Sustainable Energy Notes
Wind & Solar
Introduction to Alternative Energy
Sources
●Nonrenewable alternative energy
●Nuclear
●Requires a mineral fuel mined from Earth
●Geothermal
●Heat is extracted faster than it is replenished
●Renewable energy sources
●Solar, fresh water, wind, ocean, and biofuels
●All derive from the sun’s energy
Wind Energy
●Wind turbines use the kinetic energy of
moving air to spin a turbine, which in turn
converts the mechanical energy of the
turbine into electricity.
●Wind energy is a renewable, clean source of
energy. However, birds and bats may be
killed if they fly into or near the spinning
turbine blades.
Making Wind
● Wind is produced when differential heating of Earth’s
surface create air masses with differing heat contents and
densities
Making Wind
●Wind is highly variable
in time, place, and
intensity
●Wind velocity often
increases over hill tops
or funneled through a
mountain pass
Wind Power
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Wind turbines = devices that harness power from wind
Towers are 40 - 100 m (131 - 328 ft) tall
● Higher is better to minimize turbulence and maximize wind speed
Windmills have been used for 800 years to pump water
Today, wind power produces electricity for the same price as conventional
sources
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Wind power could be expanded to meet the electrical needs of the entire U.S.
Wind speeds are 20% greater over water than over land and less turbulent.
Wind-The Good…
PROS
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Wind produces no emissions once installed
●
It prevents the release of CO2
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It is more efficient than conventional power sources
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Turbines also use less water than conventional power
plants
●
Farmers and ranchers can lease their land
● Produces extra revenue
● Landowners can still use their land for other uses
●
Advancing technology is also driving down the cost of
wind farm construction
Wind- …and The Bad
CONS
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The wind doesn’t always blow, limiting its reliability to
generate electricity.
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Research and construction is costly.
●
Turbine construction is often far from population centers
and requires new infrastructure.
●
Wind farms proposed near population centers are often
opposed by local residents.
●
Wind turbines also pose a threat to birds and bats, which
can be killed when they fly into rotating blades
Future of Wind Power
●Growing at approximately 30% per year
●Nearly 10 times the growth rate of oil use
●Created thousands of jobs and investment
opportunities
●Technology producing more efficient wind
turbines
Solar
Energy
Solar
Energy
●Photovoltaic solar cells capture light energy from the sun
and transform it directly into electrical energy. Their use is
limited by the availability of sunlight.
●Active solar energy systems use solar energy to heat a
liquid through mechanical and electric equipment to collect
and store the energy captured from the sun.
●Passive solar energy systems absorb heat directly from the
sun without the use of mechanical and electric equipment,
and energy cannot be collected or stored.
●Solar energy systems have low environmental impact and
produce clean energy, but they can be expensive. Large
solar energy farms may negatively impact desert
ecosystems.
Photovoltaic Solar Cells
● Capture light energy from the sun and transform it directly into
electrical energy. Their use is limited by the availability of sunlight.
Passive Solar energy
●
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Each square meter of Earth receives about 1
kilowatt of solar energy = 17 times more than a
lightbulb
●
There is great potential in 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. Ex-South Facing windows
with an eve. Take advantage of greenhouse
effect
●
Thermal mass = construction materials
that absorb, store, and release heat.
●
Planting vegetation in strategic locations
●
By heating buildings in winter and
cooling them in summer, passive solar
methods conserve energy and reduce
costs
Active Solar Energy
●
Active solar energy collection = uses technology to
focus, move, or store solar energy
●
Photovoltaic cells = collect sunlight and
convert it into electrical energy thanks to the
photoelectric effect. Sunlight excites
electrons in two silicon plates and moves
them.
●
Solar plates=dark colored plates absorb
heat and transfer it via air, water, or
antifreeze.
●
Solar cookers = simple, portable ovens that
use reflectors to focus sunlight onto food
Hanes 2.0 Solar Oven
CSP Solar Energy
●
Concentrating solar power
(CSP) plants use mirrors to
concentrate the sun's energy to
drive traditional steam turbines
or engines that create
electricity. The thermal energy
concentrated in a CSP plant
can be stored and used to
produce electricity when it is
needed, day or night.
●
Power tower = mirrors
concentrate sunlight onto
receivers to create electricity
●
Solar-trough collection
systems = mirrors focus
sunlight on oil in troughs. Oil
creates steam to produce
electricity
Solar Pros
PROS
●
The Sun will burn for 4 - 5 billion more years
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Solar technologies are quiet, safe, use no
fuels, contain no moving parts, and require
little maintenance
They allow local, decentralized control over
power
Developing nations can use solar cookers,
instead of gathering firewood
Net metering = PV owners can sell excess
electricity to their local power utility
New jobs are being created
Solar Cons
CONS
●
More expensive than fossil
fuels
●
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Solar battery storage is
expensive
Not all regions are sunny
enough to make current
technology pay for itself
Daily and seasonal variation
Production of panels is
energy and materials
intensive
What is the EROI?
● Energy return on investment
● Energy return
must be greater
than 1:1 or you
spend more
energy to get it
than you get from
it.
What EROI is needed?
● For society to function, we need an
EROI of somewhere between 5:1 to 7:1.
● 2:1 - $2 out
with $1 in.
● 5:1 - $5 out
with $1 in.
● Can renewables power our society?
Can renewables power society?
● For society to function, we need an
EROI of somewhere between 5:1 to 7:1.
What EROI is needed?
● For society to function, we need an
EROI of somewhere between 5:1 to 7:1.
● Can renewables power our society?
Solar Energy
●10 weeks of solar
energy equivalent
to all known fossil
fuel reserves
●Two types
●Passive
●Active
Passive Solar Energy
●Promotes cooling in hot weather and
retaining heat in cold weather
●Methods include:
●Overhangs that block summer sun but allow
winter sun
●Walls in buildings that absorbs heat during
the day and releases it at night
●Deciduous trees as landscaping
Active Solar
●Energy systems that require mechanical
power
●Electric pump circulate air, water or other
fluids from solar collectors to a location where
heat is stored
●Additional pumps move heat to location
where energy is converted and used
Solar Collectors
●Provide space heating
or hot water
●Flat Plate Collector
●Flat, glass-covered
plates over a black
background where
absorbing fluid is
circulated through
tubes
●Evacuated tube
collector
●Each tube filled with
absorbing fluid pass
through a larger tube
Photovoltaic
●Converts sunlight directly into electricity
●Made from thin layers of semiconductors and
a solid-state electronic components with few
or no moving parts
●World’s faster growing source of energy
Photovoltaic

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Off the grid
Emerging as a major contributor to
developing countries
●Don’t have ability
to build a electrical
grid
●Systems can
power lights and
televisions in small
villages
Solar Thermal Generators
●Focus sunlight onto
water-holding
containers
●Traditionally built using
solar power towers
●Water boils and is
used to run
conventional steamdriven electrical
generators
●Built with very large
output
Solar Thermal Generators
●In newer facility
●Mirrors focus solar energy onto pipes with
heat-absorbing fluid
Solar Energy and the Environment
●Generally low impact
●One concern
●Variety of metals, glass plastics, and fluids
used in the manufacture and use of solar
equipment
●Production and accidental spills could
release toxic materials