Feature 3 | ENERGY GENERATION & STORAGE


Battery and capacitor R&D advances energy storage


A range of energy storage techniques are being studied that could have naval applications, among them new types of electrochemical capacitors and advanced batteries.


Next-generation surface ships could make use of new types of electrochemical capacitors.


and capacitor science and technology, with the unified aim of increasing the storage densities of both devices through materials-level basic and applied research. Large pulse power


E capacitors are


identified as a critical area for the US Navy. The ONR’s basic research programme concentrates on storage density at the materials level (the fundamental limitation to energy density at the device level) and dielectric breakdown mechanisms (breakdowns limit the voltage and usable storage density). Significant potential is also cited


for hybrid materials that combine the strengths of polymers and ceramics, if the benign failure feature of polymer dielectrics can be retained. Applied research includes exploiting the


18


nergy storage programmes being pursued by the US Office of Naval Research (ONR) focus on battery


benefits of both the ceramic and polymer in hybrid materials systems, addressing scale-up issues for materials identified in the basic research programme, and developing new device geometries and packaging that maximise the energy and power density. Electrochemical capacitors (ECs, also


denoted as super capacitors or ultra capacitors) are a class of energy-storage devices that exhibit characteristics related to both electrostatic capacitors and conventional batteries, the US Naval Research Laboratory explains. In terms of design and function, ECs


are most closely related to batteries in that both are based on electrochemical cells that typically incorporate liquid or gel electrolytes. Tese constituents ultimately limit their operational voltages to less than 5V, in contrast to solid-state electrostatic capacitors that can be charged to kV levels


(limited only by the breakdown strength of the incorporated dielectric material: typically a polymer or ceramic). Despite their significantly lower single-


cell voltages, ECs and batteries show a clear advantage in terms of energy density, owing to the superior charge- storage capacities of electrochemical mechanisms when compared with the energy stored in the electric field imposed across the dielectric material in an electrostatic capacitor. In the case of electrochemical charge-


storage, however, the required transport of solvent, ions and electrons – and the lower mobility of molecules and ions relative to electrons – limits the power characteristics of ECs and batteries with respect to electrostatic capacitors. ECs are commonly differentiated


from batteries in that at least one of two electrodes in an EC relies on double-


Warship Technology January 2012


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36