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

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For coils of this size or larger, the structural mass is proportional to the stored energy. Thus, the
cost for structure is directly proportional to the stored energy. On the other hand, since the
thickness of the windings is constant, the larger the coil, the smaller the cost of superconductor
per unit of stored energy.
Extensive History of SMES
The following are steps along the way to the development of SMES technology. They include
technical developments and studies prepared to show the effectiveness of SMES technology and
the costs and value of the system. These studies and devices are generally listed in chronological
order. The exception to this rule is where a review of several related studies contains relevant
summary information that makes the review of greater value than any of the individual pieces.
Many reports that related to these studies are contained in the Bibliography.
As is true of many technologies, early concepts that drive the approach of the research
community for a period may be found to have a very limited contribution to the eventual
development of commercial systems. Some specific instances are described here.
1969 Ferrier of Electricité de France proposed a large superconducting magnet that would
accommodate a great deal of the load levelling needs for France. His intent was to use a toroidal
coil that was several hundred meters in diameter with a peak field greater than 10 T. It was later
found that the various superconducting materials have optimum (least expensive) fields and
temperatures for their use. Most SMES devices in operation today operate at a peak field of 5 to
6 T.
1971 Boom, Peterson and Mohan of the University of Illinois conceived of a direct connection
of a large, DC energy storage coil to the electric power grid via a 3 phase SCR based
inverter/converter. This approach has been the core of the design of the power component of the
SMES system, though improvements in silicon based power conversion systems have advanced
the functionality of the PCS on modern SMES plants.
1972 Hassenzahl of the Los Alamos National Laboratory proposed the use of in situ rock to
support the magnetic forces in a large SMES for load levelling and the operation of the SMES
coil in superfluid helium. These two changes in a large system eliminate about half the total
plant cost. The cost of structure as a fraction of total cost depends on the amount of stored
energy, but is roughly 30% of the cost of a very large SMES. In 1972, the cost of the
superconductor was estimated to be about half of the total system cost, which was cut in half.
Both of these suggestions increased the cost of the refrigerator, which must remove heat that is
carried along the supports between the coil and the warm rock and must have a greater capacity
when operating at the lower temperature required by superfluid. It increased from 2% of the
total cost to about 4%. The overall impact of these two design conditions was a cost reduction of
about 40 %. Since very large SMES plants were never built, neither of these concepts has been
applied to the technology.
1973 Hassenzahl of Los Alamos suggests the addition of excess converter capacity to adapt a
load-levelling device to a system with multiple benefits, specifically spinning reserve.
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