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Following up on developments in the solar energy sector does not usually involve contacting the Department of Corrections and Rehabilitation or paying a visit to a penitentiary. But the recent news of a PV module field coming online at one of California's prisons piqued my journalistic interest, prompting a call to the folks who work for the agency that locks up those who run afoul of the Man. During our conversations, they invited me to go to prison...to see the new solar installation for myself.

I have yet to take them up on their offer.

A couple of weeks back, the private-public partnership of SunEdison and the California DCR announced that a 1.18-MW solar array had been activated on May 2 at Ironwood State Prison, located near Blythe in the Mojave Desert in the southeastern part of the state. SunEdison, which financed and built the installation, will also operate it as part of a solar power services agreement (SPSA), under which the CDCR will buy the energy produced at rates equal to or less than current retail prices.

Ironwood, great name for a prison, great place for PV array. (Photo courtesy: Zinn Photography/SunEdison; remix by TC)

It's not the first California prison to go solar. Chuckawalla Valley State Prison, less than a mile from the Ironwood facility, activated its 1.16-MW system in June 2006 and has produced 3.7 million kilowatt-hours of juice so far. Ironwood is expected to convert enough photons into electrons in its first year of operation to hit or exceed the 2.4 million kWh mark.

Nor will Ironwood be the last state pen to be rigged for solar and reduce its carbon hoofprint. Harry Franey, head of the CDCR's energy management and sustainability section in its facilities management division, told me that 10 more adult prison sites are being actively evaluated for similarly scaled (1-MW-plus) solar installations. "A year from now, most of those 10 sites [could] be under construction," he said.

Four companies--including SunEdison--are on the short list of contractors bidding on those upcoming projects. And it doesn't stop there: A total of 31 additional adult and eight youth facilities--basically the entire California prison system except for the conservation camps--are under consideration for PV in the longer term, according to Franey.

Ironwood's 13-acre PV plot features a key improvement over the Chuckawalla solar farm, said Franey. While the original installation relies on fixed, ground-mounted, south-facing Sharp Solar panels, the second big house's 6200-plus modules--a mix of 170-, 180-, and 190-W Evergreen Solar Spruce Line models (with up to 12.7% conversion efficiency and 32.8 V-AC capability)--are hooked up on computer-controlled, single-axis tracking mechanisms.

"They find the sun earlier in the day, maximize the output much earlier, and continue to perform better later in the day" than the Chuckawalla panels, he explained. "I expect better performance than the output stated."

Franey said it took about a year to get from the contract signing to actually flipping the switch on the solar-power plant, but once SunEd started putting the panels in, "the system went in fast. It almost took 'em longer to stake out the field than to lay it out. There was about six months of actual onsite construction, including three months to lay out [the modules.]"

The Ironwood PV site is expected to provide about 10% of energy needs on the kilowatt-hour side, but more like 25% on the pure-kilowatt side, he calculated, adding that peak demand will be about 4 MW.

So how does that 2.4 million kWh of expected first-year electricity from those desert sun-baked Evergreen modules break out on a per-prisoner basis? It calculates to approximately 530.5 kWh annually, or 1.45 kWh per diem, for each of the 4524 minimum- and medium-security male inmates doing time at Ironwood.

What's the amount of electricity bought by the average residential customer in California? About 6500 kWh.