Page 308 -

Appendix C
Comparison of Different Power-Generation Methods 273

Applications of Solar Energy Technology
Average insolation showing land area (small black dots) is required to
replace the total world energy supply with solar electricity. Insolation
for most people is from 150 to 300 W/m^2 or 3.5 to 7.0 kWh/m^2/day.
Solar energy technologies use solar radiation for practical ends.
Technologies that use secondary solar resources such as biomass, wind,
waves, and ocean thermal gradients can be included in a broader descrip-
tion of solar energy, but only primary resource applications are discussed
here. Because the performance of solar technologies varies widely
between regions, they should be deployed in a way that carefully consid-
ers these variations.
Solar technologies are broadly characterized as either passive or active
depending on the way they capture, convert, and distribute sunlight.
Active solar techniques use photovoltaic panels, pumps, and fans to con-
vert sunlight into useful outputs. Passive solar techniques include
selecting materials with favorable thermal properties, designing spaces
that naturally circulate air, and referencing the position of a building to
the Sun. Active solar technologies increase the supply of energy and are
ptg
considered supply-side technologies, whereas passive solar technologies
reduce the need for alternate resources and are generally considered
demand-side technologies.

Solar Electricity

Sunlight can be converted into electricity using photovoltaics (PV),
concentrating solar power (CSP), and various experimental technologies.
PV has mainly been used to power small and medium-sized applications,
from the calculator powered by a single solar cell to off-grid homes pow-
ered by a photovoltaic array. For large-scale generation, CSP plants like
SEGS have been the norm, but recently multimegawatt PV plants are
becoming common. Completed in 2007, the 14 MW power station in
Clark County, Nevada, and the 20 MW site in Beneixama, Spain, are
characteristic of the trend toward larger photovoltaic power stations in
the United States and Europe.

Photovoltaics
A solar cell, or (PV, is a device that converts light into direct current
using the photoelectric effect. The first solar cell was constructed by
Charles Fritts in the 1880s. Although the prototype selenium cells