1 9 th ▁century ▁as ▁a ▁medium ▁for ▁thermal ▁storage ▁applications . ▁They ▁have ▁been ▁used ▁in ▁such ▁diverse ▁applications ▁as ▁re fr iger ated ▁transport ation ▁for ▁rail ▁and ▁road ▁applications ▁and ▁their ▁physical ▁properties ▁are , ▁therefore , ▁well ▁known . ▁ ▁Un like ▁the ▁ice ▁storage ▁system , ▁however , ▁the ▁PC M ▁systems ▁can ▁be ▁used ▁with ▁any ▁conventional ▁water ▁ch iller ▁both ▁for ▁a ▁new ▁or ▁altern atively ▁retro fit ▁application . ▁The ▁positive ▁temperature ▁phase ▁change ▁allows ▁cent rif ug al ▁and ▁absor ption ▁ch ill ers ▁as ▁well ▁as ▁the ▁conventional ▁reci proc ating ▁and ▁sc rew ▁ch iller ▁systems ▁or ▁even ▁lower ▁ambient ▁conditions ▁util izing ▁a ▁cool ing ▁tower ▁or ▁dry ▁cool er ▁for ▁charg ing ▁the ▁T ES ▁system . ▁ ▁The ▁temperature ▁range ▁offered ▁by ▁the ▁PC M ▁technology ▁provides ▁a ▁new ▁horizon ▁for ▁the ▁building ▁services ▁and ▁re fr iger ation ▁engine ers ▁regarding ▁medium ▁and ▁high ▁temperature ▁energy ▁storage ▁applications . ▁The ▁scope ▁of ▁this ▁thermal ▁energy ▁application ▁is ▁wide - r anging ▁of ▁solar ▁he ating , ▁hot ▁water , ▁he ating ▁re jection ▁( i . e ., ▁cool ing ▁tower ), ▁and ▁dry ▁cool er ▁circuit ry ▁thermal ▁energy ▁storage ▁applications . ▁ ▁Since ▁PC M s ▁transform ▁between ▁solid – liqu id ▁in ▁thermal ▁cy cling , ▁enc aps ulation ▁naturally ▁became ▁the ▁obvious ▁storage ▁choice . ▁ ▁Enc aps ulation ▁of ▁PC M s ▁Mac ro - enc aps ulation : ▁Early ▁development ▁of ▁macro