BIO320 Chapter 10

1. 10-1
ENVIRONMENTAL
SCIENCE
A Study of Interrelationships
15th Edition
Renewable Energy Sources
Chapter 10
©2019 McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction
or further distribution permitted without the prior written consent of McGraw-Hill Education.

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Outline
10.1 The Status of
Renewable Energy
10.2 Major Kinds of
Renewable Energy
10.3 Energy Conversion

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10.1 The Status of Renewable
Energy (1 of 2)
Currently, alternative energy sources supply about 14%
of the world’s total energy.
• Renewable sources will become much more important as
fossil fuel supplies become more expensive.
• Biomass conversion
• Hydroelectric power
• Solar energy
• Wind energy
• Geothermal energy
• Tidal power

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10.1 The Status of Renewable
Energy (2 of 2)
Currently, alternative energy sources supply about 14% of the world’s total
energy.
• Some studies suggest these sources could provide half of the world’s
energy needs by 2050.
Source: Data from International
Energy Agency.

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Biomass Conversion
All biomass is produced by green plants that convert
sunlight into plant material through photosynthesis.
Biomass fulfilled almost all of humankind’s energy needs
prior to the Industrial Revolution.
Biomass is still the predominant form of energy used by
people in less-developed countries.

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Major Types of Biomass
There are several sources of biomass energy:
• Fuelwood
• Municipal and industrial wastes
• Agricultural crop residues and animal wastes
• Energy planta tions

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Fuelwood
In less-developed countries, fuelwood has been a major
energy source for centuries.
Fuelwood is the primary energy source for nearly half the
world’s population.
Due to intense population growth, an estimated 1.3 billion
people cannot get enough fuelwood, or are using it faster
than rate of regeneration.
It is a source of air pollution and particulate matter.

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Wood Use for Cooking
Many people in the developing world
use wood as a primary fuel for cooking.
Reliance on wood is a major cause of
deforestation.

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Waste
Waste is a major source of biomass and other burnable
materials produced by society.
The burning of solid waste only makes economic sense
when the cost of waste disposal is taken into account.
Using municipal waste as a source of energy:
• Reduces landfill volume.
• Requires large volume and dependable supply, and must be sorted.
• Produces air pollution, including pollutants not found in other forms
of biomass.

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Crop Residues and Animal Wastes
Materials left over following the harvest of a crop (e.g.,
straw and stalks) can be used as biomass fuel.
Animal dung is dried and burned or processed in anaerobic
digesters to provide a burnable gas.

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Energy plantations
Many crops, including sugar beets, sugar cane, corn,
grains, kelp, and palm oil can be grown for the express
purpose of energy production.
Two factors determine whether a crop is suitable for energy
use:
• Good energy crops have a very high yield of dry material per unit of
land.
• The amount of energy that can be produced from a biomass crop
must be more than the amount of energy required to grow a crop.

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Biomass Conversion Technologies
There are several technologies capable of converting
biomass into energy:
• Direct combustion
• Burning biomass in fires to cook food or heat homes.
• Biofuels production
• Fermentation converts plant sugars to ethanol, which is used as an energy source.
• Anaerobic digestion
• Green, wet biomass and animal waste is broken down by anaerobic bacteria,
producing methane and CO2.
• Pyrolysis
• A thermo chemical process that converts biomass to a more useful fuel such as
charcoal.

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Methane Digester

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Environmental Issues (1 of 5)
Habitat and biodiversity loss
• 1.3 billion people cannot
obtain wood, or harvest it
faster than it grows.
• Much forest has been
destroyed in Asia and Africa.
• Desertification has
increased in these regions.
Air pollution
• Burning wood produces air
pollution.
• Smoke, particulates, carbon
monoxide, and hydrocarbons
contribute to ill health.

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Hydroelectric Power (1 of 2)
Hydroelectric power is created when flowing water is
captured and turned into electricity.
• Damming a river and storing water in a reservoir is the most common
method.
• Pumped storage plants use two reservoirs separated by a significant
elevation difference.
• The potential for developing hydroelectric power is best in
mountainous regions and large river valleys.
• The World Energy Council estimates that it would be technically
possible to triple the electricity produced by
hydropower with current technology.

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Hydroelectric Power (2 of 2)
Hydroelectric power currently supplies 16% of world’s
electricity.
• In South and Central America, 65% of electricity used comes from
hydroelectric power.
• Norway gets 95% of its electricity and 60% of all its energy from
hydroelectric power.
• Construction of “mini hydro” (less than 10 megawatts) and “micro
hydro” (less than 1 megawatt) plants is increasing; these plants can
be built in remote places and supply electricity to small areas.

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Hydroelectric Power Plant
Source: Tennessee Valley
Authority.

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Environmental Issues (2 of 5)
Reservoir construction causes significant environmental
and social damage.
• Loss of farmland or forest land due to flooding
• Community relocation
• Prevention of fish migrations
• Trapping of silt fills in reservoir and stops flow of nutrients
downstream
• Mercury accumulation

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Solar Energy (1 of 2)
Daily energy from the sun is 600 times greater than energy
produced each day by all other energy sources combined.
• The major problems with solar energy are its intermittent and
diffuse nature.
Solar energy is utilized in three ways:
1. In passive heating, the sun’s energy is converted directly to heat
and used at collection site.
2. In an active heating system, the sun’s energy is converted into
heat, but transported elsewhere to be used.
3. Solar energy is also transformed into electrical energy.

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Solar Energy (2 of 2)
In a passive solar system, light energy is transformed to
heat energy when it is absorbed by a surface.
Buildings designed for passive solar heating in the
Northern Hemisphere usually have large, south-facing
windows.
Floors and walls, made of materials that absorb and store
the sun’s heat during the day, slowly release heat at night
when it is needed most. This feature is called direct gain.

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Passive Solar Designs
Source: Courtesy of National Renewable Energy
Laboratory/Lyle Rawlings from FIRST, Inc. (Fully
Integrated Residential Solor Technology)
Source: Courtesy of National Renewable Energy
Laboratory/Lyle Rawlings from FIRST Inc. (Fully
Integrated Residential Solor Technology)
Source: Courtesy of National Renewable Energy
Laboratory/NREL/PIX

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An Active Solar Heating Design

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Solar-Generated Electricity
Solar energy can generate electricity in two different ways:
1. Steam can be created to drive a turbine.
• Currently the most successful design is the parabolic trough which
heats oil in pipes. The heat is transferred to water to make steam and
run a turbine.
2. Photovoltaic (PV) cells can generate electricity directly.
• Generating electricity from coal and nuclear power is rising, while
electricity from photovoltaics is now less expensive in some places
than electricity from the grid.
• In recent years, the amount of PV power installed worldwide has been
increasing dramatically.

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Photovoltaics
Thin-film technology has made it possible to build solar cells
into roof shingles and tiles, building facades, and the
glazing for skylights and atria.
Worldwide, in 2016, about 69,000 megawatts of
photovoltaics were installed. In 2012, about 31,000
megawatts were installed.
U.S. solar energy capacity increased by 60 percent
between 2015 and 2016.

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Conventional Solar Generation of
Electricity
Solar Power Tower
Uses mirrors to focus sunlight
at a central point that raises
the temperature and allows
for the production of steam.
Parabolic Trough
Transfers heat to water and
converts it to steam.

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Environmental Issues (3 of 5)
Since solar energy is renewable, it has minimal
environmental impact.
However, the manufacture of the silicon or other materials
that make up the units requires large amounts of energy.
Thermal or photovoltaic power plants require large
amounts of land to position mirrors or solar collectors.
• SEGS system in California covers 6.4 km2 (2.5 mi2).
Installation of photovoltaics or water heating systems on
buildings does not require additional space and is often
incorporated into the design of the building.

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Photovoltaic Applications

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Wind Energy (1 of 2)
For centuries, wind has been used to move ships, grind
grains, pump water, and do other forms of work. In more
recent times, wind has been used to generate electricity.
In 2008, the U.S. Department of Energy published a report
that stated that it was technically feasible to generate 20
percent of electricity in the United States from wind by
2030.
Because winds are variable, wind must be coupled with
other, more reliable sources of energy.

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Wind Energy (2 of 2)
Since the technology to generate electricity from wind is
relatively easy to install, sizable increases in capacity occur
each year.
• In 2016, there were about 497,000 megawatts of installed capacity
worldwide.
• This was an increase of 14% over 15%
• The United States, Germany, and China constitute about 60 percent
of the installed capacity.
Total electrical energy produced by wind today is less than
1 percent of total worldwide energy consumption.

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Environmental Issues (4 of 5)
Moving blades are a hazard to birds and bats.
• Newer designs have slower-moving rotors that many birds such as
the golden eagle find easier to avoid.
Some people consider the sight of a large number of wind
generators to be visual pollution.

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Wind Energy Potential
Source: U.S. Department of Energy.

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Geothermal Energy (1 of 2)
In geologically active areas hot magma moves to the
surface and heats water.
• The hot water can heat buildings or generate electricity through a
steam turbine.
Wells are drilled to obtain steam trapped underground, and
the steam powers electrical generators.
The U.S. produces 30% of world’s geothermal electricity,
with the world’s largest plant in San Francisco.
• This accounts for less than 1% of U.S. electrical consumption.

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Geothermal Energy (2 of 2)
Heat pumps can be used in areas that are not geologically
active.
The pump extracts heat from the Earth, and deposits it in a
building.

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Environmental Issues (5 of 5)
Steam often contains hydrogen sulfide gas.
• It smells like rotten eggs.
• Minerals in the steam corrode pipes and
equipment.
• The minerals are toxic to fish.

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Tidal Power
The gravitational forces of the
moon and sun cause ocean
water to bulge out. Tides form
as the Earth rotates through
this bulge.
As water flows from a higher
level to a lower level, it can be
used to spin an electricity-
generating turbine.
Since tidal changes of roughly
16 feet are needed to produce
practical amounts of power,
suitable sites are limited.

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10.3 Energy Conservation (1 of 4)
Conservation is not a way of generating electricity, but a way of
reducing need for additional energy production and saving money for
the consumer.
Many cultural or lifestyle factors have been shaped by the availability of
relatively low-cost energy.
• Large homes
• Outdoor lighting
• Large lawns
If the cost of energy were higher, people would be likely to make
different choices about what is essential and would evaluate energy
efficiency more carefully.

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10.3 Energy Conservation (2 of 4)
There is typically a relationship between the cost of an item
and its energy efficiency.
• Often, poorly designed, energy-inefficient buildings and machines
can be produced inexpensively.
• The short-term cost (purchase price) is low, but the long-term cost for
upkeep and energy utilization is high.
• Typically, the cost of more efficient buildings or machines is higher,
but the difference in initial price is made up by savings in energy
cost over several years.
• This is known as the payback period.

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10.3 Energy Conservation (3 of 4)
The United States and Canada have about twice the per capita energy
consumption than other countries with similar economic status.
Many conservation techniques are relatively simple and highly cost-
effective:
• Highly efficient compact fluorescent light bulbs give the same amount of
light as incandescent bulbs for 25% of the energy, last about 6 times
longer, and and produce less heat.
• LED bulbs are even better. They use about 20 percent of the energy and
last 25 times longer than incandescent bulbs.

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10.3 Energy Conservation (4 of 4)

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Government Incentives
The shift to more efficient use of energy needs encouragement.
Most U.S. government incentives provide economic rewards in the form
of tax incentives or impose economic penalties (taxes and fines):
• Higher fuel economy standards for automobiles and trucks
• Tax incentives for those who upgrade insulation, windows, doors, heating
and cooling systems, and other appliances
• 2014 incandescent light bulb phase-out
• Higher energy efficiency standards for appliances
• Investment in more efficient electricity distribution
• Improvement in high speed rail transportation

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Fuelwood is the major source of energy in less-developed
countries.
Biomass can be burned to provide heat or electricity, or
can be converted to alcohol or used to generate methane.
Hydroelectric power can be increased significantly but may
displace people.
Solar energy can be collected and used in either passive
or active systems and can also generate electricity.
Summary (1 of 2)

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Geothermal and tidal applications are limited by
geographic locations.
Wind power may be used to generate electricity but
requires wide, open areas and a large number of wind
generators.
Energy conservation can reduce energy demands without
noticeably changing standards of living.
Summary (2 of 2)