GCEP RESEARCH SYMPOSIUM 2012 STANFORD, CA. Sally M. Benson. Director, Global Climate and Energy Project Stanford University OCTOBER 10, 2012

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1 May 15-16, 2013 Research at GCEP in: Solar Energy and Photocatalysis GCEP RESEARCH SYMPOSIUM 2012 STANFORD, CA Sally M. Benson Director, Global Climate and Energy Project Stanford University Bruce Clemens Stanford University OCTOBER 10, 2012 GLOBAL CHALLENGES GLOBAL SOLUTIONS GLOBAL OPPORTUNITIES

2 World Power Sources, Solar Power Potential Nuclear Hydro Coal Solar Power Potential Hitting 3% of the Earth s Land Harvested with 15% Efficiency Natural Gas Oil

4 USA Solar Power Resource To make our 11,300 Watts, each person needs a PV array about 60 feet on a side The stuff had better be cheap! - and abundant

5 On-Campus House PV System 3.1 kw Peak, Grid-tied system

6 Levelized cost of electricity Cost per area Solar Electricity Economics Cell LCOE = Total life cycle cost Total lifetime energy production Balance of System Installation Price of electricity Lifetime of system Effective fraction of time at full solar power Efficiency Power density from sun Cell cost includes: Cell material Cell manufacture Deposition or material synthesis Processing Contacts, anti-reflection, texturing, etc. Balance of system cost includes: Encapsulation Module wiring Frame and mounting hardware Installation cost includes labor for installation, maintenance, etc. Cost of the cell is only one component Even with free cells solar electricity has a substantial cost Efficiency, lifetime and sunshine drive all costs

and electron quickly relax to band edges, giving off heat (called thermalization) Photon energy great than the band gap

7 PV Cell: Solar Cell Efficiency Shockley-Queisser Limit Conduction Band Sbyrnes321 Wikimedia E g Valence Band Only light with photon energy greater than the band gap will create excited carriers Light with lower photon energy is lost Hole and electron quickly relax to band edges, giving off heat (called thermalization) Photon energy great than the band gap is lost GCEP Programs with aims to: Come as close as possible to this limit Exceed Shockley-Queisser limit with new approaches

Solar Cells Using Non-Toxic, Abundant Materials Photovoltaics (solar cells) are strong candidates for meeting future energy needs, but costs are still too high.

8 Solar Cells Using Non-Toxic, Abundant Materials Photovoltaics (solar cells) are strong candidates for meeting future energy needs, but costs are still too high. CuInGaSe 2 ~ 20% efficient thin film architecture Cu 2 ZnSnS 4 (CZTS) ~11.1 % record (Mitzi) 1.45 ev E g Material properties are similar to CZTS, so are similar efficiencies possible? Cu Sn Zn S Raw Material Costs Cu - $3.35/lb Zn - $1.59/lb Sn - $6.61/lb S $0.02/lb Ga - $209/lb In - $361/lb Se $4, 2007 $33/lb Relative Abundance Cu x 10-5 Zn x 10-5 Sn x 10-6 S Ga x 10-5 In x 10-7 Se - 5 x Source: (2007 data)

# of Papers CZT(S,Se) Efficiency vs. Time CZTS Progress # of CZTS Papers vs. Time 35 30 25 20 15 10 5 IBM World Record 11.

9 # of Papers CZT(S,Se) Efficiency vs. Time CZTS Progress # of CZTS Papers vs. Time IBM World Record 11.1% AQT-Stanford Record 9.3% CZTS research base growing fast Publication Year 9 Vardaan Chawla Clemens Group

10 Spatially Engineered Delamination Layers (SEDL) for Creating Inexpensive and Scalable Single-Crystal Semiconductor Thin Films Bruce M. Clemens, Garrett Hayes and Alberto Salleo Department of Materials Science and Engineering, Stanford University Glass Epoxy Epitaxial semiconductor film SEDL Single crystal wafer High performance of single crystal solar cells Low cost and low embedded energy of thin film solar cells Glass Epoxy Epitaxial semiconductor film SEDL Single crystal wafer

11 Delaminated Epitaxial Si Films Epitaxial Si films adhered to glass support substrates, and the growth substrate from which they were separated

12 MSE Solar Cells, Fuel Cells and Batteries: Materials for the Energy Solution Old Format Standard in-class lecture format Weekly problem sets One in-class, problem-based exam Undergraduates have five labs (with reports) and final lab project (build a battery) Graduates have final (800 word) paper Issues Diversity of background and levels leads to pace issues Half the students are lost and half are bored Background material would be helpful to equalize Problem sets are challenging for non-engineers Large class makes it difficult to give individual attention

13 New Flipped Class Format Course offered free to the world as a Massively Open Online Course (MOOC) Post recorded lectures on-line with Stanford organization Class2Go Low-cost, low-production, short-segment lecture format On-line homework and final exam Piazza forum for student discussions Separate forum for on-campus and remote students Over 12,000 students signed up from around the world Additions for Stanford Campus Students: During regular lectures times Guest speakers Problem sessions - team-based active problem solving Extra lectures Question and answer session Undergraduates laboratory section with hands-on experiments Graduate final project presented in poster sessions with peer evaluation

14 Educational Background of On-Line Students Signed Up Completed Elementary HighSchool MastersOrProfessional Associate Middle Bachelors Doctorate Other

15 Wide Range of Student Ages

16 Students from Around the World Page Views 1. United States 33, Spain 8, India 7, Germany 3, Canada 2, Columbia 2, United Kingdom 2, Brazil 2, Ukraine 2, Australia 1,824

17 Stanford MSE 256: Solar Cells Fuel Cells and Batteries Will be Offered as a MOOC in Fall of 2013 Offered through Stanford and the EdEx Platform Free to Anybody, Anywhere Sign up on line Solar.class.stanford.edu

19 Thank You!

Photovoltaic Technology. Topics for this lecture

Photovoltaic Technology. Topics for this lecture Photovoltaic Technology How to produce electricity directly from the sun Lecture prepared with the able assistance of Chris Polashenski, TA Topics for this lecture How does PV work AC/DC and inverters