db.building_hour.aggregate({
         "$match": {
                   "_id.time": {
                            "$gte": new Date("2014-11-05 00:00:00"),
                            "$lt": new Date("2014-11-06 00:00:00")
                   }
         }
},
{
         "$group": {
                   "_id": {
                            "$hour": "$_id.time"
                   },                
                   "serials": {
                            "$push": {
                                     "buildingid":"$_id.buildingid",
                                     "value": "$value"
                            }                 
                   }                     
         }
},

最后结果