Chapter 16

Question 1

Strategic issues of renewable energy

Answer 1

• In 2011, renewable energy provided 9.4% of U.S. primary energy
o And 12.6% of electricity
o President Obama wants 80% of electricity from renewables by 2035
• Worldwide, renewables provide 16% of energy
o 20% of electricity
o UN wants 80% reduction in fossil fuels by 2050

Question 2

Why is using solar energy difficult?

Answer 2

• Solar energy is abundant but diffuse (scattered)
• Varies with season, latitude, atmospheric conditions
• We must turn this diffuse, intermittent source into a form (fuel, electricity) that can be used
• Collection, conversion, and storage of solar energy are difficult and must be cost effective

Question 3

Solar heating of water

Answer 3

• Active systems: pumps move the heated water

- Passive systems: use gravity and convection to move water from the collector to the tank

Question 4

Solar space heating

Answer 4

• Flat-plate collectors can be used for space heating
o They are less expensive and can be homemade
o Only air circulates through collector box

Question 5

building = collector

Answer 5

• A building can act as its own collector
• Awnings or shades shield windows from summer heat
• Deciduous plants block summer but not winter heat

Question 6

Energy stars

Answer 6

• A well-designed solar-energy building can reduce bills, w/ only 5-10% added construction costs
• 25% of energy use is for space and water heating
• The EPA’s Energy Star Program awards Energy Star labels to buildings

Question 7

PV system inverter

Answer 7

The inverter connects PV panels to electric grid or devices powered by PV electricity

Question 8

Burning firewood

Answer 8

• w/ enough forests, burning firewood (fuelwood) can be sustainable energy resource
• 5 million U.S. homes use only wood stoves for heat
• Pellet stoves use compressed pellets made from wood wastes

Question 9

Producing methane

Answer 9

• Biogas: anaerobic digestion of sewage sludge to produce methane and nutrient-rich fertilizer
o Animal manure can be digested
• Millions of Chinese farmers have digesters

Question 10

Miscanthus

Answer 10

giant perennial grass that can grow in poor soil

Question 11

Is hydrogen the highway to the future?

Answer 11

• Cars can be adapted to run on hydrogen gas
• Hydrogen is not fuel but energy carrier – like electricity
o Must be generated using another energy source
•The only major by-product of burning H2 is water
o 2H2 + O2  2H2O _ energy
• But there is almost no hydrogen gas on Earth

Question 12

Geothermal energy

Answer 12

• using naturally heated water or steam to heat buildings or produce electricity
• In 2011, geothermal energy provided electricity equal to 11 large nuclear or coal-fired power plants

Question 13

geothermal heat pump (GHP) system

Answer 13

geothermal heat pump (GHP) system: uses loops of buried pipes filled w/ antifreeze solution