Renewable and Alternative Energy
Resources
Chapter 17
SOLAR ENERGY
Solar Energy
• Most energy efficient of all energy resources
• High net energy yield
• Estimated to supply 10% of US electric energy
over next 20 years
Passive Solar Systems
• Good passive solar design is based upon the
position of the sun.
• No mechanical means are used
• Use natural systems –
– sun
– landscaping to heat or cool a building
– shades on windows
– Natural ventilation
Passive Solar
Heating
• Passive solar heating
system absorbs and
stores heat from the
sun directly within a
structure without
the need for pumps
to distribute the
heat.
Passive Solar Collectors
• Passive solar collectors include
– South facing windows (in the US)
– Adobe walls used for heat storage
– Flagstone floors used to heat
– Summer cooling vents in the roof
– Drying your clothes on a line in the backyard
Active Solar Systems
• About 20% efficient
• Use pumps, solar cells, photovoltaic (PV) systems
and other technologies to generate electricity.
– PV systems – used in signal lights, calculators, wrist
watches, residences and electric utilities
• Some systems produce high-temperature water
for industrial applications; or steam to run
turbines.
– Usually requires use of mirrors, lenses, heliostats
Heat to house
(radiators or
forced air duct)
Superwindow
Heavy
insulation
Pump
Superwindow
Heat
exchanger
Stone floor and wall for
heat storage
PASSIVE
Hot
water
tank
ACTIVE
SOLAR WATER HEATER:
FREE energy from the Sun
STANDARD WATER HEATER:
COSTLY gas or electric
Annual operating cost: $50
Annual operating cost: $500+
Storage Capacity: 80-120 gal
Storage Capacity: 40-50 gal
Life expectancy: 15-30 years
Life expectancy: 8-12 years
Lifetime operating cost: $1,000
Lifetime operating cost: $10,000
Does NOT pollute environment
Depletes fossil fuels
Increases equity in your home
No added value to your home
25% return on your investment
No return on utility payments
Protection from future increases
At mercy of utilities/government
Hot water during blackouts!
No hot water during blackouts
Producing Electricity with Solar Cells
• Solar cells can be
used in rural villages
with ample sunlight
who are not
connected to an
electrical grid.
Figure 17-18
• Photovoltaic (PV) cells can provide electricity for
a house of building using solar-cell roof shingles.
Using Solar Energy to Generate HighTemperature Heat and Electricity
• Large arrays of solar
collectors in sunny
deserts can produce
high-temperature
heat to spin turbines
for electricity, but
costs are high.
Figure 17-15
Passive or Active Solar Heating
Advantages
• Energy is free
• Net energy is moderate
(active) to high (passive)
• Quick installation
• No carbon dioxide emissions
• Very low air and water
pollution
• Very low land disturbance
• Saves fossil fuel resources
• Could create new jobs
•
•
•
•
•
Disadvantages
Not always available –
weather dependent;
requires a backup power
source
Needs heat storage system
High cost
Active systems need
maintenance and repair
Appliances must be low
voltage (average household
Energy Storage
The best
example of an
energy storage
element in a
solar energy
system is a hot
water tank.
INDIRECT SOLAR ENERGY
Firewood, hydropower and windmills/turbines all
get their energy from the sun.
– The sun’s radiation heats different parts of the
earth at different rates.
– Different areas absorb or reflect at different rates.
– Hot air rises, cooler air moves along the Earth’s
surface.
– When air is in motion, it contains kinetic energy.
Net Energy Comparisons
• Net energy – amount of energy left over after
conversions.
• Highest net energy yield overall comes from fossil
fuels
– #1 Coal
#2 Natural gas
Passive solar gives highest net yield of renewable
energy sources and is the most energy efficient of all
energy sources.
WIND POWER
WIND POWER
• About 35% efficiency
• Favorable sites – American Midwest, coastal
regions and mountain passes.
• Wind turbines convert kinetic energy into
mechanical energy
• Turbine drives generator which converts
mechanical energy into electricity.
Wind Turbines
• Two types
1) Horizontal-axis turbine
2) Vertical-axis turbine
(egg-beater)
Made of steel and
fiberglass
Energy Production
• The largest wind turbines
can power over 600
houses.
• Global capacity is close to
70,000 MW (1 MW can
power over 250 homes).
• Turbines must be
mounted 100 ft (30 m) or
more aboveground to
capture optimum energy.
Technological Obstacles
• Wind turbines reach maximum generation at
wind speeds of about 30 mph.
– do not generate at winds speeds below 8 – 10 mph.
– cut out for safety reasons if winds are above 56 mph.
• Larger turbines (375 ft) require a base of some
1000 tons of reinforced concrete.
• Projected turbine lifespan is 20-25 years, but
many have to be replaced after just 9-12 years.
Advantages
• Free source of energy
• Renewable
• Pollution free – no emissions of air pollutants or
GHGs; no toxic wastes
• Relatively low impact on environment – no
drilling, mining or waste products. However, they
do take up a lot of space (several acres)
Disadvantages
• Expensive
• Dependability – wind is intermittent
• Wind energy cannot be stored unless batteries
are used
• Good wind sites are often located in remote
locations far from areas of electric power
demand.
• Can compete for land space (habitat destruction)
• Noisy
Lightning
• Damage to wind
turbines is estimated at
$50,000/yr
• Some costs run over
$250,000/yr
Visual Impact
Birds
What the…!!!
• 10,000 to 15,000 birds
die each year due to
collisions with turbines
• Altamont, CA – 17,000
raptor deaths
*&!*#