03 July 2012

35 Megawatts

What does 35 megawatts of solar (roughly 6,000 times what's on our roof) look like? This:


Austin's first solar farm opened earlier this year, and since it's open to visitors, you know I had to check it out. The
Webberville Solar Farm is waaaay out east of town, on a 380-acre parcel near a substation (which kept to a minimum the transmission infrastructure that needed to be built to accommodate all of the new generation). The project is a collaboration among several different entities, as the sign at the entrance indicates:


Austin Energy is committed to purchasing the energy generated at the site -- expected to be over 50,000 megawatt-hours each year -- for the next 25 years, as part of its goal of 30% renewable energy. (I hear they have another solar farm in the works, too.) Solar power is optimal for a location like Texas, where there is ample sun, especially at times of peak demand. It's no secret that we need more generation capacity, but it doesn't make sense to spend $400 million to build a traditional power plant whose power will only be needed from 4-7 p.m. during the hottest summer months; solar farms (and rooftop systems -- called "distributed solar") are ideal because they happen to generate most of their power during the times we need it most.

But back to the stars of the show:



The panels are mounted on frames that allow them to pivot to follow the sun throughout the day. Every few minutes, we could hear one segment or another pivot a degree or two. The farm has this great observation deck for viewing the site:


Like the
wind farms we drove through earlier this year, the solar farm is pretty expansive, but this map helped to give context to its acres and acres of panels:


(Although now that I compare the map to the aerial picture at the top of the post...they're not a match. Hmmmm.)

Each of the red notations within the solar field on the map (the ones that start with "E") indicates the location of an inverter (which converts the power being generated by the panels from direct current (DC) to alternating current (AC)). Unlike our inverters, which are the size of a car stereo and each convert the power from a single panel, these inverters are huge because they serve entire segments of the farm. There they are in the white container buildings.


Solar power is low-maintenance compared with traditional forms of energy, but there are two maintenance issues at this farm. The first, which is an issue for any solar array, involves cleaning the panels. They explained that they hadn't yet cleaned the panels (the installation of which began last summer), but they are closely monitoring the panels' production and will only clean them when it stops being cost-effective
not to.

The second issue is more site-specific: weeds.


When the rows and rows of panels were constructed in the midst of last summer's drought, weeds weren't an issue, but with this spring's rains, some of them have grown tall enough to begin to block the bottoms of the panels, compromising solar production. But they have a plan to deal with the weeds, and that plan is...sheep! Solar sheep!

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