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

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Costs and Benefits
This section defines the variables that determine typical costs and benefits for flywheel
energy storage applied to transmission and distribution. Costs are based on currently
available high speed and low speed flywheel technology, in multi module configurations.
For this analysis the low-speed system is estimated to be used for grid stability in the
proposed distributed mini FACTS application. The high-speed system is estimated for
service to provide fluctuating load stabilization in the railroad traction application. In
fact, either the high or low speed flywheels can be applied in these T&D applications.
Cost data is also provided for expected near-term development of the high-speed
flywheel. This development will increase the flywheel capacity by 2.5 times in the same
physical package.
Cost Assumptions
The following are the assumptions related to these variables and the relevant applications.
1. For the grid stabilization application the low-speed flywheel equipment first cost are
assumed to be $400 per kW. For the traction application the high-speed flywheel
equipment first cost is assumed to be $600 per kW for current hardware and $400 per
kW for future high-capacity hardware.
2. The installation cost is a one-time expense that includes ancillary electrical power
integration and wiring, panel board and switchgear, and system foundation and
enclosure equipment. HVAC is required for the low speed flywheel and this cost is
included as additional part of the installation cost.
3. The system footprint or real-estate cost is a fixed cost based on the square-footage
required to house the flywheel modules and related equipment. For this cost and
benefit analysis, it is assumed that the area required is 500 square feet for all three
applications and the cost per square foot per year is $25.00.
4. Annual operating expenses include cost of energy, routine maintenance, inspection,
and any scheduled replacements. The HVAC energy cost is a continuous expense and
is a function of the system efficiency. Only the grid stabilization application is
expected to require HVAC for system controls.
5. The energy used by the flywheel system to maintain rotor speed is a function of the
system efficiency and duty cycle. For example, for some applications, the duty cycle
might be once per week, while for more demanding applications, the duty cycle might
be once per hour. The efficiency is greatest for light duty cycle applications and
typically reaches 97 percent, or 3% loss at no load. However, for high-duty cycle
applications, the efficiency typically reduces to 90 percent.
Cost Analysis
Costs depend primarily on the flywheel technology and the specification for the
application. The primary applications discussed previously are AC grid stabilization and
traction load stabilization. The information in Table 4 below summarizes the significant
cost elements for these different applications and selected flywheel technologies.
Flywheels Page 33