Environmental Engineering Reference
In-Depth Information
TABLE 3.1
U.S. Solar-Related Water Consumption for Solar Technology
Deployment in 2030 and 2050 under USDOE (2012) Scenario
Solar
Generation
in 2030
(TWh)
Solar-Related Water
Consumption
in 2030
(billion gal)
Solar
Generation
in 2050
(TWh)
Solar-Related Water
Consumption
in 2050
(billion gal)
Rooftop PV
164
0-0.8
318
0-1.6
Utility-scale PV
341
0-1.7
718
0-3.6
CSP
a
137
14-75
412
42-227
Total
642
14-78
1448
42-232
Source:
USDOE,
SunShot Vision Study
, U.S. Department of Energy, Washington, DC, 2012.
a
The CSP water-use values shown here reflect a range of trough/tower water-use estimates. The
low number reflects trough/tower technology with 90% use of dry cooling and 10% use of wet
cooling, with per-megawatt-hour consumption at the low end of the trough/tower ranges. The
high number reflects trough/tower technology with 50% use of wet cooling and 50% use of dry
cooling, with per-megawatt-hour consumption at the high end of the trough/tower ranges. The
USDOE scenario assumes 100% dry cooling as a conservative estimate of costs, but it is likely
that the mix would consist of various technologies. Thus, the values given in this table are meant
to illustrate a range of possible scenarios of CSP deployment. Dish/engine CSP technologies
were used in these calculations because substantially more data are available for them, but,
assuming dish/engine technologies meet the price and performance characteristics envisioned in
the USDOE scenario, widespread deployment of these technologies could help reduce CSP-
related water use.
2.
Drift
—A small quantity of water may be carried from the tower as mist or
small droplets. Drift loss is small compared to evaporation, and blowdown
and is controlled with baffles and drift eliminators.
3.
Blowdown or bleed-off
—When water evaporates from the tower, dis-
solved solids (such as calcium, magnesium, chloride, and silica) are left
behind. As more water evaporates, the concentration of these dissolved
solids increases. If the concentration gets too high, the solids can cause
scale to form within the system or the dissolved solids can lead to cor-
rosion problems. The concentration of dissolved solids is controlled by
blowdown. Carefully monitoring and controlling the quantity of blow-
down provides the most significant opportunity to conserve water in cool-
ing tower operations.
4.
Basin leaks or overlows
—Properly operated towers should not have leaks
or overflows. Float control equipment must be checked to ensure that the
basin level is being maintained properly, and the system valves must be
checked to make sure that there are no unaccounted for losses.
