▁def or est ation ▁are ▁less ened ▁and ▁time ▁is ▁reg ained ▁by ▁people ▁sp ending ▁less ▁hours ▁gather ing ▁wood ▁for ▁open ▁fires . ▁The ▁remaining ▁off - grid ▁energy ▁that ▁does ▁not ▁power ▁the ▁fan ▁can ▁then ▁be ▁used ▁to ▁charge ▁port able ▁devices ▁through ▁a ▁USB ▁port , ▁such ▁as ▁cell ▁ph ones ▁and ▁LED ▁lights . ▁ ▁Sol ar ▁st ov es ▁▁ ▁Simple ▁solar ▁st ov es ▁use ▁the ▁following ▁basic ▁principles : ▁ ▁Con cent rating ▁sun light : ▁A ▁reflect ive ▁mirror ▁of ▁pol ished ▁glass , ▁metal ▁or ▁met all ised ▁film ▁concentr ates ▁light ▁and ▁heat ▁from ▁the ▁sun ▁on ▁a ▁small ▁cook ing ▁area , ▁making ▁the ▁energy ▁more ▁concentr ated ▁and ▁increasing ▁its ▁he ating ▁power . ▁ ▁Con ver ting ▁light ▁to ▁heat : ▁A ▁black ▁or ▁low ▁reflect ivity ▁surface ▁on ▁a ▁food ▁container ▁or ▁the ▁inside ▁of ▁a ▁solar ▁cook er ▁impro ves ▁the ▁effect iveness ▁of ▁turning ▁light ▁into ▁heat . ▁Light ▁absor ption ▁converts ▁the ▁sun ' s ▁visible ▁light ▁into ▁heat , ▁substantial ly ▁impro ving ▁the ▁effect iveness ▁of ▁the ▁cook er . ▁ ▁Tra pping ▁heat : ▁Con ve ction ▁can ▁be ▁reduced ▁by ▁isol ating ▁the ▁air ▁inside ▁the ▁cook er ▁from ▁the ▁air ▁outside ▁the ▁cook er . ▁A ▁pl astic ▁bag ▁or ▁tight ly ▁se aled ▁glass ▁cover ▁tra ps ▁the ▁hot ▁air ▁inside . ▁This ▁makes ▁it ▁possible ▁to ▁reach ▁temper atures ▁on ▁cold ▁and ▁wind y ▁days ▁similar ▁to