Solar
The second challenge in this course is: power computation with light.
Due: Week 7, March 7th.
Background
LEDs are pretty forgiving loads – they can turn just a few electrons into pleasing photons, and they’re cheap enough that if you break them it’s no huge loss. Powering them with a kinetic source – especially a human-powered generator – provides abundant electricity with easy-to-find parts and puts you in control of the energy. Need more? Crank harder.
For this assignment both components – the source and the load – become more complex. For the source, we’ll use solar, or more specifically, photovoltaics – materials that turn light into electricity. This isn’t new stuff – one of Einstein’s early papers on the photoelectric effect laid the foundations for quantum mechanics – but in recent years solar has achieved a scale in manufacturing and deployment that allows it to compete with any legacy energy supply.
But solar, at the grid scale or in our personal projects, doesn’t have the ability to dispatch energy whenever we need it. We can seek out sunlight, but if it’s not sunny, we’re stuck. So we need to add some kind of storage, which allows us to take a fluctuating input and provide a steady output. This could be many things, but we’ll do this with lithium-chemistry batteries. This year ITP is providing a kit to provide the basic solar/battery foundation, allowing you to focus on applications.
For that application, I’ve merely specified “computation”. I leave this to you to define as creatively or straightforwardly as you like, but at a minimum this is a higher bar than merely powering a passive load like an LED. You’ll have to provide a stable basis for a something to power up and run code you write. You’ll need to consider the power implications of any sensors, outputs, or networking you add to your project. And above all, you’ll need to try to live with – to really use – the device you create. Document your project in situ, because it will be difficult to demo them in doors. In week 8 you’ll present the project and the documentation.
Kinetic
The course begins with a three-week kinetic challenge: turn motion into light.
Due: Week 4, February 14.
Background
For as long as electricity has been more-or-less sorted out, people have been proposing things like shoe-generators and door-generators and fill-in-the-blank generators attached to anything you can imagine, in the name of capturing “lost” energy. This is one of those old ideas that perennially pops up in new clothes.
Today we have a few pretty humble products that do just that – think the Eton emergency radios, etc. – along with a swarm of Kickstarter-esque products that combine what is, in almost all cases, exactly the same technology as a shake light or crank radio, with slick design and big promises. The creators are either unaware of basic energy concepts, or hope you are. See for example here.
(There are occasionally innovations in this field. One is capturing negative work: when we use our muscles against a motion. Think descending stairs, or slowing down our leg as it swings forward when we walk. It takes a lot more ingenuity to engage an energy-capture device only when it is capturing negative work; but if done correctly, such devices could capture energy while reducing the user’s effort.)
There are not so many ways to generate electricity, and until we’re all cyborgs, there are well-understood biological limits to our human machinery (machinery that, by the way, doesn’t generally tolerate a lot of energy going to waste anyway). It doesn’t seem to me there are too many novel ways to generate electricity with muscles. So why are we doing it for our first assignment, you may ask?
There are two reasons: first, becoming a human generator is one of the best ways I know of to improve your understanding of how energy fundamentally feels, and along the way gain intuition about electricity and mechanisms. Electromagnetic induction is the way virtually all of our electricity is generated.
Second, while the energy reasonably available from a human is small, what can be done with that energy is rapidly expanding. Our phones – super computers of a previous generation – run at about 1 watt, or 1/100th the power of a human body; sensors shrink and as they do take permanent place in our infrastructure and on our bodies; LEDs squeeze more illumination from less energy every year. As our technology becomes more ephemeral, previously impractical energy sources become interesting.
We begin with LEDs because they are forgiving and efficient loads. However, I must note that too many projects use lighting up an LED as a kind of proof-of-concept and never move beyond that phase. Beware projects that only light up LEDs.
So, your first challenge is to turn motion into light.
Tips – tap big motions (from big muscles), use good lights (high efficiency LEDs). Since the projects will be reviewed on Valentine’s Day, bonus points for red/pink lights.