Page 38 - Solar Power in Building Design The Engineer's Complete Design Resource

8 SOLAR POWER SYSTEM PHYSICS

Figure 1.4 Photovoltaic module operational diagrams.

positive and negative leads. These are then connected front to back in series to achieve
higher voltages.
For example, 48 solar cell modules connected in series will result in 24 V of output.
An increase in the number of solar cells within the solar cell bank will result in a high-
er voltage. This voltage is employed to operate inverters which convert the dc power
into a more suitable ac form of electricity.
In addition to the previously discussed PN-junction device, solar cells contain
construction components, for mechanical assembly purposes, that are laid over a rigid
or flexible holding platform or a substrate, such as a glass or a flexible film, and are
interconnected by micron-thin, highly conductive metals. A typical solar panel used in
photovoltaic power generation is constructed from a glass supportive plate that houses
solar PV modules, each formed from several hundreds of interconnected PN devices.
Depending on the requirements of a specific application, most solar panels manufac-
tured today produce an output of 6, 12, 24, or 48 V dc. The amount of power produced
by a solar panel, expressed in watts, represents an aggregate power output of all solar
PN devices. For example, a manufacturer will express various panel characteristics by
voltage, wattage, and surface area.

Types of Solar Cells Technologies

Solar cell technologies at present fall into three main categories: monocrystalline
(single-crystal construction), polycrystalline (semicrystalline), and amorphous silicon
thin film.