To　further　improve　the　performance　of　thermal　energy　storage　(TES)　system　with　phase　change　materials　(PCMs),　this　paper　proposed　a　novel　method,　i.e.　combining　the　additions　of　TiO2　nanoparticles,　metal　foam　and　the　provision　of　ultrasonic　field,　investigated　its　synergetic　effects　in　enhancing　conduction　and　convection　heat　transfer.　The　thermal　characteristics,　including　the　TES　time　distributions　and　the　energy　consumption　of　the　TES　system,　were　discussed　to　evaluate　the　combined　effects　of　TiO2　nanoparticles　and　ultrasonic　field　on　the　TES　rate　and　TES　efficiency.　The　results　showed　that　the　latent　TES　time　reduction　index　reached　46.50%,　when　the　TiO2　nanoparticles　concentration　was　5.0　wt%　and　the　ultrasonic　power　was　100　W,　while　the　TES　efficiency　dropped　to　10.66%.　Increasing　TiO2　nanoparticles　concentration　and　ultrasonic　power　positively　improved　the　TES　rate　due　to　conduction　heat　transfer　enhanced　by　nanoparticles　and　convection　heat　transfer　enhanced　by　the　acoustic　streaming　effect　and　the　cavitation　effect　of　the　ultrasonic　field,　but　which　negatively　reduced　the　TES　efficiency　mainly　due　to　the　energy　consumption　of　the　ultrasonic　field.　Therefore,　the　effects　of　the　ultrasonic　field　introduced　at　four　action　stages　on　the　TES　rate　and　TES　efficiency　were　compared,　and　it　confirmed　that　introducing　ultrasonic　field　at　the　latent　TES　stage　was　better　than　that　in　the　sensible　TES　stage.　Additionally,　the　proposed　novel　combined　method　needed　to　consider　the　priority　relationship　between　TES　rate　and　TES　efficiency　for　designing　the　TES　system,　favoring　the　potentials　for　further　advances　in　TES　applications.　©　2022　Elsevier　Ltd