EmanuelSachsFredFortFlowersandDanielFortFlowers
ProfessorofMechanicalEngineeringMIT
Photovoltaics; Opportunities and Challenges
Harnessing solar energy is critical
• Covering0.2%ofthelandareaoftheUSwith20%efficientPVsystemswouldgeneratealltheelectricitythattheUSconsumes
History and Status of Silicon PV
*LCOE calculated assuming 5.75kWh/m2/day (17% capacity factor), a 7% discount rate, and a 30-year project life.
Solar at the cost of coal
Wafers; Sawn ingots vs. Kerfless Current Silicon-Wafer Process
Cast Ingot Cut Brick
5
Saw Wafers Clean & Damage Etch Wafers
2X of Everything for
1 Wafer
Silicon to Wafer in 1 Machine
MoldWafer
Pure Silicon
50% contaminated
waste
Pure Silicon
1366 Direct Wafer (DW)
Direct Wafer: Timeline
1/09 Dec Conception
First Tin Wafers
First Silicon Wafers
Win $500k NREL
Win $4M
ARPA-E
First cells
1/10 6” furnace design and
build
Scale to 3” wafers
12.5% cells
15-16% on 6”
wafers
String Ribbon silicon Issues:1. Breakquality/
throughputtradeoff
2. Reducecapitalcosts
3. Producestandard‐sizewafer
Vertical ribbon growth Increasing Growth rate → Low Lifetime
→ high dislocation density → low lifetime (after Bentzen, J. Appl Phys. 99)
Maximizegrowthrate→hightemperaturegradient&curvature → high stress
Tempe
rature
Height
Self-Aligned Cell
Self‐AlignedMetallizaUon
30µm fingers Texture and grooves in 1 step
Light-trapping texture guides precision metallization
9
Isotexture Issues • Lighttrapping• CosmeUcuniformityandconsistency
• SawdamagesensiUvity
• WaferqualitysensiUvity– ShunUngatdislocaUons
• InconsistentwithfuturePVdirecUons– Reardielectrics– Kerflesswafers
1366 Texture Solution • Elegant,low‐cost,texturingtechnologytosimultaneously:
1. Formhoneycombfronttextureo Bestproventexturefor
mulU
2. Polishtheback3. Formfrontgroovesif
desiredo Highperformance
metallizaUon
1366 Metallization Solution
• SelfaligneddeposiUonofAgpasteintogrooves• Platedfingers<40micronswidex10micronstall• ContactresisUvity<0.001ohms‐cm2on100ohms/squniformemiaers– NoneedforexpensiveselecUveemiaers
China Leading Global Race to Make Clean Energy Jan 30, 2010
• LargestManufofWindTurbines
• LargestManufofsolarpanels
• 2%loanstobuildfactories
PV in China
• Costofcapital• Laborrate• Costofrawmaterials• PermicngandEnvironmental
TotalcostadvantagewithidenUcaltechnology~30%
Basic Science; US Dominates
Balance of Trade??
Can Silicon PV be Manufactured in US Silicon is >80% of PV market,
but US trails Asia/Europe
Source: Photon International
1366 Strategy in Cell Making
• SellEquipment
• PartneredwithRENA,globalleaderinwetprocessingforPV,basedinGermany
• FirstproductlaunchscheduledforSept2010
U.S. In Manufacturing: The Bigger Picture
Restoring American Competitiveness Gary Pisano and Willy Shih Harvard Business Review, July-Aug 2009.
• Decades of outsourcing manufacturing has left U.S. industry without the means to invent the next generation of high-tech products that are key to rebuilding its economy”
• Industrial Commons: the collective R&D, engineering, and manufacturing capabilities that sustain innovation
Summary
• LotsofUSinnovaUoninPV• USmaybeabletosecureaposiUoninPVmanufacturingequipment
• Incurrentenvironment,AsiawilldominatemanufacturingofPVproducts.
• Economistsneedtotakeintoaccountcollateraldamageofmovingmanufacturingoffshore.
• Lossofsupplychainjobs.• Lossofindustrialcommons.