Environmental Engineering Reference
In-Depth Information
cleanup of produced water. 4 These alternatives for attainment of head and
water should be considered and will likely be required to make some future
projects work.
Environmental Considerations
Any hydro-based development project will involve environmental consider-
ations. Preserving healthy aquatic environments is important. By bringing
multiple stakeholders into the development conversation early, challenges
may be avoided down the road.
Environmental considerations key to development include maximizing
head to reduce the water need; potentially utilizing alternative water sources
and cleaning those sources if needed; constructing PHES facilities off line to
avoid damming of running rivers. Environmental considerations must be
assessed on a case-by-case basis but should be seen as solvable challenges
that can provide environmental benefits if addressed by multiple stakehold-
ers early in the planning process.
System Components
Reservoirs
The reservoirs serving a PHES system are critical to its viability. The reservoirs
known as the forebay and afterbay are the storage tanks of the system. They
are critical from both technical design perspectives and may be “show stop-
pers” from social and environmental perspectives. The difficulties in siting
reservoirs warrant utilizing current reservoirs where available as opposed
to developing new ones. Finding suitable reservoirs already in place may be
possible but new reservoirs will likely be required for future development.
The higher the available head, the smaller the reservoirs must be based on
the tradeoff between head and flow for power and energy availability.
Upper Reservoirs
New forebay development can be accomplished by various ways including
a stream valley reservoir (Figure 3.4) or a hill top reservoir. A stream valley
reservoir is created by an impoundment constructed across a stream valley
such that it fills the valley behind the impoundment. A derivation on stream
valley construction common to PHES development is a high stream valley
reservoir that follows the same basic idea of valley impoundment but applies
it to a steeper slope. An example of a high stream valley forebay is Cabin
Creek located just outside Georgetown, Colorado, owned and operated by
Xcel Energy/Public Service Company of Colorado (Figure 3.5).
A hilltop reservoir is constructed by building an embankment around
a  hilltop and storing water inside the embanked hilltop. An example of a
hilltop reservoir is the forebay of Raccoon Mountain (Figure 3.6).
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