Photo Voltaics (PV)
Two ways to gather energy
from the sun
-Thermal Solar
-Photovoltaics
“Photovoltaics”—derives
from the Greek “Phos”
meaning light, and
“Voltaic” meaning
electricity.
*Solar energy has been used as far back as 7th
century B.C.
*It first entered the U.S. in 1954 with only a 4%
efficiency in silicon photovoltaic cells.
*In 2001 three countries were very dedicated to
this form of energy.
*These three countries supplied 85% of PV
energy, the U.S. is only responsible for 15%.
The basic principle behind the
technology is light energy in the
form of photon particles are
captured by energy absorbing
materials like silicone.
Once captured, negatively
charged electrons split away
from the atom and flow in one
direction, the corresponding
positively charged energy is
directed in the opposite
direction.
they are:
• Monocrystalline panels
• Polycrystalline panels
• Thin film panels
• Hybrid panels (which are
monocrystalline with an embedded layer of
thin film)
Monocrystalline panels
get their name from the
fact that the silicon
wafer used to make is
cut from a single crystal
of silicon.
- highest efficiency of
any cells on the market
under
High degree of purity
Sliced very thinly to
make wafers.
- maximize power
output when roof space
is limited.
*
- high efficiency means
smallest footprint for
their output, so you can
These cells are cut from
an ingot of melted and
re-crystallised silicon
end to be slightly less
efficient for the same
size cell.
cost less
*
Polycrystalline cells are
slightly less efficient
than monocrystalline
cells
more roof space to
produce the same
output capacity.
Thin film silicon cells are
made up of silicon atoms
in a thin layer
Thin film offers the best
shade tolerance of any
solar technology.
absorb light more readily
than crystalline so cells
can be thinner.
When compared with
other types of panels,
thin film performs best
under hotter.
For this reason, amorphous
silicon is also known as
‘thin film’ photovoltaic
(PV) technology.
*
1977-Jimmy Carter
installs Photovoltaics
on the White House
President Reagan had
them removed
1985-20% Efficiency
To day-42% Efficiency
Helping the
Environment
Local & Federal Tax
Incentives
Potential To Earn
Money
Utility Rebates Based
on Installed KW
* The Regions Climate
* Desired amount of Supplemental Energy
* Funding For Initial Cost of System
* Eligibility For Incentives
* Site Restrictions
* Community Restrictions
* Local Utility Buyback Rates
* A 5KW system can potentially supply a conventional home
with power in a climate with average solar gains
* A 2KW system can potentially supply a energy efficient
home with power in a climate with average solar gains
* Partial supplementary energy is also a good choice.
In 2008, the installed cost of a residential PV
system in the United States ranged $8 to $10 per
installed watt before government or utility
incentives.
*A 2 KW system fully installed could cost on
average between $16,000 to $20,000.
*A 5 KW system fully installed could cost on
average between $30,000 to $40,000.
*Utility rebates on average are between $300 to
$400 per KW installed.
*The Renewable Energy and Job Creation Act will
give a 30% tax reduction on cost of system.
* An average home with a 5-kW system in southern Arizona
* Energy from the PV system = (5-kW) x (2100kWh/kW-year) =
10,500 kWh/year
* Energy Bill Savings per year = (10,500 kWh) x ($0.10/kWh-buy
back) = $1,050/year
* Payback of system with no incentives = $30,000 initial
cost/$1,050 = 28.6 years
Does the Pacific Northwest Have
Good Solar Potential?
The Answers is…….
Yes
Even west of the Cascades
*Oregon’s Willamette Valley receives
as much solar energy annually as the
U.S. average –
as much over the course of the year
as southern France and more than
Germany
Solar potential, not every building site will be
suitable for a solar installation. The first
Some questions you should ask are:
* Is the installation site free from shading by nearby
trees, buildings or other obstructions?
* Can the PV system be oriented for good
performance?
* Does the roof or property have enough area to
accommodate the solar array?
* If the array will be roof-mounted, what kind of roof
is it and what is its condition?
*Solar modules are usually mounted on
roofs. If roof area is not available, PV
modules can be pole-mounted, groundmounted, wall-mounted or installed as part
of a shade structure
*Photovoltaic arrays are adversely affected by
shading.
*A well-designed PV system needs clear and
unobstructed access to the sun’s rays from about
9 a.m. to 3 p.m., throughout the year.
*Even small shadows, such as the shadow of a
single branch of a leafless tree can significantly
reduce the power output of a solar module.
*Shading from the building itself – due to vents,
attic fans, skylights, gables or overhangs – must
also be avoided.
*In northern latitudes, by conventional
wisdom PV modules are ideally
oriented towards true south.
*Deviations between magnetic and true
south, referred to as magnetic
declination, vary by location.
*Orientation of a roof does not need
to be perfect.
*Solar modules produce 95 percent of
their full power when within 20
degrees of the sun’s direction.
*Roofs that face east or west may also
be acceptable.
*Optimum orientation can be influenced by
typical local weather patterns.
*Western Washington and Oregon frequently
have a marine layer of fog that burns off
by late morning and so have better solar
resource after noon than before noon.
*West of the Cascades, the maximum power
is generated with a southwest orientation.
Broadly classified by answers to the
following questions:
Will it be connected to the utility’s
transmission grid?
Will it produce alternating current (AC) or
direct current (DC) electricity, or both?
Will it have battery back-up?
Will it have back-up by a diesel, gasoline or
propane generator set?
* Most new PV systems being installed in the United States
are grid-connected residential systems without battery
back-up.
* Many grid-connected AC systems are also being installed in
commercial or public facilities.
* Two types:
• Grid-connected AC system with no battery or
generator back-up.
• Grid-connected AC system with battery back-up.
Solar Modules
*The heart of a photovoltaic system is the solar
module. Many photovoltaic cells are wired
together by the manufacturer to produce a solar
module.
*When installed at a site, solar modules are
wired together in series to form strings. Strings
of modules are connected in parallel to form an
array.
Rated Power
*Grid-connected residential PV systems use modules
with rated power output ranging from 100-300
watts.
*Rated power is the maximum power the panel can
produce with 1,000 watts of sunlight per square
meter at a module temperature of 25oC or 77oF in
still air.
*Actual power output will almost always be less.
PV System Voltage
* Modern systems without batteries are typically
wired to provide from 235V to 600V.
* In battery-based systems, the trend is also
toward use of higher array voltages, although
many charge controllers still require lower
voltages of 12V, 24V or 48V to match the
voltage of the battery string.
M stands for Max
GOooooooo Max
*Solar heaters, or solar thermal systems, provide
environmentally friendly heat for household water,
space heating, and swimming pools.
*The systems collect the sun’s energy to heat air or a
fluid. The air or fluid then transfers solar heat
directly or indirectly to your home, water, or pool.
Size of system
* 20 square feet (2 square meters) of collector area
for each of the first two family members. For every additional
person, add 8 square feet (0.7 square meters) if you live in the
Sun Belt area of the United States, or 12 to 14 square feet (1.1
to 1.3 square meters) if you live in the northern United States.
Size of Tank
For active systems, the size of the solar storage tank increases with the size of the
collector—typically 1.5 gallons per square foot of collector.
A small, 66-gallon system is usually big enough for one to three people; a
medium-size, 80-gallon system works well for a three- or four-person
household; and a large, 120-gallon system is appropriate for four to six
people.
Integral collector-storage passive systems
These work best in areas where temperatures
rarely fall below freezing. They also work well in
households with significant daytime and evening
hot-water needs.
Thermosyphon systems
Water flows through the system when warm water
rises as cooler water sinks. The collector must be
installed below the storage tank so that warm
water will rise into the tank.
Integral collector-storage systems
Also known as ICS or batch systems,
one or more black tanks or tubes in an insulated, glazed
box. Cold water first passes through the solar collector,
which preheats the water.
Should be installed only in mild-freeze climates because
the outdoor pipes could freeze in severe, cold weather.
Evacuated-tube solar collectors
They feature parallel rows of transparent glass
tubes. Each tube contains a glass outer tube and
metal absorber tube attached to a fin. The fin's
coating absorbs solar energy but inhibits radiative
heat loss. These collectors are used more
frequently for U.S. commercial applications
Flat-plate collector
Glazed flat-plate collectors are insulated, weatherproofed
boxes that contain a dark absorber plate under one or more
glass or plastic (polymer) covers.
Requirements
*Need a substantial structural base
*A structure must be a minimum distance from the
base of tower of 1.5 times the height of the tower.
* Does not work well when the wind doesn't blow
* They make noise.
* Can harm birds. (But so do cats)
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