Environmental Engineering Reference
In-Depth Information
kWh
m
3
%
20
22
15
10
5
0
10 20 30 40 50 60 70 80
bar
p
s
2
/
p
s
1
= 2.0
20
18
p
s
2
16
E
Gen
V
s
12
10
p
s
2
/
p
s
1
= 2.5
8
p
s
2
/
p
s
1
= 2.0
6
p
s
2
/
p
s
1
= 1.5
p
s
2
/
p
s
1
= 1.4
p
s
2
/
p
s
1
= 1.3
p
s
2
/
p
s
1
= 1.2
4
2
0
10
20
30
40
50
60
70
80 bar
P
s2
Fig.
- Determining the size of the reservoir
E
Gen
= Generator energy
= Storage volume
= Upper storage pressure
= Lower storage pressure
= Reservoir, case 1
= Reservoir, case 2
= Reservoir, case 3
= 825 ˚K,
T
E
ND
= 1100 ˚K
V
s
P
s2
P
s1
T
E
HD
FIGURE 5.12
E
nergy produced per unit volume for CAES with constant pressure reservoir (case 1), variable
pressure reservoir (case 2)
,
and variable pressure reservoir with constant turbine inlet pressure
(case 3). Inset shows throttling losses associated with case 3 relative to variable inlet pressure
scenario (case 2). (From P. Zaugg, Air-storage power generating plants, Brown
Boveri Review
,
62:
338
,
1975.)
compensated systems will most likely not be options and a case 2 or case
3 design would be required.
Notably, although the throttling losses incurred in case 3 relative to the
variable turbine inlet pressure system (case 2) implies a required larger stor-
age volume, the penalty is not large (see Figure 5.12 inset). In particular, the
throttling losses are small with large initial pressures (p
s2
> 60 bar) and this
is consistent with operations at all existing and proposed CAES facilities.
Because this small penalty is offset by the benefits of higher turbine effi-
ciency and simplified system operation, it is often optimal to operate a CAES
in this mode (as is the case at both the Huntorf and McIntosh plants).
