Environmental Engineering Reference
In-Depth Information
comes online coincident with low demand, the challenge is to ramp down
the baseload thermal generation systems by some method of curtailment—
and ramping down is not always possible. Storage, specifically PHES, can
address the difficulty in managing ramping rates and anti-correlation of
variable generation and loads.
PHES takes energy from the grid and returns it at a later time when it is
needed. This raises an important question. What resource powers the PHES?
The resource that powers a PHES facility will be the at the margin when the
PHES facility pumps. Thus, when coal is on the margin, coal will power the
PHES facility and wind will furnish the power when wind is on the mar-
gin. The greater the amount of renewable energy on the system, the greater
the possibility for having a renewable energy resource on the margin as the
prime mover for the PHES facility. The larger the percentage of renewable
energy resource on the system, the more flexibility it will require.
At lower penetrations of renewable resources, less storage is needed and
the probability is greater that the storage will be powered by nonrenewable
energy resources. At higher penetrations of renewable resources, more stor-
age will be required and the probability is greater that the storage will be
powered by renewable resources. Thus, storage will become critical to fur-
ther development of renewable energy and will reflect the emissions reduc-
tions as the system lowers its overall emissions.
Example:DominionPower'sBathCountyPHESStation
Dominion Power has released a video covering many aspects of its Bath
County pumped storage facility. For a basic discussion of pumped storage
stations, the video may be accessed online.
1
A brief listing of facts about the
Bath County facility is as follows:
Net generating capacity
2,100 MW
License issued
January 1977
Start of commercial
operation
December 1985
Cost (1985)
$1.7 billion or $810/MW
Owners
Dominion Power (60%), Allegheny Power (40%)
Lower dam
135 feet (41 meters) high; 2,400 feet (732 meters) long; contains 4
million cubic yards (3.1 million cubic meters) earth and rock fill
Lower reservoir
555 surface acres (2.25 square kilometers); water level fluctuates 60
feet (18 meters) during operation
Upper dam
460 feet (140 meters) high; 2,200 feet (671 meters) long; contains 18
million cubic yards (13.8 million cubic meters) of earth and rock fill
Upper reservoir
265 surface acres (1.07 square kilometers); water level fluctuates 105
feet (32 meters) during operation
