Environmental Engineering Reference
In-Depth Information
Case1:ConstantCavernPressure
First, consider the case of a CAES system with constant cavern pressure such
as a hard rock cavern with hydraulic compensation (see Figure 5.12). The
mass flow of air is constant throughout the process and can be expressed as
a simple ratio:
m
t
p V M
RT t
m
=
A
=
S S W
(5.21)
A
S
Likewise, since the inlet pressures and temperatures are constant in time,
Equation (5.30) reduces to
k
−
1
2
E
V
α
+ −
p
p
t
k
∫
2
GEN
=
V
m
β
b
dt
1
(5.22)
A
0
S
S
2
Combining these expressions,
k
−
1
2
E
V
α
M
RT
+ −
p
p
k
2
GEN
=
W
p
β
1
b
(5.23)
S
S
S
2
Case2:VariableCavernPressureand
VariableTurbineInletPressure
In the case of a variable pressure CAES system, the pressure at the turbine
inlet is allowed to vary over the operating range of the storage volume (from
p
S2
to p
S1
). However, since the pressure ratio across the hp turbine (p
2
/p
1
)
remains constant, the pressure ratio across the lp turbine is proportional to
the cavern pressure p
S
[33]:
p
p
p
p
p
p
constant
b
1
b
=
=
(5.24)
ϕ
p
2
2
S
S
