Distributed Renewable Energy Operating Impacts and Valuation Study

Solar Characterization
warranties. For example, one manufacturer offers a 10-year warranty on a 15-kW inverter for
about $1,600 (about $0.10 per watt). However, for the purposes of this Study, no O&M costs
were assumed for PV systems.
PV Technical Considerations
To fully understand the impact of PV on the utility grid, it is important to consider some
important technical characteristics of PV systems.
PV systems are designed to trip off-line when certain disturbances occur on the utility feeder. A
situation could occur on a feeder where the PV system is generating a significant portion of the
load, but a disturbance might cause the feeder to trip momentarily and then reclose. In this
situation, the PV generation could be off-line for five minutes, causing the feeder to be
overloaded. Such a situation could occur during a significant and fast moving thunderstorm
event, which typically occur during the “monsoon” season in Arizona.
Another disturbance of the electric system could occur that may affect the transmission system,
such as an electrical fault or “trip”. During such an event, the PV inverters would ideally be able
to ride through a transmission system disturbance lasting four cycles. However, if such an event
lasted longer than four cycles, the inverters may drop the PV systems. Additional information to
measure the actual trip characteristics of inverters is provided in Section 3 of this Report.
2.2.2 Model Description
Performance Modeling Approach
The basic modeling plan for PV is illustrated in Figure 2-4. Empirical data is generally not
available for the range of orientations to be considered in this Study, especially in an 8,760
hourly format (the total hours in a year). As a result, most of the analysis is based on computer
simulations. The key variables addressed in the computer model were:
• Typical system size by customer type
• Range of orientations
• Range of tilt
• Various technologies
• Location-based weather impacts
Figure 2-4: PV Modeling Plan
INPUTS PROCESSING OUTPUTS
Measured PV System Data
(for model
calibration)
Scaling to x kW
Hourly (8760) PV System
Generation Projections
Typical Meteorological
Year (TMY) Weather Data
(for energy-related analysis)
PV System Model
(SAM)
Calendar Year Weather Data
(for capacity-related analysis)
Scaling to x kW
Hourly (8760) PV System
Generation Projections
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