Photovoltaic cell energy output:

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Photovoltaic cell energy output Maximum power
output, Pm Vm x Im
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At solar noon on the equator on the Fall or
Spring Equinox E 1000 w/m2. (This is about as
high solar irradiation as you can expect). At a
typical 12 efficiency would then get a 120 watts
per m2 of solar panel.
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For Appledore Island a more reasonable irradiance
value is 200 250 watts/m2. So typical power
output would be 24 30 watts/m2 during daylight
hours.
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For Appledore Island Average annual solar
radiation 4.51 kWh/m2-day Average summer
solar radiation 5.23 kWh/m2-day Average
winter solar radiation 3.56 kWh/m2-day
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Note this isnt Appledore
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Typically, the angle of the solar array is set
within a range of between site-latitude-plus 15
degrees and site-latitude-minus 15 degrees,
depending on whether a slight winter or summer
bias is desirable in the system. Many solar
arrays are placed at an angle equal to the site
latitude with no bias for seasonal periods.
Latitude for Appledore Island 42.96oN
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PV output is low voltage (Direct Current) -
usually 6 to 24 volts. The most common output is
intended for nominal 12 volts, with an effective
output usually up to 17 volts.
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To design a system, the total amount of solar
radiation energy is expressed in hours of full
sunlight per m², or Peak Sun Hours (PSH). This
term represents the average amount of sun
available per day throughout the year. PSH has
units of kWh/m2-day. It is assumed that direct
solar radiation for one hour 1kWh/m2. Thus
PSH actually equals the number of full sun
hours in a day. For Appledore PSH for summer was
shown in a previous slide to be 5.23
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Design of number of panels required depends on
electrical demand. For Appledore typical days
power demand 30 kw (This does not include
power for R.O. and main saltwater pump). Panels
are rated by wattage.
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Total electrical demand variation (including R.O.
and main seawater pump) is shown in the following
graph.
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For example, a BP 3160 solar panel has the
following specs.
Max power output 160 w Voltage
35 volts Current 4.5 amps Size
31 x 63 in.
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Since the sun is not full strength for full day
the 160 watts output cant be realized. Energy
output from panels 160 watt x hours sun For
the summer this equals 160 x 5.3 848 Wh (per
panel)
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Energy requirement for Appledore is 30kw times
the hours of electricity use. Assume this time
is approximately 12hrs. Energy requirement 30
kW x 12hrs 360 kWh
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Number of panels required
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For the BP 3160 panels this number of panels
would occupy an area of about 75ft x 75 ft. The
total ground coverage would be reduced by tilting
the panels. 45o tilt reduces area by 0.707
0.707 m
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Inverters are required to change the DC output of
the PV to AC. The quality of these inverters
varies (by price). Some typical outputs follow.
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Here is a inexpensive inverter output
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Here is a expensive inverter output without load
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Heres an expensive inverter output with load
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• Typical inverter
• 12V to 110V
• 6kW capacity
• Eff. 90
• Wt 30 lbs
• 9 x 6 x 26

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• Other factors to consider
• Island electrical load is not likely to be 30 kw
  for 12 hrs (likely to be lower).
• Loss of energy for the inverter. The smoother
  the sine wave output the higher the
• energy loss (approx 10 - 25). Loss of energy in
  storage batteries (approx. 20)