                                       

                                  MEMORANDUM

Tetra Tech, Inc.
10306 Eaton Place, Suite 340
Fairfax, VA 22030
phone	703-385-6000

TO:			Paul Shriner, USEPA
FROM:		Kelly Meadows
DATE: 		March 11, 2011

SUBJECT:		Power Plants Located in Water-Limited Environments

Water-limited environments like the desert areas outside of Las Vegas can be challenging locations for construction of industrial facilities such as power plants, as these sites often require significant water resources.  However, given the increasing demand for electricity in Las Vegas, power producers have recently constructed a number of new generating facilities in the vicinity.  This memo documents the research into the construction of these facilities and the decision criteria used in selecting the facility's design, particularly with respect to the cooling system.

Cooling Water System Design

Power plants generate a significant amount of waste heat that must be rejected and cooling systems often use once-through cooling.  However, as discussed above, water-limited areas are challenging locations to construct new power plants; surface water is usually not available (particularly in large enough quantities for a once-through system) and competition for groundwater resources may be high (e.g., demand for drinking water supplies).

As a result, utility companies may opt to construct new facilities with dry cooling, a form of closed-cycle cooling that consumes very little water and rejects heat to the atmosphere through radiative cooling (instead of evaporative cooling, as in a wet cooling tower).

Dry cooling does have drawbacks, including an energy penalty to operate the fans and radiators.  However, these drawbacks are greatly reduced when dry cooling is incorporated into the design of the power plant (as opposed to a retrofit application); for example, turbine systems can be designed to optimize the increased backpressure, therefore reducing the loss of generating efficiency typically seen in closed-cycle systems.

New Power Plants

According to some estimates, Las Vegas has a power demand of approximately 4.8 gigawatts.  Given the growth in the area, generating capacity has been added to meet the demand.  Some alternative energy (primarily solar and wind) capacity has been added but new power plants were still necessary.  Through internet research and information from the Department of Energy's Energy Information Administration (EIA)], Tetra Tech was able to identify several power plants that are located in the Las Vegas area, with many being constructed in recent years.  Table 1 below lists these facilities.

Table 1. New Power Plants in the Las Vegas Vicinity
Facility Name
Owner
Generating Capacity (MW)
Fuel Type
Operational Year
Cooling System Type[1]
Water Source
Chuck Lenzie
Nevada Power
1465
Natural gas combined cycle
2006
Dry cooling
Well
Clark
Nevada Power
1377
Natural gas combined cycle and combustion turbines
1955
Mechanical draft
Municipal
Walter Higgins
Nevada Power
688
Natural gas combined cycle
2004
Dry cooling
Grey water
Silverhawk
Pinnacle West
664
Natural gas combined cycle
2004
Dry cooling
Well
Reid Gardner
Nevada Power
636
Coal
1965
Mechanical draft
Well, river
Apex
Las Vegas Power Company
600
Natural gas combined cycle
2003
Dry cooling
Well
Las Vegas Cogeneration
SWG Nevada
297
Natural gas combined cycle
2003
Mechanical draft
Municipal
Harry Allen
Nevada Power
186
Natural gas combined cycle and combustion turbines
1995
Dry cooling
Municipal and well
Saguaro
NRG Energy and Paragon Assets
127
Natural gas combined cycle
1991
Dry cooling
Grey water
Source: Energy Justice Network mapping tool. http://www.energyjustice.net/map/ 
1 Information confirming the cooling system type was difficult to locate; this assessment is based on aerial photos, available online information, and conversations with Nevada staff.  Several facilities also appear to use cooling ponds.

Little information on the permitting process was readily available, but all indications are that many of the new plants were constructed in areas with very little water, making dry cooling the only available option.

Additionally, many of these facilities would not be subject to national requirements under the proposed rule, as they do not meet the scoping criteria; withdrawals are not from surface waters and several facilities do not have NPDES permits.
