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?
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 2011?
- The United States
Germany is world leader, with a cumulative 17,192 megawatts installed by the end of 2010. Spain is second, with 3,784 megawatts. The United States has 2,528 megawatts, behind Italy and Japan. China had 893 megawatts.
After California, which U.S. state has the most solar power installed, as of 2011?
- New Jersey
Thanks to strong state policies encouraging renewable energy, solar installations have grown strongly in New Jersey, now with 293 megawatts of installed capacity, second only to California, with 917 megawatts.
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:
- Moving parts
- Connection to the electricity grid
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
- 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 in 2010?
- 17 percent
- 27 percent
- 47 percent
- 87 percent
The U.S. Energy Information Administration's estimate of the cost of new solar PV generation fell 47 percent in its 2011 annual energy outlook to $210 per megawatt-hour. That's twice the projected cost of new conventional coal generation but far more competitive than the previous year, when there was a fourfold spread.
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