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Photovoltaics

A one-kilometre square field of photovoltaics could generate an incredible 385 million kWh of energy.1 That is enough to power some 20,000 homes.2 However, can photovoltaics provide us with enough energy to replace our existing fossil fuel power plants?

What Are Photovoltaics?

Photovoltaics actually describes the process of converting light into electricity at an atomic level.3 This is made possible by some very special materials that have a property known as the photoelectric effect.4 This means that, as photovoltaics absorb photons of light, they also release electrons.5 These electrons are then captured to form an electric current that can be used to power anything from mobile phones to satellites.6 The exact amount of energy photovoltaics can generate depends on the amount of light striking their surface and how efficient they are at converting light into electrical energy. Currently, the most cost-effective photovoltaic systems convert between 14% and 20% of the energy contained within the light into electricity.7 However, there are systems on the market that convert as much as 45% of the light into electricity.8 These panels are extremely expensive though, and are mainly used by organisations such as NASA.9 Currently, photovoltaics produce less than one one-thousandth of the world’s energy demand.10 Nevertheless, photovoltaics have the potential to produce an incredible 470 PWh.11 That’s more than four times the world’s current energy demand.

What’s Good About Them?

  • The energy source has huge global potential.
  • They are less visually intrusive than other devices.
  • They require limited amounts of maintenance.12
  • They operate without making any noise.13

What’s Bad About Them?

  • The energy supply is intermittent as there is no sunlight available during the night.14
  • Cloudy weather can affect energy yields.15
  • They can be expensive in areas that have limited sunlight.16

How Much Area Do We Need?

Incredibly, less than 1% of the United States would need to be covered with photovoltaics in order to meet the country’s energy demand.17 Furthermore, even factoring in the UK’s legendary cloud cover, less than 4% of the land would need to be covered with photovoltaics in order to meet the country’s energy demand.18

Map showing the land area of the United States of America that would have to be covered with photovoltaics in order to meet the country's energy demand.

What Impact Do They Have on the Landscape?

There is the potential to build photovoltaic arrays that cover several hundred kilometres of land. However, because photovoltaic panels are only ever a few metres tall, even arrays of this magnitude would have almost no visual impact at eye level. What’s more, planting can be used along the boundaries to screen the arrays. When this is combined with the fact that photovoltaic arrays don’t make any noise, most passers-by won’t even realise the arrays are there.

From the air, photovoltaic arrays will be clearly visible. However, at ground level, they will be hardly noticeable.

Where Are Photovoltaics Best Located?

Photovoltaics work best when they are located in countries that benefit from lots of sunlight such as the countries found within Africa, the Middle East and Australia. In fact, in these locations, they can be three times more cost effective than they are in northern Europe.19

How Do They Perform?

Energy PriceLife SpanEnergy per KM²
¢8/KWH2030 YRS21300 GWH/YR22

Economic OffsetEnergy OffsetWorld Potential
12 YRS237.5 YRS24470 PWH25

How Do They Rate?

Value for Money|★ ★ ★ ★ ★
Reliability|★ ★ ★ ★ ★ ★
Eco-friendliness|★ ★ ★ ★ ★ ★
Global Potential|★ ★ ★ ★ ★ ★
Overall|★ ★ ★ ★ ★

Photovoltaics in a Nutshell

To summarise, photovoltaics provide a cheap source of energy that has the potential to meet all of the world’s current energy demand. What’s more, photovoltaics don’t require much land, they don’t make any noise and they have minimal visual impact. Despite all the positives, photovoltaics can only produce energy during the day and yields are significantly reduced in cloudy weather. However, we can get around this by combining photovoltaics with other renewable energy sources and by storing some of the energy photovoltaics generate during the day. When it comes to generating energy from the sun though, photovoltaics are not the only option available to us. Why not find out what solar thermal plants have to offer by clicking the link below? Alternatively, find out other ways we can stop climate change by returning to the main menu.

Image Credit

Title image taken by dvoevnore and reproduced under license from Adobe Stock.

United States map created by SUPER RADICAL.

Image of photovoltaic farm taken by abriendomundo and reproduced under license from Shutterstock.

World map created by SUPER RADICAL. World map based on all areas that receive more than 1,800 kWh of sunlight except for any areas that are covered with forests, cropland, mountains or significant quantities of ice. Irradiation information sourced from SolarGIS – ‘Global Horizontal Irradiation’ – Map. Cropland cover based on 2000 data and sourced from Columbia University Center for International Earth Science Information Network – ‘Croplands, 2000: Global’. Areas of forest cover sourced from Food and Agriculture Organization of the United Nations – ‘Global Forest Resources Assessment 2005, Progress Towards Sustainable Forest Management’ – Page 15. Areas of mountain and ice cover sourced from Koistinen, Ville – ‘The Main Biomes in the World’ – commons.wikimedia.org.

General Notes

All figures presented in this section are estimates based on best available data, assume optimum locations, and, wherever possible, are based on comparable studies. That said, many of the studies assume different economic conditions, climatic conditions, time frames and locations. Furthermore, the technologies discussed in this section are in a constant state of development. As a result, the figures presented within this section provide a rough guide only and should not be viewed as a definitive performance level.

For the total world energy demand, a figure of 104.4 million GWh has been used. The figure is based on 2012 data and sourced from International Energy Agency – 'World Balances for 2012' – www.iea.org.

All UK to USA currency conversions have been set at $1.656 USD for each £1 GBP. The figure is based on the conversion rate as of the 1st January 2014 and sourced from XE – 'XECurrency Table: USD - U.S. Dollar' – www.xe.com.

Article Endnotes

  1. Based on photovoltaic cells having an efficiency of 20%, 2,800 kWh of sunlight striking each square metre of the Sahara desert per year and photovoltaic cells covering 75% of each square metre exposed desert. Amount of sunlight striking the Sahara Desert sourced from SolarGIS – ‘Global Horizontal Irradiation’ – Map. Figure includes losses of 2% due to power conditioning and 6.5% due to transmission and distribution. Power conditioning losses based on data sourced from Fuji Electric – ‘Large-scale Photovoltaic Power Generation Systems’ – Page 7. Transmission and distribution losses based on 2007 data for the United States and sourced from United States Department of Energy – ‘Frequently Asked Questions – Electricity’ – tonto.eia.doe.gov.
  2. Based on a UK home using an average 18,738 kWh of energy in 2014. Sourced from UK Department of Energy and Climate Change – ‘Energy Consumption in the UK’ – Page 7.
  3. Knier, Gil – ‘How Do Photovoltaics Work?’ – science.nasa.gov.
  4. Knier, Gil – ‘How Do Photovoltaics Work?’ – science.nasa.gov.
  5. Knier, Gil – ‘How Do Photovoltaics Work?’ – science.nasa.gov.
  6. Knier, Gil – ‘How Do Photovoltaics Work?’ – science.nasa.gov.
  7. Thomas, David – ‘Which Solar Panel Brand Is Best? How Much Should I Expect to Pay?’ – www.theecoexperts.co.uk.
  8. Thomas, David – ‘Which Solar Panel Brand Is Best? How Much Should I Expect to Pay?’ – www.theecoexperts.co.uk.
  9. Thomas, David – ‘Which Solar Panel Brand Is Best? How Much Should I Expect to Pay?’ – www.theecoexperts.co.uk.
  10. Based on 2012 data sourced from International Energy Agency – ‘World: Renewables and Waste for 2012’ – www.iea.org.
  11. Hoogwijk, Monique and Graus, Wina – ‘Global Potential of Renewable Energy Sources: A Literature Assessment’ – Page 39. Please note, figure does not include power conditioning, distribution and transmission losses.
  12. Maehlum, Mathias Aarre – ‘Solar Energy Pros and Cons’ – energyinformative.org.
  13. Maehlum, Mathias Aarre – ‘Solar Energy Pros and Cons’ – energyinformative.org.
  14. Maehlum, Mathias Aarre – ‘Solar Energy Pros and Cons’ – energyinformative.org.
  15. Maehlum, Mathias Aarre – ‘Solar Energy Pros and Cons’ – energyinformative.org.
  16. Based on less sunlight resulting in a smaller energy yield and therefore increasing the cost of each unit of energy generated.
  17. Based on the United States of America having a total land area of 9,147,420 square kilometres, the United States of America demanding 16.8 million GWh of energy per year, photovoltaics generating 300 GWh per hectare, a 2% loss due to power conditioning and 6.5% loss due to transmission and distribution. Land area sourced from The World Bank – ‘Land Area (SQ. KM)’ – data.worldbank.org. Energy demand based on 2012 data and sourced from International Energy Agency – ‘United States: Balances for 2012’ – www.iea.org. Energy generated by photovoltaics based on photovoltaic cells having an efficiency of 20%, 2,000 kWh of sunlight striking each square metre per year and the photovoltaic cells covering 75% of each square metre exposed. Power conditioning losses based on data sourced from Fuji Electric – ‘Large-scale Photovoltaic Power Generation Systems’ – Page 7. Transmission and distribution losses based on 2007 data for the United States and sourced from U.S. Department of Energy – ‘Frequently Asked Questions – Electricity’ – tonto.eia.doe.gov.
  18. Based on the United Kingdom having a total land area of 248,532 square kilometres, the United Kingdom demanding 1.48 million GWh of energy per year, photovoltaics generating 150 GWh per hectare, a 2% loss due to power conditioning and 6.5% loss due to transmission and distribution. Land area sourced from The World Bank – ‘Land Area (SQ. KM)’ – data.worldbank.org. Energy demand based on 2012 data and sourced from International Energy Agency – ‘United Kingdom: Balances for 2012’ – www.iea.org. Energy generated by photovoltaics based on photovoltaic cells having an efficiency of 20%, 1,000 kWh of sunlight striking each square metre per year and the photovoltaic cells covering 75% of each square metre exposed. Power conditioning losses based on data sourced from Fuji Electric – ‘Large-scale Photovoltaic Power Generation Systems’ – Page 7. Transmission and distribution losses based on 2007 data for the United States and sourced from U.S. Department of Energy – ‘Frequently Asked Questions – Electricity’ – tonto.eia.doe.gov.
  19. Based on over 2,800 kWh of sunlight striking each square metre of the earth’s surface on an annual basis close to the equator and 800 kWh striking the earth’s surface in Northern Europe.
  20. Lazard – ‘Levelized Cost of Energy Analysis – Version 8.0’ – Page 16.
  21. National Renewable Energy Laboratory – ‘PV FAQs’ – Page 1.
  22. Based on photovoltaic cells having an efficiency of 20%, 2,000 kWh of sunlight striking each square metre per year and the photovoltaic cells covering 75% of each square metre exposed.
  23. Calculation undertaken within the ‘Renewable Solution’ section of the ‘ZERO-FIFTY World Energy Database’ and based on a lifespan of 20 years. Lifespan sourced from Lazard – ‘Levelized Cost of Energy Analysis – Version 8.0’ – Page 16.
  24. No carbon offset data available so substituted with energy offset period. Based on a rooftop multicrystalline system. Sourced from National Renewable Energy Laboratory – ‘PV FAQs’ – Page 1.
  25. Hoogwijk, Monique and Graus, Wina – ‘Global Potential of Renewable Energy Sources: A Literature Assessment’ – Page 39. Please note, power conditioning, distribution and transmission losses have not been considered.

For further information about any of the above sources, please visit the ZERO EMISSION WORLD Works Cited page.

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