Quiz: What You Don't Know About Solar Power


Photograph by Michael Melford, National Geographic

You've seen the panels on rooftops and mirrors in the desert. But how much do you really know about the technology needed to capture the tremendous power of the sun?

If all the energy of the sun shining on the Earth's land mass could be harnessed, it would be enough to meet the world's power needs how many times over?

  • 6 times
  • 60 times
  • 600 times
  • 6,000 times

The sunshine on the Earth's land is estimated to be 120,000 terawatts (trillion watts), or about 6,000 times the world's estimated 20-terawatt electricity demand by 2020.

When was the first discovery that certain metals produced an electric current when exposed to light?

  • 1752
  • 1839
  • 1911
  • 1954

French physicist Alexandre-Edmond Becquerel noticed the effect when working with metal electrodes in an electrolyte solution, but he couldn't explain why.

What were researchers originally trying to achieve when they developed the first practical photovoltaic (PV) cell in 1954?

  • A new power source for telephone systems
  • A power source for remote desert locations
  • A power source with no carbon dioxide emissions
  • A power source that allowed households to get off the electrical grid

Researchers at Bell Labs in Murray Hill, New Jersey, were interested in a power source for telephone systems that would not degrade in humid locations.

What country has the most solar PV power, as of 2013?

  • The United States
  • China
  • Germany
  • Spain

Germany is world leader in electricity produced from solar panels, followed by China, Italy, Japan, and the United States, according to a report from the U.S. Department of Energy.

After California, which U.S. state has the most solar power installed, as of 2014?

  • Arizona
  • Nevada
  • Florida
  • New Jersey

Arizona ranks second in cumulative installed solar capacity with 2,069 megawatts. (California has 9,977 megawatts, according to industry figures. New Jersey, North Carolina, and Nevada round out the top five.

In 2010, the United States manufactured what percentage of the world's solar PV panels?

  • 1 percent
  • 6 percent
  • 16 percent
  • 60 percent

The birthplace of solar PV technology produced only 6 percent of panels sold in 2010. China was undisputed leader with 51 percent of the market, followed by Germany with 10 percent, says GTM Research.

Photovoltaic solar energy is the only type of electricity generation that DOESN'T require:

  • Water
  • Moving parts
  • Connection to the electricity grid
  • Wiring

Solar PV panels are the only means today of generating electricity without moving parts. True, they require very little water (just enough to keep surfaces clean), and can be used for living off the electricity grid, but the same is true of wind energy.

What is essential for a rooftop PV system to work?

  • An inverter
  • A rheostat
  • A connection to the electric grid
  • A battery

An inverter is needed to convert the direct current produced by the solar panels to the alternating current required by most household appliances.

The solar arrays on the International Space Station are visible from Earth. They are the largest deployable space structures ever built. How much power can they produce?

  • 1 kilowatt
  • 10 kilowatts
  • 100 kilowatts
  • 1,000 kilowatts

After Space Shuttle astronauts in 2009 delivered the last addition to the solar array, total capacity was 80 to 100 kilowatts, enough to power 42 homes, said NASA contractor Boeing. The solar arrays are 240 feet (73 meters) long.

Concentrating solar power plants don't need photovoltaic cells. What do they need?

  • Large land area
  • Water
  • Reflectors
  • All of the above

Concentrating solar power plants use mirrors or lenses to focus solar energy from a wide area (usually under cloudless desert sky) to boil water to turn turbines.

Which is NOT one of the ways researchers are seeking to drive down the cost of solar photovoltaic cells?

  • By removing impurities in silicon
  • By using new materials
  • With photovoltaic material that can be "painted" on
  • By using geospatial software to design systems online

Impurities in the silicon actually cause the free electron movement that creates electric current. But scientists are working on newer and thinner materials, even solar ink or paint. And numerous companies aim to lower transaction costs by enabling customers to design and order online.

How much did the U.S. government's estimate for the cost of solar PV fall between 2009 and 2013?

  • 20 percent
  • 30 percent
  • 40 percent
  • 50 percent

The U.S. Energy Information Administration's estimate of the cost of new solar PV generation in 2013 fell 40 percent to $125 per megawatt hour in its 2015 Annual Energy Outlook. Its earlier estimate was $211 per megawatt hour.





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