Environmental Engineering Reference
In-Depth Information
The lower reservoir is the heart of the UPHES system. It can be excavated
from suitable geologic rock at various depths or it can tap an existing aquifer
or other naturally occurring underground water containment. UPHES allevi-
ates several of the challenges encountered with surface-pumped hydroelectric
installations. Dependence on surface topology is eliminated, although suitable
underground geology and structures are required. An underground system
has a vertical water flow path that greatly reduces loss associated with trans-
verse water flow. The environmental impact of an underground installation is
smaller than those of conventional pumped hydro systems because only one
surface reservoir is required. UPHES systems eliminate new river dams and
large powerhouses on the surface, minimize wildlife habitat disruption, and
reduce noise. Figure 4.1 illustrates a basic large, excavated UPHES system.
System Sizing
UPHES systems are roughly classified as small (10 kW to 0.5 MW) and large
(0.5 to 3000 MW) installations. Large systems are usually targeted at mitigat-
ing the varying loads of major urban centers or providing buffers to make
variable renewable energy more consistent. Most studies performed for large
Utility
Substation
Surface
Reservoir
Main Penstock
Cable Tunnel
Vent Duct
Underground
Reservoir
Power Station
FIGURE 4.1
Large basic UPHES system.
