A　latent　heat　storage　unit　made　of　a　two-stage　phase　change　material　(PCM)　can　decrease　the　mismatch　between　supply　and　demand　of　energy.　The　cascaded　phase　change　thermal　storage　stores　and　utilizes　energy　hierarchically.　A　two-stage　cascaded　thermal　storage　unit　based　on　multichannel　flat　tubes　and　compact　fins　is　developed　in　this　study.　The　device　uses　water　as　the　heat　transfer　fluid　(HTF).　Melting/solidification　time,　charging/discharging　power,　thermal　efficiency,　and　exergy　efficiency　are　evaluated　for　different　HTF　inlet　temperatures　and　PCM　volume　flow　rates.　At　the　charging　conditions　of　70　degrees　C　and　1.5　L/min,　the　melting　time　for　paraffin　and　lauric　acid　are　21and　20　min,　respectively.　The　thermal　efficiencies　of　the　first　and　second　stages　of　the　thermal　storage　unit　are　70.62　%　and　70.40　%,　respectively,　and　the　exergy　efficiencies　are　81.25　%　and　81.19　%.　Given　the　small　pressure　loss　of　the　pump　and　the　high　heat　transfer　performance　of　the　heat　storage　system,　using　70　degrees　C　and　1.5　L/min　as　experimental　conditions　for　HTF　is　the　key　to　obtaining　short　PCM　melting　times　and　high　power.