[{"_id":ObjectId("61600c11732a5d6b103ba6be"),"id":"DE","sites":[{"name":"paper_factory","energy_consumption":1000},{"name":"chair_factory","energy_consumption":2000}]},{"_id":ObjectId("61600c11732a5d6b103ba6bf"),"id":"FR","sites":[{"name":"pizza_factory","energy_consumption":3000},{"name":"foo_factory","energy_consumption":4000}]}]

db.collection.update({},[{"$addFields":{"sites":{$map:{input:"$sites",as:"s",in:{name:"$$s.name",energy_consumption:"$$s.energy_consumption",new_field:{$map:{input:"$sites",as:"value",in:"$$value.energy_consumption"}}}}}}}])