First year performance of a 20 MWac PV power plant

After one year of continuous operation in Ontario, Canada, the actual performance of the Sarnia 20MWac power plant can be compared to both the long-term energy prediction and the expected energy for the operating year 2010. The long-term prediction uses satellite meteorological data and loss assumptions and the PVSYST system simulation tool to estimate the behavior of the power plant over a "typical" year. Typical meteorological input from satellite data is discretized on a monthly basis; therefore the monthly Performance Ratio (PR) is an appropriate metric for comparison. Our comparison shows that the prediction data is in line with the actual power plant PR during normal operation. However, energy lost due to snowfall remains one major prediction difficulty. Based on the first year's data at the Enbridge's Sarnia 20 MW ac power plant, the power plant is operating within 2.1% of the long-term prediction. Using the one year of on-site meteorological data, the expected energy of the site for 2010 can be found by rerunning the prediction with hourly measured data. At this time-step, specific measurement points within the power plant can be assessed by simply comparing measured to expected values, including the DC and AC energy at the inverters as well as the module temperature and inverter efficiency. The estimation of the modeling error at each of these measurement points shows that there is no single driver of the overall modeling error during normal operation, but also shows that improvements are possible. Actual energy from the Sarnia 20 MW ac power plant was 0.6% more than expected based on the expected energy for the 2010 operating year.