Today, Occidental's 1 MW solar array is 11 years old. Since "first-light," on March 4th, 2013, the array has produced 19.4 GWh of electrical energy, 11.8% of the college's usage over the same time period.
In the last year the array produced 1.54 GWh of electrical energy, about 12.5% below our average of 1.76 GWh. In fact this was our lowest, yearly production. This was not due malfunctioning equipment, as discussed in last year’s Solar@Â鶹ÊÓƵNewsletter, but rather just a cloudy year.
The most recent production is shown with a bar on the right for each month and you can compare to previous years to the left. In February and March we got a lot of rain. The main loss though appears to be during a cloudy May and June.
On the financial side of things, our electrical bills have been lower due to the energy generated by the solar array. Over the last year the solar array saved the college $366k, our highest yearly savings. Wait, how could we have record low production but record high savings?! This is due to the ever-increasing cost of electrical energy. By my calculation our yearly average savings rate for electricity has grown from 18.0 cents/kWh to 22.2 cents/kWh, an average growth rate of 3.04% per year, since 2013.
This year marks a mini-milestone for us. To date the array has saved us $3.62M on an investment of $3.40M. In a limited sense then, we have paid off the array. Woohoo! Why limited? Because we could have invested that $3.40M in something else. I've always compared our savings to what we could have gotten with $3.40M in the endowment. Here is the current Array vs Endowment plot,
The red curve shows what $3.40M in the endowment did and an estimate of what it will do in the future. Remember we are at year 11 on the plot. The blue curve shows savings which are then assumed to be returned to the endowment and an estimate of what it will do in the future. Where they cross is where we can truly say the array is paid off, now estimated in year ~15. Originally we predicted the array would pay for itself in 12 years.
And the array "detected" another partial solar eclipse on October 14, 2023, see 2018 Solar@Â鶹ÊÓƵNewsletter for the first one.
On an otherwise very clear day you can see a big bite taken out of the array around 9:15 AM. Of course Oxy’s solar array was not the only one affected. Here is the CA grid () response to the eclipse,
Since most big solar is on trackers the solar production looks a bit like a top-hat normally. The green curve shows this on top of a more or less constant wind generation. The dip in the green curve at 9:15 AM is about 5 GW. You can see gas (orange), imports (red) and our battery fleet (yellow) filling in the gap to match demand in almost equal measures.