Su­per­ca­pac­i­tors – key to re­new­able en­ergy

DEMM Engineering & Manufacturing - - ELECTRICAL TECHNOLOGY -

Re­searchers at the Univer­sity of Can­ter­bury are in­ves­ti­gat­ing en­ergy stor­age de­vices so they can pro­vide greater re­new­able en­ergy op­tions.

Pro­fes­sor Ali­son Dow­nard and Dr Paula Brooksby have re­ceived a $739,000 Mars­den fund grant to re­search su­per­ca­pac­i­tors en­ergy stor­age de­vices.

They will lay the ground­work for en­hanced su­per­ca­pac­i­tor de­vices. Su­per­ca­pac­i­tors are used in sit­u­a­tions where bursts of en­ergy are re­quired, such as hy­brid ve­hi­cle brak­ing sys­tems and de­fib­ril­la­tors.

“Re­new­able en­ergy sources are play­ing an in­creas­ing role in meet­ing the global en­ergy de­mand,” Pro­fes­sor Dow­nard says.

“To fully ex­ploit re­new­able en­ergy sources such as wind and so­lar, ef­fi­cient and cost­ef­fec­tive en­ergy stor­age is es­sen­tial be­cause re­new­able en­ergy is not nec­es­sar­ily gen­er­ated at the place and time when we need it, so stor­age is re­quired.

“Cur­rent en­ergy stor­age ca­pa­bil­i­ties have to be im­proved to match the ad­vance in re­new­able en­ergy gen­er­a­tion. Su­per­ca­pac­i­tors can be part of the en­ergy stor­age so­lu­tion. Com­pared with bat­ter­ies, ex­ist­ing su­per­ca­pac­i­tors have low en­ergy den­sity, but they can be rapidly recharged and have long charge-recharge life­times.

“The en­ergy den­sity of a su­per-ca­pac­i­tor is di­rectly de­pen­dent on the area of its elec­trodes. The key to in­creas­ing the stor­age ca­pa­bil­ity of su­per­ca­pac­i­tors is max­imis­ing the area of elec­trodes.

“Graphene, a su­per-thin sin­gle layer of graphite, has the high­est the­o­ret­i­cal ca­pac­i­tance of any ma­te­rial and so is ideal for con­struct­ing su­per­ca­pac­i­tors.”

How­ever, the prob­lem with graphene is that the sheets clump to­gether and so most of its sur­face area is lost. The chal­lenge faced by sci­en­tists is to ar­range them in a way that max­imises the ca­pac­i­tance (elec­tri­cal charge stor­age).

“We have de­signed novel strate­gies for stack­ing care­fully spaced graphene sheets up­right on elec­trode sur­faces. We can tune the spac­ing be­tween sheets so we can max­imise the ca­pac­i­tance,” Pro­fes­sor Dow­nard says.

Their re­search will be car­ried out over the next three years and by 2017 UC will have its new $212 mil­lion Re­gional Sci­ence and In­no­va­tion Cen­tre where the chem­istry depart­ment will be based.

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