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“Energy is the only universal currency.”

Vaclav Smil

“Energy is a very subtle concept… very, very difficult to get right… we have no knowledge of what energy is.”

Richard Feynman


Download a 2-page summary: link TK

Energy has been called the “universal currency” (Vaclav Smil) but also “a very subtle concept… very, very difficult to get right” (Richard Feynman). Building on skills developed in physical computing, we will, through generating and measuring electricity, gain a more nuanced and quantitative understanding of energy in various forms. We will turn kinetic and solar energy into electrical energy, store that in batteries and capacitors, and use it to power projects. Several sessions will include hands-on labs. We will develop skills useful in a variety of undertakings, from citizen science to art installations, and address a range of topics through the lens of energy. Students will build a final project using skills learned in the class.


jfeddersen [at] gmail [dot] com Please use this email and not my NYU address as I get this immediately.

Office Hours

Calendar link coming, likely some time on Thursdays and Tuesday immediately after class. In addition to on-floor hours, I’m open to any and all ways to stay in touch through the semester, so email, chat, call, hangout, etc.


  • Develop a broad perspective and nuanced understanding of energy sources and flows.
  • Become well-versed in the current state of the art in energy conversion and storage, as well as relevant near- and far-term technologies.
  • Gain the technical skills necessary to create projects utilizing ambient energy supplies, and to measure and monitor the energy use in those projects. These will include:
    • Understanding energy units
    • Researching and estimating power and energy
    • Measuring power and energy (especially electrical)
    • Circuits for conditioning and storing electrical energy
    • Sourcing energy-related components.
  • Execute exercises and a final project that thoughtfully engage energy concepts.



In a nutshell: you will execute two fast “challenge” projects and a final, lead one class discussion on a topic of your interest, and actively participate in the class each week (readings, discussions, feedback to peers, etc.). 

Consistent Participation / Documentation [25%]

Your active and engaged participation in the course is vital, as is your on-time attendance. Students should not miss class or be late; to do so jeopardizes your grade. Readings and additional materials will be discussed in each class, and you should be prepared and familiar with the topics at hand. Small weekly assignments will be posted each week on the syllabus which will inform in-class activities.

In order to keep current events and student interests in the class, each week a student or students will be assigned to bring in topics for discussion for the following week. We will use 10-15 minutes each class for these discussions.

Documenting the work of this class in an online format is required. At a minimum, presentation materials for your exercises and final should be online by the time they are presented. You may provide additional documentation (e.g. of process, etc.) as you see fit. How/where you put the documentation is up to you, but please provide a single link from which I can access any of your work for this class, and only the work for this class. That means if you’re using a blog, for example, set up a category or tag scheme so there is a single-page archive of all class-related entries.

Kinetic Exercise [15%]

Use kinetic energy to create as much light as possible. Work in teams of 2 to 3. Show work on Week 4. See here for the longer kinetic brief.

Solar Exercise [15%]

Use light to power computation. Work in teams of 2 to 3. Show work in Week 7. A detailed solar project brief will be posted before week 4.

Discussion Leader [10%]

As Smil notes, everything can be analyzed through the lens of energy. Choose a subject of particular interest to you and lead a 10-15 minute discussion in class. Use the Smil text and additional references; provide notes or slides online. Document as much about the energy and power of that system as possible. Directly measure where you can; use research to fill in gaps in measurements; use educated estimates to fill in gaps in research.

  • Cite sources.
  • Place energy and power numbers in perspective, using the SI units we use in class, and
  • Document your topic to serve as a class reference.

Final Project [35%]

Working throughout the semester you will conceive, execute, and present a larger project that directly engages the concepts from the class, accomplishing two or more of the following:

  1. Meet the requirement for “weak sustainability” – a project gets all energy for operation from its users or the surrounding environment (no primary batteries, no plugs).
  2. Quantify its energy usage in terms of input, storage, and output, with efficiencies at each stage.
  3. Use energy concepts as an explicit and essential part of the conceptual underpinnings of the project.
  4. Make a positive difference.

This project will be done individually or in groups of two to three. Details will be provided in the syllabus, and we will collectively develop meaningful constraints for the project at the beginning of the semester.




Reading and Listening

Energy: A Beginner’s Guide
Vaclav Smil
2006, Oneworld Publications
ISBN: 978-1851684526

We’ll be using this excellent text as a the main reading for the course. It provides a wealth of technical detail in a cross-disciplinary context. In the ten years since its publication I’ve found no other text that strikes the same balance. Smil has published a number of other works on the topic. The Beginner’s Guide might be available through the NYU bookstore for about $15. Barnes & Noble and Amazon have it for a less. There are also Kindle and Nook versions.

The Energy Gang
Greentech Media
has become my go-to source for energy news, and their Energy Gang podcast is required listening for the class: please listen to each week’s podcast before the next class, or an archived podcast on weeks off. A journalist, policy expert, and VC interview a guest each week, and regular listening of this will be the fastest way to get up to speed on all issues energy-related.

Also recommended:

Not all blogs are created equal. Consistently-good online sources for energy issues include Vox, Clean Technica, the MIT Technology Review, Bloomberg, and IEEE Spectrum. Less technical “green design” blogs can sometimes be OK, but often write enthusiastically about vaporware.

Sustainable Energy without the Hot Air, David MacKay, e-book. Like the Smil text, this book/site provides a tremendous perspective on energy sources and uses, with even more emphasis on running the numbers and making apples-to-apples comparisons. See also MacKay’s Ted Talk on renewables.

Do The MathTom Murphy, blog. I originally found this in prepping for the 2014 semester. It has a ton of well-written and clearly-reasoned posts grounded in math and physics while taking on the big questions. It’s less active now but remains a great resource.

There will be additional online reading materials assigned throughout the course. Details will be provided in the weekly syllabus.


Other Resources


  • ITP’s Enertiv energy monitoring system (subject to availability – checking in on that). We will look at this in more detail during the class. API access is also available, and would make a good component of a final project.
  • The ER – we have some in house solar equipment.
  • Sustainability wiki – Not much happening here, but could be a place to collect useful info.
  • Physical computing wiki – Since this is in the pcomp area, some info here might be useful.
  • – NYU’s sustainability efforts. See especially the green grants program.
  • NYU/Poly ACRE Clean- Green-tech incubator – home to several energy-related start ups.


Energy Datasets:




Below are some notes on materials that can be useful for this class. Many of these parts you might already have, or be able to find in the junk shelf or via surplus supply online. No materials are required per se, but what you need will vary depending on your projects/solutions.

What I’d get first:

  • DC gearmotor + crank OR Small stepper motor
  • Small solar panel ~5-12V
  • capacitors: 1000uF – 1F or more, 5V minimum
  • Rectifier/Diodes

What I’d get next:

  • Arduino Pro Mini or other low-power micro, plus tools to program (FTDI board or ICP, e.g. TinyISP)
  • DC-DC converter
  • Voltage trigger or monitor ICs (e.g. 1381)

Where to buy: AllElectronics, Electronics Goldmine, and Surplus Center all usually have a variety of DC gearmotors. The first two have other electronics, including solar cells and modules. Adafruit and Sparkfun have battery chargers + cells, DC converters, and some solar as well. Note – the department has a supply of small and medium solar and some other items useful for the class.

Energy converters

DC gearmotors: I think this is the easiest way to convert muscle power into usable electricity for a project. Start with something that’s not too small and not too large (approximately hand-sized is a good idea, 37mm is a common diameter.), 12V-24V. Avoid things with really high gear ratios (and thus low RPMs) – they’ll be too hard to turn. A 1/4” or 6mm shaft is nice.

Note – Brushes and gears will eventually wear out, and not all motors handle being driven backwards well, so this is a bit of a hack, but I think the high current/voltage you can get from this makes it the easiest place to start.

Stepper motors: These are my close #2 choice for motion into electricity. No brushes to wear out, easy to to turn, but output is AC (so will need rectification) and might require higher RPMs to get the power you need. A few steppers have gearboxes built in. Most cranked electronics will be some variation of this – a simplified brushless motor with a gearbox. See Gravity Light, anything from Eton, etc.

Shake light/Faraday flashlight: Strong magnet + big coil + shaking = pulses of electricity. Easy item to find and hack, or make yourself. David Rios and the team of Xuedi Chen, Maria Saba, and Mary Fe did excellent work expanding this concept to some interesting projects.

Solar: Photovoltaics (commonly called solar power) is great – pure DC w/ no moving parts and easy to use. Commercialized by NASA for the space program in the 60s, PV is used extensively on orbit, and in recent years grid-connected solar is seeing massive growth planetside. But for your projects you might need more of it than you think you will, or care to buy – even though prices are falling, it can remain an expensive way to power your work. ITP has a few solar resources in the ER so you can try before you commit.

Possible but harder to use:
Thermocouples/Peltier junctions: These probably need higher temperature gradients than you have to work well. Think stuck between a toaster and an ice cube. Or a small flame and the Alaskan tundra, where they power sensor networks on gas and oil pipelines.

Piezo: Sounds great in theory – a slight motion or stresses on a piezo crystal or film can generate impressive voltages. But usually are very current limited, so very low power. Plus fragile. Putting crystals into shoes, pavement, welcome mats, etc., has been proposed dozens of times, but implementation usually falters. More realistic (and used in the real world) are low power sensors that use high vibration environments like factory machines or bridges.

RF scavenging: Yes, the first crystal radios were powered by the radio waves they received, and fluorescent lights glow near power lines. But while we’re awash in RF energy – AM, FM, Wifi… the inverse square law and the like means the current we can produce from anything more than a few centimeters away is very small (although not unusable – it’s just hard to do and low power).

This is not to be confused with wireless charging, where dedicated resonant coil pairs can transfer significant power wirelessly over short distances. Longer-distance wireless charging is also under development, with complicated targeting and beam-forming, but when it comes, it will at the expense of efficiency.


Batteries: Batteries are awful. Unlike everything else here, they’ll go bad if you don’t use them all the time, their performance is nowhere close to what we’d like to see (what % of your favorite device – volume + weight – is the battery?), they’re not getting better very fast, and they can explode and burn your house down! That said, if you buy a battery, have a specific project in mind for it; trade off weight and cost (lead acid, heavy, cheap – lithium, light expensive; NiMH in between); match the charger or charge circuit to the chemistry and number of cells you are charging; and have a plan to recycle your battery when it inevitably fails. Their are some nice 5V lipo chargers and batteries from Sparkfun and Adafruit that would power small projects and play nicely with solar or muscle-generated electricity. I currently have a limited supply of Voltaic battery packs that combine solar-tolerant charging with lipo chemestry.

Capacitors: These aren’t great either too, but less bad than batteries. They don’t wear out, charge and discharge very fast (power density is high), but are shockingly less energy dense than batteries, and more expensive (although they are improving faster than batteries). A ~1F 5V capacitor is easy to find and can do some interesting things.

That’s about it for electricity, but you can store energy in any number of other ways, such as compressed air, elevated weights, biomass, etc. Small hydrogen fuel cells have become available on the consumer market in recent years.

Other parts

Rectifier and/or diodes: A rectifier is something that converts AC to DC. A bridge rectifier is just four diodes in a convenient package – you can get some or easily breadboard your own.

LDOs: Depending on your project, you might want to take more control over how voltage is regulated for your microcontroller. “Low-drop out” regulators need less of a difference between the input and output voltages, and can be more efficient than a stock 7805 or similar.

DC-DC converters: A “step up” (get it?) from LDOs, DC-DC converters act like mini switching power supplies, and can efficiently step a DC voltage down (buck) or up (boost). So you could run a 3.3 volt micro from a single 1.5V battery. Or take your 7-15 V solar and get 5V for logic without wasting half or more as heat.

Low power MCUs:
If your project doesn’t need all the functionality of an UNO, don’t use one. Arduino Pro Minis use less power in idle (different voltage regulator and no onboard USB), are easily breadboarded, and once you have the FTDI board, are as easy to use as any Arduino. They’re also cheap! Trinkets are also low power, but take a bit of setup and have fewer IO pins. With a little more setup (an inexpensive programmer + small mods to the arduino IDE) you can program the ATTiny chips raw and take control over all the components in your project. Most smaller boards are available in 3.3V versions. Or you could explore entirely different MCU families that might offer better energy performance for your application (e.g. NXP). You can also save power by going slower (8Mhz instead of 16 for example)

Voltage triggers: Used extensively in BEAM circuits, these can cause an action to occur when a capacitor or battery has charged past a certain level. The “classic” Panasonic 1381 is still avialable from Solarbotics; Mouser and other suppliers carry equivalent models from Maxim and ON semiconductor. Search for supervisory circuits in three-lead through-hole packages.



Past Sessions

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