Environmental Engineering Reference
In-Depth Information
1.20E+09
0.16
QL
0.14
1.00E+09
QL/QS %
0.12
8.00E+08
0.1
6.00E+08
0.08
0.06
4.00E+08
0.04
2.00E+08
0.02
0.00E+00
0
0
10
20
30
40
50
60
Time (hours)
FIGURE 7.8
Heat loss from spherical tank compared to the energy stored in the tank.
TABLE 7.9
Thermal Losses for Major Components of
Solar Two TES
Calculated
Thermal
Loss(kW)
Measured
Thermal
Loss(kW)
Major
Equipment
Hot tank
98
102
Cold tank
45
44
Steam generator
sump
14
29
Receiver sump
13
9.5
Source:
National Renewable Energy Laboratory.
2000.
Survey of Thermal Storage for
Parabolic Trough Power Plants.
NREL/
SR-550-27925. Washington, D.C.
EconomicsofThermalEnergyStorageSystems
Thermal storage is now the least expensive clean energy storage option avail-
able. However, the cost can only be reduced further through deployment and
economies of scale. TES is economical when one or more of the following
conditions exists:
• A utility experiences high demand.
• A utility provider charges time-of-use rates (some charge more for
energy use during peak periods of day and less off-peak).
• Daily loads vary greatly.
• Loads are of short duration or are infrequent or cyclical.
• Cooling equipment has trouble handling peak loads.
• Rebates are available for load shifting to avoid peak demand.
