Page 75 - Alternative Energy Systems in Building Design

CRYSTALLINE, AMORPHOUS, THIN-FILM, AND SUN-TRACKER TECHNOLOGIES 51

An integrated isolation transformer within the inverter provides complete noise isola-
tion and filtering of the ac output power. A night isolation ac contactor disconnects the
inverter at night or during heavy cloud conditions. The output of the inverter also includes
an ac surge isolator and a manual circuit breaker that can disconnect the equipment from
the grid.
A microprocessor-based control system within the inverter includes, in addition to
waveform envelope construction and filtering algorithms, a number of program sub-
sets that perform anti-islanding, voltage, and frequency control.
As an optional feature, the inverter also can provide data communication by means
of an RS 485 interface. This RS 485 interface can transmit equipment operational and
PV measurement parameters such as PV output power, voltage, current, and totalized
kilowatthour metering data for remote monitoring and display.

Crystalline, Amorphous, Thin-Film,

and Sun-Tracker Technologies

This section is intended to familiarize readers with the four fundamental classes of solar
power PV systems, namely, monosilicon wafer, amorphous silicon, thin-film, and con-
centrator-type technologies. The basic physical and functional properties, manufacturing
processes, and specific performance parameters of these technologies will be reviewed.
In addition, some unique case studies will provide a more profound understanding of the
applications of these technologies.
Each of the technologies covered here has been developed and designed for a spe-
cific use and has unique applicative advantages and performance profiles. It should be
noted that all the technologies presented here can be applied in a mixed-use fashion,
each meeting special design criteria.

CRYSTALLINE PV SOLAR MODULE PRODUCTION
This section will review the production and manufacturing process cycle of a crys-
talline-type PV solar module. The product manufacturing process presented is specific
to SolarWorld Industries. However, it is representative of the general manufacturing
cycle for the monosilicon class of commercial solar power modules presently offered
by a large majority of manufacturers.
The manufacture of monocrystalline PV cells starts with silicon crystals, which are
found abundantly in nature in the form of flint stone. The word silicon is derived from
the Latin silex, meaning “flint stone,” which is an amorphous substance found in nature
and consisting of one part silicon and two parts oxygen (SiO ). Silicon (Si) was first
2
produced in 1823 by Berzelius when he separated the naturally occurring ferrous
silica (SiF ) by heat exposure with potassium metal. Commercial production of silicon
4
commenced in 1902 and resulted in an iron-silicon alloy with an approximate weight
of 25 percent iron that was used in steel production as an effective deoxidant. At present,
more than 1 million tons of metallurgical-grade 99 percent pure silicon is used by the