Copyright © 2009 Benjamin Cummings is an imprint of Pearson 018 Renewable Energy Alternatives Ch 16 Environment & Ecology.

Copyright © 2009 Benjamin Cummings is an imprint of Pearson

018 Renewable Energy AlternativesCh 16

Environment & Ecology


Central Case: Iceland moves toward a hydrogen economy

Iceland aims to convert to an economy based completely on renewable energy.

- Geothermal

- Hydroelectric

- Hydrogen fuel

- Oil (import only)

81% renewable

geothermalhydropower


Economies are powered by fossil fuels 80% of our

energy comes from oil, coal, and natural gas


In the U.S., most renewable energy comes from hydropower and biomass.

Nations vary in the renewables they use


The new renewables are growing fast


• However, renewables receive little government help.

Rapid growth in renewables will continue


Biomass energy

• Biomass: organic material that makes up living organisms

• Biopower: biomass sources are burned, generating heat and electricity

• Biofuels: biomass sources are converted into fuels to power automobiles

algae corn sugar cane


Biomass energy comes from many sources

• More than 1 billion people use wood from trees as their principal energy source.


Biofuels can power automobiles

• Ethanol: produced as a biofuel by fermenting carbohydrate-rich crops

- Ethanol is widely added to U.S. gasoline to reduce emissions.

- Any vehicle will run well on a 10% ethanol mix.

In 2007, the U.S. produced 30 billion L (6.5 million gal) of ethanol in 100 ethanol plants.


• Flexible fuel vehicles: run on 85% ethanol

- But very few gas stations offer this fuel

• Biodiesel: a fuel produced from vegetable oil, used cooking grease or animal fat

• Some people use straight vegetable oil in their diesel engines.

Cars can run on ethanol

Bio-Beatle Rental on Maui


Drawbacks of biomass energy• Health hazards from indoor air pollution

• Rapid harvesting can lead to deforestation, soil erosion, and desertification.

• Growing crops exerts tremendous impacts on ecosystems.

- Decreased biodiversity

- Fertilizers and pesticides

- Land is converted to agriculture.

• Biofuel is competing with food production.

- Corn supplies for food have dropped.

• Substantial inputs of energy are required.


Hydroelectric power

• Hydroelectric (hydro) power: uses the kinetic energy of moving water to turn turbines and generate electricity

• The run-of-river approach generates energy without greatly disrupting the flow of river water.


A typical dam


Run of river Approach


Hydropower is clean and renewable

• Hydropower’s advantages over fossil fuels for producing electricity:

- It is renewable .

- It is clean

• Hydropower is efficient.

- It has an EROI of 10:1


Hydropower has negative impacts• Damming rivers destroys riverine habitats.

• Natural flooding cycles are disrupted.

• Sediment deposition

• Thermal pollution of downstream water

• Reducing fish populations and aquatic biodiversity

Fish ladder


Hydroelectric power is widely used• Nations with large rivers and economic resources have used

dams.

• But hydropower is not likely to expand.

- Most of the world’s large rivers have already been dammed.

- People have grown aware of the ecological impact of dams.

Three-Gorge Dam in China


Solar energy

• Passive solar energy: the most common way to harness solar energy

• Buildings are designed to maximize direct absorption of sunlight in winter and keep cool in summer.

• Active solar energy collection: uses technology to focus, move, or store solar energy


Passive solar heating is simple and effective

• Low south-facing windows maximize heat in the winter.

- Overhangs shade windows in the summer.


Passive solar heating is simple and effective

• Thermal mass: construction materials that absorb, store, and release heat

• By heating buildings in winter and cooling them in summer, passive solar methods conserve energy and reduce costs.


Active solar energy collection • Flat plate solar collectors (solar panels):

one active method for harnessing solar energy


Focusing solar rays magnifies energy

• Solar cookers: simple, portable ovens that use reflectors to focus sunlight onto food

• Power tower: mirrors concentrate sunlight onto receivers to create electricity

In southern California, a power tower produces power for 10,000 households.


Photovoltaic cells generate electricity

• Photovoltaic (PV) cells: collect sunlight and convert it into electrical energy

- These are used with wind turbines and diesel engines.

Bluenergy solar wind turbine


Photovoltaic cells generate electricity

• Photovoltaic (photoelectric) effect: occurs when light strikes one of a pair of metal plates in a PV cell, causing the release of electrons, creating an electric current


Solar power is little used but fast growing

• Solar energy was pushed to the sidelines by fossil fuels.

- lack of investment

- But grown 25%/year since 1971.

• Solar energy is attractive in developing nations.

- Where hundreds of millions don’t have electricity


Solar power offers many benefits

• It’s long lasting.• It’s quiet, safe, contain no

moving parts, and require little maintenance.

• Net metering: PV owners can sell excess electricity to their local power utility

• New jobs are being created.

• Some federal tax credits.


Location is a drawback


Solar Power Hawaii


Modern wind turbines convert kinetic energy• Wind turbines: devices that turn wind energy into

electricity

• Towers are 40–100 m (131–328 ft) tall.

- Higher is better to minimize turbulence and maximize wind speed.


Wind is the fastest-growing energy sector


Offshore sites can be promising

• Wind speeds are 20% greater over water than over land.

• There is less air turbulence over water than land.

• Costs to erect and maintain turbines in water are higher.

- But the stronger, less turbulent winds produce more power and make offshore wind more profitable.

• Currently, turbines are limited to shallow water.


Wind Power Hawaii



Wind power has many benefits

• Wind produces no emissions.

• It doesn’t release any CO2,, SO2, NOx, mercury.

• It is more efficient.• Turbines also use less water than conventional

power plants.• It can be used on many scales, from one turbine to

hundreds.• Farmers and ranchers can lease their land.

- Produces extra revenue - Landowners can still use their land for other uses.


Wind power has some downsides


U.S. wind-generating capacity

Mountainous regions have the most wind capacity.


The origins of geothermal energy


Geothermal energy is greatest in the U.S. west


Hawaii Geothermal Resources


Puna Geothermal Venture


Geothermal power has benefits and limits

• Benefits:

- Reduces emissions

- It does emit very small amounts of gases.

• Limitations:

- May not be sustainable

- Water is laced with salts and minerals that corrode equipment and pollute the air.

- Limited to areas where the energy can be trapped


Hydrogen Fuel

• Electricity splits hydrogen atoms from oxygen atoms in water molecules:

2H2O 2H2 + O2 - Produces pure hydrogen


A hydrogen-fueled bus

Hartford, CT


Other ways of obtaining hydrogen

• Hydrogen can also be obtained from biomass and fossil fuels:

CH4 + 2H2O 4H2 + CO2

• Results in emissions of carbon-based pollution

• Whether a hydrogen-based energy system is environmentally cleaner than a fossil fuel system depends on how the hydrogen is extracted.


Costs and benefits of hydrogen and fuel cells• Drawbacks:

- a lack of infrastructure and facilities, enormous expense, and hydrogen leakage could deplete stratospheric ozone

• Benefits:

- An unlimited supply that is clean and nontoxic to use

- Few greenhouse gases and other pollutants are made

- Is no more dangerous than gasoline in tanks

- Cells are energy efficient, silent, non-polluting, and won’t need to be recharged


We can harness energy from the oceans

• Tidal energy

• Wave energy

• OTEC


Tidal Energy

La Rance tidal power plant at St. Malo, France.


Tidal Energy

Tidal energy farm


Wave energy



Wave Energy Converter


40 kw experimental buoy


Ocean Thermal Energy Conversion (OTEC)


Renewable Energy Consumption in the Nation's Energy Supply, 2008


Hawaii’s Energy Consumption

88%


Hawaii Clean Energy Initiative

by 2030


QUESTION: Review

In the United States, where does most renewable energy come from?

a) Hydropower and geothermal energy

b) Wind power and solar power

c) Geothermal energy and biomass

d) Biomass and hydropower

e) Nuclear and coal


QUESTION: Review

Ethanol in the U.S. is made mainly from ______, and is used to ______.

a) Soybeans, heat homesb) Sugar cane, drive carsc) Corn, drive carsd) Willow trees, make electricitye) Wood, heat homes


QUESTION: Review

Which of the following is NOT a benefit of hydropower?

a) It produces carbon dioxide.

b) It is a clean source of energy.

c) It is renewable.

d) It will last as long as rivers do.

e) All of these are benefits of hydropower.


QUESTION: ReviewWhich of these is NOT a passive solar

technique?

a) The use of thermal mass

b) Using flat-plate solar collectors

c) Installing low, south-facing windows that will maximize sunlight capture in the winter

d) Using strategically planted vegetation

e) All of these are passive solar techniques.


QUESTION: Review

We can harness power from wind by using devices called:

a) Wind turbines

b) Wind parks

c) Wind farms

d) Solar cells

e) Nacelles


QUESTION: Review

Wind turbines can be erected singly, but they are most often erected in groups called:

a) Wind turbines

b) Wind farms

c) Wind mills

d) Solar cells

e) Farms


QUESTION: Review

Which energy source may not be renewable, and is laced with minerals that corrode equipment?

a) Solar panels

b) Wind energy

c) Geothermal energy

d) Hydrogen fuel cells

e) Wave energy


QUESTION: Review

Kinetic energy from waves and tides can be converted into:

a) Electricity

b) Wind energy

c) Heat for homes

d) Hydrogen fuel cells

e) Hot water for homes


QUESTION: Review

Production of hydrogen fuel can come from all of these sources EXCEPT:

a) Biomass

b) Water

c) Coal

d) Oil

e) It can come from all of these sources.


QUESTION: Interpreting Graphs and Data

_____ is the best state for producing solar energy, while _____ is best for wind energy.

a) Maine, Floridab) Texas, Kentuckyc) Arizona, Idahod) North Dakota, Ohioe) Louisiana, Oklahoma

Solar

Wind


QUESTION: Interpreting Graphs and Data

If ethanol in the U.S. is produced from corn, a drawback suggested from this graph could be:

a) More corn would become available

b) More competition between food and fuel

c) Less land planted in corn

d) Corn would cost lessd) None of these

Copyright © 2009 Benjamin Cummings is an imprint of Pearson 018 Renewable Energy Alternatives Ch 16 Environment & Ecology.

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