Page 78 - Alternative Energy Systems in Building Design

54 SOLAR POWER SYSTEM PHYSICS AND TECHNOLOGIES

Figure 3.17 A formed silicon ingot cylinder ready for inspection.

100 percent functionality and is made ready for module assembly. Figure 3.18 shows
silicon ingot cylinders in a production chamber.

PV module production The PV module production process involves robotics and
automatic controls in which a series of robots assembles the solar cells step-by-step,
laying the modules, soldering the cells in a predetermined pattern, and then laminating
and framing the assembly as a finished product. On completion of framing, each PV
module is tested under artificial insolation conditions, and the results are permanently
logged and serialized. The last step of production involves a secondary module test,
cleaning, packaging, and crating. In general, the efficiency of the PV modules pro-
duced by this technique ranges from 15 to 18 percent.
PV module life span and recycling To extend the life span of PV solar modules,
PV cell assemblies are laminated between two layers of protective covering. In gen-
eral, the top protective cover is constructed from 1/4- to 5/8-in tempered glass, and the
lower protective cover is constructed from either tempered glass or a hard plastic
material. A polyurethane membrane is used as a gluing membrane that holds the sand-
wiched PV assembly together. In addition to acting as the adhesive agent, the mem-
brane hermetically seals the upper and lower covers, preventing water penetration or
oxidation. As a result of hermetic sealing, silicon-based PV modules are able to with-
stand exposure to harsh atmospheric and climatic conditions.
Even though the life span of silicon-based PV modules is guaranteed for a period
of at least 20 years, in practice, it is expected that the natural life span of the modules
will exceed 45 years without significant degradation.