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2012 Energy Syllabus

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Week 1: Introductions

1/23/12

Most of your projects at ITP have an on button and a power supply – they are active energy users. Your projects are possible because computation has become extremely efficient – and abundant and cheap. The things you create may help make technology irresistible, an increasing part of daily life; the consequence of the on button is magnified.

But if you’ve ever smelled that “hot electronics” smell from a frying TIP120 or LM7805, you’ve been closer than most to tackling questions about energy directly. And because of your work at ITP, you are in a good position to understand energy in a precise and nuanced way – an understanding generally all too lacking.

In this first class we begin the adventure of looking at the world – from the scale of an individual electronics project to the scale of the universe – in terms of energy. We introduce (or reintroduce) some of the few terms and units we will rely on throughout the semester: watts, joules, work, power. We’ll meet your new best friends – the first and second laws of thermodynamics.

The first class serves as an introduction to some of the larger themes we will pursue over the course of the semester. We look at the origins of the course and the relevant parts of my background, and hear from you about your experience and expectations.

Reading: 

  • An excerpt from Vaclav Smil’s earlier work: Energies: An Illustrated Guide to the Biosphere and Civilization. 1999, MIT Press, online here [pdf, 2.2mb]
Assignments:
  • Sign up (in class) for leading weekly discussions.
  • Find “converters” for next week’s in-class lab. DC gear head motors, steppers, or (to a lesser extent) piezo crystals are potential candidates.
  • Get the Smil text.
  • Sign up for a shop safety session if you did not take one last semester; and sign up for a shop cleaning time. See the pcomp site for signups.
  • Find your last year of electricity usage from your utility bills (or as far back as you can go). Bring that information to the next class.

Week 2: Kinetic energy

1/30/12

Gossamer Albatros

Gossamer Albatros

We’ll quantify kinetic energy, and see how it is converted into electricity (accounting for almost all of the world’s electricity generation).

 

Energy is either waiting to happen – potential – or is happening. When you look closely enough, everything happening is kinetic energy –  things in motion. Sometimes we can’t look closely enough, so we invent terms like “heat” or “sound”, which are names for patterns of kinetic activity too small and complex to observe directly.

In our pendulum experiments last week, we saw the almost perfect oscillation between potential energy and kinetic energy and back, but also observed energy leaving our system to its surroundings at a slow rate. We were introduced to the SI unit for energy and work – the joule – and its definition as force through distance (1 joule = 1 newton * 1 meter). A newton is a unit of force, defined as a that force necessary to accelerate a kilogram by 1 meter per second each second. If we lift an object, we do work moving its mass against the acceleration of gravity (9.8 m/s/s), and thus store energy in the elevated mass. A review of all this is found in Kinetic Energy 2012 (pdf).

This week we’ll take a whirlwind tour of energy throughout the history of the universe, and arrive at some of history’s first useful “heat engines”, devices for turning the stored chemical energy of fuels into heat, and from heat into motion. The proliferation of these devices has shaped our modern world. We’ll also look at electromagnetic induction, the phenomenon exploited by electrical generators, by which moving current can induce a physical force and vice versa. Heat engines alone or as the input for generators account for a huge slice of our (non-food) energy use.

To really get induction, we need to have a good understanding of the dual nature of electricity/magnetism. About the best, and most fun, reference I’ve found is this entry in the excellent Cartoon Guide to Physics by Larry Gonick and Art Huffman. Buy it! Note in particular how Lenz’ law relates to the conservation of energy. MIT created a series of applets and videos that help visualize this relationship that we’ll look at in class.

For our purposes, just about any motor is a ready-made generator. We’ll try some out, look at the basic circuits needed to condition their output (rectification via diodes, maybe a little smoothing with capacitors, maybe regulation), and try to assess their electrical performance.

Materials used in class:

Reading:

Assignments:
  • If not finished in class, measure the open-circuit voltage and short-circuit current of your converters. Put together a circuit that powers a small load, such as an LED. If necessary, use rectification, smoothing capacitors, and voltage regulation.
  • Finalize your midterm concepts and be prepared to discuss them next week in class. Identify components you think you might need and where to get them.

Week 3: Small solar

02/06/12

We’ll see how solar panels work and use small ones in simple circuits.

Last week we saw what a central role heat and heat engines play in planetary energy flows. Looking at Lawrence Livermore Lab’s analysis of US energy use, we saw that most of our energy use is either direct combustion of fossil fuels (for transportation), or using fuels as a heat source for thermal electricity plants. (Fuels, especially natural gas, are also used directly for space heating and industrial processes).

The electrification pathway is significant. The California Council on Science and Technology looked into the feasibility of reaching the state’s goal of reducing emissions to 80% below 1990 levels. The study included two significant points: 1) as much as possible California’s economy and energy use would need to become electrified, including space heating and transportation, and 2) that that electricity generation would have to be de-carbonized.

The carbon-neutral electricity generation methods available to us pose different problems. Large scale hydro electricity is already developed in many of the places it could be used, and in any event comes with an environmental footprint that is not immediately obvious. Wind power has seen intense recent development in the US thanks to the 1603 Treasury Grant Program providing production tax credits for wind power, but that program is set to expire at the end of 2012, and this has already affected plans for new turbines. The gargantuan megawatt turbines that are the most cost-effective also face aesthetic opposition in some prime wind areas. To date, no one has solved the problem of storing the by-products of nuclear electricity production, and the recent Japanese tsunami and subsequent Fukashima Daiichi crisis have shown the difficulty of securing nuclear facilities from unforeseen events.

All these methods of electrification are also somewhat indirect. A nuclear plant is a coal plant with a different hot side; wind and hydro electricity rely on the sun to drive the water cycle and energize the wind. But electricity can be generated directly from the sun. This is done via photovoltaic (PV) materials – materials that produce an electrical potential when exposed to light.

Solar works! Our modern world would not be the same without our solar-powered communication satellites, and PV is the only power supply that could operate reliably and for long durations in the extreme and remote environment of earth orbit. PV also works closer to home, powering equipment wherever grid electrification is infeasible. The proliferation of battery-powered mobile devices and mobile lifestyles has been accompanied by increasing interest in PV for consumer products. With silent operation and no moving parts, PV is the ultimate long term technology, and, contrary to some beliefs, becomes energy-positive within four years. This, combined with it’s attractive carbon profile, has resulted in global installed PV increasing exponentially in recent years. Recent drastic fluctuations in the cost of electronics-grade silicon (from $400/kg to less than $40 since 2008) and the unprecedented scale of Chinese solar manufacturing coming online make this an interesting moment for solar.

We’ll get our hands on some PV materials this week, measure their performance, and power some small circuits with PV.

Class materials:

Previous class projects of note:

Discussion:

  • Sean McIntyre, Solar powered sensor networks or energy analysis of two or three off-the-grid communities.

Reading:

  • Smil, Energy, a Beginner’s Guide Chapter 3
Assignments:
  • Create a schematic functional diagram (lines and boxes) of your midterm to present in class next week, create a one-line functional description, and give your project a name. Publish the info to your documentation site prior to class.
Link:

Week 4:  Useful connections

02/13/12

The bulk of this class will be given to catching up with hands-on time with materials such as solar panels, generators, and related peripherals. We’ll start with solar, including a review of what the department has available to you. We’ll quantify the output of panels under different lighting conditions by measuring the open circuit voltage and short circuit current, and we’ll power test loads.

We’ll charge up some capacitors and see how they can play a role in at least smoothing the (usually variable) output of our energy converters. Much larger capacitors – on the order of a farad or more – can be used as battery replacement (low energy density, very high power density, and high cost).

We’ll also look at two methods for providing a steady voltage for our loads – simple linear voltage regulators such as the LM7805, and more efficient and flexible (and expensive and harder to source) step-up or step-down DC to DC converters.

Finally, we’ll talk overall strategy for thinking about energy projects. We’ll approach the problem from a few different angles. For example, we can think generally about the kinds of energy conversions we are using. While we’ve focused particularly on the kinetic- and solar-to-electrical conversion pathways, we’ll remember that in fact there are many others, and we’ll take a second look at Smil’s conversion grid. We’ll think in terms of available inputs (Smil again, and Paradiso) – if you needed a 20W power source, what are your options? What about 5W? 100? We’ll discuss measuring or at least approximating a load – if we want to run a computer, or a phone, or an arduino, how much power do we need? And how would you know when to use any of the tech bits (regulators, smoothing capacitors, etc.) we’ve seen in class? We’ll look at a decision tree for sorting that out.

(As came in Sean’s discussion last week, there are packages available for energy harvesting that could simplify this design process for some very-low-energy projects – usually they’re geared towards the kinds of distributed sensor networks we saw last week. The department should have some if they can be found. Here’s a write up by a former student.)

And of course, we’ll see your midterm schematic drawings, hear the one line descriptions, and learn your projects’ names.

Discussion:

  • NA
Reading:

Editorial Sidenote: Energy harvesting is real, and used correctly, even otherwise “lost” energy such as braking muscle force can be recovered, enabling devices that are assistive and unobtrusive. The kneegen project above is an excellent example, with sound physics and a noble motivation.

But every year around this time, we get a fresh crop of CES energy harvesting demos pitched to the greedier goal of getting a little more talk time out of our phones. Invariably the device is a prototype, the numbers are vague (“It’s just like using your wall charger!”, “About $20!”, “Available by the end of the year!” ), and there’s a something-for-nothing thermodynamics-be-damned smell. This is aided and abetted by tech journalists’ apparent willingness to believe in anything when it comes to energy. There’s a reason you can’t find RCA’s Airnergy charger today, and it’s not because it wasn’t blogged about enough. This take down explains it pretty well.

This year we get nVolution’s nVolt. It’s not that the device couldn’t work somehow – we know that kinetic energy can get you electricity. But the effortless spinning by the pitchman is a give away – no energy in means none out, and no matter how much rotational inertia the spinning object has, none (or very very little) was being converted to electricity at CES. To his credit, he does say the system works by magic, and as soon as he mentions capacitors, the journalist moves on to what colors will be available.

Presidents Day 02/20/12 – NO CLASS!


Week 5: Limits

02/27/12

We’ll look at fundamental limits to how useful energy can be to us. These concepts won’t help you build anything, but are part of being energy literate.

Discussion:

  • Monica Bate

Week 6: Midterm projects

03/05/12

 

Spring Break 03/12/12 – NO CLASS!

 

Week 7: Big kinetic – wind

03/19/12

Discussion:

  • Ingrid Gabor, Sophie Laffont

Week 8: Big solar – field trip

03/26/12 

Discussion:

Week 9: Guest crits; special topics

04/02/12

Discussion:

  • Guiherme Costa, Danne Woo

Week 10: Monitoring, horizons, special topics

04/09/12

Discussion:

  • TBD

Week 11: Workshop

04/16/12

Discussion:

  • Sam Galison, chemical reactions (e.g. potato clock), tesla, resonant frequencies

Week 12: Final Presentations

04/23/12