Proposalto update default solar NQCs

(R.09-10-032, Phase 2)

Resource Adequacy WorkshopJanuary 25, 2011

2

Need to modify wind/solar NQC for 2012+ RA compliance years

Under current counting rules wind/solar NQC:

• Equals 70% exceedance (30th percentile) of generation over a pre-specified set of peak period

• Based on 3 years of historical data or a default value if project has no history

Issues with current rules:

• Default NQC values are not representative of new solar projects’ NQC

3

Current counting rule overstates system’s reliability

• Default solar NQC values overstate value of new solar resources because calculation is dominated by existing, gas-assisted units

• Substantial impact if method is unchanged (assume new solar NQC would be 45%)

• Impact will be large in the first year of solar addition. For 1,000 MW addition, NQC is over-stated by 500 MW (1,000 MW x (95% - 45%))

• Impact of 1,000 MW addition decreases overtime as new projects’ historical performance is reflected in the NQC calculation

• Impact of successive solar additions compound effect

Solar percentages 2007 2008 2009 Average1 0.19% 0.47% 0.33% 0.33%2 0.96% 1.16% 16.64% 6.25%3 2.80% 6.18% 17.07% 8.69%4 42.52% 66.13% 69.73% 59.46%5 80.04% 69.42% 70.24% 73.23%6 93.07% 97.42% 98.10% 96.20%7 92.17% 95.82% 96.90% 94.96%8 91.44% 95.00% 89.66% 92.03%9 83.33% 87.08% 82.73% 84.38%

10 36.19% 35.10% 41.97% 37.76%11 0.89% 0.11% 2.69% 1.23%12 0.45% 2.15% 0.02% 0.87%

Default 2011 NQC solar valuesDefault 2011 NQC solar values

Source: Caiso 2011 final NQC report, Dec 7, 2010

http://www.caiso.com/276a/276a8c14493a0.xls

Source: Caiso 2011 final NQC report, Dec 7, 2010

http://www.caiso.com/276a/276a8c14493a0.xls

4

Proposal: Revise default solar NQCs

For 2012 RA and beyond,• Replace default solar NQCs with table of values

reflecting differences in solar technology (i.e., PV fixed vs. PV tracking vs. CST) and location

• Where historical data is unavailable, use simulated hourly production from representative profiles (e.g. NREL profiles, as used in LTPP)