calculation of energy payback time of pv - … · calculation of energy payback time of pv and its...

Calculation of energy payback time of PV

and its determinants

Hans-Joerg Althaus PhD

LCA expert / scientific coordinator

[email protected]

Presentation at the Swiss Photonics Workshop

Dübendorf, October22th 2013

mailto:[email protected]





3 H.J. Althaus, Swiss Photonics Workshop, Dübendorf 22nd 2013

The principle of Energy payback time calculation

𝐸𝑃𝐵𝑇 𝑦𝑒𝑎𝑟𝑠 =

𝑃𝑟𝑖𝑚𝑎𝑟𝑦 𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑛𝑣𝑒𝑠𝑡𝑒𝑑 𝑖𝑛 𝑃𝑉 𝑠𝑦𝑠𝑡𝑒𝑚

𝑃𝑟𝑖𝑚𝑎𝑟𝑦 𝑒𝑛𝑒𝑟𝑔𝑦 𝑠𝑢𝑏𝑠𝑡𝑖𝑡𝑢𝑡𝑒𝑑 𝑏𝑦 𝑃𝑉 𝑠𝑦𝑠𝑡𝑒𝑚 𝑝𝑒𝑟 𝑦𝑒𝑎𝑟


𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 𝑖𝑛𝑣𝑒𝑠𝑡𝑒𝑑 𝑖𝑛 𝑃𝑉 𝑠𝑦𝑠𝑡𝑒𝑚

𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 𝑠𝑢𝑏𝑠𝑡𝑖𝑡𝑢𝑡𝑒𝑑 𝑏𝑦 𝑃𝑉 𝑠𝑦𝑠𝑡𝑒𝑚 𝑝𝑒𝑟 𝑦𝑒𝑎𝑟

or


Definition of “primary energy”

• Energy embodied in natural resources prior to undergoing any

human-made conversions or transformations.

• Energy contained in raw fuels, and other forms of energy received as

input to a system.

• Can be non-renewable or renewable.


What is the “primary energy” of different sources?

• Fossil fuels: lower or upper heating value

• Natural Uranium: various methods

• Substitution: how much primary fossil energy would be needed to

produce the same amount of electricity?

• Average thermal efficiency of nuclear power plant (ca. 32%)

• Energy content in fissile isotope (considering remaining fissile

isotopes in nuclear waste or not)

• Solar: various methods

• Irradiation

• Harvested (by PV (cell, module or system) or thermal collector)

Value choice introduces ambiguity. Differences up to one order of magnitude!

Important to choose consistent values for

all energy sources! Important to compare only EPBT values from different studies if they are consistent!






1) For production, use and end of life but without solar irradiation on PV

modules during use phase

1)


How to calculate primary energy invested in PV system?

chain of production

LCA

9

Life Cycle Model

H.J. Althaus, Swiss Photonics Workshop, Dübendorf 22nd 2013

Goal definition

Cumulative

Life Cycle Inventory

System per

functional

unit

Resources Emissions

Life Cycle Inventory

Disposal

Use

Production

Resources

Energy

Emissions

Waste

Product Materials

Discussion Life Cycle Impact

Assessment

How to do life cycle assessment?

LCA (ISO 14’040)


Model of the Product system of PV power generation

Reference

function


Production of PV cells (thin film Si)

Glass

ZnO

Electricity


Influence of production location

0%

20%

40%

60%

80%

100%

120%

Electricity,Switzerland

Electricity,Europe

Electricity,China

CED Non-renewable


Product system of PV power generation

Reference

function

Central Europe 100% South Europe 170%


Ambiguities in LCA (of PV system)

• System boundaries

• Cut-off criteria

• Inclusion of infrastructure

• Inclusion of R&D

• Principles for modeling multi-functionality of systems

• Data sources

• Choice of background data


Energy payback time; principle




1) For production, use and end of life but without solar irradiation on PV

modules during use phase

1)


What energy is substituted by PV electricity?

Source: EEA

40

0

Sh

are

of

ele

ctr

icit

y

pro

du

ce

d b

y f

ue

l [%

]

1990 2004

Coal & lignite

Natural gas Renewables

Oil

Nuclear

Renewables

17

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Electricity,Switzerland

Electricity,Europe

Electricity,China

HydroElectricity

Windelectricity

Nuclearelectricity

UCTEnatural gaselectricity

UCTE oilelectricity

UCTE coalelectricity

CED Non-renewable [kWh/kWh] CED Total [kWh/kWh]




Examples

CED System [MJ/m2]

electricity generated [kWh/m2]

Central Europe South Europe

Crystalline Si 6500 3530 6000

mc-Si 5000 3295 5600

Ribbon-Si 3500 2940 5000

Cd-Te 1500 2235 4500

Amorpous Si 1900 2650 3800

Exemplary values in reasonable range for PV system produced in

Europe.

CED of substituted electricity from ecoinvent v2.2

Values would be ca. 20% higher

for production in China

19

0

1

2

3

4

5

6

Energy payback time [years]

Crystalline Si mc-Si Ribbon-Si Amorpous Si Cd-Te

Differences in

electricity

generated and

substituted.

No difference in

PV production


Examples

Values would be ca. 20% higher

for production in China

Value choice introduces ambiguity. Differences up to a factor of 2!

Important to choose reasonable

substitute!

20

A glimpse beyond energy

Payback of greenhouse

gasses emitted


Examples

GWP System (kg CO2-eq/m2)




mc-Si 200 3295 5600

Ribbon-Si 150 2940 5000

Cd-Te 80 2235 4500

Amorpous Si 100 2650 3800


Europe.

GWP of substituted electricity from ecoinvent v2.2

22

Differences in

electricity

generated and

substituted.

No difference in

PV production


Examples

0

20

40

60

80

100

120

140

160

CO2 payback time [years]


Value choice introduces ambiguity. Differences up to two orders of magnitude!

Important to choose reasonable

substitute!

23

Differences in

electricity

generated and

substituted.

No difference in

PV production


Examples

0

2

4

6

8

10

12

14

16

18

20

CO2 payback time [years]



Example: Influence of production location

0%

50%

100%

150%

200%

250%

300%

Electricity, Europe Electricity, China

GWP

Assumption:

GWP of PV system

produced in China is

1.5 times the GWP of

the same system

produced in Europe.


Examples

GWP System (kg CO2-eq/m2)




mc-Si 300 3295 5600

Ribbon-Si 225 2940 5000

Cd-Te 150 2235 4500

Amorpous Si 120 2650 3800


China.

GWP of substituted electricity from ecoinvent v2.2

26

Differences in

electricity

generated and

substituted.

No difference in

PV production


Examples

0

5

10

15

20

25

30

CO2 payback time [years] if PV system produced in China


27

Emissions from scale up of PV

What happens if PV

electricity generation in

Switzerland is scaled

from today 0.33 to 11

TWh in 2050?

28

0

10'000

20'000

30'000

40'000

50'000

60'000

70'000

80'000

90'000

100'000

2010 2015 2020 2025 2030 2035 2040 2045 2050 2055

GHG emitted by expansion of PV to 11 TWh in 2050 in Switzerland

GHG emitted / year [t/a]

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1GHG emitted per kWh PV electricity

kg/kWht/a


Scale-up

Worst case

Assumptions:

- C-Si

- Production

in CN

- Constant

properties

(efficiency,

GHG

intensity)

1 ‰ of Swiss emission 2011

29

Conclusions


Conclusions

• EPBT calculation is value based.

• Care has to be taken when comparing EPBT values of different

studies.

• Influence of (arbitrary) choices can be larger then differences between

PV technologies.

• GHG payback can be much longer then EPBT

• Influence of value choices on GHG payback is much bigger than on

EPBT

• GHG emissions from transition towards high solar share in electricity

generation are comparably small.

31

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32

BauxiteSheet

rolling

Door

production

New scrap to

recycling

Vehicle

door

Use phase

Old scrap to

recycling

Old scrap to

disposal

Landfill

Alu

Aluminium sheet

De-

construction

System boundary


Allocation: cut off

3 products

33

BauxiteSheet

rolling

Door

production

New scrap to

recycling

Vehicle

door

Use phase

Old scrap to

recycling

Old scrap to

disposal

Landfill

Alu

Aluminium sheet

De-

construction

System boundary


Allocation

3 products

Mass •New scrap:10%

•Car part: 0%

•Old scrap: 90%

Value •New scrap:3%

•Car part: 95%

•Old scrap: 2%

What is “right”

and why?

34

BauxiteSheet

rolling

Door

production

New scrap to

recycling

Vehicle

door

Use phase

Old scrap to

recycling

Scrap

preparation

Old scrap to

disposal

Landfill

Alu

min

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Aluminium sheet

De-

construction

Alu

Alu

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mel

tin

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Alu

min

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cas

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System boundary


Avoided allocation

1 product 2 products 3 products

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