Energy. on this world and elsewhere. Instructor: Gordon D. Cates Office: Physics 106a, Phone: (434)

Transcription

1 Energy on this world and elsewhere Instructor: Gordon D. Cates Office: Physics 106a, Phone: (434) Course web site available at click on classes and find Physics or at October 29, 2013

2 Announcements Homework will be posted on Oct Office hours Wednesday, 6-8 pm. Midterm November 14. Homework will be due on November 7. You are allowed a 1-page cheat sheet, 8.5x11 or equivalent. ONE SIDE ONLY, and it must be HAND WRITTEN.

3 Readings (post Feynman and Energy and Technolgy) Muller, Energy for Future Presidents - Preface and Intro - Section I (all), Chapters Section II (all), pre-chapter material, and Chapters Section III, chapters 8-10 Richter, Beyond Smoke and Mirrors - Intro - Chapter 1. - Part I (all), Climate, Chapters Part II, Energy, Chapters 6-10 Class Notes through Chapter 4, Chapt 5 available soon.

4 Biofuels

5 Putting renewable energy sources into perspective TPES = Total [world] Primary Energy Supply From this table, we can see that photosynthesis does not have a great edge when it comes to providing a big chunk of TPES

6 History of ethanol The original Model T Ford was designed to run on gasoline, kerosene or ethanol, and various combinations thereof.

7 Henry Ford and ethanol Photo taken in 1933 in Lincoln Nebraska. Published: September 20, 1925 Copyright The New York Times

8 Is a particular technology realistic? Is it practical and economical? Is it scalable?

9 Corn-based ethanol In the U.S., mostly made from fermenting corn-based feedstock. - - In terms of energy, ethanol represents about 4% of fuel used the transportation sector (higher when considering only gasoline-powered vehicles, and higher still when considering gallons of fuel). Energy independence and security act of 2007 mandates that biofuels should include 36 billion gallons annually by 2022 (ethanol in 2011 was around 12.9 billion, and biodiesel production was 0.97 billion). Yield: around gallons/acre/year For 320 billion gallons/year, would need around million acres. We have around 411 million acres in cultivation

10 Crop land in the U.S. 441 million acres devoted to cropland (for comparison). This area represents around 880 million acres, the minimum we could consider. Using current production numbers, we would need something like 850 to 1000 million acres to produce enough ethanol for all our liquid fuel needs.

11 Clicker question revisited Which statement is true in reference to corn-based ethanol? A. There is easily enough cropland to produce cornbased ethanol for our transportation needs. B. There might be enough cropland if we essentially grew no food. C. There is not nearly enough cropland to supply cornbased ethanol for transportation. D. There is easily enough, but only if we learn to convert cellulose economically for fermentation.

12 Is there a net energy gain? Cornell Berkeley

13 Is there a net energy gain? Cornell Berkeley

14 Is there a net energy gain? While the net energy gain is not impressive, only around 10,000 BTU s of the input are in the form of petroleum, so according to these authors, ethanol can reduce our reliance on crude oil.

15 Corn ethanol - is there an energy gain? A report published in 2002.

16 Corn ethanol - is there an energy gain? The authors also said that the energy ratio was steadily improving. One hopes that today things are better still.

17 Comparing ethanol from corn and sugarcane A highly reliable table from Wikipedia Text Text

18 Cellulosic ethanol production

19 What about cellulosic ethanol from switchgrass? Takes about the same amount of cropland, but... The cropland can be marginal for other crops According to one study, 500% more renewable energy is produced than is consumed. The study is impressive, but I think the jury is still out.

20 Biofuels and biofuel co-products In units of BTU s, where 1000 x BTU s = 1 quad. At first glance, at 1.87 quads in 2010, it may seem that biofuels are leading other new renewables for primary energy consumption (around 1.5%). In fact, though, it takes a lot of energy to produce biofuels.

21 Biodiesel

22 Biodiesel in the U.S. in 2010 Disitillate Fuel Oil (diesel + other stuff): 1.39 billion barrels (about 42% the size of gasoline consumption). Biodiesel produced: 7.4 million barrels (0.53% of consumption). Biodiesel consumed: 5.3 million barrels (0.38% of consumption). We are a net biodiesel exporter.

23 Biodiesel - what is it? Biodiesel is renewable diesel fuel substitute that is made by chemically combining natural oils and fats with methanol or ethanol. A blend of 20% biodiesel and 80% petrodiesel, (often known as B20) can be used in almost any diesel vehicle. Engines using pure biodiesel (B100) may require minor modifications to avoid performance or maintenance issues. Some of the sources of feedstock from which biodiesel is made include: - rapeseed oil (most common source in Europe) - soybean oil (most common source in the U.S.) - canola oil - algae (presently very small percentage, but most efficient use of land)

24 Biodiesel - how is it made? Inputs include oil from plants and methanol Outputs include glycerol and biodiesel

25 Biodiesel - how is it made?

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