Photovoltaics for the Terawatt Challenge

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1 Photovoltaics for the Terawatt Challenge Christiana Honsberg Department of Electrical Computer and Energy Engineering Director, QESST ERC Arizona State University

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Photovoltaics for the Terawatt Challenge. Christiana Honsberg Department of Electrical Computer and Energy Engineering Director, QESST ERC Arizona State University. Outline. Terawatt Challenge What is it? Photovoltaics for the TW challenges Importance of rapid growth - PowerPoint PPT Presentation

Transcript of Photovoltaics for the Terawatt Challenge

  • *Photovoltaics for the Terawatt ChallengeChristiana Honsberg Department of Electrical Computer and Energy Engineering Director, QESST ERC Arizona State University

  • OutlineTerawatt ChallengeWhat is it?Photovoltaics for the TW challengesImportance of rapid growthRecent milestones in PVBut what about .. Myths of photovoltaics: land area; efficiency; energy payback time; materials availability; time to impact; duck curves, etcFuture prospectsEducationASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

  • Terawatt ChallengeTerawatt Challenge: Encapsulates the dichotomy surrounding energy essential for improved quality of life, but also tied among the most serious global challenges.

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg **

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

  • Terawatt ChallengeWhy is compound annual growth rate important?ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg **

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

  • Terawatt ChallengeIn the nearly two decades since the TW challenge paper, renewables have reached multiple milestones In US, renewable compound annual growth rate 4.8% from 2000-2012 (NREL data) ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg **NREL,2012 Renewable Energy Data Book

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

  • Photovoltaic MilestonesGermany, Spain, Italy have yearly installed PV capacity > yearly increase in electricity demand.In Germany, PV is 50% of summer peak electricity demandASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg **

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

  • Learning Curves for PhotovoltaicsASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg **PV learning curves show compound annual growth rate (CAGR) of ~30% over the last several decadesExtending the growth rates shows ability of PV (renewables more generally if these are included) to make a substantial impact on electricity generations

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

  • Potential for PV in the US

  • Photovoltaic MilestonesASU reached 50% of total electricity supplied by PVASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg **

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

  • Arizona ContextASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg **

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

  • Photovoltaics FAQEnergy payback timeLand useCostWhat do you do at night for power? Materials availabilityFor silicon, limitation is silver in grids, which cause a limitation at 2 TWAvailability subject to efficiency, thickness

    APS Tutorial Nanostructured Photovoltaics C. Honsberg **

    APS Tutorial Nanostructured Photovoltaics C. Honsberg *

  • Duck CurvesPower after sun goes down a concern for utilities.Can mitigate by load management.ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg **

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

  • PV for the Terawatt ChallengeASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg **PV technology must be high efficiency, efficient use of materials, scalable, reliable, and enable path for future improvements High efficiency; overcome limits; thin

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

  • Present State of PV: efficiencies

  • APS Tutorial Nanostructured Photovoltaics C. Honsberg * Fraction of Efficiency Achieved

    APS Tutorial Nanostructured Photovoltaics C. Honsberg *

  • Types of PV Systems

    Optical configuration of photovoltaic systems: One-sun or flat plate; concentrating systems; tracking

    APS Tutorial Nanostructured Photovoltaics C. Honsberg **

    APS Tutorial Nanostructured Photovoltaics C. Honsberg *

  • Scope of QESST ERC

  • APS Tutorial Nanostructured Photovoltaics C.Honsberg *Multiple Junction (Tandem) Solar CellsConcentration or stacking multiple solar cells increases efficiencyTo reach >50% efficiency, need ideal bandgap 6-stack tandem, (assuming ~75% of detailed balance limit).Hard to get compatible materials with the right bandgaps.

  • APS Tutorial Nanostructured Photovoltaics C.Honsberg **What do efficiency calculations tell us?Approaches to high efficiency:Concentrate sunlight. One sun = 1kW/m2, max concentration ~46,000.No entropy penalty for concentrating sunlight, but etendue limits to acceptance angle and concentration.Optically split solar spectrum (i.e. tandem)No entropy penaltyEfficiency controlled by existence of materialsBeneficially circumvent one of the assumptions in thermodynamics

    APS Tutorial Nanostructured Photovoltaics C.Honsberg *

  • APS Tutorial Nanostructured Photovoltaics C.Honsberg**Tandem Solar CellsKey issue for III-Vs: need precisely controlled band gaps which are lattice matchedMissing low band gap materialApproaches:Lattice matched; Ge-GaAs-GaInPMetamorphic;Ge-GaInAs-GaInPMetamorphic; GaInAs-GaAs-GaInPBand gaps for 4-tandem are poorly lattice matched;5 band gaps and six band-gaps are better matched

    APS Tutorial Nanostructured Photovoltaics C.Honsberg*

  • APS Tutorial Nanostructured Photovoltaics C.Honsberg**Ge-based tandem solar cells

    Metamorphic solar cell reached 40.7% at ~200X.

    APS Tutorial Nanostructured Photovoltaics C.Honsberg*

  • Carrier-Selective ContactsCarrier-selective contacts enable ideal VOC*

  • CSC Implementation: a-Si/c-Si solar cellDemonstrated 746 mV on 50 m wafers*

  • APS Tutorial Nanostructured Photovoltaics C.Honsberg**InAs QDs on GaAsSb barriersInAs QDs achieved on GaAsSb materialIncreasing Sb composition decreases QD size and increases QD densityInAs QDs on GaAs (5 ML) / GaAs1-xSbx (5nm) buffer layers with x = 23%, with density 2.6 x 106 cm-2InAs QDs on GaAs

    APS Tutorial Nanostructured Photovoltaics C.Honsberg*

  • Experimental GaAsSb/InAs QD materialDoping of QD layers to control occupancy of the QD.GaAsSb/GaAs interface

  • APS Tutorial Nanostructured Photovoltaics C.Honsberg **Tandem Solar CellsMonolithic III-V tandem solar cells; Series connected; three junctionsHigh efficiency used in high concentration, two-axis tracking systemsHigh concentration means small area (and lower cost) needed for solar cellsTrade balance of systems and solar cell cost.

    APS Tutorial Nanostructured Photovoltaics C.Honsberg *

  • Experimental GaAsSb/InAs QD material

  • ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg **Path for Continual ImprovementIdeal solar cell consists of a light-trapped, thin solar cellNanostructured surfaces allow light trapping and advanced concepts (e.g., multiple exciton devices)

    ASU-UA-NAU Student Solar Conference 04/01/2014C. Honsberg *

  • Student Led Pilot LineSilicon pilot line capabilities for interaction among students, industry and researchers10 Fulton Undergraduate Research Initiative Projects2 honors thesis4 capstone projects

  • ASU-UA-NAU Student Solar Conference 04/01/2014 C. Honsberg **

    Questions?

    ASU-UA-NAU Student Solar Conference 04/01/2014 C. Honsberg *

    *QESST Second Site Visit - Overview*****Shouldnt the external contacts contact the fermi levels.In the diagram, the inversion is too strong

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