Distributed Renewable Energy Operating Impacts and Valuation Study

Technical Value – Distribution System
DSS Distribution Feeder Model
A more detailed loss analysis was performed on a distribution feeder to validate the system level
analysis. The APS Geographic Information System (GIS) data for Deadman Wash Feeder #4
was provided to EPRI to develop a working electrical model in the DSS tool. The model
included 295 customer distribution transformers and 1,429 customer services as well as 56 miles
of 12 kV primary conductors. The same feeder had only 5 miles of primary modeled in Feeder-
All. Customer loads were modeled by allocating the peak feeder load and scaling the 2007
hourly feeder current measured at the substation. To understand the existing conditions (without
solar DE), hourly load flows were simulated and compared to actual hourly feeder measurements
with less that 2.5 percent error in total, average or maximum kWh for the year.
To determine the impact of the projected 2025 high deployment level (High Penetration Case),
the 8,760-hour solar technology curves developed in Section 2 for 2007 weather data were
applied to random customers proportionately to the projected penetration rates as follows:
• 52 percent of residential customers with PV
• 11 percent of residential customers with SHW
• 100 percent of commercial customers with PV and daylighting (only 2 identified on this
circuit)
In addition, a sensitivity was developed for a “greenfield” case with 100 percent penetration of
each technology and single-axis tracking for commercial PV. The analysis determined annual
losses for each scenario. Additional modeling details, assumptions and results are provided in
Appendix K.
3.2.3 Model Results
System Loss Model
Based on the deployment scenarios described in Section 2 and projected annual hourly system
load profiles, the avoided demand losses that can be realized at system peak are summarized in
Table 3-1. As expected, the demand losses increase with increased solar DE generation. These
values were added to the dependable capacity provided by solar DE to calculate the total peak
load reduction and associated values.
Table 3-1
Avoided Losses (MW) at System Peak
Year
Low
Penetration
Case
Medium
Penetration
Case
High
Penetration
Case
Single-Axis
Sensitivity
2010 0.354 0.367 0.367 0.383
2015 1.986 3.635 3.635 3.808
2025 3.283 39.452 70.551 72.869
Distributed Renewable Energy Operating Impacts & Valuation Study R. W. Beck, Inc. 3-5