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Your
current electricity rates are
70% dependent on fossil fuels. The future for anything dependent on
these fuels is not bright. In several years, the electricity rates
may double, triple. Many companies may go bankrupt because of this
crisis. You have an exit: alternative energy. But now is the
only time you can go for it. This is your
chance for escaping the disaster waiting
ahead. Now you can buy a solar system at a very reasonable rate.
Once the crisis hits hard, you will have saved a gold mine.
Our world is running out
of fuel, while our demands are increasing and carbon dioxide and other
pollutants are being continuously released to the atmosphere. You
already know the rest of the story, and you already thought of
helping. However, you were not sure about giving your money away
to organizations you do not know. But good news!
Helping
the environment can actually save you money! One way to
do this is to go solar. Here are the benefits of going solar:
- Each kWh produced from solar technology avoids over 1 pound of
carbon dioxide emission!
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- Solar allows you to be energy independent!
- You are not affected by the hikes in the utility rates!
- Solar panels could actually improve the aesthetics of your home
and make it look cool if designed right!
- Sun rays, instead of heating up your roof and giving discomfort,
will be absorbed for useful purposes.
- Almost half of your system is paid by the California government
with an instant rebate! |
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- In addition, you also get a federal tax credit for 30% of your net cost!
All these benefits come with a moderate capital investment, which
could be financed. There is literally no risk in installing
solar, and you will be backed up with all kinds of warranty terms for
several decades.
Sun is for everyone.. use it! |
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Q |
What
can solar electricity be used for? |
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Solar electricity is no
different than regular electricity you get from your grid. The
voltage is the same 110V. Solar electricity can power:
R efrigerators,
air conditioners, stoves, televisions, lamps, and hybrid cars!
A 3 kw system on your
roof could power your future electric vehicle for up to 30 miles per
day ! This number is based on facts provided by Wikipedia. |
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Q |
What
kind of maintenance is required for solar panels? |
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None! That is right, your
solar system can run without maintenance for long years. However,
washing once a year during July is a recommended process to improve
the efficiency of the panels. Of course, you can wash more if you
like, but definitely do not wax! |
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Q |
How
do solar panels work? |
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Solar panels convert
sunlight directly into electricity, with no moving parts, no liquids,
no noise or emissions. This technology is called photovoltaics,
meaning electricity (voltaics) through light (photo). Solar panels
are commonly made of silicon cells. For more info on How Solar Cells
Work, you may refer to the "Links"
page. |
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Q |
How
much voltage does a solar panel generate? |
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That depends on how many
solar cells have been connected in series in the panel. However,
almost all current solar cells each generate around 0.5V. A typical
panel would generate about 18V. |
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Q |
How
much voltage does a solar system generate? |
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Again depends on how many
solar panels have been connected in series in the system. The panels
in series in a system are called strings. There may be several
strings in parallel in a system, and each string will have equal
number of panels and generate equal voltage. The higher the voltage
the less the resistance losses in wires, thus lesser the strings the
better. |
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Q |
What
is an inverter? |
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Solar panels inherently
generate DC current. The electricity grid, on the other hand, carries
AC power, which is better for carrying the electricity long distances
with wires. Thus, a device called inverter is necessary to convert
the DC generated by the solar panels to the common AC current. It is
an indispensable component of the solar system. |
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Q |
What
is solar irradiance? |
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Irradiance is the direct,
diffuse, and reflected solar radiation that strikes a surface. Usually
expressed in kilowatts per square meter. Irradiance x time =
insolation. Also interpreted as peak sun hours to measure output of
solar panel production. Every hour in which the irradiance averages
1,000 watts per square meter is considered one peak sun hour. |
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Q |
What
are the AC and DC disconnects? |
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Disconnects are switches
that are required for the safety of electrical systems. |
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Q |
What is the optimum
location and position for solar panels? |
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Solar panels best work in
sunny regions where there are less clouds. However, solar panels are
most popular in Japan and Germany where the weather is mostly cloudy!
Even in those conditions, solar panels turn out to be a feasible
solution. The best is to install the panels as high as possible so
they are away from shade. The nearest obstacle should be kept at a
distance at least twice its height. The best tilt angle and
orientation is 30 degrees facing south. When we say south, we do
not mean the magnetic south but the true south, which in SF is 15 degrees east of
magnetic south. |
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Q |
Do
solar panels work in cloudy weather? |
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Solar panels absorb
photons of certain wavelengths, of which big portion is in visible
spectrum and hence the dark color of solar cells. Silicon crystal
based solar panels could use photons directly from the sun, or
reflected light from clouds etc., or even diffused light. In general,
higher the intensity of light, higher the efficiency of the panels, so
dim light usually does not generate much electricity. Monocrystal
panels are the only ones with good efficiency at low light
intensities, like in cloudy weathers, thus with monocrystal panels,
you can achieve more energy on average. |
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Q |
What
is the difference between MonoCrystal and PolyCrystal panels? |
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Silicon crystal based
solar panels are divided into the subgroups of Polycrystal and
Monocrystal. These panels are made by slicing a block of purified
silicon crystal using ultra high technology into thin wafers.
Monocrystal solar cells are made up of a single crystal and are
continuous. Polycrystal solar cells on the other hand are made of
several crystals bound together and sliced as such. The difference
between these is like that between hardwood and composite wood,
including the quality. When you look at the two side-by-side,
you will see that Monocrystal panels are darker, which means they
absorb more light and product more energy. Monocrystal panels are higher quality than
polycrystalline and harder to manufacture. |
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Q |
What
is the difference between STC & PTC? |
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STC stands for Standard
Test Conditions. The manufacturer of the panels tests them at STC,
which usually is at lower solar irradiance and lower cells
temperatures. However, in the field the panels experience high
temperatures, like 50 degree Celsius because of solar radiation. PTC
stands for PVUSA
Test Conditions
and simulates the
actual operating conditions more realistically.
It is based on 1000 Watt/m2 solar irradiance, 20 degree
Celsius ambient temperature, and 1 meter/second wind speed.
The efficiency of the
panels depends on temperature, and thus the PTC ratings are generally
less than STC, whereas the nominated power output of a panel is closer
to the STC rating. |
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Q |
What
kinds of rebates are there? |
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The state of California
offers two kind of rebate programs as of May '07: PBI and EPBB.
The PBI (Performance Based
Incentive) program is for systems larger than 100kw. In this program,
the rebate is paid per kWh energy you use for 5 years. The current
rebate rate is 39 cents per kWh. If you do not use it, however, you
loose it, so you need to keep your solar system on. There are plans
on converting all programs to PBI. The 30% tax
The EPBB (Expected
Performance Based Buydown) program is for systems under 100kw, which
encompasses most of residential systems. In the EPBB program, you get
an instantaneous rebate as a check shortly after having your system
installed and inspected. The
EPBB calculator will provide you with
the rebate amounts you can receive based on different configurations.
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Q |
Would
a 3kw system deliver exactly 3kw? |
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Not exactly. The reason
is, there are many factors affecting the output of a system. First,
there is the efficiency of panels and inverters, then the orientation
of the panels, shading factors, the position of the sun. Considering
this list of factors, the solar system's output will probably be
80-85% of the nominated system capacity at the brightest time of the
day. But not to worry! The experts take this into account and size
your system accordingly. You don't really loose any of your savings,
because they are all calculated in detail in advance. |
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Q |
What
is NHSP and CSI? |
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The California Solar
Initiative is the general name for the governmental support on the
solar projects. However, CSI is also used to distinguish between
existing home programs and new home programs, which are slightly
different. The CSI programs (PBI and EPBB) are for existing homes and
commercial projects and are currently (May '07) handled by the utility
companies. The program for new homes is called New Solar Homes
Partnership Program (NHSP), and is handled personally by CEC. Why?
That is not something we can answer. |
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Q |
What
is the standard rebate rate? |
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The standard rebate rate
for EPBB is what the state would pay you for your solar system per
watt under "ideal conditions". The current (May '07) standard
rebate rate is $2.50/watt. This is to change gradually (so better be
fast to get the most!). Will you be getting $2.50/watt of your
installation? Not unless your system is 100% efficient and you are
living in Orange County. The
EPBB calculator will ask you several
questions regarding panel efficiency, orientation, etc. and your
overall performance will be evaluated. Based on your overall performance your
rebate will be calculated. |
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Q |
What
is
Design Irradiance? |
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The Design Irradiance
represents the amount of energy per second that the sun provides at a
given location, usually represented by Latitude and Longitude
coordinates. In areas such as Denver, CO, or Bozeman, MT, where the
elevation is significantly higher than sea level, the amount of energy
per second tends to be greater than 1000 W/m2. In areas like Seattle,
WA, or Portland, OR, where cloud cover is present for much of the
year, the amount of energy per second tends to be smaller than 1000
W/m2. The value 1000 W/m2 is the average value for the world, near sea
level. If you want to find more detailed information you can look at
the
National Renewable Energy Laboratory website. (Taken from
SMA-America '07.) |
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Q |
What
is the Module Nominal Output Power (Module PNOM)? |
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This is the nameplate
rating or nominal output power of the panel under Standard Test
Conditions. When modules are mounted in a PV system they are usually
operating at temperatures that far exceed the temperature used for the
Standard Test Condition. For more information about the differences
between Standard Test Conditions and real operating conditions please
read STC, PTC, and Power Production from our FAQ's section. The power
that is produced from a PV panel is inversely proportional on the
temperature of the PV cells. At higher temperatures, the PV panel will
produce less power than its nominal STC rating. (Taken from
SMA-America '07.) |
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Q |
What
is the Module Open Circuit Voltage (VOC)? |
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This is the open circuit
voltage of the panel when it is exposed to sunlight. A PV panel will
produce electricity from the sun because of the photoelectric effect
which converts the sun's energy into electricity. The open circuit
condition is applied to the inverter when the panels are exposed to
any sunlight, even indirect, and the inverter is not producing power.
This value is highly dependent on the temperature of the panel, and
like nominal power decreases with increased temperature. (Taken from
SMA-America '07.) |
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Q |
What
is the Module Maximum Power Voltage (VMP)? |
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This is the voltage that
the panel produces when exposed to sunlight and a complete circuit
with a load impedance is attached in such a way that power produced by
the panel is at its maximum. This voltage is again determined using
the Standard Test Conditions, and like the Open Circuit Voltage, is
highly dependent on the temperature of the panel. Like the Open
Circuit Voltage the Maximum Power Voltage is reduced with increases in
temperature. (Taken from SMA-America '07.) |
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Q |
What
is the
Module Short Circuit Current (ISC)? |
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This is the current that
is produced by a PV panel when the load circuit impedance is reduced
to zero Ohms, creating a short circuit. This rating is again
determined using the Standard Test Conditions and is subject to change
based on the temperature of the panel. Unlike voltages and power, the
current is usually positively effected by temperature, such that the
current will increase with temperature. This increase is very small
compared to the reduction of voltage with temperature. (Taken from
SMA-America '07.) |
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Q |
What
is the Module Maximum Power Current (IMP)? |
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This is the current that
the panel produces when exposed to sunlight and a complete circuit
with a load impedance is attached in such a way that power produced by
the panel is maximum. This current is determined using the Standard
Test Conditions, and like the Short Circuit Current is subject to
change based on the temperature. The Maximum Power Current is affected
by temperature in the same way as the Short Circuit Current. (Taken
from SMA-America '07). |
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What
is the Module Temperature Coefficient of Voltage (VKvoc)? |
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In order to determine how
much the panel's output voltage is affected by changes in temperature,
we need to know the Temperature Coefficient of Voltage. The magnitude
of the coefficient is used in the String Sizing Calculations to
determine how much, or how little, changes in temperature will affect
the panels. For the maximum input voltage calculation, the Temperature
Coefficient of Voltage is used with the low temperature to determine
the maximum number of panels that can be used in a string. For the
minimum input voltage calculation, the coefficient of voltage is used
with the high temperature to determine the minimum number of panels
that should be used. Any configuration between these two extremes can
be used as long as they do not exceed the maximum current or maximum
power input thresholds. (Taken from SMA-America '07). |
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Q |
What
is the Module Temperature Coefficient of Current (IKimp)? |
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In order to determine how
much the panel's output current is effected by changes in temperature,
we need to know the Temperature Coefficient of Current. Like the
Coefficient of Voltage, the magnitude of the Coefficient of Current
represents how much, or how little, changes in temperature will affect
the performance of the panels. You will notice that the Coefficient of
Current is typically much smaller than the Coefficient of Voltage,
usually between 10 and 100 times smaller. The Temperature Coefficient
of Current is used with the highest temperature selected to determine
the maximum number of strings that can be paralleled into the
inverter. Each string must have the same number of panels. As long as
that number fits within the voltage window specified by the minimum
and maximum input voltages, this should result in a system that will
function well. (Taken from SMA-America '07.) |
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Q |
What
is the Module Temperature Coefficient of Power (PKpmp)? |
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In order to determine how
much the panel's overall output power is affected by changes in
temperature, we need to know the Temperature Coefficient of Power.
Like the Coefficients of Voltage and Current, the magnitude of the
Coefficient of Power represents how much, or how little, changes in
temperature will affect the performance of the panels. As you will
notice, the Coefficient of Voltage is usually much larger, 10 to 100
times larger typically, than the Coefficient of Current. This means
that the Coefficient of Power is influenced more by the Coefficient of
Voltage than the Coefficient of Current. The maximum input power is
actually a fuzzy limit. This means that if you were to exceed this
value with a given number of panels, you might not actually damage the
inverter, as you would with too much voltage or current, but you may
see decreased performance. For more information about why the limit is
fuzzy, please see this discussion about the different ways to rate
panels. For more information about the possibility of degraded
performance, please see this discussion about the derating mode.
(Taken from SMA-America '07.) |
