An Introduction to Sustainable Energy Systems
As individuals, we most often focus upon a single energy technology: One we particularly like (e.g., solar or wind), or one we particularly dislike (e.g., fossil fuel or nuclear).
And then we all start arguing.
At Bell Labs I researched semiconductor devices for fiber optic communications. These were kissing cousins to solar cells, and I got to know a lot of people in the solar cell field (including the founders of two U.S. solar energy companies). So, naturally, for me, that "single energy technology" was solar cells. But for years, my friends told me that "when the cost of cells falls below $X.YZ / Watt, they will take over the world!" And then they fell below that cost. And they did not take over the world. I was clearly missing something. So I began reading almost every article, paper and book on energy I could find. And I eventually figured out what I'd missed: Sustainable energy is not just about the component technologies, it's about how they fit together to create a complete energy system. Put another way, the individual technologies are only pieces of a much larger puzzle. And, frustratingly, many of those pieces still have shapes that are blurred, ill-defined, and/or changing with time.
But why not build an energy system based on just one "piece," for instance solar cells? Because, for now, no single "piece" can affordably produce the amount of energy we need, when we need it. To illustrate, say that solar cell efficiencies suddenly skyrocketed, and costs plummeted. Wouldn't that make an all-solar energy system possible? Yes, but only if you were willing to spend your evenings in the dark, either shivering or sweating. The problem? Solar cells require intense sunlight to produce energy, which only happens (with luck) near midday. But our power consumption peaks in the evenings. So for a solar-based energy system to work, we would also need an effective and affordable way of storing huge quantities of midday energy for many hours - a technology "piece" we do not yet have. Or, if you lived on the U.S. east coast, you might tap into solar cells on the west coast, where the solar peak comes three hours later. But this would require another missing technological piece: efficient and affordable long-distance power transmission lines. So, even with miraculously improved solar cells, we would still need other (miraculously improved) pieces to build an energy system. And without such miracles, it's more likely that we will need many different energy-producing pieces, and many different complementary energy storage/transmission/ . . . pieces.
In my class, and now through this website, we'll examine the science and technology behind those energy "pieces," trying to define at least their present day shapes. But the real goal will be to then use that knowledge to figure out how those pieces might someday complete the "puzzle" of a truly sustainable energy system.
|Sustainable Energy without the Hot Air
David J.C. MacKay
Downloadable for free at: Without the Hot Air.com
Or as a paperback from: UIT Cambridge England,
Class Notes vs Web Notes?
For my university class, lectures had to be of fixed length and number. That meant that I had to continuously edit and rearrange things as I added new material to the class. On the other hand, because my students were responsible for all class material, the exact order of presentation was not critical. Which freed me to enhance learning by revisiting critical topics multiple times, treating them in increasing depth, weaving them together with related topics.
But this new website is intended as an online resource for you, the citizen-researcher. And you will likely arrive here searching for information on a single specific energy topic. I hope to lure you into broader study. But to facilitate your immediate research, I am rewriting my class notes into what I will call "web notes." For these web notes:
- Material will be reordered so that single topics are largely covered in a single place (either a single web note set, or consecutive sets).
- Those note sets will then be of whatever length their topic naturally demands.
- However, because some topics (e.g., different energy technologies) share the same issue, discussion of that issue may be repeated in multiple note sets.
- Web note listings (below) will incorporate a drop down outline of each note set.
- Web note PowerPoint files will also begin with a full outline.
This rewrite will continue well into 2018. That is mostly because, in my classes, I required every student to be a fellow investigator by submitting weekly, midterm, and final exam research papers. And I have thus accumulated a large backlog of new material that I am now anxious to add to this website.
But to pique your interest and provoke your input, I am posting my still incomplete and evolving outline of these new "web notes" below. Please send your suggestions to me via this website's Contact webpage.
Older (but complete) Class Notes + Resource Webpages
New (but still Incomplete) Web Notes + Resource Webpages
My Personal Introduction to Sustainable Energy - New Aug 2017
How and why I became interested / How I learned that full energy systems are almost always required
U.S. Energy Production and Consumption (resources webpage) - New Sept 2017 (expanded Nov 2017)
Typical household consumption / Total U.S. electrical power production
How this has (or has not) been changing
The still surprisingly small role of renewables in the U.S.
How states differ in the ways they produce energy
How our consumption varies during the day
The surprising importance of residential consumption => Follow the
Worldwide data and maps of per-capita power consumption
Electricity - Underlying Science & Generic Systems:
The Science of Electricity: What it is / How it's generated / How we now try to transmit it
Part I: Electric & Magnetic Fields (resources webpage, with a dozen video demonstrations) - New Jan 2018
Teaching "E & M" by memorizing equations vs. watching things happen
Our personal experiences with electric fields / The experiences of one British schoolmaster
Electric charge: Two canceling types, attractive to each other, repulsive to themselves
Electric Fields: An abstract way of mapping out the forces between electric charges
Magnetic Fields: Metal filing trails that are NOT force maps
How such non-force-maps can nevertheless explain the forces between magnets
Electro-Magnetism: How charges (driven by Electric Fields) can generate Magnetic Fields
The gravity-defying fall of magnets through non-magnetic metal pipes
Explained by Magnetic Induction = Propulsion of electrons by passing Magnetic Fields
=> Causing their Electro-Magnetism to create an opposing Magnetic Field
Explaining (eventually) metal recycling, maglev trains, electric generators, electric motors . . .
Part II: Magnetic Induction: Motors, Generators & Transformers (resources webpage) - Rewritten Jan 2018
A review of electric & magnetic fields (drawn from preceding note set)
Magnetic-field-sucking "ferromagnetic materials" => Magnetic field directing "Pole Pieces"
The surprisingly straight-forward inner working of electric motors
DC motors that switch "rotor" magnetization via "split ring" electrical contacts
Even simpler AC motors
Increasing and smoothing out a motor's torque by adding multiple electro-magnet pairs
Nikola Tesla's clever "brushless" induction motor alternative
Which, flattened out, now provides the basis for ultrahigh speed "maglev" trains
How the two adjacent coils of "transformers" allow one to transform AC power
Optimizing Voltage x Current choices for either long distance power transmission
Or for the myriad voltages now required for the most efficient & safe use of power
A Generic Power Plant and Grid (resources webpage) - Rewritten & Expanded Feb 2018
Most power plants = Heat source + boiling water kettle + propeller + generator
Including coal, nuclear, biomass/biofuel, and one type of natural gas (CCGT)
Hydro and wind plants omit the heat source & kettle
But photovoltaic power plants (alone) are completely different
Our demand for their power is very cyclic = Base Power + Dispatchable Power
Massive steam plants cannot efficiently meet this cycle (only hydropower can)
And only one type of natural gas plant (OCGT) can deal well with its 2-3 hour peak
Combining many power plants into a grid requires scrupulous synchronization
And even that falls apart if one tries to transmit AC power over long distances
Where the peaks in current and peaks in voltage cease to track one another
Which, accelerated by green energy, is pushing us toward high voltage DC power transmission
As enabled by transformers + diodes + capacitors
Power from Carbon:
Part I: Conventional Fossil Fuels (resources webpage)
The non-green source of two-thirds of U.S. electrical power
Why combustion of solid > liquid > gas gets progressively more energy efficient (and thus clean)
Coal Power: Conventional vs. IGCC vs. Sequestered IGCC (= so-called "clean coal")
Natural Gas Power: Not so efficient (OCGT) vs. very efficient (CCGT)
Fracking basics / wastewater impact / earthquake potential
Global warming problem of "accidental" and "under the radar" methane releases
Part II: Biomass and Biofuels (resources webpage)
Biomass = Burning of already available organic waste & garbage
The #4 low-carbon-footprint provider of U.S. electricity (1.6% of total 2016 electricity*)
Biofuels = Deliberate cultivation of fuel crops
Their too often abysmal ratio of energy output to net energy input
Their surprisingly large impact upon the environment & world food prices
But how they might provide the solution to air transportation's huge carbon footprint
Hydroelectric Power (resources webpage)
The #2 low-carbon-footprint provider of U.S. electricity (6.3% of total 2016 electricity*)
The Science of Hydro
The alternatives of conventional (reservoir) dams vs. "Run of the River" vs. "Pumped Storage Hydro"
Issues / criticisms of hydro including:
Land use (as in agriculturally / ecologically critical river deltas)
Concrete's carbon footprint
(Release of mercury soil pollutants?)
The saltwater potential of wave and tidal energy
Wind Power (resources webpage)
The #3 low-carbon-footprint provider of U.S. electricity (5.6% of total 2016 electricity*)
The Science of Wind
The extreme importance of height
How peak wind speed can be more important than average wind speed
Wind Turbine Technology
Wind Farm Layout
A wind turbine's "capacity" vs. its average energy production
Mismatch in timing between wind energy production vs. consumption =>
Critical need for wind energy storage
And for vastly improved power transmission
The importance of location, location, location!
Offshore wind farms exploiting faster more sustainable winds (plus reduced NIMBY!)
Growing technology behind offshore wind turbines & possible deep-water floating wind turbines
Hurricane resistant wind turbines?
Turbines vs. Birds & Bats
The #5 low-carbon-footprint provider of U.S. electricity (0.9% of total 2016 electricity*)
Part I: Today's Solar Cells (resources webpage) - New Sept 2017
What is electricity? => The need for "electron pumps"
What is sunlight? How does light interact with various materials
How to make an electron pump (vs. a non-energy-producing "photoconductor")
Creating free electrons and holes by adding donors & acceptors
=> Electron-pumping interfacial electric fields
Choosing solar cell material to milk the most power from sunlight: The Shockley-Queisser Limit
Silicon's idiosyncrasies => The impact of "indirect bandgap" & "traps"
Today's diamond, gold, silver & bronze standards / Record solar cell efficiencies
The huge difference between average and peak solar cell power output
Dealing with reflection (why many solar cells appear blue)
Lifetime solar cell energy output vs. lifetime energy input
Part II: Tomorrow's Solar Cells (resources webpage)
How we might beat the S-Q limit of ~30% solar cell efficiency:
Tandem cells combining cells of different materials
Quantum Dot cells combing differently sized nano structures
How we might build much less expensive cells:
Thin film PV cells including perovskites and dyes
How we might instead transform the sun's spectrum to match the cells:
Luminescent Solar Concentrators (LSCs) for windows
Conversion of Waste Heat to electricity via metamaterials
Part III: Solar Thermal Power / Solar Thermal Energy Storage (resources webpage)
The two types of solar thermal plants:
Concentrated solar thermal (solar towers) versus
Distributed solar thermal collectors
Why solar thermal is today's most expensive energy technology
But how solar thermal with built-in energy storage might be a green energy champ:
Molten salt energy storage
Solar thermal collectors & towers vs. birds & bats
Part IV: Our First Attempts at Affordable Grid-Scale Solar Energy (resources webpage)
Including California's Topaz plant
Concentrated solar thermal plants:
California's Ivanpah and questions raised by omission of energy storage, and bird kills
Versus Nevada's Crescent Dunes with its built-in energy storage
Distributed solar thermal farms
Including Morocco's Quarzazate
Exotic Power Technologies (resources webpage)
Small potential / Unproven: Flying Wind Turbines
Medium potential / Proven but thus far in only exceptionally favorable locations: Geothermal
Large potential / Unproven and hugely expensive: Orbiting Solar Power Stations
Huge potential / Unproven and still elusive after the better part of a century's R&D: Nuclear Fusion
Electrochemical Energy Storage:
Part I: Today's Batteries (resources webpage)
As seen around the house vs. in electrified transportation vs. for Grid energy storage
Part II: Tomorrow's Batteries / Tomorrow's Fuel Cells (resources webpage)
ARPA-E's push for cheaper / more efficient / safer batteries including:
"Saltwater" (aqueous hybrid ion) batteries, solid-electrolyte Li batteries & quinone flow batteries
Fuel cell basics
Fuel cells as enabler of a "hydrogen economy" - or least electrified transportation
But only with radical improvement in their surprisingly poor energy storage efficiency
The #1 low-carbon-footprint provider of U.S. electricity
(19.7% of total 2016 electricity*)
Part I: But they blow up! (resources webpage) - Expanded Dec 2017
Nuclei: What they contain, how to keep track of this
Fission of abundant U238 vs. rare U235
Use of "moderators" to slow emitted neutrons => Sustained fission chain reactions
vs. neutron "poisons" and neutron "mirrors"
Chain reactions in bombs vs. chain reactions in nuclear reactors
Common "light water" moderated reactors:
Boiling Water Reactors (BWR) vs. Pressurized Water Reactors
As opposed to carbon moderated RBMK reactors
Three Mile Island
Fukushima Dai Ichi
The claim that massive use of concrete negates nuclear's ~ zero greenhouse emission
Part II: Prehistoric Nuclear Reactors? (resources webpage) - Rewritten Aug 2017
Part III: Gen III / III+ Reactors: Confronting Cost & Operational Safety (resources webpage)
AP-1000 / ES-BWR / Small Modular Reactors
Part IV: Gen IV Reactors: Two Designs that Might Radically Reduce Nuclear Waste (resources webpage)
Liquid Fluorine Thorium Reactor / Traveling Wave Reactor
Part V: A Brief Review of Other Gen IV Reactors (resources webpage)
*Historical data on U.S. energy sources are given in my U.S. Energy Production and Consumption web note set:
Show/Hide Enlarged Figure
Power Plant Requirements: Land & Water (resources webpage) - Revised Nov 2017
How much power does a "typical" plant generate? How many plants does the U.S. need?
Calculation of power plant land use for all of the different technologies
With design goals based on current U.S. power consumption:
1000 power plants of 1 GW power production capacity
Leading to table of net land use if each technology produced ALL of U.S. power
Calculation of power plant water use for all of the different technologies
Water for 100% use of biofuel power is likely ~ ALL available fresh water
With portion returned to rivers often polluted by agricultural chemicals
Water for 100% steam-driven power plants ~ 2X Mississippi River
But almost all of that water is returned to rivers "polluted" only by warming
Minimal water consumption for solar PV, some solar thermal, wind and OCGT natural gas
Power Plant Requirements: Minerals & Fuels (resources webpage)
Lifetime Energy Return on Energy Invested - EROI (resources webpage) - New Oct 2017
Shortcomings of a purely economic assessment of energy technologies
Energy Payback Time vs. full lifetime energy cycle assessment
Definition and classic papers on Energy Return on (Energy) Invested: EROI
A re-examination of EROI data based on newer/additional data + technological insights
Dramatic increases in Wind and Nuclear EROIs suggested by their technological evolution
The murky world of biofuels where good intentions can strongly color EROI evaluation
Power Plant Economics: Analysis Techniques & Data (resources webpage) - Rewritten/Updated Oct 2017
Time value of money + Uniform payment series + Present value
Worked example of a power plant's lifetime financing
Application in computing a breakeven Levelized Cost of Energy: LCOE
LCOE data from the U.S. Energy Information Agency: 2011 - 2017
Analysis of EIA data peculiarities and trends
Examining the EIA assumption of across-the-board 30 year power plant lifetime
LCOE data from Lazard
Comparison of data from all sources
Resulting conclusions about present day renewable energy economics
Appendix tables of "U/P", "P/U", "F/P" and "P/F" function values
Personal Energy Consumption:
Energy Consumption in Housing - Revised Nov 2017
Our homes consume over 1/5th of U.S. energy
90% of which involves producing and moving heat
How that heat is moved:
CONDUCTION = Transfer of vibrational energy between atoms/molecules
CONVECTION = Movement of hot atoms/molecules to cooler places
RADIATION = Flow of energy via electromagnetic waves (e.g., as infrared heat)
Detailed analysis of how each of these mechanisms affect our homes
And the often simple & cheap things we can do to decrease their impact
Long term energy-saving strategies, including passive solar and smart(er) homes
Versus big savings available NOW via things like "condensing furnaces" and "heat pumps"
Energy Consumption in Transportation (resources webpage)
Green(er) Cars & Trucks (resources webpage)
Fitting Round (Renewable) Pegs into a Square (Grid) Holes:
A Renewable Grid: Trying to Get Power When We Need It, Where We Need It (resources webpage)
A Partial Solution: Massive Energy Storage + Long Distance Power Transmission (resources webpage)
Smart Grid: Robust/Energy Efficient vs. Hackable Orwellian Nightmare? (resources webpage) - Expanded Dec 2017
How major U.S. blackouts prompted thinking about a "Smart Resilient Grid"
And how deregulation has since made the Grid even less reliable
The five elements proposed for such a robust and energy-efficient Grid:
Sensing trouble: Phasor (phase and frequency) Measurement Units (PMUs)
Isolating trouble: Local, smart, microprocessor-based sensors & circuit breakers
Logging & managing trouble: Digital Supervisory Control & Data Acquisition (SCADA) systems
Communicating trouble: An Intranet linking the whole Grid together
Controlling demand thereby mitigating trouble: An Advanced Metering Interface (AMI)
The latter involving power companies monitoring and/or controlling your IoT home appliances
Raising huge security and privacy issues (including hacker/governmental sabotage)
Versus some far less intrusive smart(ish) energy-saving tools & strategies
The Bigger Picture:
Climatology and Climate Change (resources webpage) - Expanded January 2018
Inconvenient truths about An Inconvenient Truth?
Paleoclimatology: Gathering climate data spanning millions of years
Ten thousand years: Dendrochronology (tree rings), radiocarbon dating . . .
Hundred thousand years: Glacial ice cores . . .
Million years: Geology, fossils and their isotopic ratios . . .
The recent stark increases in atmospheric gases such as CO2
vs. a less stark upward trend in temperature
Climate Models: The long, long list of effects & mechanisms that must be included
Their surprisingly slow incorporation during the 1970's to 1990's
The 2000's: Supercomputers finally allow for high-resolution worldwide modeling
The ongoing transition from fitting past data toward accurately predicting future data
Greenhouse Effect, Carbon Footprint & Sequestration (resources webpage) - Revised Dec 2017
Building a simple "do-it-yourself" model of the Greenhouse Effect based on:
1 color of sunlight + 1 color of earthlight + 1 greenhouse gas
Which ultimately collapses because: It's all about different colors
Colors where gas A absorbs & emits vs. colors where gas B absorbs & emits
Critical colors = Those where earth might radiate away heat (particular infrared colors)
But is now being thwarted by the addition of new atmospheric gases
Data on gases now accumulating in the atmosphere
Including now-censored "EPA Inventory of U.S. Greenhouse Gas Emissions & Sinks"
Discussion of atmospheric gas sources, especially energy industry sources
Possibilities of reducing such emissions
Or of at least "sequestering" those emissions
Where Do We Go From Here? (Cap & Trade / Carbon Tax?) (resources webpage) - Revised Nov 2017
Searching for an effective, politician & lobbyist-proof, way of mitigating climate change
Cap & Trade: Affecting industry directly / but me only indirectly
Its success with acid rain vs. the complexities of applying it to climate change
Carbon Tax: Affecting ALL directly
What tax rate would be required to produce the desired changes?
A prediction based on present day energy economics
What is my personal carbon footprint? => How much tax would I likely pay?
Household cost as a function of carbon tax rate and your local energy sources
Would this be justified by what economists call the Social Cost of Carbon?
Their last two decades of research & debate about this cost
My analysis of their data, incorporating more recent climate modeling
Suggested Energy News Sources:
Copyright: John C. Bean