Environmental Engineering Reference
In-Depth Information
To overcome the cost and performance penalty associated with dry cooling, some
developers are considering
hybrid systems
that employ dry cooling when tempera-
tures are below 38°C (100°F) and wet cooling for hotter periods. Hybrid systems can
consume 40 to 90% less water than a wet-cooled system while maintaining 97 to
99% of the performance (USDOE, 2009); however, hybrid systems currently have a
higher life-cycle cost than wet-cooled systems (Turchi et al., 2010).
In addition to consuming water for cooling, trough and tower CSP systems con-
sume a relatively small amount of water to produce steam for electricity generation.
In a typical Rankine cycle steam turbine, water in a closed loop is heated to produce
steam and spin a turbine, then cooled, re-condensed, and used again. A relatively
small amount of water—compared with the water consumed in an evaporative cool-
ing system—is drained to remove particulates and salts (the blowdown process) in
the boiler and cooling systems. The amount of blowdown water depends on the qual-
ity of the source water; more is required when using degraded water sources. Dish/
engine CSP plants with Stirling engines do not use a water-steam cycle; the move-
ment of a gas is used to produce electricity in these systems.
The distribution of solar water consumption will not be uniform across the United
States; it will be highest in the arid Southwest, where CSP development will be con-
centrated. Unless dry cooling is used, siting CSP in arid areas presents a potentially
insurmountable deployment challenge because of water constraints in these areas
(Carter and Campbell, 2009). The West accounted for half of all U.S. population
growth from 1990 to 2000, creating additional demand for water (Anderson and
Woosley, 2005). Water resources in arid regions may also decline with climate change,
and the Southwest has experienced the most rapid warming in the United States (U.S.
Global Change Research Program, 2009). Water consumption per unit of area for PV
and CSP is less intensive than for a number of other activities. Thus, although water
consumption is likely to be an issue of contention in the Southwest going forward, it is
possible that solar developers will be able to obtain water rights from existing water-
rights holders, sometimes resulting in less intensive water consumption.
h
azardoUs
w
aste
Like all other technologies, solar technologies require proper waste management and
recycling. PV is associated with a few particular waste management and recycling
issues, whereas CSP shares issues with other technologies that use common materi-
als such as concrete, glass, and steel. Waste management and recycling issues for
each technology are discussed below, with a focus on the issues surrounding PV. The
PV cell manufacturing process includes a number of hazardous materials, such as
DID YOU KNOW?
Unlike wind turbine-produced electricity, solar power is noise pollution free.
It has no moving parts and does not require any fuel other than sunlight to
produce power.
