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Utility-Scale Applications

In 1995-1996 utility companies allocated over $100 million($US) forPV purchases
at over 400 installation sites.

PV technology / performance has been much improved in recent years, withavailability and reliability approaching utility standards. Current utilityconcerns include :
· Availability, ease of purchase and tech support for large PV powermodules(>50 Wp).
· Some amount of PV module degradation that has been seen for mostall of the PV flat-plate technologies which have been field tested since1985.
· Module / panel rating. The rating of modules has evolved to includeseveral testing methods and more than one standard is now being used.
· Varying PV manufacturing technologies each have different chancesfor near term cost reductions / efficiency improvements.

PV Manufacturing Technologies vs Market Development :
Utility purchasing trends over the next few years will continue play a keyrole in projecting which PV technologies will be ultimately most successful.
Performance of commercial crystalline modules has been generally satisfactoryto utility users, with slow, continual price declines as well as slow, continualefficiency gains.
Long term prospects for thin film photovoltaic technologies continue tointerest the utility market. DOE development support for thin film materialsand production processes has been helpful.

For the purposes of market trend analysis, PV utility market segments aredivided into "internal, infrastructural acquisitions" and "demand-sidemanagement. Worldwide, utility companies have been purchasing PV for theirown internal, infrastructural upgrades since 1982. These types of acquisitionsare mostly in the category of mobile communications, telemetry and arealighting. Demand-side management is a newer category for PV applications,including distributed line-tied substations and both line-tied and standalone roof-mounted systems.

Balance-of-system(BOS) is the photovoltaic system category for all equipmentand installation operations other than the actual PV modules. Several largePV manufacturers also manufacture some balance of systems equipment. HistoricallyBOS has been the domain of large engineering and systems houses. Severallarge
international companies have specialized in custom applications for veryspecialized utility scale equipment. For example, Peerless Winsmith, forover 20 years, has concentrated on large sun-tracking mounting structuresfor utility scale PV arrays and other solar electric and/or solar thermalapplications

Typically, BOS for utility applications includes the following:
· DC-to-AC inverter (power conditioning unit)
· foundation, plus mounting structure for PV modules which may "track"the sun or be "fixed" facing south);
· all electrical cable & connection equipment.
· Storage components. Storage, if utilized usually means
(BOS, continued)
batteries, but may include pumped storage or other options.
· If utilized, any backup generation equipment such as on-site dieselgenerator set(s).

·"Soft" costs included in BOS cost accounting generally include:
· Project Management · Engineering and Design
· Procurement · Siting and Permitting
· Installation · Construction Management
· Electrical Protection · Safety Equipment

1995­p;1997 : Constraints On Utility Participation
· Component miss-matching
· Need for more system integration
· Need for more standardized PV/ BOS packages
· Regulatory, codes and standards issues, worldwide
· Need for more trained design/engineering staff, worldwide
· Management-level misperceptions/lack of 1st hand experiences
· Need for product development: performance/degradation issues
· Early stage of international high volume mfg capacity
· Need for further development building integration
· Need for additional tax structure incentives

ARCO Solar's Lugo-Hesperia Substation was the world's first photovoltaiccentral power station. ARCO Solar's 6.5 megawatt Carrisa Plains plant wasthe largest grid-connected PV station in 1985. The early lessons learnedfrom their performance were significant to the utility industry, worldwide.

Carrisa Plains 6 5 MW central station power was originally connected tothe PG&E grid, providing over 12 million
kilowatt-hours annually, sufficient to meet annual electrical needs forover 2,300 average homes. Annual comparisons of performance predictionsto actual energy output for Hesperia and Carissa indicated that :
· these plants were productive and reliable
· PV power plant performance is highly predictable
The predicted AC output of the Carrisa plant for the period studied was12,207 megawatt-hours. The actual performance was 12,232 megawatt-hours.The plant's capacity factor (during system peak periods) was generally above60%, with unattended operation, low maintenance expense, no water requirementsand no air emissions. The Carrisa Plains Solar Substation was sold off toCarrizo Power in 1990.
Currently, the accuracy with which the performance of large central stationPV can be modeled is due to the straightforward nature of central solarPV plant technology and the sophisticated analytic performance models nowavailable.

International PV / BOS manufacturers continue to benefit from an increasingnumber of utilities that are investigating feasibility photovoltaic distributed-powergeneration / grid support, strategically located to relieve transformerstress and match load growth in the distribution network.

Current example: Sacramento Municipal Utility District (SMUD) recently workedhard to complete a significant solar home electrification project in 1994.The pilot project, involving 108 homes in the Sacramento area (SMUD's PVPioneers program) showcases the viability of using photovoltaic power aspart of the utility's distributed power system. SMUD's program grid-connectedsolar arrays are composed of seven pre-wired 400 kWp rooftop mounted arraysand an inverter to convert the direct current (DC) generated by the solararray into an alternating current (AC). The AC power is fed back into thelocal grid. Each of the rooftop PV systems generates enough electricityduring the year to meet the average electrical needs of a Sacramento home.

John F. Long Homes' "Solar l" was the country's first centralsolar electric suburban community. (Photocomm 1986) The development is stillpowered predominantly by solar electric arrays The system designed to meetthe entire annualized power needs for 24 (very well-insulated) homes. ThePV system was originally designed and guaranteed (by ARCO Solar) to provide350,000 kilowatt hours of electricity each year for ten years.

The power conditioning unit is a 150 KW utility interactive inverter (Toshiba)that converts DC power to AC power and steps the voltage up to 12.5 KV.It is also specially designed to eliminate transformer no-load losses atnight. The solar electric network is then connected to the Salt River