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4. Costs and Benefits
4.1. Overview
Estimating costs for the VRB is complicated by the small number of field
demonstrations, the lack of manufacturing in significant quantities, and the wide range of
power ratings and energy ratings for the applications considered in this analysis. The
basis of cost estimates come from discussions with the manufacturers, a previous EPRI
study of advanced batteries [Symons, 1998], a survey of advanced storage technologies
by Sandia National Laboratories [Corey, 2002] for a proposed 2.5 MW / 10 MWh project
in Nevada, and experience with similar flow batteries and system integration efforts by
the author.
The VRB can be thought of as having two distinct capital cost elements: (1) those
associated with the power rating, including cell stacks and PCS, and (2) those associated
with the energy storage rating, such as tanks, plumbing, pumps, and enclosure. This is
not strictly true, since some items (such as the control system) are not related to either the
power or energy ratings, and some items may be related to both elements. Nonetheless, it
is useful to report capital costs in these terms, and one cost breakdown for the VRB is
provided below.
4.2. Costs
Capital Costs
Stack costs include materials costs, such as electrodes and separators, labor costs,
amortization of tooling and plant used in manufacturing, various overhead costs,
shipping, installation, and taxes. While the VRB is not at present manufactured in
automated or semi-automated processes, these have been estimated [Symons, 1998] at
about $450/kW for quantities of 1 MW per year and $300/kW at 20 MW per year.
Balance of system (BOS) costs as defined here represent all installed system costs except
for the stacks and PCS. These include the electrolyte, pumps, plumbing, electrolyte
tanks, supporting structures and enclosures, control systems, shipping, installation, and
taxes. The largest component of BOS cost, the electrolyte itself, is estimated [Symons,
1998] to be $30-50/kWh depending upon the quantities procured. However, this estimate
was based upon the $6-7/kg price of vanadium chemicals in 1998. Vanadium commodity
prices have since declined steadily each year 4 to about half that price in 2002.
Furthermore, the strategic relationship between Vantech and Highveld may provide
additional cost savings in VRB chemicals, and it is reasonable to expect that electrolyte
costs will range from about $40/kWh for initial systems down to about $20/kWh for
mature production quantities. Except for a handful of custom-built storage demonstration
projects based on different battery chemistries, there is little quantitative information
available about the remaining BOS cost components. Assuming these non-electrolyte
4 U.S. Geological Survey, Mineral Commodity Summaries, January 2002.
Vanadium Redox Battery 27