Meen 489 689 lecture 6 diffusion and failure at nano scale + synopsis of the energy sector
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Diffusion and Failure at nano scale + Synopsis of the Energy Sector
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Meen 489 689 lecture 6 diffusion and failure at nano scale + synopsis of the energy sector
- 1. MEEN 489/689: Entrepreneurship & Nanomaterials for Energy Applications Lecture 6: Diffusion & Failure at the Nanoscale Synopsis of the Energy Sector James Donnell, Andreas Polycarpou, Tanil Ozkan, Haejune Kim Fall 2015 19/8/2015
- 2. MEEN 489/689 29/8/2015 How about nanoscale?
- 5. MEEN 489/689 59/8/2015 You won’t be tested on the derivation but should be able to explain why diffusion is faster at the nanoscale.
- 6. MEEN 489/689 69/8/2015 Is this kind of analysis still applicable at the nanoscale?
- 9. MEEN 489/689 99/8/2015 What can be done to avert mechanical failure while keeping the process scalable?
- 10. MEEN 489/689 Application: Hard disk drives R. Wood, J. Magn. Magn. Mater. (2008) Nanotechnology 1: Ultra thin (and robust) films and super smooth (or structured) surfaces Nanotechnology 2: Head-disk interface (nanometer level spacing and features) at 100 mph A. Recent Thermal Flying Control technology shifted the interface interactions to smaller (nm) scales B. Proposed Heat Assisted Magnetic Recording possesses temperature challenges
- 11. MEEN 489/689 Hard disk drive (HDD) mechanics D. Weller, Seagate Slider Magnetic disk Slider Original Flying Height Adjusted Flying Height Protruded Pole Tip )747( 66.70 57.0 25.1 10 )( Boeing m mm mm nm Slider = < 1mm Runway or road Need reliable flying at 100 mph of few nm spacing How to do it? Is small better?
- 12. MEEN 489/689 12 0 1 2 3 4 5 6 0 10 20 30 40 50 60 Separation, h (nm) AdhesiveForces(mN) Table 1: Fvdw Eq. (4): FIDMT Eq. (1): Fel Eq. (16): Fel,rough Eq. (17): Proposed Model 3 3.5 4 4.5 5 5.5 0 0.1 0.2 0.3 0.4 0.5 0.6 Separation, h (nm) AdhesiveForces(mN) Two flat parallel surfaces Proposed (rough surface) 0 1 2 3 4 5 6 0 10 20 30 40 50 60 Separation, h (nm) AdhesiveForces(mN) Table 1: Fvdw Eq. (4): FIDMT Eq. (1): Fel Eq. (16): Fel,rough Eq. (17): Proposed Model 3 3.5 4 4.5 5 5.5 0 0.1 0.2 0.3 0.4 0.5 0.6 Separation, h (nm) AdhesiveForces(mN) Two flat parallel surfaces Proposed (rough surface) Roughness = 0.74 nm Radius = 5.22 µm Asperities = 9.33 µm-2 Total lube = 10 Å Mobile lube = 5 Å Contact Force = 0.151 N/m Nominal contact = 300 um2 Adhesive Force Comparison (Flat-on-Flat vs. Rough Surface) The most important difference between idealistic smooth and “rough” cases is that the range of adhesive forces is LARGER when roughness is included Rough surface model indicates rise of adhesion at higher flying-height Suh and Polycarpou, JAP (2006)
- 13. MEEN 489/689 Areal Density Road Map
- 14. MEEN 489/689 149/8/2015 Synopsis of the Energy Sector
- 15. MEEN 489/689 15 9/8/2015 Coal: 10,000 tons of coal per day (1freight train) Nuclear: 100 tons of uranium per year Hydroelectric: 60,000 tons of water per second Comparison of power plants for 1 GW
- 16. MEEN 489/689 16 9/8/2015 Energy portfolio of industrialized nations Although most of our energy originally comes from the Sun (except nuclear), only a minuscule amount of solar energy is being used today.
- 17. MEEN 489/689 17 9/8/2015 Supply and demand are far apart Wind Solar
- 18. MEEN 489/689 Electrical Storage Chemical Storage Storing energy Energy/Weight Energy/Volume 0 10 20 30 0 10 20 30 40 Energy Storage Density Gasoline Batteries Supercapacitors • How do we store solar electricity overnight, wind electricity when calm ? • The range of all-electric cars is short due to poor storage by batteries. • Batteries have 30-50 times lower energy density than gasoline. • Chemical energy is easy to store in fuel, but electricity is not. Ethanol 14
- 19. MEEN 489/689 Electricity potential of our Sun (photovoltaics) 100Ă—100 square kilometers of solar cells could produce all the electricity for the US. But they are still too costly. 0.4 TW US Electricity Consumption 15
- 20. MEEN 489/689 The required area of solar cells 1 kW/m2 (Incident solar power) × 1/4 (Fraction of useful daylight) × 0.16 (Efficiency of a solar cell ≅ 16%) × 100×100 ·106 m2 (100×100 km2) = 4 · 108 kW (Electric power generation in the US) 0.4 TW US Electricity Consumption 16
- 21. MEEN 489/689 COMPANY PERCENT SOLAR IKEA 87% GM 43% VF Outdoor 33% Johnson & Johnson 24% REI 21% Costco 17% Kohl's 13% Anheuser- Busch 13% Campbell's Soup 12% Hartz 11% Walmart 5% Macy's 5% Whole Foods 5% Bloomberg 4% Tiffany's 3% Safeway 3% Commercial Users by Percent of Facilities with Solar Power The table below lists companies in order of the percentage of their facilities that are solar powered. This list provides another comparison for those companies that ranked highly in both installed capacity and number of installations. Note, this list is exclusively populated by companies surveyed for this report and does not include smaller companies that might otherwise be considered to have higher ratios than presented below. www.seia.org/researc h-resources/solar- means-business-2014- top-us-commercial- solar-users 17
- 22. MEEN 489/689
- 23. MEEN 489/689 The efficiency keeps growing slowly
- 24. MEEN 489/689 How much would it cost to generate all the electricity in the US by solar cells ? 1 $/W (Price of solar cells) × 4 ·108 kW (Electric power generated in the US) = 4 ·1011 $ = 400 Billion Dollars The support structure adds substantial costs. 20
- 25. MEEN 489/689 Solar thermal Convert solar energy to steam, then to electricity
- 26. MEEN 489/689 Solar thermal (31% efficiency)
- 27. MEEN 489/689 Fuel from the Sun ? • Photosynthesis • Biofuels • Split Water Plants convert solar energy to chemical energy but the efficiency is low (1%-2%) Convert plants to fuel: Make ethanol, diesel fuel from sugar, corn starch, plant oil, cellulose ... Split water into hydrogen and oxygen using sunlight. Use hydrogen as fuel. No greenhouse gases. (Futuristic) 23
- 28. MEEN 489/689 A little help from nanotechnology? 24
- 29. MEEN 489/689 Biofuels versus photovoltaics (PV) How far could one drive a car with the energy produced by 100x100 m2 (2.5 acres) of land in a year ? Biodiesel: 21 500 km Bioethanol 22 500 km Biomass to liquid: 60 000 km Photovoltaics, electric car: 3 250 000 km Solar cells are more efficient than photosynthesis. Electric motors are more efficient than combustion engines. PHOTON International, April 2007, p. 106 (www.photon-magazine.com) 25