MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA
description
Transcript of MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA
![Page 1: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/1.jpg)
MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA
Steve Pulver Daniel Cormode
Alex CroninU of A
Dirk JordanSarah KurtzRyan Smith
NREL
![Page 2: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/2.jpg)
Outline• Goal: Measure degradation rates for
systems that don’t have irradiance data• Approach: Use 20 PV systems from TEP• Step 1: Quantify relative degradation
rates• Challenge: Relative vs. absolute rates• Step 2: Bayesian statistics to derive
absolute degradation rates
![Page 3: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/3.jpg)
TEP solar test yard
Missing POA irradiance sensors
![Page 4: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/4.jpg)
Daily Final Yield, 2005-2009
Daily and annual insolation can vary by more than the degradation rate
Variation in daily insolation
![Page 5: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/5.jpg)
Removing irradiance variation
Define Daily Relative Final Yield as:Daily Final Yield divided by field average final yield
Daily Final Yield Daily Relative Final Yield
![Page 6: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/6.jpg)
Relative rates of change
Provides an easy comparison between systems, and can be calculated with low uncertainty
![Page 7: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/7.jpg)
Rate of change (percent per year)2 systems
Example: only two systems…
relative
absolute
![Page 8: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/8.jpg)
2 systems
5 systems
10 systems
There appears to be a higher probability of low degradation rates
Adding more systems…
![Page 9: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/9.jpg)
Rate of change (percent per year)17 systems
Translating to absolute…
relative
absolute
In a large dataset, possibly there is a system that changes very little
Assume the best system doesn’t degrade?
![Page 10: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/10.jpg)
Challenging scenarios
Best performing system degraded by 0.5 (percent / year)
Outlier at 2.0 (percent / year)
Normalizing by the best system may not be the best solution
![Page 11: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/11.jpg)
Our analysis
Starting point: a PDF (Probability Distribution Function) to describe the absolute degradation rate.
![Page 12: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/12.jpg)
Histogram of our dataset(relative rate of change)
Histogram of a much larger data set(absolute rate of change)
Comparison to histograms
Exponential PDF appears to be capable of handling both our dataset and the larger dataset
![Page 13: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/13.jpg)
Results depend on the function used
Amount to shift relative rates
![Page 14: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/14.jpg)
Consistent results between rates measured w/ and w/o irradiance data, and similar uncertainties between the two methods.
Absolute rates of change
![Page 15: MEASURING DEGRADATION RATES WITHOUT IRRADIANCE DATA](https://reader036.fdocuments.us/reader036/viewer/2022062305/56815ebf550346895dcd4564/html5/thumbnails/15.jpg)
Conclusions
• We determined degradation rates without irradiance data.
• Relative degradation rates provide a useful comparison between systems
• Absolute degradation rates can be obtained from relative rates