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

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Prototype VRB system costs will be significantly higher than those discussed above since
they include one-time engineering costs, they would be based upon relatively
conservative design parameters, and they would use components without the cost-savings
advantage of mass production or quantity purchases from sub-suppliers. The VRB cost
estimate of $11 million for the 2.5 MW / 10 MWh Boulder City project is taken as a
representative prototype project cost. Based upon the considerations above, the PCS cost
(reduced from a 1 MW base cost of $300/kW) would represent about $250/kW, or
$625,000. Using a baseline BOS cost for an 8-hour prototype system of $300/kWh, the
BOS for the 4-hour prototype would be about $550/kWh, or $5.5M. The remaining
$4.9M would be to procure prototype non-mass produced stacks at about $1,960/kW.
Sample system costs for representative sizes and applications are shown in Table 5,
including Prototypes, “First of a Kind” (FOAK) commercial systems and “Nth of a Kind”
(NOAK) mature systems. Prototype, FOAK and NOAK stack costs are assumed to be
$1960/kW, $450/kW and $300/kW, respectively. Baseline PCS costs (representing a 1
MW PCS rating) are assumed to be $300/kW (Prototype), $250/kW (FOAK) and
$250/kW (NOAK), and these are adjusted using the Bechtel relationship described above.
Baseline 8-hour BOS costs are assumed to be $300/kW (Prototype), $140/kWh (FOAK)
and $100/kW (NOAK), and these are adjusted to account for discharge times. Note that
some scenarios have discharge times of less than 8 hours, and calculated costs reflect the
lower BOS costs. However, the costs of these systems are higher on a $/kWh basis since
the energy storage capacity is smaller.
O&M Costs
VRB maintenance costs are likewise subject to uncertainty due to limited field
experience. Maintenance would be limited to periodic inspections and minor repairs as
necessary. All systems are operated unattended. For purposes of this analysis, annual
fixed maintenance cost is assumed to be the same on a per-system basis for the T&D size
ranges considered here. Technician travel time and per-diem costs would be the major
component of inspection cost, and the additional inspection time required for larger
systems are assumed to be negligible. Inspection costs for one technician would be about
$1000 per day, required 12 times per year for prototype systems, 4 times per year for
initial commercial systems (FOAK) and 2 times per year for mature systems (NOAK).
Charging energy is assumed to be at off-peak wholesale pricing of $0.020/kWh and, with
an AC/AC roundtrip efficiency of 70%, variable O&M costs are therefore $0.029/kWh.
Fixed and variable O&M costs using the above assumptions are shown in Table 5.
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