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PV ONLY makes sense when electricity is consumed
efficiently! |
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Consider an Energy Audit. |
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Consider energy efficiency when choosing or
building a home. |
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Use passive solar techniques to reduce power
requirements. |
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Insulation. |
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High Efficiency Appliances. |
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Window Treatment. |
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Roof Treatments. |
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Time of use rates. |
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Shade. |
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Architecture. |
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Grid-Tie. |
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Grid-Tie with Battery Backup. |
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Stand Alone. |
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What Do you need it to do ? |
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How much power do you need ? |
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What is the daily / yearly profile of power use? |
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What happens if the power (Utility or PV) system
fails ? |
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Can I run my Air Conditioner ? |
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How much does a Solar System Cost ? |
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What is the payback time ? |
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Can I spin my meter backwards ? |
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How do I get more Information ? |
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In principle yes, in practice it is not
economically (or in the case of keeping the AC on backup power —
environmentally) feasible. |
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In a line-tie system then the solar power you
generate will offset some of the power needed to run the AC. |
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Currently the installed cost is of the order of
$8 – $9 per (STC) Watt before incentives. |
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State and Federal tax credits are available. |
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Buy-downs, net metering (the Utility pays you
for only the net power they supply you with) etc. can in some states (CA)
reduce the cost to about $4 /W . |
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With a Solar PV system you are buying power at a
known fixed cost . |
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Payback can only be calculated by guessing
figures such as energy inflation rates, etc. |
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Again, using energy efficiently is the only way
to win in the long-term. |
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Yes. If you generate more power than you use,
the power can be sold back to the utility. The rate that they pay depends
on the utility company, and the local state laws and requirements. |
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Ask home owners who have PV, they are normally
more than happy to explain their system and how to get one. |
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Call your Utility company. |
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Find a local PV dealer in the yellow pages |
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There are many good sources of general and
technical information on the Internet. |
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Check PV and systems manufactures sites on the
internet. |
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www.AZSolarCenter.com |
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Solar Today and
Home Power magazines, are the most widely available sources of
printed information on PV systems. Both have a wide range on information
and advertising. |
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Simplest and cheapest entry. |
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Displace power usage from Utility. |
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Sell back
(Net Metering). |
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No backup if Utility power fails. |
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PV Array |
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Convert Sunlight in to electricity. |
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Inverter |
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Change DC from Solar Array to 120V AC
electricity used by the utility. |
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Safety Switch |
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Utility can shut system off in emergency. |
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Provide local power when the Sun is shining. |
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Displace power that would have been used from
the Utility. |
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Sell power back to utility if more power is
produced than used. |
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More flexibility on power management. |
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Provides limited power for critical loads incase
of power failure. |
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Requires Battery maintenance schedule. |
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Batteries |
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Store Energy for night time or power failure |
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Battery Cutoff Switch |
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Shutoff batteries for maintenance and safety |
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Other (depends on Inverter) |
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Solar Array |
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Inverter |
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Safety Switch |
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Same as Grid Tie |
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Provide back-up power for critical loads incase
of utility power failure. |
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Back-up time and power depend on Battery and Inverter choices (Batteries can
be charged from Utility if needed). |
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Solar power available depends on Array and
Inverter choices. |
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Convert Sunlight to electricity |
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Solar Modules will be very similar for all
systems. |
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Larger modules are normally cheaper in terms of
$ per Watt. |
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Angle |
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Modules should be oriented to face the Sun. |
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Module Temperature |
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The Modules produce more power when cooler. |
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Aesthetics |
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The mounting and color of the modules can
sometimes be chosen to blend with the architecture. |
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Trackers |
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Tracking the Sun increases the amount of power
from an array. |
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Developments in modules and engineering
practices that allow PV to form an integral part of a buildings structure. |
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Convert DC (Direct Current) electricity to AC (Alternating
Current) electricity |
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Power |
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Maximum power the inverter can handle. |
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Efficiency |
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How efficiently does the inverter convert solar
power to utility power? |
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“Night time power” |
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How much power does the inverter consume from
the grid when there is no Sunshine? |
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Xantrex ST-XR — low voltage (48V) |
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Sunny Boy — high voltage (350V) |
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48VDC Line Tie Inverter |
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Built-in system display |
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Optional Remote Display |
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1kW, 1.5kW, 2kW & 2.5kW |
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Early ST inverters had problems which seem to
have been solved in the XR series |
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High Voltage / high efficiency. |
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Can be used in 3-phase circuits. |
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Available as 1.8kW and 2.5kW. |
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Power |
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How much power do you need? |
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Battery charger |
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How flexible is the battery charging? |
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Generator control |
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Will the Inverter control a generator ? |
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Add ons needed / supplied |
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What other equipment is needed? |
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Xantrex /Trace SW Inverter / Battery Charger.
Can be used Grid-Tied with GTI interface. |
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Available in 4kW and 5.5kW |
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Store DC electricity for later use |
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Use ONLY deep-cycle batteries! |
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Wet batteries need to be checked at least every
6 months. |
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Check water and tightness of connectors. |
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Sealed Batteries (VRLA) do not need watering,
but may not last as long as wet batteries. |
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Battery capacity is measured in Ah (Amp Hours –
how many amps can the battery provide for an hour). The larger the capacity
the more energy can be stored, and normally the more expensive the battery. |
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To calculate the amount of power you can use
from a battery you need both the Voltage of the battery and its capacity. |
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Wh (Watt Hours) = Voltage ´ Ah |
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and is the amount of Power (W) that the
battery can provide for one hour. |
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The Voltage of the battery bank must ALWAYS be
matched to the Inverter, so if you have a 24V input inverter you would need
to add batteries in groups of 4 (4 ´ 6V = 24V). |
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You should never have more than 4 Parallel
strings of batteries. The batteries
will not share the load equally, and the life of the entire battery bank
will suffer. |
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The batteries must ALWAYS be kept in a well
ventilated area. They produce Hydrogen gas, that can explode if allowed to
build up. |
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Batteries contain Sulphuric acid that BURNS SKIN
on contact. |
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ALWAYS use insulated tools or wrap electrical
tape round the handles. If you touch both + and - terminals of a battery
with a metal you will start welding, at a minimum destroying the tool and
possibly starting a fire. |
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Charge Controllers (Solar Battery Chargers). |
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Disconnects and Switches. |
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Remote controls. |
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Meters. |
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Condition the power from the solar module to
charge a battery. |
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Modern units may be “Maximum Power Point
Tracking (MPPT)” may provide up to 30% more power to the battery. |
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Can be used in parallel to add more modules to a
battery bank. |
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National Electrical Code and Utilities require
disconnects for safety of the owner and utility workers. |
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Disconnect system components for installation
and maintenance. |
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Many systems offer remote control for
convenience, and some are now starting to offer performance monitoring by
computer or over the internet. |
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Collects data about system performance, and
sometimes local weather. |
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Can be very useful for isolating system
performance problems. |
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Often linked into remote control packages. |
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PV: Photo Voltaic |
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The physical principal behind the conversion of
light to electricity. |
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BIPV: Building Integrated PV: |
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The PV modules are integrated into the structure
of the building. |
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Net Metering: |
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The Utility company calculates the amount of
electricity they provided – the amount of electricity you put back to the
grid, and change only for the net electricity provided. Time scales for the
calculation change with utility company. |
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Grid -Tie / Line-Tie: |
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A system that can provide power back to the
utility company lines. |
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Modules, Panels, Arrays: |
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Assemblies of power producing photovoltaic. |
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STC: Standard Temperature Conditions: |
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A standard test temperature for PV systems to
quantify and compare components These conditions are rarely, if ever, seen
in service. |
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NOCT: Normally Operating Cell Temperature |
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A means to try and predict real-world system
performance. |
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Solar Electric vs. Solar Thermal: |
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Solar Electric (PV) systems convert light to
electricity. |
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Solar Thermal systems convert the heat from the
Sun into hot water, or heated air. |
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Time-of-day / Time-of-Use Rate: |
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The cost of utility power can vary depending on
when the power is used. Normally more expensive during the day (especially
afternoon) and cheaper at night. |
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UPS: Uninterruptible Power Supply |
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Provides
power when the utility grid fails. |
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VRLA Batteries: Valve Regulated Lead-Acid
Battery |
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Sealed battery requiring no maintenance other
than checking connections. |
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Gell Cell Batteries: |
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Sealed battery with the electrolyte in the form
of a gel. |
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AGM Battery: Advanced Glass Mat |
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Another form of spill-proof sealed battery. |
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Wet Batteries: |
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Lead-Acid batteries that have caps that allow
the water level to be checked and filled if needed. |
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L16, Group Number (e.g. Group 27), Golf Cart,
etc. Batteries: |
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These refer to the physical size of the battery,
which also has an effect on both the Voltage and storage capacity of the
battery. |
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AC (Alternating Current) |
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The current in the wire changes value 60 times a
second (60Hz). |
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AC is
easier to transmit over power lines without loss. |
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AC tends to be safer than DC as if you touch it
it will throw you away. |
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DC (Direct Current) |
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Voltage and current have steady (or very slowly
changing values) |
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Batteries, and Solar modules produce DC. |
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DC can be very dangerous, as it will cramp
muscles stopping you from moving away. |
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Inverter: |
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Converts DC to AC and often changes the voltage
too. |
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Sine Wave: |
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The shape of the electrical wave-form varies
smoothly, like the Utility power. ONLY sine wave inverters can be
grid-tied. |
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Square Wave: |
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The shape of the electrical wave-form changes
abruptly from one voltage to another. (only found in very old inverters) |
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Modified Sine / Square Wave: |
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A compromise wave-form found in cheap inverters.
Should only be used for powering simple loads (e.g. motors). Appliances
powered from a modified wave-form can buzz. |
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AZ Solar Center (www.AZSolarCenter.com) |
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Arizona Department of Commerce – |
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Energy Office (www.commerce.state.az.us/energy) |
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National Renewable Energy Lab (www.NREL.gov) |
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California Energy Commission (www.energy.ca.gov) |
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Florida Solar Energy Center (www.fsec.ucf.edu) |
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DOE (www.doe.gov) |
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Andrew Jones |
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Kyocera Solar Inc. |
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Kyocera Corp. |
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Wade Webb (Solar Webb) |
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Sundance Solar |
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Sandia National Lab and NREL |
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Exeltech |
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SMA America |
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Xantrex |
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Dan Aiello |
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SouthWest Wind power |
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Notes