The Role of Photovoltaics in Our Energy Future - PowerPoint PPT Presentation

1 / 35
About This Presentation
Title:

The Role of Photovoltaics in Our Energy Future

Description:

'Legend' suggests Cd in Size AA NiCd battery about same as 50 Watt panel ... Plus, lots of Cd-plated hardware (nuts, bolts, fixtures)! Cadmium Issues ... – PowerPoint PPT presentation

Number of Views:243
Avg rating:3.0/5.0
Slides: 36
Provided by: nrel
Category:

less

Transcript and Presenter's Notes

Title: The Role of Photovoltaics in Our Energy Future


1
The Role of Photovoltaics in Our Energy Future
  • Tracie J. Berniard
  • National Renewable Energy Laboratory
  • tracie_berniard_at_nrel.gov

2
Overview
  • The National Renewable Energy Laboratory
  • Opportunities for Renewables
  • The issue of cost
  • Next generation PV Thin Films
  • CdTe thin film PV Laboratory vs. Manufacturing
  • Looking Ahead

3
National Renewable Energy Laboratory
(NREL)Golden, CO
  • Biomass
  • Wind
  • Geothermal
  • Hydrogen and Fuel Cells
  • Advanced Vehicles and Fuels
  • Others
  • Photovoltaics NCPV (materials device
    development, measurements characterization,
    etc)
  • www.nrel.gov

4
Opportunities for Renewables
11/2000
  • CO2 emission levels
  • Rising energy costs
  • Population growth and developing nations
  • Fossil fuel age WILL end

5
Opportunities for Renewables
  • In 1999 U.S. CO2 gas emissions were 5.6 billion
    tons, up 28 from 1983.
  • Nearly 99 of this total was energy-related
    emissions.
  • AEO2001 projects 7.5 billion tons of gas in 2020
  • source www.eia.doe.gov

6
Opportunities for Renewables
  • Despite gains in energy efficiency, demand for
    energy is expected to rise due to world
    population growth

World Population by 2050 9 billion
source www.pbs.org/wgbh/nova/worldbalance
7
Opportunities for Renewables
  • Energy consumption in U.S. outweighs our
    production
  • Largest consumed sources are petroleum, natural
    gas and coal

source www.eia.doe.gov
8
Opportunities for PV
  • Renewables make up smallest percentage (6)
  • Of global PV demand, U.S. only 15, and we export
    70 of PV we produce.
  • The earth receives more energy from the sun in 1
    hr than the world uses in a yr

Based on 2002 data www.eia.doe.gov
9
Opportunities for PV
  • Quotes from the U.S. Energy Outlook as of 2001
    Report
  • Many experts believe that the age of fossil
    fuels is only an interlude between pre- and
    post-industrial eras dominated by the use of
    renewable energy.
  • The far future seems likely to belong to
    renewable sources of energy.
  • www.eia.doe.gov

10
The Issue of Cost
  • Lowest priced (module only) solar modules to
    date
  • Crystalline Si 3.20/Wp (Kyocera, U.S.)
  • 18/kWh in S. California
  • Thin Film a-Si 3.59/Wp (Kaneka, Germany)
  • 20/kWh in S. California

Module only
source www.solarbuzz.com
11
The Issue of Cost
Cost Trends for Entire PV System
  • First Solar is selling their modules in Europe
    now for 2.10/Wp (large quantities).
  • BOS 1/Wp
  • System 3/Wp

source www.solarbuzz.com
12
PV Physics Review
Dark
Vmp
FF
Jmp
Voc
Jsc
Light
Fill Factor, FF (VmpImp)/VocIsc Efficiency, ?
(VocIscFF)/Pin
13
PV Physics Review
  • p-n junction
  • built-in potential
  • any e-h pairs created within or near the
    depletion region will contribute to the
    generated current

14
PV Physics Review
  • Decrease Eg, absorb more of the spectrum
  • But not without sacrificing output voltage
  • CdTe and GaAs ideally suited

15
Next Generation PV Thin Films
  • Strong light absorbers (a 105/cm), so need less
    materials (1-2?m for CdTe)
  • Large area fabrication high volume
    manufacturing
  • However, complex materials systems
  • Key technologies a-Si, CIGS and CdTe

16
(No Transcript)
17
CdTe Thin Film PV
Standard NREL Laboratory CdTe Devices
p-n junction formation
SnO2 coated 7059 5000Ã…
CBD CdS 800Ã…
CSS CdTe 8-10?m
post-processing treatments
V-CdCl2
DAGCu Ag Backcontact
Chemical Etch
Gets routine devices of 12-14
18
CdTe Thin Film PV
Superstrate Structure
19
CdTe Thin Film PV
J. Sites, CSU, based on optical data
20
CdTe Thin Film PV
  • Highest achieved laboratory efficiency to date is
    16.5 (Wu et al., NCPV Program Review, 2001)
  • Some key advances in processing
  • Vapor-CdCl2 treatment / ZTO buffer layer
  • Backcontact (Cu)
  • CTO transparent front contact

21
CdTe Thin Film PV
  • CdCl2 post-deposition treatment gives better cell
    efficiency
  • Elimination of fast-recombination centers in
    the CdTe film
  • Reduction of recombination centers at the
    junction
  • Elimination of small grains at the the grain
    boundaries

Ref Doug H. Rose et al., Prog. Photovolt Res.
Appl. 7, 331 (1999)
22
CdTe Thin Film PV
  • Solution CdCl2 meant that an etch was necessary
    to remove surface contamination left behind

AFM images of CdCl2 Treated CdTe surfaces
Vapor CdCl2
Solution CdCl2
Y. Mahathongdy, M.S. Thesis, Colorado School of
Mines, 1999
23
CdTe Thin Film PV
  • Rollover
  • Rs

24
CdTe Thin Film PV
  • Nitric Phosphoric (NP) Etched Device
  • Te-rich layer believed to improved backcontact
    Cu2Te?
  • Penetration down grain boundaries reason for
    thick CdTe

25
CdTe Thin Film PV
Thinner CdTe Possible
  • Zn2SnO4 (ZTO), buffer layer can improve Rsh
  • - Reduces probability of forming TCO/CdTe
    junction when CdS thinned
  • - Can act as an etch-stop during backcontact
    formation
  • Less aggressive etches being studied

Ref X. Wu et al., 26th IEEE PVSC, 347, 1997
26
CdTe Thin Film PV
  • Cadmium stannate (CTO), Cd2SnO4, can replace SnO2
    as transparent front contact (TCO)
  • (CTO), resistivity ? 1.5x10-4 ?-cm two-six
    times smaller than SnO2 ? 8.6x10-4 ?-cm? lower
    Rs, i.e. improved FF

Ref X. Wu et al., 26th IEEE PVSC, 347, 1997
27
CdTe Thin Film PV
  • Laboratory vs. Manufactured Devices
  • First Solar, Inc. www.firstsolar.com
  • Module efficiency 9 (device 14) - scale up
    issue
  • Differences in processing
  • High-rate vapor transport deposition (HRVTD)
    for CdTe RD 100 Award with NREL

28
CdTe Thin Film PV
  • Laboratory vs. Manufactured Devices

Patent 5,945,163
  • Implemented 2002, and has been able to produce
    2.10/Wp modules
  • Second generation now under construction, aim of
    1/Wp modules

29
Future Direction of Thin Film PV
  • Engineered Devices Process Control
  • Substrate Structure and Flexible Substrates
    (metal foil, polymers)

30
Future Direction of Thin Film PV
  • Building Integrated Products
  • Niche Consumer and Military Markets
  • Infrastructure Distributed vs. Centralized PV
    power

31
PV Future Bright
  • U.S. huge untapped market
  • On-going research (thin film and others)
  • Import Renewables?

32
PV Future Bright
RPS Becomes Official in Maryland
Uni-Solar Receives Order for 2.4 MW of Thin-Film
France-Based Solar Plant Triples PV Capacity
Solar Photovoltaics for U.S. Missile Defense
Solar power will bring light to rural bus stops
  • Sharp Readies to Boost Solar PV Production

Solar Energy Powers Equestrian Trails
33
Summary
  • Renewables, including PV, are the future of
    energy
  • PV currently selling for 4.92/Wp avg total
    system cost, goal 1.50-2.00/Wp
  • Thin film PV is likely next generation solar
    technology to get us there
  • Thin film PV industry is in its infancy, with new
    materials and manufacturing advances to come

34
(No Transcript)
35
Cadmium Issues
  • How Much Cadmium is There in a 50 W Module?
  • 3 µm thick CdTe, 2-foot x 4-foot module
  • 0.0003 cm x 24 (2.54 cm/) x 48 (2.54 cm/)
    2 cm2 (14 gms CdTe)
  • But, only half of this is Cd, so 7 gm/50 Watt
    panel 1 Cd unit
  • Typical household installation 3000 Wpeak 60
    (50 Watt panels) 60 Cd units
  • How does this compare to other consumer items?
    (Example My house)
  • Legend suggests Cd in Size AA NiCd battery
    about same as 50 Watt panel
  • 8 Size D Batteries (32 Cd units)
  • 4 Power tool batteries (16 Cd units)
  • 2 Laptop batteries (8 Cd units)
  • 6 Cordless phone battery packs (12 Cd units)
  • 2 Cell phone batteries (4 Cd units)
  • Total 72 units of Cd.
  • Plus, lots of Cd-plated hardware (nuts, bolts,
    fixtures)!
Write a Comment
User Comments (0)
About PowerShow.com