By Dave Christy
Sierra Nevada Public Affairs Specialist

As California teeters on the edge of rolling blackouts, Western's Sierra Nevada Region is working with customers and others to develop alternate energy sources that could help meet the state's energy needs.

Sierra Nevada's non-hydro renewable energy program is centered on solar photovoltaics that convert the sun's rays to electricity. The program comprises a 50-kilowatt PV Technology Demonstration Project at Folsom, Calif., a 78-kW PV project at Elverta Calif., and a 2-kW PV project at Redding Calif. The non-hydro program is run by Bob Parkins, energy services and PV program manager, and Krishna Shah, project manager.

Parkins is available to advise other Federal agencies in some western states interested in PV through the Federal Energy Management Program.

Demonstration project
The PV Technology Demonstration Project at Folsom, which totals 50 kW in peak power, comprises six PV arrays with five different technologies.

"Its purpose is to educate Western's power customers and the public about solar photovoltaics, provide power to Western's Folsom facility, and aid the PV industry by serving as a beta test site to field test new technologies," Parkins said. The six arrays at Folsom are:

• A 3-kW roof-integrated PV system built into the roof as opposed to being attached to an existing roof. This was the first prototype system developed by the Powerlight Corp. and was heavily monitored as a beta test site proof of concept. Western subsequently installed another 78 kW of this system at its Elverta Maintenance Facility, which held the record as the largest Powerlight system in the continental United States for several years. The Elverta site was also heavily instrumented to provide basic research and performance information. Shah managed all these projects.
• A 12-kW polycrystalline silicon system, using Solarex MSX-64 modules. This is similar to the single crystal silicon technology that originated in the semiconductor industry and is the most common form of PV. A total of 234 modules were attached to the building's standing seam metal roof with specially designed clamps. The PV array powers three Trace inverters to provide 240 V AC to a three-phase transformer, which boosts the power to 480 V for connection to the building's electrical system.
• A 12-kW amorphous silicon array, using Energy Photovoltaics EPV 40 modules. This is a thin-film technology that is the alternative to crystalline silicon. Thin film modules are currently less efficient than crystalline modules but are also less expensive. A total of 320 modules were attached to a standing seam metal roof to provide power to five Trace inverters, which feed 240-V power to the same transformer serving the Solarex modules.
• A 1-kW CIS beta test site for the Siemens S40 module. The subsequent 12-kW CIS project was an outgrowth of successful experience with this test site. The system is monitored by Western on behalf of Siemens Solar to ascertain field performance of this new technology.
• A 12-kW copper-indium-diselenide thin film array, using Siemens Solar S40 modules. (See story, p. 2). This system is currently the largest installed CIS system in the world.
• A 10-kW cadmium telluride thin film system, using BP Solar Apollo modules. (See story, p. 4). This is Western's third beta test site at Folsom and the largest BP Solar Cad Tel installation.

"Installing the systems has provided Western with a wealth of experience on practical problems and solutions involving commercial sized PV systems. Useful information on what worked and didn't work was shared with the PV module and inverter manufacturers and system integrators to help improve their products," Parkins explained.

About copper-indium-diselenide modules Western's experience with copper-indium-diselenide began in 1998 when Bob Parkins arranged with Siemens Solar of Camarillo, Calif., to place a beta test site at Folsom using the firm's advanced technology CID thin film modules. In summer 1999, a truck showed up with 32 donated modules, a total of 1 kW, which Parkins quickly assembled adjacent to Folsom's first beta test site. Every month he measures the module performance, collects weather information, and transmits the data to Siemens engineers. "I am very pleased with the modules," Parkins said. "They consistently perform very well, are durable, attractive, and easy to install. I was so impressed that I specified CIS for one of the phases in the Folsom PV Technology Demonstration Project. We bought 384 modules and connected them to a 15-kW Trace Technologies inverter that had just been introduced to the market for commercial applications. The Siemens CIS modules, when wired 24 in series, work well with the Trace inverter, and generate 12 kW of AC power at peak," he said. The CIS modules are not like conventional crystalline silicon PV modules. "Crystalline silicon is the Cadillac of the PV world for performance, but it also is the most expensive," Parkins explained. "The CIS is a thin-film technology, which can be manufactured much faster with less material. It is not as efficient as crystalline silicon, but it is getting closer. I believe high-efficiency thin film modules, like the Siemens CIS, will be produced in tremendous quantities in the future at low costs. That is what is needed to satisfy world demand. After all, over one billion people in the world don't have access to electricity."

Total system vs. module costs
"I believe it is a common mistake to put too much emphasis on the cost of PV modules," he said. "I am more interested in total system costs and the tradeoffs between what the user needs and what is appropriate.

"For example, I often recommend spending more money on a PV module that comes from the factory with wiring quick connects to simplify installation and, consequently, reduce the total cost of the completed system. I have also learned to design the modules and inverter around the building's electrical system. It is tempting to force fit a 'standard' residential PV system into a commercial facility, but it doesn't work well.

"This is where our technology demonstration project helps our customers. They can see and touch actual systems, discover the advantages and appropriateness of each technology, and learn about installation considerations and details that will help them make informed decisions."

"I am particularly proud of the advanced technology thin-film systems that we have-the copper-indium-diselenide and the cadmium telluride-and the beta test sites that we have to measure the field performance of the prototypes. Although they do not match the efficiency of a classical crystalline silicon cell that most people are familiar with, they have the potential to be manufactured in great quantities rapidly and inexpensively. From a cost-per-watt basis, I believe they will be the preferred technology in the future."

Parkins's experience planning, designing, and spending many hours on roofs installing systems has paid dividends for Western customers. He has helped several municipal customers plan and design their own projects, develop and evaluate technical specifications for request for proposals, search out available grants, and monitor and inspect the PV installations.

"I get tremendous satisfaction in sharing what I have learned. I have been fortunate to have great teachers like Greg Johanson of Solar Electrical Systems, Don Osborn and Dave Collier of Sacramento Municipal Utility District, and Dan Shugar of Powerlight. I truly believe that the future lies with renewable energy, like solar energy and PV, and I am willing to talk to anyone, anytime, anywhere about it. I know Krishna feels the same way," Parkins said.

The technical assistance that Parkins provides to Western customers is also available to all Federal agencies within the region covered by the Seattle office of the Federal Energy Management Program. This region covers Hawaii, Alaska, Washington, Oregon, California, Nevada, and Arizona. FEMP has an Interagency Agreement with Western for Parkins to provide initial consultations and training to Federal agencies to help them plan PV projects at their own facilities.

 

About cadmium telluride PV technology Success often builds upon success. With two beta test sites under his belt, Bob Parkins arranged with BP Solar to expand the Folsom PV Demonstration Project to include another advanced technology thin-film system-cadmium telluride. BP Solar generously donated 144 Apollo modules, for a total of 10 kW, while Western provided the balance of the system components for the third beta test site at Folsom. It is the first Apollo project installed outside of BP Solar and the largest installed to date. "This time we included an advanced automated data acquisition system with a full weather station with remote access capability-all the bells and whistles an engineer loves," he said. "The experience with BP Solar was terrific. They listened to my input and provided a system with quick connects to simplify wiring and a framing system that is light and easy to install. My back appreciated their innovations since I help install all of our systems to learn as much as I can. Simplicity and safety during installation are among the things I look for, and I was not disappointed with BP Solar's system." Cadmium telluride is another thin-film technology that has the potential of being produced in huge quantities at a low price. "I like the product. Besides being easy to install, it is attractive and its efficiency is better that the older amorphous silicon thin-film modules that are on the market, although its efficiency is not as high as crystalline silicon. I believe it is the wave of the future, together with CIS, the other advanced thin-film technology. There are more than enough uses for both," Parkins said.