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| What exactly does a solar electric system do? |  |
| A solar electric (PV) system is a semiconductor-based technology used to convert sunlight energy into direct current (dc) electricity, consisting of several components including: solar PV panels that convert sunlight into direct current (DC) electricity; the inverter that changes the DC into normal household alternating current (AC) electricity; and disconnect and circuit protection apparatus. Solar electric panels use no moving parts and consume no fossil fuel. In addition to the solar electric panel, a grid-connected solar electric system requires an inverter to change the DC electric output from the panels into 120 V ac current synchronic with the utility power. Other components of a system include switches and circuit protection apparatus. |
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| What does grid-connected mean and why is it important? A grid-connected system is connected to the electric utility grid. A grid-connected solar electric system relies on the electric grid for power when the demand for electricity is greater than the amount coming from the PV panels. Non-grid connected or “stand alone” systems utilize batteries for electrical energy storage. |
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| What are the environmental benefits of using a PV system? | |
| The principal environmental benefit of using a solar
electric system is the reduction in emissions from electric power
coming from other (fossil fuel) generation sources.
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| What happens when the sun is not shining? | |
| Solar electric cells produce electricity in proportion
to the intensity of the sunlight striking the cell. If there is no
sunlight, no electricity is produced. An overcast sky produces little
or no electricity.
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| Will I still have electricity when the panels are not producing power? | |
| Yes, in a grid-connected solar electric system, the
electric grid provides all of the electricity needed above the amount
being provided by the PVs. This operation is automatic
and does not require any action by the homeowner. |
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| In the event of a power outage, will a grid-connected solar electric system provide back-up emergency power? | |
| No, a grid-connected solar electric system can only
operate if the grid is in operation. For safety reasons, the solar
system automatically shuts down in the event of a power failure.
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| What is the size of most residential solar electric systems? |  |
| Residential solar electric systems typically range between 1 kilowatt (kW) and 4 kW. The sizes of commercial and industrial systems are limited by the site, cost of grid electricity and the availability of funds. | |
| How much maintenance do solar electric systems require? | |
| Solar electric systems require little annual maintenance
other than adjusting the mounting rack for seasonal changes, clearing
debris from the panel and checking the electrical connections for
corrosion. These maintenance items are usually within the capabilities
of the owner of the system and do not require the services of a trained
technician.
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| What is the expected life of a solar electric panel? | |
| The expected life of a solar panel is over 25 years
with the industry standard warranty becoming 25 years.
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| What is the estimated cost of the electricity produced? | |
| According to the United States Department of Energy,
the average cost of an installed solar electric system can range from
$8 – $10/watt, or $10,000 to $50,000 respectively for a 1 kW
or 5 kW system before any applicable
rebates are applied. Solar electric systems are a long-term investment
in your future energy needs. One way of thinking of your investment
in a solar electric system is that you are buying a portion of your
next 25 years worth of electricity needs all at once.
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| Why is the angle of the solar electric panel so important? | |
| The energy density of the sunlight striking the solar
panel is directly related to the angle of the sun relative to the
surface of the solar panel. This angle is called the angle of incidence.
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| What can be done to increase the production from a solar electric installation? | |
| Adjustable mounting racks and tracking systems are sometimes
used to increase production from a PV array by reducing the angle
of incidence. Seasonally adjustable mounting racks allow the panels
to be adjusted for the seasonal changes in the height of the sun.
Tracking systems further reduce the losses, due to the angle of incidence,
by adjusting for optimum panel position throughout the day and season.
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| What are the characteristics of a good PV site?
A good site must have significant southern exposure. This exposure must be free of obstructions (unlike solar thermal applications, the output of a shaded solar panel is not proportional to the amount of shading and approaches zero output during the shaded period). A good rule of thumb to use to site a solar electric array is to have excellent exposure to the sun during the peak solar hours of 9 m. to 3 p.m. A site survey using a solar pathfinder (see photo at right) is an excellent method to determine solar access for a location. The pathfinder is used to determine the position of the sun for all of the times and seasons of the year and allows the user to quantify the reduction in energy production due to shading. |
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| Why aren’t there more PV installations? | |
| The principal limitation of PVs is their cost, which is higher than the cost of electricity from most other sources of generation. | |
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