Thermoelectric Silicon Nanowires: Large- area arrays of rough Si nanowires that are 20-300 nm in diameter. ADVANTAGES The first thermoelectrics to show promise as economical, high-performance and scalable materials. 100-fold reduction in thermal conductivity as bulk Si. Maintains same Seebeck coefficient. Current ZT value = 0.6 “ With optimized doping, diameter reduction, and roughness control, the ZT is likely to rise even higher.” – Nature 2008 article* ZT = S 2 T = Measure of Efficiency ρκ T S: Seebeck coefficient (thermopower) T: Temperature ρ : Electrical resistivity κ T : Thermal conductivity ZT > 1 is required for commercialization.
Why HEV? Already has a battery in place to utilize the electrical energy relatively easier to integrate technology. Everyone needs a car! (U.S. Sales: 17 million cars/yr) Hybrid vehicle market has high projected growth.
Market Share Growth: 2007: 2.5% 2010: 4.6 % 2016: 10% - Center for Automotive Research, Ann-Arbor J.D. Power Predictions: 65 hybrid models by 2010 Expected jump in 2009 sales due to next-generation Prius and Honda hybrid 2010: Sales expected to reach 775,000 units
Homogeneous Charge Compression Ignition - Lean combustion: spark + compression ignition Lowers production of NO and ozone None on commercial scale due to difficulty of control, limited power range and high CO emissions. Successful prototype by General Motors, Inc. Bulk Thermoelectrics (e.g. Bi 2 Te 3 ) - ZT values are too low. Quantum Well Thermoelectrics Achieve high ZT values (2.0 to 3.0). Very expensive Not scalable. Power Chips No prototypes yet.
MITIGATING THE RISKS Technology : “With optimized doping, diameter reduction, and roughness control, the ZT is likely to rise even higher.” – Nature 2008 article* Peidong Yang said they can have a large-scale prototype in one year. Team : might have to find people with experience in business, operations, marketing, sales, etc. Just like any other start-up. Market : Avoid changing the design of the car right now as much as possible. Financial : Partnerships, people who already have capital equipment and can contribute to R&D. technology: how often do the nanowires have to be replaced?
The Battery Canon Harnessing Waste Energy: From Heat to Electricity Jay Ni Nandita Sriram Jonathan Tan Zhi Kuang Tan Andy Teo ENGR 145 Winter 2008
The Problem *Based on calculations comparing the Honda Civic to the Honda Civic Hybrid It takes nearly 15 years to recoup the extra investment in hybrid cars! * Who would want to make this commitment?