Handbook of Energy Storage for Transmission or ... - W2agz.com

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Operating Cost
As a rule of thumb for a “generic” CAES plant, the operating cost per kWh delivered during
power generation mode is 0.75 times that of the incremental cost per kWh of off-peak power
purchased during the compression mode, plus the cost of the fuel (in $/MMBTU) times 4,000
Btu/kWh generated [2].
Cost of electricity generated ($/kWh) = (0.75) (Incremental cost of electricity purchased, $/kWh)
+ (Cost of fuel purchased, $/MMBtu) (4,000 Btu/kWh) / (1,000,000 Btu/MMBtu)
The factor “0.75” includes the ratio of generated electricity to purchased electricity and the
energy lost to pipe friction, air leakage, pressure regulation, and compressor/expander
component efficiencies. The heat rate of 4,000 Btu/kWh is typical for an expander-generator set
operating without the compressor during the generation mode.
Cost information
Table 10 shows the typical size, capacity, response time, and capital cost per kW e for
hypothetical CAES plants designed for the six T&D applications described in Section 3 (and
Tables 7 and 8). The fixed O&M costs for CAES plants are projected to be in the range of
$4/kW e to $7/kW e , and the variable O&M costs in the range of $0.001/kWh to $0.002/kWh. In
these examples, the fixed and variable O&M costs, the electricity in Vs. out, and the heat rate
were chosen to be the same for every plant:
• Fixed O&M costs $6.00/kW e per year [17]
• Variable O&M costs $0.002/kWh [17]
• Electric Input/Output 0.75 [2]
• Heat Rate (HHV Btu/kWh) 4,000 [2]
Benefits information
In this sample benefits analysis, the hypothetical CAES plants designed for the six T&D
applications described in Section 3 (and Tables 7, 8, and 10) are analyzed in five situations. It is
assumed that a utility is comparing the cost the CAES situations with the alternatives. In each
situation, the economic benefit of the CAES plant is compared to the situations listed in
Table 11.
For each plant, Table 12 shows the assumptions and Table 13 shows the quantifiable benefits of
the CAES plants delineated for each application. The quantifiable benefits are presented as net
present values for the five situations. The benefits will, of course, depend upon local and site
specific conditions associated with each plant type applied to each case. In addition, there are
unquantifiable benefits of each application of CAES (e.g., customer satisfaction on power
quality, reduced wear and tear from operating equipment near or over limits). Note that for all
Compressed Air Energy Storage (CAES) Page 28