A　theoretical　analysis　of　novel　direct　expansion　heat　pump　system　incorporating　a　Photovoltaic/Thermal　(PV/T)　solar　collector　acting　as　the　evaporator　is　presented　in　this　paper.　Based　on　energy　balance　of　each　parts　of　the　vacuum-tube-PV　sandwich　and　the　four　main　components　of　the　heat　pump　system,　mathematical　models　are　developed　to　evaluate　the　energy　performance　of　the　heat　pump　and　the　electrical　and　thermal　performances　of　the　PV　cells,　under　the　climatic　conditions　of　the　City　of　Nottingham,　UK.　The　simulation　results　indicate　that　the　average　monthly　thermal　and　electrical　efficiencies　are　0.752　and　0.155　respectively,　and　the　average　monthly　COP　reaches　5.35　©　2011　Published　by　Elsevier　Ltd.