Environmental Engineering Reference
In-Depth Information
into a packaged weather-tight module. Multiple modules can be further connected to form an ar-
ray of one or several thousand modules. The number of modules connected together in an array
depends on the amount of power output needed (USEIA 2011d).
Climate conditions (such as clouds or fog) have a significant effect on the amount of solar
energy received by a photovoltaic array and, in turn, on its performance. Most modern modules
are about 10 percent efficient in converting sunlight to electricity (USEIA 2011d). Recent research
by the SunPower Corporation raised this efficiency to above 22 percent in commercial applica-
tions (USDOE 2011a).
With photovoltaic cells, conversion from sunlight to electricity is direct, so bulky mechanical
generator systems are unnecessary. PV arrays of any size can be installed quickly on any flat or
tilted surface. Using the existing interconnected electric transmission and distribution grid system
eliminates the need for power storage devices (Oregon Department of Transportation 2008). Pho-
tovoltaic cells, like batteries, generate direct current (DC), which is generally used for small loads
(electronic equipment). When DC from photovoltaic cells is used for commercial applications
or sold to electric utilities for use in the electric grid, it must be converted to alternating current
(AC) using inverters, solid-state devices that convert DC power to AC.
Environmental Costs of Using Solar Energy
The solar technology “fuel cycle” is quite simple, involving acquisition of materials, manufac-
ture and installation of solar collectors and control equipment, operation of this equipment, and
disposal or recycling of waste materials from manufacturing processes and decommissioning, as
illustrated in
Figure 5.2.
Manufacturing involves producing industrial-scale semiconductors, and
aluminum and sheet metal fabrication of collectors, with installation of plumbing and electrical
components, appropriate to the specific technology utilized. Utility-scale solar energy environ-
mental costs include land disturbance and land use impacts, visual impacts, potential impacts on
water resources, hazardous materials disposal, and adverse effects on other resources, depending
on the solar technology employed.
Land Use Impacts
All commercial-scale solar energy facilities require relatively large areas for solar radiation col-
lection when used to generate electricity. These large arrays of solar collectors may interfere with
natural sunlight, rainfall, and drainage, causing a variety of effects on plants and animals. Solar
arrays may create avian perching opportunities that could affect both bird and prey populations.
Large solar thermal power plants may harm desert ecosystems if not properly managed. Birds
and insects can be killed if they fly into a concentrated beam of sunlight, such as that created by
a solar power tower (USDOE, USDOI, and ANL 2011).
Land disturbance may also adversely affect archeological resources, and solar facilities may
interfere with existing land uses, such as livestock grazing. There are concerns that the large spaces
required for solar energy production will result in loss of critical wildlife habitat (Leitner 2009;
Tsoutsos, Frantzeskaki, and Gekas 2005). There have been several estimates of the total land area
required to meet electricity demand from photovoltaic cells (Love et al. 2003; Turner, 1999). One
study asserts that “huge tracts of land would have to be covered with photovoltaic panels and
solar heating troughs” and “a direct-current (DC) transmission backbone would also have to be
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