Environmental Engineering Reference
In-Depth Information
TABLE 5.2
Selected CAES Efficiency Expressions and Values Cited in Literature
ReportedValues
WithoutHeat
Recuperator
WithHeat
Recuperator
Parameter
Definition
Heat rate
6000 to 5500 kJ/kWh
(~60 to 65%)
4500-4200 kJ/kWh
(~80-85%)
E
E
T
F
η
F
=
Charging energy ratio
1.2 to 1.4
1.4-1.6
E
E
T
M
η
PE
=
Primary energy
eficiency
CAES charged from nuclear power
(η
T
= 33%) [33]
24.5% 29.7%
Charged from fossil fuel power plant
(η
T
= 42%) [33]
28.2% 34.4%
Charged from combined heat and power
plant (η
T
= 35%) [65]
- 35.1 to 41.8%
Charged from grid-averaged baseload
power (η
T
= 35%; CER = 1.4) [70]
42-47%
E
T
η
=
PE
E
/
η
+
E
M
T
F
Roundtrip Efficiency (1)
E
4220 kJ LHV/kWh, CER = 1.5,
η
NG
= 47.6%, [10]
η
,1
=
T
RT
E
+
η
E
M
NG
F
81.7
Roundtrip Efficiency (2)
4220 kJ LHV/kWh, Eo/Ei = 1.5,
η
NG
= 38.2%, [74]
E
−
E
E
η
η
,2
=
T
F NG
M
RT
82.3%
Second Law Efficiency
T
O
= 15 C, T
MAX
= 900 C, p
S
= 20 bar [67]
E
T
T REV
η
Il
=
E
,
58.7%
68.3%
fuel consumption, these systems also offer significant NO
x
emission benefits
relative to prior designs [66].
Charging Electricity Ratio
The second performance index for CAES is the ratio of generator output to
compressor motor input—the charging electricity ratio (CER). Because of the
fuel input, the CER exceeds unity and will typically lie in the range of 1.2 to
1.8 (kWh
output
/kWh
input
) [1,33,67]. The CER also takes into account piping and
throttling losses and compressor and expander efficiencies. Throttling loss
is a function of the reservoir pressure range. Turbine efficiency is especially
