Distributed Renewable Energy Operating Impacts and Valuation Study

Section 5
Table 5-2
Percent Dependable Solar DE Capacity
100 MW Installation
Base Case Resource Plan
Solar DE Technology 2007 2006 2005 2004 2003 Average
Solar Hot Water 47.8% 41.8% 43.9% 46.3% 43.1% 44.6%
Daylighting:
Low Penetration Case 72.7% 64.1% N/A 58.7% 62.0% 64.4%
High Penetration Case 73.3% 66.2% N/A 59.0% 63.6% 65.5%
Residential PV:
18.4º Tilt, S-Facing 41.5% 52.5% 48.4% 41.1% 42.3% 45.2%
18.4º Tilt, SE-Facing 28.4% 40.8% 36.5% 28.7% 32.5% 33.4%
18.4º Tilt, SW-Facing 54.2% 63.4% 58.8% 53.1% 50.7% 56.0%
Commercial PV:
10º Tilt, S-Facing 43.7% 55.2% 50.8% 42.9% 44.3% 47.4%
0º Tilt, N/S Single-Axis Tracking 73.1% 75.3% 74.0% 68.3% 60.4% 70.2%
Diminishing Dependable Capacity
In addition to the analysis of dependable capacity for a small quantity (100 MW) of solar DE, an
analysis was performed to determine the amount of dependable solar DE capacity that might
diminish as installation of solar DE resources increased on the APS system. As discussed in
Section 4, as more solar DE resources are added to the electric system, the APS system peak
demand will be pushed to a later hour in the day (e.g., the summer peak demand will move from
the traditional hour ending at 5:00 PM to 6:00 PM, or even 7:00 PM). Because the output of the
solar DE resources becomes significantly less as the available sunlight diminishes at dusk, the
delay of the peak hour to a later hour could significantly diminish the ability of the solar DE
resources to meet the electric system peak demand and satisfy reliability planning criteria.
To analyze this effect, the LOLE analysis was repeated but this time using incrementally
increasing quantities of solar DE resources. This LOLE analysis was performed by APS for each
technology comprising the solar DE cases. Computational requirements limited the analysis to a
single historical year, 2006, for daylighting, and 2005 for the other solar DE technologies.
As depicted in Figure 5-2, as installed solar DE resources became large relative to the peak
demand of the APS system, the dependable capacity of the solar DE resources declined. The
commercial single-axis tracking PV technology (simulated for the single-axis sensitivity) is most
notably affected by the impact of diminishing capacity dependability with increasing
implementation. Solar hot water technology is the least affected. These effects can be
understood by considering the typical daily profiles for the solar DE technologies.
Since solar hot water incorporates natural storage characteristics, the dependable capacity of the
solar hot water technology is not affected significantly by the coincidence of available sunlight
with the electric system peak. The electric load avoided by a solar hot water system is minimal,
since a traditional electric water heater operates throughout a 24-hour period, and commonly
after sunset.
5-8 R. W. Beck, Inc. Arizona Public Service