actual photovoltaic output Based on solar resource
Variations in tilt and azimuth affect PV output differently, depending on system location.
n Average Full Sun (hours/day)
annual pV output/ maximum pV output (k W/k W)
Annual PV Output / Maximum PV Output (k W/k W)
0.15
0.16
0.17
0.18
0.19
0.20
0.21
CZ2: Santa Rosa
CZ3: Oakland
SW
SW
H
S
H
H
H
CZ11: Red Bluff
H
HS
S
6.0
S: South Facing, 15 deg. tilt
S W: South west Facing, 30 deg. tilt
H: Horizontal
SW
S
S
5. 5
SW
SW
S
SW
S
S
SW
SW
S
S
H
H
H
H
S
SW
SW
S
2. 5
H
CZ7: San Diego
2.0
CZ16: Big Bear
CZ6: Los Angeles
CZ8: El Toro
CZ9: Pasadena
CZ10: Riverside
CZ14: China Lake
California is divided into 16 climate zones based on the climatic conditions. The original purpose
of these data was for use in assessing compliance with California’s energy standards for buildings.
Hourly data for global horizontal radiation and ambient temperature reported by the CEC climate
zones were used in this analysis to provide a climatologic basis for estimates of solar resource.
Source: Itron Inc.
CZ15: El Centro
FIgurE 3.
photovoltaic output Based on incentive type
monitoring data demonstrate that California solar initiative systems receiving
a performance-Based incentive may outperform those receiving
the lump-sum Expected performance-Based Buydown.
annual pV output/ maximum pV output (k W/k W)
Source: Itron Inc.
50 May 2010 SOLAR TODAY solartoday.org
CouRtEsy oF sMA AMERICA
many different types of monitoring systems are available, ranging from relatively simple systems that track only how much power is generated to deluxe
systems that track and measure weather data. The sma america carport system, for example, features a sunny sensorbox and an additional wind meter
for more accurate monitoring.
the direct relationship between solar resource and actual PV output. It also
demonstrates that variations in tilt and azimuth affect PV output differently
in different locations.
Over the course of time, debris and other matter (soiling) may accumulate on your panels and reduce power output. The photo on page 49
(top) is an example of a system with severely reduced power output due
to solar resource obstruction (in this case, birds and their droppings).
This PV system is installed on top of a barn in a dry, dusty environment;
unless the system is cleaned regularly, it will not reach its maximum power
production capability. The photo on page 49 (bottom) is an example
of a commercial rooftop system that could benefit from a regular cleaning schedule. By checking your panels for dirt and other solar irradiance
obstructions and cleaning them when necessary, you can reduce the likelihood of these types of power reductions. Monitoring will help alert you
when such maintenance is necessary.
Weighing the Monitoring options
Most modern inverters now have a display on the front panel indicating system performance parameters such as cumulative power output, aC
output, DC input and voltages. a simple, no-cost option to track how PV
system performance varies over time is to manually record the PV data from
the inverter display at daily or, ideally, hourly intervals. However, this is a
tedious and involved process.
a monitoring system with data-storage capabilities offers a more robust
and less time-consuming approach. This type of system also easily tracks
environmental factors affecting PV performance, such as solar irradiance
and ambient temperature. Such monitoring can reveal how these parameters affect the PV system’s performance.
Many different types of monitoring systems are available, ranging from
relatively simple systems that track only how much power is generated
to deluxe systems that track and measure weather data. In general, the
