Abun­dant sil­i­con at heart of new sys­tem to make ‘sun power’ bat­ter­ies

The Witness - Wheels - - TRENDS - LYNDA DELACEY

A TEAM of re­searchers from Madrid is de­vel­op­ing a ther­mal en­ergy stor­age sys­tem that uses molten sil­i­con to store up to 10 times more en­ergy than ex­ist­ing ther­mal stor­age op­tions.

Their sys­tem could re­place wall­mounted bat­ter­ies sev­eral car mak­ers, from Tesla Mo­tors to Mercedes-Benz and Nis­san, are rolling out to power homes and recharge elet­ric cars. Stor­age is the cur­rent ma­jor chal­lenge faced by re­new­able en­ergy sources like wind and so­lar, with bat­ter­ies not able to copy yet.

Re­searchers have been ex­plor­ing a range of new ideas to im­prove en­ergy stor­age, in­clud­ing a com­mer­cial­ized so­lar ther­mal en­ergy sys­tem that stores con­cen­trated heat from the sun in the form of molten salts and con­verts the heat back to elec­tric­ity via a ther­mal gen­er­a­tor. The salt-based sys­tems work quite well, but they re­quire com­plex pumps, pipe­lines and heat trans­fer flu­ids to gen­er­ate elec­tric­ity, mak­ing them ex­pen­sive and vul­ner­a­ble to safety is­sues.

They’re also not based on par­tic­u­larly abun­dant ma­te­ri­als — if we scale up the use of these plants, we could find ourselves run­ning low on the ele­ments needed to make these salts within a few decades. That’s why re­searchers world­wide are look­ing for safer al­ter­na­tives that use cheaper and more abun­dant ma­te­ri­als.

The sil­i­con-based so­lu­tion pro­posed by the team from the Univer­si­dad Polytech­nic de Madrid (UPM) could be a win­ner be­cause sil­i­con is one of the world’s cheap­est and most abun­dant ele­ments — sec­ond only to oxy­gen.

The pro­posed new ther­mal en­ergy stor­age sys­tem in­volves heat­ing the sil­i­con in a con­tainer us­ing ei­ther con­cen­trated sun­light on sur­plus elec­tric­ity gen­er­ated by re­new­able power. The molten sil­i­con — which can reach tem­per­a­tures of around 1 400° C — can be isolated from its en­vi­ron­ment un­til en­ergy is needed, at which point the heat is con­verted to elec­tric­ity. Sil­i­con’s unique prop­er­ties al­low it to store more than 1 MWh of en­ergy in a cu­bic me­ter — ten times more en­ergy than salts.

The key to mak­ing the new sys­tem work, ac­cord­ing to re­search leader Ale­jan­dro Datas, is the use of ther­mopho­to­voltaic cells, a fairly new tech­nol­ogy that sees so­lar pan­els gen­er­at­ing elec­tric­ity from heat as well as light.

“At such high tem­per­a­tures, sil­i­con in­tensely shines in the same way that the Sun does,” says Datas. “Thus ther­mopho­to­voltaics can be used to con­vert this in­can­des­cent ra­di­a­tion into elec­tric­ity.”

The re­searchers be­lieve their in­ven­tion could dra­mat­i­cally re­duce the cost of stor­ing and pro­duc­ing en­ergy in the ther­mal en­ergy sec­tor.

The UPM team is now look­ing to com­mer­cial­ize the sys­tem. To­wards that end, they have founded a busi­ness project called Sil­store and have started build­ing a lab­o­ra­tory-scale pro­to­type.

PHOTO: UPM

Sci­en­tists can now use sil­i­con to store and re-use the sun’s en­ergy

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