1. Office Hours Next week Final Exam: Tuesday 16 Dec. 7:15 SW007 DVB office Hours next week: –Monday: 13:30 to 16:30 –Tuesday: 10:00 to 12:00 13:30 to 15:30

2. Summary of problems with Nuclear Fission Very expensive to build power plants (at least the way it is done in the USA). Potential for weapons proliferation by diversion of 235 U or byproducts to “undesirables” Handling of the waste (both from health and proliferation points of view). Very small probability of a very bad accident (Chernobyl, although an event just like that is impossible with western designs). New reactor designs, fuel cycles (Thorium), waste processing, etc. could provide ways out of many of these but will take research and significant investments!

3. Nuclear Fusion http://www.nuc.berkeley.edu/fusion/fusion.html The reaction shown is the easiest to use, but D-D is also possible and is what we discussed in class, simply because it is easier to get the fuel and the math is a bit easier. 2*M D = 4.027106 amu vs. 3 He + p = (3.0160293+1.007825) amu + ~2MeV or 3 H + n = (3.0160492+1.008665) amu + ~3MeV NOTE: 3 He and p are stable 3 H has a half-life of 12 years, n of 15 minutes. This process produces no long-lived radioactivity directly, unlike fission.

4. ITER http://www.iter.org/index.htm Proposed 500MW Fusion test Facility. First plasma expected 2016. “International Thermonuclear Experimental Reactor”

5. Inertial confinement http://www.nuc.berkeley.edu/thyd/icf/target.html

6. The Hydrogen Hype Can’t mine it, it is NOT an energy source –Why not just use electricity directly? Even as a liquid, energy density is low –Storage and transport are difficult issues More dangerous (explosive) than CH 4 No existing infrastructure The Realities H 2 burns with 0 2 to make water H 2 comes from the oceans (lots of it) Fuel cells can “burn” it efficiently

7. Hydrogen Economy Need lots of research in areas such as: –Production –Transmission/storage –Distribution/end use Hydrogen seems to be an attractive alternative to fossil fuels, but it cannot be mined. You need to treat it more like electricity than gasoline (i.e. as a carrier of energy, not as a primary source).

8. http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/review04/4_science_stevens_04.pdf

11. Storage Possabilities Physisorbtion Chemical Reaction Chemisorbtion Encapsulation Weak binding energy -> Low T required Carbon nanotubes Porous materials Zeolites Reversible Hydrides PdH, LiH, … Large energy input to release H2 Slow Dynamics Very large energy input to release H2 Not technologically feasible H2 trapped in cages or pores Variation of physical properties (T or P) to trap/release H 2 4 H molecules in 5 12 6 4 cage Al H

12. http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/review04/4_science_stevens_04.pdf

13. DOE report from 2004 is available at: http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/review04/4_science_stevens_04.pdf MIT web site on photo-production: http://web.mit.edu/chemistry/dgn/www/research/e_conversion.html Nature and Physics Today articles: Nature Vol. 414, p353-358 (2001)Physics Today, vol 57(12) p39-44 (2004)

14. http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/review04/4_science_stevens_04.pdf

15. Fuel Cells- sample schematics http://www.iit.edu/~smart/garrear/fuelcells.htm For more details on these and other types, see also: http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/fc_types.html

16. Alkaline Acid –High efficiency (up to 60%), small, pure H 2 fuel, very sensitive –Used by NASA (very expensive, so only they can afford it) Molten Carbonate –High efficiency (up to 60%), high temp operation (600C), bulky, robust –Used in back-up generation/ Combined Heat/Power (CHP) modes (Fuel Cell Energy) Polymer Electrolyte Membrane (PEM) –Lower temp operation (<100C), sensitive catalysts/ reformers needed, compact, lower efficiency (35%??) –Leading candidate for transportation (Ballard) Solid Oxide Fuel Cells –Highest efficiency (70%), very high-T operation (1000C) –Still in development, not yet commercially viable Synopsis of Fuel Cell types

17. Polymer Electrolyte F.C. (Ballard) 85kW basic module power (scalable from 10 to 300kW They say) for passenger cars. 212 lb (97 kg) 284 V 300 A Volume 75 liters Operates at 80 o C H2 as the fuel (needs a reformer to make use of Methanol etc.) 300kW used for buses

18. Fuel Cell Vehicles Honda: FCX Clarity (Celebrity customers in CA, leasing in Japan) Chevy Equinox (test fleet launched this year) Toyota FCHV (concept car) All use PEM fuel cells http://en.wikipedia.org/wiki/Fuel_cell http://automobiles.honda.com/fcx-clarity/how-fcx-works.aspx

19. Molten Carbonate F.C. (Fuel Cell Energy: “Direct Fuel Cell”) Appears to be a molten carbonate system based on their description Standard line includes units of 0.3,1.5 and 3 MW Fuel is CH 4 (no need for external reformer) can also use “coal gas”, biogas and methanol Marketed for high-quality power applications (fixed location) This is a nominal 300kW unit (typically delivers 250kW according to their press releases). Most of the units installed to date are of this size.

20. http://www.netl.doe.gov/publications/proceedings/03/dcfcw/dcfcw03.html http://www.netl.doe.gov/publications/proceedings/03/dcfcw/Cooper%202.pdf

21. Solid Oxide F.C. (Siemens) Efficiencies up to 53% have been demonstrated at 3 atm gas pressure (compared to about 35% for diesel/generator for distributed power generation), but I don’t think that they have installed any yet. http://www.powergeneration.siemens.com/products-solutions-services/products-packages/fuel-cells/

22. Review for Final Exam Exam will have roughly 30 questions (i.e. slightly longer than previous exams, but you have much more time; one question worth 10 points others 5). Roughly half of the questions will cover material discussed since exam II, the rest will be roughly equally split between material covered on exam I and exam II –(since exam II: Chapters 10-12, 14,16, with small amounts from chapter 13 (A-F)). Cover page is up on ONCOURSE with changes since exam II highlighted in blue. ~10 questions involve some sort of calculation or numerical answer. Look at reviews from week 5 and week 10 for summaries of important points from those sections of the course. The highlights of the last third of the course are described on the following slides.

23. Exam Review: Electricity Action of a battery, the concept of EMF Ohm’s law and power: V=IR P= IV Parallel and series circuits Faraday’s law and the generation of electricity Transformers The electric power grid: Generation, transmission, distribution

24. Exam Review: Electricity Generators and motors are very closely related Different sources have different load factors –(coal/nuclear 65-85%, wind/solar: 20%-30% etc.) Three major costs associated with electricity generation (mix depends on type of plant). –Investment costs –Operations and Maintenance –Fuel

25. Summary of wind power Power available is roughly: –P= 0.3 D 2 V 3 (P in W for D in m and V in m/s) i.e. you get much more power at higher wind speeds with larger turbines 3-blade turbines are more efficient than multi- blade, but the latter work at lower wind speeds. At higher wind speeds you need to “feather” the blades to avoid overloading the generator and gears. Typical power turbines can produce 1 -3.5 MW You still find people question having even this form of generator near where they live!

26. Provide a source of DC electric power where the EMF is provided by absorbed light Need to absorb the light –Anti-reflective coating + multiple layers Need to get the electrons out into the circuit (low resistance and recombination) –Low disorder helps with both (hence crystal is more efficient than amorphous) Crystalline Si: highest efficiency (typically 15- 25%, multi-junction record ~ 43%), poorer coverage, bulk material but only the surface contributes, expensive (e.g. NASA). Amorphous Si: lower efficiency (5-13%), less stable (can degrade when exposed to sunlight). Newer styles, e.g. CIGS, organic, could reduce costs (but so far are of quite low efficiency). Synopsis of Solar Cells

27. Nuclear Energy Binding energy of nuclei are MUCH LARGER than that of moelcules –E=mc 2 Radioactivity –Comes from both the primary reactions (especially in fission) and activation by the neutrons released in the reactions (both). –Half life, decay modes, health hazards Fission: –Split a large nucleus into smaller nuclei PLUS 2 or 3 neutrons after absorption of a SLOW neutron. –Energy release on the order of 0.74MeV/amu of fuel –Lots of such plants exist throughout the world, but there are problems Expensive to build (especially in the US) Safety issues Waste issues

28. Nuclear Energy (cont.) Waste from nuclear power: –Spent fuel and decommissioned parts are both radioactive –Short-term issue (proliferation concerns) as well as long-term Fusion: –Combine two light nuclei (typically isotopes of hydrogen) into one (typically He) with release of energy ~0.84MeV/amu (and neutron(s)). –Fuel “waste” is much easier to deal with (less active, shorter half-lives) –Decommissioning may be even a bigger problem than with fission (more energetic neutrons produced).

29. Review: Hydrogen economy H 2 is, Potentially, a clean “burning” fuel that can be used in (efficient) fuel cells and is abundant H 2 is NOT a primary fuel (you don’t dig it up; like electricity it is really an energy carrier). Presently the cheapest way to make it uses CH 4 as input source (so not carbon neutral in practice, although it could be in principle). Lots of infrastructure and research needed to realize the promise: Production, Storage, Distribution, End use, safety, etc. all need significant research progress to be viable.

30. Chemical energy is converted directly to (DC) electrical energy. Similar to battery, but there is an input fuel and there is exhaust, you’re not limited to an “on- board” chemical supply. Need electrodes, electrolyte, probably catalysts at the electrodes, and perhaps a reformer. Different types have different chemistry, electrolyte, operating temperatures, efficiencies, size, and robustness (etc.). You should know advantages/disadvantages and market niches for each type (see next slide). Synopsis of Fuel Cells

31. Alkaline Acid –High efficiency (up to 60%), small, pure H 2 fuel, very sensitive –Used by NASA (very expensive, so only they can afford it) Molten Carbonate [Fuel Cell Energy Corp.] –High efficiency (up to 60%), high temp operation (600C), bulky, robust –Used in back-up generation/ Combined Heat/Power (CHP) modes Polymer Electrolyte Membrane (PEM) [Ballard Power] –Lower temp operation (<100C), sensitive catalysts/ reformers needed, compact, lower efficiency (35%??) –Leading candidate for transportation Solid Oxide Fuel Cells [Siemens] –Highest efficiency (70%), very high-T operation (1000C) –Still in development, not yet commercially viable Synopsis of Fuel Cell types