Supercapacitor Energy Storage for Magnetic Resonance Imaging Systems

Abstract

Magnetic resonance imaging (MRI) involves very short pulses of very high current. Substantial savings in the high cost of MRI installations may be realized by employing suitable electrical energy storage, for which supercapacitors are strong candidates in view of high specific power and long cycle life. A key question is whether the well-known capacitance degradation with increased frequency is compatible with the complex and highly variable duty cycles of various MRI sequences. Compatibility of the supercapacitor voltage range with the MRI system must also be considered. We present a detailed analysis of power duty profiles in MRI, using actual imaging sequences, that has not been reported previously. We also propose and validate a simplified supercapacitor model that can accurately simulate its performance in the MRI system, involving pulses that are several orders of magnitude shorter than those considered previously. Results of equivalent experiments involving lithium-ion iron phosphate (LiFePO 4 ) batteries are also reported. Finally, we present a detailed analysis of the overall energy storage performance in a realistic neurological examination. The study is based on a specific system of our own design, and we fully disclose its relevant parameters, so that the results would be of direct practical value to the wider community, including developers of MRI.

Modelling of current and temperature effects on supercapacitors ageing. Part II: State-of-Health assessment

“…They obtained parameters are reported in Table 2. 4 The blue curve of Fig. 2 illustrates the measured evolution of the C SC during a PC stress performed for 30 days at 328.15 K. The red curve shows the estimated C Ã SC using Eq.…”

“…Refs. [1][2][3][4][5] have discussed the use of the SOH of these devices for predicting the remaining lifetime and to define optimal energy management strategies.…”

Voltage equalization of an ultracapacitor module by cell grouping using number partitioning algorithm

“…In dealing with a low power charging case, a low-power, low-cost equalizing system will be the most effective solution. Typical applications are pulsed power discharge devices [6], ride through systems [13], wherein the energy can be slowly stored and where an abrupt highpower discharge is often needed.…”

“…Compared with batteries, ultracapacitor modules offer higher power densities and cycling capabilities, but lower energy densities, so they are preferred when high power discharge and/or charge is required [1][2][3][4][5][6]. Some examples of applications are energy recovery systems [1,2], buffering of energy source fluctuations [7,8], hybrid vehicles [4,9] and others.…”

Balancing circuit control for supercapacitor state estimation

“…High power applications are realised by connecting elements or cells in series to adapt to the high voltage. Hence ESS is composed by many storage elements placed in a chain structure called also a storage string or storage pack [1][2][3][4][5][6].…”