Newsletter No. 5


Today, Occidental's 1 MW solar array is 2.5 years old.

Good Morning Occidental!

Today, Occidental's 1 MW solar array is 2.5 years old. Normally I only do this once a year but in honor of our focus on sustainability I thought I send out a mid-year report.

To date our array has produced 4.69 GWh of clean, renewable energy, 12.6% of all of the energy we used over the same time period. Because of the array 5,565 tons of CO2 did not enter our atmosphere, the equivalent of not driving an average passenger vehicle 7.7 million miles or 310 times around the earth! For other equivalencies you can punch in 4.69 GWh = 4690000 kWh here.

I am often asked if our array is showing any signs of aging. This graphs shows a side-by-side comparison of our monthly output since the array started operating.

Start with dark blue. The dark blue bars show the monthly production (in MWh) in 2013. The first month is a little lower than normal because of a slow start. Light blue is 2014 and green is 2015. April, June, July and August provide 3 year comparisons. There is no obvious trend. The panels are expected to degrade at up to 0.5% per year but with month-to-month variations we would never be able to observe that with this baseline.

But one of the months is not like the others, May 2015. Two days before Mother's day this year a mylar balloon or a squirrel (eww!) may have caused a "flashover" which caused a brief voltage dip on campus. That dip damaged the motherboard of our big 500 kW inverter*. Despite a maintenance contract with the college's electrical contractor it took an entire month to get a replacement. Many photons died in vain on the black panels of the hillside array in May. That maintenance issue cost us about 5.5% of the energy we could have produced this year, ~$12k in lost savings and $8k for a replacement board. We've had many other adventures with the inverters. The bottom line is that inverters, shading and dust constitute most of our losses, are preventable and much larger than panel degradation. At Oxy being green now also means being serious about maintenance!

On the financial side of things, our electrical bills have been lower these last 2.5 years due to the energy generated by the solar array. Since "first light" on March 4th 2013 the array has saved the college $672k on a purchase price of $3.423M. My accounting now includes any expenses we've incurred because of the array. 2.5 years in we are, by my calculation, 17.3% of the way towards paying of the array.

An app can be found, for the iPhone, at the Apple's App Store by searching for AlsoEnergy. I'll leave you with this. My favorite photo of the solar array by my favorite campus photographer, Marc Campos.

Footnotes -

*Solar arrays produce DC (direct current) electricity but we use AC (alternating current) electricity on the grid. An inverter is an electrical device for converting one to the other. They also do other nifty tricks. Our inverters are in a big steel cage next to the upper practice field. They are the only part of our array that produces any sound, a dull 60 Hz hum.