The Environmental Impact of Solar Photovoltaic Cells

Original Presentation by J. M. Pearce, 2006Updated by A. Shahed and J.M. Pearce, 2010

Email: profpearce@gmail.com

The Energy Challenge and How to Solve it with Solar Cells

The Energy Challenge

• World population is expanding rapidly and will likely reach over ~9 billion before stabilizing

• Energy use is directly proportional to standard of living

• Energy demand is skyrocketing• Standard methods of producing energy

have a limited supply and have unacceptable impacts on the environment

The Population Explosion

• Exponential population rise with advancements in energy production and technology

• UN Projections to 2050 place population level at ~9 billion

Human Development Index

HDI: longevity (life expectancy), educational attainment, and standard of living (gross domestic product per capita)

World Energy Consumption

By Fuel Type 1980-2030

Future Energy Needs

How to Produce Electricity?

• Conversion of mechanical energy into

electricity (hydro, wind)

• Conversion of chemical energy into electricity

(coal, natural gas, etc.)

• Conversion of nuclear energy into electricity

• Conversion of photon energy into electricity

Energy Sources – Global Primary Energy Supplies

Peak Oil (U.S. Production Peak – 1970)

• Measured in 1000 barrels per day• World energy reserves and peak under

considerable debate…

U.S. and World Natural Gas Supplies

World and U.S. Coal Reserves

Even if we discover more fossil fuels….

We can not burn what we already have.

Recent Global Atmospheric Carbon Dioxide Concentration

From 1860 to 1990 the industrial nations released 185 billion tons of carbon into the atmosphere from burning fossil fuels.

Today 6 + billion tons of CO2 are released into the air every year!

380ppmv

Historical CO2 Concentration

Global Warming

This is the Consensus View

The Intergovernmental Panel on Climate Change

In 1995, over 2,500 scientists representing more than 80 countries analyzed over 20,000 articles from the relevant literature

It is now quite clear that certain gases, such as carbon dioxide, play a crucial role in determining the earth's climate by preventing heat from escaping the atmosphere.

Temp. gains up to 14oF!!!

• In 50 years Earth will be ~3-5 degrees hotter

• Up to 14 ft rise in global sea levels. (3ft floods Florida & NYC)

• Weather patterns disrupted: droughts in some places and torrential rain in others – disturbing agricultural production.

• EPA estimates that by 2050 the southern boundary of forest ecosystems could move northward by 600km.

• Massive forest death and species extinction.

Potential Consequences :Manageable to Catastrophic

Global Temperatures for Various Growth Scenarios

Solar Photovoltaic Energy as a Solution to the Energy Challenge

Environmental Benefits• During use PV produces no :atmospheric emissionsradioactive waste• During use PV produces no

greenhouse gases so it will help offset CO2 emissions and global climate destabilization

– PV does have an embodied energy and embodied CO2 emissions

• PV curtails air pollution, which produces acid rain, soil damage, and human respiratory ailments.

Environmental Benefit of a 4 kWp PV system

This solar energy array would prevent: • 2.4 tons of coal from being burned• 6.2 tons of CO2 = decreasing the greenhouse

effect• over 3,600 gallons of water from being used• ~34 pounds each of NOx and SO2 from

polluting the atmosphere• 1.8 pounds of particulates from causing a

health hazard (and no nuclear waste)

EACH YEAR - FOR 30+ YEARS!

Busting PV Related Myths

Myth 1: PV use more energy to

make than they produce over their lifetime

For cells in production now the energy payback is between 6 months and 5 years!

Net Energy for 1kW-hr invested in PV Roof in Detroit, MI

Time (Years)

0 1 2 3 4 5 6 7 8 9 101112131415161718192021222324252627282930

Net

Ene

rgy

(kW

-hrs

)

-1

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15 c-Si Lowc-Si Highp-Si Lowp-Si Higha-Si Lowa-Si High

14+breeds

Built in PV

Integrated into the roof.Integrated into an awning

over a back porch California, generates electricity while shading the family's outdoor activities

Additional BIPV

Solar Shingles

• Various styles of PV shingles are available

• Solar Shingles are rated at 17W• Lightweight and Flexible• 20 year warranty on power output

Aesthetic Applications

• A Canadian team fashioned a window with solar electric cells and a motif of autumn leaves

• Semi-Transparent and

Transparent PV cells

• Building Integration

Myth 2: There is Not Enough

Land• Each day the sun casts more

energy on the earth than all people would consume in 27 years

• The entire world’s energy needs could be provided by ½ the area of the Gobi desert covered with PV.

What about in the USA?

• 100 miles by 100 miles in Nevada would

provide the equivalent of the entire US

electrical demand

• Distributed (to sites with less sun) it would

take less than 25% of the area covered by US

roads.

6 Boxes at 3.3 TW Each

Solar Cell Land Area Requirements for the World’s

Energy with Solar PV

Solar Cells• PV cells can provide a

substantial portion of energy needs.

• For the US, only 3% of the land area would be required using 1999 efficiency measures

• PV technology is improving continuously

• Greater efficiencies• Lower costs

Myth 3: We do not have Enough Raw

Materials • Si - 2nd most abundant element in

Earth’s crust

• The amorphous silicon cells manufactured from one ton of sand could produce as much electricity as burning 500,000 tons of coal.

• Philadelphia home

Solar Photovoltaics is the Future

• Photovoltaic technology provides an effective means of supplying clean energy

• The technology is ready to use and proven• There is extensive research and development

providing opportunities for higher efficiencies and new market players

• Abundant silicon resource• Will play a major role in tackling our increasing energy

needs and curbing our GGH emissions

Acknowledgements

• This is the fifth in a series of presentations created for the solar energy community to assist in the dissemination of information about solar photovoltaics.

• This work was supported from a grant from the Pennsylvania State System of Higher Education.

• The author would like to acknowledge assistance in collecting information for this presentation from Heather Zielonka.