Renewable Energy Technology Assessments - Kauai Island Utility ...

Kaua’i Island Utility Cooperative
Renewable Energy Technology Assessments
3.0 Renewable Energy Technology
Options
3.7.1 Solar Photovoltaic
Photovoltaics (PV) have achieved considerable consumer acceptance over the last
few years. PV module production tripled between 1999 and 2002, reaching a worldwide
output of 562 MW in 2002. Worldwide grid-connected residential and commercial
installations grew from 120 MW/yr in 2000 to nearly 270 MW/yr in 2002. The majority
of these installations were in Japan and Germany, where strong subsidy programs have
made the economics of PV very attractive. Large scale (>100 kW) PV installations have
been added at a rate of about 5 MW per year over the last 2 years. 39
PV cells convert sunlight directly into electricity by the interaction of photons and
electrons within the semiconductor material. To create a PV cell, a material such as
silicon is doped (i.e., mixed) with atoms from an element with one more or one less
electron than occurs in its matching substrate (e.g., silicon). By alternate doping, thin
layers of “p” material and of “n” material are created to form a “pn” junction. Photons
striking the cell cause electrons to be set free in the junction, creating a current as it
moves across the junction. The current is gathered through a metallic grid. Various
currents and voltages can be supplied through series and parallel cell arrays.
Figure 3-13. Photovoltaic Solar Panel Installation.
The direct current produced depends on the material involved and the intensity of
the solar radiation incident on the cell. Single crystal silicon cells are most widely used
today. Single crystalline cells are manufactured by growing single crystal ingots, which
are sliced into thin cell-size material. The cost of the crystalline material is a significant
21 March 2005 3-58 Black & Veatch