidding. The interior of the Earth is warm mostly due to gravitational potential energy. Basically, the stuff that formed the Earth was gravitationally attracted and kind of “fell” together. When they collided, they got warmer. There are other contributing factors to the interior temperature of the Earth, but I think this is the biggest one. Why was this pre-Earth stuff separated to begin with? Most of the material in our solar system is the left over material from a previous star. That star exploded, and now we have what we have on Earth. I guess you could call this geothermal energy a product of some previous star.

Nuclear Fission If you take some heavier elements (like uranium) and break the nucleus into two (or more) pieces, you get energy. Why? One simple explanation is that the the mass of the pieces is less than the mass of the original particle. Einstein’s famous expression E = mc2. This says that mass is related to energy. Really, it is much more complicated than that – but you get the idea. If you get energy from breaking this nucleus apart, where did the energy in the nucleus came from? How do you get uranium anyway? It takes energy to make uranium. The energy for this creation also comes from an exploding star.